[dustylax]

does anyone out there make much WTQ, im looking for some dyno proven numbers of REAL wtq from a supercharged car, anything in the area of 210wtq but with less than 300whp ? Im just asking because im curious to see how other supercharger setups have been working for people because a lot of the dyno sheets i have seen are still below 200wtq even with upwards of 270whp. Wondering if its a tuning thing or if some of these superchargers just arent making the power in this short stroke motor.

 

[...m...]

...the math is fairly straightforward: HP=T*RPM/5252...that means 200 foot pounds of peak torque at 8000 RPM yields 305 horsepower, and the only way you'll find that much torque with lower peak horsepower is if your curve drops out at a lower RPM, not a good thing when our high-revving motors are capable of offering so much more...

...don't look at it as a powerful motor coming up short on torque, look at it as a modestly torquey motor coming out ahead on power...if anything, for the kind of extra bottom-end torque you're seeking, you'd rein in even more than 300 horsepower once the revs top out - as an example, ronin's elise is now pulling 320 foot-pounds with 460 peak horsepower...

 

[Bane]

Yep.. you just don't get torque from a 2ZZ engine anic:

Charlie's tuning is top-notch so I'm confident in saying he's been able to extract as much torque as (safely) possible out of the SC cars that have his tune.

 

[Bavarian Motorist]

Won't turbo cars generate more torque?



A 1.8l just doesn't produce torque I guess

 

[Westrock]

Won't turbo cars generate more torque?

Yes, but only because it overshoots on intial spool up, this is assuming a somewhat under sized turbo....a large turbo would have a more upward torque curve through out the RPM range.

 

[dustylax]

well using the math equation for one particular setup might work, but not on everything, like he mentioned a turbo, you could be making more tq than HP with certain sized turbo's or vice versa.

the rotrex setup we have i havent dyno'd yet but its breaking the tires loose from 6-8k and im curious to see how the tq numbers are going to compare vs the screw type that most people have been using.

here are some dyno sheets of other 2zz rotrex setups.

 

[turbophil]

The question is, can the rotrex deal with the RPMs of an 82-8500 redline... I thought that was the "issue" to get around with them. Size 'em right for the mid range and you have to clip the top end... size 'em right for the top end and you lose midrange (on the 2zz in particular)?

Just a question, not a statement based on any of my own experience... Would love to know the facts though:up:

Later,

Phil

 

[ChrisB]

well using the math equation for one particular setup might work, but not on everything,

The math works in all cases. I think what you are looking for is something with a lot of torque lower in the RPM range that falls off at higher RPMs (if the torque does not fall off, the HP will continue to rise above your stated limit). Diesel engines are on the extreme end of that continuum. Small turbos are typically like that. Old American V8 engines are like that. Small displacement, high-revving engines are not. I would not expect a Rotrex boosted 2ZZ would be either.

 

[dustylax]

but a Rotrex is like that, just like a turbo it is different than the screw type and different than all motor and another small displacement turbo or supercharged engine, they all act differently, there are many variables to account for that the equation cannot be accurate 100% of the time.

 

[Westrock]

but a Rotrex is like that, just like a turbo it is different than the screw type and different than all motor and another small displacement turbo or supercharged engine, they all act differently, there are many variables to account for that the equation cannot be accurate 100% of the time.

That dyno you posted above of a Rotrex actually shows the nature of a hybrid design like that. The main difference between a positive displacement supercharger and a turbo is that the supercharger pushes air through as the scrolls rotates, no matter the speed. Where as the compressor of a turbo has to "come to speed" before it can create a pressurized enviornment because the area around the blades isn't as air tight as a supercharger, so air can leak around it at lower speeds (and other situations).

So apply this to the Rotrex. The compressor needs to spin up to a certain speed before it can start pressurizing. But the only thing that will give the compressor more speed is more RPM. As a result you get a torque curve that climbs, somewhat similar to a turbo. You just dont have the complexity of a turbo nor the latent heat building up in the compressor since its not attached to a turbine. Those are the advantages of the Rotrex.


The horsepower equation will tell you the story of the motor everytime. If someone says an engine makes 300TQ and 300HP, anyone familiar with that equation will know instantly that the torque is falling off early, around 5000 RPM. There just isn't any way around that. It all makes sense when you realize the fundamental idea is that even though all these various ways of making power work differently they are all accomplishing the same thing.

 

[...m...]

...the trick is to realise that horsepower is simply a function of torque multiplied by RPM, nothing more, and that direct relationship exists because they both measure the same essential quality of how hard a motor pulls...no matter how your motor is set up, that relationship remains unchanged by virtue of its definition, and as david notes, the only time your peak torque will appear higher for a given peak horsepower is because you're actually getting less power than another motor which carries that same peak torque up through higher RPMs...

