2.5" exhaust ? surely that will do ?
252deg duration cams?
GT2540R .86 hotside full boost 4k.
7.9:1 C/r
no AFR problems
no det problems.
mechanically sound engine
mapped

.

 

What boost?

Whos mapping it?

 

on stadard internals and head dimensions?

 

1.2bar held. no fluctuation. mapper is not the prob.

 

well that don't matter but its built to take it.

 

Your air pump is simply too small if the mapping is ok, so start looking at airflow restrictions...

 

400bhp @ 1.2 bar?

I would have said that's a little too much to expect!

Also, I wouldn't have said that the torque diving like that is anything out of the ordinary.

Does the dyno its on give a boost plot?

 

1.2 bar?!?! I wouldn't imagine mine makes 400bhp at that and I have a much bigger Turbo! and a better engine

 

no no no, it won't make anymore power above 1.2bar. it does make more boost if we set it to.the boost is virtually at flat line of 1.2bar to redline after 4k

 

Bit low. What makes you expect such low boost?

 

Your never gonna get 400bhp on that turbo at 1.2bar. On that turbo its a 2bar+ job really unless got mega lairly cams etc and a lot of luck.

2.5in exhaust isnt brilliant.

Rest of spec seems ok.

Cam timing?

 

Head not up to the job of flowing enough air then?

 

i don't expect such low boost , that is the level of boost that it stopped making anymore power. i.e @ 1.4bar 1.5bar it did not make more power!
all parameters where optimal , act,egt,timing,afr etc etc

 

NO. i know that! it what i'm saying is it won't make anymore power with more boost ( we tried it )

 

I think the exhaust needs looking at as well! Measure the back pressure, I bet it's the same as the boost pressure .

 

Then surely it has to do with the flow of air and how much the engine can or cant comsume. I'd say head work or cams is the problem then

 

600bhp proven flown thru this head

 

preturbo or after and how far after? 1 inch 1 foot 1 metre ?

 

Exhaust then...

Or are you SURE the cams are correct and timed right? Its not unheard of to get wrongly ground cams even brand new.

 

But backpressure can be 3times boost pressure and still be making good power.

Its not an ideal situation, but be suprised if a 2.5in is holding him back THAT much.

How far away from 400bhp are you now? Still at 336bhp yeah?

Ok, maybe it is the exhaust, didnt realise youd got that high already.

 

If head has been proven to flow the corect volume of air for 600 bhp, then that surely only leaves the cam choice and cam setup or as Mike R has suggested, exhaust back pressure and therefore heat

 

Its a vauxhall - Nuff said

 

315bhp! it made 336bhp with higher C/r on the same exhaust,head,turbo etc etc

 

well thats very helpful however there is as much aftermarket stuff in this engine/setup as most of you use/rate/want !

 

You tried asking Chip? could be your man

 

has the baffle fallen appar in the exhaust?

 

As i mentioned on vauxsport mate, it would be good to see the fuelling and timing maps.

IF its failing to flow the air anymore, it should be very obvious from a big drop in injector duty per cycle.


It certainly seems like a flow issue though of some sort, have you tried measuring the boost pressure just after the turbo and at the manifold and seeing what sort of drop you get through your IC and pipework etc?

 

might run it with the exhaust off at the cat replacement?
be noisy but atleast i can rule that out for undoing 3 bolts and a quick power run?

 

goes to download maps, bugger could of pulled off the data log after the power run

 

worth a go lee

 

If lots of extra boost pressure fails to yield any extra power then you have most probably either:

1) Reached the TIP max.
The head cant flow anymore volume due to turbine housing/manifold.

2) Hit a huge flow restriction in teh exhaust.
The turbine cant flow any more volume due to backpressure in exhaust.

P.S: Both the above will normally show unusually high EGT's.

3) Hit a flow restriction in the inlet/head
Not easy to measure in absolute terms on a speed density system. Try measuring TIP and turn teh boost up to see if it raises.

4) You have run off the compressor map and into excessive compressor heating.
Have you measured the Air temps at the inlet when Mapping?

4) Camshaft misstiming is causing a massive drop in VE.
What are teh cams dialled in at? Is it laggier than expected?

One of the above will very likely be your problem.

 

fuel.

.
ign.

compensation

 

why is it when i post pics sometimes they look compressed, then when i come back to look sometimes there ok?

 

Also, the turbo, it could be mismatched spec. This is quite common.

For example, we have just changed the exhaust housing on a turbo we were running on something to the next size down and made 30bhp more!

There is alot to turbo-spec'ing and mistakes are often made.

 

we'll were all learning just i'm the guinea pig

 

Indeed, the problem is that the compressor map only shows a portion of the story, it doesnt show the potential for a huge drop in VE due to a hotside thats too small!

 

just realised them maps don't mean jack wothout the boost compensation info sorry chaps
now added

 

stu its a large hotside!

 

Lee, the inlet manifold is anothe suspect.

Have you given any thought to replacing it?

 

correct my theory if you will. turbo's were essential invented to over come the restriction in the inlet tract/valves etc by forcing air past?
now i'm sure i'm correct by thinking that for more volume past a fixed size hole more pressure is required. hence turbo's. i realise i can run less boost but the same volume of air if the flow hole/tract in increased by size/flow characteristics. but hasn't this manifold already flowed enough volume at under 2 bar to give 400bhp over in sweden etc ?