timeslip.hu - interactive online dragracing

Before and After

1. Reducing weight click

2. Unknown problem causing power fall click

3. Effects of cold weather click

4. BMW launch control (ASC) click

5. Lightened flywheel click

6. Full 1/8 run vs. backing off at half track click

7. LGP vs. Petrol difference in performance click

8. Brake test with and without ABS click

9. Switching off a cylinder bank ( V8 -> inline 4 ) clikk

1. Reducing weight (2001)

This speed-time chart shows the acceleration of an 1100 kg vehicle.

First we logged the car with 4 passangers, this is the green line.
Then, we did it again with 2 passangers, that's the red line.
We selected the best of 3 runs of each config. Same road, same time.

The difference is clear, 0-100 km/h time reduced by more than 2 seconds from
13.40 seconds to 11.26. It's quite a difference, innit?

2. Unknown problem causing power fall (2001)

Again, it's a speed-time chart, these are my Renualt 5's two 1/8 mile runs.
The green is an earlier run, where the car was working fine.
In the red run the car was loosing power in 3rd gear at high revs. (from around 5000 rpm)

As you can see, speed-wise the red run is ahead in the first 7 seconds, then it
falls back spectacularly, I also shifted earlier than normal when I felt the problem.

This is the only race I lost in 2001, and it was because of this problem. It was very close...

I don't know what was causing it. Probably just crap fuel, I never noticed this later.

3. Effects of cold weather (2001)

With winter approaching, I decided to test how much does the cold weather
helps my turbocharged, intercooled Renault 5 GT turbo.

The first chart shows speed vs. time over the usual 1/8 mile track.
The red line represents the run I did on 2001 szeptember 13th at the Rabaring (cca. 16 °C),
the blue run I did on November 25th. (3 °C).

I did quite a few runs in November, five in fact.
The difference between the best and the worst was 0.2 seconds.
(In order: 10.10 s, 10.22 s, 10.20 s, 10.08 s, 10.28 s)
In September my best was 10.43 seconds.

0-100 km/h in the race was 7.86, and in the cold I could manage 7.20 s.
But I revved the car higher than in September, so this comparison is not exactly ideal.

On the second chart it's the same two run's wheel power vs. time chart.

4. BMW launch control (ASC) (2002)

The test was conducted with a BMW E46 320i.
The two runs were about 5 minutes apart, on the same, slightly wet tarmac.
It only shows the acceleration in 1st gear, as from 2nd gear the 320i is way too powerless...
Whith ASC deactivated, the car was wheelspinning all the way.

The red line shows the speed vs. time and distance vs. time chart of the car with ASC enabled.
It's clear to see that the red car starts to gain a speed advantage after the 1st second.
As it has a higher speed, it starts to gain distance as well, and while the speed difference
reduces to almost zero at the 3.5 s point, it has already build up a leed of about 2 meters.

So, ASC helps in the wet unless you're a pro...

5. Lightened flywheel (2002)

An interesting subject. The common understanding that lightening the flywheel will make you go faster. It helps revs to pick up faster, yes, but it was side effects as well. Well, my car was overhauled during the Winter of 2001/2002 and a lightweight flywheel was put in. I was eager to see the effect.
I was quite surprised that I was slower over the 1/8 mile than last year.. Obviously, I was wondering why?And the new engine was more powerful!
The distance-time chart shows one run with each config, the green being recorded with the OE flywheel, and the red with the new, lightened one.
The yellow line represents the distance between the two (virtual) cars.
As you can see, with the light flywheel I lost almost 4 meters in the first 4 seconds, then with the help of the more powerful engine I managed to pull back and almost catched the car with the standard flywheel.

But why did I collected this 4 meter deficit?
Well, last year I could hold the car on the traction limit, but now it's much harder. It's so much more willing to wheelspin than before, and if I lift up a bit, revs drop and it takes ages to get back to speed. To prevent this happening I was keeping the revs up high, causing more severe wheelspin.

Possibly if the engine would have been a bigger, naturally aspirated one, this problem wouldn't caused my loose time, but I've a tiny turbocharged 4 pot.

6. Full 1/8 run vs. backing off at half track (2002)

Another interesting subject. Someone told me he did such a terrible ET because he ran out of fuel midtrack. Ok, I thought, let's see how much time will you loose, if you accelerate only for half track (100 meters = 330 feet) and then just let the car roll freely... Well, for the test I've choosen the company car I had at the time, a 60 hp Opel Astra 1.4 8v.
The charts shows both speed vs. time and distance vs. time.
As you can see, until the 9 second mark, both cars are travelling at the same speed, and they both are at the same spot. Then in the "green" car I lifted off, selected neutral, and just waited for the finish line. No braking of course.
In this run I lost 0.57 seconds compared to the other run.
13.3 @ 92 km/h vs. 13.87 @ 72 km/h to be precise.
Speed-wise of course it's a big difference, but since you're already have a good speed at the lift off mark, time-wise you didn't loosed too much.
Well half a second is a big difference of course, but it's only 4% worse, while the speed difference is 28%.

