darkhorse

I brought my car to have it dynoed at this one shop after some modifications and I put down 295 hp at the wheels. A few days later I went to thsi other shop up the block and dynoed it again without changing anything, and put down 374 hp at the wheels. Thinking something was amiss I went to get a third opinion on another dyno and that time I put down194 hp at the wheels, so then I went out to the west coast and tried again and put out 317 hp at the wheels, then I went to Colorado and tried it there and put down 470 hp at the wheels. Now that I was really confused, I pulled the motor and put it on an engine dyno and only made 250 hp at the flywheel, and when I came back to NJ, tried it again on a guys engine dyno and made 13 hp at the flywheel, but the guy forgot to hook up one of the inputs, so we tried it again and this time it made 700 hp at the flywheel. Then we realized that the car was parked with its tires on the hose for the water supply, hence the high reading.

So my issue is this, I have dynoed my car 8 times without changing a thing, and have gotten 8 different numbers. So how do I know what I am really putting down? Do I add the first number to the second, divide by the humidity, take the square root of the date on the calendar and subtract what hour of the day it is? Or do I take the number of miles that are on the odometer, divide by two, add how many days it is until my birthday, and subtract what the temperature is that day?

The other thing I cant figure out is that a friend of mine runs a Chevy big block block, with 460 hp, weighs 3200 lbs without him in it, is like driving down the track with a 4x8 sheet of plywood tied flat to the front and runs 10.70s in the 1/4 all day long??????


Something doesnt add up.

Funky

I don't think this formula works on leap years. IMO, the best metric for "yard stick'ing" power output is 1/4mile trapspeed.

Dynos should just be used for tuning, not pee-pee measuring contests.

bolsen

iTrader: (2)

Hmmm seems that you haven't done the butt dyno yet. Perhaps you should do that, cause that way you can feel the 2 extra hp your mister gave you.

darkhorse

My point excactly...... seems like everyone is racing dynoes though

David@Vishnu

iTrader: (2)

Tell me about it I get a dozen "Guess the HP questions" and swammi " Predict the output of so and so's dyno 500 miles away from me and 1500 away from you" A day. Everybody knows the answer and the problem but I guess its human nature to fixate on it anyway.

4ringturncoat

iTrader: (21)

I never got it either...I will show you my E.T. and thats what ME and the car can do! Who cares what a dyno says, if you can't drive the car whats the point anyway.

darkhorse

I knew I wasnt nuts. I dont get it though, for the amount of time and money most people are spending on dyno time, you can probably buy 10 times the amount of track time and go get some numbers that woudl hold water. But it seems that most of these guys pushing 500 whp are still lucky to run in the 11's and 12's so it sounds better when you put up the dyno sheet.

It cracks me up, everyone shluld go to Tony Baloneys ultimate power shop in Bull****ville, his dyno reads higher than most, and for some extra rupels, he can add another 100 hp to the sheet so you can wow all your freinds.

bishiboy

iTrader: (10)

Dyno's are tuning tools and should be used as such. Quoting numbers is a joke.
Use the same dyno with the same settings to determine if your tuning to right way.
My dyno guy said, "you want big numbers, I can take out the load and you'll show50-75 more".
I don't care for specific numbers, use the dyno for what it's for.
Horsepower shootouts are the exception. With these you are using the same dyno at the same, relatively, time. Then comparable numbers matter.
By the way, My Dyno-scan PDA says I make just shy of 400hp with the stock turbo, I should be THE MAN....but I'm not

kevo

iTrader: (7)

exactly, there is a guy here got his car tuned at TT with 34x hp and ran 12.6@111 and then went to Pruven and dynoed at 308hp without adding mods or tuning, after tunning he got 37xhp and go to the track again and ran a 12.6@111 again.

matt55

iTrader: (12)

He went from 12.6@111 to " 12.41@113.9 " But dyno sheets are great for the web , 1/4 mph is just great fun

bishiboy

iTrader: (10)

They are both very subjective.
Too much of a varience in weather, altitude, octane, humidity, traction, type of dyno, driver for 1/4 mile, bla bla bla.
The internet guys love both, some take it as the only truth, which it isn't.
How many guys on this forum see a guy run 450hp on an east coast Dynojet with a certain set-up and see another guy run 300hp on Shiv's Dyno with a certain set-up and instantly think the east coast guy's set-up is the best and buy the same stuff without looking into the particulars of each?
I do my own research before I buy anything.

kevo

iTrader: (7)

And you ran faster than him with only stage 1? Wow

metaphysical

iTrader: (3)

Dyno's can be useful for some shops in the Metro areas. Imagine trying to tune on Route 1 in NJ.

EricJ@AMS

iTrader: (1)

So your saying that shops should develop new products without dynoing the car they were made for and sell them to you totally untested?

"Buy our new Turbo kit or Intercooler, we have no idea if it works or what its limitations are, but we THINK its good"

Shops use dynos to test the products that they sell which helps you in the end result. We test many things on our car to help produce the best turbo kit possible. We monitor pressure drop across the IC core, we monitor exhaust manifold backpressure to make sure that the header or exhuast housing isnt becoming a restrction when trying to achieve a certain HP level. If we see that it does, we'll do whatever it takes to change it so that you get a better product.

Dynos are GREAT tools for tuning. Theres nothing like putting a car up on one, and being able to simulate driving down the road at whatever speed you want or accelerate as fast as you want and nothing get in the way. Not to mention not having to worry about taking your eyes off the road to mess with the afc/standalone.

I personally thing a Dyno sheet is a much more accurate measure of how fast a car is. Time slips can vary because your adding the equation of the human driving it. You can take a 500 whp car with a bad driver and it will go much slower than a 400 whp car with a perfect driver. There are differnet types of dynos that will vary #s from the other types, but each brand has its own calculations to try to compensate for weather conditions to make every run as equal as possible.

It all boils down to what Bishiboy said, "Do your own research before buying anything".

darkhorse

No, I am not saying that shops shouldnt test products. But I have seen more than a few products that were "dyno tested" that when you put them on a car, it loses power. But picture this, you are a guy making a product, you put all the time and money into developement and marketing, and it turns out it really isnt all that great, so now what do you do. You can always fudge the numbers. Dynos are tuning tools, true, but how can you possibly use it as a benchmark when it staring you in the face plain as day all over the internet that everyone is getting different numbers on a dyno? I can give you another handful of of hp on a dyno if I freeze your intercooler, or have 15 lbs of ice bags on the engine, or pull air in from an outside source. I cnat tell you how many cars I have driven that have dynoed at crazy numbers that feel slow as all hell when you drive them, you sit there and say "How much hp did they tell you this had?"

I probably shoudlnt have even started with this thread, I just thought it was amazing how everyone is dyno this and dyno that, yet no one stops and says, "wait a minute, what the heck is going on? These numbers make no sense at all."

The performance of the car should be the last word, not the dyno, or flowbench, or computer simulation.