CAI info - 1/4mile, 60ft times, hp gain?
08-25-2005 | 12:48 PM
#21
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From: maryland
well i had ram air intakes (not CAIs) on all of my mild and wild Mustangs and there's always an immediate SOTP feeling right after the first testdrive. and like i said, after 1-2 weeks, you forget about it because it was so insignificant. but remember, this is an easy install and uninstall.
LT's aren't. install, ypipe, cats, sims, extensions all add up. labor is around $300-350 around here. and in most states you can't pass the visual inspection even with relocated cats (after turning off the codes with ls1edit, etc). i've paid off emission station attendents 4 times in the last 4 years or so, but it's stressful every time trying to find one. because to get 4 yes to my bribe, i got at least 5 get the **** out of here. and a guy in VA told me that he can get a reward for turning my exhaust illegal car in. and it took a longass time driving around, waiting in line for smog check to see if anyone would take a bribe.
then what about trying to sell the car later with LTs on?
again, if opening up the airbox and buying a LID is a known sucess, how is not raming more air into the same place not? does the stock MAF only want that extra breathing provided by the LID, k&n and cut airbox and not the extra air from the ram air? and how does the MAF know which extra air is from which part?
LT's aren't. install, ypipe, cats, sims, extensions all add up. labor is around $300-350 around here. and in most states you can't pass the visual inspection even with relocated cats (after turning off the codes with ls1edit, etc). i've paid off emission station attendents 4 times in the last 4 years or so, but it's stressful every time trying to find one. because to get 4 yes to my bribe, i got at least 5 get the **** out of here. and a guy in VA told me that he can get a reward for turning my exhaust illegal car in. and it took a longass time driving around, waiting in line for smog check to see if anyone would take a bribe.
then what about trying to sell the car later with LTs on?
again, if opening up the airbox and buying a LID is a known sucess, how is not raming more air into the same place not? does the stock MAF only want that extra breathing provided by the LID, k&n and cut airbox and not the extra air from the ram air? and how does the MAF know which extra air is from which part?
Last edited by mark306ci; 08-25-2005 at 01:01 PM.
08-25-2005 | 03:18 PM
#22
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I think I will install a CAI, but I wont buy one, I will fabricate my own. It should be easy to do and I can then refine it and improve what i think off the shelf ones need improvment on anyways.
thanks for eveyone info. I will post pics of the one I make!!!
then I can put the $150 to other mods...
thanks for eveyone info. I will post pics of the one I make!!!
then I can put the $150 to other mods...
08-25-2005 | 10:51 PM
#23
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From: maryland
hey good luck with this one dude. i made 2 for 2 fox mustangs out of Home Depot clothes dryer ducting, duct tape and a gutter spout (mimicking a March Ram Air kit). cost like $15 instead of $149. looked like ****. didn't seal all that well. and looked like i had a gutter spout sticking out from under my car (because i did). i tried it for my LS1 but not enough room between the a/c condenser and the front part of the car.
08-26-2005 | 11:13 AM
#24
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From: England
Originally Posted by ibanez7
so does anyone else have info, as far as timesheets or hp gains from a CAI??
Air intake is massive area and heavily debated.
If I'm understanding you correctly you want to know when/where/and how much difference a CAI makes.
If we start with stock. Basically air is sucked in via th eengine thru the air intake -> filter -> TB -> Intake manifold. At light or moderate throttle the system will be able to provide enough intake air. However at WOT (wide open throttle) there is a restriction, the intake setup can no longer provide enough air for the engine.
A lid removes most of this restriction and frees up power at WOT conditions. This is rpm based not speed based. So 1200rpm@ 70mph will require less air intake than 5500rpm @ 40mph. The stock paper filter will flow enough air for about 500bhp n/a, sodon't worry about changing it for an aftermarket one.
Cold air has a creater charge density thus producing more power. So 'cool air ducts' may be benifical. But in many modern cars the stock location is actually pretty good. Any where in front of the radiator will be fine, and even in the engine bay tempertures are not always that bad, sure while stationary the engine will heat soke, but at speed the air flow and exchange of the radiator will bring the temperatures down to a bit hotter than ambiant in most cases. The downside to cool air ducts is reduced flow of the radiator and if by a scoop then increased drag.
Without FI (forced induction - turbo/supercharger) it is very hard to force more air into an engine. Many beleive that a scoop or funnel will force more air into an engine, in many cases they will actually be forcing less air into the engine due to physics.
At sub-sonic speeds air pressure is increased by slowing the air velocity, this is done by a widening of the air intake passage. Many compition cars/bikes will have an air intake (maybe a scoop) leading into a large air box. As the air enters the airbox it will increase in pressure, thus allowing a slightly creater chare densisty into the engine. If you can match the air box with the engine and desired powerband you can also induce 'harmonic balance'. Which will aid airflow into the engine. These basic prinicples are the back bone of 'Ram Air'.
