I decided to take a couple buddies out for a ride last night in my 87 TII. I hit a back road and spun them through first, nailed second, then when it got to about 5000 rpm, I noticed an odd metal flapping sound from the engine. It sounded like interior trim rattling or something, but it was more of a metal sound, not plastic, and it sounded like it was definately coming from the engine bay. It's making about 1 psi less than normal, nothing too different there, but just under full boost. It didn't feel as strong in top end and made definite pulses at idle. I'm almost scared to look under the hood and not see anything wrong, cuse that means it's most likely something internal. So do you guys think it's something stupid, since it's only at high rpm? Or is there something that would only make noise at around 5000 rpm? Thanks guys

 

something happened to the wastegate maybe ??

 

I hope it wasnt the D word... detonation.

 

well I've never heard anything like this before. I thought detonation wasn't too loud. Almost go unnoticed on these cars, which is why it's such a killer.... hard to tell till you've done damage. And would the wastegate cause something to make sounds like that? I can understand how that would make a little less boost, but I don't know if it would make a rattling sound like that. Thanks for the ideas guys

 

If you know it's 1psi less at full boost, you've got an aftermarket boost gauge, right?

How much vacuum is it reading at idle???



-Ted

 

it's been reading all sorts of strange vacuums at idle. Right now it's normally around 150-170 torr. It used to be 200 torr all the time at idle, but about a month ago I started getting some leaks that changed it, fixed the leaks, but it still reads ~160 torr.

 

You can hear detonation. Someone post that video of the guy that cut his wastegate hose. You can hear his car detonating inside.

 

I tried looking for the video... no luck. If someone's got it, I'd love to see it and see if it's similar to the sound I'm hearing. If it is detonating, why would it suddenly start when it didn't do it before, and what can I do to stop it? I thought I was running pretty rich, but I wonder if it's actually lean.... too bad I can't afford gauges to check.

 

I have it on my HD. I forgot about it. I don't have anywhere to post it though.

 

Hope it's ok man, turbo's are sweet but they more then complicate...................BOB YOU SOB. PRIVATE MESSAGE ME!!!!

 

maybe an apex seal went out of place.

 

true detonation (around 50% or more of the A/F mixture exploding) will sound like someone is slamming your
e-shaft with a sledge hammer 8 or 9 times a second.
light detonation will sound like a marble in a tin can.
so u will know when u are really detonating

 

Do you have a good boost gauge? What psi did it hit? Was it really cold outside? cold ambient air will cause more boost creep...