[slapper]

Ken - yes, drag cars & street cars are different but they are equally affected by the same factors ie weight transfer, traction, gearing etc. I agree gearing is part of the equation but I think you'll find the major contributing factor in your example between the XR8 & the SS would be the SS has a better power to weight ratio & more importantly, a stack more torque.

 

[Guest]

Ok put the XR6T into a program and ran it down the 1/4 with the 2 different gear setups.

Actual Ford gearing for the Ford Falcon BA XR6T 2002 Manual
Gears
2.95
1.94
1.34
1.0
.73

Final 3.45

Km/h
0-40 1.7
0-60 2.6
0-80 4.4
0-100 5.9
0-120 8.5
0-140 10.9
0-160 13.8
0-180 18.4

0-100m 6.1
0-400m 14.2 @ 160Km/h
0-100m 25.8 @ 208.1 Km/h

Terminal Speed of 259.5 (if no limiter of course)
Time taken to reach top speed 173.21 sec
Distance Covererd to get to top speed ~11.5km


Proposed gearing for the Ford Falcon BA XR6T 2002 Manual
Gears
3.5
2.14
1.39
1.0
.78

Final 2.92

Km/h
0-40 1.7
0-60 2.6
0-80 4.5
0-100 6.0
0-120 8.5
0-140 11.2
0-160 14.1
0-180 17.8

0-100m 6.1
0-400m 14.2 @ 161.1Km/h
0-100m 25.9 @ 204.4 Km/h

Terminal Speed of 250.9 (if no limiter of course)
Time taken to reach top speed 106.7 sec
Distance Covererd to get to top speed ~6.5km

All other factors were left the same in the test, only the ratio's were changed. Also The program can not emulate traction control so there is wheel spin taken into account above.

{Edited} added fuel consumption details.

The program also estimated fuel consumption (not very well)
Fords gearing produces
19.8/100 City
13.0/100 Highway
16.7/100 Combined

Proposed gearing produces
18.3/100 City
11.6/100 Highway
15.3/100 Combined

So although the figures are obviously WAY out, they can possibly be use to decide relative fuel consumption. So the proposed gearing is possibly more fuel economical.

 

[slapper]

Interesting stuff, but curious re 3.45 ratio as the program calculates a 0-160 at 13.8 sec yet 0-400m is 14.2 sec (but still at a terminal of 160)? Shouldn't these times be the same or am I missing something? Why is time & distance to reach top speed have such a massive difference between the 2 set-ups? What program did you use to crunch these numbers?

 

[Guest]

The program I am using is:
CarTest - Car Acceleration Simulation, Version 4.5
Copyright (c) 1992-98 Patrick Glenn, All Rights Reserved

The reason for the 0-160 13.8 and the ET of 14.2 is the fact that 160km/h is 6000rpm in 3rd gear. So there is no acceleration due to the gear change between reaching 160km/h and hitting the 400m mark.

During a gear change because 0 power is being put to the ground and there is a large amount of air resistance (friction) the car starts to slow down until 4th gear is engaged and the power re-applied.

The reason for the massive difference in that the last few km/h take such a long time to reach. The 2 different setups reach 250km/h at 3950m and 3635m for the Proposed and Ford setups respectivly.

 

[slapper]

Thanks for that. Does anyone have the Sammit Brothers drag racing program?

 

[T3man]

Mighty Highlig > Yes, thanks for that - I knew someone out there had a program to test the figures on - makes it all very interesting and looks like I'm not too far away with my reckoning.

When I get my XR6-T it'll probably be an auto ... sigh ... never before willingly purchased an auto if a manual was available.

 

[russellw]

Some very interesting points here and excellent commentary.

Just a couple of clarifications:

1. The comment that ET's are effectively determined in the first 60' is quite correct. Other factors will influence the terminal speed but the rate of acceleration is determined by launch and can be mapped very accurately with ATS equipment.

2. The gears set in the XR6T box is the former V8 gear set - and yes it has been chosen for the greater torque capacity.

3. Whether we like it or not the use of the T5 box and the V8 gear set is a cost effective exercise that allowed the vehicle to be priced where it has been. This is also, undoubtedly, the reason for the flat torque curve to ensure that the torque capacity of that box is not surpassed. Simple mathematics tells me that the 240 kw Turbo motor should produce a somewhat higher torque peak but that's the sacrifices that manufacturers have to make to achieve budgetary targets.

