7THSIGN

Hello,
I am just trying to diagnose my cousins RX7’s problem. Just wanted to know from anybody on here that has experience, how does a RX7 perform and act when the secondary turbo is not working. Example: no boost at a cretin rpm, unusual sound etc… Thank you.

dgeesaman

iTrader: (7)

Second turbo kicks in at 4500rpm. Do you have a boost gauge?

I suggest you read the FAQ, esp. the part about turbo troubleshooting.

Dave

7THSIGN

Trust me I have. I have also taken the car to one of the so called "best RX7" shops by people on this site in my area and dumped $800 on a hose job and checking what is causing boost to drop from 10psi to 0psi at 4,500rpms and they did not fix a damn thing and did not know what the problem is. The shop however did say that they didn’t check the secondary turbo after I called them today.

But thanks for the suggestion Dave

speed7

Had that happen... pretty much resulted in sudden loss of power, back firing (cause of the s* load of fuel and no air). Happend right at around 3k too.

So keeping the turbo from engaging I was able to drive it. But acceleration was slow.

7THSIGN

hmm, I have never heard that before, I will take note. thanks. I also would like to take apart the motor and check the 2nd turbo to see whats going on. just need to find the time, if not, i will take it to the shop again.

dgeesaman

iTrader: (7)

OK, that information would have helped. It sounds then like the boost pattern is 10-8-0 or similar.

Rarely is the problem within the turbo itself - usually you just don't get boost at all the right rimes - so pulling the turbos probably isn't the next step. The problem lies in the control system. Hardened / popped-off vacuum lines are very common problem in this system, and solenoids are the next most likely suspect.

A couple of 'old-timers' have written excellent step-by-step troubleshooting for the secondary on scuderiaciriani.
http://www.scuderiaciriani.com/rx7/boost_problems.html Go about 1/2way down to the posts by Steve Wynveen and Wael El-Dasher.

You'll need a tee fitting and several feet of hose. I had an extra pressure/vac gauge that I used and left my boost gauge hooked up too. It should range at least 20in/Hg to 12psi. With long needle-nose pliers, you can tee into all these vacuum circuits without removing hardly anything.

Dave

Mahjik

iTrader: (1)

If you look at your old thread, it has all the advice you need to get started:

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/help-unsolved-boost-problem-351040/

7THSIGN

thanks dgeesaman for the feedback, the shop tested all vacuum lines and solenoids. also the cvr and other things. nothing was wrong with them. so i have no idea what is going on with this damn car.

Mahjik, thank you for bringing back the thread. I just dont know what else to do. the shop checked everything you guys told me the problem might be.... yet the problem is still there. if all vacuum lines are fine, which they should since we got a full hose job done. and the cvr and all solenoids are fine then what else could it be??? they even checked things that you guys didnt bring up. but that didnt help. i will post a pic of the invoice on what they checked when i get a chance.

I think i am starting to see why they stoped selling this car in north america...... j/k a joke

Mahjik

iTrader: (1)

I would "recheck" the shop's "checks".

mad_7tist

a? does the boost drop very quickly to 0 at ~4500? i am still in the crv camp on this one.

dgeesaman

iTrader: (7)

Do the tests in those posts - the bench check on these parts is generally inadequate. The real test for them is in situ - and teeing into the vacuum lines and doing test runs (engine fully warmed) is the only real way. I was able to get my gauge and tee setup and drive around a 2 mi loop with a single hard run. A mile later, I parked it and left the engine running, moved the tee to the next line, and repeated. Once you figure out exactly where the inputs for the CRV break down, then test the harness. If the harness seems ok, replace that solenoid.

You can simulate engine bay heat by putting the solenoids in an oven, but that's best done during the vacuum hose job.

Dave

7THSIGN

Thank you, I will try to explain this to the shop. I just got off the phone with them. I asked them if they had found anything new on what my problem could be. They told me to wait until early next week because they have a guy in there with the same problem as I do. They sent his turbo's away to be rebuilt because the 2nd one was not working properly...something about a "balance wheel". So I will wait and see if that solves the problem for him.

mad_7tist, the boost drops right at about 4500rpms and it goes down slow, not a instant quick drop.

