User 41221

I am surprised the SFR headers/crossover pipe flowed well enough to support that kind of performance. I know the set of "Stage II" crap Tim sold me wouldn't have. I am guessing this is a tribute to Chris's ability to tune a car, as I wouldn't be surprised if that was the limitation he had to overcome. Well done, Chris!

333pg333

Oooh...Harsh...but fair....

gruhsy

Nice work Chris. What is your impression of the GTX35R????

thingo

There has been a lot of good dyno numbers on this board with the sfr stage 2 headers.

User 41221

Yep, which is why I bought a set, then Tim sent me some cheap $h!t Midas Mufflers would have been embarrassed to claim as their work. Total, very expensive $h!t that doesn't fit properly.

This thread isn't meant to be a bashfest, but to praise Chris on his efforts. Lets turn this back to the original subject.

Thom

Is that a GTX3582R or a GTX3576R? With what A/R turbine housing?

Duke

Very nice flat torque curve and good results for pump gas. 7 psi at 3.5k sounds a bit low though, what turbine housing was used?

Chris White

The 7psi is a 'fuzzy' number. how you run the dyno session can vary that quite a bit. the test was started at 3k rpm steady speed followed by wide open throttle. If I started it at a lower rpm it would have been a little higher. The acceleration rate (based on the dyno load) also effects the rate the boost builds. the dyno is a Super Flow eddy current dyno, I can program in any load - I shoot for a 'real world' set up to try and duplicate the rate of acceleration that the car would see in normal use.

the turbo is a Tial GTX3582R (.82 A/R)...one of my favorites for 3 liter engines!

Chris White

Me likey.

Duke

True, it's always hard to judge spool up on a dyno. The regular GT3582R is starting to get too small for my engine, a GTX3582R would be a perfect match.. But I'm leaning more towards a motorsport ABS than more power at the moment

Chris White

OK, since the SFR headers were commented about....there was an interesting problem during the first dyno testing.
during the initial tuning I could not control the boost, it kept creeping up above the setting (using an Turbosmart Eboost2). I checked all connections and it still crept up. Then I swapped the wastegate...still had boost creep. Then I tried no boost controller (running of wastegate spring)...no difference. So I pulled out the wastegate and put in a very low pressure spring...didn't help.
after a couple of days trying everything possible I had to take the car off the dyno and look at other causes.
In the end the problem was two fold - the wastegate pipe came of the header at a 90 degree angle - it really should be more of an obtuse angle - but I have seen this before with Tim's headers and it has not been a problem. It turns out that the wastegate pipe had a 1/8" lip inside the main crossover pipe. With the exhaust velocity inside the cross over pipe this was enough to kill the flow in the wastegate pipe. In fact the boost would have still been uncontrolled if the wastegate was removed and the pipe left open!

I believe that this would not have shown up in 95% of installations, this particular engine is working so efficiently that even the smallest details matter.

333pg333

By more of an obtuse angle than 90^ do you mean 'away' from the direction of flow or towards? Assume 'away' but then is this getting into reversion or backpressure as such?

Chris White

I am with you on the ABS! I usually prefer to rely on driver skill and not gizmotronics to go fast....but flat spotting expensive tires is a real bummer! For those that have not driven a fast car on Hoosiers (or similar) it is very difficult to sense one tire locking up - no sound and not much feedback...just a lot of smoke and bad smell!

I still feel that a driver that learned without ABS can drive better than a driver that relies on ABS. Some people believe that the proper way to drive an ABS track car is to just push the brake pedal down as hard as possible and allow the ABS to sort it out, I believe that this makes for an uneven transition to trail braking.

BTW - the car owner is already wondering about going to a bigger A/R on the hot side - I am against it for a street car. On this car I think we are making enough power that adding more will start to create a problem with block stability.

Chris White

describing it is a problem since you can measure the angle from either side! You want the pipe to be at less than 90 degrees from the turbo side of the crossover.

333pg333

I believe that lockup is as much to do with brake boosters and certain pad types as ones right/left foot.
Abs is the lazy man's way but it's also going to be faster the majority of times.