300bhp/ton

Did I say that? I don't think so.

To get more power (more air) a higher lift cam opens the valves further and for longer. Opening them further requires more effort and heavy duty springs to keep it all in check.And opening them longer can result in running, emissions and mpg issues further down the line.

Bigger valves will of course allow more air flow. But two 1" valves has less curtain area than four 1/2" valves. This is MULTIVALVE technology.

Which is generally found on DOHC motors not OHV's.

Did you turn over two pages or what.

I'll make it easy - What the **** are you talking about??? I have no idea.

You said is DOHC like a cam swap? The answer I have given is no.

I NEVER mentioned a cam doesn't give power, so throw your toys back into the pram.




Then you live in a stupidly tiny world with a very narrow perspective.

Ok HONDA is from JAPAN which is NOT in EUROPE

And bhp/litre is the same the world over, the laws of PHYSICS don't change from country to country

Tell me, what would you rather have. A 5.7 litre V8 with the ability to only run 80bhp/litre or a 5.7 litre V8 with the abilty to run 110bhp/litre?

It's mentioned by ENGINEERS, who cares what magazine does or doesn't.

It's still the same thing.

How come a LS6 engine produces more power than a LS1 even though they are the same displacement?

Because the LS6 has been tuned to give better specific output!

It's all the same thing no matter which way you slice it. Specific output (bhp/litre) is used all the time. But usually indirectly and not by name, but this makes no odds as it is still the same thing.


Yeah but HOW has it acheived such good power to weight???

Do you see sports bikes with their Vee twins running OHV motors or OHC?

Could you have a 1000cc OHV motorbike engine making 180+bhp?

Just think about it?

YES you are AMERICAN, YES push rod V8's are the MAIN STAY of American cars. But look around you? Are you so blind by technology? Do you not see the evidence, logic and commen sense?

OHV is great But look past your own preconceptions and prejudice.


What conditions are you setting for it?

Off boost with the correct gearing then yeah it porbably is very economical. On boost not so. But what's your question? It just seems random and has nothing to do with what is being discussed.

OK Mr Clever What the SMEG is CAGS for then?

I expect an answer to this!

YOU CAN NOT COMPARE ENGINE FUEL EFFICENCY UNLESS THEY ARE IN THE SAME VEHICLE.

On a test cell you could measure minutes per gallon this would tell you which engine is most economical.

Different cars with different co drag, frontal area, weight, gearing, tyres, etc. Will make the results pointless.

Again I'm not sure what this has too do with OHC compared to OHV.

eh?

2.4 litres is 2.4 litres, meaning 5.7 litres is a much larger volume. Meaning over double the amount of air.

So NO.

Small engines are more economical as a rule, hence most places small 4 cylinder engines are the preferred choice.

Can they be uneconomical - sure!

But a large displacement engine will always have lower limits due to it's displacement. Hence GM has developed "Displacement on Demand" where the PCM shuts down 4 cylinders. Meaning it only has to supply fuel to four of them, in essence only half the amount of fuel.

Sparetire

1)I beat this horse to death 3 times over like a year ago, but once you get into turbos, the turbo is the ultimate determinant of power. It limits how much air can go in and out. You can take a GT30R turbo on a drag built B20 and on a Viper motor and guess what, assuming neither blows up (a huge assumption) they will in the end be limmited to a similar power figure by the tuebo. The Viper will make a bit more and make it lower, but my guess is both would be within 150HP in all out form.

You see, while the Viper makes more power for a given boost pressure, the GT30 can not supply as much boost pressure to the Viper motor efficently as it can to the B20. The Viper motor simply swallows more air at any given boost, making the GT30Rs limits lower in that regard. So the B20 might be at 35PSI for peak power, while the Viper is at 20. But both cars are making say 600-700 at the wheels. Drasticly different power bands? Yep. But that peak airflow is the same. The compressor can only flow so much. How much displacement it's trying to feed really does not affect that number much. Similarly, if you take a small T-25, and put it on a Viper., your limited to like 275ish at the wheels. Thats right, the Viper would get slower than stock with a single T-25 setup. It would make the most isane torqe ever at about 2000, but then it would fall flat on its face. No power, and slow as hell. The NA Viper motor processes more air than a T-25 could provide regardless of boost you try to run with it. It just cant flow enough.

2)HP/L in and of itself is not meaningful. BUT. It is a nice indicator of an engines overall performance. The S2000 has great HP/L and it is decently quick, despite being a 240HP car thats not really all that light. High HP/L tends to be found in cars with good top end torque (otherwise known as HP) that allows them to use gearing effectively.

HP/L is an indirect way of hinting at how an engine performs. Its not at all huge metric for a street car where there are no displacement rules.

3)DOHC does make higher HP/L relative to OHV in just about any app. BUT. When you look at HP per pound engine, which is a very very important metric for any situation, OHV often get the nod.

