problem while hitting boost?
 

my car runs fine most of the time, but i notice sometimes wen i'm on the freeway in 3rd or 4th gear my psi drops and it doesn't stay at 10. it drops somewhere around 6-7 psi...what could be the problem and how do i solve it??

At what RPM? Assuming stock turbo setup, there is a prespool prior to the secondary coming online at 4500 RPM, which will drop the boost a bit, but it should quickly recover to 10. Otherwise, I'd suspect the secondary isn't kicking in (check the vacuum lines on the turbo to make sure they're all on tight) or you have a boost leak (check intercooler fittings, vacuum lines, upper intake manifold gasket). Are there any odd sounds before, during, or after the boost drop?

yup stock turbo setup, my vacuums read -20 on my boost gauge which is good...but yeea 5k is were my boost drops down to 6-7ish and there's no odd sounds at all.

thanks, ill check my IC pipings and UIM tomoro and test it out

Actually I had a curiousity myself. I recently had a customer come to my shop with his fd R1 It had a cat-back exhaust and a brand new engine( He had showed me the work order from the shop the replaced his engine, turbos , vaccumlines ETC...) The car would on occasion hit full boost and pull hard, but other times it would be a dog.

This was in ALL gears mind you from time to time. Just throwing this out there for conversation sake. I normally work on Rx-8s and I own A rx7 fc.

Stuck actuators, bad sensors, messed up rats nest from the engine reinstall... could be a million things.

same as mine, i wud pull really hard thru all my gears and just occasionally one of my gears wud drop psi randomly, not all my gears wud drop tho. id have to baby it to the psi to get its potential lol it sucks


i hope my problems not all of that lol

I woudl agree with you there, but the guy showed me the recipt for the work, and he spent nearly 11k on the job. They changed EVERYTHING. lol. The job looked very clean and I was impressed. I'd be pissed for spending that amount of money to feel like I had a NA Fd. lol.

He should have taken it back to where he got it done at and have them fix it, for free.

To the OP, there are several solenoids, vacuum lines, and sensors that the twin turbo system rely on to properly operate. If any one of those things is failing it will cause you problems. Unfortunately there is no definite answer to your question. But finding out everything involved with the TT system and then testing it is your only way to figure it out.

If you haven't downloaded the FSM yet, do so. It has testing procedures for most of the things you will need to be checking. Good Luck

hahaa yeea id be pissed too 11k's wayy too much to waste, he shud go back and check the pipings and hoses and tighten them like im about to do :nod:


thanks just DL'd it..yea ill find out by tonight im gonna test it out wen its cooler outside lol

I have the exact same problem with my fd here... just looking at my engine bay and reading here about all the possible things that could be causing the problem is making me dizzy!

Does yours consistently get 6-7psi after 5000rpm, or is it sometimes 10psi and other times less?

Mine drops to 8psi after 5500rpm, or thereabouts. Dyno graph at
https://www.rx7club.com/showpost.php...&postcount=404

At the time I thought it was a vacuum hose issue, but it doesn't seem to be the case - I've looked over it all, and currently get the following pattern:
Initial spike to 12psi, then drops to 10psi.
At 4000rpm it drops to 8psi.
at 4500rpm it hits 10psi with a noticable kick.
at 5500rpm it drops back to 8psi and stays there to redline.

So it appears both turbos are functioning. Perhaps the stock exhaust (note I have a JDM car, so no pre-cat) is restrictive above 5500rpm at 10psi.

I doubt it, considering the stock boost is 10 psi and you can easily get 12 psi, with the stock converter in place. They wouldn't design the exhaust to be TOO small for stock boost levels. Also the factory twins are capable of pushing 10psi or more to redline.

i just fixed my problem (hopefully thats it)

it was my UIM connection, i took off the 4 bolts and put it back on and i noticed that the lower 2 bolts were screwed on all the way but there was still a gap.
then i noticed there was a wire harness right underneath that had a plastic part with 2 holes for it to fit in the lower screws to bolt on and tightly fasten :pat:

i test drove it today and noticed a big difference, it has a better response now and it spools much quicker. hits 10 psi and stays there!

thanks guy u really helped alot

Excellent, congratulations.

it did at first, esp during WOT.. but not consistently it wud jump around sometimes
and i wud lose psi in one or two gears.. my problem was me UIM, the bolts were loose, so there was a leak


hahahhaaa i kno wen i read that i was like :dammit: hahaa

It does seem odd, but there are others who report the same thing.
For example, http://www.fd3s.net/boost_problems.html states the following:
A boost leak may be occuring, but it seems unlikely considering that I can hold 10psi perfectly steadlily below 5500rpm.
One thing to note is that I have an automatic ECU (code N3A8), but the car is a manual conversion.

Glad to hear you got it fixed - good thing it was a simple fix haha ;)
Just to confirm: You are now getting a solid 10psi above 5500rpm and all the way to redline?

haha thanks man! so far im at a solid 10psi, i took my car out for a spin just about 15-20 mins to feel the difference and i definitely feel the second turbo now.

major difference from before, and my bov is louder too :)

ill check the next time i take her out and see if 3rd and 4th gear are at a sollid 10 above 6k

Haha, I remember when I first bought my FD, two of the solenoids were wired wrong, and I got a flat 6 or so psi above 4000rpm. I still thought it was fast (being used to a 1.8L n/a Nissan), but when they were wired correctly I was blown away. Literally :D

Yeah, that's how I'm feeling with my FD, there's still alot of fun to be had with only the first turbo operational... I feel like once I get my boost issues sorted i'm gonna have even more fun. :D

hahahaa yeea same here! i have a civic with 200whp and before i fixed my problem with the FD i still thought the FD was faster and stronger

but now it feels like a whole different car lol