Speed-Talk is running on www.Speed-Talk.com

IMPORTANT: Update your bookmarks to https://www.speed-talk.com/forum/
(Right-click the URL and select "Bookmark this link")

How will you go faster?

General engine tech -- Drag Racing to Circle Track

Moderator: Team

David Redszus
Guru
Guru
Posts: 9213
Joined: Tue Nov 27, 2007 9:27 am
Location: Chicago
Contact:

Re: How will you go faster?

Post by David Redszus »

Tom68 wrote: Tue Nov 22, 2022 11:43 pm
David Redszus wrote: Tue Nov 22, 2022 11:32 pm
He isn’t wrong but don’t bother arguing as he hasnt figured out that maximising the force in F=MA is also achieved by maximising available power to the wheels at any instant .

To my esteemed fellow racers.

Given F=MA, and A=F/M, where is the horsepower factor?

Is it to be found within the Force parameter, or the Weight parameter? I think not. Both have units of lbs.
Then where?

Currently, we are examining the performance of racing snowmobiles with CVT transmissions.
Since the rpms and torque are held constant, so is the horsepower.
Yet, the sled will accelerate quite quickly at constant horsepower. How is this possible?
Only until it hits the wall, aerodynamic wall, gradient wall, CVT has no more gearing increase wall.
Tom
Would you please explain what you mean by aero wall, gradient wall, and gearing increase wall?
User avatar
Tom68
HotPass
HotPass
Posts: 675
Joined: Mon Feb 07, 2022 3:43 am
Location: VIC

Re: How will you go faster?

Post by Tom68 »

David Redszus wrote: Tue Nov 22, 2022 11:49 pm
Tom
Would you please explain what you mean by aero wall, gradient wall, and gearing increase wall?
You don't have unlimited power, it'll hit a wall or run out at some point, there's no infinity with the acceleration.
David Redszus
Guru
Guru
Posts: 9213
Joined: Tue Nov 27, 2007 9:27 am
Location: Chicago
Contact:

Re: How will you go faster?

Post by David Redszus »

Tom68 wrote: Wed Nov 23, 2022 12:01 am
David Redszus wrote: Tue Nov 22, 2022 11:49 pm
Tom
Would you please explain what you mean by aero wall, gradient wall, and gearing increase wall?
You don't have unlimited power, it'll hit a wall or run out at some point, there's no infinity with the acceleration.
Tom
Yes, of course you are right.

But my point was that the sled operates at constant rpm and horsepower yet accelerates very quickly.
How can that possible happen?
digger
HotPass
HotPass
Posts: 2474
Joined: Sun Jan 27, 2008 6:39 am
Location:

Re: How will you go faster?

Post by digger »

David Redszus wrote: Tue Nov 22, 2022 11:32 pm
He isn’t wrong but don’t bother arguing as he hasnt figured out that maximising the force in F=MA is also achieved by maximising available power to the wheels at any instant .

To my esteemed fellow racers.

Given F=MA, and A=F/M, where is the horsepower factor?

Is it to be found within the Force parameter, or the Weight parameter? I think not. Both have units of lbs.
Then where?

Currently, we are examining the performance of racing snowmobiles with CVT transmissions.
Since the rpms and torque are held constant, so is the horsepower.
Yet, the sled will accelerate quite quickly at constant horsepower. How is this possible?
Power = force x velocity

Force = power / velocity

So at any speed maximising the force at that speed comes from gearing it to running at maximum power.

Therefore with cvt maximum force across speed range comes from running at maximum power continuously and infinitely variably change gearing. This provides maximum torque to the wheels or linear force to sled tracks

If you use Stan’s torque curve what’s the maximum tractive effort that can be developed by the sled with cvt at 30mph and 60mph?
User avatar
frnkeore
Expert
Expert
Posts: 677
Joined: Wed Dec 25, 2019 3:06 am
Location: Oregon

Re: How will you go faster?

Post by frnkeore »

In my opinion, the CVT, in this case, acts in the same way as the torque curve would, only more linear.

In a multi geared car, each gear is fixed and the torque curve increases speed. In a CVT the torque is constant and the CVT increases speed/velocity. They do the same thing but, reverse the method.
User avatar
Tom68
HotPass
HotPass
Posts: 675
Joined: Mon Feb 07, 2022 3:43 am
Location: VIC

Re: How will you go faster?

Post by Tom68 »

David Redszus wrote: Wed Nov 23, 2022 12:17 am
Tom68 wrote: Wed Nov 23, 2022 12:01 am
David Redszus wrote: Tue Nov 22, 2022 11:49 pm
Tom
Would you please explain what you mean by aero wall, gradient wall, and gearing increase wall?
You don't have unlimited power, it'll hit a wall or run out at some point, there's no infinity with the acceleration.
Tom
Yes, of course you are right.

But my point was that the sled operates at constant rpm and horsepower yet accelerates very quickly.
How can that possible happen?
Gearing constantly changing of course.

