turbo noise ??
 

So I get a dremel like sound at wot right after the changover. You can clearly hear it all the way through 3rd gear. Based on what Ive read here, and the mileage on them (77k), I'm pretty sure my turbos are on the way out. My only question is this: why dont I hear this sound in 4th and 5th gear at wot? I dont hear it at all until after the changover, so Im assuming its the secondary thats on its last leg. I would also assume that at 70mph in 5th gear (wot) I should hear the same sound, but I dont. what gives??


my only engine/turbo mods are a downpipe, and sbc id boost controller.

John

bump

not familiar with the sequential system but if you only hear it at change-over that's a place to start. if it's a dremel like sound i would suspect a turbo.

What about reliability mods? you don't have the plastic ast do you?

Edit- those last two questions were completely unrelated to your question, except that you mentioned "only mods".

I have exactly the same issue.
I am sure that is the second turbo issue because I have change the manifold with 1 turbo charger and all the solenoids and still I have the same problem.

These symptoms are puzzling.

1) the secondary turbo is spinning well before 4500 - I think it's spinning all the way from 3000 in a prespool stage in some cases. The point is that if the noise was from the secondary spinning, I would expect it to happen earlier, and in 4th and 5th too. BUT, if you're only testing 4th and 5th at 70mph, your rpms are only 3000-4000rpm - you can find a clear safe road and do a higher speed pull in 4th to see what happens above 4500, and also do 2nd gear pull.

2) to verify the turbo, I would look at two things: first remove the rear turbo inlet pipe. Then peek up there (it helps if the downpipe is pulled) and see if the compressor blades can/do touch the walls of the compressor housing. Be gentle with it though - the seals can be damaged by rough handling. Second, I would pull the pipe leading to the bottom of the intercooler and look for pooled oil. If your turbo seals are that bad to scrape the housing, I would expect to see a lot of oil blow-by.

3) There are many other things that could get in the airflow and make a buzzing sound - a loose manifold connection, etc. Make sure everything in the intake piping is connected securely and not leaking.

Dave