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Discussion Starter · #1 ·
Ok, from searching and reading previous posts it looks like I will be tuning for around 11.5-11.7, is that good or is it a little too conservative. Also, what is an AF that I should be letting off of the gas when I see. On the dyno I was seeing 14.5:1, I know that was way too high. If I see 12.5:1 at a certain RPM should I let off and add fuel their. How about 13.0:1 or 13.5:1? When should I get out of the gas to be safe?
 
G

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14.5:1 is ok for just crusing. ~14.5:1 to 15.2:1 is what is referred to a stoichiometric and is what you should be varying around while cruising.

If you just have the stock ECU with some piggybacks, then when you nail it at low rpm you should see it start to come off stoich somewhere around 3.5-4.5krpm and transition from closed to open loop. In this range you should be transitioning from around 14:1 to 13:1 to 12:1 and at 4.5krpm you should drop to 11.5:1 and maintain that until redline.

I've actually had times when the AFR won't come off low stoich (14:1). It seems like it isn't transitioning to open loop. Last time this happened was when I reset my ECU. I took the car up to 5krpm and it was still at 14.1:1. I backed off. After driving it a while I tried again and it transitioned...go figure. I think my ODBII ECU needed to learn something.

Funny enough, the opposite happened on the dyno. I had some old Sunoco GT104 that had been sitting around in my garage for over a year and a half (about 10 gallons in the drum). I think it went shitty. Mixed it with some 93 to get 100 octane. The AFR was fine until I put it on the dyno and turned up the boost a little. It wouldn't come off stoich hanging again around 14.1:1. Had a little detonation and immedaitely backed off at a little over 5krpm. Reset the ECU (only change) and the AFR fell right back in place. Strange...

I made 599.9rwhp @~24psi on the shitty gas mix and a tiny fan on the FMIC (their big one was broken). Temps were 95 degrees and humidity was high also. I think a bit of timing was being pulled.

Now I'm running fresh gas with 1/3 toluene and everthing is happy. I watch those AFRs like a hawk though.

If you're not transitioning to open loop and your AFRs are still around stoich at 5krpms...BACK OFF!
 

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Where do you guys drive 140 mph multiple times to tune? I think I'd kill myself or someone else.

Adam
 
G

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I have a really nice open road about 3 miles from my house. It has no entry points for miles and will support 120+mph with minimal to no braking to get back down to 60mph.

I get VERY concerned about this. The last thing we want to do is hurt someone when hauling ass around.

Pick your tune roads very wisely. Pull off the side and wait for traffic to break if necessary. Select a long raod with no entry points if possible. This is critcal IMO. People can't judge how fast you're accelerating and will pull out in front of you.
 

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Adrocktt said:
Where do you guys drive 140 mph multiple times to tune? I think I'd kill myself or someone else.

Adam
I don't use backroads, 'cause ya never know...deer, kids, beavers, whatever. Plus tiny 45 MPH transitional bumps turn into, "jack the ass end up in the air, hella scared, ski slopes" at speeds approaching 100. I usually use a lightly traveled section of highway that is not really monitored @ 1am. No on-ramps, straight as an arrow with no place for cops to hide. That and my Valentine One hasn't failed me yet. I usually pull from 3K in 4th gear until 7K~7500 and do a lazy shift to 5th to come out of warp. Doesn't take a lot of room, minimal tirespin, and I can get some good datalogs.
For the topic starter, stroker6 has some good gouge. The only thing that I personally do different is lean it out a tad from 5500 on up (12:1). It also matters what your running for a turbo setup (as the wrong A/F can kill spoolup). Guessing by your nick, I would say twins ;). Whenever I tune, I shoot for 14.7 on cruise until 150kpa, dropping to 13:1 until 170 kpa, 12.2:1 until 200 kpa and 11.5~11.8:1 from there on up, leaning out a little up top as previously noted. If you're an Imperial kind of guy, just divided KPA/6.894 to give you the pressure in PSI (and subract an atmosphere, -14.7).

Ryan
 

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Discussion Starter · #6 ·
I'm running a 67GTQ on stock fuel and stock tranny... my nickname came about from lack of thinking on my part. Who would have though I would go single. :D

This is really helpful guys. So basically if I'm running 12.5:1-13.0 at 5K get out of the gas?

Also, I have an auto so I don't think I need as much speed as you guys are saying. Should I just be doing a 3rd or 2nd gear pull? Would 2nd gear work or would I run way leaner when I go WOT in 3rd? I would rather tune in 2nd since I don't really like speeding around too much even on deserted roads and highways.

And excuse my ignorance since this is probably a stupid question, but will adding race gas change my AFs. I would assume that it would cause the car to run richer but I figured that maybe the AFs remain the same while allowing us to run higher AFs more safely.
 

