Don't flame me about not being a physics professor or tell me to buy some other brand. But I went to a midwest gathering yesteday....A Big Thanks to JohnE. And I ran on a dyno for the first time. I got a decent hp reading but I thought the torque should be a little higher. The gathering was mainly Dodge guys and they make more torque with less hp...What's up with that??

I was thinking perhaps it was something to do with the Cummins being an in-line......more rotational efficiency.

Any ideas?? Other than buy bigger tunes and start stacking?

Wayne

There is a problem getting good torque readings with the Allison on a dyno.

Unless you can lock the truck in 4th, you cannot start your pull at a low enough RPM to allow the motor to build full boost where the torque peak hits at.

Unless you have a manual trans that is.

As far as modding goes, they sell torque in a blue bottle by the lb. ;)

So, do you think there was slippage??? I had the guy put it in tow/haul and he hit his button @ 2000 rpm to start the reading. I also thought the triple disk torque converter would have everything locked up tight. I was trying to figure out why the Cummins would put out 100+ ft/lbs more for a similar hp.

Wayne

It's not the slippage you must worry about, it's downshifting into 3rd.

You REALLY need to start a pull at 1500 in 4th, and you can't because it downshifts.

I see....Hmm...the pulls were done in 5th gearwith tow/haul activated...it never down shifted. He did run it up to 110 mph and it didn't shift. And he didn't have an OBD tool to lock it in 4th. The graph starts @ 2100 to 2200 rpm and he stopped at 3500 rpm. I think he pushed his dyno button while she was rolling @ 55-60 mph and he'd nail it....it never downshifted.

So how would I interpret the data?? It graphed 397 hp and 740 on the torque. Would my real numbers be a little higher since he was pulling with a taller gear???

Here is the math behind it all

HP= (torque*RPM)/5252

So if the dodge guys made the same torque at the same RPM they would also make the same HP as you. If that's not the case then something is wrong with the dyno you were on.

Would you like to see 1000 ft/lbs? If you make 1000 ft/lbs at 1000 rpm, that is only 190 HP. Torque is a component of horsepower, much like amps is a component of watts of electric power. If I tell you that I have a battery that puts out 10,000 volts, does that mean I can run a drill or power a small town with it? Without knowing how many amps it can do at 10,000 volts, you have no idea the power available, because volts x amps = watts. Ignition coils can produce 40,000 volts, but hardly any current, so not much power is being delivered. Torque doesn't tell you much without the rpm number to tell you the horsepower. However, the driveline only understands torque. If you make 1000 ft/lbs at 1000 rpm, you are only creating 190 hp, but you will need a great tranny, driveline, and rear end to hold it. Did you ever see the size of transmissions, driveshafts, and rear ends in bigger trucks? Even with relatively low hp outputs, they need this because the low gear transmissions multiply the torque, which requires the heavy driveline. So, if the Dodge guy makes more torque than you, but it is at a lower rpm, there is no more power there than with yours.

No, They made the torque at lower rpm's. I was just curious why this would be. The D-max is 700 cc's larger...so I would think our torque figures would be higher. There was a guy there with a heavily modified Cummins but with fuel delivery problems....his readings were 380 hp and 880 torque and if I recall correctly...it was between 2200 and 2300 rpm. My peak is @ 2600-2800 from looking at the graph. Just trying to figure out why my torque would be lower if we had similar hp numbers and fairly close displacement.

Wayne

A cummins has better torq at low rpms compared to the dmax. Doesnt matter if your locked in 4th with a tec-II, you will still not have the torq numbers that a cummins would have if you have the same hp as it.

Sandman

We make 1000 ft/lbs @ 2100 and 505 Hp @ 2850 with our Xtreme tune in a duramax so that's pretty close to what you say the dodge did. Our customers have reported a range of 950 - 1050 ft/lbs @ 2100 - 2200 so you will see some variation from engine to engine. Since the dyno operator did not have the proper tools to load your vehicle down it's kind of hard to say what you really make. If your happy with the way your vehicle performs your numbers are not all that bad.

I guess I was wondering what could explain the difference. I suspect it has to do with the Cummins being an in-line versus a "V". I guess perhaps some of the twist is lost because of the different angles transmitted to the crank.

Just curious.....and really enjoyed the opportunity to see the different mods for the Cummins.

Wayne

Typically in-line engines are higher torque and lower rpm than comparable size Vs, whether gas or diesel. I think it has more to do with the bore/stroke ratio. In-lines usually have a smaller bore and longer stroke whereas Vs are the opposite. That may be because in-line engines are tighter front to back in the engine compartment, so a smaller bore makes for a shorter engine. A V engine ends up being really wide with a long stroke, but length is rarely a problem even with a big bore because it is only slightly longer than a 4 cylinder. I know the Cummins is a tight fit as it is, so bore size is probably about as big as they could make it.

I might be off my rocker, but I think the answer lies in the fact that the Cummins is like a 4" bore x 5" stroke whereas ours is more like a 4" x 4".

Longer lever arm = mo torque?

Higher BMEP

Before anyone pronounces the Dodge motor as the torque champ, let see some dyno graphs. GM and Dodge are claiming about the same torque at the brochure.

To get the best picture of true hp and torque, u need to put it on a load cell dyno and pull the motor down.
What most are trying to tell u is the motor needs time to build boost, if he nails the throttle @ 2000 rpm it takes a little time before it has built max boost.
Our motors stock have max torque in 1600-1800 rpm and as other have said u really need to stand on the throttle just above idle so it's at max boost when u cross the peak torque rpm range.
But the alli will downshift.

Banks had trouble w/ their 6 gun and it making a lot of towing torque below 2000 rpm, the speed dynos couldn't capture it (so most thought they were lying), it took John Kennedy and his load cell to get the true pic of it's torque at <2000 rpm.

I might be off my rocker, but I think the answer lies in the fact that the Cummins is like a 4" bore x 5" stroke whereas ours is more like a 4" x 4".

Longer lever arm = mo torque? Exactly my understanding is longer stroke vs bore makes torque better. The Dmax is a square motor, not exception ratio for torque.

Thanks all...I'm beginning to "See the light". I was ignorant to the mathematic relationship between torque and rpm. Also the longer stroke sheds a lot of light. Looking at my graph and numbers....looks like the peak numbers are in the 2800-2900 rpm range. Which thw math formula would confirm. I just wish we could have locked it in fourth gear...even though it didn't downshift. So I'm wondering how bogus my numbers are?

With the 110 hp tuner...341 hp and 587 torque
with the tuner and LP 397 hp and 740 torque

Wayne

Wayne

... However, the driveline only understands torque. If you make 1000 ft/lbs at 1000 rpm, you are only creating 190 hp, but you will need a great tranny, driveline, and rear end to hold it. Did you ever see the size of transmissions, driveshafts, and rear ends in bigger trucks? Even with relatively low hp outputs, they need this because the low gear transmissions multiply the torque, which requires the heavy driveline. So, if the Dodge guy makes more torque than you, but it is at a lower rpm, there is no more power there than with yours.
:offtopic: Actually an automatic transmission also sees HP. The amount of power that the trans has to deliver to the rear wheels combined with the load that must be moved creates heat, and that heat has to be removed via the trans fluid and the tranny cooler. This is were the gvw rating for the transmission comes from. I think it is around 22,000 lbs for the allison 1000, give or take a bit. It is the rest of the drivetrain like the Driveshaft, differential, axles and wheels that only care about torque.