RajDatta

Hi guys, I have been running a Garrett GT3076R setup for the last 8 years. It came with a .82 A/R exducer. I was originally running this setup with a factory modified cross-over and headers.

At one point, I decided to switch to SFR headers. While Zagaone was over this weekend, we went thru my dynosheets that show us the engine stops making any additional power past 5k rpm. This is showing us that I am restricting myself due to the 968 turbo S factory intake and exhaust setup.

Moving to a bigger inlet and exhaust is not an option since I want to maintain the factory look. We also noticed that I make max torque at 5k rpm, which seems on the high side. I know my turbo is good for 500hp plus. The idea is that we should reduce the hotside to a .63 A/R. This should help move the torque curve over to the left without losing any HP (restricted due to setup anyway).

Car runs great and hits hard, but I would like more low end torque since it seems the SFR setup moved torque a bit to the right. Since I am restricted on HP by the setup anyway, why not get some of the shifted torque back after the header swap.

These are a few things I have in mind.

1) Switch back to a factory header/cross-over setup
2) Go to a smaller exducer to move the torque band more to the left

Boost is hard set to 15.3psi. Now that I think about it, I can probably reduce the boost as well to probably .8-.9bar or so without losing anything.

3) Lower boost since I was not gaining anything after 5k rpm

Opinions on what would be the best way to achieve my torque at a lower rpm.

Attached are dyno runs.

https://picasaweb.google.com/lh/phot...eat=directlink

https://picasaweb.google.com/lh/phot...eat=directlink

Thanks.
Raj

Thom

Can you post your dyno sheets?

Dwane

Raj, I don't have anything to add. Just wanted to let you know I picked up a stroked, short geared 89 S.

RajDatta

I will add dynosheets asap. Looks like my accnt has issues, as it won't let me upload pics. I have notified the admins.

blown 944

Having an idea of when boost comes on would tell a little more.

For the boost levels you're running I would go with the .63 hot side. It would do more for shifting the torque curve.

I don't know all of the specs but given the info that's where I'd start.

RajDatta

Thanks for your response. Waiting to sort the pic issue. In the meantime, what kind of spec's would you need that would help?

Thanks.

eman930

Before going threw all that work to swap your turbo, why not get an adjustable cam gear and see if you can move you powerband with valve timing

RajDatta

I want to stick with as close to stock setup as possible. I rather make a permanent change than play with adjustable cam gears. I don't like too many adjustments, since it gives one the ability to screw up.

Paulyy

IMO a .63 is to small for a 3L but i rather see dyno graphs, boost graphs before i'd give you a proper answer.

Use photobucket, make an account. thats how i upload my photos.

blown 944

Engine size (assuming 3.0 8 v)
What head and does it have ceramic liners?
Tuning method and equip?

There is a real 968turbo car in my area and I was fortunate to see the dyno. It looked to make 400#ft at around 3800 rpm and up to 470 at just over 4000 rpm. I believe it had a k27-8 on it. The torque fell off to 310 at redline. The hp was pretty steady at 400.

Your turbo should come on earlier and produce around the same power I would think.

Paulyy

i believe the stock turbos are k27/8

blown 944

Generally I'd agree but considering the low amount of boost he wants to run I'd focus on getting the turbo spoiled quickly. A .63 should meet those goals I would think.

Again though, seeing a boost curve and dyno could help a bit.

RajDatta

Links added to thread

3.0 2 valve turbo
2.7 head, JME modded with JME cam
SFR headers
Seimens 72lbs/hr injectors
Factory intake and exhaust

Tuning was done by a shop via factory DME. They know Motronics very well. As you can see from the charts, they did an excellent job tuning it. Their dynapack is a very conservative dyno and shows approx 10-12% below a typical Dynojet. So on a Dynojet, add another 10-12% more for hp/tq ( approx 410-420tq and 400hp to the wheels on a Dynojet).

The set up was originally put together by Chris Cervelli to make 465rwhp at 1.3bar, which is obviously not what I run. He was also planning to run it on his race car with probably a 4 inch inlet and exhaust, so there would have been no restrictions.

Just trying to optimize this setup. I am not looing to make more hp, since that would require inlet and exhaust mods and take me away from the factory look.

Raj

Thom

What JME cam profile are you running? A stock cam sounds good enough for what you are looking for.

Here are Raj's dynosheets.

RajDatta

JME cam profile is very close to stock, so I don't lose much there. I had JM confirm this a while back.