Last night I went on my second test drive ('95 FD). When I got there, I watched him install(had previously been installed) PFS ECU, and disconnected the 02 sensor. I drove normal until temp., then nailed (WOT) it in 1st. Primary boosted about 14psi (which I thought was high), then secondary ... nothing ... 2nd gear was fine (sometimes-well most of the time--moody) and 3rd was fine (well the one or two times I tried). The car is extremely (beautiful) quick when everything is working together. I didn't make him an offer yet, I wanted to see what you guys thought. We tried resetting the ECU, same problem, he said this has never happen before???

 

What could cause the secondary boost not to work in 1st gear? It worked in second and third...

 

Wow you have a non post ***** thread!

Seriously though, does the boost go to absolutely 0 psi at 4500 rpm? Someone correct me if I am wrong here: In order to get full boost your engine needs to be under load. In the top end of first sometimes there just is not enough load on the engine for it to make full boost all through the RPM range.

With that said I would not be too concerned with that problem as much as I would be about the 14 psi that you speak of. If you are seriously considering this car I cannot emphasize enough that you get a compression test done at a rotary shop or a (wince) dealer. Good luck.

 

Thanks on the non post ***** comment...trying to build credibility...

no the boost pattern (in 1st gear) was something like 13.5-10...8...5...4

second gear was a different story, my head was pinned to the headrest! Why would, what gear or what speed I was at matter wheather or not the secondary boost kicks in?

 

The second turbo doesn't come online until 4500 rpms.

Even with that, the turbos only spool past 4 PSI if the car is under load (so you can't sit there at idle, and rev the car to get 14 PSI. It will only go to 4 PSI).

So, he was asking what RPM's you were shifting at, and wondering if there was enough load to allow the 2nd turbo to come online in first gear.

 

well, in first gear I was pushing 7000 rpm (boost was falling off). same with second, but in second gear there was a dramatic increase in boost when the second turbo was boosting.
Maybe I'm not understanding how the primary and secondary work?!?! lower rpms then higher rpms...I was not just reving the engine I was flying down the street!!! I could tell when (I thought) the 2nd turbo should boost, and it wasn't

 

Check the boost in second or third gear (perferrably in 3rd). If the car can hold boost to redline, then you are fine:

http://www.scuderiaciriani.com/rx7/boost_test.html

Since the car you are looking at is modified, you'll have to adjust the stock boost numbers (which are 10-8-10). However, if you are in 3rd gear, the boost should not fall off after the 2nd turbo comes online.

 

Thanks, that site makes sense. Still, I have no answer of why 2nd boost wouldn't hit in 1st gear...I'm not questioning the boost in any other gear.

 

You are probably out of the power range in 1st gear before the 2nd turbo can do anything. I think that's what Rated R1 was trying to get at.

 

I had something similar.... no boost pass 4500 then if I shifted quick I wouldn't get boost. But if I let the revs dip back down it would pick up the secondary again. After 6 months of trying different crap I went non-sequential and haven't bothered with it. I thought it was a clogged cat so I got a straight exhaust... I thought it was a hose misplaced or something so I did the hose job, no change. I didn't get to checking the solenoids and I bet one of those was not working right. My bet is to check all your hoses and test your solenoids.

 

thanks, how can I find ot how to test the solenoids...its not my car yet...

 

You just use some aligator test clips and clip the solenoids prongs to the battery. Doing this should make it switch and I think you can blow though it... but it wouldn't hurt to have a vacuum/pressure pump handy.

 

okay great!

 

Honestly since it's not your car yet I wouldn't get to involved in the troubleshooting process. The botom line is that it is a problem with the vacuum/pressure trubo control system and not a problem with the turbos themselves which is a good thing. Use it to your advantage in the bargaining process to get a good price on the car, and then worry about fixing it.

 

even better! thanks jr

 

I'm probably gonna start sounding like "ttpowered" and his MAP sensor, but I had a problem IDENTICAL to this and it was one of the check valves.....easy fix, but don't let who owns the car know that.

 

after I close the deal are you going to tell me how to fix the problem??? pretty please

 

Get the compression checked...if that checkes out. I'd go for it.

As for the turbos. If you are getting 13+ psi. I wouldn't be too concerned. You'll just have to deal with trouble shooting your sequential turbo system. Like doing the silicone / zip tie job. etc.

That's something that I haven't bothered to tackle. I just converted to NON-SEQ...No more boost issues. Just lots of it! Sweet!

 

If the car is modded, first gear goes by way to fast for load to be seen for the secondary turbo to come on line. It seems to me that 93's were somewhat boost limited in first gear anyhow. If it runs great in the other gears it could be this. If not, I second the check valve reply. Probably the check valve under the pressure tank on top of the motor, but be prepaired if you want to buy one from the dealer, they're like $25.