AFR debate
 

OK iv got a datalogit and a wideband talking to one another, Iv dun some pulls and loged data, whilst setting up excel for 3 types of data (three 20x20 cells).

1. Loged AFR
2. Desired AFR
3. Corrected fuel map

Procedure to Recalculate Fuel from Loged AFR's

1. Recalculat the base map so that INJ map in FC-Edit are all 1.00 (FC-Edit-tools-recalc base)
2. I past my loged AFR into Excel "loged AFR" data cells.
3. Performe a calculation on each cell "CELL =IF(OR(ISBLANK(B3)),1,((B3)/B27)) where B3 is the loged AFR cell and B27 is the desired AFR

This will give me the corrected fuel cell calculation for each cell in the INJ map

That said my 1st Question is what are the desired AFR for a standard engine with twins and most bolt on's.

Im guessing

Idle : 12.5-13.0
vac : 13.0-14.0 depending on power or economy
0 psi : 12.0
5 psi : 11.5
10 psi : 11.1
10-15psi : 10.0

Question 2 : Is this safe ?
Question 3 : Is this correct AFR for all rev range ?

Please feel free to state you opinion or if you would like me to exsplain further.

oh dear !!!!

I will pm you on FDUK

Scott

Dont think you will find me there ..

Also i think im not to far from the SAFE mark.

Ill go register on FDUK now i guess

First off, doing a recalc base map is a HUGE step. I wouldn't do it until you're MUCH more comfortable with the Datalogit and tuning. It's real easy to totally screw up your map with a recalc.

If you haven't done so, talk with Chuck Westbrook about his PFC tuning documents and go through them - that's a must- have if you really want to tune with the Datalogit.

Dale

You are a full point too rich on your boost AFRs. Research Chuck's many posts on AFRs for a fairly safe range under boost (on 93 octane with relocated AIT sensor). You could run a few tenths leaner than Chuck's suggestion to be more safe.

Idle is whereever it idles smoothly. Vacuum can be as lean as you can run it without stumbling if you want (14-16).

yah u need to be around the 11.-11.4 at full boost, you will feel the diference even at stock timing. PS dont fuck up ;)

change step 3 to include more samples, with your current condition anything other than a blank or zero samples will change the value for that cell...I use at least 5 samples with a very slow laptop

you may also want to limit the peak AFR recorded, since numbers in the 20's are usually a result of letting your foot off the gas, you really don't want those samples averaged in with the others

lastly always save your map prior to a recalc or making any changes

A/f seems fine. 11.0-11.5 seems to be the sweet spot.

Running 10.X is okay on 10psi+ as you still have a SMIC, and chances are your intake temps are pretty hot over 10psi.

Your vac a/f looks okay, as long as you don't have a cat.. If you have a cat you will cook it quickly with those lean mixtures under vacuum, if you don't have a cat thats fine.. might even be able to get away with leaner mix.. keep an eye on egt's though.

All of your postive pressure maps are quite fat, by about 1 afr....
However ever motor, and setup are different...

The thing to adjust with RPM is Timing, since the faster the rotor is moving the earlier you need to light the gas for the flame front to be "optimal"...

The trick here is not to light it too early has you then have pre-ignition and that will try to send the rotor in the wrong direction, and usually causes detonation type noises... allthough detonation is a whole nother issue alltogether...

Some good feedback there and i think your sugestion as to getting chuck's tutorial is a must for me.

I failed to mention that all this is theoretical as since i installed my datalogit and hooked it up to my wideband i have been doing some runs and scarde the S**T out of myself by seing 12.5 at 10psi and full WOT on some occasions, so im not driveing the car till i research this to the max and figure out what i shout be running and where.

I can see all the relationship between boost/vac with all your posts but im still strugling to make sence of it with RMP in the equasion.
Iv even considerd making my full map run at 11.1 then slowly tune from there, this may be laughable to you guys but i want to start out very safe and then i wont be afrade to WOT to log AFR's

Sugestions are all welcome as to the safest starter map.

My intentions were to save my basemap 1st then recalc .

I think i will stear clear of the base map for now as you say.

Also failed to mention i constantly run on a minimum of 98-100 octain (almost sure thats ron+mon).

I have mailed chuck and am in the process of getting hold of his notes+ .

Dont know if you just typed the wrong word but didnt you mean " richer than chucks sugestion to be more safe" as oposed to leaner.

Thanx for the help.

There really is no reason to take drastic measures like being way over rich. For one reason you may not have the fuel system to do this. If the fuel map is rich by well over 10 % you will struggle to make power. You will also have very poor economy.

There is quite a lot of room in the fuel map but i would defo not run anything richer than 11.1 at 1 bar or less.

Scott

TBH. there is no debate on here about afr on pump fuel . We all agree !

Maybe the word debate was not suitable for the questions asked but it was used in a very selfish manner, the goal was for my perposes only to start with, guess now its more of a discusion.

The differences between pump gass and race fuel are unknown to me so i cannot comment there.

I now have chucks notes+ so i guess i got some reading to do, thankfully it has a "desired afr" map, so i have a starting point.

Lots of reading and login are to follow.

Any more on the subject would be good