TeeKay

white2001s10, that's a thoughful post! Here's my point of view (slightly different). When you help the flow charateristics of an FI engine, you can get the same air through it at a lesser boost, so the hp does stay about the same. However, here's where the increased flow is beneficial, turn the boost back up to where it was before the change and your cfm increases making more hp on the same psi as before. That scenario has the benefit of cooler air in.

An example: 430 hp on a stock engine at 7 psi. Turn the boost up to 12 psi. You'll get a power increase, but the charge will be hotter, negating some of the gains due to potential detonation. Same engine, add better flowing heads and keep the boost at 7 psi and you will increase the power also, but the charge will be at the same temp as before. So you get the full benefit of the flow increase. Essentially you are increasing the engine's VE, which makes it take more air easier. Not to beat a dead horse, but that is what happened with me.

I've said it twice now, so I'll shut up!

Pro Stock John

iTrader: (34)

Restriction = creates heat

Seems like there are two issues at play:

-heat
-efficiency

A restrictive/engine setup will run into heat issues before a setup with bigger valves, better flowing heads and intake.

TeeKay

^^^^^ What he said! lol

BTW, I just re-read Wet 1's ?? on page 3. How much difference does it make 20 or 200 hp? A 1 ppm increase in air flow = about 10 hp. With a 383 stroker at 6000 and 90% VE, it flows about 41 ppm N/A. At 100% VE it flows almost 46 ppm. So that would be about a 50 hp difference. With 7psi boost that 50 is multiplied by the pressure ratio (1.47) for 75 hp. Substantial, I would think. HTH

white2001s10

iTrader: (4)

I'm not disagreeing at all, and in fact most of it is thought exercise anyway. It always will come down to how any particular combination actually responds real-world. Sometimes the results are unexpected due to the numerous variables involved.
I did want to go over the one thing I said one more time for further thought.

Try to picture this. The intake port made larger will increase CFM and lower the boost... a known fact. Roughly the same mass is moving into the cylinder due to the decrease in temp, but the pressure difference across the valve (the driving force to fill the cylinder) is less. The less pressure drop combined with a denser (heavier) mass will generally slow down the movement across the valve. The slower velocity may also take longer to overcome the exhaust pressure still in the cylinder in the case of a turbocharged engine. In this case the period of the intake lobe becomes that much more significant, and the law of deminishing returns comes into play again.

Again, since the mass going into the cylinder at the lower boost is roughly the same, the mass of exhaust will also be the same, meaning the same backpressure will be present, but with less pressure on the intake side. This ratio doesn't work in favor of the whole idea of turbocharging.

The whole idea of turbocharging as I see it is to sacrifice efficiency in order to produce a substantial net gain in power.

Wet 1

iTrader: (4)

Thanks for bringing this thread back, there's some good discussion here. What seems like a simple question isn't as simple to answer as most would think. I have my own personal thoughts on this topic, but find all the alternative viewpoints very interesting. I still find it disturbing that so many people think "just turn up the boost if you want more power, rather than spending the money on heads, cam, intake..." is the answer.

white2001s10

iTrader: (4)

If you simplify or reduce this equation or question, doesn't it then become the question of
"Do I get heads and cam, or do I turbocharge?"

Wet 1

iTrader: (4)

I my case, too much is always better... the answer for me is both!

There's little dicussion around here about air flowing inside the engine, mostly just about the power adders themselves. The subject was really brought up to spark discussion on a topic I find interesting, not so much a quest to find an answer to a personal question.

rjw

iTrader: (3)

Turning it up is in many cases is the easy way, for turbos, centris, etc.

At least two of us in this thread have Eaton blowers, so we HAVE to look at alternatives and for at least two reasons

1) The heat made by the blower when boost is turned up, which causes extra power to drive the blower as well as extra load on the IC. Not to mention that while I have spun some of the smaller Eatons to 21k and 21 PSI, unless steps are taken to get rid of the heat, the NET power gain can be minimal.

2) In my case with the MP112 mounted on the manny with an AW IC seeing engine heat, the IC is not that efficient, not to mention flow capacity and pressure loss thru the IC.

I believe that TeeKay may be in a similar situation. So, in our cases, anything that can be done to improve flow i.e TB, MAF, heads, etc. MAY allow for more flow and/or less pressure to make the same or better power.

Another factor is that we are not blowing through the TB, therefore converting to an AA or isolated AW setup means a much longer run between the TB and the intake.

Once of the pluses to our setups is very small throttled volume. This doesn't necessarily mean more power , but it does mean better throttle response.

Also, any added pipes, etc. between the power adder outlet and the intake can cause a pressure drop of maybe a psi or more due to friction.

Just some more food for thought...

white2001s10

iTrader: (4)

A simplified answer seems to be that for a limited power level it makes more sense to turn the boost up, but for really pushing it you simply do everything you can including turning the boost up.

Nothing is ever that simple though. Since a turbo has physical limitations on its own efficiency range and CFM output, you have to determine where your turbocharger is in this range before you can decide if increased CFM is in the cards. Some people who turn up the boost may not find any extra power at all.

