swaussie

I have experienced in my STi7 quite a few times fuel cut in top gear on Autobahns. I was wondering if driving at 155mph ( indicated 6200 rpm ) and the engine just shutting off is damaging to it?

Leviathan

Maybe, trouble with fuel cut is that it will lean very quickly for a short time, the big question is, how long does it need to be lean to cause damage! Ie, piston or bearing.
At that sort of speed, exhaust gas temps will be prety high anyway and so will exagerate the problem and so increase the likelyhood of damage IMHO.

ozzy

It's always been a bit violent on classics, so I'd be more concerned if it did it mid-corner at 155mph. That could ruin your day pretty quickly

Stefan

STi8 Mate

Are you sure it's fuel cut, associated with overboost, and not 250kph max. road speed limiter?

In any case there is a big difference between lean running and no fuel at all. Without any fuel there can be no heat, and no detonation. There is also no power but that's the point.

swaussie

STi8 mate, I assumed it was fuel cut at the max speed. It just stops the engine dead, it dies for a few seconds and then kicks back in and yeah its pretty violent.

urban

iTrader: (1)

I think its a limiter. And I also am pretty sure that Mike Wood posted something on here a while back about there being a limiter in 6th gear a 6,250RPM.

Shaun

[Edited by urban - 8/13/2003 9:16:06 AM]

LG John

Now, now - it was well established that a sudden and violent shut down in power mid-bend would cause no problem at all

[Edited by Saxo Boy - 8/13/2003 9:25:32 AM]

dowser

There's a soft limiter on top speed, it shouldn't be violent.

Remind me what mods you've got again?

Richard

swaussie

Hey Dowser, Has the clutch let go yet

Mods are: MRT 3" pipe with sport cat, SS uppipe, and Dawes. When I say violent I mean it feels the same as fuel cut with overboost, which at 250kmh feels pretty violent. I guess then it shuts off for a drop in speed of close to 10kmh and resumes back to cut. I just think this couldnt be good for the motor and was wondering if this was the case, ie, if you do it 4 or 5 times in a row will it go pop?

Gidney&Knowlesy

Have you got an uprated fuel pump fitted?

David_Wallis

if i was at 155 mid corner that would be the least of my worries..

prime concern would be the tyre wall

David

[Edited by David_Wallis - 8/13/2003 4:17:45 PM]

dowser

What boost do you have when it cuts (stock cut is 1.44 bar from memory)? I can DeltaDash it for you if you like, email me - lunchtime around Zurich would be best.

Whatever it is, it doesn't sound good occuring at these speeds/revs - be careful.

Richard

PS: clutch is toast, but new box still isn't finished - Anneau du Rhin on Friday (on slicks) saw me having to exit corners on a quarter throttle...anything more and it slips. Strange, it's OK on road - guess it just overheats.

Beer Good

Am a total idiot engine-wise but at 150 mph any cut is going to seem violent due to air resistance. If you managed to stick your arm out the window at this speed it would likely snap at the elbow. Magnify this by the frontal area of your car & you get the idea?

swaussie

I am assuming that its the "soft cut" at the speed limiter but does seem rather violent at these speed probably due to what "Beer good" says, wind resistance and the fact it happens straight away, both the cut and then the engine firing back into life, its a lot like it would feel like lifting your foot on and off the throttle at these speeds. What does a Soft Cut do?

It really does feel and sound like fuel to the engine has been stopped, it stops accelerating instantly and gets a muted sound from the exhaust, drops a few hundred RPM and the engine cuts back in.

My boost when it happens is running around 1.2 bar so I dont think its overboost.

I dont believe that any one else on here has not experienced hitting the speed limiter on an autobahn

Gridlock Mikey

LOL @ Saxo Boy and Ozzy

In agreeance with Dave, 155mph corners

Mikey

Lee_1075

iTrader: (1)

I would like to bring this topic back up because exactly the same happens to me!. Whilst driving on the autobahn today i also noticed that at 6200rpm (250 KMh) in 5th gear the cars power just totaly cuts off, slows down maybe 5 mph and kicks back in again. As it cuts off the boost goes down too 0,5 bar and then goes back up to 1.1. I assume there is some sort of limiter somwhere?. This only happens in 5th gear, all other gears can be red-lined. Has anyone got any ideas how to disable the limiter?. Or would the Apexi Power FC get this problem resolved?. This is really annoying me as the car launches forward when the boost comes back in.

Thankyou, ohh and here are the details of my car:

MY98
VF24 turbo
MY02 WRX LLK
Bastürk Downpipe.
Forge Dump valve
Supersprint backbox.