Thank you.

dgeesaman

iTrader: (7)

That thing about rebuilding the turbos doesn't sound comforting. 99% of the time the fix has nothing to do with the turbos themselves.

You say then, that the boost looks like 10-8-4..3..2..1 or something like that? What is the highest boost it gets, even momentarily, after 4500rpm? Because losing boost as the RPMs increase often indicates a clogged cat (or precat if the car still has one).

I guess with the price of labor, it may make sense for them to replace several solenoids: both of the turbo control solenoids, the charge relief solenoid, and charge control solenoid. Unfortunately that's about $250 worth in parts alone, but if they're having trouble diagnosing it these solenoids are your mostly likely candidates. Replacing them will be good insurance about another one failing soon. And it's certainly a better thing to 'try' than something that involves removing the turbos.

If I were anywhere near Fairfax, I'd come help you run some diagnoses. Having turbo control problems solved by garages at labor rates is a scary thing - some have a lot of experience, recognize the symptoms immediately, and fix it immediately. Others look at the mess of parts and pretend like they know all about what's in there and just burn money.

Dave

iluvmy3rdgen

Yeah it's almost definate that your turbos are alrite. Check the Y-pipe connection on the turbo, if the Y-pipe seal is messed up or the y-pipe is cracked once the acutator on the y-pipe opens up all the boost will leak out. Just a thought.



P.S. There isn't any knowledgable FD owner near this guy willing to help?

7THSIGN

dgeesaman, I really appreciate it that if you were in my area, you would take the time to look at the car. You are one of the few who have commented on the cat problem. Do you think it would be ok to remove the cat and run straight pipe to see if it would hold boost? Or should I just replace the cat with a high flow one?

iluvmy3rdgen, I will take note of the Y pipe you mentioned and have them checked. Thank you.

dgeesaman

iTrader: (7)

If you're going to remove the main cat, just borrow/buy another used one - when it's removed, the old one will probably drop gunk out the pipe when shaken if it's bad.

If you would prefer to fix it with aftermarket, then I recommend running a highflow cat instead. Midpipes stink, are loud, don't pass emissions, and require other mods.

Dave

iluvmy3rdgen

Double post.

iluvmy3rdgen

Please don't even think about trying to boost with no cat on. That will cause you a whole other problem. With that much free flowing exhuast you will pop your mootr if it's not tuned for it. Just try and get a hold of a stock cat or gut your stock one if it's clogged. I have a stock one for sale if you're interested, pm me.

dgeesaman

iTrader: (7)

Gutted stock cat = no cat.

Dave

7THSIGN

ok, I will ask my shop to check my cat. If they find that it is restrickting the motor then I will have them replace it with a high flow cat. So I should be looking for gunk to fall when removing it?

7THSIGN

The car also has 65,000 miles on it and was never modded until we bought it and added the exhaust and dp. If this information helps?

iluvmy3rdgen

Gutted cat = midpipe.
Midpipe = better chance then open exhuast.

Mahjik

iTrader: (1)

Yes and no. Standard aftermarket midpipes for the FD are 3". The stock exhaust even with a gutted cat is not 3". So, there still is restriction there even with a gutted stock cat.

7THSIGN

Well, I contacted the shop, they said that it cant be the Y pipe because if something was wrong with that, I would not be getting boost on 1st turbo.

I then told them about the cat in the mid pipe being clogged and he said it wouldn't just effect 2nd turbo.

So basically he still thinks that its the 2nd turbo pressure wheel, or the turbo its self.

Now what do you guys think about that? They say its one of the best shops in my area. Is he right?

AgentUnkind

I would be leary of a shop telling you if something is messed up past the actuator flap on the secondary side you would be getting no boost at all, because below 4500rpm that flap stays closed and you get 10psi boost from the primary. Also too, a clogged cat will cause a drop off in boost from the secondary as RPM's increase, so again they seem to not know what they're talking about. Have you tried doing any of these tests yourself or just they shop?

Alex