Dodge Viper GTS on the rollers

[AW111]

Max_Torque said:

These days we do "radiological" durability analysis of wearing parts!

Special components (bearing shells, liners, rings, crank, lifters etc) are doped with different radioactive isotopes, the engine built and run. At periods during the durab test the oil is sampled for these isotopes and the relative concentrations give us wear values for each part without diss-assembling the engine ;-)

That is brilliant. Hats off to whoever first thought of that!

My knowledge is way out of date, but from memory this was a QA facility, so tests were run on an engine randomly pulled from the end of the production line, ie testing the build quality, not the design.

Edited by AW111 on Monday 1st June 22:20

[anonymous-user]

It came from the aero industry, in particular it's used in the gearboxes for turboprops and Helicopters, where you REALLY need to know if anything is wearing out without having to take it all apart!

[Stan Weiss]

Pumaracing said:

Here's your power curve Stan. Below 2500 rpm something wasn't panning out so I've just taken it from there up. These are wheel figures. You can work out the torque and graph it against your own calculations.

RPM....BHP
2500...108
3000...154
3500...195
4000...210
4500...227
5000...219
5500...207
6000...195

I did a fair amount of smoothing of the final curve but it all matched the timed figures fairly nicely. Peak flywheel bhp is about 270. Now you can tell me what that motor was supposed to have.

Pumaracing said:

Stan, the first thing I did with your data was interpolate it into 5mph increments as follows. Using accurate data for your tyre size the mph per 1000 rpm in that gear is 11.389.

MPH..RPM...TIME...INCREMENT
30...2634..114.36
35...3073..114.95..0.59
40...3512..115.46..0.51
45...3951..115.99..0.53
50...4390..116.52..0.53
55...4829..117.13..0.61
60...5268..117.83..0.70
65...5707..118.63..0.80

Total time 4.27s

This achieves some pre-smoothing by summing several data points and eliminates most of the glitches. The time increments are actually rather nice - hitting a minimum around peak torque and then increasing again. Finding a power curve match to these increments was not difficult and very little tweaking was required to get the final nice smooth curve I posted.

I did a bit of googling on that engine which I'm not familiar with. The consensus from several web sites and youtube videos is they show about 230 bhp at the wheels at about 4800 rpm. I'll call my calculated 227 bhp just about on the money. You can clearly see from the time increments that power is dropping fast after 5000 rpm and my own power curve shows that too.

Your own power curve looks pretty close up to about 4500 and then just goes a bit too high for a bit too long after that. Not sure why.

Rotational inertia was not actually a big factor on a low revving engine like that. With wheel mass inertia and engine inertia factored in I calculated a total effective vehicle mass of 3942 lbs in that gear.

Dave,
Thanks. I smooth the output data. When I get time I will look to see what I can do to smooth the input. This is what I get using your data. This is the raw output no smoothing. The first set has aero drag abd rolling resistance added in and the second is does not.


..........................Rear......Aero....Rolling...........Rear.W..Accele...Time....Rate
..RPM......MPH...Velocity..Wheel....dynamic..Resist...Elapsed...Horse..ration..Differ....RPM
..................ft/sec..Torque...Drag.-.HP...HP......Time.....Power..in.G's..ential....Sec

.2634.0..30.938...45.375....0.00.....1.560...4.579.....0000......0.00..0.0000..0.0000....0.0
.3073.0..36.094...52.938..252.11.....2.478...5.342.....5990....147.51....3924..0.5990..732.9
.3512.0..41.250...60.501..300.11.....3.698...6.105...1.1000....200.68....4692..0.5010..876.2
.3951.0..46.407...68.063..284.44.....5.266...6.868...1.6330....213.98....4410..0.5330..823.6
.4390.0..51.563...75.626..287.60.....7.223...7.631...2.1630....240.40....4435..0.5300..828.3
.4829.0..56.719...83.188..255.19.....9.614...8.394...2.7700....234.63....3872..0.6070..723.2
.5268.0..61.876...90.751..225.87....12.482...9.158...3.4700....226.56....3358..0.7000..627.1
.5707.0..67.032...98.313..202.50....15.870...9.921...4.2700....220.04....2938..0.8000..548.8

.Averages.................258.26...............................211.97..........0.6100..737.2


...........................Rear......Aero....Rolling...........Rear.W..Accele...Time....Rate
..RPM......MPH...Velocity..Wheel....dynamic..Resist...Elapsed...Horse..ration..Differ....RPM
..................ft/sec..Torque...Drag.-.HP...HP......Time.....Power..in.G's..ential....Sec

