Under-rate HP .. why ?

[Daffy]

I'm not in the car biz and was wondering if anyone knows why a manufacturer would purposely under-rate the factory HP number. It seems common knowledge that the vipers have been under-rated & may continue to be. The new mustang cobra is rumored to be (we'll see), but I assume if a manufacturer under-rates the car there is a biz reason for doing it, regulations, insurance, something. Just wondering if any of the more informed of the auto industry here might know the logic behind it.

thanks.

Dave.

 

[Viperfreak2]

Oh yes, they under rate if they are smart! Can you imagine how angry all the 97 Mustang Cobra owners were when they started putting the cars on the dyno to baseline the engines before they did any mods and the things didn't make the advertised power? MANY lawsuits. A LOT of Viper owners put their cars on the dyno too.....imagine the rating from Dodge was 530hp in magazines and commercials they when you put the car on the dyno it made 499hp.

 

[toddt]

Ford didn't miss by a little--they missed by a LOT. This was a clear case of a coporation flat out lying.

Does anyone here object if they don't get 460 corrected horsepower? Does anyone here sue dodge if their ACR dynos to 449 instead of the rated 460 after correcting for drivetrain? I really doubt it. We just throw down an unhappy face and move on. Maybe our next Viper will have a stronger engine.

My point is--there is a bit of tolerance to the horsepower figures that is understandable.

But EVERY Cobra fell WAY short of the claim.

Ford could freely pick a number right in the middle of the spectrum of TRUTH, and no one would complain.

I'm really interested in what these numbers really will be.

 

[Daffy]

Hey, I was one of those guys. My 99 Cobra convertible was down nearly 30 rwhp when I baseline dyno'd it. It was one the very first to be an issue, Ford even flew an SVT engineer out to go over my car when they were researching the issues. I ended up getting an entirely new engine, and two replacement transmissions (they had issues there two), plus new exhaust and brake lines, and etc, all in 7 mos. Of course the new engine they put in had the flawed intake that was the main reason for the low hp to begin with, so then it had to be upgraded again with "the fix". This is how I jumped outta the Mustang and into the Viper (how's that for an upgrade).

That was all bonehead stuff, things falling into cracks at Ford etc. Stuff happens, it was a bad year. My previous 3 stangs were magnificent.

My curiousity now is why a manufacturer would rate the engine significantly lower than actual. If the initials tests are accurate & rumors are true, why would Ford put out the 03 Cobra rated at 390, if they are hitting 420, if they want a margin why not claim 405 to match Z06 - with a 15 hp window, etc. Why did Dodge underate the Viper, I've heard this also about the vette and even Porsche TT 993's. I just wonder if there's a biz reason they would do it. Or is it as simple as they want to be WAY safe in case someone checks and their manufacturing tolerances are so off that one engine goes out 40 hp short & they don't want that bad publicity - seems like a weak reason to me.

Dave.

 

[Viperfreak2]

It may just be me, but I get really angry when my french fries aren't filled all the way to the top. I would never think about suing anyone, it's a waste of time for everyone. I think my problem is that I start to wonder what else is wrong when I feel I'm not getting my moneys worth. Did someone line up the piston ring end gaps? Did my transmission get the wrong parts? were the bolts on the suspension torqued correctly?
I do understand the under-rating, but you are correct when you say it should reflect the average power output of all the engines tested. The testing should be continuous also, just to verify that everyone in the supply chain is maintaining their quality. There should not be a huge gap between a 'strong' engine and a 'weak' one. Truth is, I was never impressed with the power of my 99 RT/10. After the mods (exhaust, smooth tubes, filters, etc.) I finally felt like it was making 450hp.

 

[genXgts]

I recall reading, in the case of Vipers, that DC engineers knew that later Vipers would be softened up (a touch) to meet DOT and EPA regs with upcoming restrictions, this around 96,97. Rather than revise the power rating downwards, which would be a marketing diaster, they kept at it a conservative 450 thruout 96-02, knowing that the 96-98 make well in excess of, and then progressively drop (a touch) in 99 and again in 2000, due to cam overlap, and degrees of duration (in and out). Don't think lift was touched, although it's 1:30 am so I am not trudging out the manual at this hour, thought I would pass on what I recalled reading......

JonB has made a few posts validating such as well, which surely means a heck of alot more than my late night ramblings.....

Of course driveline efficiency % plays a role as well, and that number is in debate too, which muddies up the calcluation to true gross power at the motor!