The Pupat wrote:THE REAL BORIS wrote:I was getting the cut at 10.5 before the cooler weather arrived and I've been turning the boost back accordingly. I forgot one morning that it had been down to -3 overnight when I hit the (11.5 several times). I did it a few times after I saw it first happen, just to make sure I was right.
If you have ever seen your A/F ratio on the dyno you would know that the piggy-backs are usually set to run the SE engine leaner! It was showing 10.5/10.8 A/F BELOW 3400 rpm when on a 9 psig boost. Above that rpm it was not visible since the dyno low point reading was 10.5:1.
I will have it on dyno again when my FM downpipe is fitted. If the test conditions permit, I will run it at the higher boost too.
On the subject of AF ratios was reading an article in an old zoom mag last night on this subject. It's interesting to see why factory tunes are that rich and just how lean you can run a motor without it going cack.
Why do people still think that 10.5 or 11:1 is too rich?
Look at the tuning of any well respected performance workshop, they are all tuning cars to run in teh low elevens and mid to high tens AFR wise. I'm not talking about your dodgy backyarders either, we're talking teh big names like PAC, APC, RX, GAS and all the guys running in the front of the pack with modded turbo cars i both circuit and drag racing.
You're better to have some extra fuel to fight off detonation and allow perhaps a tad more timing, the extra fuel will make a bee's doodle of difference to overall performance, and with the added timing you may even see better fuel economy on cruise...
A long time ago my tuner told me "There is an AFR that will make you peak power, then there is an AFR that will see the car last for the whole race. The power difference is small, I'd like to see you finish." or words to that effect. I still can't complain about his results, 200kw from a stock bottom end and better then stock fuel economy.
