LS3 top end swap

[mikeyb1987]

jonnM said:

Sounds great

So what does 25% extra power feel like

Fantastic! The power builds to the redline- it's an absolute joy letting it rev out Acceleration-wise, the car feels like it's lost half a tonne in weight- gaining speed is effortless.

[jonnM]

mikeyb1987 said:

jonnM said:

Sounds great

So what does 25% extra power feel like

Fantastic! The power builds to the redline- it's an absolute joy letting it rev out Acceleration-wise, the car feels like it's lost half a tonne in weight- gaining speed is effortless.

Result! And the most important question....has it improved the lift-off pop & crackle?

[mikeyb1987]

jonnM said:

Result! And the most important question....has it improved the lift-off pop & crackle?

It still pops and bangs like a good'un! In fact, there's (what sounds like) an occasional large explosion coming from the tailpipes when doing a full-bore shift.

You wouldn't have as many questions if you fitted a cam to yours.....

[Gelf VXR]

mikeyb1987, did you get a MOT done yet? What were your emissions like?

[mikeyb1987]

Gelf VXR said:

mikeyb1987, did you get a MOT done yet? What were your emissions like?

Hi Andrew. I haven't had a chance to get to an MOT centre. There's a few issues with the map, which I'm hoping to resolve next week. Once these have been rectified, I'll get the emissions checked.

[bimbleuk]

Good luck with getting it spot on in a couple of visits!

The driveability side ideally needs time, logs and varied conditions to get a good idea of what your combo likes. You've radically changed the characteristics of your engines airflow and then chuck in a cam with overlap which messes with the sensor readings around and just off idle.

All fixable within reason of course. For example your pops and bangs will most likely be a combo of the injector timing, fuel dynamics and DFCO tables needing some tweaks.

If I can have a perfectly driveable car without the MAP (installed for reference only), MAF, IAC sensors then rest assured you'll get there.

By the way I'm still working on my fuel dynamics but I have some major changes to the whole inlet geometry to contend with.

Edited by bimbleuk on Thursday 15th May 12:55

[mikeyb1987]

bimbleuk said:

Good luck with getting it spot on in a couple of visits!

The driveability side ideally needs time, logs and varied conditions to get a good idea of what your combo likes. You've radically changed the characteristics of your engines airflow and then chuck in a cam with overlap which messes with the sensor readings around and just off idle.

All fixable within reason of course. For example your pops and bangs will most likely be a combo of the injector timing, fuel dynamics and DFCO tables needing some tweaks.

If I can have a perfectly driveable car without the MAP (installed for reference only), MAF, IAC sensors then rest assured you'll get there.

By the way I'm still working on my fuel dynamics but I have some major changes to the whole inlet geometry to contend with.

Edited by bimbleuk on Thursday 15th May 12:55

Some good valid points I'm past a couple of visits now, but I'm dropping the car off so he can have it for almost a week, so hopefully most issues will be 'mostly' ironed out.

I now know it's a long process to perfect and hone the map- had I have known that from the outset, I would've looked at getting my own copy of the software etc to log and tweak.

[ringram]

Yeah that's the way a few guys have gone.
Get a baseline in and a bit of a lesson in use and off you go.

I almost guarantee it wont be 100% to what you want given the OEM tune isn't either. Its just most people don't know any different.
Once you know things arnt perfect its hard to avoid messing with it.

[eliot]

ringram said:

Maf always restricts thats what it does. 85mm vs 90mm with an obstruction in the airflow to measure the airflow.

The question is more like how much of a restriction is it!?

That answer is for the dyno, which is exactly what they are there for. So Id retune mafless and redyno, that will tell you by how much it was/is.

Removing and retuning and claiming a gain isnt a valid test. To be a fair comparison you should the refit the maf again (but disconnected) and do a back to back dyno run.

[SturdyHSV]

eliot said:

Removing and retuning and claiming a gain isnt a valid test. To be a fair comparison you should the refit the maf again (but disconnected) and do a back to back dyno run.

I will endeavour to do this at some point, I'll keep hold of my MAF and associated tubing instead of chucking it in the bin like everyone else recommends

[ringram]

In addition to any actual physical restriction there is also the question of loss of acuity at the asymptotes of the response curve.

