1327 replies to this topic

[cheapracer]

Just a point on one of my points for (said in a 50's horror movie way) "the thread that wouldn't die!".

Did anyone see Vettels in car on the weekend and notice that in top down the straight his led tachometer display told him when to change with plenty of notice from the first led's lighting progressing to max rpm but when in top didn't even reach the first led's before braking.

As mentioned before, this is a real world decision and possibly geared so tall because they may have been anticipating spending some time behind KERS equipped cars which they would need to be tall geared to stay in the tow.

[phantom II]

Those are the correct ratios. Final drive 3:42 The two over-drive ratios account for the stock car's 30mpg. Does pretty good in the city also. I get around 14mpg in my ZR1. My point in my posts was to plead with the theorists that there are other factors to consider during max acceleration runs which were not included in the optimum shift points derived from the graphs. We are all familiar with KERS not been used below 60mph. I don't dispute the theory. A stock Z06 gets a better elapsed time using 5500. This set of the firestorm.
I got rid of the Goodyear run flats the day I got the car and replaced them with Michelin Pilot Sport PS2 ZP, but I still short shifted. The only important gauge was the ET. The Z06 needs the ZR1s ratios. It's a fine line to maximize traction with my 62 year old brain's TC mechanisms. The softer spring rates did the most for traction after the tires. In the 1/4, I power shift brutally and with these ratios and the Good-Years, I would get excessive wheel spin from 1st to 2nd and from 2nd to 3rd. The Michelin were only a slight improvement but I still short shifted. What is not shown on these graphs, is the sharp jump in torque on the drive shaft immediately after the shift. The higher the rpm, the higher the toque spike. Its not easy to slow the rotation of that big crankshaft.
Audi couldn't get the TC to work on their diesel race cars because of this spike.
Non of this happens in the ZR1 as long as you launch at 2300rpm even with its much taller 1st gear.See below.
The twin-disc clutch system also contributes to the ZR1's ease of opporation and refined feel. It has twin-disc system which enables a 25-percent reduction in inertia, thanks to smaller, 260-mm plates, corresponding to a pedal effort that is similar to the Corvette Z06's 290-mm single-disc system.
The rear axle also is stronger in the ZR1 and features asymmetrical axle-shaft diameters that were developed after careful testing to provide optimal torque management. The axles are also mounted on a more horizontal plane that correlates with the wider width of the rear wheels and tires. The rear spring rate is also much softer than the Z06.
What a lovely lovely car.

First:

2.29

Second:

1.61

Third:

1.21

Fourth:

1.00

Fifth:

0.81

Sixth:

0.67

Reverse:

3.11

Final drive ratio:

3.42

Joe Bosworth, on May 10 2009, 07:42, said:

PII

I have taken the time to plot graphs of HP and T on the data that you have provided.

Not knowing anything better I used gearing of
1st 2.66
2nd 1.78
3rd 1.30
4th 1.00
5th 0.74
6th 0.50

These are really lousy gears for what you have for an engine. (If you have something else let us know.) The four lowest gears come vaguelly close to intercepting but not quite. The upper two don't come within a mile of intercepting.

What the graph says is that for best performance you need to go out to ignition cutout or probably about 7200 or so for each shift. (Guessing a bit for what you get after 6700.)

If you are short shifting you are cheating yourself of performance unless you are doing so to get out of wheelspin zone. If this is the case then it would be interesting to know at what revs in what gear you are breaking loose. With that info we can calculate the tyre traction forces which might be interesting.

Sorry you didn't get this data out earlier. I was thinking this thread finally died for lack of any useful further info and everyone agreeing to hush up while not fully agreeing.

Regards

[gruntguru]

cheapracer, on May 11 2009, 23:41, said:

Just a point on one of my points for (said in a 50's horror movie way) "the thread that wouldn't die!".

Did anyone see Vettels in car on the weekend and notice that in top down the straight his led tachometer display told him when to change with plenty of notice from the first led's lighting progressing to max rpm but when in top didn't even reach the first led's before braking.

As mentioned before, this is a real world decision and possibly geared so tall because they may have been anticipating spending some time behind KERS equipped cars which they would need to be tall geared to stay in the tow.

