JD Racing

the dyno number between car can be different if he has detonation , different wheel,different tire pressure and even if he has diferent mods on the car it may not help in increase hp

dynoing a car whit out a programer or anything that you can see what are the reading of the sensors , detonation can pull timing off the car and you wont see it and big hp drop

and i did a car the other day that had 35 psi and was crying that his number whent down
i ask him what they he doo different to the car he ssaid nothing but his brother said that he had 45 psi in the tire the firts time he cam over so we put the air back in to 45 psi
and he gaing 4 whp on 233 whp car

and for the dyno not being corect they should check before they talk

i tune car for a leaving im not saying that it may be diferent in a few hp between diferent dyno

i know that when i take a car that i tune and when they come back they have the same hp whit in a few hp diference

and for 10 to 20 whp it not going to make a big diference between car on the high way

i have drive 300 to 600 whp fwd car and 50 whp diference your not going to kill the guy on the high way

ps i dont beleive every thing i read on the net some poeple add in the story to make it sound better

and the guy that made the more hp had a bag of ice on the blower for at least 30 minute before i had time to prepare for the run

and for the dyno not being ajusted corectly there not setteing that i can alter the hp on the dyno other that the corection factor sae, std, uncorected, and a few more setting
and both of them was set at 45 feet sea level that what it is at my shop

and both car were done on the the dyno whit in one hour and for the tac signal i dont even need one for the dyno for whp reading you just wont get you wtq numbers

Red07SSNA

I agree with most of what you wrote -- trying to determine any problem from a computer screen is as close to impossible as it can be. But the statement above is questionable -- the base Cobalts will get their doors blown off by a SC Cobalt and the HP difference is only @50. I have driven cars with 450 HP and a 300 HP car didn't stand a chance against my 450 HP car on the street. And I can attest to the fact that when driving a car with a factory rated 360 HP I got my doors blown off by a built Mopar that according to the owner had 500 HP -- it took me 2 hours to find my doors after that race

JD Racing

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the first one in blue is a stock cobalt sc that came around 2 week before
the second is in red is quicksilver
andthe 3 in green is martin and if you look at his its no as smoot all the way true so the ecu could have been pulling timing out

and for the 300 to 600 whp car i own them and they were fwd and it been since years 2000

BlownedSS

Thanks Danny for posting my numbers!

-Scott

Ryuu600

Ok let me clear something up here. The weight of your wheels WILL make a difference. It's called rotational mass. The heavier the wheel/tire the more power required to turn it, the harder the engine has to work.
The dyno needs to be calibrated to understand the difference in rotational mass.

This is good reading:

Taken from : http://www.sdsefi.com/techdyno.htm

"Chassis dynos are great tuning aids but they only give a approximation of power output as some of the important variables are not accurately controlled. Certain magazines seem to think that results obtained from chassis dynos are the gospel. They are not. In one recent independent test, hp figures varied by 11% simply by doing the runs in different gears and in another test, results varied by almost 4 % by doing the runs with a different wheel/tire combination. Tire alignment has been shown to affect results up to 3% as well. Note that Engine hp DID NOT change here yet the dyno recorded an increase in hp at the wheels. A change in wheels/tires also does not affect true, wheel hp either, only the rate of change on the rollers and the vehicle acceleration on the road. One can only conclude that inaccurate moments of inertia and correction factors are being used."

JD Racing

its a chassy dyno not a engine dyno changing your whell will make a diference yes
buy the result it what you puting down at the ground

how would you ajust for different wheel on the dyno

buy the way it a dynojet dyno

and the hp is calculated buy using the weight of the roller that weight around 6000 pds,
time , and distance and it also depending on the corection factor take humidity , tempeture and barometic presure to make the final numbers

blueta

About the octane booster. If it's stated to "raise your octane by 5 points" that means from the origional 91 to 91.5. Octane boosters for the most part are a waste of $$. So I highly doubt that the increase was helped by that. Also were both cars dyno'ed in the same gears?

martinsmu

They where dyno'ed in the same gear.

Danny, I was by no means trying to put down your dyno, I am just trying to get insight on why there was such a big difference on dyno and not on the street.

One thing to remember is my car is miss alligned, didn't know it could make a difference, none the less 3%(potentially 6-8WHP). My tire pressure was also @ 28PSI that could make a little difference aswell. I also have an old GM flash, ryan had all the updates... maybe that made a difference. Geting the new updates tomorrow....

Also the gas in the car I think was a mix of plus'regular'supreme. So maybe in fact my car was pulling timming on the dyno, and maybe not on the street later when it was colder outside... Impossible to tell without HPtune or proper guages.

I however dont think the bagg of Ice made a BIG difference, but it might of made a 1% so (2-3whp) I was also running the NGK'S that might not be best, maybe I should stay with stock saab plugs. I disagree with the comment on the 50whp not killing a guy on the highway. Having same cars, same gearing, same weight, same tires and rims.... The car with 50whp should be quite a big stronger. In this case 27whp = (11% more whp). This should of made ALOT more diffence than what was happening on the street. I mean he put 1-1'2 cars from 60-110

I'll be back with everything setup right!! :-p hopefully better numbers.

If everything went really wrong, maybe every little nagging thing added up to a significant difference on the dyno, time will tell.

QuikSilverSS

I did have a 235lb passenger and 75lbs worh of luggage for the weekend?? you also have a carbon fibre hood so your car was lighter when we ran from 70mph?? I makes no difference to me if I put down 257whp, on the street your car runs strong and have no doubt that it would be a drivers race between me and you.

QuikSilverSS

I had NGK BKR7E's gapped at 0.031(by mistake, dealer didnt gap them right) I switched to ZEX plugs and noticed a difference in power, as for the comment above about the octane boost I put a whole conatainer(good to treat 60litres, 10 points) in 1/4 tank so it should have been able to bring my octane up to 93-94..think the ecu advanced the timing alittle which in my opinion would affect the numbers, only thing to do is dyno again with Martinsmu, this time i will run 91 octane only and no ice on the supercharger to see if we get simialr results..I believe the dyno was correct and that he treated us very fairly.

BlownedSS

I'll put my car on too

-Scott

martinsmu

haha, no no, iam not trying to argue your # ryan where off, I am actually happy to see good #'s from your car. I am mostly worried something is wrong with mine, but couldn't make sense of it. I will make sure to get good gas next time, make sure I unplugg my battery before installing a new pulley, get the car allignent aswell.

Yeah scott comme dyno with us, how are you likeing your S2? I was at lounsbury's today and saw the menanics working on your car! ;-) Like your boost guage, where did you get it?

BlownedSS

So far loving it will keep me happy for hopefully this summer then i'll need more, lol

The boost guage i can't remember where i got it, but i hate the stock one!!!

-Scott