This is going to start a crap fest and quite honestly, that's exactly why I am posting it

We ALL get caught up more and more in the dyno numbers that are out there. Over the last few weeks I have been meaning to make this post and after this last weekend when we dyno'd 25 Subaru's and 2 EVO's at a local meet that was held here I was even more determined to voice my opinion

I am constantly asked questions like why the difference in HP numbers from one dyno to another? Who's numbers are right? Etc., etc.

Well as I have admitted I am no engineer and the only answer I can ever come up with is each company must have a different idea about the loss a car has to the wheels.

I keep looking at Dynojet numbers and how "high" they are. There are other dynos that are like this too. Land and Sea and Dynapak are two I can say for sure. Dynapak actually seems to spit out numbers almost identical to Dynojet actually.

Dynojet was the first widely used chassis dyno. Other companies that followed apparently thought it would be a good idea to make their dynos spit out numbers close to the "originator". That makes sense to me too.

Problem is the more of these numbers that are out there the more I started to relate what the Dynojet reads to what would be seen at the flywheel rather than at the wheels.

There are exceptions to this of course. A car with a very loose torque converter, even on a Dynojet, will not come close to putting it's flywheel numbers to the ground. My brother owns a Buick Regal that he put a small block Chevy in, for example. The engine was dyno'd across the street from here on an engine dyno. On this dyno it made 497 crank HP. After the engine was installed, alternator, mechanical fuel pump, trans, rear end and a loose 10" converter the power to the ground on our old Dynojet was only 370 whp. Quite a bit of loss to support the example I am trying to make BUT the torque converter I would say is the major culprite in this example. It was a non lock up unit and I would venture to say that even at 7,000 rpm had over 15% slippage. The EVO's though seem to be close and without the slippage through a torque converter/auto trans should atleast be closer.

Case in point is the 2006 EVO9 that Tym brought here. This car made 281 whp on the his Dynojet. That's pretty damn close to the factory rating of 286 hp.

Then we have all the formulas floating around about who's numbers are right. I myself have said that I felt the Dynojet numbers are closer to "right" as I have had my mind set that it takes "___" HP to run a certain ET/MPH in the 1/4 mile. There are formulas to figure out how much HP your car makes based on the 1/4 mile MPH and weight of the car. There is the old Moroso slide rule for doing this too. The numbers on the slide rule and misc formulas match fairly closely with the Dynojet numbers I see.

These numbers are all based on flywheel HP though, not wheel HP.

Just some thoughts....

David Buschur
www.buschurracing.com

 

DAVE...

Very Interesting thoughts..and I'm sure it's gonna turn into one of those (???) threads

I don't think that ALL Dynojets read the same of very close to flywheel HP. I am not no expert though...this is from my personal hands-on experience & my friends cars..using the dynojet.

I have noticed a consistent loss of around 15-20% from factory rated 'FLYWHEEL' horsepower when cars are dynoed on our local 2wd & 4wd dynojets here.

For Example:

I use to be a HONDA guy..turbo & Nat. aspirated..when I dynoed these cars STOCK they would make like 115-120 stock..these engines where factory rated @ 140 'flywheel' HP...15% loss from flywheel.

My EVO's (had an Evo 6 & now an Evo 7) dynoed stock 240-245 wheel hp (flywheel rated @ 286 hp) these horsepower rating also showed around a 15% loss from stock flywheel horsepower.

I am basing this on STOCK cars. I DO BELIEVE the DynoJet reads much higher than alot of other Dyno's out there, but I DO NOT BELIEVE it is reading flywheel Horse Power.

As I said I'm not an expert this is what I have seen in my personal cars & my friends cars..before mod's.

Just my 2 cents as they say...

 

I really just believe the 05 VIIIs and 06 IXs were underrated at the crank by Mitsubishi. I don't think it's that the Dynojets are reading so high, but rather that the published flywheel numbers are way too low. It just doesn't seem to make sense that the 03/04s who put down 225-235 on a Dynojet would only have ~225-235 at the flywheel. I think their Dynojet figures are proper as well as their published 271hp at the crank. Once you get to 05, though, the numbers get thrown off. The trap speeds increased by 2mph, but the published HP only went up by 5. Next, with 06s, the trap speeds increased again by 2mph, but only a 10hp increase at the crank. The cars are putting down the times/speeds at the track to prove their power, but the published numbers seem too low to me.

 

Warrtalon I am with you on this.