Is it possible that the first LED illuminates at or just beyond the power peak? That would make sense for optimum shifting which would be well past the power peak (probably at redline) and would also still be around max power at top speed in the straight. A hundred RPM or so below the power peak is still probably delivering 99%+ of max HP and that leaves some RPM margin for:
- slipstreaming
- other factors which might allow slightly higher top speed during the race
- lower gearing caused by tyre wear

Edited by gruntguru, 11 May 2009 - 23:39.

[Paul Ranson]

Equally possible, I'd have thought, that they don't light the lights in top. Why distract the driver?

Paul

[RDV]

....lights are there to indicate shift point, you set them at different RPM before rev-limit to give time to shift before you hit limiter....hence lower gears(which accelerate faster..) will be set with a bigger margin than higher gears, and you also have different colours, yellow then red....top gear does not need shift point indicator....

[Tony Matthews]

RDV, on May 13 2009, 23:24, said:

...top gear does not need shift point indicator....

Now you point it out RDV, it's so bloody obvious! Too obvious to occur to me, it seems...!

[gruntguru]

RDV, on May 14 2009, 08:24, said:

....lights are there to indicate shift point, you set them at different RPM before rev-limit to give time to shift before you hit limiter....hence lower gears(which accelerate faster..) will be set with a bigger margin than higher gears, and you also have different colours, yellow then red....top gear does not need shift point indicator....

Of course - why didn't I think of that?

[Bill Sherwood]

gruntguru, on May 14 2009, 08:34, said:

Of course - why didn't I think of that?

I suspect the driver would still like to know how much margin her has to go to the redline, in case he gets a good aero tow and/or using KERS to pass. If he's near the limiter and only just creeping past a car in front, he may use that extra information to change his strategy as to where to pass next time, etc.

[cheapracer]

RDV, on May 14 2009, 06:24, said:

....lights are there to indicate shift point, you set them at different RPM before rev-limit to give time to shift before you hit limiter....hence lower gears(which accelerate faster..) will be set with a bigger margin than higher gears, and you also have different colours, yellow then red....top gear does not need shift point indicator....

Doesn't need doesn't mean doesn't have but anyway, I have ears and it wasn't peaking.

[cheapracer]

Bill Sherwood, on May 14 2009, 13:41, said:

I suspect the driver would still like to know how much margin her has to go to the redline, in case he gets a good aero tow and/or using KERS to pass. If he's near the limiter and only just creeping past a car in front, he may use that extra information to change his strategy as to where to pass next time, etc.

]

Especially in practice in these unknown and constantly changing car specs where he may want to get behind a KERS car and establish his gearing with the aid of the led's.

[gruntguru]

cheapracer, on May 15 2009, 01:18, said:

Especially in practice in these unknown and constantly changing car specs where he may want to get behind a KERS car and establish his gearing with the aid of the led's.

KERS won't change the top speed much especially if the straight is long enough to approach terminal velocity. Even if the extra 10% power could be sustained for long enough (and it can't at 6 seconds), it will only increase terminal speed by about 3% ie another 500rpm. So even if the team gears the car for the power peak at top speed there will still be at least another 500 rpm before the 18k rev limiter.

Edited by gruntguru, 22 May 2009 - 06:33.

[ben38]

That's true
Get the lapsim demo version and simulate straight line
Aero cars (ie also big drag cars) are rubbish in straight line past 160 km/h
On formula cars drag is more important than power on straight as different aero set up from low to high downforce will get a drag coefficient so different that it will offset few % of power (or torque not to fall again in the engine guys dogfight^^)
On a GT car with no aero like a gt3 it could make a significant difference indeed

[PederN]

McGuire, on Apr 2 2009, 09:47, said:

Shelby et. al. did not say, "Horsepower sells cars; a wide power band wins races." They said, "Horsepower sells cars; torque wins races." That is what they meant and they were entirely correct. Shelby was right and you are wrong. Not surprisingly.

Does anyone know if Shelby (et. al.) actually said this, and in that case, when?

[McGuire]

PederN, on Oct 2 2009, 21:41, said:

Does anyone know if Shelby (et. al.) actually said this, and in that case, when?

I've only heard him say it about 50 times on the rubber chicken circuit etc. It's a stock phrase in his How-I-kicked-Enzo's-ass-story. Provocative (though it's really not) and folk wisdom-y, I suppose.

