Dinan 4.10 LSD

[lucid]

Originally Posted by b16r1ch

Hmmm...

You are not gaining any more power with gearing, you are simply 'moving' the RPM band to the left (referring to a dyno graph).

So, in a drag race moving to a 4.10 should will improve your 60' but reduce your trap speed. On a road course, you will be able to accelerate 'quicker' out of slow/throwaway turns but ultimately 'slower' in an extended straight. Of course, this depends on the track...i.e. short gearing should help in shorter technical courses between and hurt in longer high-speed courses.

Again, to each their own. I still think there are better ways to spend $3k to reduce lap/track times...i.e. reducing rotational unsprung weight and increasing overall grip.
-Rich

I am not sure what you mean by moving the rpm band to the left. It is true that the 4.10 preserves the gear spacing. What I would really like is a slightly shorter 3rd gear so that the 2-3 spacing is changed, and you drop fewer rpms during that shift and stay more to the right side of the dyno graph. Anyway, I agree that there are probably better ways to spend the money, and that track wheel/tires are a more attractive option.

[b16r1ch]

Originally Posted by lucid

I am not sure what you mean by moving the rpm band to the left. It is true that the 4.10 preserves the gear spacing. What I would really like is a slightly shorter 3rd gear so that the 2-3 spacing is changed, and you drop fewer rpms during that shift and stay more to the right side of the dyno graph. Anyway, I agree that there are probably better ways to spend the money, and that track wheel/tires are a more attractive option.

Basically saying that you are not adding power, just getting to it sooner...so, figuratively speaking, it's like shifting the powercurve to the left on a HP/TQ to RPM graph.

-Rich

[Sticky]

Originally Posted by b16r1ch

Hmmm...

You are not gaining any more power with gearing, you are simply 'moving' the RPM band to the left (referring to a dyno graph).

So, in a drag race moving to a 4.10 should will improve your 60' but reduce your trap speed. On a road course, you will be able to accelerate 'quicker' out of slow/throwaway turns but ultimately 'slower' in an extended straight. Of course, this depends on the track...i.e. short gearing should help in shorter technical courses between and hurt in longer high-speed courses.

Again, to each their own. I still think there are better ways to spend $3k to reduce lap/track times...i.e. reducing rotational unsprung weight and increasing overall grip.

-Rich

Trap speed is NOT reduced. 60 foot improvement comes with traction not necessarily gearing. You would be putting more torque down earlier.

[Sticky]

Originally Posted by lucid

And what does that say exactly? That the modified final drive is slightly faster? Isn't that what I've been saying all along? Was the stock car blown away? No. And it was a short race. Let them go at it longer so that the gear change issues kick in. Not that these street racing videos ever prove anything one way or the other.



What does the above statement supposed to mean exactly? What is your point?



So, tell me where "the" power band, as you state it, starts and ends exactly? Give me specific rpm values and tell me why those numbers and not others. (as if the engine is not making power elsewhere)



What is "not upsetting the balance of the car" if not what I said by losing traction and the back end because of getting on the throttle too early out of a turn? This is the first that is taught at any driving school. Of course you can go WOT after you feel its safe to do so, but that usually means you've straightened out considerably after a tight turn. It's a different story if you are in a miata though. Then you can mash it all you want since the thing has very high traction/power ratio on track rubber.

What I am saying is 13% change in final drive will not result in 13% average acceleration during the 1/4 mile, as calculated by trap speed/1/4 time (delta velocity/delta time). If what you are saying about "always 13% more torque at the wheels" was true, it would have to lead to 13% higher average acceleration, but it won't. I told you why, but you are avoiding the issue.

I agree the car will feel liverlier during regular driving though. In that case, one is operating the engine in a limited vehicle speed range, and what happens after you shift is not a major consideration.

So what exactly is your issue? Are you just typing for the sake of typing or what?

The bottom line, the car IS faster and will FEEL faster with shorter gearing.

13% torque does not equal 13% more acceleration improvement in the 1/4, don't know where or how you made that correlation.