Ram Air, is no mith and does work, but not how the marketing people will have you beleive. In 99.99% of automotive cases Ram Air does not take place and is mearly a scoop on the front of a car.
However forcing air into an engine is a lot harder. It has been tested and proven (mainly by the aviation industry) that you need to be traverling at about 150mph before you'll see any benefit. At 200mph the gain will beusable but not until you reach 350mph will there be a significant gain in engine output. The only production car I know of that has an operational Ram Air system is the Bristol Fighter (a very expensive/exclusive British car, using a variation of the Viper V10), however it needs to reach 200mph to see any gain.
Air box resonance is the key to a good intake system, a scoop facing into the air flow will often yeild little or nothing. And in many cases will be an indirect gain caused by other means.
Have fun designing your own setup.
08-26-2005 | 12:22 PM
#25
Informative post 300, I have nothing to add to that.
I think one reason everyone sees varying results from intake modifications is due to MAF calibration. Its calibrated for the original stock configuration, once that changes the MAF is really no longer accurate and needs recalibration to correspond to the intake airflow changes.
I think one reason everyone sees varying results from intake modifications is due to MAF calibration. Its calibrated for the original stock configuration, once that changes the MAF is really no longer accurate and needs recalibration to correspond to the intake airflow changes.
08-26-2005 | 01:07 PM
#26
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i agree with your long written post, and thank you for your thoughts.
I feel that these CAI kits are exactly that, just a cold air intake instead of warm engine air. They are definitely not much of a force feed.
I feel that these CAI kits are exactly that, just a cold air intake instead of warm engine air. They are definitely not much of a force feed.
09-02-2005 | 04:25 AM
#27
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From: maryland
Originally Posted by 300bhp/ton
The only production car I know of that has an operational Ram Air system is the Bristol Fighter (a very expensive/exclusive British car, using a variation of the Viper V10), however it needs to reach 200mph to see any gain.
why do highend exotic cars with rear mounted engines usually have some kind of ram air ducting that draws air from the roof and such? it's always pointed in the direction of oncoming air and not in any other direction.
09-02-2005 | 09:54 AM
#28
Originally Posted by mark306ci
well i had ram air intakes (not CAIs) on all of my mild and wild Mustangs and there's always an immediate SOTP feeling right after the first testdrive. and like i said, after 1-2 weeks, you forget about it because it was so insignificant. but remember, this is an easy install and uninstall.
LT's aren't. install, ypipe, cats, sims, extensions all add up. labor is around $300-350 around here. and in most states you can't pass the visual inspection even with relocated cats (after turning off the codes with ls1edit, etc). i've paid off emission station attendents 4 times in the last 4 years or so, but it's stressful every time trying to find one. because to get 4 yes to my bribe, i got at least 5 get the **** out of here. and a guy in VA told me that he can get a reward for turning my exhaust illegal car in. and it took a longass time driving around, waiting in line for smog check to see if anyone would take a bribe.
then what about trying to sell the car later with LTs on?
again, if opening up the airbox and buying a LID is a known sucess, how is not raming more air into the same place not? does the stock MAF only want that extra breathing provided by the LID, k&n and cut airbox and not the extra air from the ram air? and how does the MAF know which extra air is from which part?
LT's aren't. install, ypipe, cats, sims, extensions all add up. labor is around $300-350 around here. and in most states you can't pass the visual inspection even with relocated cats (after turning off the codes with ls1edit, etc). i've paid off emission station attendents 4 times in the last 4 years or so, but it's stressful every time trying to find one. because to get 4 yes to my bribe, i got at least 5 get the **** out of here. and a guy in VA told me that he can get a reward for turning my exhaust illegal car in. and it took a longass time driving around, waiting in line for smog check to see if anyone would take a bribe.
then what about trying to sell the car later with LTs on?
again, if opening up the airbox and buying a LID is a known sucess, how is not raming more air into the same place not? does the stock MAF only want that extra breathing provided by the LID, k&n and cut airbox and not the extra air from the ram air? and how does the MAF know which extra air is from which part?
and you just said yourself "you forget about it because it was so insignificant." now if you make it yourself, good and more power to you. but if you payed $200 or more for something "insignificant", then yikes.
Originally Posted by mark306ci
i find this hard to believe that at speeds up to 199 mph, there is absolutely no gain whatsover . and then at 200mph, all of the sudden, the car gains power. c'mon. do you have any actual data to back this up?
why do highend exotic cars with rear mounted engines usually have some kind of ram air ducting that draws air from the roof and such? it's always pointed in the direction of oncoming air and not in any other direction.
why do highend exotic cars with rear mounted engines usually have some kind of ram air ducting that draws air from the roof and such? it's always pointed in the direction of oncoming air and not in any other direction.
