report on 82 300cd stick conversion
 

We had the stick tranny installed last spring. It is hooked to a pretty fresh 617 turbo motor, using a 240 fw clutch and four speed tranny. I was a bit hesitant to use the 307 gear but decided to give it a try. It is working fine.

We have put about four thousand miles on it, maybe 12 fill ups. Our lowest mpg was 17+ our highest nearly 27. My daughter has it at Ball State. She lives pretty close to campus so only drives it in the evening over to the Architecture building and walks the rest of the time. And she drives it home to Lafayette on secondary roads from time to time, so no tank is purely highway or town.

It appears to be getting about the same as a 240d stick. I think it would hit about 27 on a long trip, maybe a bit more and probably would not go below 20 in town except in winter.

So I would say it is a pretty happy combination.

Tom W

How do yall like the driving experience now with this car configured as such?

I've been thinking of using a 3.07, how is acceleration?

It drives nicely. First and second gear feel very close together ratio wise....it feels really odd because of that.

Acceleration is in a word, Doggy.

I am not sure the boost and or enrichment is acting as it should though. But the car runs like a top and my daughter has not complained so I have not addressed it in any way.

It is being used as basic transportation. Although it looks really nice now and the paint and body looks very good, the leather is so old that the large parts of the seat are developing some pretty significant cracks. One of these days I am going to have to either find some palimino tex cd seats or get some work done on these replacing individual panels.

Also there is a vac issue that my indie has been unable to figure out. I may have to take it to a benz specialist in Indianapolis for that.

I think a 346 rear with a five speed would be perfect, but this is a big improvment over the automatic and taking off is not too bad, but the acceleration is leisurely.

Tom W

If only there was a 3.3x or 3.2x ratio to work with. The jump from 3.69-3.46 made a big (good) difference in acceleration and MPG, but going to 3.07 is too big a jump for me.

This is a rather interesting point.

Many folks like the manual because they believe that it's faster than the automatic. However, personally, I think that this is factually incorrect. The automatic benefits by some extreme slippage with the torque converter...........allowing the engine to instantly jump to 2000 rpm off the line and climb from there. The manual has no such benefit.

If you look at the hardware on Lance's vehicle, you'd think that it would smoke just about any other 617 out there. But, it's only in the mid 13's. This is in a lighter 240 body, with a Vnt, and a 3.46 axle ratio. A good running stock automatic with a 2.88 or a 3.07 will beat it

You are 100% correct.

NA vs NA the stick is definitely faster. But turbo vs turbo the automatic will catch up between the manual's shifts.

My primary reasons for going manual are simplicity, better control and to be different. If pure acceleration was my goal I would have used an automatic with the higher stall speed 85 torque converter.

With an automatic, you are able to stay on the throttle and keep the turbo spooled up during shifts, maintaining boost. A number of turbo enthusiasts I know in the BMW world choose automatic cars for this very reason, and one actually swapped in an automatic in place of a manual. Also, many choose lower numerical gears to stay in a particular gear longer and thus keep the turbo spooled longer.

Got some data for these?

I would think the torque converter would allow the automatic to jump up to it's peak torque much faster due to the t/c. Furthermore, the t/c allows the engine to offer higher torque for any given road speed.

Does the comparison include the same diff ratio for the two vehicles?

A 240D's 0-60 is 3 seconds faster with the manual.

The auto can power brake, the manual can clutch dump. Both can cheat a few tenths off their time. I'm talking about a right foot off the brake and onto the throttle acceleration. No playing footsie with the throttle and brake.

Yes. The 240D uses a 3.69 no matter the tranny and the euro 4-speed 300D uses the same 3.46 as the nonturbo 300D automatic.

That's quite interesting as well. Clearly, the auto loses too much in the transmission........despite the torque improvement.

Do any tests of the five cylinder?

An automatic uses quite a bit of horsepower in its operation. If you have a powerful engint this becomes insignificant, with a small engine like a 240 it is very significant and cuts the power available to accerate the vehicle to a noticable degree.

There are many different situations you could use to test quickness including acceleration and decelleration as you would do in an autocross, too. That type of situation I would expect the stick to do better than the automatic.

But in the end the real reason to convert these old cars to stick is for economy of operation.

Tom W

I'm thinking that the power loss in the automatic is not directly proportional to the engine power. As an example, a 62 hp engine might lose 15 hp to the transmission. However, a 123 hp engine might lose 18 hp to a very similar transmission. The more horsepower available..........the less the proportional loss in the transmssion.

So, where a 240D is severely restricted in acceleration with the automatic, a 617 vehicle or a six cylinder would not be in quite the same situation.

Remember, from 0-60, that torque converter provides quite a bit more output torque relative to vehicle speed..........hence the name.

I have an '81 manual 240D and an '82 240D automatic. Most of the time, I haven't noticed a significant acceleration difference between the two. The automatic seems to rev a bit higher than the manual in any gear - probably due to inherent slippage in the converter. Also, when pushed, the automatic revs alot higher before up-shifts, compared to how I prefer to shift the manual. Since both cars are now 26 - 27 years old, there may be other variables at work here too. The most signifiant difference I've noticed is the manual car gets 3 to 5 mpg better than the automatic!

Happy Motoring, Mark

Yes, another excellent reason to convert to stick.

BTW the modern automaitcs I think probably have a lot less loss than these old ones.

Tom W