hi all,

firstly a run down on my car....
it is an EL XR8 I, 165,000 auto(new)
i have put a K&N panel and full exhaust in it with high flow cats and ELGT extractors.
recently replaced with platinum plugs, new leads, dizzy cap, rotor button, new coolant temp sensor, cleaner MAF with proper contact cleaner adn serviced with all the best gear regually...
car is run strictly on shell 95 with standard timing which has been checked...

when chasinig my brother the other night the car was running great! pulling really well and keeping up with him when i didnt think it would, i was really happy.

the only problem was that with full throttle off the lights, the car pulled great but once it got right up the top of the rpm band it starder pinging (well thats what it sounded like, maybe detonation?)

as soon as i eased on the pedal it shifted to second and then i could apply full throttle again without problem....

thoughts?

Are the Injectors, MAF & ECU standard? Did you clean the stock MAF or replace it with another?

Sounds like a MAF issue to me.

ywah maf was cleaner with proper contact cleaner, maf and all electrics are stock but new as lsited. went really well the whole rev range until i got up into the last few hundred rpm, the sound was quite obvious

Get it on a dyno/wideband and get the AFRs checked.

Sounds like a timing issue. How old is the dizzy? Is it a stock unit? If you can, try taking a couple of degrees of timing out of it, and go for another fang.....
Maybe try a tank full of Premium 98.

+1

ok guys, sounds interesting.

the timing has been chaecked and is spot on 30 if anything a fraction under...

new iridium plugs, eagle leads 8.0mm and new cap and rotor but the dizzy is factory and original as far as i know...

however its only 165,000 ks old...

do the 6 cyl ones swap pver because ive got one of these at home?

is 98 req in these? i only went for 95 given the lowish comp... i always use shell as i have heard its the cleanest

Try running some water through engine..
I use a coke bottle and connect it to vacuum line, hold throttle open to about 2000 rpm then
put hose in bottle.. The water cleans the chambers big time..
DON'T let engine idle while hose is in water !!!
Another option is sorting out the PCV a little better..
I fitted an alloy tube in mine where it comes off the back of inlet..
By raising extending pcv higher there's less chance of sucking up oil into inlet manifold...
Oil in combustion chamber promotes detonation..
Also oil builds up as carbon in your combustion chambers...
The reason water is used to flush out carbon...

ok that sounds like a good idea. how much water should i run through it?

How much water???
Does it suck it in quite fast???
Have you ever locked up an engine???

MITCHY

This thing would have to have a lot of carbon in it to be pinging.

If the timing is spot on, just check the fuel mixtures. It will take a dyno op 10 minutes.

Never had one lock up and done 1000's over the years..
Use the charcoal canister line.. It's smallest hose.. Or use a restrictor on a larger vacuum line which is even to all cylinders.. Don't close throttle !! Thats why I said rpm at 2000 rpm..
DON'T pour water into the intake !!!
I use at least 6 litres @ 600cc at a time... Making sure it SUCKS it UP from ground level..
If you've ever seen a blown head gasket ?? The blown area is usually VERY clean due to water / coolant action..
This also means a cheap water injection kit works also...
If you check most inlet manifolds ?? You'll find they are full of oil...
A catch can / oil separator like the turbo guys do fixes these issues..
Which btw is BAD news on forced induction motors where detonation must be avoided at all costs..
Yes retarding [or correct timing] should prevent detonation..
Correct fuel mixture also...
May pay to check TPS ?? Check that voltage increases while throttle is opened.. Approx .9 to 4.5 / 5v ..
If the EGR has been disabled or not working?? This can cause detonation issues too..
Fuel filter and pump up to spec ??
Check vacuum leaks between maf and engine..
Trouble with dyno ?? Unless you check these things first your spending $$ to find any issues ...
The system cannot really be tuned so its just a diagnostic tool to find faults..

try all the above,
being at the top end it could also be fuel, ie fuel pressure. Might pay to tee in a fuel pressure gauge and see what it shows.

where does the charcole canister line run to on the manifold?

i rant he car hard again last night and it almost felt like it had a bit of a vibration on the upper half of the rpm band... not abd but it was there...

does this help the diagnosis?

i will try the water thing.... i will also try 98 on the next tank but i have been running 95...

the dizzy is only 165 old there is another one for sale which came out of a 175 k xr8 which i could try... do the el 6cyl ones fit?

any chance old and out of spec O2 sensors would cause this?

i ahve replace the coolant temp sensor and ignition is all new except for the dizzy although its low millage

is it worth getting injectors cleaned? i run fuel injector cleaner but would a remove and clean be worht while?

thoughts???

very unlikely its the dizzy.
disconnect the battery for an hour or so and see if it still does it.
If it does, then its not related to long term fuel trims (ie o2's)