11 to 1 Comp w/ Boost - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 03-21-2012, 06:31 PM   #21
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Interesting Sav. I have a 99 motor now and noticed just as you say. boost is down until I get my clutch in, but at the lower numbers I am running more than the 95 motor liked.
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Old 03-22-2012, 12:50 AM   #22
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too high
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Old 03-22-2012, 01:01 AM   #23
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Quote:
Originally Posted by 1993ka24det View Post
I was looking to raise the comp, then I thought of the F20c and its 11/1 comp ratio. I was thinking of running no more than 14 psi on on it, but just enough to make 250-270hp. What do you guys think?
First off, what turbo were you planning on running?
Second, the F20c has V-tec.
3rd, you don't need that kind of psi or compression to make 250-270 on a miata engine. I'm positive you could make that easily by 10psi on a big turbo.
I said it a million times and I'll say it again: "It's not about the psi of air you can compress (a.k.a. boost)...it's about the volume of air that you can move."
I.E. Little turbo on 14psi may make 240whp, while big turbo on 8psi might make the same 240whp. If you can understand why that happens, then you can understand how to make power.
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Old 03-22-2012, 01:32 AM   #24
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Ok I'll bite. I don't understand this. How does 8psi going into the same engine at the same RPM make the same power as 14psi. Assuming IAT is intercooled to the same in both cases, I don't see how this works.
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Old 03-22-2012, 01:37 AM   #25
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Originally Posted by Boost Joose View Post
10:1 here. 93 for the street(~350whp) and vp113(~500whp) for the track.
You are too retarded to pull this off.
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Old 03-22-2012, 01:39 AM   #26
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Quote:
Originally Posted by Mobius View Post
Ok I'll bite. I don't understand this. How does 8psi going into the same engine at the same RPM make the same power as 14psi. Assuming IAT is intercooled to the same in both cases, I don't see how this works.
Because 8psi on a big turbo is not the same as 8 psi on a small turbo. PSI is compressed air measured in pounds per square inch. CFM is cubic feet per minute. Although the psi's are the same, the amount of cfm's with a bigger turbo will be greater.
The higher the psi's (compressed air), the higher your IAT's should also be. Hence, a big turbo will move a higher volume of air (CFM's) with less boost because of turbo size, plus IAT's should be lower.
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Old 03-22-2012, 01:50 AM   #27
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Originally Posted by Braineack View Post
y8s hit 257rwhp on a dynapak at 9.5psi on his '01. that's 10:1?
I did 240 on york dyno at 10psi with fm base timing map. Five years ago. Dammmnnn

That was with the 01+ 10:1 pistons. I had no idea what i was doing with tuning back then. Motor never kabloodied.

I lost a lot of races at that psi :(
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Old 03-22-2012, 02:08 AM   #28
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All this conjecture LOL.

A well-tuned motor will barely make 72 ft-lbs per L per atmo of MAP at torque peak, at the hubs, on a Dynapack. That may be 80-84 ft-lbs/L/atmo of MAP at the crank, and even F1 and NASCAR motors make 89. It's a number that can't be broken.

And then if the torque only drops 13% (which would be a very good flowing motor) at the power peak, at say, 6500 RPM, that means:

72 * 6500/5252 * .87 = 77 hp per L per atmo of MAP

At 15 psi that's 277 hp

y8s had to be making power peak at 7000 RPM with a 13% drop from peak torque to make 257 hp at 9.5 psi.

High revving Hondas make their hp/L by making their power peak at >7500 RPM.
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Old 03-22-2012, 02:43 AM   #29
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Quote:
Originally Posted by thirdgen View Post
First off, what turbo were you planning on running?
Second, the F20c has V-tec.
3rd, you don't need that kind of psi or compression to make 250-270 on a miata engine. I'm positive you could make that easily by 10psi on a big turbo.
I said it a million times and I'll say it again: "It's not about the psi of air you can compress (a.k.a. boost)...it's about the volume of air that you can move."
I.E. Little turbo on 14psi may make 240whp, while big turbo on 8psi might make the same 240whp. If you can understand why that happens, then you can understand how to make power.
Im looking at a GT2860 or a GT2871, but I dont know how laggy the 2871 would be on the 1.6
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Old 03-22-2012, 02:52 AM   #30
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Quote:
Originally Posted by JasonC SBB View Post
All this conjecture LOL.