09-02-2005 | 04:08 PM
#29
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From: maryland
Originally Posted by luvmeZ28
who cares about easy to install/uninstall? and FYI, the header install isnt nearly as hard as these shops that charge 300+ would want you to believe.
and if you think you would sell the car, then dont waste your time modding it at all. if i wasnt going to keep mine, i wouldnt bother with anything.
i dont really understand why people do any of the "little things" like lid, smooth bellow, ssra, maf, !egr, when thats all they are going to do and you will see very little gains. i dunno, i just wont be happy if all i can say is "my car runs .2 faster than stock."
and how much does LT alone gain? about .20 faster. lmao.
and the combined cost of those little mods (minus the MAF,
), the cost is less than doing LTs parts & labor.
and you just said yourself "you forget about it because it was so insignificant." now if you make it yourself, good and more power to you. but if you payed $200 or more for something "insignificant", then yikes.
i have actually heard bits and pieces of his argument before, but i would love to read a full explanation. linky please
09-02-2005 | 04:26 PM
#30
Originally Posted by mark306ci
well i do and i don't feel like changing my own headers.
good for you if you plan on keeping a car for 20 years. and i have a convertible and i don't like the extra noise of LTs. not everybody lives in non-emission required states. it's a pain looking for places to bribe every 2 years. and the stink that LTs gives out have been known to attract cops. it's so obvious whenever i'm behind someone who've removed their cats.
same can be said about going to LTs instead of an STS turbo kit that's easier to install, remain emission legal, and make 5-6 times more power.
and how much does LT alone gain? about .20 faster. lmao.
and the combined cost of those little mods (minus the MAF,), the cost is less than doing LTs parts & labor.
i want to see you make a ram air that fits in that little flat space where the SSRA slips through and seal as well while keeping A/C. if you spend $50 and a crap load of time making a POS homemade ramair kit that doesn't perform as well, then i don't consider that time well spent.
link on what? that some rear mounted exotic cars have ramair ducting on the roof to draw air? you can see it by looking at the pictures.
good for you if you plan on keeping a car for 20 years. and i have a convertible and i don't like the extra noise of LTs. not everybody lives in non-emission required states. it's a pain looking for places to bribe every 2 years. and the stink that LTs gives out have been known to attract cops. it's so obvious whenever i'm behind someone who've removed their cats.
same can be said about going to LTs instead of an STS turbo kit that's easier to install, remain emission legal, and make 5-6 times more power.
and how much does LT alone gain? about .20 faster. lmao.
and the combined cost of those little mods (minus the MAF,
), the cost is less than doing LTs parts & labor.i want to see you make a ram air that fits in that little flat space where the SSRA slips through and seal as well while keeping A/C. if you spend $50 and a crap load of time making a POS homemade ramair kit that doesn't perform as well, then i don't consider that time well spent.
link on what? that some rear mounted exotic cars have ramair ducting on the roof to draw air? you can see it by looking at the pictures.
and yes, i will have this car for a long time. it wont be the only car i own, just my favorite toy.
and choosing an STS over LTs is a great choice, you actually get some power for the money you spend, unlike the piddy overpriced mods like CAI.
and it was a guestimate that all the piddly mods might give you .2. i doubt they do. ive seen headers net .4-.5, plus you gotta love the gains on the dyno, not to mention the improved sound. so worth it in my opinion, maybe not if you dont do the work yourself, but i wont ever know the answer to that one.
and i dont ever configure the costs of labor into anything, because im not going to pay people to do things for me(except gear install). so that puts those little parts all together in the same price range(more with maf
) as LTs, and thats just laughable. youre basically paying so you can say you have them. and you, yourself used the word that best fits. "insignificant"and there is actually a guy on here that made his own CAI, and it fit well and looked good. i dont even think it cost him $50 and i know he didnt spend a whole lot of time on it. i wish i could find that thread.
and about the link, i was talking to the other guy in this thread that you are so adamently disagreeing with. about the air flow.
you seem to be getting a little flustered over this.
and the fact that you are trying to compare gains of SSRA or whatever, to LTs is
no hard feelings.
09-02-2005 | 06:53 PM
#31
Originally Posted by ibanez7
i hope it does work for $130-$200 mod..
I might juts make my own CAI. Its woudnt be hard to do...
I might juts make my own CAI. Its woudnt be hard to do...
yeah man i made one. 17.00 from home depot
i got (3) sheets of sheetmetal @ 5.50 a piece 3' or 4'x 16 inches wide
youll need some small screws, like maybe 1/2" self tappers work great
tin snips something good to bend metal with (a handbrake or just a good vise) and some patience
itll go in between your air dam and a/c condenser thing. lift up you air filter, take out of box, then cut the plastic shroud thats there, go to www.fasttoys.net to see some pics of it it helped me a lil.
then start measuring stuff up. the top has like a 16x 1 inch opening
the bottom is a 16x 3 inch opening
i cant remember exact lengths
and youll have to take out at least 2 bolts
that are in that forked metal piece .. go to www.fasttoys.net to look at picture. its not real hard to do. you just need patience and YOU WILL FEEL A DIFFERENCE i did a bunch of free mods which definately helped if u need to know any free mods, go head' and ask me about em. all i know is that i pulls harder than before def. noticeable!!
