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rubberbudgie · #41 27-10-2010, 07:48 PM

It appears I made a typo, should read 1.5bar not 2.5bar - around the 21psi mark anyway when the problem occurred but earlier on it had reached 2bar for a few seconds max. The map that came with the car when I got it goes up to 250kpa (2.5bar) but all values above 220kpa are identical across all load points so I'm guessing they never got any further with it. When I first bought the car and took it to ASG I was told the engine was built to run the extreme pressures associated with using NOS and should be good for at least 40psi.

As for DIY tuning, some people seem to be of the opinion that engine tuners are magical wizards that should be worshipped from afar and that it is beyond the ability of us mere mortals to even attempt to do anything as crazy as tuning an engine ourselves. The only advantage a professional tuner seems to provide is the speed in which the eventual tune is achieved. It takes me a LOT longer to get the exact same point, that is all.

There is a fairly standard procedure involved in tuning an engine (fuel, ingnition, boost, fuel again, accel & decel enrich/enlean), and as long as the basic rules of not running too lean an AFR (or too rich), avoiding detonation and pre-ignition and making sure all external factors (coolant & air temp, atmospheric pressure etc) are factored into the equation then everything should be fine.

I always run fresh O2 sensors that are calibrated both in free air and with lambda stabilised reference gas every 1000kms (a little over the top I know but never hurts to be safe), I use exposed tipped (fast-response) EGT probes and I have fuel, water and oil pressure & temperature sensors all connected into the Motec with safe limits on each in case of any problems. On top of that, my spark plugs are always 2 heat ranges colder than standard, octane booster is always used and timing is retarded 2 degrees for every 50hp of NOS being used (150hp maximum).

So after all this, I have then verified my maps with numerous professional tuners before using them and have never once been told I have had anything set that could cause any potential problems.

So with all of this in mind, how could my "DIY" tune have caused the head-gasket to give way like it did. If I had torched pistons or valves or cracked something due to extreme cylinder temperatures then fair enough my DIY tune would definitely be to blame but that is not what has happened here, or have I missed something somewhere....?