Perhaps when there are a few more pennies in the Ford coffers and a bit more development time up the sleeves, we will see some improvements in this (one) remaining area.

Wouldn't mind a sneak peek in the skunkworks right now either!

Cheers
Russ

 

[Guest]

Here are the specs if you are thinking about getting the auto

Gearing for the Ford Falcon BA XR6T 2002 Auto
Gears
2.50
1.49
1.0
.68

Final 3.45

Km/h
0-40 1.8
0-60 3.0
0-80 4.2
0-100 6.5
0-120 8.6
0-140 11.0
0-160 15.1
0-180 19.4

0-100m 6.2
0-400m 14.5 @ 156.5Km/h
0-100m 26.3 @ 204.5 Km/h

Terminal Speed of 251 (if no limiter of course)


From what i have hear the strength of the manual gear box is questionable if the car is modded. So you could do a couple of mods and the auto would more than match the manual.

Personally i have been driving an auto for way too long and look forward to the chance to drive a manual again.

 

[slapper]

russellw - your point #2 is interesting, I didn't know that, thanks for the input.

Mighty Highlig - were all of your calcs using a rev limit of 6000 or 7000rpm?

 

[Guest]

I used the 6000rpm redline as published by Ford.

¨X¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨TENGINE¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T
¨U Disp: 3984 cc. Loc:FRONT Type:TURBO
¨U Horsepower: 240 kW @ 5250 rpm
¨U Torque: 450 Nm @ 2000 rpm
¨U Comp Ratio: 8.7:1 Redline: 6000 rpm
¨U Start rpm: 2100 with Clutch: DUMP
¨^¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T
¨X¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨TDRIVETRAIN¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T
¨U Transmission: 5 speed MANUAL
¨U Gear Ratios 1st: 2.95:1 4th: 1.00:1
¨U 2nd: 1.94:1 5th: 0.73:1
¨U 3rd: 1.34:1 6th: :1
¨U Final drive ratio: 3.45:1
¨U Driving wheels: REAR
¨^¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T
¨X¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨TCHASSIS & BODY¨T¨T¨T¨T¨T¨T¨T¨T¨T
¨U Car test weight: 1710 kg.
¨U % weight on front wheels: 50 %
¨U Wheelbase: 283.0 cm.
¨U Tire section width: 235 mm.
¨U Tire circumf. (opt.): m.
¨U Wheel diameter: 43.2 cm.
¨U Tire profile: 45 %
¨U Coefficient of drag: 0.310
¨U Frontal area (opt.): sq.m.
¨U Overall height: 144.5 cm.
¨U Overall width: 186.4 cm.
¨U Ground clearance: 20.1 cm.
¨^¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T¨T

I made the Auto 20kg's heavier.
All the specs are correct as officially published by Ford or Wheels.
I estimated the weight on the front wheels, the groud clearance and the drag.

 

[slapper]

Just a few variables to input hey!? Well done! I have reservations as to the accuracy of the package's quarter mile times as the 3.45 scenario reached 0-160kph a full 0.3sec quicker than the 2.92 version yet it lost all of this before the line. Although 0.3 sec doesn't sound much, @160kph it is equal to almost 3 car lengths - how could you possibly lose 3 car lengths by slamming it into 4th just before the line is beyond me, maybe 1 car length if you're real unlucky?? I'll take mine up to Willowbank (stock trim) & see how I fare after its run in.

 

[PigDog]

Slapper, comparing 0-speed (ie/ 160kph) is completely different to comparing 0-distance (400m). Getting to 160kph .3 seconds before another car will no way equate to 3 car lengths (or any car lengths), think about it at the time of the 1st car reacing 160kph the other car is probably at 159 or 159.5kph.

Now if another car is doing 1kph less than you after a set amount of time do you think it would be 3 car lengths behind? Obviously it'll be right beside you or right up your ass. Since you've been to the drags you'll know that it's not uncommon for a car to cut a better ET than another car even if it's terminal speed is lower, so you might not even be ahead at all.