Last edited by 98TADRIVER; 09-02-2005 at 06:59 PM.
09-07-2005 | 09:49 PM
#32
This thread is funny. I just ordered a FTRA, it's currently on backorder and I can't wait until it arrives. It wasn't over 200 dollars either and I actually got a discount because it's backordered. It's also their new and improved one, slightly changed to add an even greater ram-air effect. I don't see how anyone can think ram-air is a myth and you need to be going 150+ to experience it because there is an increase in air pressure at even low speeds. There is a good article in GMHTP June 2005 called introduction to induction and it explains everything from CAI's, stock setups, aftermarket and homemade ram-air rigs and even filters. Bottom line is that any CAI or Ram-Air setup is going to give a gain because;
1. There's no way that your engine can't inhale more air when the environment in front of the throttle body is pressurized.
2. There's a duct which quickly and effeciently directs ambient air (which we all know is cooler and more oxygen rich) into the throttle body.
The "Ram-Air" hood that was so greatly marketed on WS6's and is still on other cars today is crap. The opening is small, restrictive, and indirect. While may give a little gain, it is not optimum. From what I know about Ram-Air from reading that article the FTRA is the best looking setup out there. It is clearly better than the WS6 Ram-Air and seems to utilize the underhood space to the best of its ability to create a true ram-air effect while not looking ghetto. Maybe one of these FTRA's is too much money for too little gain for you and you want other mods and that makes sense to me. I'm just getting all the support mods done before I go into headers and cams and **** because I know that the intake, exhaust, and engine all work as a system feeding off of each other. So later, when I do get headers, cam and nitrous, I'll experience a bigger gain from them because my car is breathing better.
And one other thing, supposedly a FTRA or SSRA will pay for itself in no time considering the +MPG you get, and with gas the way it is now, you can't afford to go wrong.
1. There's no way that your engine can't inhale more air when the environment in front of the throttle body is pressurized.
2. There's a duct which quickly and effeciently directs ambient air (which we all know is cooler and more oxygen rich) into the throttle body.
The "Ram-Air" hood that was so greatly marketed on WS6's and is still on other cars today is crap. The opening is small, restrictive, and indirect. While may give a little gain, it is not optimum. From what I know about Ram-Air from reading that article the FTRA is the best looking setup out there. It is clearly better than the WS6 Ram-Air and seems to utilize the underhood space to the best of its ability to create a true ram-air effect while not looking ghetto. Maybe one of these FTRA's is too much money for too little gain for you and you want other mods and that makes sense to me. I'm just getting all the support mods done before I go into headers and cams and **** because I know that the intake, exhaust, and engine all work as a system feeding off of each other. So later, when I do get headers, cam and nitrous, I'll experience a bigger gain from them because my car is breathing better.
And one other thing, supposedly a FTRA or SSRA will pay for itself in no time considering the +MPG you get, and with gas the way it is now, you can't afford to go wrong.
09-08-2005 | 01:59 AM
#33
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From: maryland
Originally Posted by luvmeZ28
you seem to be getting a little flustered over this.
and the fact that you are trying to compare gains of SSRA or whatever, to LTs is
no hard feelings.
and the fact that you are trying to compare gains of SSRA or whatever, to LTs is
no hard feelings.
you said that all of the little mods such as SSRA, FRA, lid, filter, elbow, etc. would gain about .20 and not worth it ....
my response was that .20 is about what LTs give you. maybe .30 but being a lot easier and cheaper to buy & install vs. LTs.
09-08-2005 | 02:02 AM
#34
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From: maryland
Originally Posted by luvmeZ28
and it was a guestimate that all the piddly mods might give you .2. i doubt they do. ive seen headers net .4-.5,
so if you put LTs on a completely stock LS1, you're not gaining .4-.5
how much more RWHP do LTs give with no tuning? 18-22 rwhp? you're not cutting .4-.5 off of your ET with this little HP.
09-08-2005 | 07:11 AM
#35
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From: England
Answer Part 1
Originally Posted by mark306ci
i find this hard to believe that at speeds up to 199 mph, there is absolutely no gain whatsover . and then at 200mph, all of the sudden, the car gains power.
In all reality a lot of this is still probably a marketing ploy. But considering Bristol do not advertise and even refuse to sell cars to people that they think will harm the image of the brand it seems logical to assume that there is much truth behind the whispers.
Originally Posted by mark306ci
why do highend exotic cars with rear mounted engines usually have some kind of ram air ducting that draws air from the roof and such? it's always pointed in the direction of oncoming air and not in any other direction.
Many mid engined cars do have side mounted scoups (including the Porsche 911). Now these can be mistaken for many things.
1. They could be and are regular air ducts for radiator cooling
2. Brake cooling ducts
3. A regular duct for an air intake
Now a duct is mearly designed to change the direction of air flow rather than increase the air pressure.
