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Discussion in '1996 - 2004 SN95 Mustang -General/Talk-' started by Nightfire, Jun 19, 2014.
My only guess (and I'm no dyno expert) is that the tires were slipping on the roller?
I doubt that was the case. This is actually a very typical chassis dyno graph. Dynojets are typically known for having more erratic looking graphs that some of the other load bearing dynos. There are also smoothing functions that average the readings to provide smother slopes and make the graphs a little easier to read. Most dyno graphs without correction look like this and there is nothing wrong with it that I can see. I'm curious as to the dip in the graph and would be interested in seeing exactly what the converter was doing as far as slip % and lock up go.
This is a graph form on of our dyno pulls with my hooptie. With the smoothing on you can get a much more pleasant looking graph (This was actually used in RacePages magazine, hence the smoothing to make it easier for most people to use)
Its no big deal. Apparently its just the converter locking up.
Looks like one of the runs is with the converter unlocked, and the other with it locked.
Regardless, a graph really shouldn't be quite that rough. It's not horrible, but it should be fairly easy to smooth it out via tuning. Notice it already has a lot of smoothing on it (SAE 5). I don't know exactly what's causing it, but I'd guess the transfer function still needs some fine tuning, or the spark tables need some smoothing.
The graph is taking a beating on facebook. People are say the tune looks like . To be honest, he's kind of the only one in town and Im not too sure of his abilities.
Do you have one with the AFR reflected on the graph?
I think I got burned on the tune. I've always heard to go out of town for a tune and not let anyone here touch it. My builder swore by this guy so I gave it a shot
Would crazy bad belt slip explain it?
Talked to my tuner. Apparently my slip is worse than I thought. Its pretty much slipping throughout the RPM band (causing the erratic lines) and slipping HUGELY up top (creating the dip). The 3" is coming off ASAP
He also said AFR's are solid and apologized for not adding it to the graph. Timing is around 15deg I believe.
If you're actually having belt slip, you've got a problem somewhere else. There's no reason you should have any trouble pushing 10 pounds of boost through stock heads and cams via a fairly efficient blower, especially not with an 8-rib setup. I'm running a 2.9" pulley pushing 13 pounds of boost on a 6-rib setup, with this much wrap:
And that's with an inefficient Eaton. 03/04 Cobra guys regularly push 16 pounds through 4-valve heads with the Eaton on an 8-rib setup. No reason an 8-rib Procharger only pushing 10 pounds of boost should have any issues with belt slip.
I think I would be getting a little nervous about the builder/tuner at this point. Sounds like you may need to look at trailer'ing the car to DFW or SA for a week and let a new shop take a stab at it before you need another motor.
I also can't imagine the belt slipping that badly. I've pushed a 6 rib setup into the 20psi range without any special pulleys or coatings.
No 8-rib. Stock 6-rib w/ stock tensioner and a 3" pulley
3" pulley with a stock crank and stock-ish top end should see 16-17lbs.....we only saw 8.
Oh. I was just basing my assumption on this quote from earlier in the thread.
Regardless, you shouldn't have problems pushing 13+ pounds on a 6 rib. Did your tuner datalog the boost readings?
Yeah, that was the plan but my oil pump took a crap at the last second which ate into my budget a bit. I have a 3.25 and a 3.5 pulley. Would I see slip with the 3.25? I think the 3.25 is rated for 14lbs.
I just wanted to go big from the start and threw on the 3" which was bad idea. Boost readings were not datalogged, don't know why. I showed up around the tail end of the pulls so I wasn't able to keep on top of things. Boost was monitored via boost gauge and he said that it was all over the place. I'll ask for 1 pull and datalog AFR's and boost.
He also told me to remember that the dyno was set up for power vs. MPH and not the typical power vs. RPM. Power vs. MPH graphs are always a little rougher,
Not to break your balls but I posted a dyno graph earlier that is power over MPH in the same configuration as yours. What he is telling you in that regard is total BS.
As far as the slip goes, If you are having problems with a 3" pulley a 3.25 or even 3.5 isn't going to make the slip just magically vanish. There has to be something else going on here. Is it a manual tensioner or an automatic one? Is the belt configuration correct for your application? Some pictures of the setup, especially the belt routing may be beneficial.
I can't think of any reason a tuner would want the power over speed instead of power vs. rpm. Every change in the tune you'd ever make, you do it at a certain rpm. So unless you want to back-convert to the rpm knowing your gearing numbers, the speed is pretty much useless as far as I'm concerned.
what belt are you running??
Not sure on the brand (since my builder provided it). I believe its just a 107" (or something close to that) off-the-shelf O'Reilly's belt
Oh, and other great news.....aside from the crazy belt slip, its misfiring. I almost feel like giving up lol. The thing still fkn hauls though!