matching gearing to your power curve

[Kevin Shasteen]

.., A 200 Hp diesel the size of a small house won't accelerate nearly as quickly as a 2 liter producing the same power..,

 

That is exactly the point I was making. The HP footprint (HP Column on a Dyno) will indicate which engine is best suited for your needs. If you put both the 200 HP diesel and a 2.0L on a Dyno you would see that their HP curves differ greatly...thus you would then know which engine is best suited for your needs.

 

Obviously the HP footprint is not the only tool used in evaluating an engine: but, it is one of the most useful/valuable tools only equalled or superceded in by the TQ measurement.

 

As far as the output of an engine, both HP & TQ being a deivative & your belief that neither HP nor TQ are a rule of thumb as to how quickly power can be applied....exactly what would you use to evaluate an engine and its ability to apply power? Gearing certainly plays a huge part but the gearing is at the end of the power application and the gearing coupling is only as efficient as its power source that created the force in the first place.

 

An engine's force is measured in two ways...TQ & HP. The Vehicle's ability to utilize that force is where the gearing comes in to play.

 

TQ is the rule of thumb in "How Much" work the engine is capable of actually doing, while the HP rating is the rule of thumb in "How Quickly" the engine can accomplish that work. The work gets done in real time: real time to an engine is engine RPM not Vehicle Speed. Vehicle Speed is determined by the power source thru its gear couplings.

 

To say HP doesnt exist because it is a function of TQ is a misrepresentation of the facts; afterall, TQ is merely a function of Force...so does that mean that TQ doesnt really exist either? Certainly not-as both are merely measurements of Force in an engine and occur at different rpm's for different reasons based on the engine's ability to breath.

 

Now juggle all this: the power source, the power sources ability to work quickly or slowly, its RPM range where peak power both TQ & HP...thru its gear couplings & you should be able to accomplish your power needs = Happy Camper

 

Kevin,

(Yea,Still an Inliner)

[Pop N Wood]

Power, force, work, acceleration. All of these terms have very precise mathematical definitions, and each of these definitions has a very specific physical interpretation. There is nothing ambiguous about any of them.

 

Pick up an introductory physics text. Work is force times distance. Power is the rate at which work can be done. Torque is the rotational equivalent of force. The relationship between power and torque is just like the relationship between distance traveled and velocity. They are simply not a different measure of the same thing.

 

Kevin’s example of a diesel vs. the BBC dragster is exactly the end result I am trying to make. It is engine power that determines how fast a car can accelerate, not torque. The more power you can produce, the more torque you can create by the appropriate gearing. A Duramax Diesel truck can out accelerate many cars off the line only because it is geared to get into the power band more quickly. But if the car can get into it’s power band and stay there longer, then it will out accelerate the engine with more torque.

 

To dispel another common myth about towing capacity. What vehicle can pull a heavier tow load, a Duramax truck or a vehicle with a 450 HP SBC? Traction aside, I say if geared right the SBC will out pull the diesel truck. This is because the amount of torque you can put to the rear wheels is determined by the maximum HP the engine produces. Gear the SBC to run at it’s power peak and it will have more rear wheel torque than the lower HP diesel can produce. Go to a tractor pull if you don’t believe me. Jet turbine engines aren’t exactly know for low RPM torque, but if geared down from 12000 RPM to a few hundred RPM their HP advantage can be turned into massive pulling torque. As for streetablity, obviously who want to tow a horse trailer through the mountains with an engine reving at 5500 RPM. Get an engine that produces sufficient power at low RPM’s and get the pulling torque you need with less vibration.

 

I honestly think people would be better off if they completely ignored torque curves and just look at power curves. And I mean the whole curve of power vs. RPM, not just the peak value. Figure out what RPM’s your engine will be running at, then tune the engine (or gear the car) to maximize the power output over those revs.

[blackwidow]

Horsepower is about a dozen diffrent units depending on what your using it to measure. One day it will be fazed out by the watt. Untill then it will be diffrent things depending on what you are using it to measure.

 

As far as IC engines are concerned you cannot have HP without torque. Period

 

In any case one is more important than the other in certain circumstances. And should be looked at on a per application basis.

[Careless]

I'm going to add to Grumpy's links by posting this handy Gear Calc software that a friend and I used to find out what rear end and what transmission to use in his drag Iroc.

 

helped reduce his times by about a second or so, with him babying the car, so to speak.

 

http://racingdownloads.com/racing_software-22.html

[grumpyvette]

http://www.geocities.com/z_design_studio/transmission_300zx_tt.html

 

this is very handy, just remember to keep the engine in its ideal power band, you want to spend as much time as you can in any gear in the area centered between the torque and hp peaks, naturally youll need to rpm the engine above and below the peaks at times but try to concentrate the engines power band rpms with the sellected trans and rear gear choices

it makes no sence to build an engine that potentially produces 500 hp at 6700rpm, if your rear gear and trans keep the engine in the 2500rpm-5000rpm band most of the time or if your auto trans shifts at 5500rpm

[blackwidow]

I added this for manual shift points as it kind of goes along with what is being disscussed here.

 

http://forums.hybridz.org/showthread.php?t=140122

[grumpyvette]

thanks for posting that good info

[kiwi303]

The Z Design Studio links graph maker isn't working for me. it'll load all the boxes right, but not the graph.

 

Do you have any other links to graphical layout calculators? the other linkes are either bad/gone or text output. I'm trying to see what the Borg Warner M76 (0507) box from the Aussie XE Falcon will give me when matched between a 3.7 R200 diff and a Rover V8 with 7500 rev limit, driving tyres sized 225/60R15.

[grumpyvette]

http://www.geocities.com/z_design_studio/transmission_300zx_tt.html

 

http://purplesagetradingpost.com/sumner/bvillecar/bville-spreadsheet-index.html

 

these are the two most useful

[kiwi303]

I've tried this one's sister program for the S30 and S130

http://www.geocities.com/z_design_studio/transmission_300zx_tt.html

 

An it's worked in the past, however it's not workign this time round, I've got firefox 3 now rather than the 2.xx I did then, but I still have all the plugins, up to date JAVA, Flash etc so I can't see what might be stopping the graph from displaying.

 

Does that calculator in the link work for you?

 

 

I managed to get the excel bonneville one to graph manually, so Thanks for that Grumpy it looks like 5th gear at 2500 will put me at legal open road speed 4th gear (1:1) at 3000 and 3rd gear at 4000 will do the same, so a cam with power/torque between 2000 and 4000 revs will suit a cruiser that has a bit of fun as well

[grumpyvette]

from displaying.

 

Does that calculator in the link work for you?

 

http://www.geocities.com/z_design_studio/transmission_300zx_tt.html

 

works fine but it takes some time to fully load up, change the gear ratios and watch the red lines move possition then put your cursor in the box and you should see the rpms change as it moves around, its not giving set answers but rpm bands and speeds in gear

[kiwi303]

the problem with it from my perspective, is the graph won't load at all, where there used to be a graph with 4 or 5 lines spiking out from 0/0 to whatever top revs were, now theres a little 1mm x 1mm box blank box like you get when HTML coding says to put a border on something but the something is gone.

 

even when the page is fully loaded and network connections display is showing a flat line with no data being transfered... still nothing.

 

I suppose the page might not be compatible with firefox 3, I gave up and went searching through the HDD for Internet explorer, which I haven't used for nearly a year, that made it work.

 

Cheers Grumpy just something to submit to the firefox dev team