mike1986fyrbird

Here the deal;

Air-fuel ratio in first between 3000-4000rpm is 12.5 then dips down to 12:0 after 4000~rpm.
Air-Fuel ratio in second between 4000-6000rpm is 12:0:1~
Air-fuel ratio in third between 4000-4600 is 12.5:1~

What gives? Why is it leaner in third gear?
I've been trying to adjust the AFR by using the PE enrich vs. RPM table. I'm assuming I can't do this and I need to adjust the MAF table because of what is occuring.

The Mass air flow grams/sec at a specific rpm in first and second is pretty much the same. In third gear at the same RPM the maf grams/sec is lower.
For example;
First and second gear at 4300rpm is 225grams/sec
Third gear at 4300rpm is 215grams/sec

I have not logged higher then 4500rpm because I don't feel like going faster then that on the highway..

Am I going to have to adjust the MAF tables to match the commanded AFR and then go from there so AFR is the same in every gear or am I missing something?

Thanks.

91L98Z28

are we talking about an ECM calculated AFR?
a measured (WBO2) AFR?
a guessed (NBO2) AFR?

I'm not a MAF guy but I believe PE AFR vs. RPM is indeed where folks add fuel when they max the MAF, so you should be able to achieve a change in AFR from this table.

reasons for AFR and MAF flow differences could be many, for example are you getting knock counts in third, that could be retarding the timing a few degrees, which also would lower your MAF flowrate and alter AFR readings (if you're measuring with a WBO2)..

mike1986fyrbird

I can achieve a change of fuel using that table. The problem is, third gear is leaner then the rest.
I am using a wideband 02 and there is no knock retard occuring.

Anyone know why this is happening?
Thanks

mike1986fyrbird

Any ideas? No one has came across this problem before?

RednGold86Z

iTrader: (1)

Does your ECT go up enough to change the PE vs Coolant Temp?

What does the "commanded A/F" do? Does it match the actual?

its scot

I get some variation in diforent gears also. I just atributed it to diforent load on the motor and I have a ram air setup that can make it leaner at higher speeds. I found that if I hold the brakes on at a target rpm say 3000 then let up to 3500 then 4000 ect. I get very consystont A/F raeding this has helped a lot with my tuning. you can make a loner graph at each rpm in stead of say 1000-6000 rpm in just a cuple of seconds.

mike1986fyrbird

Alright i'll try that out tonight.
No, my coolant doesnt raise enough to change the modifier. It went from 182* to 189*.