GlesgaKiss

So am I right in having brown drawers? Or not the end of the world if just for a second? (a knock reading of 83 that is...the drawers can go in the washing machine)

I've had a high knock reading a few times recently, and every time it has been in the redline. Only for a second or two, as I never try to redline it on purpose: It only happens when pulling away quickly when the road is greasy, and spinning all 4 wheels by accident.

The rest of the time it's perfect...barely goes above 11 or 12, which is very strange.

So it this to be expected in the redline or do I have a problem?


Thanks in advance Scoobynet

Alan

bluenose172

iTrader: (2)

What gear does this happen in, is it only on aggressive starts? Could be false knock, or does it happen say starting from 3rd low down to the red line, then I'd be worried.

billsandhu

Its probably "other noise" thats being picked up, especially if its spirited starts, wheelspin and hitting rev limiter.

GlesgaKiss

Hi, cheers for both replies.

It's 100% perfect the rest of the time. Even when absolutely flat out in every gear it never goes above 12-15. Just occasionally for a second I see the check engine light flashing(Andy F mapped it to flash above a knock reading of 30), usually as I said, accidentally spinning all four wheels and going into the redline in 1st. Although the other day it did it in 4th...and I'm sure it wasn't in the red: maybe 5.5 - 6k rpm?

Again, it was only for a split second, as I obviously backed off as soon as I saw the CEL flash. Still worrying though. I'll maybe drop Andy F an email, although was wanting to avoid that as he's busy at the best of times, and now he'll be winding down for xmas.

Does that sound like it could be other noise it's picking up then? I didn't even know that could happen.


Cheers, Alan

GlesgaKiss

Just to clarify - It has never done it low down to the redline. I would never do that if it was detecting knock anyway. It's only for a split second at wide open throttle usually when hitting the redline in first.

Pete

Alan, probably a DUMB question, Andy didn,t map it so the engine light acts as a rev-limiter did he??

My car was mapped by Richard @ tractive and when i get to 7k revs the engine light comes on for about a sec, i panicked like mad when i first saw this and called Richard and he told me he,d mapped it this way, i,ve spoken to David@ API about this too and he,s seen cars done like this aswell, just a thought as you said it was when you was close to the limiter it was coming on..

GlesgaKiss

Nah, fair enough question Pete as I actually thought the same...and it maybe does do that aswell. But it's definetly programmed to flash above 30 - incase I get a tankfull of dodgy fuel - and it's definetly showed high knock readings every time.

Last one was 83 as mentioned, and there was one before that at 60 ish, and one before that about the same. It's happened about 3 or 4 times in total over the last few months. The two that I remember before the last one were when spinning the wheels in first and bouncing off the rev limiter -having a bit of sideways fun late at night. The last one was flat out in 4th at quite high rpm, but I'm sure it was still a fair bit away from the redline.

Andy mapped it so all the useable power came before 6k anyway, so I've no reason to redline it.

Pete

Well hopefully mate it,d just be the SPIRITED driving that caused these high readings, keep a watch on it though fella...

GlesgaKiss

Hope so!

Have a good Christmas

Pete

You too fella.......and DON,T worry..

Worry when it does go bang, hopefully never.......

billsandhu

Bouncing off the rev limiter would certainly cause it to show a high knock reading.

APIDavid

iTrader: (4)

Exactly as Bill says, hitting a rev limiter will cause lights to flash usually. Rev limiters cause knock. Hopefully that'll be it.

Try getting a shift light set up 200 rpm below the rev cut that way you'll avoid the knock, which is never good for an engine.

David APi

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Adam K

I have PFC, and as Alan, I get high knock reading on revlimit/cut.
Been told it's no big deal, but...
What is the cause?

APIDavid

iTrader: (4)

It's either fuel cut or ignition retard or a combination of both, depending upon the choice of the mapper.

David

Jolly Green Monster

iTrader: (4)

PowerFc fuel cuts only on the Impreza.. unless you have a very rare modified one that did ignition cut.. but unlikely..

As has been said you are not doing the engine much good bouncing off the limiter.

Simon

Adam K

My pfc does fuel cut.
I have been pondering the mode to raise rev limit 2-300 rpm and use the highest 3-500 prms to retard ignition to near tdc to soften 'the blow'. Is that a good idea or am I mising something?

Jolly Green Monster

iTrader: (4)

you can do that yes but because the powerfc interpolated from the row before to the current row etc.. you woukld need ideally to alter the rpm row increaments and then do that etc..

Simon

GlesgaKiss

Thanks to both the experts who've replied.

I'll try and avoid the rev limiter in future! It's just so much fun popping it into first at a quiet junction and getting it sideways briefly.