J Chen

Hi Rage,
How can you possibly attain
460 rwhp with a 57 trim
compressor wheel ?
I bet Tony must be scratching
his head as well.

dmoffitt

rage2 has always been making insane power, look what he did w/ his 2.5 after all. some might say his setups are a bit stretched to the limits but that's where the fun's @ imo

rage - don't listen to these nay-sayers, hehe your car years ago was the inspiration for me to start modding mine!!

J Chen

Yeah but the 57 trim does'nt flow
enough air to support those hp nos.
You're looking at least 520hp at
the crank my friend. Besides the
compressor will be way out of it's
efficiency range. Lots of hot air.

TonyG

Here's a little food for thought......

2.5L 951 engine, with a 60-1 compressor, .58 a/r "P" trim T4 turbine



2.5L 951 engine, with a T04E .60 a/r compressor (partial mapping since I don't know the turbine or spool characteristics).




And finally a 2.5L engine, comparing the 60-1 compressor .58 a/r turbine, "P" trim vs a T04E .60 a/r on the same engine (simulation using the same turbine section)




Don't knit pick this .... this is a pretty close (actually very close) simulation.. at sea level.

The thing here to pay attention to is the fact that with the 60-1 compressor you are "coming into the peak efficiency where as with the T-4E .60 you are going out of the peak efficency (big difference).


TonyG

rage2

2.5L
T04E 57 trim wheel, .60 A/R compressor housing. Turbine is a KKK #8 housing, Stage 3 wheel (according to TEC).
The only thing that was changed was the compressor and wheel. T04E 60 trim wheel, .70 A/R compressor housing. Well that and I'm moving to a 2.8L big bore.
Dynojet SAE corrected. 3700ft elevation. 28psi boost. A/F ratio of 12.2:1, timing in the low to mid 20's.
Yea, that's what TEC told me too, which is why there was no change done to the exhaust side. Doesn't the compressor weight differences cause slower onset of boost (my definition of lag)?

TonyG

Rage


Originally posted by TonyG
If you are looking for less lag, then the only thing to change would be the turbine (housing and/or wheel). Not the compressor.
--------------------------------------------------------------------------------

>>>Yea, that's what TEC told me too, <<<

Ok... so good so far...

>>>which is why there was no change done to the exhaust side. <<<

Huh?

>>>Doesn't the compressor weight differences cause slower onset of boost (my definition of lag)?<<<

Yes... but it's trivial compared to the effect of the turbine size. The turbine is what really controls when the turbo spools, at what rpm the turbo operates, and (to a large degree) what back pressure exists between the exhaust valve the the turbine.

The compressor determines the boost, how efficient the boost is at a given rpm and boost level, and how much air flow is available.

If lag is your issue..... you are looking in the wrong place. You should have tightened up your turbine either (and/or) with a different turbine trim or different turbine housing a/r.

TonyG

dmoffitt

damned compressor maps make me feel so stupid, is there an easy way to read them? i can't seem to find the correlation between boost and RPM?

J Chen

Hi Rage2,
Now that Tony has graciously provided the maps,
I still dying to know how you manage to generate
460 rwhp. You can't attain that figure even with
the 60 trim at 28 psi.

Russ Murphy

I think rage2's thinking (if I may presume) is that since he is moving up in displacment he is effectively reducing the turbine size. If he doesn't want any more lag than he had on the 2.5 and maybe improve the lag, then wouldn't this approach work or am I whacked out here? Wait, don't answer the last one.

rage2

Sorry, I meant the turbine side.
Yea, that's why I didn't change the turbine housing or wheel. Since I'm moving up 0.3L in displacement, that should net the same effect as tightening the turbine specs a bit?
Yep, that's exactly what I'm trying. Theoretically, it should work right?

rage2

That's why I'm hoping someone can explain how the compressor housing affects the compressor map. I noticed David Floyd's 60 trim uses the .50 A/R compressor housing. Mine has a .70 A/R compressor housing. My 57 trim used the .60 A/R housing (seen in 4th pic). Maybe that contributed to it? I did a bit of googling, and found a few DSM's and Hondas using the same compressor (57 trim .60 housing) and they're making similar power figures, around the 450whp range.

SoloRacer

Rage: When did you dyno that kind of power with your car? Last I remember you only made 280 rwhp on Toma's Mustang dyno and all the really high horsepower readings you had were from your blitz power meter and not a dyno. Not saying you didn't dyno your car recently just wondering when you did it and if you could post a copy of the dyno sheet for us.

As for the turbo I have friend with an RX7 Turbo running a T04E 60-1, p-trim with a 1.15 a/r exhaust. He made 365 rwhp on a Mustang dyno at 12 psi. He estimates he is at 400-425 rwhp now at 18 psi - he hasn't dynoed to confirm it.

rage2

Hey soloracer, long time no see.

The 280whp on Toma's dyno was 12psi on pump gas. I'll try to find the dynojet dynosheet with the 460whp run, it should be at work somewhere.

TonyG

dmoffitt

The left side of the compressor map is the Pressure Ratio. The pressure ratio is:

14.7 + Boost
----------------
14.7


The bottom is the air flow that an engine will injest. This is a fixed number determined by the size of the engine.


Here's for formula for Air Flow (which you can convert to lbs/min)


(cubic inch displacement) X (redline rpm) x (.5 for 4 stroke engine) x (Engine Volumetric Efficiency)
----------------------------------------------------------------------------------------------------------------------------
1728 (convertscubic inches to cubic feet)

or in the case of a 951 with a 2.5 liter engine:

151x7000x.5x.85
-------------------
1728

Which equals 259.9 cfm This would be the "normally aspirated air flow".


Then you have to take the normally aspirated air flow, and multiply it by the pressure ratio you are going to be running. Thus:

259.9cfm x a pressure ratio of 2.02 (15psi at sea level) = 525 cfm

Again... the pressure ratio in this case would equal

14.7 + 15
--------------- = 2.02 (pressure ratio at 15 psi boost)
14.7



Now you take that 525 cfm number, and to convert to lbs/min you would simply multiply by .0749 thus

525cfm x .0749 = 39.3 lbs/ min


Now you can look at a compressor map, and say, that for a 2.5 liter 951 engine, with a VE of .85, running 15psi boost at 7000 rpms, the compressor must produce 39.3lbs/min or 525 cfm or the boost will drop off since the air flow requirements go up as rpms increase.



You can look at the “rings” on the compressor map as follows:

Imagine an a girl on an island. The island is very small and there are sharks trying to get her. The island is only 5 feet across, so she needs to stand at the center of the sharks might get her.

The center of the island is the highest part of the earth. Every step she takes in any direction leads to lower ground, and closer to the sharks. This is no good.

Imagine the rings on the compressor map the same way. The inner most ring is the highest part of the island and it has the highest efficiency. Each layer is lower ground and has a lower efficiency. Pretty soon after enough steps you are in the water, and you have horrible efficiency to the point that the turbo cannot pump out enough air, boost drops, and the shark bites the chick. Game over.

Each island is typically marked with a percentage number which represents the efficiency for the area that is circled.

SoloRacer

Awesome. I made 280 rwhp/307 lb-ft torque with my K27/8 on Toma's dyno and I know that your car should make more. What was your peak torque?