.2634.0..30.938...45.375....0.00.......000.....000.....0000......0.00..0.0000..0.0000....0.0
.3073.0..36.094...52.938..238.75.......000.....000.....5990....139.69....3924..0.5990..732.9
.3512.0..41.250...60.501..285.45.......000.....000...1.1000....190.88....4692..0.5010..876.2
.3951.0..46.407...68.063..268.31.......000.....000...1.6330....201.85....4410..0.5330..823.6
.4390.0..51.563...75.626..269.83.......000.....000...2.1630....225.54....4435..0.5300..828.3
.4829.0..56.719...83.188..235.60.......000.....000...2.7700....216.63....3872..0.6070..723.2
.5268.0..61.876...90.751..204.30.......000.....000...3.4700....204.92....3358..0.7000..627.1
.5707.0..67.032...98.313..178.76.......000.....000...4.2700....194.25....2938..0.8000..548.8

.Averages.................240.14...............................196.25..........0.6100..737.2


Stan

[Pumaracing]

Hey Stan. Don't go trying to make it easy for us to read your data tables ok. I wouldn't want you to put yourself out typing some comprehensible column titles in. You just let us try and parse out way through the morass of gibberish by ourselves ok.

Anyhoo. Your power curves look a lot more sensible now. Just a few things to correct. The rolling circumference of radial tyres isn't the simple calculation of width x aspect ratio plus rim diameter you are using. I already gave you the correct mph per 1000 rpm - 11.389. If you look at manufacturer's tyre data the average rolling circumference of new tyres is 97% of the simple calculation and my own program accounts for that. This is increasing your mph numbers by 3% and power requirement by 6%. 5707 rpm is exactly 65 mph. This alone is adding 15 or so bhp to your numbers.

If I interpret your columns correctly and check the calculations it seems you're using a coefficient of rolling resistance of 0.015. This is a bit high for road tyres. I use 0.013. It's not greatly significant though. The aero drag calculations look ok.

Run the calcs again and you should be closer to 227 bhp.

[Stan Weiss]

Dave,
That data was cut and pasted from the output of my software. Now you know why my users say the software is not user friendly. As for the tire size I just used what I already had in my parameter file. If I still had the vehicle I could of measured the circumference of the tire (which is the only really accurate way) and than calculated and used that tire diameter and radius. Yes my default coefficient of rolling resistance is 0.015, but that is a user entered parameter and easily changed based on what surface the simulation is for.

Stan

[Pumaracing]

Could "have" measured FFS. Not could "of" measured. Ohhhh you colonials bdising our wonderful language.

Measuring the free circumference of a tyre doesn't give you you the actual rolling circumference. Tyre distortion (mass of the vehicle compressing the tyre into a D shape) and tyre slip / tread shuffle reduce that figure to the data available from tyre manufacturer brochures. I studied much of this before writing my own simulation program. Getting the speeds right is key to getting the power right.

[carl b]

Last time out the viper did 200 mph in the mile

I think it can do more now

[Stan Weiss]

carl b said:

Last time out the viper did 200 mph in the mile

I think it can do more now

Carl,
Is this a standing start on flying mile?

With all of the twists and turns that this thread has taken why not one more? If you post up specs like trans gear ratios, rear end gear ratio, tires size, weight of vehicle with you and a HP and or torque curve, Dave and or I might be able to do a simulation run.

Stan

[Pumaracing]

Well I can - and Stan might get fairly close.

Bazinga.

[Boosted LS1]

Well, don't they say "A miss is as good as a mile" :-)

[Stan Weiss]

Pumaracing said:

Well I can - and Stan might get fairly close.

Bazinga.

Dave,
I sure hope Carl posts some real information about the car. So you can do a simulation. I took a WAG about some specs and I know my HP / Torque is low and have it running 200 MPH @ 1 KM and 222 MPH at 1 Mile

Stan

[chuntington101]

I just wish Carl would post some pics of the setup in car or some videos of the car in action.

[carl b]

It was a standing mile at Woodbridge

Car pulled repeated 196 mph but couldn't quite hit 200 so I took the wipers off and the mirrors and hit 200 mph in a standing start mile

With the recent mods I recon it could do better

[carl b]

What do you need to know about the setup

[Stan Weiss]

Carl,
This what I am using, please let me know if you see anything that is
wrong.

