zenofspeed

iTrader: (1)

Hey guys. New problem

Car: gotham stage 2 port. 3mm seals. stock twins (ported WG). power fc. greddy ic. at 10psi = 265rwhp. etc. etc.

The car has an audible whooshing sound (like air escaping) from 1k to 4.5k rpm. At 4.5krpm it audibly seals and the sound stops and power increases dramatically (passengers pressed into seats).

Along with the new sound, I've lost the oomph I had below 4.5k rpm. Sounds like boost leak right?

It is not the BOV, I adjusted it tighter and the sound/perfromance remained IDENTICAL even with the BOV so tight is was barely venting. It is not the IC piping. I've checked all the IC piping and couplers and put on better couplers/clamps (Greddy's suck).

So My question is - Given the above info, where should I look for the leak?

Also, why would it stop at higher RPM and stop leaking? Is there a path that the boost flows during single turbo use and then is diverted after the other turbo kicks in? (sorry I'm noob :P)

Thanks!

shipdriver

iTrader: (1)

What is the PowerFC reading for boost, or if you have a boost gauge, what is it reading?

Mahjik

iTrader: (1)

Well, at least from your description, it sounds like your CRV is vented open so you hear it until it closes at around 4500 rpms. Take a look at the system overview:

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

The CRV is venting the excess secondary boost until it closes to provide full boost at the transition. Now the question is, what is your boost pattern? Are you making boost before 4500 rpms?

zenofspeed

iTrader: (1)

The car wasn't making the noise when I got it. I do make boost before 4500 but I need to really watch my boost gauge to see what the boost is doing exactly. I'll have to watch my gague later today when I drive home.

The power delivery (before 4500rpm) is noticeably muted compared to what it used to be from before the noise started.

I asked another FD enthusiast via Pm and he said:


the twin setup. If the cold pipe for the primary turbo isn't connected you'd be seeing exactly as you described.

I'd bet you split the coupling on that turbo... I can't remember if the primary turbo is the front or rear turbo, but you'll have to dig down a little to get to that coupling. Not too bad, just not right visible on the surface.

zenofspeed

iTrader: (1)

Thanks for the link

the more stuff like that you can point me toward, the better

Mahjik

iTrader: (1)

First thing you need to figure out is what exactly is your boost pattern. 1st step in troubleshooting boost issues is the Boost Test:

http://www.fd3s.net/boost_test.html

That will help narrow down what is happening. Simply saying "I hear rushing air" isn't going to get your far.

zenofspeed

iTrader: (1)

OK. Are you looking for 4 readings such as this?

3,000 10
4,500 8 (as 2d turbo comes on)
4,500+ 10 (recovers almost immediately)
6,000+ 8 (and holds to redline)

Thanks

zenofspeed

iTrader: (1)

Ok so the CRV vents to the air cleaner, then what happens to that air? Goes to atmosphere?

Anyway I read this in that walkthrough of testing:

A SLIGHT AND SMOOTH INCREASE IN POWER SHOULD BE FELT AT 4500rpm.

my car used to feel like that. Now it's crap below 4500 and "Bam!" at 4500+.

Where can I get the needed gauges and connections for running the walkthrough you linked?

Mahjik

iTrader: (1)

Basically yes. What is the boost pattern you are seeing?

You don't have a boost/vacuum gauge? If not go here:

http://www.rx7store.net/category_s/21.htm

And pick a boost gauge. If you don't care about looks, this one will do:

http://www.rx7store.net/product_p/autometer%20boost.htm

It's cheap and gets the job done.

zenofspeed

iTrader: (1)

hah sorry. i do have a boost vaccuum gauge installed on my steering column. I don't have an external one for testing lines like it seemed to be describing in that diagnosis walk through.

Anyway, Let me try and get on a safe peice of road where I can stare at my gauge under WOT in 3rd to get those 4 readings.

Mahjik

iTrader: (1)

You need to start with the boost test. As I said, that will help narrow down where you need to start checking with the system. Otherwise, you just need to start checking everything as you have no basis to what the problem may or may not be...

zenofspeed

iTrader: (1)

OK did the test

3000rpm 7psi
4500rpm 5psi (normal dip for split second)
4500rpm+ 10psi
6000rom 10psi to redline

So there appears to be a leak before 4500rpm as it should be 10psi then too. This thread might be pointless now. I found a rotary shop and dropped it off. They are going to throw it on the dyno tomorrow and figure it out.

zenofspeed

iTrader: (1)

WELL, the shop hasn't dynoed it yet because they wanted to check with me first after what they found. They found the compression to be 75 -75-75 on the front and 80-80-80 on the back.

Not good right?

I've had the car for 2 weeks and the previous owner had the compression checked right before the sale and it read all 6 90s (gotham tested). I've been running at 10psi only and only at full operating temp. 30k miles on the motor. boo

Mahjik

iTrader: (1)

Try talking to Gotham to see when exactly the compression test was done on the car. I would also take the car to second shop for a "second opinion" on the compression test.

zenofspeed

iTrader: (1)

Yeah, I plan on doing both those things. Funny thing is, I talked to Steve Kahn the other day and forgot ask the exact date the compression was checked =/.

I dont know another local rotary shop, so I may just pay the dealer the $200 for them to do the compression check.

Mahjik

iTrader: (1)

Is it at Gotham now?

zenofspeed

iTrader: (1)

no it's at protech performance in Austin. They are the guys that built the 153hp turbo kit for hte rx8. They drive Fds and seem to know what they are doing. They put some 2stroke in it and engine cleaner in the tank, they want me to take it easy for a tank of gas to try and get the compression back up. I told them I redline it everyday and to go ahead and throw it on the dyno to see the curve.

DaveW

IMO, the low compression, although it is obviously not good, has nothing to do with the boost problem. If it starts and runs OK, it should still produce plenty of boost. There is still an unrelated (to the low compression) problem in the boost system.

Dave

zenofspeed

iTrader: (1)

I agree. I asked them to go ahead and dyno it to evaluate that problem, which is why I initially brough the car in.

I think the compression just scared them and they don't want it to pop on their dyno. If I can resolve the boost leak, I'm just gonna drive it how I always do until the compression issue makes it not run anymore. Then rebuild.

zenofspeed

iTrader: (1)

Dyno done.

290whp at roughly 10psi and 7500rpm. Good flat torque curve that peaks at 260. 11.5 A/f straight across. 96% injector duty cycle at redline (stock fuel)

They couldn't find any leaks, but said the turbos "may be on their way out". The primary is not reaching full boost and the above dyno was acheived at 12 psi settings. Maybe it is normal, but they aren't holding full boost to redline.

so the boost looked like this:
7-8 psi < 4500rpm
6psi @ 4500rpm
12 psi 4500-6800rpm
10 psi 6800-8000rpm

The power delivery used to "feel" smooth, but from that pattern, it seems clear why it wouldn't feel smooth anymore (8 to 12psi transition)

Anyone have insights? the shop stated that the motor (although having low compression) seems to run strong, but the stock twins may slowly go out over time as they age. I think they have at least 33k on them since a rebuild at 60k. So 93k total lifetime.

*ponders which single to get*