Improving 0-60mph time

[100SRV]

I decided to measure my car's 0-60mph time recently, with the aid of a hand-held GPS. I did two runs in the same direction as follows:

start in 1st through 2,3,4 time taken: 11 seconds
start in 2nd through 2,3,4 time taken: 12 seconds

I was a little dissapointed to say the least. After analysing the GPS data (logging every second) I found that the 0-50 time was about 8 seconds whilst the drag to 60 was slower. It seemed as though the car couldn't quite reach 60 in third gear but my calculations say otherwise.

What should my next step be to improve this (other than a bigger engine)?
I know smaller diameter tyres will help, and I will try to do some runs with maybe 28" diameter ones fitted.

Another test is to remove the airbox and try the runs with the K&N cones directly on the SU's in case the induction system is restricting the engine at high rpm.


Background data:
The car has a standard 3.9 litre SU carburetted Rover V8 breathing through a large K & N cone filter in a large capacity airbox / induction system.
The needles are BBC profile.
The exhaust is a straight-through 2.5" bore system.
The gearbox is an LT77 driving through 1.222 ratio transfer box and 3.54 differential.
The tyre diameter is about 32" Kerb weight is 1350kg.

(I think the engine could do with some new piston rings but it certainly isn't knackered.)

Do the times match other PH'ers expectations?
cheers,
100SRV

[shouldbworking]

The measure of performance in such vehicles as yours is not in 0-60 times. Play to its strengths eh.

[Fidgits]

shouldbworking said:

The measure of performance in such vehicles as yours is not in 0-60 times. Play to its strengths eh.

what he said.

standing sprint to 60 is a pretty arbitary figure, and not really any use unless your american and like 1/4 mile sprints.

With your car, concentrate on its ability to go up muddy hills!

[Alex]

As you point out, a handheld GPS updates every second, so your figures are only accurate to +/- 1 second.

And you say it can't quite reach 60mph in 3rd? You mean 2nd, surely?

Nevertheless, 10 seconds 0-60 for a V8 non-Vitesse SD1 sounds about right.

[rev-erend]

Take the engine out and put it in a Dutton (or similar) that should improve the 0 ~ 60

Or just buy a V8 TVR - as they have done this already

[Calorus]

I'd say it sounded way slow - but that above all, if you're in 4th when you get to 60, you've already spent about 2 seconds with the clutch down. An SD1 should just about make 60 in Second, it the driver, not he car that casing the time droppage.

[100SRV]

All good suggestions - as you say play to it's strengths!

I was more curious than anything else; the car is rapid enough as it is given the mud tyres and soft suspension (next area for improvement) it runs on.

However I was surprised at how slow it seemed, once measured. GPS inaccuracy won't help, meither will the slow-shifting LT77 but I certainly gave it a good thrashing.

Measured times are:
mph
Time 1-2-3 2-3
0 1.6 11.2
1 17.3 17.3
2 20.5 25.4
3 28.4 26.9
4 36.1 39.6
5 37.7 42.7
6 42.7 42.7
7 45.7 45.7
8 48.8 52.0
9 51.9 51.9
10 55.1 56.9
11 60.0 58.2
12 60.0 63.0
13 66.1 66.1
14 64.6 66.1
15 63.0
16 69.2
17 66.1

And using the formula MPH/1000rpm = 2.976D/ MTR where:
D Tyre diameter in inches (more accurate to use 2 x rolling radius)
M Gearbox ratio
T Transfer ratio
R Differential ratio

I got the following figures:
N V, mph
rpm First Second Third Fourth Fifth
1000 6.8 10.5 16.0 22.4 9.8
1500 10.1 15.8 24.1 33.6 14.7
2000 13.5 21.0 32.1 44.8 19.6
2500 16.9 26.3 40.1 56.0 24.5
3000 20.3 31.5 48.1 67.3 29.3
3500 23.6 36.8 56.2 78.5 34.2
4000 27.0 42.1 64.2 89.7 39.1
4500 30.4 47.3 72.2 100.9 44.0
5000 33.8 52.6 80.2 112.1 48.9
5500 37.1 57.8 88.3 123.3 53.8


Funny thing was that the GPS indicated a speed of 55mph when the engine seemed to be flat-out in third - this corresponds to 3500rpm in third gear (if my sums are correct). I am getting full travel at the carburetter butterflies.

The engine is non-SD1 but it has late (i.e. 4.0 / 4.6 type cylinder heads machined to suit composite gaskets (CR 9.35:1)

cheers
100SRV

Edited because I realised that the previous in-gear speeds were for a 1.4 ratio transfer box - now corrected to 1.2 - perhaps I'd better check the ratio because according to the revised table I'm missing even more speed....

