Better Turbo For Built Rb25Det

[zebra]

I think what Ash is trying to say is: 550rwhp is way to much grunt for the S14 chassis already and combine that with an inexpirenced drive on the track.

I tend to agree, you will be faster to begin with with 400rwhp or less and learn the finer points of going quick on a circuit.

[radianation]

That's a fair point, and I appreciate the concern and suggestion for track purposes. Let's hope I'm a better driver than you're giving me credit for, considering I started out on karts at age 5. =D

*edit*

Talk to me a little bit about the factory redline on the RB25DET, what it can be safely increased to without modifications, and the steps required to increase it beyond that? Is increasing the redline required for more power on the engine or should I be seeing my max power more in the 6400 RPM range like the stock setup? I'm obviously seeing my max power at the redline currently, but I think that's because of the turbo compressor map not being ideal for the engine. I suppose the engine flows about 50 at 7500rpm?

Edited December 18, 2010 by radianation

[SimonR32]

Also, back to the possible issue of valve float, if you watch in this video, right about the time where the dip is in the power on my dyno chart you see a puff of black smoke from the exhaust. Any clue?

Black puff out the exhaust could be ping causing the carbon to be cleaned off the combustion chamber and coming out the exhaust

[radianation]

Couldn't that be the result of a weak valve spring?

[Lithium]

I am sure if the guy is fine with the car at 420whp, he's got the peddling to deal with a high power S14 and has an idea of what the chassis copes with a bit of power like.

For the higher power level you are after I'd have thought bigger cams etc would be a good idea too.

[joeyjoejoejuniorshabadoo]

honestly i agree with the 3076 idea...

run e85 and you can see ~350rwkw with brilliant response

i run an HKS 2835 pro s and on e85 i see 323rwkw (432rwhp) with 20psi by 3400

the on/off throttle response is blistering for a 2.5 litre and a 3076 with a good manifold on sugarcubes should see you to ~470rwhp with similar response

[joeyjoejoejuniorshabadoo]

ima post my dyno graph to show the difference between 98 and e85.

this is the same tuner, same car, same dyno, same day, different fuel:

with the 3076 setup you'd end up with something similar to this response wise but with more power

[radianation]

I could always take that in steps. If the power isn't there on pump gas after the turbo swap I just change fuel... Or do you think I should change fuel now and see how the current turbo does?

[joeyjoejoejuniorshabadoo]

changing fuels wont yeild better response.... just same response with more power

imho change the turbo, then tune for pulp, then tweak tune for e85

[radianation]

I was thinking maybe just running higher boost with E85, but yeah I think the Turbo needs to be better matched.

[radianation]

I had a friend consult Garrett Marketing/Engineers directly and here is their suggestion / response:

So, we made some assumptions about the engine.

It is running an air-to-air intercooler.

4 valves/cylinder for .9 volumetric efficiency

It will be using pump gas (though I did try the match with a few different A/F ratios)

It will be used near Louisville with an average barometric pressure of 14.37 and an average temp of 55* F

Actual crank horsepower is approximately 675 accounting for a 20% drivetrain loss to give the 550 RWHP target

Brake Specific Fuel Consumption (BSFC) of 0.46

From what we can see, a 2.5L will have a difficult time making 675 HP at 20 psi without running really rich (I got it there at 9.2:1). However, a more sober 10.5:1 A/F ratio delivers the power at a pressure ratio of 2.8, or 25 psi gauge. This will give the target 675 crank HP at 7500 RPM. Intake manifold temps should hover around 129*, and torque should be 473 lb/ft.

Now, which turbo? Both of the choices Andrew listed would work. The GT3582R will make the power, but the bigger wheels are going to make it a little laggier. Plus, I don’t feel like the added volume is totally necessary given that it is a 2.5L and back pressure shouldn’t be an issue. My choice would be the GTX3076R, not only because it is the hawtness right now, but also because it will be faster reacting and will still deliver the power at ~73-75% efficiency. You’ll be closer to the choke flow line of the map, so the real power will be right smack dab in the heart of the map where you want it. Also, there are three A/R’s for turbine housing sizing. I’m feeling like the larger 1.06 might be the best way to go, but it is kind of guess and check with the turbine housing A/R sizing. The only caution I would have in using the GTX3076R is to watch for surge. I don’t think that it will happen, but there is a better chance of it occurring with this turbo than the GT3582R.

I think I'm going to go with the GTX3076R per the recommendations both on this forum and from the manufacturer. However, I'm not sure which A/R at this point.

[waxracing]

Stop have a look at the airwerx series by borgwarner first

The s200sx is like the 3076 but the extended tip allows it to spool sooner.

Its also not ball bearing so you can rebuild it if you need to

[bradsm87]

Stop have a look at the airwerx series by borgwarner first

The s200sx is like the 3076 but the extended tip allows it to spool sooner.

Its also not ball bearing so you can rebuild it if you need to

If I wan gonna get a BW, It'd be the newer EFR series 4 sure.

[radianation]

Later they added this comment, which is more inline with what I was thinking...

Two small notes about the turbo, one change and one advise.

Rather than the 1.06 A/R, I’ve looked at back pressure numbers and a 0.82 A/R would be fine and get into boost between 500-1000 rpm sooner. A little back pressure isn’t necessarily a bad thing for track and autocross either.

[waxracing]

Its alot more expensive turbo the efr I said airweks because its the same sort of price as the 3076 but a better turbo

[radianation]

Were you thinking something like this?

http://www.full-race.com/store/turbos/borgwarner-efr/borgwarner-efr-7064-turbo.html

[bradsm87]

Were you thinking something like this?

http://www.full-race.com/store/turbos/borgwarner-efr/borgwarner-efr-7064-turbo.html

Yep