If you think about it, most cars have a duct or scoop that draws air. It's commonly know as a radiator grill. However behind that grill you may also find a oil cooler, transmission cool, intercooler, and an air intake. Sometimes these will be located infront or behind the radiator. Take this V12 Jaguar engine, the air boxes (one for each bank) are forward facing. Although they are behind the radiator this will have little affect on the actual air flow. So in many ways they could be construed as Ram Air intake, because they have an opening into the air flow. If these same air boxes where located infront of tha radiator or thru holes in the bonnet they would still function exactly the same (although the intake air would likely be a lower temperature, but this is a different issue all together)
However of course the Jagur V12 does not have Ram Air nor is it advertised too have.
On a mid engined car (unless the radiator or intercooler are located at the front) the scoops are mearly relocated radiator grills. In addition these ducts also help promote air circulation around the engine. (a problem that the 1st Lotus Esprit had, basically no air circulation due to being mid engined, thus they suffered over heating problems. The S2 variant gained side scoops mearly to help disipate heat from the engine bay by promoting air circulation).
In other instances, these side scoops will often be slightly lower or indented from the bodywork, often with a long track leading to it. Although not exactly they are a form of NACA duct, where they scavenge low pressure air from within the boundary layer. The reason is they allow an intake duct to be present while resulting in minimum drag.
See the side scoop on this Ferrari F360, it is preceeded buy a long depression, thus the scoop does not protrude into the air flow. Most 'exoctics' use similar methods
This is a NACA duct:
For more info on aerodynamics I'll refer you to this thread: https://ls1tech.com/forums/road-racing/370922-aerodynamics-explanation.html
09-08-2005 | 07:13 AM
#36
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From: England
Answer Part 2 Here is some general information about Ram Air that I have found across the internet. All from reliable resources. In additon the physics have been backed up and proven, so its not just hear say or opinions. Remeber the world of physics is very large and diverse, and not always obvious to the causual enthusiast.
I hope this has answered some of your questions.
Originally Posted by various resources from the web
Marketers just can't resist it. Ram air! The words themselves summon up images of rushing wild beasts, or of secret military aircraft operating on futuristic principles.
Unfortunately, on most perofrmance cars, ram-air is as functional as tail fins were on cars of the ’60s.
What is it? Ram air just means using a forward-facing air intake to gain some extra intake pressure. We have all, as children, felt the pressure of moving air on our hands when we held them out the window of the family car. When moving air is brought smoothly to rest, the energy of its motion is converted into pressure. Motorcycles went through a "ram-air" period in the early 1990s, during which street bikes were equipped with the forward-facing "rocket-launcher" engine air intakes seen on many road-racing machines.
While it's appealing to imagine the forward velocity of a car being converted into free supercharge, the actual air pressure gain is extremely small at normal speeds. For example, at 150 mph, the pressure gain when air is efficiently brought to rest is 2.75 percent. Because this is a dynamic effect, it is proportional to the square of the air velocity. At a more realizable automobile speed of 75 mph, the effect (again with 100 percent efficient conversion of velocity into pressure) will be only one-quarter as great — that is, just under seven-tenths of one percent.
In fact, velocity energy is not converted into pressure at 100 percent efficiency. A figure of 75 percent efficiency is usual, which reduces our notional ram-air gain at 75 mph to one-half of one percent.
Therefore, at normal speeds, ram air is a myth. However, something much more interesting lies behind it, ignored by the advertiser's busy pen. That something is airbox resonance.
In order to implement ram air, the carburetors or throttle-bodies of our engine must seal to an airbox whose volume is large enough that the intake cycle of one cylinder cannot pull its internal pressure down significantly. Box volume is typically 10-20 times the engine's displacement. Then the forward-facing air intake is connected to the box. When this assembly is tested on the dyno — even without an external fan to simulate the high-speed rush of air past the intake — it is discovered that the engine's torque curve is greatly altered, with new peaks and hollows.
Why? The answer is airbox resonance. If you hold the mouth of an empty bottle near your open mouth as you loudly hum scales, you find that at certain “hum frequencies” the bottle reinforces your humming, which becomes louder. What is happening is that the springy compressibility of the air in the bottle is bouncing the slug of air in the bottle's neck back and forth at a particular frequency — higher if the bottle is small, lower if it is larger. Your humming is driving a rapid plus-and-minus variation of the air pressure inside the bottle.
The same thing happens inside a resonant airbox. The volume of air in the box is the “spring” in this kind of oscillator. The mass of air in the box's intake pipe is what oscillates. The “humming” that drives the oscillation is the rapid succession of suction pulses at the carb or throttle-body intakes. If the volume of the airbox and the dimensions of the intake pipe(s) are correctly chosen, the airbox can be made to resonate very strongly, in step with the engine's suction pulses. The result, when this is done correctly, is that the engine takes air from the box only during the high-pressure part of its cycle, while the box refills from atmosphere through its intake between engine suction pulses. This produces a useful gain in torque.
