Big Turbo Problem Emails

----- Original Message -----

From: John Clark
To: GK; JY
Cc: ""
Sent: Tuesday, August 31, 2004 3:46 PM
Subject: Re: Urgent GT28RS questions


I've come across a major hurdle with the new turbos! as you'll see below there were some initial teething troubles with the installation (alignment of housings, exhaust flange etc.) - but I took the old T25s off last night and there's not enough room!

I had thought that the passenger (nearside) turbo would be the one to check for clearance, as the compressor outlet is inboard - very close to the block... actually the 1st problem encountered was that the GT28RS has smaller holes drilled on the exhaust manifold flange (inlet) than the T25s - so the studs would not fit through the GT28RS flange - minor issue - these can be drilled, with suitable care etc. Anyway, offered the new turbo up to the flange to check clearance: compressor outlet looks tight to the block, but possible fit, maybe with a silicon 90 degree elbow (the original aluminium elbow that was welded onto the fabricated chargecooler piping looks a bit restrictive anyway - I did have a fall back plan for more room - more of that in a min....

Thought I'd just check the other side (take the turbo off for GK etc.) - wasn't so concerned about this bank, as the compressor outlet faces away from the block (it's the compressor that's significantly larger on the GT28RS, as with the .64 A/R turbine variant that I went to all the trouble to get, the exhaust housing is not that much bigger).

HOWEVER - the 5 stud turbine/wastegate outlet of the GT28RS is wider and fouls the gearbox casing! - OH DEAR.

So - my fall back - I'm thinking that the exhaust manifolds can be retained but more clearance allowed, if some spacers can be made up to mount between the manifolds and the heads, using longer studs and two gaskets?... Not sure exactly what width spacers would need to be, but if I get the turbos flange holes drilled and mount them to the exhaust manifolds, I can offer them up and measure - as an estimate, I 'd say only between 1 and 2 cm.

Thought I'd tell this story to see what everyone thinks and whether there's another way (I'm committed to getting these turbos to fit!) Issues with the spacer idea that I've mulled over would be what material? - how easy/expensive would they be to fabricate with matched exhaust ports? The exhaust gasket is, of course, a perfect pattern for machining a spacer though.....

Just one other thing - not having the engine in the chassis, I'm not absolutely sure how much room I've got to play with in the engine cradle - anyone help here? (I'm gonna see if there are any good photos/diagrams in the workshop manual or on the web - but if anyone's got access to a assembled car, it would help)



----- Original Message -----
From: John Clark
To: JY
Cc: GK
Sent: Friday, September 03, 2004 5:58 PM
Subject: Manifold Spacer??


Here's some annotated piccys then, explaining the idea - yeah, I agree ally would probably melt without the cooling effect of the head water galleries. This heat-soak photo shows that temperature really starts to increase a small distance from the gasket area of the manifold.

Using a laser cut sheet metal with a gasket as the pattern may be an idea then - the only thing would be the cost - If it's into the territory of having a stainless steel purpose fabricated manifolds, this would probably be nicer. I will want to have a stainless exhaust system made too - starting from the 3 inch V-band adapter on the GT28RS exhaust output, so maybe finding the right people is an idea?

Inconel has to be cast I think? and it's VERY expensive.

The first thing is to understand better how much room there is to play with within the chassis tubes though - have a look: