2k05gt

This Last weekend my local Mustang Club had a Dyno Day, for 50 bucks you get two pulls and A/F.

I had a JLT II CAI installed a month ago and I got a Canned tune from V-8 Power (where I purchased my SCT II Tuner From). Anyway, It was my turn on the Dyno and they strapped my car down like it was a crazed horse, put probs in a few orifices and fired her up, the 27 inch flat plasma screen sparked to life with numbers and dials, every mash of the gas pedal the numbers surged, then the tuner yelled out, "Shut Her Down!!" un strap this car. I was amaized that I did not get my dyno readings. the tuner walked over to me and said, " she's running too lean your over 18 A/F ratio, I would not drive this car home" I was dumfounded, I said that V-8 Power.com gave me the tune for the JLT and I have not had any Check engine lights or codes show up. He turned and looked straight in to my eyes like a crazed trainer who values each horse as his own and said, If I can make one thing clear, You can not Tune a Car Over the Internet" he turned and walked away.
So I walk into the office to talk to the owner and he wants to make an appointment for a Dyno Tune in three weeks. He stated that
"The Air fuel was checked after the cats through the exhaust pipe and reading after the cats is always leaner, but 18 is can severly damage your engine" so he recommended that I put a stock Intake back on and flash the PCM back to stock to drive home.

The only items I have on the car are as follows:
JLT II CAI
62mm Throttle Body by Granatelli Motor Sports
Steeda Underdrive Pullies
MAC Axle-Back Exhaust.

I complained to V-8 Power and they sent me a new file from scratch, do I trust it, and run next week at the track? or cancel until the Dyno Tune before Drag Racing?

The one question still remains un-answered, What damage could I have done driving the car for a month that lean (500-600 miles)?

2k05gt

I complained to V-8 Power and they sent me a new file from scratch, do I trust it, and run next week at the track? or cancel until the Dyno Tune before Drag Racing?

The one question still remains un-answered, What damage could I have done driving the car for a month (500-600 miles)? with the Air/Fuel Ratio 18:1 with no check engine lights and no codes

Could the Tuner have a problem with their Dyno? 18 is very lean so why did my car not error out?

jbailer

WoW! When I first read the title of your post it really caught my attention. I was thinking Oh NO, he's not running that lean trying to get a little extra power is he? I'm really glad they caught it and it will be corrected. To many people have blown motors due to bad tunes. The new computers have much more sophisticated tables and many more tables that interact with each other. It really is extremely important to stick with trusted, experienced tuners. I've been reading so many posts on multiple forums learning about all the mistakes.

They are correct that it will read more lean at the tail pipe. The difference is typically .75 - 1.0 AFR though. I use a very high end A/F monitoring system and have for a couple years. It is very consistant that the readings they get from the tail pipe when on the dyno are about .75 AFR leaner than the true readings. With that in mind though, it is still at least 17:1 which is off the chart lean. I'm very surprised you didn't get a CEL. The way it should work is, the up-stream A/F or O2 sensors detect the A/F ratio and feed back it is running lean. The ECU responds by increasing the short term fuel trims to compensate for the lean condition. After a short period of time, the steady short term trim will start to move the long term trim to account for that condition at which time the short term trim decreases by the same amount. When the long term trim passes some pre-determined (usually around 17-20%) correction value, it will turn on the CEL and put the car into safe mode. In safe mode, it gets extra fuel, retards timing significantly, can change shift points on an auto, stuff like that.

Many things can happen from running that lean for 500 miles but usually the ECU can head that off. The biggest concern is when you run that lean with positive pressure. Since you weren't supercharged, it is much more forgiving. The lean condition promotes detonation which is devostating to an engine. Typically the knock sensors will pick that up and retard the timing before detonation can do too much damage. All I can say is stick with a respectable trusted tuner. -Joe

jbailer

Yes they could have a problem with there sensor. Those sensors used on dynos are subjected to the harshest environments. I think they should be re-calibrated from time to time and certainly replaced more often than I bet they are. Especially if they are testing cars running meth. I like using my system from Innovate Motorsports. I have the LM-1 Digital Air/Fuel Ratio Meter, LMA-3 Aux Box and a set of 3 XD-16 gauges. I can recalibrate my sensor periodically and I ALWAYS trust my readings over the dyno shop. -Joe

2k05gt

Thanks Jbailer for your reply..

I did notice some changes in shift and performance when driving it for this short period.
I was not sure If I could have done longterm harm to my motor or not.
Should there be somthing I should be watching out for, noises, smoke stuff like this
or do you think that I'm ok as long as I get a good dyno tune from these guys.

2k05gt

So I should install a Wideband A/F meter
I was looking at AFM Wideband but they do not explan how to install, can I just replace the O2 sensor or do I need a new hole welded in before the cats

Thanks again

jbailer

I'd really have to break out the crystal ball to answer those specific questions. The truth is, nobody can really tell you for certain without looking into it. My bet is something like this, their sensor was reading a little off combined with your car running right on the edge of throwing a CEL. It should be running right around stoich 14.7:1 at idle. Some like to run it just a little leaner so it's cleaner. As you start to get on the gas, the ECU is being fed pedal position, vehicle speed and a couple others to tell it to fatten up the fuel delivery now (based on a table). I'm betting the lean value they were reading was only near idle and it came down from there. Did they show you the chart? If he was reading it, they were logging it. If it was Dyno Jet, you can even download a viewer off the Internet to view the recording.

The thing is, I've never heard of V8 power. Maybe someone else here can attaest to their credibility? If they are a good shop, why would they need to send you another tune? Why did they send you a bad one the first time. If it were me, I'd seek out one of the better well known tuning shops and buy a tune from them. It's your engine you're gambling with. -Joe

jbailer

Definitely a new hole. Make sure they put it in right if you get one. Make sure they use a good quality stainless steel bung and it is mounted above the 3:00 to 9:00 position on the pipe so water/condensation doesn't sit on the sensor. Keep it just before the cat, farthest away from the engine to protect from too much heat. -Joe

2k05gt

http://www.v8power.com/

A/F Numbers were on the screen and everytime he reved the engine from idle the A/F number would drop to about 17.2 at idle it was around 18.0 - 17.9

My First tune was with V8power all I had was a K&N CAI

I went to My local Tuner here in Virginia and they tuned the car with the K&N and a 62MM Throttle Body, I had good numbers for an automatic car 271hp 282Tq.

I dumped the K&N because of low power gains, so I found a used JLT II CAI for 75.00 online.
Got a tune from V8power because I got CEL right off the bat when I installed the JLT.

For now I am back on the K&N and the Origional Dyno tune.

jbailer

I'm in MD and guessing that the club you were refering to is NVMC. I just joined and hope to meet you some day. Again, I can't really say anything about v8power but looking at their site and reading all of the stories of blown engines from bad tunes, I would just again recommend you seek a good reputable tuning shop. -Joe