Hey All,

I'm trying to understand what type of Air to Fuel ratio I would want to aim for on different boost/rpm levels.

This is for:

V2 Supercharger @ 14psi
Meth Kit starting at 5 PSI
EMU for tuning
Greddy pressure sensor

I have read around and got what A/F to aim for at cruise, under boost etc. I just don't know when to aim for those A/F (mainly in boost or getting into boost) at various RPMs. In my tune once it goes into boost it goes straight to 11.5 A/F to be safe. But should I transition it at different boost levels as 11.5 may be to rich at certain boost levels?

I will be using my Greddy pressure sensor to make myself a new map. Any information on how to scale this would be great. I have found this link which shows the conversion from Voltage (Greddy pressure sensor) to PSI. Can someone confirm that its the one to use? IE proper conversion.


I'll make myself a map tonight showing different A/F that i'll aim for when I tune the car. I know a lot of it is feel and how the car responds but my big problem is getting those A/F's correctly at various boost/rpm levels.

Also if anyone has any current maps that they are using and don't mind sharing that would be great! It will give me a sense of what needs to be done.

Thanks, I will post my I/J map with my scaling and the A/F ratios I think I should be getting.

 

I would have to think something in the low to mid 12's would be fine when your around 1-5psi. I am currently tuned to 11.1-11.5 at wot with a front mount

 

If it were me, I would just leave it at mid 11's where you have it as soon as it goes into boost. Its a good afr, not too lean not rich, just perfect. If you aint knocking 12's gives you the most power from my experience, but if you wanna be safe, leave it at 11s.

 

This is what I just made. I used the voltage levels to pick what the vacuum/boost would be in terms of PSI....This is just rough values from what ive read. Any comments? suggestions? By any means no one should use this, its just to see if I'm on the right track...

Also are my voltage to psi levels correct? is this the proper scaling for the greddy pressure sensor? Thats my most important question.

 

Its going to be hard to be precise without actually seeing what the change in values does, meaning without being on a dyno.
Using AFRs to street tune does work, but its really hard to say what AFRs are the correct ones per boost level, timing plays a big part in this as well.

 

and as I've noticed feeling of how the car responds. J&S is in the works for timing. I've played around and I'm happy with my results so far. The A/F target really helps out, I just have to fine tweak it now and remove some flat spots in the tune. I'm crusing at 15.5 A/F a tad bit higher, it feels smooth and I'm probably getting my best gas millage :0

 

The J&S will pull timing as needed, but it wont tell you where the most power is being made.

 

That is correct, but ill be able to get it to a point where I’m on the edge with timing. Then I'll dyno it, see where I'm at and make adjustments according to torque values that I get.

To be honest, I’ve ran Stock timing without any adjustments. I've only adjusted my A/F and had meth help along. The car always pulled. If **** hits the fan, I have another motor on the side waiting to go in. At least with the J&S ill get assurance that I don't have a knock and be able to play around with timing comfortably.

Dyno will be done within October. Then it will be time to put her to sleep for the winter.

 

Alright well, I tuned the car and lets just say I have a smile on my face. For once my tune went just as planned. My cruise is around 16 A/F (no hesitation from the car), you press the gas a little it richens. As it goes through 0-6 PSI I have it go from 13.5 to 11.5 in steps. It accelerates like a crack head. I got torque steer in second going to redline with my 245/45/18 rims, that was fun! My A/F ratios was a flat and I mean flat 11.1 across the board going to redline. It can be tweaked a little more but for now, I gotta say I like my tune.

BTW I'm still using stock timing,no adjustments at all to it. My J&S is on its way so we will see if I'm knocking. I do have meth which I believe is really helping out.

From 0-6 psi timing is at or getting to 17 degrees, from then on it goes up to 25 degrees @ 12 PSI.

Might be to much timing...That will be answered when I get my J&S...It's almost winter time so if it craps out on me, well I have another motor that's ready to go in. But you know what, if timing was off and I was knocking I would have blown this motor by now. I have been running it all summer long. I did a good 30 passes at the drag strip. I sure as hell wasn't easy on it. In any case timing control is on its way!!!

Hope it holds together

 

12psi from a SC + stock timing + meth + 93octane (I hope). Id say you are pretty safe, ofcourse every car is different so you never know, but you shouldn't be knocking with that setup, specially at 11.1afr. This is a 3.0 right?

 

What do you run at the track

 

I'm running on 94 Octane and with an inercooler. At the track my best was 14.3 @ 105 MPH 2.3 60 foot on street tires. Going tonight with slicks.

 

Alright went to the track...