 

[slapper]

Pigdog, I take your point but in this scenario we're comparing 2 identical vehicles with identical power, just different gears. Given the program has a 0-160 of 13.8 seconds for the 3.45 ratio, you cannot tell me that this vehicle is not going to be ahead of the other when it has reached this speed a full 0.3 seconds quicker. Doing the math, 0.3 sec at 160kph = 2.8 car lengths (assuming a constant 160 kph, a bit less with a full calc.). Unless the 2.92 car has a better power-to-weight ratio or the driver of the 3.45 car is a real unco, the higher geared car is not going to catch that up even with the lower geared car shifting into 4th before the line. The program will have a variable set in it which assumes the length of time a gear change is effected which I think is overstated. For example, my VLT regularly runs with a modded wrx, even though my car is an auto & is constantly on full boost, the wrx never drops any distance when we race (although he does go thru some gear-boxes!). While these programs are an excellent guide to quarter mile times they still make a number of assumptions which will never be 100% indicative of a physical run down the 400m. The only program that I've seen which was close to flawless (for my VLT anyway) was the Sammit Brothers program which had an enormous amount of data that was obtained from the track that was used to set the variables, not just mathematic formulae.

 

[Guest]

Well I have all the 'enviroment' parameters that this program uses. These were NOT set up by me, I assume they were set up by the guy who wrote the program. As you can see for the Manual the shift time is .5 sec which would surely make up the .3 sec diff at 160km/h.

I can change these variables but i wanted to leave everything standad and only modify the gear ratios.

Air Temperature: 18 deg. C.
Barometric Pressure: 994.92 mbar
Relative Humidity: 55 %
Elevation above Reference: 0 m.
Headwind (+), Tailwind (-): 0 kmh
Road Grade (+=Ascend, -=Descend): 0 %
<B>Shift Time, Manual: 0.50 sec.</B>
Shift Time, Auto: 0.30 sec.
Engage Time, Manual: 0.20 sec.
Engage Time, Auto: 0.10 sec.
Clutch Slip Max. Time, Manual: 5.00 sec.
Brake Release Time at Start, Auto: 0.10 sec.
Trans. Engage Method-Lin,Prog,Regr: R
Shift@O=Optim,R=Redline,D=Driver,P=Prog: O
Engine Free Decel Rate: 2000 rpm/sec
Engine Bog Down Decel Rate: 4000 rpm/sec
Engine Wheelspin Decel Rate, Manual: 500 rpm/sec
Engine Clutch Slip Decel Rate, Man.: 250 rpm/sec
Engine Trans. Slip Accel Rate, Auto: 750 rpm/sec
Engine Wheelspin Accel Rate, Auto: 250 rpm/sec
Max. Coefficient of Static Friction: 1.00
Max. Coefficient of Kinetic Friction: 0.85
Coefficient of Rolling Resistance: 0.013
Tire Expansion Factor: 0.012 %/kmh
Hot Tire Pressure: 2.41 bar
Tire Tread to Section Width Ratio: 90.0 %
Wheel and Tire Weight: 20.4 kg.
Minimum Engine Speed: 700 rpm
Zero h.p. Engine Speed: 600 rpm
Turbo Start Speed: 3000 rpm
Max. Torque Conv. Slack Until, Auto: 2000 rpm
Low Max. Brake Torque Speed, Auto: 2000 rpm
Time Increment: 0.05 sec.
Start Time after Car Moves: 30.48 cm.
Mechanical Losses-Auxiliaries: 2.00 %
Mechanical Losses-Manual Trans.: 6.00 %
Mechanical Losses-Auto Trans.: 8.00 %
Mechanical Losses-Differential: 4.00 %
Mechanical Losses-Axles & Shafts: 5.00 %
Mechanical Losses-Torque Converter: 3.00 %
Max. Clutch Slip Losses, Manual: 10.00 %
Max. Trans. Slip Losses, Auto: 15.00 %
Max. Torq. Conv. Torque Multiplier: 2.25
Effective Engine Radius: 7.6 cm.
Drive Shaft Radius: 2.5 cm.
Center of Gravity from bottom: 30.0 %
Graphics Aspect Ratio (EGA): 0.75
Graphics Aspect Ratio (VGA): 1.00
Sound Effects (Y=Yes, N=No): Y

