Stalling issue

[Corey]

Never being one to proclaim that I know it all, got a very weird stalling issue on a 3B.
The spec of the car is
stock turbo
stock exhaust manifold
7A ex cam
3" turbo back exhaust, single box
Lightweight flywheel 3B stock that has been machined
Clutchnet clutch
RS2 intercooler
remapped to 1.2Bar

The car shows no faults
New ISV
New MAF
New PCV system
Samco's in place
New small bore vacuum silicon hose

All systems checked and work as they should (TPS, throttle position etc)

The car drives perfectly and does everything as she should except when above 4.5-5k rpm and come off the throttle and allow it to go back to idle it stalls.
I suspect it is the flywheel effect, that when the throttle is closed the mass of air gets dumped back to before the turbo by the DV creating turbulence near the MAF, which in turn sucks air through it creating a high voltage which tells the ecu to put fuel into the engine (can see it on the lambda signal).
The engine speed drops to quickly for it to recover from the extra fuel.
Below 4.5k rpm the car behaves perfectly. You can recreate this when the car is stationary or when driving, it doesn't matter it still does it.
I suspect the flywheel is causing the issue but it doesn't really sit right in my mind as I have used lighter flywheels with this specification of car.
Spent an awful lot of time talking to Mark at Automark (he mapped this for us) and he has only seen this phenomenon 3 times before but they were on race engines and they weren't asked to idle after high rpm so the fault wasn't persued, at the moment there is no known cure.

So any ideas as at the moment I'm scratching my head, not many things beat me and I am not going to be beaten by this, the car is due back to me at the beginning of March where I am going to put a stock flywheel in to either prove my theory or make me

[Chris M]

Isn't this the same or simular problem Ross had with his car? I know his car didn't do it all the time tho.

What about moving the MAF to the pressure side??

Cheers,

[Corey]

Moving the MAF is something that I have discussed with the owner at great length but at this stage of the cars evolution he wishes the car to remain "stock" looking.
By moving it it would prevent this turbulent air being created by the DV doing its job and I couldn't guarentee it would cure it as all the thought as to what is causing the stall is merely a theory.
I would like to "prove" it before spending the owners money.

Both Mark and I thought it may be software related, so the most recent S2 I did a remap on
3B with RS2+ spec (same exhaust but totally stock flywheel and doesn't stall at all) we put that software in to see if it stalled (didn't drive the car as the map is wrong for this car) it did still!!!
Software isn't the cause.

Yes Ross had the same problem but something prevented that being investigated

[Chris M]

Yeah, you can say that again

Well as you know, i'm interested in the clutch/flywheel combo (if you can get me a price ) so would be more than happy to try them in my car, and its RS2 spec too. I will be running the MAF on the pressure side too, so we will see if that does or doesn't make any difference

Cheers,

[terrybullwon]

I have the same issue corey,
Is the car running a cone filter?
When this happens to me the fuel light can come on some times.....
I have also cleaned all sensors tested and check them and replaced the plugs and checked the DV.
My car is remaped but this problem came out of the blue and has nothing to do with my map.

This could make for a very interesting thread.

[Corey]

It had a Carbon CDI filter thingy but we changed that to an RS2 airbox, which made it a little bit better but didn't cure it.
One thing I was going to try was to remove the DV totally and blank the hoses to see if it still happened, it wouldn't be permanent as it would cause issues elsewhere.

[Corey]

Yeah, you can say that again

Well as you know, i'm interested in the clutch/flywheel combo (if you can get me a price ) so would be more than happy to try them in my car, and its RS2 spec too. I will be running the MAF on the pressure side too, so we will see if that does or doesn't make any difference

Cheers,

Yes I know

When we have this 3B in I am going to rig up the MAF temporarily on the pressure side to see what happens.

[Chris M]

I don't mind having to find any problems on my car, i've usually got time

TBH, i wouldn't have thought the DV would make too much of a difference Its not really running that much diffferent to mine. How much boost is it running and what DV?

