Dyno Testing H.P vs. Torque

[Balzac]

I have had my truck on two different dyno's with far different results. First time they tested in second gear(automatic), w. o. t and added drag to get 238 HP and 529. 6 lbs. torque.

Yesterday on a Mustang, in drive, @ 44 mph (1760 rpm I believe) 220. 3 HP, 837. 8 lbs. torque. All I have changed between the two are the head gasket and 4" Jardine exhaust Turbo Back.

If I do the calculation on the latest one, assuming the torque is correct( I am not sure that it is) the HP would calculate to 280. 8.

My question is , is there anyone out there with similiar truck and mods that has HP and torque readings.

I invite any theories also.

'95 auto, TST#5 in center, boost elbow, BHAF, 3000 gov. springs.

 

[HoleshotHolset]

On edit: I should have read your post closer...

I don't agree with how they tested your truck..... the usual method is to let it go through O. D. and then as soon as it goes into lockup... . put it to the floor and hold it there until you think your're good and ready to let off... . you'll be able to tell that it's not really accelerating much faster once you hit the 'brick wall'



Some trucks will kick down out of O. D. or disengage the TCC, which won't load the engine enough to make the HP..... try not to worry so much about the torque... if you're making good HP, the torque is there and there's more if it available well below the rpm at which your peak HP was.



Your #'s are all over the place..... some consistancy is needed otherwise you need to just throw the #'s out and do it again.



Horsepower = torque * rpm * 1/5252



I figured out my torque from my dyno runs using the above equation. Do some substitution for the variables and away you go.



That's how I came up with 714ft/lbs of torque at 258. 6rwhp, which was @ about 1950rpm..... on my last dyno run. See sig. for BOMBS (those runs were without the GSK..... )



HTH,



Matt

 

[BushWakr - RIP]

I'm a little confused on an associated issue here. There are Mustang Dyno's, chassis dyno's, etc, etc. What's what???

Is one better than the other and why. I ask because I'm planning on doing some runs with my truck and don't want to waste my time or money.



Any thoughts??



bob

 

[JHansen]

I bounced some of the #'s that came up on Saturday off Scott when we had dinner... . he says he's seen some real high #'s come off that dyno before. I guess we'll see what Andy comes up with when he straps onto his buddy's Mustang with all the proper inputs-I'm wagering his #'s then will match up closer to Waterous' than PAAL's... . time will tell I guess.



Bob, the dyno that was used Saturday was a Mustang chassis dyno. It uses basically a big jesus electric generator to create the drag to load the truck. I think the load is fixed-and the dyno interprets how quickly you spin the rollers up to get torque #'s which are then converted to horsepower. They were loading the trucks up in a high gear (not sure which one exactly) at low rpm and then laying 'er to the boards until they hit governed RPM. Still not sure really how that shop's computer converts it as they aren't hooking up the RPM trace to the engine-maybe they dyno in direct. Still in hindsight I'm thinking they'd need to know at least the tire size and gear ratio to determine driveshaft RPM and therefore engine RPM. Maybe there's something there I'm missing... ... I never claimed to be the brightest bulb on the tree .



AFAIK, the Dynojet dynos use weighted rollers to create the drag-and again the computer interprets how fast you spin them up to determine #'s. The Superflow that we dynoed on in December is an adjustable load-the operator determines how hard the truck is loaded. On that one he had us with the standards in 5th gear, told us to put it to WOT, and then started loading the truck until he pulled it down to the point it wasn't making any bigger #'s.



HTH

Jason

 

[HoleshotHolset]

With your TCC engaged (and hopefully not slipping... ) you should 'in theory' be putting pretty much all of the engine's power to the rubber (same holds true for a healty manual transmission/clutch)... . since this should end up being a direct relationship... . just read the MPH from the dyno sheet where you got peak HP and then hop in the truck and see what RPM you get at that MPH..... then use that RPM in the equation I mentioned previously... . You don't need an RPM signal from the engine to figure out what RPM it is at... . we just need to do a little deductive reasoning, and hope our drivetrain isn't failing.



Tire size/gear ratio..... doesn't really matter as far as what MPH the dyno says. As long as you're running everything the same on the street, go out and see what RPM the peak HP - MPH is happening at.



Big tires and low (numerically) gears put more load on the engine... . and with more load = more power.



FWIW, I've had really good luck with DynoJet - very repeatable results.