[Sticky]

Originally Posted by lucid

OK guys, I took the time to plot wheel torque vs vehicle speed as some folks really do think that switching final drives ALWAYS gives you more torque at the wheels, which is not true, and which has been my minor contribution to this discussion. I don't know how else to illustrate that fact apart from plotting the numbers.

Your car simply will NOT accelerate faster on a, say, 0-200 km/h run by 6.5% simply because your final drive has been changed by 6.5%, and this graph illustrates why. As can be clearly seen in the graph, you are NOT always putting down 6.5% more torque at the wheels during the run. After the shifts, the modified car actually has significantly LESS torque at the wheels for a vehicle speed range (see blue line about 30% higher than the red line after the 2->3 shift).

The net result is that you will end up accelerating somewhat faster, but not by 6.5%, so it won't be what some people think. The difference is especially pronounced in the 1st gear since both cars need to go through the entire rpm range during that interval.

There are also some finer points such as when the race ends. If it were the end at 170 km/h, the stock car would have an advantage for instance since it can still stay in 3rd gear whereas the modified car needs to shift into 4th and lose its torque multiplication advantage.

This is all aside from the point that on a track, 2nd gear is used coming out of turns (never mind the fact that 1st gear is used once), and there are traction limitations which bring up the issue of how much of that torque you can actually put down without completely losing the back end. Sticky thinks I should take yet another performance driving class. I should perhaps relay that suggestion to Will Turner whose E90 M3 also seemed to be traction limited turning in second gear going up the hill I had issues with so that he can benefit from Sticky's advice as well (never mind the fact that his car had track rubber).

Attachment 195882

EDIT: The 4.01 on graph title and legend are typos. The calculations used the 4.10 ratio. I will fix that text and upload the new graph.

Not applicable to DCT and 4.10 is almost half the reduction that 3.62 for the DCT would be.

The car is faster with the shorter gears, especially the DCT which would absolutely destroy a manual with 4.10's.

This gearing discussion has happened many times over on M5board, I suggest you educate yourself on the real world difference (this is going to 3.91 which is about the same as the manual M3 would be going to 4.10): http://www.m5board.com/vbulletin/e60...k-results.html

"There is a substantial difference in the acelleration. Here are the results, using average numbers:

------------------------Stock -----------------------Dinan ----------------------Difference

60 ft. time ---------2.229 sec------------------2.225 sec----------------0.004 sec

0-60 mph ---------4.56 sec---------------------4.40 sec------------------0.16 sec

Quarter Mile -----12.78 @ 115.59 ---------12.54 @ 118.24 -------0.24 sec, 2.65 mph

50 - 110 mph-----7.86 sec---------------------7.31sec-------------------0.55 sec"

The difference on the road course is great as well, spending more time at higher revs and GETTING there faster.

[lucid]

Originally Posted by Sticky

So what exactly is your issue? Are you just typing for the sake of typing or what?

You are the one challenging what I said (as in see below quote), so ask yourself that question.

Originally Posted by Sticky

No, there will be a big advantage at all times as you are ALWAYS putting down 13% more torque (DCT 3.62).

Originally Posted by Sticky

13% torque does not equal 13% more acceleration improvement in the 1/4, don't know where or how you made that correlation.

Look, you wrote one ALWAYS gets 13% more torque at the wheels with the 4.10. And I said you are wrong, and gave you proof. Again, if what you said is true, you should get 13% faster average acceleration in the quarter mile. F=ma. If you always have 13% more force, you will have 13% more acceleration (I am not talking lay person's "acceleration time". I am talking about the real definition of acceleration as in delta v / delta t). It's a linear relationship. Period. What part of that don't you understand or are refuting? (4.10 is not 13% more by the way, it is 6.5% as the Dinan site states. Check your math.)

If you care to read what I posted, and actually think about it for minute as opposed to posting videos, you'll see that I have, from the very beginning, said the 4.10 car will be slightly faster, but not by the amount of additional reduction in the new LSD. Why is that so hard to understand?