For others, adding cam and heads may not find any extra power either due to reaching the CFM limit of the turbo.

abbaskhan

heads and cam at the same boost level will make a big differnce (but referance it in the heads or intake manifold the intake pipe might show slightly lower boost numbers even though the heads flow much better) assuming your turbo or superchager can compensate for the added airflow without a severe increase in intake temp from it spinning harder. any one who tell you otherwise is lying or doesnt know. more volume less compression of the air will always spell more power even at moderate boost levels assuming your compensating for your increase, in tuning, intake pipe size , etc etc(look at the boost level of indy cars in the past some only ran roughly 6 pounds but made insane power for 2.65 liters why??? heads flowed incredible numbers!!!) but all things have to matched pretty well for it to work with no adverse affects ( in essence little or no drop in low end power production)
spend money in a well balanced system. you wont see the highest numbers but for a budget your car will extract max performance at all rpm's (ive seen 800rwp cars trap better then 1000rwp cars) . be sure you do reseach, putting a 106mm on a 346 and 50lbs of boost might sound like a good idea but drivability will be borderline at best and you end up like a 88mm turbo supra with out nitrous ( you just wait till my boost hits in a few mins ill catch you)..... thank god no one got into safe BMEP on pump gas for a lsx type forged motor (although im am curious maybe 350~400 with intake temps in check and chamber design opitmized) that would be a discussion

TeeKay

You folks seem to have a handle on the details of the subject. I'm what you call a "practical" hot-rodder, that is I like the technical a lot until it gets too cumbersome to deal with. Then I go back to the basics of what works tell me (IOW testing). It's always seemed to say for me, "Maximize VE, then do what you want with the rest. That gives the best numbers."

You all have some good points and it's a pleasure to participate in a damn good discussion!

Wnts2Go10O

iTrader: (12)

things that increase airflow does a few things as been mentioned.. 1) less restriction which in turn means less boost
2) more power from said increase in flow
so logic would dictate that the better the flow at the same amount of boost = more power.

longrange4u

iTrader: (2)

So the theory if I understand it correctly.....

320HP Base LS1 motor + Heads, TB, cam, etc = 380HP (The numbers are not factual the formula is what I am seeking)

380HP Modded motor + F/I @ 8lbs(for the purpose of the argument we will saw F/I adds 60%) = 608HP

Vs:

320HP Base LS1 motor + FI @ 8lbs alone = 512HP

The mods in this example added 60HP to a NA motor. Where as the same mods on an F/I motor added 96HP

So in summary... the benefits from a engine modification:

Base Motor + Mods x FI increase % - Power loss due to heat increase of air = HP

So the mods to a motor proportionately increase with the F/I % increase. Resulting in a 30 HP modification (Such as heads) could translate to a 45+ HP mod through F/I.

Someone please feel free to shoot me down if I am way off.....

WAHUSKER

iTrader: (4)

IMO if you are going with a stroker, better heads are an obvious choice. As is a cam that matches. More cubes will require more air. But you don't really need a $5k set of heads for an FI motor. Unless your goal is to run 8s.

And some of you touched on why freeing up air flow drops the boost level. A s/c or turbo makes boost by increasing the volume of air going into the engine. If you increase the cavity it has to fill, it will still be pumping out the same volume it was, so the result is the psi goes down. But you didn't lose anything.

A friend of mine went from an LS6 intake to a Edlebrock & lost 2 lbs of boost. But his car dynoed the same. When he pumped the boost back up to where it was he gained 40hp. So if you run smaller heads & intake on a big-cube motor, you will get higher boost, but you will also lose power because you're restricting the motor. Or at least that's how it seems to me.

TeeKay

8KickassRS9, longrange4u and wahusker, you have all spoken wisdom. lol Like I'm a wise man (not!).

Seriously, wahusker, that exactly how it happened to me 2 years ago. Kickass, you got it IMO! longrange4u, exactly, the pressure ratio amplifies the N/A increase by the same amount assuming heat is under control.

BTW, an article in GM High Tech Performance showed a 37 hp gain over stock with the AFR 205's. At 7 psi, that should be worth about 55 hp. I wouldn't sneeze at that!

white2001s10

iTrader: (4)

I was hoping this discussion would continue.

Let me throw out some scenarios as examples.

Car A is turbocharged with 10psi and makes 500hp

Car B is the same but adds $3k heads/intake giving 7psi and makes 500hp

Car B then tries to turn the boost up to 10psi but then only makes 470hp because the turbo exceeded the physical limit of moving CFM through so the intake temp increased significantly.

Car B is $3000 in the hole making less power and then has to order a bigger turbocharger to increase the CFM capacity. With the bigger turbo car B then reaches 10psi but has significant lag aggrivated by the larger heads/intake. Car B then makes 600hp but actually runs a little slower. Car B then adds a nitrous shot to cure the lag and goes on to make 700hp with about $5000 in upgrades.

Car A with the smaller turbo turns the boost up to 12psi and adds a $300 dry nitrous shot to make 700hp with stock heads/intake and no lag.

happy ending

rjw

iTrader: (3)

If this were to happen, then Car B obviously didn't look at the big picture and got what he deserved.

Car A could go on and blow up the engine due to the added heat of upping the boost

Not so happy ending...

And your point is?

More BS...Car A fries everything and buys the smaller turbo, stock heads, etc to rebuild his setup from Car B and goes back to 8 PSI

Car B uses the money to hire someone to re-engineer his system and ends up making 1000 hp without the juice.

So what's the point?

Wet 1

iTrader: (4)

LOL, I think we just took a wrong turn.

longrange4u

iTrader: (2)

White... I dont think your examples are exactly accurate:

"Car B is the same but adds $3k heads/intake giving 7psi and makes 500hp" What we are saying in this arguement is that when you increase the mods ie: the mods you offer above... the PSI may drop to 4-5 due to better flow numbers but the RWHP would stay the same (500 at 4-5psi) so then the result is that when you up your boost back to pre-mod boost pressure (7psi) your hp would increase in turn (550-575).

Of course the numbers for HP and psi are speculative... but the idea remains solid. If you added 3k in mods and turned up to 7psi AND made the SAME hp (500) then something is wrong.

rjw

iTrader: (3)

I agree...

But I think that I already said that, in a different way...