I ran my car out at Ifo in Kansas city, Mo sept 4th, then went down to Tulsa, Ok for the ifo race on the 19th of sept. I'm trying to find out possible reasons why my boost pressure was different at Tulsa than Kansas city. Simple run down stock gsr, 6265s turbo top mount, e85, Id 1000's...etc. I'm using a hondata s300 with pwm control. At Kansas city I was using gear based duty cycle. Boost was kept at 23.5psi to 25psi. Temp was pretty decent, high 70's to low 80's, and partly cloudy. Now down in Tulsa, using the same map and using exactly all the same boost settings, boost went to 29psi. Temp was low 90's and sunny and hot as hell.

If anyone has any insight that maybe, be able to help me out, it would be much appreciated!

 

pinhole or slight leak in WG vacuum lines? A little extra release of pressure before the WG's will result in higher boost levels

 

diff altitudes?

 

Boyles Law? (PV/T=PV/T) change in density altitude will change boost pressure if not accounted for in tuning the PWM control. or like garage808 said, small leak. i have seen both on my car.

 

Thanks for the responses. This helped me get some ideas and hopefully I can resolve my issue. Is there a reference that I can search out that would help me with the D/A calculations and try to figure this out. I do know the domestic guys use readings from d/a religiously, to make adjustments.

On a side note would using two step colder plugs affect the tune at all? went from 7's to 9's.