Competition Dyno Talk

[DavidTD]

Richard,



The truck we used to demonstrate our dynos at the PRI trade show in Indy this year was a two week old 2005 2500 CTD with auto trans. Bone stock, it made 230/400 and change. We could hardly believe it either, as my bone stock 1996 makes just a hair under 180/420 with a sloppy automatic and over 120k on the clock. Bully Dog Diesel Performance gave us a new Power Pup Programmer to try out, it supposedly having a 160hp program in it.



Well, it didn't exactly make an extra 160hp. More like 110hp, if memory serves. Still, it made the truck an absolute HOOT to drive, especially in 4wd on the rain slick streets.



Long story short, what you said is probably more true than you realize. Reality is pretty depressing, huh?

Brian, since you have the superior dyno, why does it show a 95hp loss from flywheel to rear tire? Why does my machine measure 270 - 280 on nearly everyone of these trucks I do? These numbers are either uncorrected or no more than 1. 02 correction. The question I'd like to hear answered is why 1. 17 correction on a dyno that is at sea-level? Why is it I have never seen even 10% correction anywhere I have been on the east coast?

 

[J.Davy]

Any of you guys who care , do the google search -turbocharged engine correction factor-and you will see that s. a. e. correction factors do not apply to turbocharged engines and if guys are applying them to ignore it and use the uncorrected number. There could be another correction factor but it is going to be different. What this guy does not understand is there is limits to engines, and when you are building a engine to make its max power at sealevel you add more air as you go up in elevation to compensate. If you reverese engineer the engine say build it at 8000 ' you would have to detune it to run it at sea level so that it would not blow up. We snowmobile anywhere from sealevel to 10000' and the only sleds that can still run have decent at those upper altitudes are turbocharged. They can run 15 psi up top and only 5 at he bottom or they will blow up. You dyno that engine up top and try to correct it useing s. a. e. correction it is going to set some sort of world record for h. p. Kevin Cameron's articles on this stuff are good info.

 

[DavidTD]

Easy. Because customers seem to think that chassis dynos measure crankshaft HP.



The truth of the matter is this: Chassis dynos only measure HP at the wheels. There will ALWAYS be driveline losses, no matter if the vehicle tested has an automatic transmission, a manual transmission, or a direct drive through nothing but the rear end assembly. The 1. 17 correction is what it takes to turn the MEASURED rear wheel HP number into the higher crankshaft HP number that everyone thinks they need to see.



This correction factor is automatically built into some dynos, which is why these dynos (no names, no flames) consistantly yield remarkably higher dyno test results than the other brands of machine. We are very clear to our customers that they are buying a chassis dyno, and that adding such external corrections to give the 'effect' of simulated crankshaft HP testing is ill-advised. Such practices create a great deal of confusion and frustration when customers find that the test results will vary wildly from one dyno to another depending on how they've set this external correction.



Make sense?

Huh? I know of no Chassis dyno that corrects to Flywheel HP. There is no way to know because the drivetrain loss will vary GREATLY depending on set-up. Correction factors are designed to "adjust" the actual (uncorrected rear wheel hp/tq as measured) to the standard atmospheric conditions established for SAE. Meaning, it is designed to allow you to compare a run in 90 degree, humid summer air with one in colder, dry air from a winter day. Corrected, in theory, the runs would be the same. Uncorrected you would make more power in the winter, less in the summer. Chassis dyno's do not correct to flywheel power, or at least mine doesn't.



The general accepted drivetrain loss is 15% for manuals, 20% for automatics. Testing in lock-up with our diesels will fall somewhere in between. Most 305hp Cummins make about 260hp. Most 300hp Dmax's make 255-260hp with the speed limiter removed or using a tech II, 240's without. Most 325hp Cummins make 270-280. My 205 flywheel hp T-bird makes 170's. Stock 01 235/460 24v - makes 200-205 and 410-420 tq. These are many actual trucks run all over the east coast.



As far as correction, what I like is when I can dyno in Muncie and make 692hp in June. Make 699 in Atlanta in September, and then make 699hp in McDonough in November. Uncorrected, these numbers vary, corrected same truck, same tune, same dyno, but different weather and location and you see the number is pretty reliable.

 

[TractorNut]

"Inertia dyno"

I have a question about the different dynos. . since this seems to be on the topic... what do your rollers weigh??? (rolling mass) Does dynojet have options when purchasing a dyno??? As far as the mass of the rollers?? I would think this would make a big difference in how the turbo chargers act on different dynos. .

