RX7Wishing

Okay. ive been having some weird off and on boost issues that i have been troublshooting for the past few days. I finally had a chance to get a boost guage hooked up for a few hours to do some pulls.

First, The problem. On Some occasion's the car feels insanley slow compared to other times. I have checked for vaccum leaks in the more accessible spots and i found a check valve that actually came apart under the Vaccum chamber next to the manifold. I fixed the problem and the car actually boosted and felt alot better. However she started falling flat on her face after awhile of driving. So. I got a boost guage and here are the results


Boost comes on around 2600 RPMS and goes up to about 11 PSI then drops to about 7 around 4600 rpms, IT then would climb back ( Quick ) and hold 11-12 PSI till near redline. Now remember that these results were taken about 10 mins into Normal operating temps. After a few good solid runs where the car felt fast as hell i encountered boost problems again.. After about 30 mins of testing and duplicating results the boost dropped off to 6 lbs and would NOT go any higher.. thats when the car started feeling sluggish again. It seems that as soon as the car would get hot from a few hard runs boost would drop off. Now everything is stock on the car except a 3 inch Catback. Im thinking that maybe the intake is collapasing from the heat and restricting airflow?, Thus causing the boost issues.. what do you guys think?!?!? I also found that the Vaccum chamber right behind the altenator has a broken nipple and the hose isnt connected. I know that this is causing some loss of vaccum, but remember the car pulls 11 psi at N.O.T but as soon as it really starts to heatup boost wont pass 6-7 psi.. im stump.. i know some of you guru's have some insight on this... So help a brother out!!

RX7Wishing

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RX7Wishing

*Bump

Damn you guys post alot... sending my thread straight to the 2nd page ib under 5 mins .. *******.. lol

FormerPorscheGuy

Boost loss after it heats up. Sounds like your precat is clogged. Get a downpipe, this should fix your problem.

RX7Wishing

With a DP do you need to do anything for fuel?!?

cruiser

Nope, but you do need a way to control boost. You are already at 11psi on *I assume* stock ECU. Limit it to 10psi and get the DP.

Get ProfecB or Home-depot boost controller. And buy that boost gauge

RX7Wishing

EDIT: Sorry, wrong thread

RX7Wishing

*bump

So do more people agree that a clogged CAT is more then likely the cause..???

adam c

iTrader: (2)

You have found a problem with a broken nipple, and disconnected hose. I suggest that you fix that first. That may solve your problem. I don't think the precat is clogged. If it were clogged, the car would not run worse when hot. The precat heats up very quickly, and should not show different performance levels after a couple of minutes. Clogged is clogged, hot or cold. That being said, a downpipe is ALWAYS a good mod for an FD.

RX7Wishing

What werd

cruiser

Could be also a crack on the corssover pipe (the one coming from the y-pipe attached to turbos) which only shows when the plastics heats up and expands a bit...

Could be number of things. I had some issues with boost also, but after installing intakes and DP the problem was gone (but it was most likely a loose hose somewhere).... so, recheck the hoses, then start buying the good stuff for your FD...

clayne

Excessive cracks in exhaust manifold exacerbated by heat.

This will manifest itself as almost no primary boost then all of a sudden full boost from both turbos. To further confirm this as the problem you may be observing an additional change in exhaust note during the no-boost period (due to the cracks).

Sinful7

You should fix that soon.
I had a check valve came unpluged on the same vacuum chamber, the car boosts fine when I go WOT but when I shift up a gear I have low as boost.

fc1jz

Sounds like the same problem I am having.
I had the sequential setup, and my 2nd turbo would boost fully sometimes.
And other times it would only boost 6 or 7 lbs.
Then, it never boosted past 6 or 7 lbs

Now I changed my turbos and went full Non Sequential.
But I still have the same 6lb boost problem.
Could it be the Crossover pipe?? I am still using the stock plastic upper crossover pipe.
I have a Chipped ECU, DP, Intake and HIflo Cat.
I also noticed a crack in my Oil Filler neck. But I removed both boost lines from the oil neck and plugged them and went for a test drive with the same 7lbs of boost.
I guess I need to pressure check everything in my system.

RX7Wishing

stupid FD's j/j .. yea its a real pain in the ***.. Do you have the stock airbox?

clayne

Wastegate control line pills have been removed when you swapped hoses. Find them.

fc1jz

I thought it may be this also, but I replaced the restrictor pills and test drove it and still 7lbs. Then I disconnected/capped the wastegate completely and test drove it. 7lbs!!!

Could this be a blown 2nd turbo?

I am thinking of just going single turbo if I can't figure out the problem. But I hate that I spent nearly 1g to get these turbo's and have them installed, just to dump them for a single.

My car will max out a hair less than .5 bar and continue to fall off to .35 bar at redline.
I had my hi flo cat checked to see if it was clogged, but it wasnt. I removed the intake assembly completely and it didn't help. I have gone over all the connections 5 times or better. But nothing helps.

By the way, I have no Air Pump, no EGR, no ACV and have used appropriate block off plates. And I replaced all solenoids with resistors.