Mystery boost problem
 

Background info:

1992 JDM RHD FD.

Just got the car back from:
Rebuilt street ported motor with ALS apex seals
99-spec twins
replaced all vaccuum lines and all but one check valve (apparently was one short, I've ordered a new one today and will replace the last "old" one)
HKS downpipe
Koyo Rad
FMIC
Efini y-pipe
A/C delete
P/S delete
Battery relocate to trunk
Power FC
NGK Powerdex AFR
Clutch/Flywheel
Ghetto-fabbed intake: The story here is that I had ordered a Greddy Arinix which got held up in the mail (Canada post went on strike for a while so my intake was lost in mail hell, I'm still waiting for it to arrive)

So currently I have two tiny motorcycle filters on the stock piping to the turbos and my air pump is sucking in unfiltered air, and the "other" hoses around the tubo's are venting to atmosphere.

The problem:

I find that in the mornings when I start up and head off, I have no boost until the engine warms up. While this is a great safety feature (can't accidentally boost a cold motor) it still drives me nuts as this isn't how it should be.

9 times out of 10 once the car is warmed up (87+ degrees according to the PFC) I'll have both turbos working fine. At the same time I've also had situations where I'm nice and warm, but the secondary doesn't kick in either.

Once the turbos finally decide to work, they work great, they transition properly and they never stop functioning. It's just getting them to start functioning in the first place.

Any tips or suggestions would be great.

-Geoff

Considering you're in a very cold place, the most likely issue would be that you're solenoids are getting stuck when it's cold. Once the car warms up, then the diaphragms inside the solenoids start to warm up, loosening them so when they're activated they move how they're supposed to.

Also the electrical connections can be a little worse when it's cold, not supplying enough voltage to the solenoids. So maybe once the car gets warm the connectors make better contact and start working properly.

I'm not sure ambient temperature is a good way to go here. It's consistantly 95-100+ degrees F in the summer.

-Geoff

But is this check valve good?? If its not check valves can cause symptoms like this. I would check and replace all check valves and see if this issues continue... My guess is that check valves are bad and when warm it allows air to pass and works. Could be oil inside the valves or something..

Check and replace all the valves and get back to us.

Phil

I'll be replacing the check valve when I get home from work, I had intended to replace them all, but I guess I was one short during the swap, so an old one was reused.

I'm thinking if it's not the check valve it may be the CCV...

-Geoff

Well I replaced the last check valve and I had boost this morning. As long as this continues to be the case, it seems like the problem is solved.

For the reference of others in the future: The valve at fault was the one that goes in line from the Y-Pipe to the pressure chamber. It seems that the one that was re-used was of the shorter rounder type not the slightly elongated one that belongs in there.

I'll do a few other "cold" tests and update the thread later to confirm that this was the solution.

-Geoff

Good to hear.

If you don't already have them, I suggest buying a set of viton check valves from Dale Clark and replacing all of them. Much better quality and airflow then you get from oem or other aftermarket check valves and you eliminate those issues for a long time.

I do!

Those are what all my other valves are. I bought them from Dale prior to all the work, but I must have misplaced one or dropped it as we ended up having to re-use an old one. I guess we picked the wrong old one to use :(

Further update: I went for a drive on lunch at work and had boost immediately. From previous testing my car was usually cool enough by lunch to have to wait for boost, so this is another good sign.

I'll do one last update tomorrow morning so that this thread doesn't keep popping up after the car has sat overnight to confirm that I have "cold" boost.

Unless the problem returns after that, I'm going to consider this solved.

-Geoff

Looks like I spoke too soon.

I started up this morning... no boost until warmed up. Again, once warmed up, everything is fine... this is getting annoying.

Modification changes:

Since this thread was started a greddy Arinix has been added and a Bonez high-flow cat

-Geoff

I should also add: I seem to only been getting 9lbs of boost in first gear but 12lbs in 2nd, 3rd,4th and 5th...

-Geoff