carb tuning help - afr logs included

[Corty]

hi all just after a bit of info in which way to go next
here are 2 flat out wide open throttle logs from about 10 mins ago

the afr need to drop a few poins would ideally like to see 12.5 not 13.0

also when cruising and the turbo spools it goes lean ,
at present the carb is
standard 1st stage
2nd stage is 1.3mm
main is 1.3
and the a/c is 1.0mm

i can get good afr on idle
ive removed the dump valves and plumbed the boost reading at the lower part of the manifold

the inlet temp is on the intercooler pipe just before the carb lobster

which should i look at adjusting next
first stage? as its lean on cruise /low psi
or increase the second stage to 1.35/1.4mm
or do i look at reducing the a/c to .95mm






cruising log ----



thanks in advance
Corty

[Alex]

I can't see the logs due to my crap work computer

What boost are you running? You should aim for 11.5 - 12.00 @ WOT. 12.5 is a bit marginal. I'm running a very similar spec to you and I get late 11's/12.00 @ WOT. That's at 15psi at the manifold.

To richen things up try dropping the A/C to 0.9. You can take the 2nd stage to 1.4 max.

[Trevhib]

Can't help I'm afraid but those logs are super cool.

[Corty]

thanks for the input alex
im running around 13psi
the engine is built for more like 22psi but i like to have a marginal safe zone and only want the extra boost when i need it (so not yet)

so dropping the A/C jet has an input on the boosted afr value
is there any point in increasing the first stage? & will this have a knock on effect to the rest of the fuel curve ?
or when it swops to second stage will the first stage jetting be non apparent.

at least i know i should be aiming for a richer afr than what i was originally thinking
so ill get it down to 11.5- then increase the boost till i see 12.0:1 AFR


super happy with the Ktec intercooler tho - its 23*C intake at 100mph wot and 13psi of boost from the ktec 180 turbo on a closed private road of course .

[Alex]

Reducing the A/C makes a big difference to the fuelling, my car didn't like a 0.9 jet so I put a 1.00 in and it's happy with that. I would tend to leave the 1st stage alone, certainly at your current boost level.

This might help if you've not already seen it

https://www.rtoc.org/boards/showthread.php?t=4734

[Fordy]

reducing the 1st stage to lean fueling in the slow spool up area can make the engine feel crisper

11.8-11.5 depending on a few factors/spec @ 6000-7000rpm in 4th/5th is good fueling

[Corty]

right
ive been playing with the ac jet today
seperate logs when dropping sizr by .05mm each time started at 1.15 then 1.10 then 1.00 as didnt have 1.05 drill handy

it dosent seem to be making much difference at all
so i increased the second stage from 1.3mm to 1.4mm

just gone for another session and its still giving the same readings thus has had no effect


should i look at increasing the main ? thus upping the fuel throughout the entire curve ?


im guessing i have a std cam - could this be holding me back?
all valves clerences done .20 inlet
.25 exhaust , measured top of lift with dial indicator so i had true top of lift too

i have another carb that i could try but dont think this will improve things

any other thoughts anyone??

[Corty]

[francob80]

Are you running an adjustable FPR ? Perhaps adding more fuel into the mix will help ? Pretty certain you should be aiming for low 11s, 13 on your logs seems too lean. Or have you considered trying another AFR gauge as your software/AFR might be giving false readings.

[turbo ted]

Before you did any tuning to the carb did you clean the fuel sender in the tank if its any way dirty at all it will run lean everywhere on boost off boost.

[Corty]

yep stripped cleaned and reinstalled , also new fuel filter added at same time , fuel pump removed purged and then refitted


will try the other carb when i get home at 2pm , see whats occuring
(cheers for the input) - ill prob check again just to be sure

[Corty]

Are you running an adjustable FPR ? Perhaps adding more fuel into the mix will help ? Pretty certain you should be aiming for low 11s, 13 on your logs seems too lean. Or have you considered trying another AFR gauge as your software/AFR might be giving false readings.

hi mate im running std fpr
i have a gauge in the car linked to the carb inlet circuit and it reads around 3-4 psi above boost so im led to believe this is correct ie 15psi = 19/20 psi fuel pressure

the afr reading should hopefully be legit' as they seem to be the same readings for the same stretch of road and the same day - so the temp hasnt changed

on my old exhaust i had it around 12.8 afr and it went like a banshee , so id say that was an as expected afr reading and power produced - ill get another wideband kit from a different supplier hooked up to the end of the exhaust (as mine is 6 inces from turbo) and compare the logs.

good old renault - never a dull moment - i can drop a carb off in under 5 mins now lol

[Alex]

Before you try that 2nd carb do a fresh air re-set on the lambda sensor - it won't cost you anything so is worth a try. Seems weird you're running lean with that carb spec/boost?

[Corty]

and how do you do a fresh air reset?
remove the probe from the exhaust pipe and let it go all the way to 21AFR?
or is ther a special super secret hand shake?

the unit does a test set up everytime i start as its plumbed into ign live
but worth a try i guess!

[francob80]

I still think 12.8 is too lean. Reading various threads on here I believe you need to be richer still.

[Alex]

and how do you do a fresh air reset?
remove the probe from the exhaust pipe and let it go all the way to 21AFR?
or is ther a special super secret hand shake?

the unit does a test set up everytime i start as its plumbed into ign live
but worth a try i guess!

I forget now but it should be in the manual. I have an Innovate set up and I think you unscrew the lambda and turn the ignition on for a certain amount of time. And repeat possibly. Something on the lines of that anyway.

[bigdavec1974]

If you have the lm-1
http://www.innovatemotorsports.com/s...LM1_Manual.pdf

[Corty]

rite tried 2nd carb and its dangerously lean
so its off again
ive increased the main jet to 1.35mm
this dosent seem to have made a huge difference to the fuel curve

running 1.00a/c (about 0.95-1.00) as its drilled not reamed out

i noticed that when i give it a little choke the afr comes into where i want it 12.5s or lower depending on the amount of choke

ive cleaned the fuel sender in the tank and the fuel pressure is rising about 3-4psi above boost so guessing thats ok too

im guessing its not getting the fuel it needs on WOT

should i look at increasing the main jet further 1.40mm /1.5mm ?

or could it be a dodgy knock sensor or something else ?

i am using a ktec 180 turbo so im guessing this is flowing more air than a std turbo at the same pressure - more air = leaner mix = more fuel needed?

[turbo ted]

You may try opening up the needle jet a bit to 1.9mm but the jetting you done already should be loads should fuel 22psi easy have got phase1 fuel pump or a updated pump as the standard phase 2 pump is not up to the job

[francob80]

Not set mine up yet but as far as I can tell running an adjustable FPR like a Malpassi will ensure you get enough fuelling at WOT. But if you are struggling for fuel at only 13psi then have you considered uprating your pump to one with a higher flow?

[Alex]

Theres something funny going on here, you should easily be able to fuel 13psi with that carb spec, in fact it should probably be overfuelling!

I would try doing that lambda re-set. This might not fix the issue but it's worth a try. Failing that I would be checking the wiring to the fuel pump and maybe try another pump. 4 psi above boost is o.k.

[James5]

Reading this buddy I would be re-calibrating the 02 sensor if that makes no difference then trying that spare carb you have with a fresh rebuild kit in situ. To have no changes to the carb with changes to the jetting you have made shows an issue as any small change in any jet size would make a big difference with fueling.