NYSS Guy

iTrader: (1)

I'm not that well versed on tuning, but I have a question. Is it considered to be dangerous to tune a car a little on the lean side in a lower RPM range (i/e/ before boost), and then richen it up once boost begins?

I'm thinking of having my car leaned up a bit under 3k rpms, and then richened up above that, which is when the boost makes up for it. But my thoughts are that the leaner it is on the bottom end, it will make some more power down low. Besides, with my setup, I would think it's basically a stock car until boost comes on.

What are your thoughts?

gametech

iTrader: (1)

You won't get more power from having the tune lean on the bottom, but you will get better economy. Since cruise and low load states don't load the engine much, it's nice to have better fuel economy. Just don't be too frugal on the high side, because under power , running too lean will cost you a motor. Some people here go all the way to 10.0 to 1, but the general consencus seems to be that with a lot of boost you should run 11.5 - 12.0 to 1 for a happy-well fed motor. I have found that with anything under 10.2-1 I start to see smoke in the exhaust, and I start to worry about washing the cylinder rings.

cablebandit

iTrader: (37)

i think he means at WOT. I have mine lean down low and then start ramping up the fuel as boost comes in.I also need to get the timing the same way. I have it too conservative before 4000 rpms and I could prolly squeeze a little more tq down low with a few more degrees. Looking at my logs, you can see exactly where my alky kicks in on launch. From 4000-6000 in 1st gear a/f is at 10.0 and then it rises to 11.5/7 the rest of the run.

NoGo

iTrader: (2)

Ideally, for forced induction your a/f should represent how much boost you are running. If your car is running no boost for 2000 to 3000 RPMs, then you should have a normal NA a/f ratio for that portion.

However, on mostof the V8 turbo cars the turbo spools VERY quickly. I have found that it there is better throttle response, if you keep the NA a/f ratio a bit fat for those quick spools on the freeway.

NYSS Guy

iTrader: (1)

I had a feeling that the A/F before boost would be more like a NA setup, and then richen it up. Now, for the stupid question of the year, what is the ideal A/F for a NA application?

NoGo

iTrader: (2)

Ideally, the optimal power a/f for NA is 12.8. However, as I mentioned above you may want to set it slightly richer to take the sudden onset of boost.

Try having your pre-boost a/f around 12.0 to 12.5 and your boosted a/f around 11.0 to 11.5

Under boost, you can try moving your a/f up to around 12.1 for a little more power......but it is a little riskier depending on the build.