Dyno'd lean....should I be worried?

[thapr3dat0r]

Had the GT500 dyno'd on Saturday. The pulls were looking ok in the high 11, low 12 range. Then towards the very top end, it hit about 12.8-12.9 :uh oh: I also thought it dyno'd kind of lean stock (can't remember exact #s). Both stock and Saturday's A/F curves were identical, peaking up top, with the one on Saturday just being higher overall. o2 sensor was put in the proper bung at front of car.

Mods:
FRPP 113mm Intake
2.65" Pulley
VMP Tune
Catless X-Pipe
L&M 66mm Throttle Body
NGK TR6 Plugs

Should I be worried? Thinking I can ask Justin to add some fuel.

 

[03MUSCLE]

Best to be on the safe side and give up a feww ponys!!

 

[Bad500Chris]

Time to dial it back a little bit. or setup the rev limiter a little lower.

 

[DRock9]

I would not push that car until you get it fixed.

Sure it says 12.9 on the dyno which might not be awful but on a colder day it could spike up to 13.5 or even higher which would result in very high combustion temps and possibly frying your rings or putting a hole in your piston.

 

[Proto]

COTs on or off? You could either add fuel (4-6%) in the WOT a/f menu in your SCT, or if i remember there's an a/f by rpm window menu. Add fuel in the top end.

Make another run and have someone check fuel pressure. Had this issue with a friends 5.4sc harley f-150. Fuel pressure dropped down the 40psi on the top end. Problem was a clogged fuel filter.

 

[Van@RevanRacing]

Sounds like an old A/F meter or it is actually lean and you need a tune. That lean at WOT would have some audible detonation on 93-91 octane.

Van

 

[Robertt305]

Kaboom !!!!

 

[VNMOUS1]

Yes, sounds odd. Can you get your dyno guy to shoot me the run files to take a look at? I don't suppose that the car was datalogged as well was it?

In the meantime, use your handheld and add 2% fuel at WOT.

Email sent to you.

bj

 

[Van@RevanRacing]

Yes, sounds odd. Can you get your dyno guy to shoot me the run files to take a look at? I don't suppose that the car was datalogged as well was it?

In the meantime, use your handheld and add 2% fuel at WOT.

Email sent to you.

bj

Without a datalog with pedal position and gear it can log a higher A/F and then suddenly, it looks lean.

Something isn't right. We both know with that A/F the engine would have audible detonation.

12.9 on C-16 is lean. Something isn't right here.......just my observation.

 

[Shaker1]

I had something similar before I added my pulley and new tune. With a tail pipe sniffer and factory cats it was showing almost 13 A/F from 3500-6200. Never heard any detonation in 2 years that I ran that tune. Need a new dyno with the pulley and tune to get new numbers. I am tempted to add fuel at WOT, but everyone said it must be a bad reading, due to no detonation???

Anyone suggest a good tuner in northern Illinois?

 

[zporta]

where did you get your car dynoed? If the shop/ operator wasnt concerned you should have smacked him. Or if he didnt let off immediately after the a/f started to spike. I know you are in VA and if i were you i would check out Horsepower by Hermann. I tuned my car previously with the stock blower and 2.6 upper, it was pretty much spot on. Or you can get a remote tune from Lund (very happy with his tune). Regardless you need to do something

 

[thapr3dat0r]

Time to dial it back a little bit. or setup the rev limiter a little lower.

Although my tune has the rev limiter set higher than stock (6500 IIRC), I'm pretty sure he only ran it up to 6000.

COTs on or off? You could either add fuel (4-6%) in the WOT a/f menu in your SCT, or if i remember there's an a/f by rpm window menu. Add fuel in the top end.

Make another run and have someone check fuel pressure. Had this issue with a friends 5.4sc harley f-150. Fuel pressure dropped down the 40psi on the top end. Problem was a clogged fuel filter.

Cat over temp? No, I don't think I have it turned off as I keep getting the cat inefficiancy CEL. Justin sent me the updated tunes to turn them off but my PC died and all I have is my Mac (no love for the SCT) so I can't load them. I'll send them to my buddy. I sure hope it isn't a clogged fuel filter, it only has 17k on the odometer. But I suppose it's possible. I want to datalog it but am afraid to grenade my engine now.

I would not push that car until you get it fixed.

Sure it says 12.9 on the dyno which might not be awful but on a colder day it could spike up to 13.5 or even higher which would result in very high combustion temps and possibly frying your rings or putting a hole in your piston.

