Air Fuel Ratio For Naturally Asperated Apex

[RTX Meirda]

I just bought a wide band O2 setup for my Apex. What air/fuel ratio should I be shooting for at different throdle positions?

 

[blue er]

buy some dyno time, but most na 4 strokes seem to like 12.5:1 give or take a bit, my tiburon liked 12.7 across the board overall

 

[DYNAREX]

i think 13-13.5 is best power

 

[Srxspec]

87 octane on the dyno anything leaner than 12.3 did not make any more HP. That's at WOT.

 

[APEX 21]

I heard they come stock 12.5 to 1 air to fuel. I've heard switching it to 13.5 to1 will get you better fuel economy with no real hp loss

 

[RTX Meirda]

Does anyone know at what ratio there begins to be a power loss?

I know Ulmer has been to the dyno, so i believe the sled will not make any more power going leaner than 12.3 to 1.

What is the limit where power begins to drop?

 

[Bigger Hammer]

Hope you don't mind me putting a couple more questions on your thread, they are related, not trying to hijack thread. EFI is new to me, just trying to get an understanding of it.

I heard that when you slowly increase throttle, the A/F ratio will lean out some, but when you accelerate hard, it gets richer, is this correct? ( I heard this about EFI in general, not specific to sleds) How much does it change?

 

[Bigwin]

This is a great thread, All eyes and ears..

 

[SledFreak]

and so is RTX Meirda avatar.....

 

[AIRWOLF]

and so is RTX Meirda avatar.....

I TOTALLY AGREE

 

[170plus]

at wot the efi goes richer or leaner according to the air temp in the airbox,colder air,richer efi,warmer air the leaner it goes,the adjustments you make on the pod have no effect on the wot running

 

[Bigger Hammer]

Ok below WOT, or more specifically below 7000 RPM, is the air fuel ratio around 12.3:1 stock? Or is it a little leaner (13.0-13.5:1)? I have not had a problem, but have heard of some people having a flat spot when they nail it. I realize that stock I have no control over the fuel mixture above 7000 RPM.

 

[170plus]

if i remember correctly,when we checked mine with the exhaust gas analyzer that stock was like 14.5 to 1,we set mine up at 13.2 to 1 which only raised the numbers on the pod by only 4 or 5,when we run the cylinder up 10 or 12 points on the pod,it was down below 12 to 1 so probably too rich for stock airbox,i havent tried any more adjustments since i put the holes in my airbox cause it never has bobbled at any rpm

 

[RTX Meirda]

OK I went out to the lake today!

I closed all of the air openings that I have added.

At WOT, the sled is 12.1 to 1 air fuel ratio. (-8 degrees C)

When I uncover my 6 bulls eyes and 2 TPI valves, The ratio is approx 12.6 to 1.

The sled feels much snapier with the airbox open. I couldn't find anyone that wanted to race me today, so I can't tell you which is faster. (I set the suspension past max transfer, once they saw me launch....no one would come near)

 

[87gtNOS]

OK I went out to the lake today!

I closed all of the air openings that I have added.

At WOT, the sled is 12.1 to 1 air fuel ratio. (-8 degrees C)

When I uncover my 6 bulls eyes and 2 TPI valves, The ratio is approx 12.6 to 1.

The sled feels much snapier with the airbox open. I couldn't find anyone that wanted to race me today, so I can't tell you which is faster. (I set the suspension past max transfer, once they saw me launch....no one would come near)

today I learnt that you should close the TPI's when spraying nitrous...or it sprays right out the side of them...still gained me 20mph hehe...