What AFR to aim for when running closed loop?
Turbo Mini Forums

On a forced induction engine what AFR do you aim for for performance & safety?

Team www.sheepspeed.com Racing

i was told (by a tuner) between 11.5 and 12.5 but dont quote me wait for others to reply

"Tuning should be a compromise between what is possible and what is necessary"

10)Thou shalt always quest for more power

i thought stoich was 14.7:1, is it different for FI engines then?

Stoich is 14.7:1 whatever but does not give maximum power.

Maximum power is at about 12.5:1, but you may want to go to about 11-12:1 to get a bit of extra cooling.

Depends on ambient and the effectiveness of your intercooler.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Paul would you run it 11.5 accross the whole map?

Team www.sheepspeed.com Racing

My AFR map is about

15.5:1 at 0.6Bara and below.
14.0:1 at 0.8Bara
12.5 at 1.0Bara

I would go to 11.5:1 above 1Bar boost. That sounds safe to me.

No liability accepted from damages caused by the above

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Edited by Vegard on 6th Feb, 2009.

All this bollox confuses the shit out of me

Dave

I seriously doubt it!

The Milton Keynes Map must rate as the most confusing in the world, so I'm not surprised.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Is it possible to have it at 11.5:1 just under wide open throttle?

Jim,

Just make sure that the AFR map has full authority over your VE map.

With MS, the AFR map has limited authority so if you lose your wideband then the VE map will limit how far it will shift the AFR. The is set at 15% by default, but is adjustable.

Edited by Paul S on 6th Feb, 2009.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

when my car was first tuned if you can call it that they guy "set it up at 9.5!!!!! (muppet)

"Tuning should be a compromise between what is possible and what is necessary"

10)Thou shalt always quest for more power

My Map is there, but since changing the intercooler a few years back it has always been very rich. I have since AFR around 10.2 when running over 2 bar boost, so I'm confident that if I run closed loop I'm not going to do damage (no more than running it in open loop anyway) I'm booked in for a mapping session on the 20th so this is just a short term tweak.

My Map is currently set to only adjust 15%
I've attached my setup screens
Anything I should change on here?

This is how it is currently?

Attachments:

70.55kb

177.28kb

Team www.sheepspeed.com Racing

I would not rely on TPS for AFR closed loop on a boosted engine.

Having said that, the maximum adjustment it can make to your VE map is 15%. So if you are running 10.2:1 on open loop, then that map will reduce the fueling by 15% because the target is much higher.

15% less fueling on 10.2:1 will give......

12:1

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

i wouldnt ever run closed loop under full throttle, to much chance of a £60 sensor fucking a ££££ engine.

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

Hi Jimster,

I am running 11.5 AFR on high load/high boost conditions. I would not go over 12,0:1 AFR on cond. like 5000+ rpm and full throttle.

I would also allow closed loop only when cruising....never on boost!

Why is your Map based on TPS% and RPM on a boosted engine???

If you want I can send you my target AFR Map next week....

Bimmer Twinky headed and turboed A-Series:
http://www.minifreunde.at/harry/projects.htm

Seems like what ever you have adjusted has worked from the figures! Lol What did you set it to in the end?

Im running closed loop throughout the whole map and have got it set at 0.85 lambda throughout. Closed loop should be safe as long as you limit the fueling correction the ecu can make.

https://www.facebook.com/pages/Fusion-Fabri..._homepage_panel

www.fusionfabs.co.uk



1/4mile in 13.2sec @ 111 terminal on 15psi

you run 12.5:1 part throttle and cruise?

i run 12:1 full throttle on boost. 12.5:1 full throttle off boost,and from about 70kpa(gauge) to total vacuum i run just lean of stoic, enough to give good economy, but not enough to geenrate missfires and a wee bit of interpolation inbetween. above 1.2 bar i let the afr's drop down to 11.5:1 jsut to be on the safe side. below that boost level teh car feels notably more sluggish with the extra fuel.

EDIT and idle around 13:1 due to injector limitations. any leaner and it starts to miss as the ajustment is too coarse with my old ms1 cpu.

Edited by evolotion on 8th Feb, 2009.

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

The emerald uses rpm vs tps as a base map, it then scales this map in 3D with a separate pressure compensation table.

Works really well, as it self compensates for boost against the base map.

WWW.FORCE-RACING.CO.UK PLEASE CLICK HERE

Of course Carl knows this too..!!!!

lol Carl

I liked how Carl was right in there when the mechanical bits were going on with the hubs, then stood back when the computer came out Its black magic, I tell you!

Talking about what AFR to run, LMAO we had a few running off the scale rich saturday Its amazing what an air filter can do Make More Smoke!

There should be no real reason to run bellow 0.85 lambda. You have the power to control both the fueling and the ignition more acurately than a carb and clockwork dizzy so there should be no need to overfuel past 0.85 lambda unless the engine has not been built to take the desired boost levels

I run closed loop at full throttle, as the rich and lean correction limits are set to 10% respectively, and the fact that the WBO2 controller is built in, the ECU knows when to ignore silly readings, which is more than can be said for any ECU that requires an external WBO2 controller

How oftenn do Lambda sensors die when they are controlled correctly and the engine is in good tune? Production cars and the same sensors run for years and tens of thousands of miles. Its hardly going to die within 3000 miles.

The DON is probably running Alpha-N with MAP multiplication due to the wild profile of the cams which would cause poor MAP signals in the lower RPMs so it uses a combination of both.

I did run closed loop for the shoot out, through the whole range, but we did keep an eye on the AFR with a second sensor just to check everything was as it should be, fueling did seem to be spot on. These are the settings I used

Team www.sheepspeed.com Racing