414 + 86 = 500 hp

[mPlasticDesign]

Originally Posted by PencilGeek

You will also have a 14.9% reduction in speed.

I aways thought the jump from 3.15 to 3.62 was a huge mistake. The Dinan guys were also against the idea -- except the market demanded it. The market demand was started by a contingent of enthusiests who insisted they wanted 3.62 and promised to purchase such a ratio if it were ever produced. One of the most vociferous proponents was an avid drag racing guy. I personally think he single-handedly persuaded enough people that it literally created a market for the 3.62 where no market really existed.

However, after installing his 3.62 and running at the track...he did not lower his ET. I'm not sure if he lost time on the track, but I think there's enough speculation that he did -- because one week later, he was selling his 3.62. What's the moral to the story? If you really think the 3.62 is the best bang for the buck -- think again.

Wow, intersting. I don't have DCT so the only choice I would have is the final drive ratio of 4.10 for the 6MT. What do you know about the 4.10? I thought it would give you more immediate quicker acceraltion of the line? You got me thinking now....

[Lemans_Blue_M]

Originally Posted by ///Metak

Wow, intersting. I don't have DCT so the only choice I would have is the final drive ratio of 4.10 for the 6MT. What do you know about the 4.10? I thought it would give you more immediate quicker acceraltion of the line? You got me thinking now....

It depends on your transmission gearing...

Your 6-speed manual tranny will probably benefit more from the shorter 4.10 gears, than the 7-speed DCT tranny. (the 6mt internal gear ratios work out better)

Keep in mind, that you will always lose some top end speed when you install shorter than factory spec gearing.

You will also burn slightly more fuel as a result of the switch...

[M3 Montreal]

Originally Posted by Lemans_Blue_M

It depends on your transmission gearing...

Your 6-speed manual tranny will probably benefit more from the shorter 4.10 gears, than the 7-speed DCT tranny. (the 6mt internal gear ratios work out better)

Keep in mind, that you will always lose some top end speed when you install shorter than factory spec gearing.

You will also burn slightly more fuel as a result of the switch...

How much from the top end is lost?

I cant think of any racetrack where I would need more that 250kmph as a top end before braking (at least near me) so if the top end stops around 275 thats actually not bad. I think Mosport is around 230 to 240 and thats one of the highest speed tracks around me.

[swamp2]

Originally Posted by PencilGeek

You will also have a 14.9% reduction in speed.

I aways thought the jump from 3.15 to 3.62 was a huge mistake. The Dinan guys were also against the idea -- except the market demanded it. The market demand was started by a contingent of enthusiests who insisted they wanted 3.62 and promised to purchase such a ratio if it were ever produced. One of the most vociferous proponents was an avid drag racing guy. I personally think he single-handedly persuaded enough people that it literally created a market for the 3.62 where no market really existed.

However, after installing his 3.62 and running at the track...he did not lower his ET. I'm not sure if he lost time on the track, but I think there's enough speculation that he did -- because one week later, he was selling his 3.62. What's the moral to the story? If you really think the 3.62 is the best bang for the buck -- think again.

Interesting. I did some CarTest simulation with different FD ratios and found the same thing - almost identical performance. It was puzzling but I guess there is some loose validation of this right here. Good info.

[NFDoms2k1]

Originally Posted by AMPowerJ

Everyone is forgetting 100+ octane fuel. That alone should give you about 30 hp so you could achieve your goal at the crank without FI.

+1 Didn't even think about this, with all the other mods you spoke of it should be close with high octane, but thats kind of like putting the asterik next to Bond's name unless it you have regular access to it and don't mind paying $100+ per fill-up.

[KonigsTiger]

Originally Posted by Lemans_Blue_M

Actually...that last part is wrong.

Stroked 4.6 liter S65 motors are making over 500 crank hp.