Anyway, I don't have a problem with you, so let's cool this off and get on with the rest of the discussion.

[lucid]

Originally Posted by Sticky

"There is a substantial difference in the acelleration. Here are the results, using average numbers:

------------------------Stock -----------------------Dinan ----------------------Difference

60 ft. time ---------2.229 sec------------------2.225 sec----------------0.004 sec

0-60 mph ---------4.56 sec---------------------4.40 sec------------------0.16 sec

Quarter Mile -----12.78 @ 115.59 ---------12.54 @ 118.24 -------0.24 sec, 2.65 mph

50 - 110 mph-----7.86 sec---------------------7.31sec-------------------0.55 sec"

If these numbers are valid (how many times has he run each test and under what conditions, etc.), then for about 8% difference in the final drive, you get about %4 more average acceleration, which is in-line with what I am saying.

Originally Posted by Sticky

Not applicable to DCT and 4.10 is almost half the reduction that 3.62 for the DCT would be.

The type of analysis I posted is every bit applicable to DCT. You just need to use different numbers for the stock and modified final drives and gear ratios, that's all. The plot would look very similar, with the stock car putting down significantly more torque at certain vehicle speed ranges after the modified car shifts. Give me the stock and modified final drive ratios for DCT, and I'll plot those as well.

[lucid]

Originally Posted by PencilGeek

How are you defining wheel torque? WT = Engine Torque * Gear Ratio * Final Drive Ratio?

If so, it would have been very interesting to use my actual dyno charts for this. If you can confirm the formula above, I'll whip it together based on actual data and post later tonight.

I am using the RRI data for torque at the wheels/total reduction. I then multiply that by total reduction in each gear. So, these are all measured numbers at the wheel, and not from BMW's crank dyno chart.

[Sticky]

Originally Posted by lucid

If these numbers are valid (how many times has he run each test and under what conditions, etc.), then for about 8% difference in the final drive, you get about %4 more average acceleration, which is in-line with what I am saying.



The type of analysis I posted is every bit applicable to DCT. You just need to use different numbers for the stock and modified final drives and gear ratios, that's all. The plot would look very similar, with the stock car putting down significantly more torque at certain vehicle speed ranges after the modified car shifts.

How do you take into account the shift speed of the DCT in the graph? Does not seem that you do.

[Sticky]

Originally Posted by lucid

You are the one challenging what I said (as in see below quote), so ask yourself that question.





Look, you wrote one ALWAYS gets 13% more torque at the wheels with the 4.10. And I said you are wrong, and gave you proof. Again, if what you said is true, you should get 13% faster average acceleration in the quarter mile. F=ma. If you always have 13% more force, you will have 13% more acceleration (I am not talking lay person's "acceleration time". I am talking about the real definition of acceleration as in delta v / delta t). It's a linear relationship. Period. What part of that don't you understand or are refuting? (4.10 is not 13% more by the way, it is 6.5% as the Dinan site states. Check your math.)

If you care to read what I posted, and actually think about it for minute as opposed to posting videos, you'll see that I have, from the very beginning, said the 4.10 car will be slightly faster, but not by the amount of additional reduction in the new LSD. Why is that so hard to understand?

Anyway, I don't have a problem with you, so let's cool this off and get on with the rest of the discussion.

In parenthesis I put 3.62 referring to 13%, YOU wrote 4.10, check yourself.

The shorter gearing is a constant, its multiplication is always higher. Once you start taking into account other variables, speed, shifts, etc, it naturally changes.

[lucid]

Originally Posted by Sticky

How do you take into account the shift speed of the DCT in the graph? Does not seem that you do.

I haven't accounted for the shift time since it will be the same delay for both the stock and the modified 6MT, which is what the plot compares.

[lucid]

Originally Posted by Sticky

In parenthesis I put 3.62 referring to 13%, YOU wrote 4.10, check yourself.

The shorter gearing is a constant, its multiplication is always higher. Once you start taking into account other variables, speed, shifts, etc, it naturally changes.