Edited by 100SRV on Wednesday 17th January 16:36

Edited by 100SRV on Tuesday 30th January 08:31

[pentoman]

Playing with my own data logger (one with accelerometers and 5hz sample rate for more accuracy) it's amazing how important nailing a perfect start and getting quick gearchanges in is. Bog down just a bit and you'll lose 1/2 a second to one second. Also if 2nd will stretch to 60 it's a bonus.
It's made me realise 0-60 is fairly silly. You may be able to measure 30-70 for better comparison?

Great car by the way!

[100SRV]

Hi Pentoman,
thanks! A true "sports utility" I suppose?

To be honest both the start and gearchange could do with improving, it bogged a little in first and there was a lot of clutch slip by me when starting in second. I think I ought to try some better ATF in the main gearbox, perhaps a synthetic might help gear change quality?

I will try the intermediate speeds like 30-70, 40-70. Anything over 70 is pretty pointless as the canvas does an impression of a braking parachute!

100SRV

[SneakyNeil]

Agree with pentoman, you need to absolutley *nail* the start. Just let your foot slip off the side of the clutch and let the pedal ping up on it's own, you need to find the right RPM to do this at so that you don't bog and don't get too much wheelspin. Gearchanges should just be stamping on+off the clutch as fast as possible with no hesitation at the bottom... It's murder on the clutch/synchros/driveshafts/engine mounts, especially on 4wd!

[leorest]

Reduce weight, improve aerodynamics, then break out the laughing gas

[100SRV]

Thanks for the suggestions. It is pretty difficult to reduce it's weight as there is not a lot to it! Apparently the 100" Wildcat frame (precursor to the Wildcat 200) is only about 40kg lighter - it omits the box-section chassis in favour of a full tubular space-frame. I can jettison the spare wheel and other crap but those things are in the car because they are dead useful and I don't posess a magic wand!

I did another check on Vmax in 2nd and 3rd gears - around 45 to 48 for 2nd and about 68 for 3rd. That kills the "I've got the wrong transfer ratio" theory - it's definitely a 1.222 and the prefix on it's serial number bears this out.

Might give up on improving the drag race time - I don't want to wreck the powertrain for the sake of a few seconds.

Nitrous Oxide - a nice idea!

Has anyone succesfully mated a 5.7 litre Chevrolet to a ZF S5 gearbox? :-)

100SRV

[Jwb]

A rolling road tune up will give benefits. I would gues you have fitted K&N filters and the recommended needles, however a RR tune up will optomise what you have and is the best value in terms of bhp to time and £.

As as been said, the start is very important.

[cerbagriff]

If your interested in off the line acceleration, drag racers do this with the smallest diameter rims they can use on the back/drive wheels with the highest profile tyres and lower tyre pressure. Apparantly this helps the tyres to get and maintain grip.

[texpis]

Hi I have a 88 inch Tomcat with 4.2 v8 janspeed exhaust K&N filter 4.6 heads and fuel injection. I measure the 0 to 60 on a digital speedo calibrated to the tyres with 28" tyres I got it down to just above 7 seconds with 32" simex 8.5 secs and that is with an engine with 1500 miles on hopfully quicker when loosened up. I would ditch the SUs and put either fuel injection or weber carb.
Mick

[chuntington101]

LSx engine should fit in the same pace as a rover V8. the problem is the gearbox! most will be making over 350bhp (ls1) or even over 400bhp (ls2) and a hell of a lot of torque to go with it. oh and thats stock by the way!!!!!

this is great if you can fit the gearbox of choice, the T56, but its a big heavy thing hence why it can take the pwoer lol.

other alternatives would be a built T5 (from a cossy) but agian your going to be pushing even a well built one. plus you got to find a way of getting the power to the ground! lol

but if you could get a LS1 in there you will be glad to know that they take N2O VERY well (thanks to big cylinders). a 200bhp shot on a stock engine is not unheard of.

i say go for it!

thanks Chris.

[100SRV]

Hi,
350 Chevy is a bit excessive as I'd like to minimise the amount of engineering work required - I think refinement of the exisiting setup is the answer!

if I went down the EFI route could I use a THOR plenum with a 14CUX injection system? How much of an improvement in engine performance is the THOR / Motronic setup over the 14CUX / GEMS system?

cheers,
100SRV

[D_G]

Just hook a twin turbo supra up to it via a short (but strong) towrope

[100SRV]

Hi D_G,

I doubt if the Supra would have the torque to drag both of them to 60mph rapidly!

I have been doing some more experimenting with gear changes and when to change up (it revs quite happily to about 68mph in third). I've also found a set of wheels to which I can fit some smaller diameter tyres for road use only. When I have finished changing the brake master cylinder and servo I'll do a few more test runs and post the results on here.

100SRV

[D_G]

Only kidding mate

Have you considered NOS, used it myself and is really good if used in small bursts.

Dave