Using this idea, motorcycle engines have been able to realize torque increases, in particular speed ranges, of 10-15 percent. In race engines, it is usual to tune the airbox to resonate at peak-power rpm to increase top speed. For production engines, it is often more useful to tune the box resonance to fill in what would otherwise be a flat-spot in the torque curve, resulting in smoother power and improved acceleration.
Early resonant airbox systems used long intake pipes that terminated in forward-facing intakes. More recent designs do not connect the ram-air pipe to the box at all, but terminate it near the airbox entry. The actual entry pipe is a short piece of tubing with bellmouths on both ends. This is done because (a) the potential gain from actual ram air is too small to worry about, and (b) it's easier to tune the airbox with a short tube.
Where vehicle speeds are very high, gains from ram air are significant. This was discovered by Rolls-Royce in the late 1920s as the company developed its R Schneider Trophy air racing engine. At speeds above 300 mph, it was noticed that the R’s fuel mixture leaned out enough to cause backfiring. When the mixture was corrected for ram-air pressure gain, the engineers realized they had a "free" source of power. At 350 mph the gain from ram air is almost 15 percent. Similar mixture correction is necessary when ram air is used on drag-race and Bonneville cars and bikes.
Intuition suggests that a forward-facing intake made in the form of a funnel, large end foremost, should somehow multiply the pressure of the air, resulting in a much larger pressure gain at the small end. Sadly, intuition is wrong. In order to convert velocity energy into pressure, the air has to be slowed down, and this requires a duct that widens rather than narrows. Next time you fly on a commercial airliner, note that its engine intakes widen as the airflow approaches the compressor face. Such widening passages are called diffusers, and they are universally used in the conversion of velocity into pressure.
Language often plays tricks on us — especially when language is used by product advertisers. "Ram air" sounds much more appealing than "resonant airbox." Nevertheless, it is airbox resonance that actually generates a significant power gain.
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Cliffnotes:
-Ram Air a myth? = NO
-Does it work on a road car = NO
-At 150mhp there is next to no gain.
-Significant gains arn't seen until 300mph+
-The air box is the key, not the ducting.
-When buying a CAI/induction kit look for the one that uses air box resonance
Edit: Additional Reading
Intake temperature is a whole different ball game.
The simple rule is:
'Cool for power (maximum charge density), hot for economy (minimum charge density to reduce losses due to throttling).'
Although in many cars the under bonnent temperatures are no where near as bad as many people beleive. This refers to a 5.3 liter Jguar XJS V12. So a big engine in a small engine bay.
The under-bonnet air temperature at idle can easily get up around 70 C but the faster the car goes the lower the air temperature falls - simply because the radiator is passing its heat to a much larger quantity of air per second - so at 80 mph. the engine is breathing air at around 45 C. That's still a bit higher than the ideal but not nearly so bad as many people think. Obviously the standard arrangement helps to maximise economy in moderate speed urban cruise without compromising top end power too much.
In setups that duct cool air from outside. The power gains from such a system are almost certainly attributed to the filter, and less restritive intake (meaning quite simply a bigger opening), and a form of air box resonance coupled with a 'cool air intake' from outside the engine bay. Sadly even at very high speeds (well over 100mph) I doubt that it has any form of 'Ram Air' effect. If you reconfigured the system to take air from the inside of a wheel arch it would produce the same results as having the intake ducts at the front of the car. The source of the air, not the location of the ducts is the important factor.
Remember the only way to get a greater volume of air into the engine is to compress it. This is what turbo and superchargers do. An air intake scoop either on the front of a car or on the bonnet will not compress the air at any speed most people are likely to travel at.
Taking the airbox resonance theory futher with the intake manifold itself by optimising the length and entry profile into each of the tracts to better exploit induced harmonic resonances in the air as it flows towards the cylinder. Any tube containing air can be made to resonate at certain critical frequencies in the manner of an organ pipe. Such is the case with the inlet tracts of an engine and if the natural resonance frequencies can be matched to the engine speed then a mild supercharging effect can be induced. Get it wrong and the reverse will apply, resulting in a loss of performance.
Unfortunately, on most perofrmance cars, ram-air is as functional as tail fins were on cars of the ’60s.
What is it? Ram air just means using a forward-facing air intake to gain some extra intake pressure. We have all, as children, felt the pressure of moving air on our hands when we held them out the window of the family car. When moving air is brought smoothly to rest, the energy of its motion is converted into pressure. Motorcycles went through a "ram-air" period in the early 1990s, during which street bikes were equipped with the forward-facing "rocket-launcher" engine air intakes seen on many road-racing machines.
While it's appealing to imagine the forward velocity of a car being converted into free supercharge, the actual air pressure gain is extremely small at normal speeds. For example, at 150 mph, the pressure gain when air is efficiently brought to rest is 2.75 percent. Because this is a dynamic effect, it is proportional to the square of the air velocity. At a more realizable automobile speed of 75 mph, the effect (again with 100 percent efficient conversion of velocity into pressure) will be only one-quarter as great — that is, just under seven-tenths of one percent.
