Weird turbo V8 valve train issues?

[Carnut1]

No turbo experience here but is it possible guides were a bit loose and passing a bit of oil produced a bit of detonation which may not have been heard but added negative torque and beat the valve job to death?

[ptuomov]

Out of curiosity, was there a resolution to this issue?

[vwchuck]

130 on the seat is not enough and you have a backpressure issue with that tiny turbine. I run this turbo on my 2.3 liter and have a 1 to 1 manifold to exhaust pressure ratio. If you over double the displacement there is no way that turbine could flow enough.

[Vincenzo]

Beaten up seats is indicative of a serious cam/spring problem which is resulting in chronic valve bounce.
Valve bounce bad enough to beat up seats invariably costs horsepower

[BILL-C]

Were all of the seats beat up, or just the exhaust?

[tonyg64]

If the boost gets back into the (ex) port it will open the valves before the cam gets to it. Causes major damage. Seen it on Subaru WRC engines.

Tony

[BILL-C]

If there is not enough ign timing, the exhaust temps will get too hot and cause exhaust valve and seat damage. I've observed 40* F egt rise per degree of excessive ign timing retard. There' alot of different ways to kill an engine!

[user-23911]

If the boost gets back into the (ex) port it will open the valves before the cam gets to it. Causes major damage. Seen it on Subaru WRC engines.

Tony

Really?

I very much doubt it.

Antilag....that's the killer on WRC type engines.

[midnightbluS10]

I'll take a guess......being single turbo on a V8, it'll have exhaust leaks. They ALWAYS do.
Maybe combine that with a turbine housing that might be a bit on the big side.

How does being a single turbo V8 correlate to having exhaust leaks? Serious question. Thanks.

[BILL-C]

Ex seat damage caused by excessive heat will typically have more pitting than expected, while seat damage caused by pounding of the valvetrain ( too many rpm for the spring) has a smoother surface finish.

[peejay]

I'll take a guess......being single turbo on a V8, it'll have exhaust leaks. They ALWAYS do.
Maybe combine that with a turbine housing that might be a bit on the big side.

How does being a single turbo V8 correlate to having exhaust leaks? Serious question. Thanks.

They don't.

I've never had an exhaust leakage issue on single turbo V6s aside from poorly designed stainless headers cracking. This is inherent to stainless headers, not to vee engines.

Design the piping with an eye to allowing things to grow with heat, with bellows pipes/flex pipes as necessary, and you won't have issues.

[user-23911]

It's all about expansion,contraction, heat cycles and the cracks that always follow.
If you use the correct materials and the correct design, they last longer but still end up leaking.
A V engine has 2 banks and needs an expansion joint between them, also an expansion joint to the turbo.

Just the same as straight 6 engines with turbos.
If you build the manifold strong so it won't crack, made with a single flange, the flange ends up warping then leaking.
The best manifolds are the factory manifolds usually made from some sort of cast iron and often made in 2 or 3 pieces with expansion joints for reliability.
The XR6T is a good example as is the Detroit 60 series diesel.


If you want to talk V6s and single turbo, there's been plenty of conversions done over the years with the 3000GT.
Not one of them has ever run reliably or properly or even well for any length or time, they all get parted out...........because they ALWAYS leak.
Even the aftermarket TT manifolds for them are known to be extremely unreliable and always crack.


A single turbo V8 is always more difficult to build with a good design due to space limitations.........which I've done myself more than once a long time ago.
The most reliable way is to use the factory cast manifolds with adaptors but again, it depends on what you're starting with.
It only takes a very small exhaust leak which you probably won't hear, you end up loosing lots of potential boost.

[ptuomov]

Small exhaust leaks only hurt power at rpms where the wastegate is fully closed, right? I'm not saying they are acceptable, just that lack of peak power is not the problem.

[user-23911]

You'll get fluctuating boost (with temp) and a lack of top end power. The torque will drop away early.

[ptuomov]

You'll get fluctuating boost (with temp) and a lack of top end power. The torque will drop away early.

Your wastegate closed at peak power? That's your biggest exhaust leak right there if it's open.