Yes, we "stroker" guys are consistently making well over 535bhp (with some ECU improvements and some other goodies) at the crank and no, I don´t believe it is possible to get to 500bhp without any major modifications either in displacement or going FI.

[mixja]

Originally Posted by swamp2

Interesting. I did some CarTest simulation with different FD ratios and found the same thing - almost identical performance. It was puzzling but I guess there is some loose validation of this right here. Good info.

The differences vary markedly depending on the scenario you try to model.

If for example you model a rolling start at 30MPH in 4th gear, the car with higher FD gets a big lead (most of it in gained in the initial 4th gear pull) that the car with lower FD can never pull back...

Based upon my modeling of this I've come up with two conclusions:

- You need fast gear changes (which DCT has)
- As power increases, the relative benefit of a higher FD decreases

I like to call the FD modification the butt dyno mod - your butt dyno tells you the car is much faster because of the increased torque to the wheels, and the transition from no acceleration to full acceleration is much more apparent. But in reality the gains in performance are only slight.

[QTRM3]

dose anyone has a dyno chart shows the torque gain for 4.1 diff..

[mPlasticDesign]

Originally Posted by QTRM3

dose anyone has a dyno chart shows the torque gain for 4.1 diff..

I have done a few online(non forum) searches, couldn't find antything. I'd be interested as well.

[D-Rock]

^^^ That cost a lot and i would like something that would be in the car not just gas...

[mixja]

Originally Posted by mixja

The differences vary markedly depending on the scenario you try to model.

If for example you model a rolling start at 30MPH in 4th gear, the car with higher FD gets a big lead (most of it in gained in the initial 4th gear pull) that the car with lower FD can never pull back...

Based upon my modeling of this I've come up with two conclusions:

- You need fast gear changes (which DCT has)
- As power increases, the relative benefit of a higher FD decreases

I like to call the FD modification the butt dyno mod - your butt dyno tells you the car is much faster because of the increased torque to the wheels, and the transition from no acceleration to full acceleration is much more apparent. But in reality the gains in performance are only slight.

The other interesting factor that adds to the perception a higher FD is much faster is that the time spent in gear is reduced by the square of the ratio between stock FD and higher FD.

E.g. for DCT 3.15 vs 3.62, the ratio is 1.149 (i.e. you get 14.9% more torque in gear). The time spent in each gear is reduced by 1.149^2 or 1.32 (in other words you spend 32% less time in gear). As a side note the distance traveled in each gear is reduced by 1.149^3 or 1.52 (i.e. you travel 52% less distance in each gear)

So basically your G forces are increased by 15% using the example of DCT 3.62 vs stock DCT, but your time in gear is reduced by 32%...this leads to the perception that the car is much faster...

:EDIT: The above is based upon the assumption of a flat torque curve

[Adonislike]

This is good info to know. Thanks Everyone for the input

[mPlasticDesign]

I am sure ther is a dimishing return going too aggressive on the FD on aftermarket LSD's at some point, I just wonder if there is a happy median?

[J08M3]

3.62 was too drastic of a change for DCT. They have another option which is less drastic and should provide more positive results.

I will be switching my 6MT from 3.85 to 4.10 though, this is about a 6% change in torque at the rear wheels. Will barley lower my top speed, which I currently never get to hit anyway. Definitely will improve my acceleration though, and will also give me a chance the keep the RPMs up just a little more which I need on a street driven vehicle.

[askiles]

Nitrous is a quick solution, without major modification, that can get you where you want.

-Andy

[Lemans_Blue_M]

Originally Posted by J08M3

3.62 was too drastic of a change for DCT. They have another option which is less drastic and should provide more positive results.

I will be switching my 6MT from 3.85 to 4.10 though, this is about a 6% change in torque at the rear wheels. Will barley lower my top speed, which I currently never get to hit anyway. Definitely will improve my acceleration though, and will also give me a chance the keep the RPMs up just a little more which I need on a street driven vehicle.