In fact, velocity energy is not converted into pressure at 100 percent efficiency. A figure of 75 percent efficiency is usual, which reduces our notional ram-air gain at 75 mph to one-half of one percent.
Therefore, at normal speeds, ram air is a myth. However, something much more interesting lies behind it, ignored by the advertiser's busy pen. That something is airbox resonance.
In order to implement ram air, the carburetors or throttle-bodies of our engine must seal to an airbox whose volume is large enough that the intake cycle of one cylinder cannot pull its internal pressure down significantly. Box volume is typically 10-20 times the engine's displacement. Then the forward-facing air intake is connected to the box. When this assembly is tested on the dyno — even without an external fan to simulate the high-speed rush of air past the intake — it is discovered that the engine's torque curve is greatly altered, with new peaks and hollows.
Why? The answer is airbox resonance. If you hold the mouth of an empty bottle near your open mouth as you loudly hum scales, you find that at certain “hum frequencies” the bottle reinforces your humming, which becomes louder. What is happening is that the springy compressibility of the air in the bottle is bouncing the slug of air in the bottle's neck back and forth at a particular frequency — higher if the bottle is small, lower if it is larger. Your humming is driving a rapid plus-and-minus variation of the air pressure inside the bottle.
The same thing happens inside a resonant airbox. The volume of air in the box is the “spring” in this kind of oscillator. The mass of air in the box's intake pipe is what oscillates. The “humming” that drives the oscillation is the rapid succession of suction pulses at the carb or throttle-body intakes. If the volume of the airbox and the dimensions of the intake pipe(s) are correctly chosen, the airbox can be made to resonate very strongly, in step with the engine's suction pulses. The result, when this is done correctly, is that the engine takes air from the box only during the high-pressure part of its cycle, while the box refills from atmosphere through its intake between engine suction pulses. This produces a useful gain in torque.
Using this idea, motorcycle engines have been able to realize torque increases, in particular speed ranges, of 10-15 percent. In race engines, it is usual to tune the airbox to resonate at peak-power rpm to increase top speed. For production engines, it is often more useful to tune the box resonance to fill in what would otherwise be a flat-spot in the torque curve, resulting in smoother power and improved acceleration.
Early resonant airbox systems used long intake pipes that terminated in forward-facing intakes. More recent designs do not connect the ram-air pipe to the box at all, but terminate it near the airbox entry. The actual entry pipe is a short piece of tubing with bellmouths on both ends. This is done because (a) the potential gain from actual ram air is too small to worry about, and (b) it's easier to tune the airbox with a short tube.
Where vehicle speeds are very high, gains from ram air are significant. This was discovered by Rolls-Royce in the late 1920s as the company developed its R Schneider Trophy air racing engine. At speeds above 300 mph, it was noticed that the R’s fuel mixture leaned out enough to cause backfiring. When the mixture was corrected for ram-air pressure gain, the engineers realized they had a "free" source of power. At 350 mph the gain from ram air is almost 15 percent. Similar mixture correction is necessary when ram air is used on drag-race and Bonneville cars and bikes.
Intuition suggests that a forward-facing intake made in the form of a funnel, large end foremost, should somehow multiply the pressure of the air, resulting in a much larger pressure gain at the small end. Sadly, intuition is wrong. In order to convert velocity energy into pressure, the air has to be slowed down, and this requires a duct that widens rather than narrows. Next time you fly on a commercial airliner, note that its engine intakes widen as the airflow approaches the compressor face. Such widening passages are called diffusers, and they are universally used in the conversion of velocity into pressure.
Language often plays tricks on us — especially when language is used by product advertisers. "Ram air" sounds much more appealing than "resonant airbox." Nevertheless, it is airbox resonance that actually generates a significant power gain.
------------------------------------------------------------------
Cliffnotes:
-Ram Air a myth? = NO
-Does it work on a road car = NO
-At 150mhp there is next to no gain.
-Significant gains arn't seen until 300mph+
-The air box is the key, not the ducting.
-When buying a CAI/induction kit look for the one that uses air box resonance
Edit: Additional Reading
Intake temperature is a whole different ball game.
The simple rule is:
'Cool for power (maximum charge density), hot for economy (minimum charge density to reduce losses due to throttling).'
Although in many cars the under bonnent temperatures are no where near as bad as many people beleive. This refers to a 5.3 liter Jguar XJS V12. So a big engine in a small engine bay.
The under-bonnet air temperature at idle can easily get up around 70 C but the faster the car goes the lower the air temperature falls - simply because the radiator is passing its heat to a much larger quantity of air per second - so at 80 mph. the engine is breathing air at around 45 C. That's still a bit higher than the ideal but not nearly so bad as many people think. Obviously the standard arrangement helps to maximise economy in moderate speed urban cruise without compromising top end power too much.
