nicad2

iTrader: (3)

I got me my stock turbos torn apart and found the ubiquitous manifold cracks. As I understand it here are the effects of these common cracks

1) Primary Turbo Wastegate - Wastegate is always somewhat open. This may slow initial spoolup on the primary.

2) Secondary Precontrol - Precontrol is always somewhat open. During low-speed conditions ( < 3K rpm ) some exhaust pressure is "lost" to secondary turbo. This would also slow initial spoolup on the primary.

There don't appear to be any negative effects on heavy load performance (> 3K rpm).

Do you agree?

Here are a couple of pictures.
Primary Turbo - Wastegate Cracks


Secondary Tubo - Precontrol Cracks

CantGoStraight

The waste gate is for both turbos, the pre control is to seal off the primary from the secondary. If your waste gate leaks, then both turbo's lose boost. If the precontrol is leaking then you lose primary boost build (can take longer to reach 10 psi) the second picture of your precontrol is bad (mine has a crack in the web large enough to put a niclkel in and builds only to 7 0r 8 psi before the secondary comes on) but will build to 14.5 psi without any problem my waste gate (1st picture) needs to be ported. Hope this helps with your question. Jack

dgeesaman

iTrader: (7)

Look at the area around the doors that seals against the manifold. If there are markings on the doors suggesting *major* leakage, perhaps it is having an effect. But I don't see that based on what I can inspect in the pictures. While some of those cracks seem large, none of them seem to be causing blowby or exhaust leaks. I'd keep on truckin with them.

Dave

bajaman

Jebus H. Christmas! Those are some BIG *** CRACKS! That damned manifold looks ATE UP!

And I thought the cracks in MY manifold on the stock turbos with 93K on them were bad:

nicad2

iTrader: (3)

I agree that the wastegate will effect the secondary, but I don't think the precontrol seals off the primary from the secondary. I think you mean the charge control valve, that is in the y-pipe. The precontrol is used for pre-spooling the secondary between 3000-4500 rpm.

Here is a summary.

0-3000 rpm
- Primary spools more slowly due to wastegate and precontrol leakage
3000-45000 prm
- Primary spools more slowly due to wastegate leakage
- Secondary has no effect since it just spools earlier due to precontrol leakage
4500-redline rpm
- No effect for primary and secondary since the wastegate should be partially open anyhow to limit boost to 10psi.
- Precontrol leaks don't hurt anything since it is fully open anyhow.