Correct gear ratios?

[Nathan Pasho]

Nick suspects the gear ratios may be off.

This is the only information I was able to find on the internet for the 2cv6 gearbox.

first=5.203,
second=2.656,
third=1.785,
fourth=1.315,

final drive = 4.125.  

Does anyone know if these are correct?

[Nick Roads]

gears seem fine perhaps it is the rev range, torque and bhp and settings you may need to consider

I have no engine knowledge (or ability) but the posts below particularly from terry collier may help in setting up the sim engine (just search under rev if link is wrong below)

http://2cvracing.org.uk/phpBB2/viewtopic.php?t=707&highlight=rev

cheers

[TerryCollier]

Hi

I am sending you an Excel Worksheet seperately that might help. You do not mention the symptoms so I am assuming the cause. I think that you are not matching the gear ratios to the designed power output of the engine. If your gear changes slip out of the power band then you will hesitate then pick up as you hopefully get into power. This is the biggest problem with the 2CV engine and this gearbox.

You have to design an engine which will give you a high HP but which lasts over a range from 4000 to 7000. This is not easy but if you only have a 10% drop across this range then the car will perform. The tendency of this engine is to meet walls. So the power will halve in 500 rpm ie from 6500 to 7000. The skill in the design is to spread these walls apart as far as you can. This is difficult.

Most of the drivers will recognise the scenario where holding 3rd gives you no more speed but changing to 4th is like braking. Does mess you up on corners.

If anyone in the Club wants these calculations send me an E-Mail and I will forward it to you. It does not seem to be the thing to put into a Post.

Regards

Terry

[Nathan Pasho]

Nick says he's downshifting too much, so it probably is a weak low rpm problem.  

I have been flattening the torque curve, you say it is the horsepower curve that needs to be flat?  What rpm is your torque peak?

I have tuned the engine to give the correct lap times, so when I boost the low rpm power, I am going to have to shave somewhere else or it will be too fast.