12 psi in 4th and 5th on stock car

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10-24-10, 10:38 AM

#51

adam c

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Quote:

Originally Posted by arghx

The primary has its own actuator (precontrol actuator) with its own solenoid and pill.

I don't think this is correct. The other pill, in the prespool (precontrol) line, acts to spool the secondary turbo before it comes on line at 4500 rpm. There are only two pills acting to control boost.

Quote:

Originally Posted by arghx

Your secondary boost sounds fine to me. Just about every factory turbo car tapers boost a little bit near redline.

Yep!

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10-24-10, 01:47 PM

#52

adamrs80

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Quote:

Originally Posted by adam c

12 psi on the primary won't hurt anything because the stock fuel system will plenty of fuel at low rpm. On a stock car, boost will tend to drop off a little at high rpm in higher gears. Sounds like your problem is solved.

BTW, you cant go 120 mph in 3rd gear

Well maybe I did shift into 4th then. It's definitely tough to watch the speed, rpms, boost, and think about what gear I'm in. I needed a passenger to watch the boost for me but it was 7:30 am and my wife was watching our girls.

Good to know I'm okay fuel-wise at low RPMs and 12 psi.

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10-24-10, 03:38 PM

#53

arghx

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Quote:

Originally Posted by adam c

I think I was unclear. The precontrol has the dual purpose of prespooling the secondary turbo and controlling boost before transition. It controls boost by bleeding exhaust from the primary turbo in order to spool the secondary turbo. During prespool the secondary turbo dumps its pressurized air back to the airbox through the charge relief valve.

Before transition the wastegate is completely shut with the wastegate solenoid fully bleeding air from the actuator. The precontrol actuator regulates boost and the precontrol solenoid bleeds air away from this actuator. Without a way to reprogram the precontrol solenoid duty cycle (PFC is the only way to do that really) the pill size would have to be changed to lower boost. Otherwise you would have to bypass the factory precontrol solenoid altogether. After transition the precontrol is fully open and the wastegate is duty controlled to regulate boost.

See my "Sequential turbos demystified" article: https://www.rx7club.com/3rd-generation-specific-1993-2002-16/why-engine-so-damn-complicated-part-1-sequential-turbos-demystified-841821/