After figuring out that my Meth was causing spark blow out in first gear we got a good run, well better run.

So the last run of the day before it rained we got a 13.814 @ 103MPH 60 Foot was 2.067. Again Meth was causing a small issue but its way better then my previous 14.3. There is a good 13.6 run for sure.

I have a question about Meth now. Before I had it start at 5psi and went full blast at 14 psi. Seeing that when I launched the car at the track in first gear it would cause spark blow out at 5500RPM. So we increased the starting at 8PSI and it was fine. Is that safe? When should I have the Meth kick in? My spark-plug is gapped at 0.26-0.28 I beleive. Should I re gap them? and if so to what? I lowered the gap before because my Meth was causing spark blow out but I had a bigger injector.

So i guess the question is, what should I gap my spark plugs at? its probably my issue.

Id like to start my Meth at 3-5 PSI to keep it safe.

Thanks

 

Between running 94octane a intercooler and 11.1 a/f you'll be fine setting meth to spray at 8psi. Remember your target a/f with meth is different than on gas. Now if you had a turbo and could hit 8psi at 3000rpms on stock timing that would be a problem and I would suggest bring in meth sooner. Remember alot of guys running the amount of meth you are don't have a intercooler

Also your trap speed is alittle low and that tiny gap is not helping. I would tune the car to 11.1 on gas and high 11's when meth kicks in and this should resolve your problems with the blow up and allow you to open the gap alittle gaining power and mpg.

There is alot of power untapped on your car, congrats on your time and good luck next time you hit the track

When you install your J&S you'll that the car is not knocking

 

Alright so when Meth kicks in I'll make sure its 11.5 A/F maybe a bit higher. Without the Meth ill go with 11.1.

So

1-6 PSI will be 11.1 A/F
7-13 PSI will be 11.5-11.7 A/F with Meth

I'll get one of those vacuum/boost testers (don't no the name) and have my Meth tested so it opens at 7PSI.

I'll Gap them to 0.32 and see how that works.

One weird thing, last night I tuned the car and it was hitting 11.1 with Meth in 3rd gear to redline. Tonight it was hitting 10.0 A/F any ides as to why? Temps where the same...

 

I would not suggest making alot of changes at one time tune the a/f 1st remember these are ballpark #'s you maybe able to lean out your 1-6psi a/f alittle more but I wouldn't go beyond 11.5 on gas and 12.0 on meth without dyno testing to confirm what a/f provides the most hp or something to test for knock.

Also what rpm do you start to see boost and when do you hit 8-10psi

And I would regap the plugs last make sure everything works 1st and car is no longer bogging then slowly start opening your gap

 

The bogging was caused due to the Meth, I believe 1st gear goes to 7 psi and around 5500rpm that's when the Meth kicked in and made it seem my redline was set to 5500. Then I let go of the gas and went back on it.

I'm going to put back the Meth back to its original setting IE starting at 5PSI, once I get my coil booster I'll gap the plugs higher and go from there.

I'll also check my exhaust for any leaks because I can't understand why the A/F went from 11.1 to a flat 10 in 1 day. They where both check on a colder night so I don't understand.

 

not sure what would cause the a/f to change so much, got to think about it

So I am guessing the car drives fine without meth, I would tune the car on gas a add meth as needed

 

if your max boost is at 13psi, you should be fine starting to spray at 8psi (actually, you dont even need meth at 5 psi. 8psi or even 9 is where you should start spraying it), I was nonintercooled at 10psi with meth turning on at about 7psi, no issues, stock timing (back when it was 3.0). Now my question is, what size nozzle are you using, you could possibly be using a nozzle that is just too big hence why it bogs when you spray at lower boost. How much does your AFR drop when you spray the meth? for example if you do a run without meth, then do another run with the meth, what is the difference between the two afr's? I have always read that if your afr drops more than 1 point, then your nozzle is too big. I am willing to be this could be your issue, and not spark blowout.

Edit: my guesstimation is that you should be using a 3 or 4gph nozzle.

 

The nozzle I have is spraying at 130ml/min. That's not a lot but it blows the spark in first gear.. Not sure what the A/F drops by with meth...

 

Belt decided to skip a rib today. The belt was fine so I put it back on. tightened everything and noticed that the tensioner pulley wasn't sitting right. I hope nothing bad has happened but with my luck usually something does happen. Will check it out tonight...

 

Supercharger up and running again. Will need a new belt, but I have a spare. Just the pain to remove it >_<, J&S on its way + my coil-boosters. Next Saturday will be the last day for the track! hope I can make it!