Im having some trouble with a 'whistleing' noise coming from the engine when the turbos appear to be boosting.
However i got a Blitz digital boost gauge thats reading a peak of 0.81 bar (around 10 psi) But the 1st turbo isnt boosting quite this high. i was wondering is it still possible for a boost leak to occur, and still register the appropriate boost (been 10psi) ?

 

Yes it's possible. The pressure may be 12 psi at the turbo compressor but only 10 psi at the boost source for your gauge if there is a leak somewhere between. You might just be hearing the sound of the turbos spooling. I noticed the spooling sound get much louder when I added an open intake to my car.

 

Im running 1 large intake supplying both turbos, but the 1st turbo (when noise begins) only appears to boost to around 6-8 psi at most :/

 

littlemilla3 - Is what you're saying really true? It doesn't seem logical to me, but I'm just thinking out loud here. Let's say theoretically you're measuring boost just after the turbo. If you had a leak anywhere after that, wouldn't the boost from turbo to the leak be all the same ... equal to the max boost capable due to the leak?

I have a similar issue as Xcite24 ... maybe the same. Mine (over)boosts like a **** (as per the gage, and I'm trying to fix that), but sounds like its leaking boost big time (from 2 psi and greater) from about 2,500 to I'm not sure what rpm. I get a bit busy driving and loose track. Since this is a project car, I'm not driving it daily. Its not registered or insured so I can't easily just go check this.

I think what I was told was that what I may be hearing is the 2nd turbo pre-spooling and dumping it's pre-spool boost into the airbox. But I wouldn't suspect it would sound just like a boost leak.

- JyRO

 

Xcite, it sounds like your primary isn't boosting like it should. You need to look at your boost below 4500, and above 4500. Below 4500 is your primary only, and if one of the valves that isolates the secondary isn't shutting all the way, you will see lower boost under 4500 and full boost above. The stuff to check is the Charge Relief Valve, Charge Control Valve. You can find details in the FAQ under turbo troubleshooting.

Dave

 

Hey thanks for the info, im not sure exactly were to find the appropriate vlaves, But i know that the 'whistleing' noise starts on the 1st turbo for sure. around 3000 rpm, (@ 0.4 bar 5psi)
And continues all the time through to the second turbo.

Does the primary turbo continue to be used when the secondary comes into play.. or does it phase out ?

If it doesnt and continues to boost this copuld be the 1 im having the problem with.

 

It keeps truckin. Two turbos flow more than 1, so that's the idea behind having the secondary join in when the flow requirements get big (>4500).

Yep, I think the noise is evidence. Try having a helper boost it in neutral (you gotta peg the throttle, but you can get a few psi) and follow the sound.

Check out this site:
http://www.autosportracetech.com/RX-7/rx7stuff.htm

Dave

 

Hey thanks dave, that website is really helpful for me finding what i need to look for

Now i tried doing a neutral boost, only prob was it didnt appear to be gaining enough boost to cause the whistleing noise. the noise only seems to appear until around 0.4 bar, around 6 psi :/

Although ill retry again in the mosrning hoping to trace it back then using the diagrams to trace through the pipeworks. Although im fairly confiden **** the primary turbo with the leak as it does not seem to have any pulling power either under 1st turbo. (plus noise appearing around 3000 rpm

 

Right i done a 3rd gear pull, and the whistling noise comes on around 3000 RPM And the boost seems to hold steady around 9psi (sometimes 10) When it switches it dips to around 6 psi, then 2nd turbo comes in and it only boosts to 0.4 bar (around 5.5 psi) and wont really go any higher.
Iv tried doing the neutral boost, but failing with the turbos not boosting enough for the whistleing to start.

 

Definetly sounds like a vac leak. Your first turbo seems to be working fine(9-10 psi) but the leak appears in the transition(should be 8ish) and secondary(should be 10).

 

What about the whistleing noise im experiancing on the 1st turbo (around 300 rpm) @ 5 psi onwards. i dont think its the actual turbos spooling up, as the noise appears too loud.