Dyno results from last Saturday 5.7L Hemi swap

[cegpcola]

I wasn't real happy with the results! For those that don't know, in 2007 I finished swapping a 5.7L Hemi into the Durango. The swap was completely stock with the exception of a B&G reflash. The original setup used the stock Durango 2.5" exhaust and a cheap intake. This setup produced some good numbers at 242whp and 302 wtq on the Dyno in October 2007. About a month ago, I decided to redo the exhaust to open up the flow a little bit as the old setup really choked off the Hemi. I had an exhaust shop redo the Y-pipe using a magnaflow dual 2.5" to single 3" Y. This went into a Summit Racing 3" cutout and then straight back to a FlowSound Single 3" in and dual 2.5" out turned down just before the rear Axle. The seat of the pants feel makes me think that I picked up some ponies at the expense of a little loss of torque, but mostly it feels like it moved the powerband up just a tad.

So on to the Dyno. First off, the Dyno day was at a new shop here. Unfortunately the shop is still learning how to operat their dyno and it shows in the results. They have manual transmission cars down pretty well, but they seem to struggle with automatics and this was compounded even more due to my ported and polished TB (more on this later.) We started out with the dyno opperator driving the Durango to do the pulls and, after about 7 failed attempts to keep it in third gear for a pull, he decided to put me in it to see if I could get it to behave. Unfortunately, I got the same results. So we thought about it for a while and determined the only way to do it with the rushed time we had was to take it up to cruising speed and then drop the hammer. Of course this will induce a downshift to second, but we let the truck run through second gear and, as soon as he picked up the shift into third, he hit the sample on the dyno and I'd stay on it until the truck shifted again and he stopped the sample. The bigest problem with this is the truck is already past peak torque when the Dyno sample is started.

Now about the ported and polished TB! The electronic transmission is controlled by the PCM using load and RPM to determine the down and up shifts it needs and, porting and polishing the throttle body, makes the transitions between load columns very touchy. This in turn made it harder to be consistant with the throttle delivery resulting in either too much throttle (down shift), or too little throttle (up shift under cruise conditions.)

Now for the results:

Some funny runs where it upshifted and dropped the numbers.



Some cutout closed runs:



And with the cutout open:

[Connman]

Find another shop, those numbers are useless. The most important component of a dyno is the operator.

[midnite]

[cegpcola]

The original shop where I had it Dyno'd has a different operator now so I doubt they could get it as easily as they did last time. I'm waiting for the HPTuners software now so I can "lock" the transmission in third gear and get correct pulls. Plus with the software, I can tune the truck… which it needs.

[MWeed]

I have to agree. Your dyno shop doesn't know what they're doing. Those results aren't any better than a warmed up 5.9. The Hemi should be walking all over those numbers just stock and, with what you've done, you should be seeing much higher numbers.