Anyway... you should be shot, hanged, and your corpse set on fire and dragged through the streets behind a Hindustan Ambassador for restarting this thread.

[gruntguru]

McGuire, on Oct 3 2009, 08:35, said:

I've only heard him say it about 50 times on the rubber chicken circuit etc. It's a stock phrase in his How-I-kicked-Enzo's-ass-story. Provocative (though it's really not) and folk wisdom-y, I suppose.

Anyway... you should be shot, hanged, and your corpse set on fire and dragged through the streets behind a Hindustan Ambassador for restarting this thread.

Yay!!! Torque wars - on again.

This old platitude needs a great deal of clarification to mean anything remotely correct. If Shelby said this repeatedly without clarification he was very naive. Folk wisdom is sometimes just plain dumb.

[Catalina Park]

McGuire, on Oct 3 2009, 08:35, said:

Anyway... you should be shot, hanged, and your corpse set on fire and dragged through the streets behind a Hindustan Ambassador for restarting this thread.

Is torque or horsepower more important for dragging bodies behind Hindsustan Ambassadors?

[Tony Matthews]

Just a decent tow-hook, you can't trust the bumpers.

[gordmac]

Hindsustan Ambassador, is that the one that is an old (1950's) Morris Oxford?

[carlt]

gordmac, on Oct 3 2009, 17:52, said:

Hindsustan Ambassador, is that the one that is an old (1950's) Morris Oxford?

Indeed

BMC- 'B' series -

All Torque and no Trousers

[cheapracer]

Catalina Park, on Oct 3 2009, 19:59, said:

Is torque or horsepower more important for dragging bodies behind Hindsustan Ambassadors?

Thats a problem because they have neither. They don't have heated rear windows either being in India unlike Lada's which need them to keep your hands warm while pushing them being in colder Russia.

I walked into a car dealer just the other day and said "I want an oil filter for my Hindsustan Ambassador" and the Guy replied "sorry mate, full stock, we're not buying cars this month.".

Edited by cheapracer, 04 October 2009 - 02:20.

[Tony Matthews]

cheapracer, on Oct 4 2009, 03:18, said:

Thats a problem because they have neither. They don't have heated rear windows either being in India unlike Lada's which need them to keep your hands warm while pushing them being in colder Russia.

I walked into a car dealer just the other day and said "I want an oil filter for my Hindsustan Ambassador" and the Guy replied "sorry mate, full stock, we're not buying cars this month.".

The fishing trip was obviously a disaster...

[Catalina Park]

gordmac, on Oct 4 2009, 02:52, said:

Hindsustan Ambassador, is that the one that is an old (1950's) Morris Oxford?

The later ones featured an Isuzu diesel.

[cheapracer]

Catalina Park, on Oct 4 2009, 15:49, said:

The later ones featured an Isuzu diesel.

The 'GT'

[Tony Matthews]

cheapracer, on Oct 4 2009, 09:40, said:

The 'GT'

What's that? Goat Tandoori?

[cheapracer]

http://www.hmambassa...er-overview.asp

Check it out, their truck has "enough power for air conditioning"

and "more earings"!!!!!!

Edited by cheapracer, 04 October 2009 - 11:07.

[Tony Matthews]

cheapracer, on Oct 4 2009, 12:05, said:

Check it out, their truck has "enough power for air conditioning"

2.7 kilometres/litre - is that good, or as bad as it sounds? Perhaps that's with the aircon on max...

Edited by Tony Matthews, 04 October 2009 - 12:06.

[gruntguru]

Catalina Park, on Oct 4 2009, 17:49, said:

The later ones featured an Isuzu diesel.

Is it a V8 or V10?

[Bill S]

At the dire risk of posting something that might start this thread again, I remembered I had a simple little program that does a pretty reasonable job of comparing cars in drag races and around tracks.
I've uploaded it to to my site so anyone can download it -> http://www.billzilla...temp/carsim.zip

It's got a bunch of typical cars that came with it, and a few others I've added - please ignore some of the odd experiments!
I remember using it to look at acceleration curves in the various gears, and it takes into account wind drag and a heap of other factors. Hope it's of interest to some.