HP rating on Diesel engines

[The Cosworth]

Hey guys, I was talking with a buddy who has a diesel truck about HP ratings on them.

HP=(Torquexrpm)/5252

therefore that means that you are always experiencing torque until you get past 5252 rpm.

Most (if not all) diesels redline before 5252, so does that mean you are never using your HP? and if that is the case, would that mean if you could spin a diesel engine faster you could get some STUPID hp numbers?

TYIA

[Zero102]

This is a VERY complicated question.
Yes, HP is torque*rpm/5252, and when dyno'ing diesels this reads to some very low HP numbers for some very strong cars. Yes this is because most diesels red-line well before 5252RPM. This is caused for a few reasons, primarily the mass of the rotating assembly inside of a diesel engine, it is very high, so there is a lot of stress on the internals at just 4000RPM, and since the stress is proportional to the rotational rate squared, the difference between 4000rpm and 5252RPM is bigger than it sounds.

Also, the flame propagation speed in diesel is lower than in gasoline, so is the rate of expansion of the produced gases. This works against high-revving diesel engines. The turbo's on most passenger car diesels are sized to provide full boost by 1200-1500RPM (they are variable geometry) and hold that boost to 4000RPM, after that they are outside of their efficiency area and the boost drops off as well as the heat increases. You couldn't just spin these engines faster without other serious modifications. We're not talking about truck engines here, some of those have a redline as low as 1500 or 1750RPM.

I want to pick on the 'experiencing torque' statement for a minute, you are always 'experiencing torque', torque is what moves you, it is always what you feel when you step on the accelerator. HP gives you meaningful performance data for other calculations, but you never 'feel' horsepower.

While it is very difficult to get a diesel engine to wind up past say, 5k RPM and still produce meaningful torque there are several companies who have been successful. I recall seeing some smaller displacement (1-3L) diesel engines with redlines as high as 10,000RPM I just can't place where at the moment.


If you are serious about diesel tuning do some more research on how diesel engines work, there is no way I can possibly explain all of it on here :)

[Canmorite]

Originally posted by Zero102
While it is very difficult to get a diesel engine to wind up past say, 5k RPM and still produce meaningful torque there are several companies who have been successful. I recall seeing some smaller displacement (1-3L) diesel engines with redlines as high as 10,000RPM I just can't place where at the moment.


Audi, for one.

http://www.fast-autos.net/vehicles/Audi/2006/R10/

[benyl]

Usable power band is between 3K and 5K for the R10.

[syeve]

Originally posted by Zero102
This is a VERY complicated question.
Yes, HP is torque*rpm/5252, and when dyno'ing diesels this reads to some very low HP numbers for some very strong cars. Yes this is because most diesels red-line well before 5252RPM. This is caused for a few reasons, primarily the mass of the rotating assembly inside of a diesel engine, it is very high, so there is a lot of stress on the internals at just 4000RPM, and since the stress is proportional to the rotational rate squared, the difference between 4000rpm and 5252RPM is bigger than it sounds.

Also, the flame propagation speed in diesel is lower than in gasoline, so is the rate of expansion of the produced gases. This works against high-revving diesel engines. The turbo's on most passenger car diesels are sized to provide full boost by 1200-1500RPM (they are variable geometry) and hold that boost to 4000RPM, after that they are outside of their efficiency area and the boost drops off as well as the heat increases. You couldn't just spin these engines faster without other serious modifications. We're not talking about truck engines here, some of those have a redline as low as 1500 or 1750RPM.

I want to pick on the 'experiencing torque' statement for a minute, you are always 'experiencing torque', torque is what moves you, it is always what you feel when you step on the accelerator. HP gives you meaningful performance data for other calculations, but you never 'feel' horsepower.

While it is very difficult to get a diesel engine to wind up past say, 5k RPM and still produce meaningful torque there are several companies who have been successful. I recall seeing some smaller displacement (1-3L) diesel engines with redlines as high as 10,000RPM I just can't place where at the moment.


If you are serious about diesel tuning do some more research on how diesel engines work, there is no way I can possibly explain all of it on here :)

You are smart.

[forkdork]

http://www.dieselinside.com/1.6td/tach.jpg

6200rpm in a 1.6TD (VW). This is probably the easiest revving diesel engine we got in Canada (obviously this isn't stock), but I highly doubt you could get the new 1.9L TDI (ALH/BEW) or even the 1.9TD AAZ engines to rev like this because of the mass of the internals (as explained above).

[The Cosworth]

haha no i am not super into tuning them I was just wondering because technically you are always on the torque curve then, the HP curve will never pass it for a standard (see f350, duramax) engine.


Thanks zero102

[Canmorite]

Originally posted by benyl
Usable power band is between 3K and 5K for the R10.

Ah, didn't know that. Where did you find that info?

[Zero102]

I checked wikipedia on the R10 before I posted, IIRC they say something about a 3k-5k powerband but I could have sworn the engine had a redline of like 10k, maybe I'm crazy? They don't post the redline on wikipedia.

The 1.6IDI or TD is happier to rev than the 1.9TDI, but IIRC the stock rev limiter on the 1.9TDI is 5200RPM. Mine's an autotragic (sorry, the wife's fault!!) so it always shifts at 4900RPM regardless and I don't see the point revving it up in neutral just to find out.

IMO diesel's are far more drivable than a comparably sized gas engine. Sort of like electric cars, they have gobs and gobs of torque for passing and pulling power, they just don't do so well in straight line sprints.

[Ashers]

My 1.9 PD TDI (BEW) falls on its face at 4000 rpm... before that its a absolute scream!

[benyl]

Originally posted by Canmorite


Ah, didn't know that. Where did you find that info?

on wiki... AND the article you posted. LOL

[Unknown303]

I was the Diesel person in the original discussion.

I just figured that the original calculation didn't hold true for Diesels.

[Unknown303]

Oh thats not my truck but it is a Durmax.

1036 HP Torque 1500 (Max torque for Dyno).

Or this image.
http://photoshare.shaw.ca/image/f/7/a/78597/813-0.jpg?rev=0

[The Cosworth]

Originally posted by Unknown303
Oh thats not my truck but it is a Durmax.

1036 HP Torque 1500 (Max torque for Dyno).

Or this image.
http://photoshare.shaw.ca/image/f/7/a/78597/813-0.jpg?rev=0

all you gotta do is throw an intake on and you'll be there wouldnt you?

haha

the efficiency of the turbo really falls off in this one hey?

[Unknown303]

Jesus i wish i just had an intake to go to get there.

All the Diesel dyno's (Maybe not the R10) drop of in that exact fashion. Luckily with gearing you never have to see that region of the curve.