Brian?? I am also curious about your dyno... when you run most trucks/cars. . in a group event. . do you have the dyno set as Interia only?? Or a different load factor for a group of vechicals based on experience??? And I'm guessing that if you are placing a simulated load on the vechical that is hooked to a load cell and figured into the equation of the HP/TQ output???

Just curious. . and trying to learn here...

I have run engine and PTO dynos (M&W and A&W's). . and I understand the Interia dynos. . Just trying to figure out some of the details...

Thanks,

Bryan

 

[J.Davy]

Brian it took a couple days for you to realize that diesels are fuel dependant ,it was big of you to say I was actually right about something,you must have asked one of your buds or looked it up but it is good to see you are starting to come around. You keep researching all this stuff and you will eventually figure it out ,its not rocket science.

 

[DavidTD]

Take a look at this page:



http://www.twinturbov8.com/dynostuff.htm



You tell me what's going on. It sure looks to me like DJ is trying to put those driveline losses back into the test results.

Brian - Surely you are not gonna try and tell me that because your machine read lower than the others that the others have to be wrong. In the case you provided, the dynojet made 476, the dynopack 504, and yours 409 all from 560 fwHP. Not knowing this vehicle, The dyno jet fell within acceptable specs for loss. The dyno pac hooks directly to the axles, you remove the tire/wheels. Less rotating mass, less loss. Then your machine with 27% loss. This makes your numbers correct how?

 

[banshee]

Take a look at this page:



http://www.twinturbov8.com/dynostuff.htm



You tell me what's going on. It sure looks to me like DJ is trying to put those driveline losses back into the test results.

The dynojet and dyno pak numbers look the most realistic to me!! 46% driveline loss??? LOL Come on!!

 

[banshee]

Sorry, but when I shift from 2WD to 4WD I don't lose an additional 13% (You list 33% for 2WD and 46% from 4WD). I've run at the track and on the street from both driveline combos, and the losses are very minimal when at speed. Maybe 3-5 percent, but not 13. Track times just don't back up that data.

 

[Gary - K7GLD]

"Sorry, but when I shift from 2WD to 4WD I don't lose an additional 13% (You list 33% for 2WD and 46% from 4WD). I've run at the track and on the street from both driveline combos, and the losses are very minimal when at speed. Maybe 3-5 percent, but not 13. Track times just don't back up that data. "



Without test documentation, pretty hard to back up that claim reliably - if using track times, the added traction in 4x4 could easily offset driveline power drain, and slant results...

 

[Timbeaux38]

I don't know about you guys, but I'm chomping at the bit to do business with Brian, With his customer-friendly demeanor, and his ability to gauge the intelligence of the learning disabled is unbelieveable- He can tell how smart you are without even meeting you- Brian, it is clear that you have lots of knowledge, but your delivery sucks. I'm shure that you have a great product that may be superior to others out there, but I would not purchase ANYTHING from you based on your comments on this board. You must be one hell of a plastic salesman, because it would appear that those who have bought your product have the wrong image of you. It is far easier to sell the attributes and benefits of your product than bashing someone elses IMO. I'm OK withthe fact that you will probably say I have no Idea what I'm talking about and that you have graduated from the Dale Carnegie school of sales and such, so let me have it- But I do know this: If you conduct yourself in the business world like you do on this board, you are not going to sell tons of product, nor are you going to make tons of friends.



Cheers,



Tim

 

[Gary - K7GLD]

... Sure would be neat if we could stay on topic, and leave senseless personality analysis and attacks back in the schoolyard...

 

[banshee]

"Sorry, but when I shift from 2WD to 4WD I don't lose an additional 13% (You list 33% for 2WD and 46% from 4WD). I've run at the track and on the street from both driveline combos, and the losses are very minimal when at speed. Maybe 3-5 percent, but not 13. Track times just don't back up that data. "



Without test documentation, pretty hard to back up that claim reliably - if using track times, the added traction in 4x4 could easily offset driveline power drain, and slant results...

ETs are usually a couple tenths slower, but the trap speeds (which are directly related to how much power you are putting to the ground and are much more consistent with respect to your power output) are always VERY close... within a couple/few tenths of a MPH. Certainly NOT 13% slower. The same results are seen when racing from 70mph rolls. Traction is no issue in those races, and after having done it literally hundreds of times I can attest that the results are repeatable. Think what you guys want, but those numbers are bogus.