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I have an auto also. My afrs are different in 2nd gear compared to 3rd gear. In the lower gears my car runs leaner than in 3rd.


Carlo
 

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If you are tuning it on the street 12.5:1 should be ideal. With a car on the dyno 12.5:1 is running on the lean side.
 

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Discussion Starter · #9 ·
BalticMKIV, thats pretty wierd since I would think it would be the opposite. Is there a reason for that? Do all the other automatic guys see the same thing?

What do you guys think about what G said? I know people tune for 11.5:1 on the dyno assuming it is gonna run leaner on the street so wouldn't what he said make sense?
 
G

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I believe people used to say that AFRs varied a full point from dyno to road tuning, but I'm under the impession they're about the same. After I dyno'd and got on the road, my FJO read within .2AFR of what it did on the dyno, and the dyno WBO2 was about .2AFR off from my FJO. Pretty good correlations IMO.

Kind of interesting how the recommended AFR has come down about a full point in the last 2-3 years. Supra owners used to tune to 12.5:1 and would consider it safe. I personally think it is fine unless you're doing back to back hard pulls in high gears, road racing in 100 degree weather, etc...but everyone seems to think the 11.5:1 is better, and that is what you should tune to on the road.

With regard to your other question, yes, if the AFR is 13:1 at 5krpm, backoff and add 2-4% and try again until you get it down around 11.5:1.
 

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VeilsideTT- I dont think its just auto guys having this problem. Another member by the name of Spanki started a thread similar to this. Hes a 6spd and tuned his 3rd gear for 11.5:1 but in second gear he is seeing 12.4:1. I do not know if there is anyway around this problem unless you switch over to AEM.

carlo
 

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Doesnt make sense to see a leaner mixture in a lower gear. I tune cars to 11.3-7 on the dyno.
 
G

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VeilsideTT, hopefully you're not just going by the FJO. You should also be checking your plugs to make sure all your injectors are firing and they all should look pretty much the same as well as gapped the same. this might be redundant to some but you should use as many tools as you can when tuning...

Melvin
 

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Discussion Starter · #14 ·
Baltic, thats really wierd. I guess I should take a few runs in each gear and see which one runs the most lean.

Melvin, I'll be sure to check that out. I didn't even assume I could be running lean because of a bad injector. Lets just hope it was me hooking the AFc wrong since thats what seems the most obvious. BTW, sorry I didn't get a chance to call you back this weekend. I was really crazy all week and I've been running around like a chicken with its head cut off. I got that bolt tightened so i'm good to go there. I'll give you a call in the next day or two though just to see how things are going.
 

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Ryan23 said:
I don't use backroads, 'cause ya never know...deer, kids, beavers, whatever. Plus tiny 45 MPH transitional bumps turn into, "jack the ass end up in the air, hella scared, ski slopes" at speeds approaching 100. I usually use a lightly traveled section of highway that is not really monitored @ 1am. No on-ramps, straight as an arrow with no place for cops to hide. That and my Valentine One hasn't failed me yet. I usually pull from 3K in 4th gear until 7K~7500 and do a lazy shift to 5th to come out of warp. Doesn't take a lot of room, minimal tirespin, and I can get some good datalogs.
For the topic starter, stroker6 has some good gouge. The only thing that I personally do different is lean it out a tad from 5500 on up (12:1). It also matters what your running for a turbo setup (as the wrong A/F can kill spoolup). Guessing by your nick, I would say twins ;). Whenever I tune, I shoot for 14.7 on cruise until 150kpa, dropping to 13:1 until 170 kpa, 12.2:1 until 200 kpa and 11.5~11.8:1 from there on up, leaning out a little up top as previously noted. If you're an Imperial kind of guy, just divided KPA/6.894 to give you the pressure in PSI (and subract an atmosphere, -14.7).

Ryan
that's what Rt.50 is for!!!! :D :D :D

vnt
 

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Discussion Starter · #17 ·
Hmm... very helpful. How about the race gas question I asked before? Will it affect my AFs or will it keep them the same but just give me a safety?
 

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VeilsideTT said:
Hmm... very helpful. How about the race gas question I asked before? Will it affect my AFs or will it keep them the same but just give me a safety?
it'll affect it big time.

vnt
 

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Discussion Starter · #19 ·
Damn Val, everytime I see your sig I am amazed. 642/669 unlocked... please... tell me your secrets... I must know master. :)
 

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what can i say my tuner is damn good, and that's with a 3" mp/dp, and we're upgrading to a 4" mp/dp & KeithTa/Titan Intake Manifold Pretty damn soon. Paul is telling me i should run a 9.80 w/o a problem now.

vnt ;)
 
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