[Robert]

Originally Posted by wdodge45

Great news....the reason for the 1.30 AR was we were overboosting with the .96 housing that was ordered originally and we where flat on the upper rpm, the 1.30's made all the differance in the world. It took care of the overboost by bleeding some air and it also helped with the restriction too, the car woke up and was totally like driving a new car with way more HP.
So, will we hurt ourselves here by running the bigger AR or should we drop it down? Or just leave it alone?
Paul Traci's car went with HP66's and they had to re-cam to help spool the turbos faster as they weren't spooling until 4k, but he also doesn't have the GT-K 650's either, and what I'm hearing is the way the compressor is ported on the GT-K 650's and the new wheels this shouldn't pose the isssues Paul is having...yes/no?????
Bill

One question, did Paul's car have the newer F1 turbine wheel? That would have made a big difference as well. Of course we won't know 100% for sure how your car will do with a smaller turbine housing like a .96 until the car is under load on the dyno. If Paul has the same exact motor setup as you and had the F1 turbine wheels and a 1.30 A/R housing and he had to re-cam to lower the spool up time then yes a .96 would speed that up. I'm just leary of the issue you hit before. I don't want you to be flat up top either. Honestly for me its a 50/50 toss up with the A/R just because I don't know if Paul's car and your car are apples to apples. You are correct about the compressor housing ports though. The ported compressor shroud allows some air to bypass the inducer under lower pressure ratio operation which will make the compressor more efficient at lower boost pressure than without it. It will also help get the turbo up to full boost a bit faster for the same reason. Whether or not this will completely make it the same as it was before again I don't think anyone can say for sure until the engine is under load. If you know which turbine wheels Paul was running I could help estimate a little better of course. If Paul doesn't have the F1 turbine wheels or compressor shroud porting then no you should not have to worry about re-camming the car for these units to spool up. It will change spool up time just a bit but like I said before it shouldn't be more than a 100-200 RPM difference. If you ran P trims before with a 1.30 A/R I would stick with the 1.30 A/R housings now. The newer wheels spool up better then the old ones will in the same exact housing. The real question, will the improvement in spool up from the new turbine wheels completely offset the impact of running a larger compressor wheel. My honest answer is it will be very close. With the ported compressor shroud added to the equation to the race is going to be even tighter but I think you'll be ok.