Are diesels slow ? at reving hurt times

[Moretorque]

I was watching diesels set up for 1/4 mile racing and it seemed like the times should be better. I am trying to understand how HP relates to the real world in application.

Just wondering if the long stroke was a real hard obstacle to over come for acceleration in reving and because such they really work better for pulling or maybe I am off somewhere.

[Highwayman]

I'd say that weighing 3 times what a car weighs is one of the bigger obstacles.

I've seen some people lighten the crank up a good bit, which would help, but it is like playing with fire..

[Rusty Green]

I always thought it was the torque that made up for the weight an less rpm

[rdix7991]

Sometimes looking at max HP can throw you off a bit when compared to quarter mile times.
Horsepower is directly related to RPM or angular velocity. If you differentiate that with respect to time you get acceleration. So that means the longer you can keep power applied to the drive, the better overall acceleration you will have.

[Highwayman]

I like playing with the HP calculator at the top of the page to get an idea of how different things change ET

[chevota84]

Originally Posted by Highwayman

I like playing with the HP calculator at the top of the page to get an idea of how different things change ET

X2. Put in a formula and start taking weight off, it's amazing how much difference 500 lbs makes.

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[mikmaze]

who's gonna shed 750 lbs, and swap an aluminum f150 body on a dodge chassis......

[Moretorque]

I was looking at a 2500 HP billet block diesel funny car on Utube and it seems it should run 5's no problem. It was running high 6's.

[chevota84]

Originally Posted by Moretorque

I was looking at a 2500 HP billet block diesel funny car on Utube and it seems it should run 5's no problem. It was running high 6's.

Who was it?

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[oldestof11]

Originally Posted by chevota84

Who was it?

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There's only 1 that I know of.

OP, he was having issues with applying the power to the track.

[Moretorque]

John Robinson.

[Bodacious]

Maybe I can get someone else to do the leg work here , how does the Schied dragster's times compare to the top alcohol dragster times??

[Scooter's Roofing]

after watching countless diesel truck speedometer videos on facebook and talking to custodial engineers at Cummins, International, AND Isuzu, I've come to realize that it's all about rev gain.

[mikmaze]

if its about rev gain, maybe we need to develop a type of trans that would allow you to start off at wot, top rpm and change speed to the rear as the tires moved faster......... biggest baddest toughest cvt ever.

[Moretorque]

Originally Posted by Scooter's Roofing

after watching countless diesel truck speedometer videos on facebook and talking to custodial engineers at Cummins, International, AND Isuzu, I've come to realize that it's all about rev gain.

I was reading where in drag racing they gave up on them to a degree in the pro ranks because how slow they developed power. They sure seem like they pull real good for moving a load.

That is the thing, lots of torque seems like you can drive a gear better for rev gain under a load but then you loose with a long stroke ?

I am trying to understand how to read a dyno and what it all means in real world app. Thanks for the help.

[turbom700]

Originally Posted by mikmaze

if its about rev gain, maybe we need to develop a type of trans that would allow you to start off at wot, top rpm and change speed to the rear as the tires moved faster......... biggest baddest toughest cvt ever.

They already have them and I belive John Robinson(sp) is running one. Same style clutch(transmission) they use in Funny cars and Top Fuel Drags. Bascially a set of clutch plates on arm that the higher the motor revs the more pressure it puts on the clutch. (way more complex then that)

Keep in mind that Diesel are running half the rpm there gas counter parts run. Having a narrow rpm range isnt helping anything.

[Moretorque]

Originally Posted by turbom700

They already have them and I belive John Robinson(sp) is running one. Same style clutch(transmission) they use in Funny cars and Top Fuel Drags. Bascially a set of clutch plates on arm that the higher the motor revs the more pressure it puts on the clutch. (way more complex then that)

Keep in mind that Diesel are running half the rpm there gas counter parts run. Having a narrow rpm range isnt helping anything.

That is where a one speed with a clutch comes in. They load the clutch to keep the engine in peak RPM torque range to accelerate so you are not reliant on RPM swing connected to shifting gears. That is how I ride my CR 500, put it in 4th and let the torque do the work by riding the clutch.

[turbom700]

But you still need RPM, Try riding your CR500 with half the RPM range and see how that works.

Take the CR500 to a drag strip and try launching is 4th gear then do it in 2nd and shift to 4th(if you could) your likely to have better ET then launching just in 4th.

Another thing to keep in mind is these style clutches are rebuild after each pass atleast in TF they are.

[Bodacious]

Originally Posted by mikmaze

if its about rev gain, maybe we need to develop a type of trans that would allow you to start off at wot, top rpm and change speed to the rear as the tires moved faster......... biggest baddest toughest cvt ever.

We run a triple 10" weighted clutch. The problem with this set-up is that you leave at close to 5000rpms just as the clutch weight overcomes the mechanical force to hold it. The engine is pretty much at its peak power when you let the clutch go which shocks the living crap out of the chassis/suspension. I've been doing my best to slip the clutch off the line, but it just ain't working out. ...can't cut a light for chit. If you weight the clutch to slip, it slips all the time cause you only have maybe another 500-800rpms before topping out (IE not enough to obtain lock up). If I could somehow get the thing to light around 3000rpms and leave, it would make for a much better set-up.

Ideally, a timed clutch sorta like the Top Fuel teams run would be the best (Or the bad a$$ CVT you mentioned) where the power could be delivered smoother and as you said, the engine could stay in the power range.

[Moretorque]

Yaa you are right but I wonder if John has enough torque like a TF car to where a tranny just slows you down.

The new 4 strokes that are replacing the 2 stroke 500's cannot do that even though they are the same HP.