RodsterinFL

or at least one aspect of it.

There has been so much said about torque/power on this site and frankly I was bothered by it due to my lack of understanding. I was even approached by people who obviously had seen the specs on the RX8 and made issue of the 159 ft lbs. and compared it to the Z @ 274 and others. Well, last evening our nightly discussion centered around this issue and I learned something that many novices like myself may not know:

Harley motorcycles traditionally have been low rpm higher torque bikes while the Japanese bikes like Kawasaki are high RPM bikes.
Why does this matter? I was familiar with the wicked fast street bikes (Japanese) that take off and are gone from sight in a matter of seconds. Their RPMis high like the Kawasaki ZX6 are 13,500 RPM. The Harley moves off at a leisurely pace even at full throttle in comparison.

The RX 8 by many, is being compared to a regular piston engine car. The problem with that is that 9000 RPM is not the norm for a regular car engine. and that is what most people do not realize.
TheRX 8's 159 ft lbs. is GEARED to realize a higher return. Take two engines - one produces 100 ft lbs@5000 and the other 200@5000. If you GEAR the first to run 10,000rpm, you in effect equalize the ft lbs. at the wheel - simply said I am told.

This same idea is mentioned by an expert in the RX8 book by Yamaguchi. He explains how the actual torque of the RX is between the Porsche Boxster and Boxter S cars - Paul Frere p.35 4th paragraph.

I know many people here probably already know this but I didn't catch on until one gave me examples. Yes the other higher torque cars will pull away once the advantage of RPM/gearing is lost at higher speeds but most of us drive below 80mph "mostly" anyway and aren't racing. If so other things can be done- I am told. There is more to it than the simple spec numbers.

RXhusker

Gears are Torque Multipliers. Thanks to insightful posts from Buger and this excellent article Torque and HP it finally all made sense to me :D

rotarygod

Horsepower helps you win races. Torque helps you win tug of wars.

There was a rather ignorant redneck (non RX-7 owner) on the RX7club forum that read that article and said it was the dumbest comparison that he had ever read and that of course the F1 car would win. He couldn't say why though and obviously didn't read the whole thing.

RodsterinFL

exactly RXhusker ,multipliers.


I guess I am now baffled at the response of the people now.

Genom

The thing is Rodster, most people DONT know stuff like this. For most people out there they just look at the numbers and assume bigger is better in every way.

350 Formula

The thing that you have to remember is that most people are comparing piston engines that are geared about the same. So, my Formula with 325 ft/lbs will beat a 'standard' car with 250 or so. Also, most piston engines only make 5K to 6K RPMs so you can not gear them to equal the higher torque engine unless you have a LOT more gears or give up top end.

Now, with a 9K engine with 6 speeds...... you do the math.

yawpower

Hey there Rodsterin. I was happy to see your post, but I would like to make one clarification. I don't mean to be argumentative, but the torque-horsepower issue has been so skewed that I want to make sure everyone understands.

In response to:

The mechanical advantage of the gearing does not go away, because the low torque, high rpm motor will still be geared lower (Greater torque multiplication) even at high speed.

If the two engines that you describe are both geared for the same top speed, the torque multiplication will be double for the high rpm motor.

A guy named Adam Hammer emailed me in response to the article and pointed out a simplification that I should have included.

Force = HP * 375 / MPH

I included all the math with the gear ratios so that the explanation would be complete. This simple formula above says it all. Notice there is no mention of torque.

Paul Yaw
Yaw Power Products

Supercharger

Road&Track test data

_______________ 0-100mph __ Power __ Weight ___ Final Drive Ratio


Porsche Boxster S __ 14.4 s ___ 258 hp __ 3080 lb _____ 3.44:1

Porsche Boxster ____15.7 s ___ 228 hp __ 3000 lb _____ 3.56:1

Mazda RX-8 _______ 15.9 s ___ 238 hp __ 3000 lb _____ 4.44:1


All the above cars have manual transmission, NA engine and RWD.

canzoomer

True, to a point.
IF our RX-8 engines as delivered made the same torque or better to redline we would have a real edge at 7000rpm+ over other (mainly piston) engines that do not rev that high.

BUT: The cars have an ECU problem and torque and horsepower ( torque x revs) drops off badly when the 3rd set of intake runners open up.

The net effect is that while we have a 9500 redline, there is little point in going over 7300..

So, while in theory it is true ( and in Japan where the ECU allows the engine to make MORE power at 8500rpm) we do not benefit from this.

For an example of an engine that DOES benefit from this look at the Honda S2000..

It has a high redline too, and makes it's peak power way up there, because the engine does not have this ECU problem.

DisneyDestroyer

I liked this description:

Torque determines whether you can do something (drive through sand, fight wind resistance, etc). Horsepower determines how fast you can do it.

So as long as the torque can push you through the wind, higher HP will get you there faster.

RodsterinFL

no problem Yawpower. It doesn't hurt to be corrected. We state what we learn and others can help to refine it.

MWG

All of the examples, I see compare heavier cars or with a lighter car or motorcycles and the other thing I see Alot. Is a kawasaki is more aero friendly than a harley. It would only be fare if you commared a Kawasaki one with a harley engine and one with a kawasaki engine. Also F1 cars win because of rpm and weight. I mean They weigh very little. And because horsepower is a dirved from torque now that might be high rpm torque but it is torque. The rotary is a lot better at gettin all that power but you have to get air and fuel in to make that torque/horsepower at those higher rpms and then you can use the rpm to you avantage. With the help of gears to be faster.

deks

Aero isn't going to make a whole lot of difference below 60mph, and really below 100mph.

Buger posted this article a long time ago in this thread. It's my favorite explanation of the hp/torque difference. And it uses similar cars for comparison (LT1 vs. L98 or ZR1 Vette).