August West

So I finally got my car dynoed after a year plus of putting it off...my car has the regular SW chip in it, Euro RS valves, Elgin Super C2 cams, Fabspeed Sport Cat, Cup Airbox w/ K&N filter, and a G-pipe.

My intentions are to send these results to Steve Wong and get a custom chip made, but I thought I'd float the results with all you guys and perhaps get some opinions as to if it'll be worth $675 to get a new chip made or not. The AFR seems a bit rich but I don't know offhand how askew it is...thoughts?

Also wondering what you guys use for estimating power at flywheel given it's a C4? I've heard 15% for 2WD and anywhere from 20-25% for AWD...thoughts?

Thanks in advance!

-nick

I'm going to say that you're much too lean. The AFR on my bone stock '91 C4 was down to 11.6 at ~6300rpm. With the 93octane Wong chip it was down a bit more to 11.4.

I'm not sure how the injection compensates for all of the extra breathing that you've given the motor. Using a carb example- when you make the engine breathe more air, you have to go up a jet size so that it also gets more fuel. There could be some analog of that going on.

Here are the results from my dyno runs, with and without the SW chip, otherwise 100% stock. This was on a Mustang dyno in 3rd gear.

https://rennlist.com/forums/964-foru...ve-w-chip.html

*edit, looks like photobucket is down at the moment so the plot isn't coming up, but my numbers are in there. Hope this helps!

Cosmos99

14.7 is stiochiometric anything with a lower first number is rich and a higher first number is lean. So if you are running 11.6 your car is running rich as stock and even richer with the chip ( which it will usually ). To the OP I would ask the guru Steve Weiner from Rennsport Systems or Geoffry. They can help you interpret your dyno figures.

-nick

Stoichiometric is great for a emissions, but not for power (nor fuel economy).

But I do agree about just sending the curve to the experts. I'm sure that Steve will tell you directly if he thinks that the arf is very far off in his experience. I'm guessing that it is.

provoste

FYI- 964's don't make good power running rich. Low 13's AFR are generally Steve's targets. 11-12 is RICH.

August West

Okay, I've stared into the rabbit hole of differences between dyno machines and it seems that Mustang dynos typically report horsepower readings that are around 12% lower than what dynojet dynos report. Differences lie between the way the machines load up the chassis.

I was a little let down that after all my engine upgrades that the Mustang dyno only showed a max of 211 rear wheel horsepower coming from my car. Once I corrected the reading, conservatively using 10% for the differences between dyno machines, and then conservatively using 20% drivetrain loss in an AWD C4, I arrived at a more respectable number:

211/.90 equals 234, then dividing by .80 equals 292 flywheel horsepower. The final number can vary substantially depending on what factors one uses for drivetrain loss and conversion factor between the two dyno machines.

It seems that the Mustang dynos are better for actually tuning the car because it tries to mimic real world loadings with car weight and wind speed, etc. It seems that most people prefer the dynojet readings because the numbers come out more robust!

I'm gonna go ahead and get Steve to burn a new chip... I've already spent boatloads on engine upgrades, so what's another $675 dollars, huh? My AFR needs to be smoothed out and brought closer to 13.2:1...I'll let you all know how it goes.

D.C.

I have a stupid math question for everyone.

Seems there are 3 ways to calculate this.

211/.90 equals 234, then dividing by .80 equals 292 flywheel horsepower.
or
211/.8 equals 263, then dividing by .90 equals 293.
or do we add the 20% and the 10% together and do it this way.
211/.7 equals 301

Not really that much difference, but 8hp might make you feel even better.

I think 211/.7 = 301hp is the correct way to do the math.

Congrats, and nice work

Dave

Lorenfb

"My intentions are to send these results to Steve Wong and get a custom chip made"

Don't waste your time and money!

Read here;
https://rennlist.com/forums/911-foru...-the-myth.html

-nick

I've never trusted a dyno to measure anything except differences in output on the same car and with the same dyno. Ultimate numbers seem to be a ballpark at best.

I am now enlightened in regards to target afr for our 3.6's. I thought my numbers were pretty rich but I didn't have a reason to doubt them. Now I'm wondering if I've got an air/vacuum leak someplace.

Anyway, I would be curious to see what Steve W. thinks of your afr curve. And how the dyno curves compare if he burns you a new fuel map.

For the math- it would be a 10% correction between dynos first, then the correction for flywheel power. But there is a lot of wiggle room in those numbers.

provoste

Again? Please let's not revisit this argument once again.

Lorenfb

"Please let's not revisit this argument once again."

But we continue to see the naive get sucked into 'taking the snake oil'!

KaiB

Time and time again, you only pop up to spew your venom regarding this subject. Do us all a favor and leave it alone; your point(s) have been made and taken...no need to regurgitate the same old.

If you really feel the need to do so, perhaps OT would be the best spot.

August West

I'm remapping because of the extensive upgrades that I've done to the engine and it only makes sense to address the fuel mapping in these instances...it's not a matter of naivete or drinking snake oil.

Lorenfb's reputation precedes him... 'nuff said on that.

Steve Weiner-Rennsport Systems

BS.

For the benefit of others following this thread,...

A GOOD chip improves throttle response and torque provided good premium fuel is used.

Naturally, the success or failure lies with the experience and knowledge of the person doing this and E-bay software is to be avoided like the plague (Loren knows this).

Mister Wong is one of the best at this.

Lorenfb

"BS."

And where are your data and references to refute it?
Have yet to see any of your personal data or dyno runs!

Have to love those that promote 'tuning' are also the ones that profit off the naive.