Is this bad???

[SVTkel]

I am no expert however we are not comparing apples to apples regarding a stock Cobra dyno and the dyno posted above.

In the original post it takes the car over 1700 RPM to drop below 12.0. This car is not stock anymore as it has a catback, X-pipe and one of the best intakes you can get.

On the dyno you posted of a stock car within 250 RPM of the start of the pull the car is below 12.0.

If it were my car I would run and get it tuned right away. A couple of $100 is cheaper than a new motor, plus as a bonus you will make more power.

 

[93 347 Cobra]

I think that the problem with the internet is that guys hear about where the A/F needs to be for these cars and they chew on that and come up with this nonsense that a car needs to be at 11.8 from 500rpms to redline. Which is retarded. The stock Ford tune doesn't even advance the timing to the aggressive levels you do in an aftermarket tune. How much timing is dialed in has everything to do with whether or not a car is going to detonate.

YOU SIMPLY DON'T DETONATE BECAUSE YOU HAVE A LEAN A/F! There are other variables that affect detonation.

You're right and people are bustin' your balls for it. There's a reason why tuning tools have different sets of parameters for above 4K and below 4K.

 

[01cobravortech]

You're right and people are bustin' your balls for it. There's a reason why tuning tools have different sets of parameters for above 4K and below 4K.

I'll tell you this man, I've seen a lot of dyno sheets with guys running the JLT CAI & RAI...and they are incredibly similar to the OP. If this was considered dangerously lean, guys like JLT would be out of business. 8psi is not 13-14psi. You can't even compare the low stock timing with aftermarket tunes that push the timing to 20 - 23*. But whatever. :beer:

 

[jcobra]

I guess the overall consensus is to get it tuned. There goes another $600.

 

[04CobraMatt]

Im gonna agree with 03cobravortech, the timming is pretty conservative in a stock tune. Dont worry about it... If you are worried, just keep running 93oct until you do get a tune. I dont see a rush for you to get a Xcal2/Livewire, but with a custom tune will get you another 10-15 pony's and the option to run either 91 or 93 safetly.

Another thing, how was this reading taken? a sniffer in the exhaust?

 

[ReVviNg HiGh]

might be the prochamber giving a bad reading. Is there a o2 bung upstream the rear o2 sensors? if the a/f was checked using a wideband and using one of the rear or bungs, thats the problem. the prochamber makes the exhaust back up to about 1/2 - 1ft before the chamber box. this caused my friends problem. he had to get a bung welded in upstream the rear o2's but below the upper 02's to get a good accurate a/f reading.

The stock tune is very rich. You are ok with your mods. When you get a pulley i would get a tune.

 

[04CobraMatt]

might be the prochamber giving a bad reading. Is there a o2 bung upstream the rear o2 sensors? if the a/f was checked using a wideband and using one of the rear or bungs, thats the problem. the prochamber makes the exhaust back up to about 1/2 - 1ft before the chamber box. this caused my friends problem. he had to get a bung welded in upstream the rear o2's but below the upper 02's to get a good accurate a/f reading.

The stock tune is very rich. You are ok with your mods. When you get a pulley i would get a tune.

I've got an off-road prochamber with my wideband plugged in the drivers side rear 02 bung.. first i hear of this... in what way do the readins get affected?

 

[jcobra]

Ill have to find out where they got the reading from.

 

[ReVviNg HiGh]

I've got an off-road prochamber with my wideband plugged in the drivers side rear 02 bung.. first i hear of this... in what way do the readins get affected?

Turbulance was the issue. The reading was not accurate at the time of tuning with the wideband on the dyno. Luckily Evoloution Performance has an exhaust shop and was able to have a bung welded in between the o2 bungs. After that was done they got accurate readings. This is not the 1st i have heard with using the prochamber. I sold mine right before i got mine tuned last week.

 

[jcobra]

This was the response I got from my tuner as to how the dyno read my a/f. He also races NMRA.


they use a $2500 sniffer system from the tailpipe.. i use it when i dyno my car.. its almost dead on to my 2 widebands in my exhaust..[/QUOTE]

 

[spincobra03]

jcobra 600 for a tune? first off who is tuning the car, a good tune should cost you half that, I think it tough to say whats a safe A/F considering you havent increased boost. Most guys on here are used to saying 11.5 is the norm but most of us never brought it to the dyno until we were ready to mod. I guess the point is just spend a couple bucks and go to a reputable tuner. good luck

 

[jcobra]

That price includes an xcal2. tune, dyno time. If im gonna have it tuned I might as well pulley it. Ive been holding off cause the car only has 4300 miles and I wanted to make sure the tick didnt develop as I am still under the ford ESP.

 

[ReVviNg HiGh]

if the sniffer was used then the prochamber will not mess up the reading. The reading is only an issue when using a the rear o2 bungs for the wideband.

 

[jcobra]

if the sniffer was used then the prochamber will not mess up the reading. The reading is only an issue when using a the rear o2 bungs for the wideband.

Yeah, it just needs a tune.

 

[01cobravortech]

http://www.modularfords.com/forums/2003-2004-mustang-cobra/first-dyno-run-evaluation-85095.html

Here's another guy on MF who just dynoed a bone stock Cobra. Please pay close attention to the stock tune's A/F...ahem ahem ahem...ahem

 

[Blown04GT]

I think 01cobravortech said this earlier in a matter of words - it isn't the lean mixture that always causes detonation, IT IS THE TIMING.

The common misconception of running lean and blowing motors is running too much timing, causing the mixture to run lean, and then detonating. The oh so fatal detonation is not a direct result of the mixture running lean, but because it had too much timing.

Basically what happens is the spark comes too late and the mixture has already compressed and heated to the point that it explodes on its own (without spark) and then the spark ignites directly on the top of the piston (the dreadful "ping" you hear from detonation).

So yes, get it retuned to see some decent gains, but don't because it is running so lean that it will blow up.