Diesel Power Magazine 1st gen buildup

[RSWORDS]

Its not uncommon for factory engine ratings to be under rated. If it has 200 at the wheels then it obviously has more then that at the motor. I have not been in any stock diesels other then my 89 I sold. My 93 is stock but It is not on the road yet. I have only driven it a little. I would have to say that my 89 had more then my 93 has. My current 89 has been turned up since I got it.

So basically they just gave an estimate on the hp rating, and never really dyno'd it right? The only way 160hp could really be 200rwhp, is if 160hp was an estimate.

Well maybe cummins ran out of say 160 pumps... And grabbed some 200 pumps (just using numbers) off the shelf to keep from falling behind with dodge.

[RSWORDS]

Its not uncommon for factory engine ratings to be under rated. If it has 200 at the wheels then it obviously has more then that at the motor. I have not been in any stock diesels other then my 89 I sold. My 93 is stock but It is not on the road yet. I have only driven it a little. I would have to say that my 89 had more then my 93 has. My current 89 has been turned up since I got it.

So basically they just gave an estimate on the hp rating, and never really dyno'd it right? The only way 160hp could really be 200rwhp, is if 160hp was an estimate.

Well maybe cummins ran out of say 160 pumps... And grabbed some 200 pumps (just using numbers) off the shelf to keep from falling behind with dodge.

[mprmn08]

most likely it was just bshp which is just a calculated number. they know at a givne rpm it does this hp and torque so they calculate what it will do at the rom they say it has 160 or whatever.

[GLHS]

Let's put it this way; IIRC the boost spec on non intercooled trucks was 23 and non intercooled was 15.

im guessing you mean the spec for non ic was 23, and ic was 15?.

DOH!! Um, yes.

[JQmile]

Here's an odd way of thinking about it. At that point Cummins was basically supplying engines to Dodge and Dodge was just droppin em in.....if you were Cummins better safe to build the engines at 180+hp than have a few get out that only have 140-150hp.

[jltait]

One thing to keep in mind is how the dyno session was ran. I Have read alot on this concerning chassis dyno numbers in magazines. When dynoing an automatic the only acceptable means to get an externally comparable (I say externally comparable in meaning able to compare to other dyno numbers of other truck on other dyno's or the same truck on a different dyno)hp/tq rating is in the direct 1:1 gear with the converter locked up (3rd gear for 727/a518). Otherwise you are reading torqe multiplication of the gear (if not in direct 3rd) or torque mulitiplication of the converter (which is fine if just making before/after comparisons of changes). So my understanding is the reality is a first gen with an auto 727 or a518 cannot be accurately dynoed for engine power unless their is an accepted calculation factor for the lack of a lock up converter. Supporting this is the fact that many see better/worse dyno numbers from converter swaps. A manual transmission in direct (4th gear for a g360) should give accurate externally comparable dyno readings as long as the clucth is working properly. Later second gen auto's can be mearsured accurately as well as long as the dyno run was made in 3rd with the converter locked to remove converter multiplication from being a factor. Also keep in mind that to be accurate a dyno session would have to be corrected to the same atmospheric conditions that cummins used to rate the engines by. I do not have personal experience with dynoing but this but this is information I have read and wanted to share, feel welcome to correct or question as needed!!

[Richie O]

When I had my truck done the rear wheel horse was 297. That was a actual rear wheel horse. The torque rating on the other hand was a guess by the computer on crank torque. I knew the torque rating sounded to high so I had a buddy call the shop and get an explanation. If they check rear wheel horsepower is that not acurate?

[jltait]

the formula for horsepower is :HP = rpm x T(torque)/
5252(constant). Based on the formula I would think that unless one has an accurate Rear Wheel torque number that their horsepower number would be skewed as well. Thats not to say that your RWHP and RWTQ numbers are not accurate they absolutely are but to say that absolutely ='s a specific crankshaft HP/TQ is where I think things get hairy. Remember gearing/converter change TQ and horsepower is a calculation based on TQ and RPM. Some very good converters can increase TQ nearly 2:1 (though not in this class of vehicle/transmission)
Think this might have gotten slightly off track..the question started did cummins rate the engine lower than actual output based on RWHP number guys are seeing In stock form. What I threw out there was be concious that gears and converters can manipulate the numbers, as well as atmospheric conditions. I'll bet the cummins ratings were good, but when guys run on a chassis dyno in stock form and produce numbers above the factory ratings it is probably due to other factors (gearing,converters, atmospheric, and alititude) . It would be interesting to see what one of these engines would do on and engine dyno with all the appropriate SAE requirements in place. ie stock intake/exhaust/ all accessories in place and operational and have it altitude/atmosphere corrected. Engine dynoeing has only recently become as much science as it was art. Remember the Ford Cobra law suit. Now I don't doubt that ford was getting the #'s they said they were, but in what condition was the engine prepped for the dyno. This is what led to the new SAE J3XXX dyno method which controls the variable or uses a correction factor for ones that cannot be controlled. When the manufacturers went to this method some engines with no change whatsoever went up in HP/TQ and others went down.

[seeker1056]

that gasser formula does not apply to diesels

[mprmn08]

actually it does apply to diesels they just have to put a magnet on the balancer and a pickup mounted somewhere to read the mag. flying around and that is used as you "spark" like they use on gassers to figure out the numbers. i've ran a few chassis dynos before and thats all we do to diesels and its just as accurate. its the dyno itself that scews the numbers whether its a load cell type dyno or not. the only way to get good numbers on a diesel is with a load dyno.

[Richie O]

I agree that it would be hard to get a flywheel hp and torque rating from the rear wheels. That is why we always refer to our power ratings as rear wheel hp. To me that means more then flywheel horsepower. I want to know whats hittin the ground. Thats all that really matters to me.

[Crossy's son]

I got the new march issue, its a good overview of everything they did to rust bucket so far. lots of other goodies in the magazine,

DEFINELY GET THE MARCH ISSUE, ITS AWESOME

that and i think you can see JQmile's face doing a burnout in the 89.

[seeker1056]

mmm - I dont think so

seems to me the torque hp/tq crossover constant for a diesel is 2980 or so rpm not 5250 rpm like a gasser.

its the "constant" that is wrong not the formula itself, if memory serves

[KTA]

HP and torque are both directly related to each other. Math is math and no matter what the physics of the universe remain the same be it a gas or diesel engine. hp and torque will always be equal at 5250 rpm, it is mathematically defined that way. What you are confused by is by looking at many dyno graphs. If the dyno graph is not set to show hp and torque using the same scale, then the point the lines cross at can be anywhere depending on the scalling, but the values would still be the same at 5250 rpm even though the lines may not cross there because of scaling.

[seeker1056]

Interesting KTA - as it was 2 years ago when i stated the 5250 gasser crossover and got told - not- on just about every diesel site on the net that I was frequenting at the time - and I was sure that physics hadnt changed - but you know - when it seems everyone else has the same amswer one must question thiers, or the info it was based on

I am glad to see I didnt lose my marbles or my hold on physics

thanx KTA