Car Weight = 3500.0 <<<--- Vehicle plus you
Rear Gear Ratio = 4.11
T Gear1 = 2.664
T Gear2 = 1.783
T Gear3 = 1.302
T Gear4 = 1.0
T Gear5 = 0.741
T Gear6 = 0.502
Coefficient of Drag = 0.36
Frontal Area = 20.0
Tire Diameter = 28.0
Tire Rolling Radius = 14.0

I do not know what other information is on your time slip but this is
what I get for the 196 MPH and 200 MPH runs.

60 Foot ET = 1.5552
330 Foot ET = 4.1262
1/8 Mile ET = 6.3041
1/8 Mile MPH = 113.3826
1000 Foot ET = 8.1971
1/4 Mile ET = 9.7985
1/4 Mile MPH = 141.5976
Try Using Rear Gear Ratio = 6.162
1/2 Mile ET = 15.504
1/2 Mile MPH = 169.56
KiloMeter ET = 18.020
KiloMeter MPH = 177.65
Mile ET = 25.287
Mile MPH = 196.27

==============

Make change to CD and Frontal Area

60 Foot ET = 1.5551
330 Foot ET = 4.1244
1/8 Mile ET = 6.2979
1/8 Mile MPH = 113.6709
1000 Foot ET = 8.1849
1/4 Mile ET = 9.7783
1/4 Mile MPH = 142.3929
Try Using Rear Gear Ratio = 6.127
1/2 Mile ET = 15.442
1/2 Mile MPH = 171.25
KiloMeter ET = 17.928
KiloMeter MPH = 180.08
Mile ET = 25.068
Mile MPH = 200.49

Do you have a dyno sheet which shows HP and or Torque from the way the
engine was when you made these runs? That would sure help to dial in the
simulation.

Thanks,
Stan

[carl b]

I'm sorry but it's never been on a dyno before

[Pumaracing]

Stan, there's an old joke over here about what a person's doing if he's trying to combine sadism, necrophilia and bestiality at the same time. I'll tell it to you sometime.

[stevieturbo]

Does a Viper not use a 3.08 rear diff ?

And I can guarantee there is no way the early parts of the run will match those times.

Woodbridge is an airfield, and a slippy one at that. When I did my 200mph runs, I was still breaking traction at 190mph on some. Grip did improve a little later in the day though

Neither of our cars will see 60fts less than 2.0s unless Carl was using some very grippy tyres. Even then I cant see them being much below that.

The bulk of the speeds will be attained later in the track due to the very poor traction.

[Pumaracing]

The correct simulation for a 196 mph terminal speed at 1 mile on road tyres for a 50/50 weight distribution rwd car weighing 3600 lbs with driver is as follows. Gearing and aero drag data from online sources.

60 Foot ET = 2.31 @ 34.5 mph
0-60 mph = 4.16s
1/8 Mile ET = 7.91 @ 107.4 mph
1/4 Mile ET = 11.58 @ 137.7 mph
Kilometer ET = 19.95 @ 179 mph
Mile ET = 27.16 @ 196 mph

Flywheel Horsepower = 705

Edited by Pumaracing on Thursday 4th June 12:30

[Stan Weiss]

stevieturbo said:

Does a Viper not use a 3.08 rear diff ?

And I can guarantee there is no way the early parts of the run will match those times.

Woodbridge is an airfield, and a slippy one at that. When I did my 200mph runs, I was still breaking traction at 190mph on some. Grip did improve a little later in the day though

Neither of our cars will see 60fts less than 2.0s unless Carl was using some very grippy tyres. Even then I cant see them being much below that.

The bulk of the speeds will be attained later in the track due to the very poor traction.

Stevie,
Thank you for that very valuable information.

Would you or Carl have an data logging from your runs?

Here is a revised run where maximum acceleration is never greater than .545 G's

60 Foot ET = 2.3020
330 Foot ET = 5.8242
1/8 Mile ET = 8.3982
1/8 Mile MPH = 99.5908
1000 Foot ET = 10.4558
1/4 Mile ET = 12.1548
1/4 Mile MPH = 134.4697
Try Using Rear Gear Ratio = 4.794
1/2 Mile ET = 18.049
1/2 Mile MPH = 166.67
KiloMeter ET = 20.594
KiloMeter MPH = 176.44
Mile ET = 27.864
Mile MPH = 196.65

Stan