Mr Incredible

Oh, the HUMANITY! I feel like my best dog just ran off.

261 HP / 274 TQ

Please help me understand how these numbers relate to the more widely quoted DynoJet numbers.

The dyno tech (EJs Dyno in Omaha NE) gave me some conversion numbers, along with some conversion numbers I picked up from various threads.

The operator gave me an estimated flywheel number of 340 hp. This also cooincides with the 1.3 conversion factor listed on the dyno sheet for SAE numbers. This gave me 339hp/356tq.

But with a 17% drivetrain loss, that gives 281hpq/295tq.

But a standard DynoJet conversion of +15% gives me 300hp/315tq.

Pardon my ignorance, but what's it all mean. No way I'm putting those numbers in my sig. Heck, I didn't even want to tell anybody. But I still want to know it I own a POS or whether it really isn't so bad.

help.

92SilverSHO

iTrader: (3)

looks like you got an lt1 instead of an ls1. LOL. Most people dyno on a dynojet so its saying if you dynoed on a dynojet, your numbers would read 300/315 which for an a4 in 98 is pretty decent actually.

Ws6man2000

iTrader: (24)

dont feel bad on a mustang dyno my 00 ws6 only made 280 rwhp with long tubes, y pipe borla catback gutted cats free mods,mti clear lid and asp pulley

Black02SS

iTrader: (36)

Few years ago I made 333rwhp with a cam only car on a Mustang. Same setup did 378rwhp on a dynojet.

oange ss

iTrader: (50)

A4 drivetrain loss would be in the 18-22% neighborhood

s346k

iTrader: (4)

i'd take the dynograph everywhere and use it as bait. "only 261 rwhp"...easy pickins!

what does the car run at the track? unless you're trapping 96-98, don't worry about it.

Mr Incredible

I haven't been to a track yet. There was one up north but it closed this season. There's an 1/8th mile track over in Council Bluffs but I haven't been to scope it out yet.

I need to make time for it, that's for sure.

NYTIGER

Mustang Dyno's will read low as they are loading the the engine.

My 05 GTO read 320HP and 358TQ on an MD. Most Dyno on a Dyno jet around 350/350.

loaf

Dont feel bad, my car made 297whp@4800 with intake, full exhaust, big cam, valvetrain and a tune. granted my fuel pump was cutting out at 4800rpms... A stock LS1 will dyno 240-260 instead of 290-310 like a dynojet. If you post the numbers just also put what kind of dyno. instead post quarter mile time. thats a good benchmark of what kind of power you are making. Dyno's arent really a good benchmark for "numbers" anyway. there is so many variables involved in the process they could fudge your numbers...the weather and the type of dyno. I take quarter mile times more seriously.

Besides when someone is braging about having 350hp and you beat him with 260 he looks really bad :-)

edit: With new fuel pump my numbers are up to 311whp, but its still being tuned. i dont expect over 320whp.

waSStock

A lot of people are under this impression....not true. Dynomite, Dyno Dynamics, Superflow, Mustang, Maha read lower than Dyno Jet because they are accurate. Dyno Jet has a built in "feel good" factor. I think it was the April issue of Hot Rod that interviewed Mark Dobec...(the founder of Dyno Jet) and he explained the "fudge factor"...it made his customers happy to see high numbers.

I am not saying this guys numbers aren't low, but...everything with a grain of salt.

Nickn20

whenever I use dynojet numbers in a et calculator its pretty damn close. any other dyno numbers never work for that either too high or too low. as long as its consistant its all relativity. I will stick with dynojet, its always consistant for me, and I always have a good idea of what the car should run at the track.

waSStock

never said they weren't consistent...they are just high. However, the DynoJet numbers will change depending on which version WinPep Software is used.

Like you said, just stay with the same machine and you'll be fine.

Nickn20

yea I hear ya, and I don't think they are high IMO(at least mine anyway), I just think mustangs are low, based off what cars actually run at the track. I have been working with winpep 7 for years now, I remember the old stuff back when I was just tuning and not operating the dyno, it was quite archaic. I never knew the different versions changed numbers? weird.

67Firebird455

iTrader: (27)

Yeah, I have seen dyno numbers fluxuate THAT much. Now what do you think the big boys (600+rwhp) feel like? Is the variation in measurement only 55rwhp on those cars also, or is it a relative change based on the horsepower made?

Marc 85Z28

iTrader: (8)

Do you have any firsthand experience on or with any type of dyno? They are ALL ACCURATE! Some just measure torque differently, which explains the difference in the numbers.

