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....?

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Mate that's fair enough.. and I do agree with what you're saying somewhat.

BUT, most people here haven't got the balls to self tune a stock engine let alone a Cosworth one.. you're somewhat a mad scientist

The main thing I'd worry about when self tuning is that even if I had 95% of the knowledge of the tuner, its going to be that last 5% that I don't know, which would end up biting me in the arse.

Oh for sure, it always is that last 5% that is the hardest (and sometimes the most expensive) to learn but as with most things the best way to learn something is to get in there and have a go.

But as for the balls to tune a Cosworth, I reckon that it's safer to tune a stronger motor than a stock motor which will have much less room for errors should something be tuned wrong. But that being said, I tuned my white wrx which has totally stock internals with no problems at all and that uses NOS as well, all be it with a much smaller HP shot. Again as long as safeguards are in place and you don't go too crazy with the amount of HP being injected then there should be no problems.

But what I will say is this, please don't read my responses as me not being appreciative of everyones feedback because I value everyones advice and experience on these forums immensely and greatly appreciate the time people take to respond to my never ending amount of questions. And having been a long time reader before I ever posted on here I'm sure a lot of other people out there appreciate the time people take to answer questions too.

Unfortunately the black budgie project is going to have to go on hold as I'm off to Malaysia for 9 days in about 2 hours time so will catch you all when I return.

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250KPA in the motec software is absolute, so thats only 1.5bar of boost isnt it?

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MY93 Impreza GX 1.8L, 0hp, 0nm

He said that in the top of post #41.

250kpa != 2.5bar

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MY93 Impreza GX 1.8L, 0hp, 0nm

So was the motor running 2.5 bar of boost ?

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97 WRX V3 STi with goodies.

No - that was a typo. Darren confirmed above that it was approx 1.5 bar or 21 Psi.

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[COLOR=Black]Liberty GT Spec B tuned 240 HP & 372 Nm at the hubs.[/COLOR] "Instead of banning high performance cars - ban low performance drivers"

0kpa = vacuum
<100 kpa = partial vacuum
100kpa = atmosphere pressure,
200kpa = 1 bar
300kpa = 2 bar

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Long live the WRC

I'd be thinking he is running manifold pressure (gauge) as load rather than absolute pressure. He mentioned all the values are the same above 220 kPa and I would have thought a motor like this would have been tuned higher than 1.2 bar.

Out of curiosity, does the M800(non pnp) use the knock sensor at all? It would be neat to setup some kind of active knock control similar to the stock ECU.

Edit: Just looked at Motec ECU manager and it doesn't look like manifold gauge pressure is available as load, well not on the old version I have anyway. I know the ViPec software allows for gauge pressure (i.e. -100 to 150 kPa(g)), but it looks like Motec only has absolute pressure.

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