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I have a GT3076R turbo on my car. When we built the turbo kit, I asked for V bands on both of my turbine housings so that they would be easily swappable. I recently switched from the 0.82 a/r that I did my tuning on back to the 0.63 a/r turbine housing and noticed a few interesting things.

1. Once VTEC hits, I'm running REALLY rich now.
2. I have knock retard around 4500 rpm now. With the 0.82 a/r, I had none.
3. The boost threshold and peak boost rpm didn't seem to change.

Peak boost with the 0.63 a/r comes at 4000 rpm in 4th gear. I have old logs of full boost with the 0.82 a/r at 4000 rpm in 6th gear. Unfortunately, my old 4th gear logs were deleted when I replaced my hard drive which makes it impossible to do an even 4th gear comparison. To ensure that gearing wasn't responsible, I checked my boost response in 6th gear with the 0.63 a/r. Peak boost hits at 3750 rpm. That is 250 rpm sooner than the 0.82 a/r housing.

Conclusions

1. The 0.63 a/r felt slightly more responsive and torquier, but didn't seem to have nearly as much power after it hit full boost.
2. The 0.82 a/r has a minimal change in response for a significant change in power. I went from 12:1 afr to 9.5:1 afr with no changes in tuning.
3. The logs show that on a good day, the 0.63 a/r *might* spool 250 rpm sooner. On a bad day they might be even.
4. When I swap to the 1000 cc injectors, I WILL be swapping back to the 0.82 a/r turbine housing.
5. I do NOT recommend the 0.63 a/r turbine housing. It is too small and doesn't work nearly as well with the larger cam profile as the 0.82 a/r does.

Tim

Chris Macellaro

Hello Tim!



Great looking car you have!

Tim is it possible with the faster spool rate you may be going through load cells that have not yet been calibrated properly?




Chris Macellaro

Tinker219

Ive always wanted to try a 1.06 AR housing; I know when I had my GT4088R, with its .96 AR, I was still seeing 14psi by 5000 rpm; thats quick.

Chris Macellaro

That is a large turbo!


That might be very interesting to see my friend!



Chris Macellaro

timg

Thanks Chris.

One thing I forgot to mention was that the new runs with the 0.63 a/r were at 3000' and the old ones with the 0.82 a/r were at 5000+ feet. That leads me to believe even more that the spool difference is minor.

It is possible that I'm going through load cells that weren't calibrated, but I hit everything from 7 psi to 16 psi at 4000+ rpm on the dyno. It was close to the edge at 4000-4500 rpm and the knock could be a result of bad gas, the elevation change, or the turbine housing. The map was right on for the 0.82 a/r housing though and I never saw knock at any altitude.

Tim