 

[Billy Diesel]

ETs are usually a couple tenths slower, but the trap speeds (which are directly related to how much power you are putting to the ground and are much more consistent with respect to your power output) are always VERY close... within a couple/few tenths of a MPH. Certainly NOT 13% slower. The same results are seen when racing from 70mph rolls. Traction is no issue in those races, and after having done it literally hundreds of times I can attest that the results are repeatable. Think what you guys want, but those numbers are bogus.

On our trucks, especially the newer ones, how much less rotating mass is there between 2by and 4by?? You are already spinning 2 extra axle shafts, a differential, a drive shaft, and some transfer case internals. All that happens when you throw the lever is the front is connected to the rear. I am not surprised you are not seeing a huge difference between 2by and 4by.



--

-Will

 

[Gary - K7GLD]

"ETs are usually a couple tenths slower, but the trap speeds (which are directly related to how much power you are putting to the ground and are much more consistent with respect to your power output) are always VERY close... within a couple/few tenths of a MPH. "



As a matter of curiosity and discussion, in a vehicle such as the one you are using for racing, about how much HP is required to gain or lose a tenth of a second? I know there is an equation for figuring that - maybe you are familiar with it?



Whatever it is, I'm pretty certain that 10% less in drivetrain loss does NOT equate to 10% lower trap times...

 

[DavidTD]

"ETs are usually a couple tenths slower, but the trap speeds (which are directly related to how much power you are putting to the ground and are much more consistent with respect to your power output) are always VERY close... within a couple/few tenths of a MPH. "



As a matter of curiosity and discussion, in a vehicle such as the one you are using for racing, about how much HP is required to gain or lose a tenth of a second? I know there is an equation for figuring that - maybe you are familiar with it?



Whatever it is, I'm pretty certain that 10% less in drivetrain loss does NOT equate to 10% lower trap times...

Gary, that is a tough question. 1/4 mile speeds are directly relational to HP available. ET is directly relational to traction available.

 

[Gary - K7GLD]

"Gary, that is a tough question. 1/4 mile speeds are directly relational to HP available. ET is directly relational to traction available. "



Dunno - but in my past life as a hotrodder, the relationship between quarter mile times and HP was pretty well known, and the ability to predict what HP was needed to lower quarter mile times by a 10th of a second could be pretty easily specified for a given vehicle. But it's been a few years, and I don't know the equation. In spite of that, I still suspect that LOSS of "a couple of 10ths" represents a higher percentage of actual HP or drivetrain loss than the original poster thinks...

 

[banshee]

And any hotrodder knows that the trap speed is a much better indication of power delivered to the wheels than ET. The same vehicle can cut more than a second of its 1/4 mile ET by going from street radials to drag slicks (more traction, same power to wheels), but trap speed only varies slightly.



But, hey, I'll take the 46% if the "experts" insist. Let's see... . that puts me at almost 1100 hp at the crank!!! Sweet!!!

 

[justinp20012500]

... Sure would be neat if we could stay on topic, and leave senseless personality analysis and attacks back in the schoolyard...

I agree.



Please gentlemen I can see that this thread is a prime candidate for a big padlock.



This discussion is very interesting and I would like to get back to the technicalities of why my HP # and ET/MPH do not match...



David,



Did you get around to downloading my dyno sheets???



Justin

 

[DavidTD]

I agree.



Please gentlemen I can see that this thread is a prime candidate for a big padlock.



This discussion is very interesting and I would like to get back to the technicalities of why my HP # and ET/MPH do not match...



David,



Did you get around to downloading my dyno sheets???



Justin

No Justin, I have not been into the office where I have high speed. Here in the sticks, I can't get it yet.



But one thing I did notice, is that on your dyno sheet waaaay back on page 1 it list your truck as 6600lbs. If I calculate your hp based on 6600 lbs, it comes out to 409, closer to the 384 you made. You'd have to ask the dyno operator how much that weight will change the output (if at all) as I don't know.



But I would be willing to bet with timing box, fueling box, DDIII's and hybrid turbo your truck was making more than 384hp, on my dyno anyway. Maybe some others will chime in with their opinion on what they have made with similar set-ups.

 

[jeff2]

This thead is very exciting, big fancy words, aerospace tech,

I don't know how we have managed all this time!

NASCAR seems to think a lot of dynojet's product.

I personally like the tool because it gives a real world test

of how a truck will respond on the street. If your truck won't

come to life on david's dyno you will have a black smoking

pig on the street. A load will hide that problem,and show more

power. I think in the diesel world, the dynojet is the only way to

go, because pulling these engines down with no air flow is hard

on parts. Thats my 9th grade drop out,grease monkey opinion!