I'm also running a cone filter, been looking at modding my existing 3B airbox tho.

Cheers

[Corey]

I don't mind having to find any problems on my car, i've usually got time

Always looking for willing victi... er I mean volunteers

TBH, i wouldn't have thought the DV would make too much of a difference Its not really running that much diffferent to mine. How much boost is it running and what DV?

I'm also running a cone filter, been looking at modding my existing 3B airbox tho.

Cheers

1.2Bar boost, normally I wouldn't put more than 1Bar through the K24 but with the exhaust system it just loved what we through at it.
The DV removal would be to see if the air rushing back theory could be proved, it was using a Forge 007 recirc but that has been removed at the moment as it was sticking, it has a brand new OE S3 item on.

[Jay]

you have probably tried this...

It had a Carbon CDI filter thingy but we changed that to an RS2 airbox, which made it a little bit better but didn't cure it.
One thing I was going to try was to remove the DV totally and blank the hoses to see if it still happened, it wouldn't be permanent as it would cause issues elsewhere.

I had the same problem but I was using a Bailey sport piston type dump valve, now changed to a recirc type but the return point is lower in my MAF to turbo hose than standard but I also adjusted the throttle damper (to slow throttle return) and throttle closed position/angle to allow slightly more air passed so its not as reliant on the idle control valve to catch the engine.

Not teaching you to suck eggs i see the vac hoses have been replaced including samcos but is there a boost leak, may be on the breather side of things as this will make things way to rich and the ecu can't copy at first when dropping to idle??!

Could the tunner/mapper increase the injector on position from the standard 1800 rpm to say 2400 to give it more chance of sorting it self as you say with the light fly wheel it will return to idle very quickly?

Jay

[Corey]

I had the same problem but I was using a Bailey sport piston type dump valve, now changed to a recirc type but the return point is lower in my MAF to turbo hose than standard but I also adjusted the throttle damper (to slow throttle return) and throttle closed position/angle to allow slightly more air passed so its not as reliant on the idle control valve to catch the engine.

Not teaching you to suck eggs i see the vac hoses have been replaced including samcos but is there a boost leak, may be on the breather side of things as this will make things way to rich and the ecu can't copy at first when dropping to idle??!

Could the tunner/mapper increase the injector on position from the standard 1800 rpm to say 2400 to give it more chance of sorting it self as you say with the light fly wheel it will return to idle very quickly?

Jay

Reset all the throttle position and tried it at different openings.

No leaks whatsoever. Please don't worry about me sucking eggs as I am open to all ideas. The PCV system has been replaced.

Would be a possiblity to tweak the on position, we had discussed tweaking the map to reduce the fuelling being put in at the decel point but it would have an adverse affect on the accel also as the ecu uses the same area of the map at certain points.

[Markarina]

Hmmm I've had this problem ever since I got my 3B back in 1999, the car is was stock when I got it, and is still pretty much stock ( Samco hoses, magnecor HT leads and forge DV - only fitted last year ).

The problem went away last for a little while after I had, the samco's, forge DV, WGFV, PCV , flame trap and MAF replaced.

I have the next 4 weeks off work so assuming the chemo doesn't knock me flat I can pop over if you want another 3B with the same problem to look at for comparison.

[Corey]

I think if we can sort the issue on one car it may open up the problem for other's.

You are more than welcome to pop across anytime you like

[Jamo]

Have you tried putting the stock Ex Cam in?

Also try it might sound mad changing the dump valve to the wrong way round or putting a to atmosphere one in as a test.

[Corey]

Have you tried putting the stock Ex Cam in?

Also try it might sound mad changing the dump valve to the wrong way round or putting a to atmosphere one in as a test.

Not tried the stock cam but it is an idea.
Tried the DV both ways but the atmo idea would be better than no DV at all.