As a note I have to tell, it was quite hard to do two similar starts... :)
I could have cheated with manipulating one run's data, but I wanted it to keep real.

7. LGP vs. Petrol difference in performance (2003)

I was able to test two different cars in Petrol and in LPG mode.
Both are switchable, they have two fuel tanks, a big one for LPG and the normal for petrol. The tests were done at the same place, at same time.
First is a Trabant 1.1. This is a later Trabant with a four stroke engine sourced from VW. The car's ful log is also available on the site. (click here)
It's clear as revs rise power drops with LPG (red line) opposed to climbing steadily until the gearchanges with petrol.

The other car was BMW E36 316i.
Here we only tested in 2nd gear, to get the whole power chart.
From around 3.5 seconds the clutch wasn't slipping anymore and we powered into the limiter. The timing difference of the charts is caused by the slightly different starts, but this doesn't blur the clear power advantage of the petrol powered car. The difference is not huge, and loosing 2-3 bhp is something you can live with for cheaper motoring.

8. Brake test with and without ABS.

There were debates recently on various forums whether ABS helps to reduce braking distances as well, or just help to maintain control over the car during hard braking.
I wasn't able to do new tests, but I had dig up some tests we did in 2001.
The car was a then brand new Subaru Impreza WRX.
The test were done over the same road, in dry roads with winter tires. The temperature was around 0°C. First we did the test with ABS on, then took out the fuse, and voila ABS disengaged. Both brake tests are available to see in the brake tests page.

The red line shows the deceleration force with, and the green without ABS.
There's a clear hole in the green line at around 1.2 seconds. As the wheels locked up, -which is inevitable during hard braking without ABS- the car lost direction a bit,was heading into the ditch. To steer it back to straight, the driver had to lift off a bit, increasing the brake distance quite a bit.
The blue line shows the speed difference between the two cars against time. Obviously when both cars stop, the difference comes back to zero.

The yellow shows the distance between the two cars against time.
It's clear that when both cars comes to a halt, the distance between the cars is less than two meters! (6 feet) And most importantly, the difference is mainly caused by the lift off, not the inferior braking force!
In fact as you can see, the speed difference gradually reduces after the sudden increase caused by the lift off.

The blue and yellow line use the left scale. Positive values means the car with ABS has the advantage. E.g. at the 2 second point, it is travelling 3 km/h slower, and is behind the other car by around 0.7 meters. (around 2 feet)

We logged another car with and without ABS. It's a Honda Civic VTI. (photo)
It's quite easy to disable the ABS on a Civic. You have to pull away with the
handbrake on (not fully obviously), and above a certain speed the computer throws up an error and disable the ABS. From this point it will stay disabled while the engine is running, regardless of the status of the handbrake.

Once again, we tested in winter, dry tarmac, on 195/50R15 Pirelli Wintersport tires. We used the same strech of road, 5-10 minutes between the two tests.

Well , there is quite a bit of surprise here, with ABS disengaged the braking distance is shorter! The braking starts even, but after half a second, the non ABS car finds extra traction and gains a speed difference of around 3 km/h, which stays on this level for more than a second. Then the speeds starts to equal, but this time the non ABS is more than 1.5 meters ahead! (5 feet) There's an interesting comeback of the ABS car starting from around the 2.5 second point. I think this is caused by a driver 'mistake' in the non ABS car.
He simply didn't push the pedal hard enough.

Anyway, it's proved, that the braking distance can be both shorter and longer with ABS, it depends on a lot of factors, there's no simple answer in real life.

The blue and yellow line use the left scale. Negative values means the car without ABS has the advantage. E.g. at the 2 second point, it is travelling 3 km/h slower, and is behind the other car by around 0.9 meters. (3 feet)

9. Swithing off a cylinder bank ( V8 -> inline4 )

A friend had some problems with his Chevy Corvette a few weeks ago, causing dramatical power loss. It turned out it was caused by a blown fuse.
Whoo, I thought it must be logged! :)

So, first we logged the car with all 8 cylinders (see full log).
Then we removed the fuse for the left bank's injectors.

Thinking simply, we could think that half the cylinders will produce half the power. Far from it. Internal losses and power required to suck in, compress the air, etc... sap a lot of power.
The red line on the chart shows the wheel power with all 8 cylinders firing, the green is wheel power with only 4 cylinders firing.
Huge difference!
On 1/8 mile we timed 9.43 seconds with 8cyl and a poor 14.5 s with 4cyl.

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