...if you look closely, you'll notice that every single motor, no matter how exotic, always makes numerically identical torque and horsepower at 5252 RPM - that's because 1 horsepower is defined as 1 foot-pound of torque rotating 5252 times per minute...

...essentially, torque measures the twisting force of a motor at any given instant, and power measures the potential mechanical advantage of that twisting force times the rotational speed at which it's being delivered...

 

[turbophil]

DX- It's just an efficiency game. Your answer lies in compressor maps. You'll find that in most cases, you'll see peak torque on or close to the island.

Best,

Phil

 

[dustylax]

haha i honestly dont know the math of the scenario of all NA motors making certain numbers at certain rpm's. Almost all of the cars i dyno here end up different because they have different setups and no same motors or setups make the same numbers of tq vs hp, regardless of where in the RPM range, that is not really what i was asking about.

i always see the screw type chargers making low tq for what kind of Hp they make and im just trying to make a simple comparison between torque for the 2 types of superchargers. i just wanted to see what kind of wtq people are making on screw type to compare to the rotrex, wondering if anyone else squeezing more out or if its just an inefficiency in the design of the screw type vs. the rotrex.

regardless of where in the RPM band the number happens i am just looking to see what peak numbers people have gotten from the screw type's, the location of or how wide the torque or hp is is a different issue all together about how they make power, the peak number is all i was looking for to get some numbers for comparison.

 

[Monsi]

supercharged engines have a fairly flat torque line(positive displacement not centrifugal)... so if you want 210 ft/lbs and 270 whp you need to lower the rev limiter

that being said I think you are putting entirely too much weight(no pun intended) on torque...

there is a very good reason why cars have transmissions in them
from a physics standpoint torque the amount of torque the engine is capable of producing is almost irrelevant when determining how fast you can accelerate your car provided you have the proper gearing and the engine isn't limited by its own rotational inertia

 

[...m...]

...yes, but think of the shift time and weight savings if we eliminated the transmission!..hey, it works for electric motors, at least...

 

[dustylax]

all variables being the same, speaking about the 2zz with the same 6 speed transmission and same ratio's, strictly comparing supercharger type to supercharger type the amount of torque of one unit will determine how fast the car can accelerate, torque is what moves your car, if you had 300whp in 2 of the same cars and one produces 190wtq and the other produces 220wtq which one would you prefer ?

 

[Tracktimeplz]

all variables being the same, speaking about the 2zz with the same 6 speed transmission and same ratio's, strictly comparing supercharger type to supercharger type the amount of torque of one unit will determine how fast the car can accelerate, torque is what moves your car, if you had 300whp in 2 of the same cars and one produces 190wtq and the other produces 220wtq which one would you prefer ?

Depends on the track

 

[...m...]

...okay, not being facetious this time - it depends entirely upon the torque curve and the driver's preferred throttle response...the 220 ft-lb car's will torque drop off precipitously above 7200 RPM at best, while the 190 ft-lb car may be good all the way up to 8300 RPM, but those two peak numbers alone (torque and power) don't tell us enough to determine the usable powerband nor throttle response...

...generally speaking, given the same peak torque, a wider and flatter curve offers a more usable powerband (and smoother throttle response) than one which sharply rises over a narrow area, but there are all sorts of curves which could make those same peak power/torque numbers you're proposing - we can only determine definitively is that the peak torque hits no higher than a certain RPM for a given power...

 

[Monsi]

I can make a lego motor put out 200lb/ft of torque... won't accelerate your lotus very well tho

just as m said... in that scenario the 220 car will run out of steam at the top of its rev range

 

[dustylax]

...okay, not being facetious this time - it depends entirely upon the torque curve and the driver's preferred throttle response...the 220 ft-lb car's will torque drop off precipitously above 7200 RPM at best, while the 190 ft-lb car may be good all the way up to 8300 RPM, but those two peak numbers alone (torque and power) don't tell us enough to determine the usable powerband nor throttle response...

...generally speaking, given the same peak torque, a wider and flatter curve offers a more usable powerband (and smoother throttle response) than one which sharply rises over a narrow area, but there are all sorts of curves which could make those same peak power/torque numbers you're proposing - we can only determine definitively is that the peak torque hits no higher than a certain RPM for a given power...

this is a rotrex 2zz, looks like a very usable power band and doesnt fall off up top, everyone seems to be speaking of different scenerio's they can think of, im talking about cars that have already been done, just looking for peak tq, cant seem to get anyone with torque over 200 to the wheels and less than 300whp.
again:

if the arguement was how wide the power band is on a lotus and how the driver would use it please remember most drivers keep it up near lift where the biggest power is so that is also where the most peak tq is on a rotrex setup and it also carries just as much torque across the low end of the power band as a screw type.