I thought i would start a thread about detonation. Im looking for any info and opinions on the subject, or rather how to avoid it.
So far i know that the fuels octane level has a lot to answer for, for example 98 will make more power safelly than 91 or even 95 when they are all tuned to there individual limits. So if the engine was tuned for 98 and you ran 91 it may suffer detonation. Race fuels again have higher octanes.
From my basic understanding of detonation it is an unstable combustion that takes place resulting in two explosions that smash into each other, or one that ignites first without a spark occuring yet or am i thinking of pre-ignition?
Ive always heard a lot of talk about compression ratios being too high causing detonation, however people like to turbo na srs, 2jzs due to the added compression and extra tourque given, it is not uncommon to here of turbo motors running 9:1 compression and na motors of 11:1 on pump fuel, but how much of this has to do with the combustion chambers shape/design?
Which would be a better design head the open chamber head or the heart/peanut type to avoid detonation, is this the same for na and turbo engines?
Timing i no makes heaps of difference, add a bit too much advance and tink, tink, tink! Also air temp for boosted engines!
The reason i want to no more about this is my l20b turbo has started detonating since ive changed the headgasket and got it up and running again, the boost has crept up to 10psi as i noticed the wastgate actuator was loose when its suppost to be shut/tight so i adjusted it up. Ive had to back the timing out a considerable amount to the point were i cant get wheelspin at all unless im rough with the clutch, its really killed the engines performance and resposiveness. I have a fuel/air meter and its not running lean up top although its lean at idle (hunting and stalling a bit). The engine itself isnt over heating. It was only pinging when under load and high in the revs or on the limiter in 2nd and above. I also filled up with a fresh tank from another sevo and made no difference, its annoying because it never used to detonate. Im hoping im not at the limit of the standard engine as far as safe power without detonation goes. i am seriously considering building a fresh engine up with one goal in mind, to avoid detonation as much as possible. Still using cast pistons but try and find some with a bigger dish to drop compression, the best type of l head either open or closed/heart chamber, modified if need be and of course new bearings, quality gaskets etc. That way i can just crank boost and timing into it, or is it not that simple, im probably missing heaps, anyway enough rambling, thanks guys/girls

i reckon thats a good size for a low boost turbo a12 running draw through. I have found that when the turbo wheels stops spinning eg, big turbo on little motor at idle that fuel likes to puddle in the compressor housing causing a rich stumble on quick throttle opening after idling. Im following this project with much interest!

pm sent dat_1200_ute

i got these if your interested?




there the rear ones, ive a thread with info

photos as requested

nice finds mate, top buy that little sedan, looks like you got a better deal than me, but im not complaining, gotta have something to keep me busy Love the sun visor!

yea plugs have done wierd things for me in the past, ive had four new bosh plugs die eg no spark at all even when cleaned/correct gap, changed plugs and ran perfect. Was only running approx one hour under no load, didnt get a refund either Maybe the coil is doing wierd things for you. Can you whip out a plug and lay it accross head and check spark quality, that might help!

acrylic will get you a good finish from the back yard/shed better than most cheap cars. Also i found there is more light painting outside and i prefer it/extra space. Just use good quality clear and it will buff up nice! ive done 4 home paint jobs and it comes down to practise/trial and error, #### my first paint job on the mini was described as DUDE DID YOU PAINT THAT WITH YOUR PUBES by people who saw it before buffed but even that polished up nice!

Cool guys, i live in maylands about 15mins from city up magill rd! Yea i got the grille, suprised it hasnt gone already, ill hold it for you then dat_1200_ute for $100! Im home this week so just organise a time with me fellas. Whitesedan my car goes better with the nissan gasket in it now

yea i got a couple of BALD ones if you just want the rims-free. I might have one at my old mans place, ill check for you!