A well-tuned motor will barely make 72 ft-lbs per L per atmo of MAP at torque peak, at the hubs, on a Dynapack. That may be 80-84 ft-lbs/L/atmo of MAP at the crank, and even F1 and NASCAR motors make 89. It's a number that can't be broken.

And then if the torque only drops 13% (which would be a very good flowing motor) at the power peak, at say, 6500 RPM, that means:

72 * 6500/5252 * .87 = 77 hp per L per atmo of MAP

At 15 psi that's 277 hp

y8s had to be making power peak at 7000 RPM with a 13% drop from peak torque to make 257 hp at 9.5 psi.

High revving Hondas make their hp/L by making their power peak at >7500 RPM.
Im not drunk enough to do all the math, but yes I know what you mean. Alot of people say HP, HP, HP but actually all about torque
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Old 03-22-2012, 02:55 AM   #31
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I've had a very hard time believing the 257 on only 9.5psi for the longest time.
And since he never re-dyno'd (to my knowledge) its still a mystery to me.
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Old 03-22-2012, 03:40 AM   #32
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If he makes 72 ft-lbs per L per atmo, and makes peak hp at 7000, and his torque at 7000 RPM is only 13% down from torque peak...

or put another way ...

if he makes 72 minus 13% ( = 63 ), ft-lbs per L per atmo at 7000, then he will make 257 hp at 9.5 psi.
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Old 03-22-2012, 03:42 AM   #33
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Old 03-22-2012, 03:45 AM   #34
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FM's 2L stroker makes almost exactly 72 ft-lbs per L, and it loses ~12% of torque, at the power peak which is 7000 RPM:

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Old 03-22-2012, 03:47 AM   #35
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Quote:
Originally Posted by 1993ka24det View Post
If that engine is 3.0L, it's making 75 ft-lbs per L.
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Old 03-22-2012, 04:45 AM   #36
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Its BMEP, and yes that is very important, but revs are important too.
An engine at 300 psi BMEP at 4000 RPM and another engine making 300 psi BMEP at 8000 RPM, which one has more stress on it?
Its for this reason that power is typically used as the benchmark for where things like rods are going to fail.

Now if were strictly talking about knock limitations, then yes, between equal engines, the BMEP is going to indicate said limit. The problem is that were not talking about a simple comparison, such as different CR or boost with all else being equal.
Changing boost changes compressor efficiency, and changing compression changes quench.
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Old 03-22-2012, 09:47 AM   #37
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Quote:
Originally Posted by 18psi View Post
I've had a very hard time believing the 257 on only 9.5psi for the longest time.
And since he never re-dyno'd (to my knowledge) its still a mystery to me.

well I know he made 246rwhp dynojet at the same boost (maybe less), but i know he was fooling with his tune and vvt stuff.

and he did make peak at 7000, or very close to it.


this all happened 4 years ago so everything is fuzzy.
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Old 03-22-2012, 10:36 AM   #38
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Quote:
Originally Posted by hustler View Post
You are too retarded to pull this off.
Hey 250, crank up the boost
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Old 03-22-2012, 12:03 PM   #39
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Quote:
Originally Posted by Braineack View Post
well I know he made 246rwhp dynojet at the same boost (maybe less), but i know he was fooling with his tune and vvt stuff.
and he did make peak at 7000, or very close to it
this all happened 4 years ago so everything is fuzzy.
I mean even 246 is pretty darn impressive at such low boost and pump gas.
And he does have a baller manifold and baller exhaust setup, with a turbo that is running about as cool as it can, so I guess it all contributes to it.
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Old 03-22-2012, 12:05 PM   #40
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just a tubular manifold 2876 with vvt. nothing spectacular that anyone couldn't replicate easily.
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