 

[Great White]

There is an old rule of thumb I read many years ago stating that the ideal take off ratio should equal 10.00. For example a 3.25diff multiplied by a 3.10 first gear = 10.075. anything over 10.8 - 11 results in a truck like first gear that has to be changed too quickly without having covered any real distance.So if we used the BA 2.95 first x 3.45 diff we come up with 10.1775. Using the proposed 3.5 first x 3.45 =12.075 which is just too high. To make this ratio viable we need to use the 2.92 diff x 3.5 =10.22. Futhermore I have never liked second gear ratios over 2.00 because unless third is 1.48 - 1.50 the revs drop too far.

Top Loader standard
1st 2.78, 2nd 1.93, 3rd 1.36, 4th 1.00

Close ratio "bullnose" has a 2.32 first

XB Borg Warner single rail
1st 2.84, 1.84, 1.36, 1.00

XC and XD single rail - 250 and 302
3.06 First and as above, and 351 for both uses 2.48 first.
It seems that higher first gear ratios(lower numerically) are tougher. All of the above is just my two bobs worth.

 

[PigDog]

Pigdog, I take your point but in this scenario we're comparing 2 identical vehicles with identical power, just different gears. Given the program has a 0-160 of 13.8 seconds for the 3.45 ratio, you cannot tell me that this vehicle is not going to be ahead of the other when it has reached this speed a full 0.3 seconds quicker. Doing the math, 0.3 sec at 160kph = 2.8 car lengths (assuming a constant 160 kph, a bit less with a full calc.).

I'm sorry mate but you're still misunderstanding..

If you were talking terminal speed at the traps your little 'car lengths' calculation can work - but it does not work for 0-speed (160kph). The 2nd car is not .3 seconds behind the 1st car in distance it is .3 seconds behind in reaching a set speed. It's a completely different kettle of fish.

 

[slapper]

PigDog - I understand what you're saying & it is totally correct but in this case I don't think it is a critical factor as the variables being distance, time & terminal speed are all at/very near the 400 meter mark. I bounced this off my bother (physics whiz) who said we were both right & both wrong. My point isn't disproving the laws of physics, it was just to state that the 3.45 would cross the line quicker if the gear change was effected in under .5 sec, something which the program would support.

 

[EDFUTURA]

I think everyone is missing something fairly important - ie. with the forced induction you'll find that a typical "fast" run will be done by getting out of first basically as soon as you can off the line then punching thru the gears from second onward - and not stringing it out to the 6000rpm limit as that won't be necessary with the way the turbo delivers power.

So that's why 1st seems too low and close - it's really not intended as an acceleration gear - maybe it's there more for tractability towing yachts up boatramps etc.?

So for practical purposes you shouldn't think of 1st-2nd as being in the equation - instead the "first" change will be 2nd-3rd which will see 100kph come and gone then the second change will be 3rd-4th and bye bye 400 mark - so that means effectively two changes over the quarter - both right in the "fat zone" of really strong torque/power flow.

Remember, the forte of a large capacity turbo motor will be HUGE torque/power flow so you drive it like a big V8 not a revy sportster.

Just my opinion anyway :s5

 

[T3man]

EDFUTURA> your basic argument is supporting mine - but you aren't keeping count of the gearchanges very well - even if you short shift into 2nd, as you seem to be advocating, there is no need for a 2-3 change before the 100kph barrier, and likewise, if you use "my" gearing there is no 3-4 change before crossing the 400m.

My argument is, that by using the huge amount of low down torque this motor has, you should be gearing it to take advantage of that, and the fastest ETs will be done by choosing ratios that result in fewer gearchanges. Ford haven't done this IMO.

 

[EDFUTURA]

T3man - ooops - yep, you're quite right about the gear changes - I didn't look close enough at the tables there (even my machine is still in third thru 400m). :s5 - but my basic point is that for performance purposes first simply has to be ignored. Unfortunately, I think that having the gears configured the way they are is the price to pay for having what's ultimately a compromise between a family sedan and a sports car.