[Mk2] [Turbo] Holsett HX35 or Borg Warner S366

[bobhatton]

I don't know why people think they have to drop the compression ratio for. There are 4 or 5 3SGTE powered cars running in the TSS which run 9.5:1 compression ratio, The Celica WRC ran 10.5 so there is no need to drop compression. Modern day after market ECU's are sophisticated you can run with the higher compression and map accordingly.
If I was Asbestos I would fit a stock Rev 3 head Gasket and a GT3082 and watch it punch some numbers on the rollers.

Its all about how the engine has been designed. what boost it will run and what fuel will be used. You cannot just map for a bad designed engine and get the right power

[craig_mr2_mk1]

So are you saying running 9.5:1 compression on 99 ron fuel & upto 2bar of boost is a bad design? It's being done and reliably so can't be bad. Dropping the compression doesnt help the car drive off boost either.

[ashley]

I've heard of running 2 bar at 11:1, but I can't get my head around how it works...you'd think the ecu was retarding ignition so much that you'd literally be flushing burning charge out of the exhaust manifold...

[bobhatton]

So are you saying running 9.5:1 compression on 99 ron fuel & upto 2bar of boost is a bad design? It's being done and reliably so can't be bad. Dropping the compression doesnt help the car drive off boost either.

Yes very bad design

[bobhatton]

I've heard of running 2 bar at 11:1, but I can't get my head around how it works...you'd think the ecu was retarding ignition so much that you'd literally be flushing burning charge out of the exhaust manifold...

Yes you are right, wrong thing to do

[bobhatton]

One of the main things on an engine that is determined by the engine/cylinder head design is the ignition advance.
This should never change by more that a few degree from stock when changes are made to the engine, if it does then the changes are wrong.

An engine should be able to take ignition advance to a point when power starts to drop off and there is no detonation.

If the ignition advance is being adjusted to stop detonation then the design of the modded engine has something wrong.

Just because you have an all singing and dancing ECU this cannot make up for a badly designed engine, all it will do is allow the engine to run but it will never give the correct power and in the end you will get damage, like cracked blocks, blown head gaskets and broken pistons.

[asbestos]

Hi Bob, do you have any threads on the site to your theorys of a bad design and a good design on our engines ?, in my simplistic way i thought i was doing the right thing, as stated earlier in this thread i have never rebuilt a petrol turbo vehicle before so i researched as much as possible a lot of it done on this site the majority of cars running preplanned high boost lower the comp ratio, so with my higher compression pistons and a heaqd skim the compression would have been higher, what is the problem in using a thicker than standard head gasket to drop the comp ratio back to somewhere just below standard comp ratio,
the thread was started about my queries over a what turbo to fit, im going with Garrett GTX 35r after taking on board the comments on hear and a bit more research, I suppose the dyno will tell all,

[Chris]

GTX35 is too much for your application and goals.

I can't be fooked to get into the comp ratio debate, but for 450bhp, with only 850cc injectors, the above turbo is too big and not in it's efficient range.

3076/82 is the way you need to go.

Getting mixed reviews on the GTX too. Hang fire on that for the time being. GT series is well proven and cheaper.

[bobhatton]

Hi Bob, do you have any threads on the site to your theorys of a bad design and a good design on our engines ?, in my simplistic way i thought i was doing the right thing, as stated earlier in this thread i have never rebuilt a petrol turbo vehicle before so i researched as much as possible a lot of it done on this site the majority of cars running preplanned high boost lower the comp ratio, so with my higher compression pistons and a heaqd skim the compression would have been higher, what is the problem in using a thicker than standard head gasket to drop the comp ratio back to somewhere just below standard comp ratio,
the thread was started about my queries over a what turbo to fit, im going with Garrett GTX 35r after taking on board the comments on hear and a bit more research, I suppose the dyno will tell all,

Have a read here

http://www.turbobygarrett.com/turbobyga ... with_boost

You got the wrong compression pistons to start with but I understand what your thinking was with the thick gasket, but it may or may not help.

Your piston to head clearence should be about 0.35mm any bigger is not good, this means all builds will have the pistons out the top of the block by a small amount.

[bobhatton]

Hi Bob, do you have any threads on the site to your theorys of a bad design and a good design on our engines ?, in my simplistic way i thought i was doing the right thing, as stated earlier in this thread i have never rebuilt a petrol turbo vehicle before so i researched as much as possible a lot of it done on this site the majority of cars running preplanned high boost lower the comp ratio, so with my higher compression pistons and a heaqd skim the compression would have been higher, what is the problem in using a thicker than standard head gasket to drop the comp ratio back to somewhere just below standard comp ratio,
the thread was started about my queries over a what turbo to fit, im going with Garrett GTX 35r after taking on board the comments on hear and a bit more research, I suppose the dyno will tell all,

The information I have given is not my theory it is just standard engine design that we all used before the wrong information was spread all over the internet.

What air flow and at what pressure ratio have you worked out for your engine to give you the power the engine was designed for?
Once you know this you can look at all the compresses maps and chose the correct one to suit.
All you then need to do is decide what AR exhaust housing you want to use.

[mark239]

Those precision turbo units are some job

[Rob B]

GTX35 is too much for your application and goals.

I can't be fooked to get into the comp ratio debate, but for 450bhp, with only 850cc injectors, the above turbo is too big and not in it's efficient range.

3076/82 is the way you need to go.

GT series is well proven and cheaper.

I agree with Chris on this one, 3076r all the way.for 450hp there wont be much lag but it'l have a nice kick and top end. . What more do you want from turbo??Got one on a GT4 making a very reliable 486 at 1.6bar for last two years no problem 63ar also.

Gt35 would be too laggy for the setup imo