I've had my car on both a Mustang Dyno and a DynoJet. There is a BIG difference in the way the engine/car behaved on the 2 different dynos, and the lapsed time was different. Both produced accurate results. The DynoJet was an older model which used a fixed value (dyno operated stated roughly between 2800-3000lbs) for the roller resistance (simulated vehicle weight), whereas the MD used my actual raceweight (3700lbs). The rate of acceleration on the DJet was much quicker and thus gave a higher output.

To the original poster, my car "only" put down 380rwhp on the MD, and I've got a H/C full bolt-on A4 car. The DJet resulted in 402rwhp. I care about neither. The MD pull was a tuning deal, and the DJet run was free. Regardless, the car runs better than the MD rwhp would suggest. 119mph in a 380rwhp auto car at 3700lbs.

waSStock

The rate of acceleration on an inertia dyno (DynoJet) is determined by horsepower. The rate of acceleration on a chassis dyno with absorption capability is determined by the absorber. The part you are confused on is how they measure power. An inertia dyno calculates HP by measuring the rate of acceleration. An eddy current or water absorber chassis dyno measures torque with a load cell/strain guage, AND gives credit for accelerating a drum/roller. This is why we can do a steady state test (holding a specific RPM at 100% throttle for example) and see the almost the same HP as an acceleration run. The higher end dynos utilize an engine inertia factor for this.

My original reply to this thread was only to point out what the founder of Dyno Jet had stated.

As far as first hand dyno experience, lol...its what I have done for a living for the past 11 years. I am not trying to knock anyone, there are just so many misconceptions out there, its nuts.

HioSSilver

iTrader: (8)

I dynoed with a bone stock Z28 on a md once and he made 255 rwhp, this was back when I had a ls1 in my SS. I made 305 rwhp with macs w/ orp, airlid, ud pully, ported tb, dual dual slp that came on the car. We dynoed together that day. Cars can very greatly.

dynocar

A couple of points here from the guy who dynoed the car. The car dynoed at 11.8-11.9 after the CATs which is very rich. This is obviously costing HP, possibly 10-20 at the wheels. This engine had a factory rating of 320 FWHP, and we estimated that it has approx 340 FWHP which sounds about right to me with the minor mods done and considering his A/F ratio.

Nickn20, today many HP calculators are fudged to compensate for the fudge factor on some chassis dynos. Until approx the last decade, most HP calculators computed Gross SAE J607 FWHP, the numbers that typically came from engine dynos. If you use such a calculator or dyno, they will read higher then true net SAE J1349 RWHP but closer to the fudged chassis dynos. Now if you use a fudged calculator, it will compute higher then the true Net SAE J1349 found on many of the load controlled chassis dynos on the market.

WaSStock, if you increase the load, such as steady state testing, you will get higher numbers then using the RPM sweep method (less load) if the dyno is working correctly, or better yet, use the reverse sweep by pulling the engine from a high to a low RPM range which will really increase the numbers that some crate engine suppliers use to advertise their HP numbers.

300bhp/ton

Yeah but remember the grain of salt.

Most of these calculators are American, and as the Dynojet is the most common dyno in America it's harly surprising that the calculators have been programmed to accept those numbers.

Also remember HP is only an expression of torque at rpm:

HP = torque (lb ft) x rpm / 5252

An inertia dyno like a Dynojet uses a different calulation but that's becuase it uses a static drag weight as opposed to water or electro-magnetic loading like most other dyno's. Hence they read comparitively high.

Example, take a sn95 Mustang GT (99+) manual, stock.

It has a fairly well established 260bhp SAE Net. Slap it on a Dynoket and you'll get as high as 243rwhp out of it, but anyone would have to be off their rocker to believe that less than 20HP was being lost thru the drivetrain. Most jump to the conclusion, "oh the engine is underated". This is a totally false conclusion and just a result of wishful thinking or a delusional mind.

The answer is of course that the HP being derived by the Dynojet is not the same as the claimed 260bhp SAE Net.

A Mustang dyno will generally give a rwhp number of 210-225rwhp for a stock sn95 Mustang. Using this figure and any of the avaiable equations to derive drivetrain loss and you'll always end up pretty darn close to the manufacturer claimed number.

This same senario always plays out the same for pretty much all vehicles, Mach 1, Terminator, Corvette, Fbody (using known bhp SAE Net figures from Corvette) and so on.

dynocar

300bhp/ton, I agree with you 100%. Also, when we test HP on a chassis dyno we normally use the RPM sweep method. When a manufacturer measures/rates their engines, they use the RPM step method. This in itself can cause the chassis dyno to read approx 5% lower. The sad truth is, if I were to introduce a new brand of chassis dyno tomorrow, it would give the highest numbers and somehow the public would rationalize that it is accurate.