So, I am not sure what the comparison in your mind is. Do you want to compare stock DCT vs modified DCT, or stock 6MT vs modified DCT, or some other permutation. Anyway, I don't know what the stock final drive on DCT is, but I will find out. Just tell me what the modified final drive for DCT would be.

You have to take the vehicle speed into account when doing any type of comparison of this nature. That is the key issue here, which is a secondary variable that you cannot mess with directly. The modified car needs to go through the entire speed range as it accelerates. It can't skip the speeds where it has lost the multiplication advantage of the lower gear after shifting and is putting down less torque than the stock car.

[Sticky]

Originally Posted by lucid

So, I am not sure what the comparison in your mind is. Do you want to compare stock DCT vs modified DCT, or stock 6MT vs modified DCT, or some other permutation. Anyway, I don't know what the stock final drive on DCT is, but I will find out. Just tell me what the modified final drive for DCT would be.

You have to take the vehicle speed into account when doing any type of comparison of this nature. That is the key issue here, which is a secondary variable that you cannot mess with directly. The modified car needs to go through the entire speed range as it accelerates. It can't skip the speeds where it has lost the multiplication advantage of the lower gear after shifting and is putting down less torque than the stock car.

I am looking at it from the DCT perspective as my car is DCT.

The DCT is 3.15, going to 3.62 is ~13% reduction. It would make a very noticeable change in the car.

There are many variables to take into account, you can go as far as temperature and humidity but I think dealing in the relatively simple terms of the % reduction and the new max speed in each gear is a good start.

[mixja]

I agree with lucid - shorter gearing doesn't necessarily mean a car is going to be faster, depends on the nature of what you are doing with the car...

In a drag race, shorter gearing can decrease your quarter mile time, especially if you need an extra gear change. On the other hand, if your gearing is such that you're just about to hit redline in the same gear vs a 1000RPM off redline in the same gear with longer gearing, you'll probably get a faster quarter mile time. The off the line advantage of shorter gearing won't be apparent due to traction issues...

[lucid]

Originally Posted by Sticky

I am looking at it from the DCT perspective as my car is DCT.

The DCT is 3.15, going to 3.62 is ~13% reduction. It would make a very noticeable change in the car.

OK. I'll run those numbers and post that plot tomorrow.

[rzm3]

hey lucid you mind uploading your excel file? i would like to do some calcs as well. thanks!

[bigjae1976]

I emailed Dan @ diffsonline.com and he said the M5/6 and the E46 M3 rear will not fit the E9x M3. Bummer.

[BarryC]

I see all the back and forth regarding the impact of a change in FDR which is all well and good.... But does anyone know where/how to get a 3.62 for a DCT car?

Thx,
BC

[lucid]

Originally Posted by PencilGeek

I'll also re-run the 6MT based on actual dyno results, and post it. I'll also provide the spreadsheet.

In fact, I'll do four graphs for you guys:
1) Stock 91 octane, 6MT, 3.85 vs. 4.10
2) Current dyno, 6MT, 3.85 vs. 4.10
1) Stock 91 octane, DCT, 3.15 vs. 3.62
2) Current dyno, 6MT, 3.15vs. 3.62

1 is what I already plotted. I thought your dyno numbers were very much in-line with the RRI measured numbers, which is what I used?

[Sticky]

Originally Posted by BarryC

I see all the back and forth regarding the impact of a change in FDR which is all well and good.... But does anyone know where/how to get a 3.62 for a DCT car?

Thx,
BC

It is an OEM ring and pinion, not hard to find.

The question becomes if the OEM ring and pinion can be put in the E92 M3 diff or if it is possible to simply put a stock M5/M6 diff in place.

[Sticky]

Originally Posted by bigjae1976

I emailed Dan @ diffsonline.com and he said the M5/6 and the E46 M3 rear will not fit the E9x M3. Bummer.

Ask him the if the ring and pinion will fit the E92 diff housing.

[b16r1ch]

Cool...your graphs illustrate what I was talking about...power isn't affected, just 'shifted'. In this case the shift is 'up', given your plotting MPH to RPM.

-Rich