In setups that duct cool air from outside. The power gains from such a system are almost certainly attributed to the filter, and less restritive intake (meaning quite simply a bigger opening), and a form of air box resonance coupled with a 'cool air intake' from outside the engine bay. Sadly even at very high speeds (well over 100mph) I doubt that it has any form of 'Ram Air' effect. If you reconfigured the system to take air from the inside of a wheel arch it would produce the same results as having the intake ducts at the front of the car. The source of the air, not the location of the ducts is the important factor.
Remember the only way to get a greater volume of air into the engine is to compress it. This is what turbo and superchargers do. An air intake scoop either on the front of a car or on the bonnet will not compress the air at any speed most people are likely to travel at.
Taking the airbox resonance theory futher with the intake manifold itself by optimising the length and entry profile into each of the tracts to better exploit induced harmonic resonances in the air as it flows towards the cylinder. Any tube containing air can be made to resonate at certain critical frequencies in the manner of an organ pipe. Such is the case with the inlet tracts of an engine and if the natural resonance frequencies can be matched to the engine speed then a mild supercharging effect can be induced. Get it wrong and the reverse will apply, resulting in a loss of performance.
09-08-2005 | 03:05 PM
#37
Originally Posted by mark306ci
just arguing the point that this thing does work and easy to install. and i was not comparing the gains of LTs with SSRA only.
you said that all of the little mods such as SSRA, FRA, lid, filter, elbow, etc. would gain about .20 and not worth it ....
my response was that .20 is about what LTs give you. maybe .30 but being a lot easier and cheaper to buy & install vs. LTs.
you said that all of the little mods such as SSRA, FRA, lid, filter, elbow, etc. would gain about .20 and not worth it ....
my response was that .20 is about what LTs give you. maybe .30 but being a lot easier and cheaper to buy & install vs. LTs.
Originally Posted by mark306ci
there's no way that you're gaining that much with LTs and nothing else. remember, you said that doing little things such as FRA, filter, lid, etc... is "piddly".
so if you put LTs on a completely stock LS1, you're not gaining .4-.5
how much more RWHP do LTs give with no tuning? 18-22 rwhp? you're not cutting .4-.5 off of your ET with this little HP.
so if you put LTs on a completely stock LS1, you're not gaining .4-.5
how much more RWHP do LTs give with no tuning? 18-22 rwhp? you're not cutting .4-.5 off of your ET with this little HP.
09-08-2005 | 05:06 PM
#38
They are not worth it. You will gain very little for what you are paying for it. I personally did not gain anything from my SSRA, but others have gained the most of .05 tenth in the 1/4. I have one for sale if anybody wants one thoa.
09-08-2005 | 10:00 PM
#39
Originally Posted by saclay
They are not worth it. You will gain very little for what you are paying for it. I personally did not gain anything from my SSRA, but others have gained the most of .05 tenth in the 1/4. I have one for sale if anybody wants one thoa.
09-08-2005 | 11:15 PM
#40
TECH Enthusiast
Joined: Apr 2004
Posts: 749
Likes: 0
From: Chandler, Arizona
I'll put in my 2 cents. Ram air is never a bad thing, but cold air makes a much bigger difference, at least at speeds below 100 mph.
Assume you get the full ram effect at 100 mph, the air pressure will increase by what is called the stagnation pressure or by 1/2 Rho V squared, where Rho is the air density and V is the velocity. At 100 mph, the stagnation pressure is .174 psi. This will add around 3.4 hp (assumes horsepower is linear to inlet density). However, if you lower the inlet temperature from 100F to just 90F, this increases the air density by a ratio of the absolute temps and would increase horsepower by 5.5 hp.
Now that being said, I don't run a cold air induction because I think the factory airbox already pulls from a cold area in the nose of the car. I could increase my power at 100 mph by 3.4 hp, but given that it goes up by the velocity squared, you really don't get much benefit until the end of your 1/4 mile run. I'm just going to stick to the stock setup with my SLP lid. I did however raise the airbox and sealed off the back of it to get more flow area into the airbox. I sealed the back portion just to keep the hot air from coming in from the radiator.
Assume you get the full ram effect at 100 mph, the air pressure will increase by what is called the stagnation pressure or by 1/2 Rho V squared, where Rho is the air density and V is the velocity. At 100 mph, the stagnation pressure is .174 psi. This will add around 3.4 hp (assumes horsepower is linear to inlet density). However, if you lower the inlet temperature from 100F to just 90F, this increases the air density by a ratio of the absolute temps and would increase horsepower by 5.5 hp.
Now that being said, I don't run a cold air induction because I think the factory airbox already pulls from a cold area in the nose of the car. I could increase my power at 100 mph by 3.4 hp, but given that it goes up by the velocity squared, you really don't get much benefit until the end of your 1/4 mile run. I'm just going to stick to the stock setup with my SLP lid. I did however raise the airbox and sealed off the back of it to get more flow area into the airbox. I sealed the back portion just to keep the hot air from coming in from the radiator.