Food for thought

[bill shurvinton]

Originally posted by g11ary
Coming from a complete novice.....
Some ecu\'s will retard the ignition in given circomstances, Motec I believe and Apexi will retard as the water temp rise above a give deadline, Motec would eventually cut the engine, I think.

Slim chance of detonation if its running rich? If its running richer is the fuel not burning slower?

Detonation can look like someone has hit a rotor surface with a large hammer and dennted it or even in extreme put a hole on it, it certainly can hole a piston. It can either chip or crack apex seals or just shatter them leaving them to exit via the turbo, good bye turbo.

Yes rich mixtures burn more slowly, but you can still get detonation due to a number of other causes. For example, if the spark is too far advanced, then rich or not, PPP will occur early, causing detonation. For my money, less fuel and more spark retard is a less risky strategy. (but happy to be proved wrong). More fuel loses power, and petrol is expensive.

Also, running rich means there is unburned fuel lying around which forms thick carbon deposits. These are prime targets for pre-ignition (as are wrong heat range plugs).


Now think on this. EGR contains lots of water. Think of it as free water injection. When you go single turbo you rip out all the EGR ( this is actually a good thing in the case of the stock setup, but nonetheless interesting to ponder). As I have posted before, by injected COOLED EGR SAAB could run their 4 pots at 20PSI and 14.7:1 AFR.

turbo 13Bs do not like detonation. But the root cause is rarely found. (note send blown engines to Carl for a rebuild. He will take pictures and measurements that should help me find them.

Bill

[chrisBoid]

Sorry..

What is PPP and EGR?

[bill shurvinton]

EGR is exhaust gas recirculation. PPP is peak pressure in the chamber.

[Initial-D]

I think I\'ll have to have a read about the various elements within my engine so I can get to grips with this thread!!

Unfortunatly having masses of work to do isn\'t going to help me achieve this!!