This means at low RPM and high RPM the maf does not as accurately report airflow effectively limiting its use in high BHP applications
Hence why OEM use mafless at lower rpm ramping in MAF until it takes over around 4000rpm

Then there is the fact it does not understand reversion. Air can flow both in and out of the engine, especially with larger cams.
The Maf see's all of these flows as flows into the engine. It is dumb as to the actual direction.

Finally all ECUs up to around 2008 had a hard limit of 512g/sec airflow which equates to about 450rwhp IIRC
After this the ECU sees no change in airflow irrespective of what Hz it sees from the Maf.

Therefore that is why all GM LS tuners recommend mafless for proper high BHP operation.
Newer ECU's and larger Mafs overcome some, but not all these issues.

[SturdyHSV]

Rich, I'll need a custom OS to keep adaptive spark without the MAF I presume? Is there one for the E40? I presume once the new OS is on there, everything else is still basically the same?

[ringram]

Take a look at the OS Patches section at the bottom of the tune.
I think you get adaptive spark just by patching the OS. Click the button, then full flash.
Amen

There is also a 2bar custom OS available.

[SturdyHSV]

ringram said:

I think you get adaptive spark just by patching the OS. Click the button, then full flash.

I shall apply that patch then, cool

[eliot]

SturdyHSV said:

eliot said:

Removing and retuning and claiming a gain isnt a valid test. To be a fair comparison you should the refit the maf again (but disconnected) and do a back to back dyno run.

I will endeavour to do this at some point, I'll keep hold of my MAF and associated tubing instead of chucking it in the bin like everyone else recommends

I'm not convinced that removing the maf makes that much difference - so if you are able to compare as described it would be an interesting result. My guess would be ~5-8 bhp on a 400bhp engine.

[SturdyHSV]

eliot said:

I'm not convinced that removing the maf makes that much difference - so if you are able to compare as described it would be an interesting result. My guess would be ~5-8 bhp on a 400bhp engine.

I can't promise it'll be soon as no idea when it'll be on a dyno next, but I'll make an effort to try it out.

It'll still be hard to be scientific though, ideally you'd want the runs as close to back to back as possible for minimal atmospheric variations, but then which one do you do first, as the temperature of the engine will vary between runs too

Should be interesting either way

[eliot]

You could argue that if the difference is within or masked by the variation between two runs on the same dyno on the same day, the the gain/loss isnt worth worrying about.

[Gelf VXR]

I just got my cam data from FTI for a custom cam after submitting their cam spec form, my criteria was for a daily driver, UK emmisions compliant, no loss of bottom end, maximum torque under the curve, and to pull to 6400rpm. Purchase is required before you can receive the spec.

Taking into consideration I would be swapping in LS3 hollow valves, increase compression slightly from .051 stock head gasket to .040 cometic gaskets,retaining 1.85:1 rockers. I also have a modified RC LS3 intake with runner bars + ¬8CFM

I wasn't too surprised to see the spec hardly changed from the SLP cam I already have installed

Installed SLP cam 216/229 113+3 .330/.331

Custom FTI cam 219/229 113+4 .340/.342 (.629/.633)


I was thinking maybe upto 223/231, but looking online 219/223 (LS3 valves) or 219/227 (L92 valves)is popular small cam now

http://www.g8board.com/forums/showthread.php?t=837...

http://www.gmhightechperformance.com/tech/lsx_engi...



Unfortunately im still out of the country working, itll be some time before i can get in installed

[ringram]

I dont think there will be any point changing cams mate.
That is so close there is no point as its within normal cam variation. IMO you should use the spend on something else.

Im going with a 222/230-112 LSA - 112 ICL for my pending LS3 (was thinking of a 114, but after the Big Meet I realise cam overlap is good)

Only a tiny bit larger. But then the engine is ~3% larger than the LS2 anyway.

[SturdyHSV]

ringram said:

I dont think there will be any point changing cams mate.
That is so close there is no point as its within normal cam variation. IMO you should use the spend on something else.

Im going with a 222/230-112 LSA - 112 ICL for my pending LS3 (was thinking of a 114, but after the Big Meet I realise cam overlap is good)

Only a tiny bit larger. But then the engine is ~3% larger than the LS2 anyway.

I look forward to hearing that