It says 10.9 for air/fuel ratio. Does this mean its 10:9 ratio? If this is the case is it too rich? I hear lots of guys have a air fuel ratio of 11.5-11.7 (is it dangerous to be this lean?) What is the optimal air fuel ratio for safety and performance? I'm not an expert at this stuff so I'm asking for professional advice.

I think the dyno was conservative because I told the tuner the redline was 7500 rpm and not 8000 rpm. I also told him I did not want to be near redline when tuning so it seems he let off around 6500-6900 rpm. I figure if we got closer to redline we would've made 15 or more hp?? Whats your take on that?


Thanks in advance!

 

Not sure if it would help, but would a list of mods on the car help you answer my question?

 

It's 10.9 / 1
Air / Fuel Ratio... So 10.9 Air particles for every 1 Fuel

14.8 Is 1.0 lamda, or "Optimal" combustion anything less is rich and anything more is lean.

Optimal is a strong word, optimal for what...

Turbo charged engines use gasoline (a fluid) to soak up heat as it converts to a gas. So the richer the mixture the more heat is soaked up, reducing the chance for detonation. That's why under boost you tunr rich, and at idle you like to go a bit richer than 14.8 so as to have some breathing room should you have bad gas, or atmospheric pressure issues, which all affect AFR.

But Less is rich, more is lean.


As top your question, probhably not, since HP and Tourque drop off just before / at redline.

 

I guess optimal in my definition is to make the most power while being safe in regards to preventative measures. Don't want it running to lean that might pose future problems.

 

I am not expert either, but I would think 10.0:1 AFR would be more then richly safe. My AFRs are in that range. Some are higher but I try to keep them at 10-11 under full throttle and full boost.

I would think that it would be dangerous to run ratios greater then 13 or so (under boost). But don't quote me on that, wait and see what other people say. I know to that knock can still occur at those AFR levels so yu want to watch that.

BTW was this a tail pipe sniffer WB or installed into you DP?

 

I figured letting off 1000rpm+ early on the dyno may not show all the hp that might have been there.

So do you think 10.9 is too rich or just rich?

 

What was funny is that before the tune the car was running leaner at 11.8 and made less power. After the tune it was 10.9 and made more power. I don't get it. The car was tuned with a laptop.

 

From the look he ran a baseline (Run 1) and tuned it a bit rich, to be on the safe side, (what you requested) and gave you a bit more HP, without looking at Ignition (Timing) and other variables like EGT, there's no way to tell whether there is more hp to be had, but likelyhood is yes, since it is very rich, the cost for that HP, would be running closer to the ragged edge...

-DC

 

Looks like a nice safe tune to me, although I would add a bit of fuel at transition to reduce that a/f blip.

It's true that you could make more power at 11.5:1, but it's also riskier. That looks like a nice conservative daily driver tune. What are your mods?

 

This would point to some power found by changing the timing, of when the plugs fire.
Likelyhood is that the timing was a bit conservative on the old tune, and the mixture was not burning completely or too late to create a fast even burn.

The blip in the transition is possible if he let the ecu tune itself. Depending on the ecu. It looks at the Map sensor and saw a dip in Boost, and leaned out the mixture, since there's less pressure you don't need as much fuel. Or it could be experience, the only thing that would concern me is if you went non seq. that area of the map might lean out your system, so if you go non-seq. get it tuned before you step on it.

 

Am I better off leaving the tune as is? Would be nice to have more power, but I don't want to put anything at risk. Maybe a little bit leaner won't hurt?

I kinda like the seq setup for quick spool up.

Here are the engine mods:

Denso Fuel Pump
Apexi Air Intakes
Greddy 2 Row FMIC
Fluidyne Radiator
1300CC secondary injectors
Lightened Flywheel
Heavy Duty Pressure Plate
Act Extreme Clutch
Greddy Elbow
'99 Spec Y Pipe
M2 Down Pipe
Petite Mid Pipe
JIC Catback
Greddy Profec B
Apexi PFC Commander

 

I believe this is when everything is combusted and there is no fuel left over. And i think its 14.7