shipdriver

iTrader: (1)

I've been a long time lurker and complete turbo newb here (I just bought the RX-7 in March), but I've about exhausted my wits with endless searching and researching. I have stock sequential turbos and was happy until I installed a boost gauge and saw that I was not seeing full boost. At WOT in 3rd gear, I will never get past 2psig. If I really crank it up, I will see upto about 7psig when at very high speeds (>100mph). Since I don't commonly see those speeds, I normally see only 0-2psig. Note vacuum at idle is 16-18"Hg and when the car is off, the gauge shows 0 psig. I removed and inspected the Y-pipe coupling and after a lot of bending and twisting saw no cracks. I replaced the hose from the Y-pipe to the Air Bypass Valve, but saw no improvement. The crossover pipe seems secure and the intercooler piping looked OK when I took them off. Any help would be appreciated! It would be nice to get full boost on my baby, because it's been pretty impressive even with low boost. Thanks!

Lupercal_CATS

This is the same situation I am in, except that I have not got a boost gauge on my car to see what it is running. The car has really good pick up until about 4000-4500 RPMs when the secondary should kick in. I checked most of the hoses and the rubber couler peice on the y pipe was pretty trashed but I think that is not the only problem.

My guess would be that it is solenoid / vacuum hose related. I plan to change all my hoses to silicone and while I do that check all the solenoids.

Buzzardsluck

Mods? Do you hear a vacuum leak?

It sounds like you didn't test drive the car or check its turbos before buying? Just trying to see when the last time the car was running correctly.

Montego

iTrader: (1)

lol

I have stock sequential turbos and was happy until I installed a boost gauge and saw that I was not seeing full boost. At WOT in 3rd gear, I will never get past 2psig. If I really crank it up, I will see upto about 7psig when at very high speeds (>100mph). Since I don't commonly see those speeds, "

if you were happy with 2 psi you are in for some fun times.

Ok is your gauge an autometer? FYI they tend to suck... Most likely is it's one of your solenoids. If you truly are at your wits end then maybe you should consider taking the car to a shop that knows Rx-7's. Because having an FD at 2-7 psi is a waste. The car barely begins to come alive at 10 psi, and at 7 it's dog IMO.

BTW if you do take it to a shop have them hook up their own boost gauge and verify if yours is working properly. My boost gauge reads zero but at full boost it's always 2 psi off. The only reason I found out it's because I put my car on the dyno. Later on I bought an EBC that reads boost and it was consitent with the dyno readings so I know for sure that my gauge sucks.

rynberg

http://www.autosportracetech.com/RX-7/rx7stuff.htm

shipdriver

iTrader: (1)

Looking at the wiring harness connectors to the pre-control and wastegate solenoids, there is a third connector (2 black and one light blue). What is the third connector for? I found the light blue one not connected to anything. Thanks!

shipdriver

iTrader: (1)

Next question: When the engine is not running, the wastegate and pre-control door levers are vertical but the turbo control lever is at an angle from vertical. Is this correct? I am getting a MityVac next week to check the actuators per FSM/Autosportsracetech, but was wondering if there were any visual checks that I can do prior.
Also, I am seeing no movement on the Charge Control Valve whether idling or stopped and vacuum line to Chamber A removed. It's position is just like in the diagram in the Autosportsracetech t/s guide.
Thanks for any assistance!

Regards,
Rob

dgeesaman

iTrader: (7)

You should start with the basics: vacuum and pressure storage.

Using a pair of long needle-nose pliers and maybe a flathead screwdriver to get it started, pull this hose after the engine has been running and stopped. You should hear a solid 'whoosh' of air rushing in to fill the chamber.


If there isn't vacuum, then you have a vacuum leak from either a loose hose or bad check valve. The mityvac will allow you to directly test the valves, and it will allow you to pull vacuum from this hose while you look/listen for the leak.

Dave

shipdriver

iTrader: (1)

Thanks, Dave! I did three tests with that vacuum tank hose.
1) Ran at idle for a few minutes, shut down and...nothing when I removed the hose.
2) Ran and revved the engine, shutdown and...a small psssht.
3) Ran and revved the engine, shutdown and waited 6-7 minutes and...a tiny pfft.
Definitely no solid rushes of air. Would the check valve between the vacuum tank and the UIM be the most likely culprit if this indicates a failure to hold vacuum?

dgeesaman

iTrader: (7)

Either that or a loose hose. Small splits in the hose near a nipple can be easy to overlook.

Dave

shipdriver

iTrader: (1)

Got my MityVac today! The vacuum chamber, the hose to the check valve and the check valve checked out OK. They held vacuum. However, when I went to test the Charge Control Actuator IAW FSM, I couldn't get a vacuum at all. When I took the hose between it and the UIM (using my finger over the end where the Charge Control Actuator goes), it held a vacuum. But as soon as I hooked up to the Charge Control Actuator, I couldn't get a vacuum. It's like I was sucking in atmosphere directly. Needless to say, there was no movement of the Charge Ctrl Act. Could this mean that it is damaged and leaking air plus stuck open, dumping boost to the secondary side and out the Charge Relief because there is no vacuum for it either?

shipdriver

iTrader: (1)

Holy Crap! That Charge Control Valve is over $400!

yuichiror

iTrader: (1)

You might want to post on our local thread:
https://www.rx7club.com/showthread.p...page=334&pp=15

Our local website:
http://hamptonroadsrotaryclub.com

We have a couple of really good FD guys in the area.
BTW, welcome to the group. Always nice to have another FD in Hampton Roads.

yuichiror

iTrader: (1)

Check the classified section of the forum.

jbrx7tt

Just had a similar issue that we were able to fix without much problem, the secondary turbo was not kicking in just like yours. The boost would just drop after the second turbo was supposed to kick in. Basically took out the intake to get to the charge control valve & vacume lines. Checked all of the hoses and vacume lines which were fine. The little actuator that is supposed to open the valve to allow the second turbo boost seemed to be stuck shut. Not sure exactly how we fixed it but with a screwdriver we manually opened and shut it a few times and it seemed to work after that. Was that the real problem? Who knows but it is a easy and worth a try and worked for me....beats buying a new $400 part! Good luck