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Discussion Starter #1
I saw this on another forum I want to know how you can "backwards dyno" or is that just on an engine dyno? He also proclaims to be putting 850 to the ground later in the post...... LOL LOL



And I do understand how they make 1400 hp, by pulling the motor backwards on the dyno, this is the way a sled puller runs so this is how they dyno them, the same motor on a accelerated dyno pull . meaning the way drag racer pull them would only make in the neighborhood of a 1000 hp , because not only are you giving up using stored energy in the motor , but a over rich, pig fat motor is lazy when you try to make it rev gain. So put you motor in a drag racing type vehicle , and watch the difference .

I wonder if you can guess who said that?
 

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Discussion Starter #3
You dont wanna know............... Lets just say he is relatively new to the diesel world...
 

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OMG!!! what site is that from?


luke
 

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Discussion Starter #6
No B, none of the sort. I was hoping that DavidTD may have some sort of Idea what this fella is talking about. The only way I could see a "backwards dyno" is if you ramp a truck up to say 5k on a loading dyno, then romp on it ? I dunno...makls no sense to me...
 

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An interesting theory.....wonder how true it is. Hopefully this spaws some interesting disscussion and not a bash fest.

Slightly OT but who has the fastest time down the 1/4 mile in a diesel powered vehicle? Not interested in a debate about who is lighter or who has more $$$ in it or who will be :blah: Just a simple who is the fastest?

I am truely interested in a disscusion on this, seems alot of good and interesting info could come out if people keep an open mind regardless who is right or wrong. Sounds like an interesting theory but does it hold water??? I duno.

My though right or wrong. Pulling a motor down that hard would definatly load the piss outa a turbo regardless how laggy it is I would think. If you make good power letting it rev free then in a lite vehicle I would say thats a plus to moving down the 1320. yes no???
 

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ok.....maybe my question about who is the fastest is slightly stiring the pot ;)
 

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Discussion Starter #9
I could be wrong Ratlover, but to my knowledge Scott Bentz has the fastest pass in a Rail. I dont think it is stirring the pot too much now, but if some more "vocal" members of the diesel internet community show up it could get interesting. I would love to answer the question, but I dont know enough about how you could dyno both bcakwards and forewards...I figure if a motor is under full load at a gfiven RPM it makes the same power no matter if it is coming or going......but i'm no physics guy...
 

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I think I have a clue here, just a clue. Something an old drag racer from home told me, "Torque motors like to work". The best way I can explain it is by example. Good friend of his was running the same motor Milton was, a 355 small block that was wrap happy as all get out. Well, Miltons' buddy built a 383 stroker for his drag car and put it in. With the same tranny and rear end gears used on the 355 motor his times did not change more than a tenth. He changed the rear end gears from 4.10's to 3.73's. With everything else being equal he picked up another tenth. The only thing he did different was make the motor "load" a bit more, which apparently made the motor happier and let it show it's stuff. Henceforth the phrase "Torque motors like to work".

Clear as mud?
 

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Allright, after thinking about the statement in question a bit, I think I know what the feller is trying to say....(This is what you're getting at too, BG)
I'm assuming what the guy is talking about is putting a higher load on the engine via the dyno (higher resistance in other words). On an engine dyno, I could see this working, but I would think on a wheel dyno, if you put more resistance on the drum, would that not promote wheel slip as well? :confused:
When it comes to running tractors on a pto dyno, you can get more power out of a high-torque motor by pulling them down below 540 rpm (Pto speed). This only works for something that likes low rpm though, as a high-revving motor (such as a 2 cycle detroit) has nothing down in the basement..You pull that below its sweet spot, it falls flat on its face.
 

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He was talking about an engine dyno. Here they can spin the motor to a selected rpm (say 5000) then apply load and pull down the motor (say to 3000) and the machine will provide HP/TQ. What Comp is saying is that this does not demonstrate the engines ability to rev. He is correct, but he is incorrect in assuming that same builder cannot make one with the ability to rev.

FTR, this is why I prefer to run on my Dyno Jet. It simulates the engines being able to rev down the track. Darren made 686 at TS, then after his run, I calculated it out to 682. Being able to tune at the shop, then calculate the estimated trap speed before ever loading on the trailer is what we are after.

Bentz dragster fastest I know of. 7.98 @ 167.
Comp Pro Truck - [email protected]
Jeff Garmon on factory frame @ 9.97 @ 136
Factory body - Bill Fletcher @ 10.13 @ 135

Those are the fastest I know of, but who knows what else is out there.
 

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Discussion Starter #13
That clears things up a bit david..I did not realize he was talking about an engine Dyno..
 

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Thanks David. I'm wrong again.

I know you like your dynojet becasue if you cant get turbos to light on it then you aint going to get em to light well on the street/track ect. right? Could not a good operator(key word here) with a load cell be a bit more exacting to how the motor will be loaded if(another key word) the right info was pumped into it? Dyno jet seems(no offense here) idiot proof while load cells allow for the garbage in garbage out.

I didnt see were he said someone couldnt build a motor to do X.....or was that in the rest of the post he made?
 

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Discussion Starter #15
He pretty much said what he always says if you read his posts.
 

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ratlover said:
Thanks David. I'm wrong again.

I know you like your dynojet becasue if you cant get turbos to light on it then you aint going to get em to light well on the street/track ect. right? Could not a good operator(key word here) with a load cell be a bit more exacting to how the motor will be loaded if(another key word) the right info was pumped into it? Dyno jet seems(no offense here) idiot proof while load cells allow for the garbage in garbage out.

I didnt see were he said someone couldnt build a motor to do X.....or was that in the rest of the post he made?
Huh, so you think if you can't get a turbo to light on a dynojet, that means they won't light well on the street? The reason people like Dynojets over Superflows or Mustangs is because they produced inflated numbers lol.
 

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ratlover said:
Thanks David. I'm wrong again.

I know you like your dynojet becasue if you cant get turbos to light on it then you aint going to get em to light well on the street/track ect. right? Could not a good operator(key word here) with a load cell be a bit more exacting to how the motor will be loaded if(another key word) the right info was pumped into it? Dyno jet seems(no offense here) idiot proof while load cells allow for the garbage in garbage out.

I didnt see were he said someone couldnt build a motor to do X.....or was that in the rest of the post he made?
I wouldn't say you were wrong ratlover. And you are absolutely correct with the loading units. I like them too. There are cases when turbo's will not reach potential on a dyno jet, but in most cases I think they could be tuned to be better.
 

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duke1n said:
Huh, so you think if you can't get a turbo to light on a dynojet, that means they won't light well on the street? The reason people like Dynojets over Superflows or Mustangs is because they produced inflated numbers lol.
If you can't light the turbo on a DJ248 it will be laggy on the street. Yes. It will light on the street though but will be slow responding.

If Dyno Jets provide inflated numbers, why is it that every test I have conducted between the two styles, when the loading unit is operated correctly it is within a few HP of my dyno jet?

If the numbers are inflated, how do you explain 686hp making a 10 second pass?
 

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I ment wrong in fastest diesel vehicle
 
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