Matt

 

[JHansen]

I understand exactly what you're saying-I just question how the dyno we were at on Saturday can give you a horsepower number when they aren't making allowances for different gear ratios and/or tire sizes. In fact a lot of the dyno runs had the truck brand scratched out and pen-scribbled in the real truck-kinda poor to get a Ford dyno sheet for your superior Dodge run.



The fella that I mentioned in my first post-Andy-has a '97 (I think) 3500 4x4 QC with a 5 spd. He's got exhaust work (I think 4" all the way back but not sure) and a 270 hp plate... ... . but not much else-Jim please jump in here and correct me if I'm wrong. He punched out 283 (?-within 1 or 2 hp of this #) hp which IIRC was pretty close to the #'s he made in Dec. on the Superflow. But this particular Mustang dyno measured him at a peak torque of over 900 ft. lbs which computed at that particular RPM to 383 hp... ..... something isn't right IMO. I should have strapped down to see what I could do... . maybe I could have generated a 1000 ft-lb. sheet as I did a shade better than Andy in December! I don't think we were getting real #'s off this particular dyno-I saw a stocker ETH with no miles to speak of generate over 620 of torque... I also saw a Duramax generate 210hp/580 torque ... ... We'll see what Andy comes out with when he runs on his buddy's Mustang with proper inputs.



I ain't no dyno guru either-still trying to make sense of what I've seen!



Jason

 

[RottnDogue]

Originally posted by HoleshotHolset

On edit Horsepower = torque * rpm * 1/5252



I figured out my torque from my dyno runs using the above equation. Do some substitution for the variables and away you go.



That's how I came up with 714ft/lbs of torque at 258. 6rwhp, which was @ about 1950rpm..... on my last dyno run. See sig. for BOMBS (those runs were without the GSK..... )



HTH,



Matt

For the Math impaired

T=5252xHP/RPM

 

[Balzac]

Jason,

you have the correct info on Andy's truck. 383 HP is too-oo high,

and my torque reading of 837 also not right.

Jim

 

[JHansen]

You know as a polite Canadian I never try to call somebody down... but I sure wanted to call BS on Saturday . Scott had told me before that their dyno was a little extravagant to put it politely..... guess I should have run to see if I could crank out the big #'s. Really makes those Duramax #'s look poor though doesn't it?



I really wish I had all the BOMBs on right now that I aspire to-I'd love to take it over to Cummins and bet the dyno guy I could pull with the average N14 (460 at the flywheel). Think there'd be a few jaws dropping?



We'll see what Andy gets out of his next dyno session-I gave him my cell # to let me know what came out of it.



Jason

 

[HoleshotHolset]

Us jerks here in Mass. wouldn't think twice about calling BS on anything we don't agree with. :-{} Especially if we're payin' money for a service or product.



We get our retribution on the roadways where we all drive like idiots in our many rotaries or roundabouts... .



Matt

 

[RottnDogue]

Originally posted by HoleshotHolset

Us jerks here in Mass. wouldn't think twice about calling BS on anything we don't agree with. :-{} Especially if we're payin' money for a service or product.



We get our retribution on the roadways where we all drive like idiots in our many rotaries or roundabouts... .



Matt

Now Matt the people from the NorthEast aren't that bad... ..... Oh Ok, Yes they are..... But, once You learn how to ignore them

Or be a Bigger D$*K then the other person, both work..... It's not so bad

 

[Balzac]

Jason,

Tell us more about the Duramax. Was it at PAAL on Saturday?

I had to leave early.

Anyone else out there seen a Dmax on a dyno?

Jim

 

[JHansen]

Yes it was Jim-they ran it around 1:00 or so. I only got to watch it run stock-they were installing a chip on it in the parking lot to run it again but I had already told Scott and Jason that I'd meet them up in the NE for dinner at 1:30-so I never got to see it run with the BD chip. Like I said it only cranked out 210 hp/580 torque on the dyno run I saw-on a dyno which for all intents and purposes seems to be biased to the high side of things..... remember that stocker ETH/DEE that cranked out more than 620 of torque. I can't remember the HP #'s from its run though.



Andy would know what it cranked out modded. He was gonna give me a call on my cell to let me know but I never heard from him..... no big deal anyways as I was just mildly curious. Next time you're talking to him ask him-sure he wrote it down somewhere.



J