But it also sort of can't, because to operate at a constant horsepower it needs a constant load in the real world.

A load cell dyno'd 800 hp engine in a small lightweight car with skinny tyres never produces 800hp in the car.
User avatar
Rick!
Pro
Pro
Posts: 369
Joined: Fri Jan 01, 2016 4:13 pm
Location:
Contact:

Re: How will you go faster?

Post by Rick! »

digger wrote: Tue Nov 22, 2022 4:12 pm
I know you don’t like thinking outside the box with equations but

Tractive effort force = wheel power / velocity

So 400 hp (298,000 watts) at a speed of 60 mph (28.7m/s) will generate a tractive effort force = 10,383N (22,800lb)
Last time I checked, 1lbf = 4.448N, so your calculation should be closer to 2334lbf.
And now you have others haphazardly throwing around lbf and lbm. :) I so much prefer SI units over the British Engineering system...
I also prefer to calculate atmospheric parameters from the inputs of temp, humidity and absolute pressure (barometer.)
Carry on, I'm entertained by the snowmobile example since as it was a passion and vocation of mine for a almost two decades. When you get to the part about the track driver/track interface and track hysteresis as knobs to turn to go faster, I might come out to play.
User avatar
Stan Weiss
Vendor
Posts: 4558
Joined: Tue Feb 20, 2007 1:31 pm
Location: Philadelphia, PA
Contact:

Re: How will you go faster?

Post by Stan Weiss »

This is the graph that David ask me to post.

Stan
David_R_Accel_Gs.gif
You do not have the required permissions to view the files attached to this post.
Stan Weiss/World Wide Enterprises
Offering Performance Software Since 1987
http://www.magneticlynx.com/carfor/carfor.htm
Proud Supporter of Indy 2022 A/S - A/SA Shootout
David Redszus
Guru
Guru
Posts: 9213
Joined: Tue Nov 27, 2007 9:27 am
Location: Chicago
Contact:

Re: How will you go faster?

Post by David Redszus »

So at any speed maximising the force at that speed comes from gearing it to running at maximum power.
Yes, but it also runs at constant torque as well as constant power.
Therefore with cvt maximum force across speed range comes from running at maximum power continuously and infinitely variably change gearing. This provides maximum torque to the wheels or linear force to sled tracks
Since engine power and torque are constant, the remaining variable is the clutch.
It changes clutch ratio which multiplies wheel torque, but the power does not change. The trick with a CVT is to tune the shape of the clutch shift curve for acceleration and/or top end.
A load cell dyno'd 800 hp engine in a small lightweight car with skinny tyres never produces 800hp in the car.
Excellent observation. No matter how much torque or horsepower is seen on a dyno, the actual horsepower delivered to the track will depend on grip and traction. Wheelspin indicates the upper limit has been reached; more power does no good whatsoever.
I also prefer to calculate atmospheric parameters from the inputs of temp, humidity and absolute pressure (barometer.)
Using those atmospheric parameters we can calculate absolute air density at any altitude or temperature; in fact the data logger can compute and display absolute air density.
We also predict the percent power loss or gain, the fuel enrichment change needed and air drag.
Carry on, I'm entertained by the snowmobile example since as it was a passion and vocation of mine for a almost two decades. When you get to the part about the track driver/track interface and track hysteresis as knobs to turn to go faster, I might come out to play.
Snowmobile racing now consists of drag, oval track, snocross and cross country racing using both two stroke and four stroke engines. The sleds are computer tuned, fuel injected, and some are turbocharged.

Drag sleds now produce almost 1000 horsepower which cannot be put down to the ice. We use on-board computer programs to control boost so as to maintain traction. Belt slippage and track to ground slippage is measured as is acceleration and speed for every foot of track. But there is always more to learn.
David Redszus
Guru
Guru
Posts: 9213
Joined: Tue Nov 27, 2007 9:27 am
Location: Chicago
Contact:

Re: How will you go faster?

Post by David Redszus »

David_R_Accel_Gs.gif

Many thanks to Stan for posting the graph.

The G force vs MPH graph was developed from the torque curve furnished by Stan and the vehicle specs posted earlier. It shows the acceleration and speed in each gear. It includes transmission losses, air drag, and rolling resistance.

What's wrong with this graph? How can performance be improved?
BobbyB
Pro
Pro
Posts: 380
Joined: Mon Apr 15, 2013 1:35 pm
Location:

Re: How will you go faster?

Post by BobbyB »

David Redszus wrote: Wed Nov 23, 2022 11:34 am David_R_Accel_Gs.gif

Many thanks to Stan for posting the graph.

The G force vs MPH graph was developed from the torque curve furnished by Stan and the vehicle specs posted earlier. It shows the acceleration and speed in each gear. It includes transmission losses, air drag, and rolling resistance.

What's wrong with this graph? How can performance be improved?
In the graph legend, what does " tire c 81.68" mean?
hoffman900
Guru
Guru
Posts: 2823
Joined: Sat Feb 23, 2013 5:42 pm
Location:

Re: How will you go faster?

