Dissapointing lag

[tomwood_uk]

Evening gents,

Finally managed to get my car mapped a couple of weeks ago at automark . Absolute nightmare tbh , 16 hour day of various tests, adjustments and then finally the mapping. Incidently can't recommend Mark enough, a true guru on these engines and supremely helpful.

However both myself and Mark were a little dissapointed with the results, and I'm gonna have to go back soon. Anyway, the main issue is that of lag. Rough spec of engine; rebuild forged balanced engine, 7a flywheel. Standard rebuilt head and cams, Wagner rs2 evo cast manifold, gtx3071 with anti surge cold side and .82 hot side, big Chinese intercooler with mainly 3" ally hardpipe on the inlet. Stock recirc dump valve, maf in stock position. 3" turbo to tailpipe exhaust with no cats , one midbox and the back box. Stock inlet manny. Turbosmart e boost street controller working fine. 0.9 bar wastegate spring. Ev14 750 injectors.

I can either run spring pressure with the boost controller off, 1.3 or 1.5 bar. The inlet system gas been pressre tested to 2 bar.

However...lag is a real issue. Very little boost below 3k , and I don't think it's making full boost until well after 4k rpm. Mark wants me to change to a smaller turbo but iv gott be honest, I thought this setup would be ideal for a street car?

Any suggestions or similar experience?

[Jamo]

I strongly disagree with the 1st paragraph but thats IMO, and those such as AndyP have been educated as such

Anyway are you sure your cam timing is correct?

Personally I believe it's because you are not using motronic to control boost and using a aftermarket controller. I've run both, the only advantage with the aftermarket was full boost at part throttle.

[UrS4boy]

Unless you (we) were to go to a variable geometry turbo, going to a turbo that is larger than stock (K24-7000) turbo and gives a better top end performance will always give you worse performance down low (lag, loss of torque, etc). This is true even when going from a stock 3B/AAN/ABY K24-7000 to an RS2 ADU K24-7200.

Sad but true. Lot of folks liked the GT 2871/KKK hybrids for almost RS2 K24-7200 levels of upper performance but better than RS2 K24-7200 lower end performance.

http://store.034motorsport.com/k26-gt2871-turbocharger-20775.html

Or.... just drop a gear and nail that 3071 sucker.

[Sonic]

As above - you've bolted on a bigger turbo with a bigger hot side which inherently has more lag than stock. It's a given.

The 7a cams will give you slightly more delay with the benefit of more top-end, but you could look at the wagner reverse inlet to help.

But, as above, shift it down a gear and nail it...

[nip]

Tom call me at the weekend or after 9 Friday night and pop over

[DJones]

I strongly disagree with the 1st paragraph but thats IMO, and those such as AndyP have been educated as such

Anyway are you sure your cam timing is correct?

Personally I believe it's because you are not using motronic to control boost and using a aftermarket controller. I've run both, the only advantage with the aftermarket was full boost at part throttle.

And me and I don't agree with any of this ^ your set up doesn't sound that dissimilar to mine.

Couple of points, did you lighten the 7a flywheel, the standard is quite a lump and you would certainly feel the extra rotational mass on pick up.

The Wagner manifold introduced more lag on mine than the standard RS2 setup, back to back tests. The wider runners of the Wagner help at the top but not air speed at the bottom.

All of the above said I think the anti surge housing will be causing you the biggest problem, in the testing I did with one it did exactly as you describe.

I to use a .82 housing and I have virtually no lag despite twin intercoolers.

I tried an anti surge housing to get around surge on my .6 housing and it was rubbish. Went back to the non anti surge housing and increased the hot side from .6 to .83 job done 490bhp virtually no lag.

My next test will be to fit both 7a cams to introduce some overlap and hence lag to see what it does at the top. But I'm building a Porsche engine at the mo... Which was 600bhp at 1.1 bar before it came out.... Oh and no lag.....

Hope it helps in some way.

Darren.

[twenty valve]

you need to get dmitri to map your car with stock motronic ecu. that is all

[tomwood_uk]

I strongly disagree with the 1st paragraph but thats IMO, and those such as AndyP have been educated as such

Anyway are you sure your cam timing is correct?

Personally I believe it's because you are not using motronic to control boost and using a aftermarket controller. I've run both, the only advantage with the aftermarket was full boost at part throttle.

You mean you disagree with using Automark? I don't follow.

I have thought of cam timing, but it was obviously checked and checked again when the engine was on the stand, purely for piece of mind I will confirm.

Its not the boost controller as I initially ran the setup on the N75, made no difference to lag. With the controller turned off using just the w/g spring the lag is still the same.

[tomwood_uk]

As above - you've bolted on a bigger turbo with a bigger hot side which inherently has more lag than stock. It's a given.

The 7a cams will give you slightly more delay with the benefit of more top-end, but you could look at the wagner reverse inlet to help.

But, as above, shift it down a gear and nail it...

I know mate, just a bit disappointing as I thought I'd chosen the best compromise with the GTX version. Been spending too much time in my mates R33 GTR I think

[tomwood_uk]

Tom call me at the weekend or after 9 Friday night and pop over

PM me your number again nip, new phone. If I don't go Edition 38 I'll pop over

[tomwood_uk]

And me and I don't agree with any of this ^ your set up doesn't sound that dissimilar to mine.

Couple of points, did you lighten the 7a flywheel, the standard is quite a lump and you would certainly feel the extra rotational mass on pick up.

The Wagner manifold introduced more lag on mine than the standard RS2 setup, back to back tests. The wider runners of the Wagner help at the top but not air speed at the bottom.

All of the above said I think the anti surge housing will be causing you the biggest problem, in the testing I did with one it did exactly as you describe.

I to use a .82 housing and I have virtually no lag despite twin intercoolers.

I tried an anti surge housing to get around surge on my .6 housing and it was rubbish. Went back to the non anti surge housing and increased the hot side from .6 to .83 job done 490bhp virtually no lag.

My next test will be to fit both 7a cams to introduce some overlap and hence lag to see what it does at the top. But I'm building a Porsche engine at the mo... Which was 600bhp at 1.1 bar before it came out.... Oh and no lag.....

Hope it helps in some way.

Darren.

Cheers Darren, very helpful.

No mate didn't have the flywheel lightened just balanced. Did change from a dual mass though so a decent reduction in weight straight away.

Yea this anti surge housing has been bugging me a little aswell.

The top end performance is very good, and with a few more tweeks and a little more boost im sure it will make the performance figures I'm after. The reason Mark is concerned with the lag is that he knows how well yours performs! Your cars sounds a bit of an animal

[Error404]

Without knowing mush about the technical aspects of it, surely the anti-surge housing just makes the compressor less efficient = slower spool / boost response?

[tomwood_uk]

Without knowing mush about the technical aspects of it, surely the anti-surge housing just makes the compressor less efficient = slower spool / boost response?

It would appear so mate, just doing some research now.

[DJones]

Without knowing mush about the technical aspects of it, surely the anti-surge housing just makes the compressor less efficient = slower spool / boost response?

Alex, spot on.

Darren.

[tomwood_uk]

I'm trying to find out if you can replace the anti surge housing on a GTX with a standard item.