Mike,

I just read a post in the supercharger section from a member who dynoed his 4.6L with K&N FPIK, Superchip, JBA Headers and Gibson cat back and got 187 RWHP. This seems low to me, I figure about 200 - 210 RWHP (220 stock HP + 12 for K&N + 22 for Superchip + +20 for headers and cat back = 274 FWHP - 65 for AT loss = 211 RWHP) What do you think?

WarEagle

 

I don't think anything about it.

Think about it like this: unless it's your vehicle, you were there, **and** you have some real hands-on working knowledge of the various types, model & brands of chassis dyno's in general, including knowledge of the specific dyno used and exactly how the pulls were done including all conditions & data, there is nothing to be derived from just the raw numbers, they mean almost nothing. There is no useful data, just raw numbers.

It sounds like you're making the same couple of basic and very natural errors/assumptions here (and almost everyone does by the way, myself included years ago, before I had the knowledge I do now), the first of which is trying to interpret anything meaningful from what somebody else got on some dyno somewhere. When you don't have any data, conditions or knowledge of the dyno, the shop or it's operator, that's an exercise in futility. The second is assuming or thinking that dynos are basically the same, or that they are somehow a consistently accurate type of device, including from one dyno to the next. Those are perfectly normal assumptions for us to make, most of us tend to think of a dyno as a dyno, that they're all the same, and any dyno is always "right." A perfectly natural assumption. However, they aren't, not even close. Conditions vary, as do dynos, widely and sometimes *wildly*.

99 times out of 100, the dyno's people go to are inertia dynos, and usually Dynojets, as inertia dynos are the only dyno's that most shops and people can afford ($30K as comapred to 6 figures for a good eddy current dyno), and they just aren't very accurate for a number of things. They cannot properly compensate for widely varying vehicle weights, for one thing, and that alone is a *huge* factor that throws off power levels reported. Sure, they claim to be able to compensate load factors for weight, etc., but in reality, forget it. Any shop owner who has owned or operated for any length of time both a good eddy current chassis dyno and inertia dynos as well will be the first to tell you that an inertia dyno is not particularly accurate. Some feel that they aren't much more than a tuning tool to get A/F's on.

For example, put a bone-stock Lightning on a Dynojet or just about any other inertia dyno and you'll get readings that are typically 30-40 horsepower too HIGH, which is why we have seen all the posts from Lightning owners here with no modifications bragging about having 330 horsepower at the rear wheels. Sure, the Dynojet *said* that, those people aren't lying, not in the least! But it never happened in reality, not once has a stock Lightning made those kinds of power levels to the wheels among the many Lightning owners we serve, they'd have to be 400 or more at the flywheel to get 330 rear wheel. The *real* range is 260-290 at the rear wheels on a stock '99 or '00 Lightning, and about 300-310 on an '01 or '02 Lightning. Take a regular F-150 on that same Dynojet that read too high on the Lightning, and you can get readings that are too low! I've seen it happen more times than I can count.

That being said, even we spend time on Dynojets from time to time for certain things, and will continue to where applicable.

One much more minor thing to remember is that the driveline losses are not static regardless of power level. As power rises, the amount of power lost to the driveline rises somewhat as well, though it is not linear or exponential, I don't subscribe to the set percentages, either.

At stock power levels on a "regular" 5.4 F-150 from 1999 or later, which is 260 hp SAE Net at the flywheel, which will translate to about 195 rear wheel with the 4R70W automatic, and 191 with the 4R100 automatic, **assuming** the engine is actually making it's rated 260 hp bone-stock. As you get up higher in power, you'll lose a bit more to driveline losses, it won't stay a constant 65 hp or 69 hp with the 4R10W & 4R100 trannys respectively.

If you have a stock 4.6 making it's 220 hp rating and it has an automatic, that will be the 4R70W and that would give you about 155 hp to the rear wheels, under ideal conditions. Given that level of modification, the Superchip, the K&N FIPK, headers, and the cat-back system, yes, 187 is a bit low, but that all depends on how much power that engine was making in bone-stock trim before any modifications, the octane & energy content of the fuel being burned, the conditions in the dyno test cell at the time, as well as the dyno, the operator, how the pulls were done, and so on, as I mentioned above.............................................

 

"I figure about 200 - 210 RWHP (220 stock HP + 12 for K&N + 22 for Superchip + +20 for headers and cat back = 274 FWHP - 65 for AT loss = 211 RWHP) "

When adding mods 2+2 does not always equal 4. You can't just add up all of the advertised hp to get a total.

I think someone here said it best. Add up all the advertised hp and divide by 2. That will get you in the ball park.