Is it that hard?

[93Ext5.7ltr]

Hi Guys,

Its been a while and I'm feeling a little better about myself after reading the following article, but I'm not sure I should be feeling this good. Can someone help me understand the weight-to-power ratio of HP a little better? I'm still pretty unclear on it.

Anyway - back to the article:
Truckin' No. 9 Volume 33, July 30, 2007 (out on sale now). "To hell and back" (2007 Harley-Davidson F-150) page 38,39 + 55

(Granted, this is a 4-door P/U and completely stock):
pg 38 "And the bad-boy Harley gives Ford a tagline that it can now punctuate with a bad-ass 450hp 500lb-ft supercharged powerplant......"

pg 39 "Our time on the dyno was troubling. Our first power run resulted in numbers far lower than the 380hp that we had expected at the wheels. We let the truck cool down and gave it another shot, getting only 337 hp. The guys at Livernois said they couldn't get any more out of it, without discarding th rather restrictive airbox or doing a custom tune. We did confirm on the dyno, not the street, that the speed limiter kicks in at 120mph".

pg 55 " This truck came with a supercharged 5.4L V-8 that cranked out a respectable 445 hp and 500 lb-ft... KNowing that the factory speed limiter on the Roush was activated and set at around 95mph, we didn't bother taking the truck to a 1/4mile dragstrip.........So, we took the Roush to a nice patch of asphalt that we know, where we tested the 0-60 performance. Out of five runs, we twice made a time of 6.76 seconds."

See sig for my adders and note that its been a long-standing-well-known issue that my vehicle is in DIRE need of some sort of tuning beyond what even some pretty good tuners can tune. They also suspect I have a problem between the TPS and injector wiring harness (this is evidenced by poor A/F ratio until about 2800rpm, then it steadily evens out until about 6200rpm). Ran a 14.6 1/4mile when it was 105 degrees and ran a 14.6 in 88 degree weather.... a little bit too consistent for the amount of temperature change. I pulled of a 0-60 time of 6.2 (not a 60' time - he he)

So am I ?

Is it that hard to make rwhp out of a truck? Should I feel more impressed with my truck being that its N/A and tapping into 360rwhp? Understandably, I'm not trying to turn it into a dyno queen and obviously have my priorities right I feel, since I'm trying to get the ET down and disatisfied with it.

Sorry this was so long....just trying to understand.....thank you for any feedback.

[txarkitekt]

Ok...couple things:

First, you shouldn't try to compare flywheel hp and RWHP from a Ford--especially the 5.4L Triton 3-valve motor. I can't tell you how many countless tuners and editors I have heard say that the Triton is not really putting out what Ford claims. And that has become general knowledge as of late... Each manufacturer now has to abide by SAE ratings for hp figures...A lot of vehicles will end up seeing lower than expected hp numbers because they are trying to set a standard. At the opposite end of the spectrum, the Nissan Titan claimed 305 hp out of their Endurance 5.6L V8. Several tuners and editors say that the Endurance figure was grossly underrated and it feels like it is making 340-350 hp instead. Case in point---take a ECSB Nissan and Ford--each with the largest motor, towing package, and lowest gear ratio each maker offers. Line them up. Then run them. The Nissan at 317 hp/389 ft.lb. would annihilate the Ford at 300 hp/365 ft.lb. eventhough they are pretty close in output numbers...

Second, it is harder to get RWHP out of RWD trucks...than say a RWD car. Trucks have to have heavy duty trannys, TC, rear ends, driveshafts, U-joints, etc throughout the driveline. All of that HD equipment adds mass to what is already there... Thus requiring the motor to have work slightly harder to get that power from the flywheel to the ground some 15' away. A RWD car does not have to have the HD stuff, making it easier for a car to put out more hp than a truck.

And as for your PCM tuning issues, consult Allen Nelson for your tuning needs. He is in San Antonio. He can figure everything out for you. A live tune is definitely what you will need to do--considering your highly modified truck. Where exactly in Texas are you? Depending your location, Allen Nelson is in San Antonio, Billy @ TRT is in DFW, and Charley Wheatley is in Houston.

[93Ext5.7ltr]

Hi txarkitekt,

I respect what you have to say (BTW - from DFW area too), but I'm going to disagree a bit (Ford hater myself though)

I've heard of the point of view about Ford's dyno numbers versus HP and don't argue there might be something too that. However, Hot Rod Magazine (which I would consider pretty fair and impartial) has an issue also currently out, September 2007 "Powerparts! We test 'em" pages 84 - 90:

(Stage 2: Normally aspirited)
Engine Dyno (on the dyno is a 5.7Liter LS1 from a '04 GTO) and its had some things done to it. It pulls 491HP@6,200RPM / 458lbft@5,000RPM .

Now they do some minor modifications for the Stage 3: Normally Aspirited Chassis Dyno where they change out he hotcam they had in with a custom-grind Crane hydraulic roller cam (PN 144HR00062). The difference between the cams are:

Hotcam (part number 12480033) 219/228/.556/.556 LSA 112 (a cam I've had in my truck before)

vs

Cran 210/218/.583/.583 LSA 112

and they add a Borla '05-06 GTO Cat-back w/ dynatech headers w/ high-flow mini-cats.

.....the results? 352.8HP@ 5,750 RPM 358.8lbft @4,750 RPM

Granted, they did not take it up to 6,200RPM as they had on the engine dyno and they also had not taken the torque up to 5,000 as on the engine dyno. Even the magazine (who did not appear to speak of any suspected malfunctioning dynomometer) stated "-but obviously even with the new cam, the engine in-car was down about 140hp and 100lbft at the rear wheels."

So this was from even a car perspective versus all the heavy duty stuff from a truck.

I'll give TRT a shot, but won't rule out going to Allen if my tune shop can't narrow down anything better as a possible cause.

P.S - they wound up getting the GTO to 601rwhp with a upgraded supercharger and Alcohol injection kit.