A couple of weeks ago, I replaced the stock pulley with a 3". Went to the dyno for a new tune and was very happy to see an increase to 404/467. Could've done better but the stock injectors could'nt get the job done and were running lean at higher RPM. So, I got the 39# Cobra injectors from Whipple and bought a Kenne Bell Boost-a-Pump in case of future upgrades. After the install, the tune had to be completely redone, so back to the dyno and re-tune. I only picked up 4hp and 3lbs of torque. The A/F is now perfect. Temps were lower than the previous tune, so none of this makes sense. I'm running 22 degrees of timing now, as opposed to 17, just to make the new numbers. My tuner is lost for an explanation. Somebody got an idea?

 

Change in weather conditions? Original tune was way lean and unsafe, but made best power, they say the most power you will make is right before you blow it up. The numbers sound good and if it is safe I would be happy with it. Also, look at the curve, you may not have picked up much peak, but have a fatter overall power curve.

 

The runs were made at about 10pm, so temps were good at about 60-65 degrees, but we had a slow rain all day, so I imagine the humidity was up. The truck had been sitting a long time waiting for others to finish up, so there wasn't any heat soak. Two weeks ago, I drove it well over an hour, so there was plenty of heat soak and the temps were in the high 70s.

Here's the run two weeks ago:



Here's the most recent with the new injectors:


My original number with everything stock except the tune, was 365/395. Since then I have added LT headers, high flow cats, E-Fans, 3" Mandrel bent true duals with x-pipe muffler, and 39# injectors. Seems like I should have picked up better numbers than what I'm getting. Definately something wrong here just comparing the two dyno sheets.

 

Maybe, but look at the midrange, it really fattened up, I bet it drives allot better than before. You gained allot of torque and Hp, just not at the peak.

 

My tuner is lost for an explanation<<?? that scares me...but there right, your
torque curve/power looks alot better ...i dont see what your using for intake??filter?

 

Good thing it's halloween, cause that scared me too! He started grasping at straws and said, "may be the tranny, but it drives fine." and "could be the airbox." Which makes no sense because it's part of the Whipple kit and I asked him about it a few months ago and he said it was great. It draws from the fenderwell, not from under the hood. I'm going to give Whipple a call on Monday and see what they think, other than that I don't have a lot of choices. Bama Chips is the only game in town. I thought about Troyer's, but I really need this done on the rollers.

 

To be honest, I can't tell any difference. Where do you see I gained alot of hp and tq? I've looked at it and looked at it and yes it looks a little fatter but I think the difference in the RPM on both graphs give the impression that it's better than it is. Maybe 5 or 10 hp at the same rpm across the line?

 

If you look at your old hp and torque curves, the lines are straight...When you look at the new curves, your lines are curved or humped which means you have more in the middle...

I see in your gallery that you have some pretty big tires and wheels...could they be robbing some power? not to say that the power you're making is not good enough...

 

Here's a pic with some lines drawn across the repective RPM's.



If you notice, I made gains in the lower rpms, but in the higher rpms, where I was have a lean condition, hp and torque are the same. The whole purpose of replacing the stock inj. with the 39# inj. was to elliviate the lean condition and see a larger gains. The guy who owns the dynotune said when I change out the inj. I should see at least a 20-25hp gain. This was also predicted on this forum when I asked for advice. I believe something is wrong. As far as the tires and rims, they are the same size that originally came on the truck, so that would not make a difference. 05RoushMKLT is making 427rwhp with the same setup minus the headers, smaller pulley, and exhuast.

 

You are always going to make more power in the range where it is just lean of safe with a supercharger...12.5 or so. It's the same with n/a setups but for them a 12.5 AFR is perfectly safe whereas for a boosted app. it isn't considered very safe. There is also a point where adding timing no longer makes any more appreciable power....just because you advance the timing doesn't mean you will always gain power from it. Also dyno's are not always consistant....you can expect to be rather significant differances even on the same dyno between different periods of time. There are lot of variables just to lay blame on something wrong with the truck.

 

I understand what you and everybody else is saying, I'm just having a hard time believeing that my truck is producing what it should. It dynoed, with just a tune, at 365rwhp. Since then, I went from a 3.375" pulley to a 3.0", added ceramic coated LT headers, high-flow cats, mandrel-bent 3" true dual exhaust, e-fans, and 39# injectors. All these performance enhancing mods have netted me a whopping 43rwhp. Does this sound right to you? And as far as the dyno being inconsistent, I doubt it was off by much if any, because I cannot tell any difference.

 

404/467 seem like good numbers to me.
You picked-up 40+ horsepower, I'd say that's pretty good.

Sounds like atmospheric conditions weren't the same.
If humidity was significantly higher, you'll make a little less power.

But it's not like a huge difference.

What numbers were you expecting?

 

With all my mods, I was thinking it would be about 425/490. Shouldn't the smaller pulley give me 30-40hp by itself?

 

well 3.75 to 3 isnt really that "big" of a difference. you see a difference of what 3/8s an inch radius.
dunno, i think you are putting down exellent numbers for your setup, and yah your new curves look great, much more usuable power.
-Patrick

 

Well, it gave me another 3lbs of boost and I saw/felt a "big" difference. I know a guy who built a 900rwhp mustang, so I'm going to have him take a look at it and see what he thinks. After that, the tranny is getting replaced with a monster box and a new converter. Maybe a bigger MAF too.