What people often dont know is that OHV was invented after OHC as a means of making motors more compact. OHV is actually more complex and a heavier valve train than OHC as well, the price you pay for the light weight and compact size. OHCs dont have pushrods, they dont have a cam in the block that is then linked to the head. The OHCs just have a belt going to the cam(s). There are rockers, lifters, valves and springs and retainers and thats about it really. It's all enclosed in the cylinder head. So the block casting is much less complex (which is one big reason most went to OHC IMHO.

Sparetire

[QUOTE=300bhp/ton]

eh?

2.4 litres is 2.4 litres, meaning 5.7 litres is a much larger volume. Meaning over double the amount of air.

So NO.
QUOTE]

The lower rotational mass of the smaller engine will tend to allow better mileage, buts thats a broad generalization.

400HP requires a certain amount of air period. And the amount of air requires a certain amount of fuel at a given AFR. Period.

Further, a larger volume in which to combust the air and fuel will often make for a more efficient process at a given pressure. More consistent diffusion means more even, predictable flame front.

In the end a 2.4 floored making 400HP burns about as much gas a 5.4 making 400HP. Its all about how much fuel energy can be released per unit time.

Now in cruising you have a bajillion other variables........

300bhp/ton

[QUOTE=Sparetire]Agree 100%

slick1851

The Viper motor wouldnt make good power at all a GT30 is way way to small and will choke the motor, while the B20 will end up being faster with the GT30

You have to match the turbo to displacment etc

300bhp/ton

Can't disagree with any of that.

But my point has always been having BOTH engines with the same displacement. Sadly the motor industry just doesn't give us large displacement DOHC's to play with - yet. But maybe one day.

This is true, but it can still be handy, or rather I should say interesting.

I'm not sure whats happening concerning the 6.4 DOHC V8 GM was supposidly working on. But boy want an engine that could be. And we all know that as long as it carries the right attributes a 6.4 DOHC would outperform a 7.0 OHV.

This is true, although in a car weighing in at ~3600lb having an extra 50, even 100lb in the engine is only marginal to overall performance. Plus not all DOHC's are massivly heavy. The Jaguar AJV8 DOHC engine weighs in at about the same (slgihtly less) than a LS1.

:thumbs:

ss1129

iTrader: (16)

So is this topic about dohc or hp per liter?

DOHC is cool and all, but this is LS1 tech, and last I checked they were OHV motors. To try and argue against them is kind of pointless on here. And last I checked the ls series motors don't have 2 1" valves.

Cags has nothing to do with the engine. I know what its for Im not stupid. But there are automatic ls1s out there cruising the streets. I have seen them.

Again...I have never in my 28 years of existance ever...ever heard anyone say "man that car puts out wicked hp per liter". Nobody cares about it. Im not saying it isnt useful, just nobody cares about it.

Also Im sure when engineers are designing motors they dont say "man we need to make a sweet motor that puts out 89.567 hp per liter" Again, because its stupid. Hmm have I ever seen a car advertising hp per liter??????







NO, because its stupid. Its like a house listing sq ft per room instead of total living space. But in the end its all details, and Im not really for aruging on either side anymore.

ss1129

iTrader: (16)

What about valve sizes? I guess they dont count.

Ok I understand that 2 motors running the same displacement and same cam specs with one being doch and one being ohv that the doch will produce more hp. But as you add larger valves to the ohv motor that hp difference will shrink. I do also think that ohc is more reliable....but at the same time more expensive. but in the end its to each his own.

LSWaaa?

300bhp/ton

Actually I think it's about a Honda engine.

But that isn't what my comment was based upon.

Essentially someone (not you) blatantly said "HP per litre" is only a ricer thing.

I disagree, as I'm not a ricer. Far from it, I'm probably somewhere between Red neck and country hick. But I find bhp/litre a usful metric and can see the logic of it. This simply expands into where it can be used and what allows very good bhp/litre, hence the topic of DOHC.

Yeah, but it's still tech.

Why?

1. I'm not arguing against, I've mearly stated fact (or at least assumption).

2. Do you really believe I living in England where fuel is near $7.00/gallon would own and drive a Ls1 Camaro and be a member of a board like this if I didn't like them???

But my personal bias doesn't alter any of the facts. DOHC is superior in HP terms and me jumping up and down claiming "ls1 is best" "ls1 is best" "ls1 is best" "ls1 is best" "ls1 is best" won't alter that fact.


Don't believe I said they do. I just used some simple numbers as an illustration.

No but it has a lot to do with fuel economy.

Then why did you disagree with me about it?

2 points:

1. You where talking about the LS7 in the z06. This is NOT available with an Auto.

2. Auto Ls1's are not as economical as manaul cars.


I'm saying anyone should. But I bet you have heard someone say this engine makes 'xxx' HP from only 'xx' litres.

It's the same thing.

I mean come on the LS1 is a marvel of modder technology it produces nearly DOUBLE the HP the a 1977 6.6 Poncho Trans Am does.

More power + less displacement.

Maynot directly, but it's still there.

I mean if GM lanched a new car with a 8.8 litre engine but it only managed 270bhp would you be impressed?

I guess probably not, because that's embarrising low HP for the displacement.

Or to play it on the other hand if Honda released a new 2.0 engine for a future model but it only managed 102bhp would you be more impressed than the 237bhp from the current 2.0 litre?

umm....

