Can someone give me a list of the parts of the turbo control system that could possibly cause an extremely late transistion to secondary at anywhere in between 6,500-7,800rpm?

I've replaced the one-way check valve to the pressure tank as somone had suggested in another thread, it seemed to make the transition consistent at least. I've tried 3 different solenoid valves for the charge relief solenoid until I finally found a good one. I've tried 2 different CRVs I had laying around and that also helped a lot. But the late transition is still there.

Thanks.

 

did you check your precontrol actuator, solenoid and vac lines?

 

I'm guessing the precontrol actuator you check with the KOKO process right? Solenoid probably has about 100,000 miles on it but I just replaced all vacuum lines with silicone about 3 months ago and everything is hooked up right and not leaking.

Thanks.

 

Have you looked at this web site yet?

http://www.autosportracetech.com/RX-...leshooting.htm

 

Well since I don't have an assitant at the moment, I'll probably end up taking the pre-control actuator off of my old set of twins and seeing if it makes a difference. If I wanted to replace the pre-control solenoid I'd probably have to order it since I don't think I have solenoids of that type laying around.

Thanks guys, at least it's narrowed down for me now.

 

What's your boost pattern like? It will not transition if it does not have 8 psi, i believe.

 

Instant 11psi on primary
8psi at transition at 6,500-7,800rpm
Instantly back up to 11psi and pulls really really good.

Engine related mods are mild streetport, hose techniques silicone line kit, RX7store 3" downpipe & high-flow cat, 2.25" cat-back into an OPAK racing muffler.

 

IMO, if it's holding 11 psi all the way to 6500, you have already transitioned (the stock system transitions at ~4500) and are using the secondary. I don't think you'd have 11 psi at 6500 w/o the second turbo already on line. Are you using a boost controller or the stock boost "control" system?

If that scenario is true, you are feeling something other than "transition" at the 6500-7800 boost hesitation.

 

I'm using the stock control and there are no other symptoms besides this late spurt of boost. And I have no boost leaks (courtesy of Fighter's Garage pressure tester). I'm thinking the precontrol solenoid as SLOASFK said, I just swapped out the actuator and it didn't help so I put my lower mileage one back in.

 

Sounds to me like a possibility is one (or both) of the turbo control solenoids. It takes both vacuum and pressure to work the turbo control actuator which allows exhaust flow to the secondary turbo. Often one of these (more often pressure) is not working properly and therefore it takes much longer than it should for the turbo contol actuator to move. This is a pretty common problem. This can be checked by t-ing into the vacuum and pressure lines going to the tubo contol actuator and looking for vacuum and pressure (respectively) to hit at about 4,500 rpm (under full throttle). Hope this helps.
--Jeff

 

Thanks guys, really, I know which direction I'll need to take to fix the problem.

 

I agree with Dave. There is no way that the primary turbo can produce 8psi of boost at 6500 rpm. It simply cannot pump enough volume to maintain high pressure at high rpm.

Its possible that your (stock?) ecu is going rich at high rpm, causing hesitation.

 

I hear what you guys are saying, but I also don't think he could hold a perfect 11 PSI through transition without a dip?

 

OK. Dumb question: is what you see at your "transition" really 6500 RPM? Is there any possibility the tach is screwy?

 

Some people (not many) have their secondary turbos spooled perfectly to match the primary at 4500 rpm.

The stock ecu will dump some extra fuel at high rpm (under hard acceleration) when it sees the engine as not fully warmed up. This fuel dump will cause a hesitation. The stock ecu may see the engine as not fully warmed up if coolant temps are under 200 degrees.

To the thread starter. Try warming your car up to 210 degrees, and see if the hesitation persists.