Dyno nos.

[CRWilliams]

I just got back from the local chassis dyno and I have a couple of questions. They were using a Dynometer(brand name) dyno and he was running the pull in 5th gear. It was not like the ones I have seen on TV where they get into gear(usually the straight through gear, 4th in my truck) and then hammer it and get the numbers. They didn't hook any probes to my truck or anything. They just chained it down and ran it through the gears. Supposedly in 5th gear my truck is putting 187 horsepower to the rear wheels, this according to his figures is something like 427lb/ft of torque. These numbers sound pretty low to me. I have turned up the main power screw 2 turns, turned the diaphram about 1/4 turn and turned the star wheel down 3/4 turn. I also have a 14 cm housingmaking 25 lbs of boostwith the truck empty and a full 4 " exhaust system. Could anyone tell me if the dyno run was done wrong, should he have done it in 4th gear. The sheet shows a torque figure of 1272 lb/ft, he tried to explain that was a different figure from actual lb/ft of torque but he didn't make any sense. I don't have any faith in these guys anyway, the run was free and afterwards they tried to sell me a torque plate from Banks. I am going to try and include a copy of a couple of the runs, I hope it works.

 

[CRWilliams]

AARGH, pic too small. Sorry I'll try again.

 

[CRWilliams]

One more time, then I give up. Hope you don't need a magnifying glass to read this one.

 

[Copterdoc]

dyno feedback

Those are pretty good numbers, rear wheel and crankshaft horsepower and torque are two very different things. The 160hp and 400 ftlbs of torque that my cummins is rated at stock is the crank rating. rear wheel numbers are always a lot lower due to drag and friction. anywhere from where the crank bolts up to a clutch or torque converter you have power loss . Anywhere there is power being transfered from one component to another a very small amount of power is lost due to friction and drag. This includes your transmission(a manual transmission has slightly less loss than an auto), rearend and wheel bearings. It varies but i've read that your rear wheel numbers will be 15 to 25% lower than crank numbers depending on your power train. copterdoc

 

[Nordby]

I'll take a shot at this, though I am certainly no pro, I've had some trial by fire with my truck.



187 rear wheel horsepower is real good with a first gen truck. My stock number was 137 or so.



The torque number has to be divided by your rear-end ratio. But since he did not run in 4th, I don't thing that counts either. I'm sure there is some math involving your 5th gear ratio, and your rear end ratio, that when dividing that torque number from the dyno sheet by will give the right result. I'm guessing your 5th is . 77 (from memory, might be . 75 or . 72, not sure) and your diff is a 3. 54.



Again, guessing on what might be right for the torque calculation is (1299)/(. 77)(3. 54) = 476. 5. This is pretty respectible at the rear wheels too, but I would have expected over 500 lb/ft at the rear wheels given the horsepower you are throwing down. Either my guess at the equation is wrong, or I have your 5th gear ration as wrong (using . 72 you have 509 lb/ft).



Jon.

 

[Gary - K7GLD]

Seems like most of the newer, popular dynos are NOT set up to actually measure developed power under steady load, but instead measure the ACCELLERATION rate the engine is capable of, and THEN converts those numbers into HP and torque... That's fine for engines capable of rapid accelleration, like most V8s - but NOT for and engine like the Cummins long stroke inline 6! Our engines are far more like locomotives than race engines - not the fastest from a dead stop, but designed for heavy, steady pulling. Thus, a dyno like the Mustang, or any that operate by placing a LOAD on the engine and then measure the ability of the engine to maintain RPM at a specific load is a FAR more accurate method for a diesel than one designed only for measuring an engines ability for accelleration.

 

[paccool]

After the pump rebuild, mine was 180 RWHP, torque was a guess. Same thing they told you, torque is not real. The HP was with the timing way off - something they said they checked but didn't. Took the truck to Wentland diesel afterward and they set it up right. Made quite a difference in power. Now I need to get it back on a Dyno again. I am guessing at 195-200 HP. The auto takes away more than the manual but it still pulls pretty strong!

 

[drives mopars]

close but a hair low read what i got

i was at vegas may meet lots of tdr trucks on dynos



went to 2 dynos. my 93 pump taken off and adjed



open banks pipe, pw's 14 cm banks turbo k/n



remimber its a 4x4 dually with nv4500



went 210 hp with ac on , i guess about 215 to 220 hp



at rear tires or about 300 fly wheel hp



there was big harv w/ a 93 3/4 ton 2x4 getrag 5 spd

that went 209 hp. my dually 4x4 lost a lot more hp in drivetrain

then his,



did you try new injectors. ? i thing 476 to 500 tk is right on

the numbers for you. bruce pittsburg diesel says 330 fw hp is max hp for our pumps ,bill

 

[CRWilliams]

Somebody posted a thread a couple of weeks ago about replacing just the nozzles, the part no. he gave was 0433175040. I am thinking of trying this, I can't afford injectors just yet. I do need to have the pump timing set though. My biggest question was really should the run have been done in 4th or 5th?

 

[Gary - K7GLD]

WELL, most dynos give a printout that displays a plot of horsepower and torque vs engine rpm - without that info it's difficult with the material you have posted here to tell whether you actually REACHED maximum values, or at what point during the test! BUT, based on info provided in OTHER dyno runs, *I* would think that 4th, direct gear, would be most likely to give the most accurate numbers.



As far as *I* am concerned, compared to other dyno procedures and printouts, the one YOU got STINKS!

 

[Phil May]

Gear Ratio

What gears are you running 55 mph on the test @ 2500 rpm cant be 4:10s as my truck will only do 83 mph flat out with the 4:10. Why didnt you run it up on the govenor and see what it would do it might be interesting to see.

 

[CRWilliams]

I just noticed what RPM he had written on the sheet. Something is rotten in Denmark. He was in 5th gear on every dyno run and with my 3. 54's 55mph in 5th is something along maybe 1800 rpm. The way this dyno was apparently run you accelerated to a specific rpm and then the dyno would put a load on the engine. I didn't like it in the first place. A friend of mine has a brand new 2001 demo that the salesman who drove it bombed(believe it or not). He saw the dyno sheet on it, 300 hp at the rear wheels. He is going down there today or Monday and running his and seeing what he gets. BTW he thinks the run should have been made in 4th also, he thinks they were trying to lowball my power so they could sell me some Banks stuff . Needless to say I don't think I will go back to them, there is supposed to be a shop in Grand Junction with a Dynojet I suppose I will take it there. Or maybe someplace in Denver when I'm there next week. Anyone have any recommendations?

P. S. -Just did the math, if the rpm was actually 1800 the torque should be more like 588. Also on each dyno run the tires were turning black and I was sure they were spinning on at least a couple of the runs

 

[Cooker]

My friend has a 91, 4x4, 4. 10's, 5 speed, 16cm housing, and some pump work done. On a dyno at Michigan Caterpillar his truck put 251 hp on the ground. I don't know any other mods to his truck, but let me tell you it sure smoked alot.



Recently his pump died with about 160k on it and his new reman pump runs smoother and runs better through the RPM's, but doesn't have quite the hp as his previous pump even after a little tweaking.



-Ryan

 

[Dieselman359]

My 2 Cents

I say we all go to Scheid Diesel's upcomming rally (which I still need to register for, already got a hotel room though) And run our old powerhouses on their dyno that they set up. Last year I saw 170hp, and 460lb-ft @ the wheels in 5th@60mph. That was before the 'Ol Blue Specials.

Come on out, or I'll be the only First Gen on the dyno for the second year in a row