Knock Spike

[sti pretender]

Dump valve stopped working couple of weeks ago to find the vaccum joint had seperated. Temp fixed it and cleaned the DV after this everything was ok.

Since then have found that I am getting a high knock reading record on the Apexi commander. Car runs fine and can accelerate without it happening only when I kick the car hard in 3rd or 4th I get a knock spike high up the revs.

Can actually see it happen on the display it doesn't build up or stay high it is just like a spike then it goes.

The car can also gave a high boost reading, mapped by AF to 1.3 with a safety margin of 0.1 to allow a max 1.4 for overboost on track. Highest reading was 1.45.

Talked to Duncan at Hypertech and he suggested the temp fix might be letting the cause. Have renewed the joint and re-clipped it, tested the car at the weekend on a deserted section of road.

Run 1 - ok

Run 2 - ok

Run 3 - Knock reading 65, boost 1.42

Run 4 - Knock reading 81, boost 1.28

Going to take the car the Hypertech once Duncan is back off holidays but just wondered if anyone had any suggestions? Initially thought the DV was a HKS but no markings or codes on it, car was imported and was on it when I got it, have seen a few HKS copies on ebay so think it might to one.

[emoe]

Mine does a similar thing mate.

Although i do believe mine is now caused through a lot of changes to the engine bay.

When it was first mapped and fitted, the apexi wouldnt hit high Knock and flash the ECU light unless i was on top boost 1.4 bar and hammerinig the hell out of her.

Since then i fitted bigger injectors, a front mount, oil cooler, big bore up pipe, alcohol injection, and a few other mods, and strangely, on low boost or high boost it seems fine, not hittimg much more than 13-16 onthe apexi.

however if i am in pos.2 (about 1bar) i get hellish knock!!!

Not sure why it does it, but the car is going back for a remap when finances allow.

My advice would be to let Hypertech look. It may be the mod leaking air, making for a lean mix.

Good luck!

[cullenmin]

Has your fuel pressure decreased or been tampered with? Loose connection on the FPR?

Rich

[sti pretender]

Has your fuel pressure decreased or been tampered with? Loose connection on the FPR?

Rich

Not touched anything else and injector duty seems fine based on the readings.

Haven't got the use of my garage at the moment so will let Hypertech check it.

Thanks for the replies.