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Questions regarding fuel cut.....


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Guys, I was having a conversation with Mid about fuel cut after reading his thread, and he said I would be better off posting this as a question, below is what we have said so far, do you have any pointers on what I should do......

 

Ashley Willis wrote on 27-07-2003 04:18 AM:

Mid, when you get fule cut what exactly happens while your driving, as I have a FCD fitted, but have never hit fuel cut, even while boosting to 1.4......???

 

Ash.

 

*************

 

Mid'lifecry'sis wrote on 28-07-2003 09:51 AM:

1.4!! Hows the engine?! LOL..... The cut just kills the engine m8, lights appear for a couple of seconds with vital items like breaks etc still available, then power comes back. I have damaged my exhaust and I think the .2 of a bar loss 1.0 to 1.2 is due to this. The cut must have been a surge through the exhaust at 1.2.... allowing a cut. Anyhow, thats what an FCD is supposed to do....

 

*************

 

Ashley Willis wrote on 28-07-2003 03:50 PM:

Firstly, so I would I be right in believing that if I have nerver hit fuel cut then my engine has never hit its max, and could I get away without hitting fuel cut at 1.4, I mean should I confirm that I have an FCD in place and operating correctly. The bloke who had it before said it has an FCD fitted, but I dont know where it is or what it looks like.

 

Ash.

*************

 

I am no expert m8.. but running 1.4 with ALL, and I mean GOOD engine mods will not hurt, Intercooler etc, but you may find your FCD is programmed at 1.4 if the boost controller etc is set up....

 

You need to post this on Tech rather than spin with me m8, I'm not the best by a long shot!

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MY FCD (Pete Betts) is set ~18psi boost (~1.4ish bar ?) as he

made it..(I think)

 

I'm sure it can be turned 'up' but the standard MAP can't safely be

left to handle 18+ psi ? ? ? I think that's the jist ?

 

** MY engine went bang at ~ 1.4/1.5 over ~10seconds ! ! ! ! **

 

It MAY have been running lean (Pump/Filter etc)...

It WAS running hot (I/C bit iffy.. 30+C...concrete runway...QUEUE!)

It MAY have been that the 'MAP' wasn't supplying the correct fuel

ratio anyhow....TOO HIGH BOOST ? ?

 

I dunno..... just more "wood-for-the-fire" maties....:(

 

FatS.

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NO, sorry mate...

 

the FCD allowed the engine to boost >09./1.0 but then,

map might not have been able to ACTUALLY supply enough

fuel for 1.5bar ? even though it was 'willing' ?

 

That's why Pete Betts says "Your Own LOOKOUT", you have to

realise that JUST getting rid of Fuel Cut does NOT mean the Injection

Ignition system can safely cope with the extra boost ! !

 

The Fuel Cut is the "rev-limiter" and you're just getting rid of it ! !:confused:

 

Fuel Cuts are there as an engine 'safety' feature............

 

I KNOW ! !:( :eek:

 

(it was fine at ~1.2 bar......... then.............. I got greedy)

 

FatS

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Originally posted by Steve W MY FCD (Pete Betts) is set ~18psi boost (~1.4ish bar ?) as he

made it..(I think)

 

I'm sure it can be turned 'up' but the standard MAP can't safely be

left to handle 18+ psi ? ? ? I think that's the jist ?

 

18psi is about 1.2 bar. Other than that, pretty much all you say is correct Steve. The stock ECU will not be supplying any more fuel at 1.4 bar than it does at 1.2 so all you will succeed in doing is generating huge amounts of heat at best and taking a piston out at worst.

 

Ash, you will deffo have an FCD fitted. Depending on the manufacturer, you can adjust the fuel cut to wherever you want it. Both Petes and our HKS ones allow this. FCD's are nearly always mounted on or around the ECU which is under the plastic cover where the passengers feet go.

 

IMO you are playing Russian roulette running 1.4 bar on your spec. Bring the boost down, and preferably the FCD cut point too (if your particular FCD allows this) to make sure that if you get greedy and turn it back up again at least you'll hit the cut.

 

If your FCD doesn't allow you to adjust the fuel cut point and can only remove it altogether then book your car in with someone and get the thing ripped off and thrown in the bin. The fuel cut is your only safeguard against a blown engine in an overboost scenario.