Sean

 

Why not start a donation box for sticking a stock Evo motor on the engine dyno, then stick it back in the car and do a pull on your dyno (or vice versa) I would kick down some $$ for that.

 

I see numbers all over the map with Evos on any Dyno lately. On our old local mustang AWD a stock Evo would put down 206-210 whp which i would look at as my starting point, my car without cams and injectors was putting down 270 whp about 6 months ago. For me that was an accomplishment. Now i have seen data changed where you can get and extra, lets say 30 whp out of the same dyno...by just changing some numbers!!! So this brings me to MY conclusion... Dyno numbers don't mean sh|t to anybody but myself to see my own gains over what my car did stock on the same dyno. Other people that see those numbers will say that they are low...whatever its the Trap speeds that count isn't it. I can get my car to read 350 whp as is but if i go to the strip and pass at 110 mph its not going to impress people anymore is it....Everytime i see big dyno numbers posted on Evom i never even look at the thread unless there is "before and after" dyno sheets posted

 

Dave just needs to end this and take his RS to Switzer's. I'm waiting for that 450whp+ dyno chart

 

i tend to disagree about dynojets reading flywheel power. i've done a lot of tuning on 2wd hondas and the results tend to agree with the 10-15% drivetrain loss.

 

I agree with you as well on this warrtalon...

I was thinking the same thing upon looking at the trap speeds/flywheel ratings awahile ago..

Each dynojet isnt created equal imo...

 

Dang, come on, there should be more arguements than this. Nobody is going to flat out tell me I'm a idiot??

Warrtalon, I can't agree with what you said about the power numbers and the EVO9's being that much stronger. On our dyno all EVO's in decent condition running 93-94 octane make between 200-215, it's actually all closer to 208 or so but that is as wide a range as they go, 200-215.

O.K. so anyway. I get this months Hot Rod magazine in the mail. There is an article in it, "The Truth Meter". It's about the Mark Dobeck, the originator of the Dynoet. Basics of the story is he was just building kits to re-jet carbs back in the 1980's. He needed a way to hook a large piece of equipment to a motorcycle and test AFR's and such. Well since that was impossible he decided to make a portable roller to run the motorcycles on to use his test equipment. He then got an idea to make this portable roller calculate HP.

At the time the most powerful motorcycle being built was a V Max. Here is the story from there, just a paragraph:

"Dynojets final number-fudge was arbitrarily based on a number from the most powerful road-going motorcycle of the time, the '85 1,200 cc Yamaha V Max. The VMax had 145 advertised factroy hosepower, which was far above the raw 90 hp number spit out by the formula. " (*not a quote->they are talking about the formula that they came up with to figure out the hp based on the time it took to accelerate the rolls of the dyno they built) "Meanwhile, existing aftermarket torque-cell engine dynamometers delivered numbers that clustered around 120. Always a pragmatist, Dobeck finally ordered his Chief Engineer to doctor the math so tha the Dynojet 100 measured 120 hp for a stock VMax. And that was that: For once and forever, the power of everything else in the world would be relative to the '85 Ymaha VMax and a fudged imaginary number."

Anyway, the proof is in the story about what I was thinking lately. Pick up the March 2006 issue of Hot Rod and read for yourself.

The Dynojet numbers mean basically nothing. It is a tuning tool to make baseline runs from and measure you gains. The actual numbers are inflated and that is FACT based on the inventor himself.

Wow.

David Buschur
www.buschurracing.com

 

+1

 

there is a great article on dynojet and its history in 'sports car international', latest issue with orange exige on cover.

recommended reading.

n

 

Dave, does that mean that every dyno number you ever posted of every part you make or tried BS?(when you had the 2wd dyno) I would guess so Not to question you, but if your RS is making 400whp on your dyno then that would mean that on a Dynojet it may be around 450-460 right? That is what a full GT30r turbo with an equal length manifold and external WG would make on a Dynojet. Something doesnt make sense here since you still have a stock based turbo. That would mean that all but the 35r kit you make senseless mods. Maybe its just me.

 

ha ha.. the mag I spoke of sounds very similar to that, if not verbatum.


n

 

Thanks David,

This answered a lot of my questions concerning dynos and how they came about.

It is a fudged number because you coulda built an engine back then and said it was 16hp and then you would build your dyno to read 16hp when it dyno'd that engine because thats how you would programmed it, the computer needs basically a visual baseline to determine how much higher or lower it is and uses that specific engine to determine it. It makes perfect sense that dynos in the beginning read as high as they were advertised or people woulda felt ripped off.