I usually don't redline it, I flog it even less now that it's not my daily. It was a pretty cold day so I'm hoping it won't get any worse. It was around mid 50's.

Sounds like an old A/F meter or it is actually lean and you need a tune. That lean at WOT would have some audible detonation on 93-91 octane.

Van

I did question the accuracy of the A/F meter but my buddy's GT500 on the same dyno seemed to have normal A/F levels. I didn't hear any ping and I'm sure the tuner would have said something if he heard some. He was going to shut down the pull early because of the A/F levels but let it go. He said he had to shut down someone else's GT500 because it got into the 13s. I was on fresh 93 octane.

Yes, sounds odd. Can you get your dyno guy to shoot me the run files to take a look at? I don't suppose that the car was datalogged as well was it?

In the meantime, use your handheld and add 2% fuel at WOT.

Email sent to you.

bj

No, unfortunately it was not logged. That would have been a good idea, though. I'll do that next time. I will contact him for the files. He gave me a print out of the dyno that focused on the A/F lines. I will post that in the meantime.

I had something similar before I added my pulley and new tune. With a tail pipe sniffer and factory cats it was showing almost 13 A/F from 3500-6200. Never heard any detonation in 2 years that I ran that tune. Need a new dyno with the pulley and tune to get new numbers. I am tempted to add fuel at WOT, but everyone said it must be a bad reading, due to no detonation???

Anyone suggest a good tuner in northern Illinois?

He wanted to emphasize that he put the A/F meter in the front, as I guess the tailpipe sniffer isn't as accurate. With factory cats on yours, it would probably be even less accurate.

 

[thapr3dat0r]

where did you get your car dynoed? If the shop/ operator wasnt concerned you should have smacked him. Or if he didnt let off immediately after the a/f started to spike. I know you are in VA and if i were you i would check out Horsepower by Hermann. I tuned my car previously with the stock blower and 2.6 upper, it was pretty much spot on. Or you can get a remote tune from Lund (very happy with his tune). Regardless you need to do something

Thanks Zach. I got it done at Excessive Motorsports in Manassas VA. He is really good and knows his stuff. He was concerned. He had to shut down the first pull because it spun on the dyno. Then he ran it again and it hooked. He noticed the climbing A/F and was going to shut it down if it got worse. He shut down someone else's GT500 early when it got into the 13s. I'm really hoping it's a faulty A/F meter because we didn't hear any detonation. But my buddy's GT500's A/F levels were normal. :shrug:

 

[Robertt305]

If its spinning in the dyno at your power then he obviously doesn't know how to properly strap a car down....

I'd bet his wide and sensor is toast cause at that AFR on pump gas and RPM you should have seen a rod up close and personal ...

 

[thapr3dat0r]

If its spinning in the dyno at your power then he obviously doesn't know how to properly strap a car down....

I'd bet his wide and sensor is toast cause at that AFR on pump gas and RPM you should have seen a rod up close and personal ...

Would cold tires cause it to spin on the rollers? He didn't make any adjustments or tighten it down before he did the next pull right after which hooked.

 

[VNMOUS1]

Just heard from him this morning. Didn't load the tune we sent for off-road X. That in and of itself will make it more lean.

And yep, Van, without datalogging it's a "guesstimate ".

We'll get him to load the correct tune, toss in some Torco for head room and go to another facility. The wrong tune is one thing, but to not have any detonation at all under that condition is unlikely .

Bj

Sent via Tapatalk from my MoPho

 

[Robertt305]

Would cold tires cause it to spin on the rollers? He didn't make any adjustments or tighten it down before he did the next pull right after which hooked.

I've dynoed my car on cold tires without a problem and I'm on 410's and a KB 2.8 with 20 psi .....

I trailer my car to the dyno so it's off the trailer then a idle warm up and let her rip..

Either way I'd go to a diffrent Dyno like BJ said...

 

[Robertt305]

Torco FTW !!!

 

[thapr3dat0r]

Just to be clear, I wasn't in any way trying to imply the tune is the issue. My buddy has the same tune on his car and he hasn't had any problems. Chris at Excessive even admitted Justin's tunes are great. I personally think it's my car (high A/F stock) or the A/F reading on the dyno.

I'm going to load the correct tunes and do a datalog. Does the SCT log/monitor the factory wideband?

 

[thapr3dat0r]

Updated OP with dyno graph