Roojai

I have had a knocklink on my car for about 2 weeks. The car is a wagon with a TD05 turbo and a Z4 Ecu (Jap ecu). It is de-catted.

I am fueling with optimax and octane booster and the knock link is on it's most sensitive setting.

The car is running very well and I have found that I rarely get more than 2 greens showing on my knocklink. I can sometimes get a couple of orange going towards the top of the rev range in 3rd and 4th but I have not been worried about this (just engine noise).

Today I had the red light up momentarily twice, both times in 2nd gear. I had been thrashing the car a bit and all had been well. Then, coming out of a tight corner in second, the revs at about 3500, I floored it and hit max boost quickly and hard, got a couple of oranges and then a momentary flash of red. Did it again at the next tight bend (keeping a better eye on the KL this time) and saw that I got a momentary flash of red at about 4000 rpm which disappeared and all I had were greens to the rev limit.

So it does seem to be DET, but only for a split second, in conditions in which I am pushing the car very hard in second gear.

Should I worry?

Is the decat the cause? Or is my KL just very sensitive and it is picking up slight DET which is normal and the ECU is detecting and retarding the ignition as it should?

97 rExy

no det is a good det
4000rpm is when you get max torque.....rod went through the block @ 4200rpm on my previous engine.
you should only get the first green on knocklink
any more lights need to be sorted

Roojai

Thanks for the reply, perhaps I need to see someone about it.

I thought that you were supposed to adjust the sensitivity and the sensor will pick up normal engine noise and light up more lights towards the top of the rev range if set on most sensitive.

Roojai

I've been driving today and not getting more than 2 greens and occasionally one orange at about 6000 rpm WOT

I think I might be able to get a red again if I open the throttle very suddenly while already running a trailing rpm of 3000+ but I'm not going to try.

If I accerate through the rev range it seems fine.

TheSquirrel

Steady throttle equals closed loop fuelling, ecu fuels based on lambda

WOT is open loop fuelling, ecu fuels on predetermined map based onTPS, MAF and MAP

Get the car on a Select Monitor to ensure all sensors are operating within tolerances
It sounds like one of the sensors is not giving the ecu the right info but not enough for it to throw a CEL When i posted on SN i got no response other than "any det is bad" Hooked the car up to a BOSCH diagnostic machine and spotted the MAP sensor was really slow in reacting from vacuum to boost, thus giving a brief flash of red on the KL, going from steady throttle to WOT then no activity up the rest of the rev range Changed the MAP sensor problem solved no more det

Not saying this will be your exact fault but it should help

Agree with 97rExy "No det is good Det"
Your car fuelling properly will show NO activity on the KL, 2 green at very most

Grant

Roojai

Thanks mate.

Where can I get my sensors checked. I know the MAF sensor and the Lambda sensor are OK so I guess the MAP sensor would be a good one to check.

Where is it, how do you check it and is it cheap to replace?

Cheers in advance

TheSquirrel

Its located on the inner wing on the drivers side After the brown coloured canister, above the boost soilenoid There is a vacuum pipe going in and finishing

As for the checking the sensors find an auto electrician that possesess a Bosch Diagnostic machine for Jap cars It cost me £50 plus vat but the fault was cured within 10 minutes after that no more det We had a later model MAP sensor so thats what i fitted, i know an after market 3 bar MAP sensor is in the £60 region

Grant

micared

Your inlet temps may be worth monitoring......when they get high you increase the likelyhood of det. If your only getting det when you're thrashing it, and the car is already hot, you're asking for it, really. All assuming you're still on the standard topmount i/c. The KL should always be set to max sensitivity, btw.

Roojai

Thanks for advice.
I had thought about temp but I considered as I had been going quickly in coolish weather that the TMIC would be doing it's job ok. I hadn't been sitting in traffic. But worth considering for sure.

It seems to happen during sudden changes in boost levels only so I am beginning to think it could be the MAP sensor as suggested or else my ECU just can't cope with the spool up speed as a result of a decat.

I can even get orange lights momenarily at only half throttle as long as I depress to half throttle suddenly at 4000rpm.

If I let the boost build gradually I can have foot to the floor all the way to the redline with just greens, even in fourth and fifith (to 112MPH)

It's weird! I even could have sworn that I got a red on lift-off once. Sometimes it seems fine, but then it's not.

Any more ideas?

micared

Red on lift off ( between high rev gearchanges ) is transitional det, and I got rid of it on mine only when the car was remapped. Prior to the tek3, it would flash the red between 3rd to 4th and occasionally 4th to 5th under load ( wide open throttle ).

Roojai

Did a search on transitional DET and found that this, as well as DET on sudden throttle inputs is not too uncommon afterall.

Might have to put my CAT back on until I can get it remapped!