Tuning concerns/questions

I'm not new to getting 11-15 Mustangs tuned, but I'd like some thoughts on this latest deal. I have tunes from 2 tuners(no names...lets call them tuner A and tuner B). Both are very well known and very well respected. I know that both of these guys truly know what they are doing.

Tuner A datalogging shows routinely -2 degrees of knock indicating a very safe tune as the PCM is adding timing. My fuel economy over stock and compared to tuner B is dismal. So, it's also pig rich. I know all the emissions controls and cat over temp protection are in place. In general, this is a good tune.

Now, tuner B. My datalogs show +3.5 degrees of knock. At WOT, starting around 3500, it starts at -1 degree and steadily climbs +1.5, +2....all the way to +3.5. It feels 30-50hp stronger than tune A. Drivability, part throttle cruising/responsiveness are better. Not a ton better, but it's noticeable. Fuel economy is also 3-4mpg better. I sent tuner B my logs and he said he'd be surprised if it was actually 3.5 degrees. He said to go out and make a couple more runs and then send him a pic of the plugs to see what we are actually getting.

Now, does that seem like a fair request? My gut tells me that worst case, if I am actually getting 3.5 degrees of knock, those 2-3 extra pulls ~could~ scatter this motor all over the highway. Is that enough that I should be concerned about for a couple of pulls? It would seem to me that the PCM seeing +3.5, even if it is being liberal with the readings, indicates that tune is right on the ragged edge. Meaning, that if I get a tank of bad gas in 6 months, it could be great until then...and then boom! To be fair, he said that he could pull some timing out of the tune if it actually is knocking. So, what are my risks with 2-3 more pulls with that much knock...if it is actually that much?

Personally, if it's my street car, I go with the safer tune that's getting no knock compared to the tune that's getting 3.5 degrees of timing retard. Margin of error is good.
If you're curious, you could also ask each tuner for the timing tables and how they're adding/removing timing etc, to compare. There's obvious discrepancies between the two tuners and how they're approaching the tune of your vehicle.

Have you compared how much timing the PCM is commanding in both tunes? Have you ruled out crap gas as a contributing factor? I wouldn't have a problem making a few more logs, but I surely wouldn't go for a full WOT pull through the gears. If it's pulling that much timing at WOT, it's probably pulling timing if you just get a little aggressive in your drive. If you have the ability to take a couple degrees out of your timing in the user defined settings, you could try that too. But to run it through the gears at WOT, I wouldn't do it.

For a street car it needs to be a soft tune on top. Why risk it and pull the plugs when your motor is toast? There are too many uncontrolled variables(i.e. bad fuel, weather conditions, altitude)that can hurt the motor if the tune is set aggressively.

Put some 100-octane in your tank, datalog with the more aggressive tune and see if you can duplicate the amount of knock you've already seen. If not, it is true knock. If it is, it's false knock.

Thanks peeps. Pretty close to what I was thinking too. The 100 octane wouldn't be a bad plan either...but I think I'd always worry that I'm right on the edge of destruction.

I would go with tune A and maybe see what tuner A says about your logs.

If it's too rich you could also get cylinder wash which isn't good either.

After dealing with various tuners I went back to a Ford Racing tune/blower... just more piece of mind for me personally.

I'm in Austin too BTW

Cool yea. Since tune A is so solid, I don't mind saying it's a Lund tune. My only complaint really is that I think it's a bit rich(mileage). But I totally signed on for shitty mileage when I bought the car so oh well. But, I'm 100% confident it's safe. For my street car that will never see a track, giving up 30-40 horsepower seems reasonable for extra peace of mind.

@Imatk Ever go to cars and coffee at the Oasis?

Yeah I try to make it there every now and again. I have a gray '07

I've been meaning to go. Just never made it out. Next time you go, hit me up.

Will do!

FYI, Lund uses the following A/F ratios in his tunes for the GT500:
11.5 for 91 octane
12.0 for 100 octane

jchristena said:

Cool yea. Since tune A is so solid, I don't mind saying it's a Lund tune. My only complaint really is that I think it's a bit rich(mileage). But I totally signed on for shitty mileage when I bought the car so oh well. But, I'm 100% confident it's safe. For my street car that will never see a track, giving up 30-40 horsepower seems reasonable for extra peace of mind.

@Imatk Ever go to cars and coffee at the Oasis?

Click to expand...

Do you mind PM'ing me who tune B was? I just bought a 2014 GT500 with 3k miles on it and am looking to get my tuned. I want to make sure I don't go down tuner B for a street driven setup.