Exhaust leak sound and lean condition under boost

1932 Views 10 Replies 4 Participants Last post by drtalon123, Oct 16, 2020

Turboshitbox

Discussion Starter · May 11, 2020

I apologize if this has been covered before but I haven’t seen anyone with the same problem.

I have a mini me turbo setup. D16y5 block with y8 head. Stock internals with ARP headstuds boosting 12psi. Car is also dyno tuned and has a p28 with hondata s300. So the car has been fine for the past few months after the tune until recently I started hearing a ticking/exhaust leak sound and it runs lean under WOT. It usually sits at 11-12 afr under boost but now climbs from 12-14 quickly and I let off immediately. I checked valve lash and it they were all still set to 0.8 and 0.10. I have new gasket from turbo manifold to downpipe. Running open dp. Timing is on point. I asked my tuner he suggested I check the adj. cam gear to see if it slipped but it didn’t. Spark plugs are brand new bkr7e 0.28 gap and injectors are Acura RDX 410cc. No misfires or anything weird other than the exhaust leak sound. Any ideas? dizzy isn’t leaking oil and looks good. Coil wires are also brand new. Wanted to see what you guys think before I go ahead and replace injectors and what not. Oh and I also have a walbro 255 fuel pump. I appreciate any input. Thanks guys

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drtalon123

· #2 · May 11, 2020 (Edited)

Its your exhaust leak more than likely. If it still sounds like its leaking, you need to fix it.

Wideband oxygen sensors sense "oxygen", a leaking exhaust upstream from the wideband sensor will draw fresh air into the exhaust stream, and skew your AFR readings.

If the car was fine till the exhaust started leaking, and still feels fine, then the tune is probably still fine, and the exhaust leak is drawing in pre-sensor oxygen giving you a false lean indication.

Find the leak, and fix.

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Turboshitbox

Discussion Starter · #3 · May 12, 2020

Thanks for the input. That’s what I was thinking and been trying to find the leak but no luck. But even when I had a blown turbo gasket my AFR held solid so that’s why I wasn’t too sure it would be an exhaust leak but I may go and get the turbo manifold resurfaced to make sure that’s not the issue

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drtalon123

· #4 · May 12, 2020 (Edited)

If you bring it to a reputable shop, you can tell them to smoke test the exhaust for leaks.

EVAP leak testing machines pump out a thick white smoke under a small amount of shop air pressure, and they can pump it into the exhaust tail pipe opening while on a lift, and watch for where the pipe or fittings might be leaking from.

What kind of manifold do you run? Is it a cheap ebay ram horn stainless manifold? Those things are known to crack at the collector flanges all the time. Welding them back up doesn't work, and will crack again in a few weeks.

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Turboshitbox

Discussion Starter · #5 · May 12, 2020

I have a go autoworks log style manifold I suspected a crack too and took it off to check but couldn’t visually see any cracks or damage but I’ll probably look for a shop that can smoke test it

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transzex

· #6 · May 12, 2020

Have you thought about asking Greg @GO-AUTOWORKS since it is his product?

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Turboshitbox

Discussion Starter · #7 · Oct 16, 2020

A bit late but I figured I’d give any future viewers an update and conclusion. After trying a new turbo manifold and y8 head I still had the same issue so I compression tested it cylinders 2-4 were at 155-160psi and cylinder 1 90psi. I pulled the motor and got it all disassembled this past weekend and here’s what I found...

Ringlands completely broke off when I pulled the piston out. Bearings were also pretty shot so I’m happy I pulled the motor when I did. Other than that everything else looked fine. Thanks for everyone’s input and suggestions much appreciated

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drtalon123

· #8 · Oct 16, 2020 (Edited)

Edit... reread your OP, yup those are stock rods and pistons lol.

So not an exhaust leak, was a misfire! That'll do it! You'll remember this forever... always do a compression test if you have odd drivability issues, takes 5 mins and lets you know a fuck ton about the health of the cylinder sealing components.

Time for pistons and rods! You gonna rebuild it?

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Turboshitbox

Discussion Starter · #9 · Oct 16, 2020

Yes definitely. Didn’t have the best luck finding a compression tester. I got a brand new one that was faulty so I ordered one and while I waited I did what I could to eliminate possibilities. But yes I’m planning a forged bottom end build I picked up a z6 block from a friend so I’ll be using that to build. Planning on leaving the head stock (for now) for simplicity and since I have a fresh y8 head laying around ill probably get that built in the future if need be but my goals aren’t very high shooting for 300-350hp range since we don’t have e85 here in Hawaii I don’t want to push the car too much.

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