My Blue Heaven

With the anomaly I've seen on my dyno graph along with the one other posted by SC67Stang ( http://forums.bradbarnett.net/index.php?ac...e=post&id=12931 ) I'd like to know how many auto owners have had your car dyno'd and what your numbers were, and what your graph looked like.

I was doing a 4th gear run starting at 65mph. At around 90mph/5Krpm there is a pronounced stutter, and the dyno reflects it as a lag, then a surge, after that the graph calms back down to normal. You can see it on the above dyno graph also occuring at the 5K mark.

My tuner is supposed to email my info and as soon as he does I'll post my sheets.

I'm curious to what could be causing this as it seems to only be affecting autos, but John's (swingle007) didn't see it on his dyno run.

Also the torque falls off like a dog after surge. This is both pre and post tune.

Any ideas? Please point me to your posts if you've previously posted an auto dyno graph.

The attached dyno sheet is my third baseline run, trans in 4th gear, o/d off. Started run at 65mph to avoid downshift into 3rd.

See further down for more detailed dyno sheets.

Thanks,
Chris

elvism

did u have the tune send to you by a programmer or were you there while the tune was being done on the dyno?

My Blue Heaven

I used the performance tune from diablo. Lost about 5 hp, across the board as I remember it. I posted all this last night in depth. But the anomaly was apparent from the first baseline pull we did.

elvism

i notice one thing for sure and that is if a car is be tuned right then it must be done by someone that knows what to look for.just find someone that knows what to do with this issue. ill keep you posted.

My Blue Heaven

This is the third baselne pull (003) vs. the 1st Diablo pull (004).

You can see I lost HP with the new tune so far.

My Blue Heaven

This is a zoom from 80 to 100 mph on baseline pull 3, shows the spike real well. From what my dyno tech told me, he thought that the engine/tranny was slowing down for whatever reason, and that was loading up the dyno. After the engine/tranny resumed it allowed the dyno to release it's stored energy and caused the spike. After that energy was released the dyno went back to the true HP that the car was making. It's all way above my head.

My Blue Heaven

And finally, this is the same pull, # 003, but showing engine rpm rather than mph.
4850 to 5400 is the range and you can see the trippy graph. The loop is caused by the engine rpm actually slowing down then speeding back up. You don't see this on the mph graph since the drum is still accelerating at this point and raising the mph. I don't know what's going on at 5K for the auto's but whatever it is ain't good for power.

OK, any ideas what might be causing this? anyone?

elvism

i had the same problem as you and still do at 3 to 4th gear. im going back next month on the 23rd to fix this issue. i have a dip also but i never saw a loop like that??i will try to post tomorrow my result if i can finda scanner.dont worry well get it right.

My Blue Heaven

You might not have seen the loop if your graph didn't have engine rpm at the x (?) axis (don't know if it's x or y, been a long time since I was in math class!)

Chris

Tucker

Here is a Auto dyno:
I'm not trying to promote, it's just the only auto 05 graph I have
This was a 3rd gear pull.

Black Magic

When you were on the dyno did you have the traction control turned off? Should the auto's run the dyno in 3rd gear? That does not fix this problem but 4th gear seems like it takes awhile to max out with stock gears to 6000 rpm. I was wondering what that was like on a dyno waiting for it to hit 6000 in 4th gear? Could this loss in rpm be a knock sensor or something related to the front wheel speed sensors? Hope you find the problem. I go in 2 weeks for my first pulls.

My Blue Heaven

If you don't turn the traction control off the car doesn't do anything at all

You dyno in 4th due to the fact that this is the 1 to 1 ratio for the tranny.

I have a 4.10 gear installed and it only took a few seconds for it to spin up to the rev limiter from 65mph. We started from 65 due to the downshifting issue, but my Dan has told me that he knows how to lock it in 4th now so the pulls we do next will be from a lower speed.

Chris

dhof303

I know what this "loop" is and it can be a typical dyno graph from a car with an automatic due to the torque converter "flashing." My 2000 Superduty did the same thing on the dyno in December, it is most likely attributed to a stock transmission with an engine that is making more power. My truck has a diablo sport 100hp chip and while it does increase transmission line pressure it still has the stock transmission internals. I haven't seen this phenomenon on any other 05 stangs but I would suspect it could happen to any of them.

Black Magic

Chris, is there something I have to do when I got to the dyno about this or Dan is going to do something on his equipment to fix? Thanks for any help.

My Blue Heaven

As you've got a couple of weeks this might all be figured out by then, if not at least you're aware that it's a known issue with the Automatic transmissions if you see it on your dyno run.

BTW, I wouldn't count the spike as your top HP number as it's not a by product of the engine making power, it's the inertia from the drum being released.

Chris

My Blue Heaven

I wonder if they did the 3rd gear pull to get around the spike.

Doesn't make much sense otherwise as you're putting quite a bit less HP to the ground in 3rd.

Chris