Your chioce, which I fully respect.

Well in many ways they will.

If they have a performance goal and they know the weight of the car they will be able to calculate how much HP it will need to acheive the performance goal.

Take the Audi TT. It's built on the Golf platform and at the time the available engines where 2.0 n/a with 150bhp and a 1.8 turbo with 150bhp.

Neither was powful enough to provide the required performance, so the engineers will have looked at which engine could acheive the goal better for less money.

Due to the advantages of FI, they opted for the smaller displacement engine because it was easier/cheaper to get it to produce 225bhp.

The 2.0 could have been used but to get 225bhp n/a from it would have made it very racey and not suitable for mass production for it's target audience. And turboing the 2.0 would have added extra R&D costs.

But because the 1.8T was capable of better specific output it made the obvious choice.

Hope that makes sense, I know what I mean, but it's often hard to convey it in words.

Yep Honda did, so have Caterham. And many have in the past also.

ss1129

iTrader: (16)

I dont think I mentioned the ls7. Buts thats fine. I see eye to eye with you on most points, but for top end hp wouldnt top fuelers use dohc if it was better?

Sparetire

A DOHC head will get more curtain area over time with lighter smaller valves, lower lift and shorter duration. Thus making more streetable power all else being equal.....which it isnt. Displacement is still key. But look at the available bore, lets say 4 inches. The object is to get as much circumfrence as possible from as many or as few vlaves as you want inside the bore, without hitting the spark plug. You can only go so big with a single circle before you run out of room. With a 2V setup, they will run out of diameter quick. Now with 4 smaller circles, suddenly you use a lot more of the bore area for breathing. So you dont need huge lift or duration to get curtain area/time.

Think about it. Except the old SN95s, who talks about aftermarket heads on OHC cars? Almost nobody. Its not needed. My DSM has a full 20% more displacement than stocker and the stock head and cams even do great. I might do a mild upgrade to the cams, like the 272s some Evo guys use, but I might not. Then again, I'll have to run over 20PSI and deal with all the challenges that brings about to hit 11s. A Big OHV does not.

Give and take. Frankly I'd take the massive displacement advantage and a strong tranny over a better head most of the time. But to have both...holy crap. I think I would be out and out scared of a turbo DOHC LS motor in my garage. They are pretty much as powerful as anything I want to be responsible for as is.

300bhp/ton

I think that's an excellent point, why don't tpo fulers use DOHC?

Well the only logical assumption I can think of is:

a) Are they regulated to prevent use of DOHC. In the same way as twin screwm blowers where outlawed against Roots style. The performance gap was too big between them. This is also the same reason why turbochargers aren't used. They simply are not allowed.

b) Drag racing is very much an American thing. And OHV motors are the main stay of American racing, so I guess going to DOHC would be slightly out of character. Also a lot of poeple (such as some of those posted in this thread, simply don't believe the advantages of DOHC setups).

c) Lack of availability. All top fuel motors can follow a line of heritage back to road going engines, all where OHV's. There simple are not any mass produced DOHC of suitable displacement to be used for this level of competition.


Have you ever heard of Engine Masters? They have a website, David Vizard often writes for them. Very informative and some great articles.

However they run an annual contest to make the most HP from 'x' spec motor. Big block or small block with a maximum displacement. There are also limitations on fuel and parts.

But all OHC engines are outlawed and not allowed to compete. I believe this because OHC would under these conditions trounce the OHV motors. But this would of course not be good for the good ol' American V8.

Ford mod motors even though not great are not allowed to enter this contest. But I guess the real threat comes from engines like the Mercedes AMG 6.3 litre V8.

Personally I just find it interesting, as I love all things automotive. But I would be keen to see what some of these engines can actually do.

brad8266

iTrader: (23)

Thsoi thread got completely jacked.

Its too bad that some people get so upset over a simple comment, but whatever. What else could you expect from Internet racers.

Hot94Z28

I hate it when someone jakes at tread . I wish they had to have a discustion about something other than what the thread is about they would take it to PM. As far as the k24

zigroid

iTrader: (22)

no ****.

300bhp/ton, you really need to quit thinking in hypothetical situations and realize we live in the real world. I don't have the time to reply to your post now but I'll address all your ignorant ramblings tonight.

Sparetire

A thousand apologies your highness.

The original question got answered and the convo went elseware. If you dont like it, read another thread. Its not like we are muddying up the information about a race that has happened.

brad8266

iTrader: (23)

See what I mean? I never asked you to apoligize for ****, so please spare me the apology man.

Ya know its funny how everyone gets all buttsore on the Internet and wants to argue and benchrace all the time but when you go out to car club meets even if the meets have imports and domestics there is not any arguing like what goes down on the Internet. Its so civil, but once your behind the keyboard **** changes and people grow ***** or something and just wanna talk ****.

GMmexican

iTrader: (7)

whats the H22 in the import world'?

300bhp/ton

Isn't this EXACTLY what you've been doing. After all it was your post that caused this. And you subsequent replys.

Kettle calling the pot black maybe......