kyosuke

when you google the car this comes up

Model: 2006 Mercedes-Benz S-Class
Number of cylinders: 8
Horsepower: 493 hp
MPG: 15 city / 22 highway
Engine: 5.4 L V8
Curb weight: 4,300 lbs
Dimensions: 199-203″ L x 73″ W x 57″ H
Torque: 516 lb-ft

but when you goto renntech itll state stock hp is really 354/355
i hear a mustang dyno is way lower so does anyone know if like there is a universal dyno that everyone uses ?

mfl

Both are correct. The early S55 AMG had 345 HP. In 2003 a compressor was added which raised HP to 500 (European spec)

kyosuke

but why would all these companies be quoting hp specs from the most earliest versions of the car

VinnyT

You have to take in the drivetrain loss. Those numbers are usually at the flywheel. When you factor in the driveshaft, transmission and rear end, you might be seeing a 50-85 hp loss.

Then you have the mileage of the engine, condition of the plugs, coil packs, air filters, fuel grade, temp of the motor, etc. All these things will sway those numbers dramatically.

cmpcpro

I don't think the mileage of the motor gives much of a difference at all unless it's been damaged or it has no compression which would be more from abuse or overheating etc.. there was an E55 with over 200k miles that pulled like a brand new car.. I think the other factors like plugs coils etc would make a much bigger difference.

StarvingArtist

Sellers estimate at the crank, tuners measure at the wheels.

auburn2

In truth the answer to your question is "it depends"

Specifically it depends on air temperature, engine temperature, humidity, engine condition, plugs, where you measure, how you measure, fuel and your specific engine.

If you want a good estimate start with the manufacturers published numbers for your year. That will be a pretty good number for net HP at the crank for an average engine on a standard day. That won't answer how much your car has but it will answer what the average car would have on the average day when new (discounting purposeful dishonesty by the manufacturer).

Going beyond that introduces a lot of variables.

1. Some cars are hot some and some are slugs, two "identical" cars can roll off the lot on the same day and produce 20 hp difference on the dyno.

2. You lose about 18% hp on a chassis dyno vs an engine dyno for an automatic transmission. That is an average number that varies by the specific dyno used, the specific transmission in question and the gear used.

3. Temperature, pressure and humidity all affect hp.

GrepAwk

Kyosuke: My opinion is because Renntech is marketing to the pre-2003 AMG model year owners. They are letting a slight mistake go uncorrected. Or maybe you are the first to find this omission. Do they show a range of years? (I can't see the font is too small in ur post).

You can probably justify a Renntech kit cost added to the cost of non-supercharged cars thru MY 2002. The Cost per Horsepower added looks pretty good. These normally aspirated S55's are going for low $ in the used market now. It makes a great project car if you find one in excellent condition. Just be careful to check whether they had the same improved cylinder walls and rods to handle the new power (I don't remember).

But there is not a lot of room left to improve the supercharged Komressor vehicles that came out in MY 2003. The OE AMG supercharger and tune already boosted the older cars by 150HP. Are you going to pay Renntech to get another 50HP by removing the OE supercharger and putting on their own with an additional tune to get to the limits where the transmission becomes the weakest link? The cost/horsepower added for such an upgrade is, in my opinion, not worth the time/money/reduced reliability.

FYI, the difference in MSRP from 2002 to 2003 Model Year was around $14k. ($103k increased to $117k on notes when I was shopping these). So $14k list price bought you 148HP gain if you could have waited one extra year.

GrepAwk

Ah, now I can read their screenshot. It's as I suggested, they are marketing to owners of S55, up to and including MY 2002. And they are only offering an ECU tune with that product, not a supercharger. They really ought to put applicable model years on their spec sheet. Then again, most owners of these cars already know what they have in hand.