Post by hoffman900 »

David Redszus wrote: Wed Nov 23, 2022 11:34 am David_R_Accel_Gs.gif

Many thanks to Stan for posting the graph.

The G force vs MPH graph was developed from the torque curve furnished by Stan and the vehicle specs posted earlier. It shows the acceleration and speed in each gear. It includes transmission losses, air drag, and rolling resistance.

What's wrong with this graph? How can performance be improved?
I think my focus would be to hold onto the peak torque because BMEP is very hard to improve, and focus on the torque’s fall off with ever increasing rom (which is subsequently going to raise horsepower)
-Bob
User avatar
Stan Weiss
Vendor
Posts: 4558
Joined: Tue Feb 20, 2007 1:31 pm
Location: Philadelphia, PA
Contact:

Re: How will you go faster?

Post by Stan Weiss »

BobbyB wrote: Wed Nov 23, 2022 11:51 am
David Redszus wrote: Wed Nov 23, 2022 11:34 am David_R_Accel_Gs.gif

Many thanks to Stan for posting the graph.

The G force vs MPH graph was developed from the torque curve furnished by Stan and the vehicle specs posted earlier. It shows the acceleration and speed in each gear. It includes transmission losses, air drag, and rolling resistance.

What's wrong with this graph? How can performance be improved?
In the graph legend, what does " tire c 81.68" mean?
Bobby,
I took that to mean the tire circumference which would be a 26" diameter.

Stan
Stan Weiss/World Wide Enterprises
Offering Performance Software Since 1987
http://www.magneticlynx.com/carfor/carfor.htm
Proud Supporter of Indy 2022 A/S - A/SA Shootout
Ken_Parkman
Expert
Expert
Posts: 637
Joined: Sun Jan 02, 2005 11:30 pm
Location: Ontario, Canada

Re: How will you go faster?

Post by Ken_Parkman »

David Redszus wrote: Tue Nov 22, 2022 11:46 pm
David your own simulation data proves these statements incorrect.
It does nothing of the sort. What do you feel is incorrect? Could you please provide a concrete example with real numbers?
How is it possible your better calculated performance is with the lower of your chosen input parameters if there is not something more to be learned?
There is a great deal more to be learned; we have just begun. The changes in calculated performance were never intended to optimize performance; only that as various parameters change, so does performance.

The shape of the torque curve and the gear sets used can produce substantial differences in performance.
A short first gear will produce a very quick 60ft time and high G force.
But, if the remaining gears are incorrect, the total 1/4 mile elapsed time will be slow.

Given a specific torque curve, it is important to find the right combination of rear end ratio, gear ratios, and tire diameter.
The concrete example was several pages back where a simple corrected input gave a 17% improvement in acceleration. Pretty good bang for the buck. The second concrete example is your own simulation where the use of the higher power portion of the torque curve (even with gear inputs are not realistic) gave a much better quarter mile time.

The question what is wrong with the chart (if you are serious) is it cannot improve real performance as we cannot optimize the driveline with that data. As you used the torque input there is not a crossover for different gears and we have no idea how optimize even the shift point. You cannot begin to optimize performance when you don't even know when to shift. Replot it using a power input against rpm and then you can optimize shift points and then have data to work with for driveline optimization.
BobbyB
Pro
Pro
Posts: 380
Joined: Mon Apr 15, 2013 1:35 pm
Location:

Re: How will you go faster?

Post by BobbyB »

Ken_Parkman wrote: Wed Nov 23, 2022 12:15 pm
David Redszus wrote: Tue Nov 22, 2022 11:46 pm
David your own simulation data proves these statements incorrect.
It does nothing of the sort. What do you feel is incorrect? Could you please provide a concrete example with real numbers?
How is it possible your better calculated performance is with the lower of your chosen input parameters if there is not something more to be learned?
There is a great deal more to be learned; we have just begun. The changes in calculated performance were never intended to optimize performance; only that as various parameters change, so does performance.

The shape of the torque curve and the gear sets used can produce substantial differences in performance.
A short first gear will produce a very quick 60ft time and high G force.
But, if the remaining gears are incorrect, the total 1/4 mile elapsed time will be slow.

Given a specific torque curve, it is important to find the right combination of rear end ratio, gear ratios, and tire diameter.
The concrete example was several pages back where a simple corrected input gave a 17% improvement in acceleration. Pretty good bang for the buck. The second concrete example is your own simulation where the use of the higher power portion of the torque curve (even with gear inputs are not realistic) gave a much better quarter mile time.

The question what is wrong with the chart (if you are serious) is it cannot improve real performance as we cannot optimize the driveline with that data. As you used the torque input there is not a crossover for different gears and we have no idea how optimize even the shift point. You cannot begin to optimize performance when you don't even know when to shift. Replot it using a power input against rpm and then you can optimize shift points and then have data to work with for driveline optimization.
it looks to me like you should shift at 55 mph & 92mph to maximize acceleration ... Am I missing something?
Post Reply