hyperlitenerd

iTrader: (1)

Hello Everyone,

This is a new problem for this week. I can got wot in any gear, and when I get to 4-5k the boost drops to 5-6 psi until red line. the tube for my boost gauge had cracked, so I replaced that. I've looked here http://www.autosportracetech.com/RX-7/symptoms.htm and it does not mention anything about 6psi on the secondary. I've searched around some already, but if you have any insight it would be appreciated.

dhays

iTrader: (1)

I suggest you look at the troubleshooting guide on the same site.

http://www.autosportracetech.com/RX-...leshooting.htm

hyperlitenerd

iTrader: (1)

Upon further inspection there is a gap in my intercooler hose and coupler? I have attached a picture. The car is still hot so I've been unable to tighten it. But could this be causing my problems?

rossc

That might be your problem, but seeing as how you are getting full boost on primary then I doubt it. Check you vacuum and pressure lines related to your turbo pre-control actuator and turbo control actuator. In my experience, a line popped off my pressure tank causing a slower opening of my turbo control actuator which cut my boost in half after 4500rpm.

hyperlitenerd

iTrader: (1)

alright I will try and find those tonight after it cools down, Thanks!

hyperlitenerd

iTrader: (1)

Well The vacuum lines seem to be intact. I've noticed that it was really struggling the further it got up in the rpms. Going to and from school, if I boost is 5th gear, 65-80mph, 1 it's slower, two if I boost for a couple of seconds, after I let off, I get a faint burning smell. NOT A GAS SMELL. I'm thinking maybe a clogged down pipe? What are your thoughts?

DaveW

Getting full boost and power at higher revs relies on getting good intake and exhaust flow. So a clogged cat could very well be the reason.

hyperlitenerd

iTrader: (1)

Good I'm glad that makes sense to someone other than me. This could be the excuse I've been looking for to getting a down pipe!

dhays

iTrader: (1)

You don't need that excuse to get rid of the downpipe. Do it just to get the heat out of the engine bay.

Again, if you are getting good boost on primary and poor on secondary, then in my limited understanding, it seems to point to the control system. If it was me, I'd start going through that troubleshooting guide and see what you can find.

hyperlitenerd

iTrader: (1)

Well I have not installed the down pipe yet. But the boost above 4k seems fairly random now. Between 6psi and 8psi. I had taken some of my tubes out to check something else, and took the time to look at what hoses I could see, and everything is intact as far as I can see. So I'm not so sure it's the down pipe anymore. I'm not sure what I should check next, or where it is in the engine bay.

DarkLikePoe

I'm having the same problem as you. Here's what I think it could be (in order of likelihood):

1. Vacuum leak to the turbo control valve.
2. Ignition breakup.
3. Clogged cat.

I have pressure in the pressure tank, vacuum in the vacuum tank. I'm going to replace the check valve between the vacuum chamber and the actuator because I THINK that it is under boost that it's leaking. My next course of action will be to pull the turbo control actuator itself off and check it. If the diaphragm between the vacuum and boost chambers is leaking, it won't matter HOW good the rat's nest is.

Now, if that's not it, I'll check the cat because it's the next easiest thing to diagnose. If that's not it, it's probably ignition break-up at the top end. I am, however, pretty sure it's the vacuum issue.

Hypothesis for the boost pattern (10-4-6to8):
(1) Primary boosts fine until 4000rpm. (2) At 4000rpm, the Turbo control actuator is supposed to open, allowing exhaust gas to the secondary turbine. It is not opening. At the same time, the charge control valve is open, bleeding primary boost through the charge relief valve, and manifold pressure drops to 4psi. Almost instantly, the charge relief valve closes, but because the secondary isn't getting exhaust, the primary charges the pipes as much as possible, which, at higher RPM, is less than 10psi.

Good luck, and if you figure it out, please post up. I will do the same!

hyperlitenerd

iTrader: (1)

I had not thought of the ignition break up on the top end.

The actuators make the most logical sense to me right now. Since it does fall off after the transition. I'll let you know how it is after the downpipe gets installed.

dhays

iTrader: (1)

Forgive my ignorance, but wouldn't you notice ignition break up at higher RPM? And how would that effect boost?

Likewise, wouldn't a clogged cat effect boost in the primary as well as the secondary, yet he is getting 10 psi in primary?

ptrhahn

iTrader: (9)

Not all of these cars saw 10 psi on the secondary when stock and in good condition... many bleed down to about 8.

6-8 might be fairly normal on an older car.... I'd suspect a clogged cat, either pre or main, fairly strongly. It will affect the secondary far more than the primary, because therte's more flow in twin mode. My car originally showed about 12-10-8 before the downpipe.

dhays

iTrader: (1)

My rotary mechanic tells me essentially the same thing. He really doesn't expect more than 7-8 psi on secondary on stock twins. I still will try to squeeze out some more however.

DarkLikePoe

Yes.

To be perfectly honest, it's exactly what was keeping me from full boost after my rebuild. I was limited to wildly fluctuating and limited boost in the top end. Exactly HOW is beyond my meager understanding, and given the sheer consistency of the problem, I honestly do not believe it to be the cause of my current issue.

Perhaps, though given the lower flow rate from a single turbo through a slower-spinning engine, the drop may not be as noticeable. There are times, to be fair, when I get a very sluggish 8psi on the primary, though I think this to be a function of a sorry vacuum system.

dhays, I am completely in agreement with regard to your skepticism. I truly do not think the problem is ignition or clogged cat. I know exactly which check valve is left to replace, and I'm 90% sure I've got it pegged.

hyperlitenerd

iTrader: (1)

Well an update from my side of things. Got the downpipe in the car, and man, you can really hear the turbos now. But it did not fix my problem. I also had the spark plugs and fuel filter while I was at it. So This leads me to belive its a house or an actuator. So I have taken some hoses off before, and I am comfortable doing that my self. I just need to know which hoses and actuators to check, and their general location.

Thanks!

Edit:

If I put it in 3rd gear on the freeway when it is above 4000rpm, the boost will climb to ~7 and hold there if that helps.

hyperlitenerd

iTrader: (1)

Bump!

Got an IM last night

xaZnCoOLbLeHx: you should change holder/coupler as soon as u can.
[01:20] xaZnCoOLbLeHx: or u should get the efini y=pipe.

Does this a valid thing for me to check? It would seem to me that it would cause boost leak below 4500 too if it was the coupler.

DarkLikePoe

I doubt it's your coupler/Y-pipe. I think it's the turbo control actuator itself. I'll PM you if I find some cheap if you do the same!

hyperlitenerd

iTrader: (1)

ARRRRRRRRRRRRRRRRRRRRRRG!!!!!!

Got word from the shop, a reputable local shop, and they have replaced the vacuum hoses and some of the solenoids. And now there is no boost on the primary turbo. Do you have any idea's what could have caused this? I am not giving out any names, as I am giving them more time to fix it. If this was your car, what would you check?

DarkLikePoe

Beats the hell out of me. Restrictor pills? I can't think of anything else that would change when you're replacing hoses...

hyperlitenerd

iTrader: (1)

Yeah I don't know what would cause it to get 0psi. I can diagnose 5psi, but no psi has me worried. Well it's going to stay there until it gets fixed, a turbo less rx7 is worthless to me.

This is making me think about just selling it and getting an rx8 or a miata.