azmi951

What are the symptoms of detonation on the 951?

as soon as it makes more than .75 bars it hesitates and has a huge power loss.

I'm thinking that it is detonation because I'm driving back to Arizona from michigan (read as "I no longer an have 94 octain gas, I have to buy 91")

I'm thinking that it needs a few heat randes cooler of plug if this is the problem. any NGK recomendations from people living in a hot climate?

By the way does anyone know why Some states dont sell higher than 91? It used to be 92.

Thanks for any help.

Sean

porshhhh951

I get 93octane here locally..and also have access to serveral race shop's with anything from 104-114.

Dentonation sounds like marbles pinging inside the engine. Maybe you got some bad gas....and hitting the knock senor maybe?? Does it die completely or just stumble?
Do you have any gauges to monitor the car? @.75 bar you wouldn't be hitting fuel cut(I assume you are running stock injectors without fpr)
can you hit more than .75bar in higher load gear's in lower rpm's?

Once again roll down your window if it is indeed dentonation you will hear a very distinct sound. Possible vac leak.

Jfrahm

We only get 90 or 91 here in CO, but you don't need as high an octane number to prevent detonation due to the altitude.

I have gotten lots of detonation on my experimental turbo car (non 944) and there was not much power lost. You probably have a boost leak somewhere, check your IC pipes.

-Joel.

hosrom_951

Also check the throttle position sensor (TPS), if you hit .75bar, when full throttle? if yes, it could be that TPS.

azmi951

Thank you all very much. I had thought it could be a boost, vacuum leak but the gas thing had lead me to think it was detonation.

I will keep you all posted.

Sean

TurboTommy

You basically not supposed to hear the pinging because the knock sensor is supposed to take care of it before the human ear can hear it. Possibly as our cars get older the anti-knock system might not be as sensitive, so if you do hear it, it will be with the windows up for a split second through the fire wall.

We would need a better description of "hesitation and huge power loss".

Detonation--hesitation, yes; huge power loss,no

Unless you have totally the wrong plugs, changing spark plugs is just a bandaid and doesn't solve anything.

Like somebody already said, you need to know how much your max boost actually is.

facboy

i think overboosting. just because you're only hitting 0.75 bar doesn't mean that the klr or whatever isn't misreading it and cutting fuel anyway.

azmi951

off hesitaion, like a really crappy fuel cut rev limiter.

My max boost is 1.25 bar or about 18psi on a good day in higher gears.

I started to take a look around and there is one suspect vacuum hose, it is the one that goes to the bottom of the throttle body. It is just a bit loose and I know it would not hold pressure. It looks like it goes to the cycling valve. Is this the main pressure supply?

I will be gettin some silicone hose tomorow locally, anything I should know or avoid with this stuff?


Thanks for your help

Sean

TurboTommy

According to your last post; I would say definitely detonation (almost 18 psi boost, 91 octane, warm/dry weather, hesitation).

facboy

oh...my bad, i don't know why i missed that 'chips' in between the twists and the cat-bypass.

azmi951

Ok changed all the rubber and plastic hozes to silicone......Perfect.

Thanks for all your help from this I think that the fuel regulator was not getting all boost presssure. Thus loosing fuel

Thanks

Sean