 

Regards,

 

Nathan

TDI PLC

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Cheers guys some helpfull stuff there, especially Nathan. Just thought I'd mention I was only on 1.4 for about 5 months, I now have one of CW rings up my pipe ;)

 

Im cleaning the car tomorrow, will have those plastic covers off and have a gander.....

 

And one other little thing, was breaking for a roundabout and my red triangle cam on for about a second, could it have been the brake fluid level shifting about......????

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Originally posted by Ashley Willis

Just thought I'd mention I was only on 1.4 for about 5 months

 

Someone was looking down on you! I wouldn't want to run 5 minutes at 1.4. I can only presume that you didn't do any high speed/high load pulls. Even so, I wouldn't like to have seen your EGT thats for sure...

 

And one other little thing, was breaking for a roundabout and my red triangle cam on for about a second, could it have been the brake fluid level shifting about......????

 

Nearly always.

 

Regards,

 

Nathan

TDI PLC

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Originally posted by Steve W

** MY engine went bang at ~ 1.4/1.5 over ~10seconds ! ! ! ! **

 

It MAY have been running lean (Pump/Filter etc)...

It WAS running hot (I/C bit iffy.. 30+C...concrete runway...QUEUE!)

It MAY have been that the 'MAP' wasn't supplying the correct fuel

ratio anyhow....TOO HIGH BOOST ? ?

 

I dunno..... just more "wood-for-the-fire" maties....:(

 

FatS.

 

Sorry to hear that Steve, :( I didn’t realise things were that bad from your post. Hope you get her sorted soon. :)

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CHEERS Pete (had 11 years of thrashing me RS Escort around..

FLAT OUT ! - no costs AT ALL - so this is just GodArse catching-up

I suppose ?)

 

NATHAN ! (grabbing thread cautiously..:p )

 

even allowing for the "dodgy fuel pump thread" recently....

 

What choices of JapPLUS pump do you do ? ?

 

How 'noisy' ?

 

How much ?

 

Mine's hopefully going back together soonish, and first 'extra' mod

is DEFINITELY bigger/higher pressure pump...

 

FatS.

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Originally posted by Nathan

Someone was looking down on you! I wouldn't want to run 5 minutes at 1.4. I can only presume that you didn't do any high speed/high load pulls. Even so, I wouldn't like to have seen your EGT thats for sure...

 

 

 

Nearly always.

 

Regards,

 

Nathan

TDI PLC

 

Thats the thing, I was nieve and didnt know too much, I was racing anything big powered, including the odd bike, it even tounched 1.4 and half once on a nice cold winters day.

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Jeez, that was a pain in the arse, I held down the shift key too long, turn out it was a short cut for a mobility option, tunred itself on and ignored any key strokes, as I was trying to say......

 

So have I been that lucky it didnt go pop......!!!! Although I say I drove it hard, I never let it go into the red which starts around 6,500rpm I think, giving it around 1,500 spare......

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Originally posted by Steve W

NATHAN ! (grabbing thread cautiously..:p )

 

even allowing for the "dodgy fuel pump thread" recently....

 

What choices of JapPLUS pump do you do ? ?

 

How 'noisy' ?

 

How much ?

 

Hi Steve,

 

Not sure what you mean by 'JapPLUS' pump? We only use one type of pump, the Walbro GS341/342 series, and we find it's good enough for around 500bhp even though Walbro won't rate it as higher than 400bhp.

 

I honestly don't find them noisy at all, but then we do use the foam sleeve around the body of the pump which does quieten them down quite a bit. Plus we use a relay so that the pump isn't running with the engine off so again it's harder to notice. I've not had any customers raising any concerns so thats a good pointer I guess.

 

Our kit is £160 excluding VAT and comes supplied specifically for the MK4. It has the relay, fuel filter, foam sleeve, full fitting instructions (with pictures), all wiring, bullet connectors and cable ties.

 

Best regards,

 

Nathan

TDI PLC

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I have had to take the fuel pump cage out of the tank before now to see if the fuel pump is working as you can't hear a thing even with the spare wheel out and the cover plate off, and I have a Walbro. Not a TDI supplied one and I don't know the exact model number, but I doubt any others in the appropriate range will be so significantly louder as to be annoyingly audible from the driver's seat!

 

-Ian

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