Car won't take timing with out knock

[MatthewT85]

So in February I had my car tuned making around 280rwkw. The car drove fine maybe a little carp down low, which I thought was the vct plug needing replacing.

The car then began flashing the cel/knock light. Replaced the vct plug and took it back to get the tune looked at. I've been told the car can't handle timing above 10psi and 4 degrees of timing was taken out anywhere above 10psi.

IAT were mid to high 50. Don't know if that's an issue.

Car has

Hypergear atr43ss2

Top feed rail with 1000cc xspurt

Jjr return flow cooler

Haltec platinum pro

Any reasons why a car would be fine with the timing then after a few months hate it.

Tuner thinks the 98 down here is bad but I can't see why it would be that bad/different

[KiwiRS4T]

How big is your exhaust? Possibly collapsed CAT? Can you check pressure or temps pre and after intercooler?

Just saw you have a Venom cat so probably not that.

Same tuner as February?

[MatthewT85]

Yeah same tuner. I do.t really have anything to check pre and after cooler.
Yeah jjr bellmouth dump venom cat hks superdragger cat back

[89CAL]

Stao might be able to weigh in here, but I believe he was having issues with JJR Belmouth dump pupes at one stage. The flange doesnt quite match up to the gasket/turbo and you need to grind out the dump a bit to make it match.

I never had this issue but I believe that it was a problem

Do you know how much timing is actually in the MAP up were the problem area is?

[MatthewT85]

Ok I don't think I had the issue as I would have noticed when I went to put the gasket on.
No I don't know how much timing is in there before after the change. I may have to see if I can find out tomorrow.

[tridentt150v]

If everything was working fine for a while then it changed without notice then my bet is fuel starvation, time to check the filter, FPR, pump etc

Pump is my guess, its not delivering enough when you boost!

[MatthewT85]

He did mention he took a bit of fuel out of the map as the afr was a touch rich. Would that rule out the fuel system? I didn't ask either but a pressure gauge in the fuel line would tell whether there was an issue in the fuel system wouldn't it?

[hy_rpm]

Check you exhaust isnt a jasma approved item which i think hks super dragger is which will have a smaller tapered pipe in them like 2 to 2.5inch inch which will restrict it at that power level

[MatthewT85]

It is a jasma one. But I feel it's odd that I was making the power with the cat back already

[GTSBoy]

When it changes from something that used to work, then it is not the fundamental architecture of the car.  If it NEVER took timing then we'd go looking at the return flow cooler, the exhaust, etc etc.  So we look to things that can change.  As has been mentioned already, cat is a possibility.  After that it's fuel system, as has also been said.  What may be happening is something unexpected like just one dirty/part blocked injector.  If you get one cylinder running a bit lean it will knock and the others won't, and the mixtures may not show up too badly because 5/6 of the engine is working right.  Those Bosch injectors may or may not have the little inlet filters in them.  They can catch crap and bock really quick.

[Lithium]

13 hours ago, MatthewT85 said:

Any reasons why a car would be fine with the timing then after a few months hate it.

Tuner thinks the 98 down here is bad but I can't see why it would be that bad/different

 

The fact the tune hadn't gone leaner would suggest it's less likely to be a fuel delivery issue which is one of the causes for this kind of thing which I've seen.  To cause THAT much sensitivity at that low boost and requested timing would need to be quite the fuelling issue, not something that would be too subtle to pick up even if it was only one cylinder - imho.

The other thing (and probably more common cause for this type of stuff) is triggering issues causing the effective timing to fly way off requested timing.   Either make sure the wiring to the CAS is good, or if you can find someone with the same type of CAS then maybe try swapping them over - or anything else you have the tech to do to rule that out.

Edited November 9, 2016 by Lithium

[MatthewT85]

2 hours ago, Lithium said:

To cause THAT much sensitivity at that low boost and requested timing would need to be quite the fuelling issue, 

 

sorry does that mean it would be pretty obvious if there was a problem with fuel system and its most likely not the issue?

[Lithium]

While I can't say for 100% sure, I doubt it's a fuelling issue if the car didn't start running leaner when the issue came about.

 

[MatthewT85]

Yeah that's my thought too as it looks like it was actually 3 pc richer than the initial tune.

[tridentt150v]

Or his harmonic balancer has spun?

[burn4005]

my thoughts:

a) you have one or more blocked/bad injectors

b) your ACTUAL timing is not what the ecu thinks it is. check both base (locked) timing, and actual timing while revving the engine up with a timing light.

[hypergear]

I'm leaning towards to what the Afr gauge say as well.

[MatthewT85]

On 11/13/2016 at 0:35 AM, hypergear said:

I'm leaning towards to what the Afr gauge say as well.

do you mean if the afr was fine or rich then there isnt an issue with fuel system(injectors, FPR ect)

[hypergear]

as in if fuel is running lean due to blocked fuel filter, injector or bad fuel pump.

[MatthewT85]

Ah k well the afr were all good