Keep in mind that you will not only lose some 'top end speed'...but you will also lose speed in each and every gear as well. (although you will gain some torque in return)

Shorter gearing is a mixed bag. There is no free lunch. For the advantages you get, there are also some disadvantages as well.

[J08M3]

Originally Posted by Lemans_Blue_M

Keep in mind that you will not only lose some 'top end speed'...but you will also lose speed in each and every gear as well. (although you will gain some torque in return)

Shorter gearing is a mixed bag. There is no free lunch. For the advantages you get, there are also some disadvantages as well.

So? That doesn't really matter, I'm looking for acceleration. If I can't go fast enough in 3rd, I can change to 4th. You only have to worry about top speed and I can afford to lose MPH there. Of course you don't want to change your FD too much or you will be forced to make additional shifts during your acceleration up to desired speed. That will cause you to lose time.

[mPlasticDesign]

Originally Posted by J08M3

So? That doesn't really matter, I'm looking for acceleration. If I can't go fast enough in 3rd, I can change to 4th. You only have to worry about top speed and I can afford to lose MPH there. Of course you don't want to change your FD too much or you will be forced to make additional shifts during your acceleration up to desired speed. That will cause you to lose time.

This is kinda what I was thinking. Seems that you would get to a given speed faster with the 4.1? So even though a stock 6MT will be in that gear longer without shifting I doesn't seem that it would'nt be enough to overcome the deficit in distance to the 4.1LSD. I think I remember PG saying that changing your tire specs to a 30 series would yield similar results? Maybe he can chime in.

[Lemans_Blue_M]

Originally Posted by J08M3

So? That doesn't really matter, I'm looking for acceleration. If I can't go fast enough in 3rd, I can change to 4th. You only have to worry about top speed and I can afford to lose MPH there. Of course you don't want to change your FD too much or you will be forced to make additional shifts during your acceleration up to desired speed. That will cause you to lose time.

Well...depending on the fixed transmission gearing (combined with the differential gear ratio you choose), you actually CAN lose time. (0-60 & 1/4 mile et)

The internal transmission gear ratios in 1st, 2nd, and 3rd gears are crucial. That will determine whether your shift points fall where you need them too in the rev band. You can't change those ratios. So you just have to properly incorporate them into your plans. The shorter the diff ratio, the quicker you need to shift. (i.e.- you have less time to react)

It can get to a point where 1st and 2nd gears are almost useless...

If your transmission gear ratios aren't working in sync with you newly selected shorter ring and pinion gear ratio...you won't improve your acceleration times much at all. And worst case..you will end up worse off than when you stared. (performance wise)

The math has to work out...or you won't accomplish anything.

[Lemans_Blue_M]

Originally Posted by ///Metak

This is kinda what I was thinking. Seems that you would get to a given speed faster with the 4.1? So even though a stock 6MT will be in that gear longer without shifting I doesn't seem that it would'nt be enough to overcome the deficit in distance to the 4.1LSD. I think I remember PG saying that changing your tire specs to a 30 series would yield similar results? Maybe he can chime in.

No, you guys are missing the point here...

The shorter gears are ramping up the torque. (a shorter gear ratio = greater torque multiplier)

You reach the maximum speed (within that gear) so fast, that you need to upshift not to hit the rev limiter in each gear. So basically, you have to shift faster (and more often) not to kill your forward momentum. You can end up having MORE shifts if you choose the wrong differential gear ratio. (3-shifts to a given speed vs. 2-shift to a given speed)

That 'extra' shift can actually slow you down if the tranny/diff gearing numbers don't jive.

[J08M3]

Originally Posted by Lemans_Blue_M

Well...depending on the fixed transmission gearing (combined with the differential gear ratio you choose), you actually CAN lose time. (0-60 & 1/4 mile et)

The internal transmission gear ratios in 1st, 2nd, and 3rd gears are crucial. That will determine whether your shift points fall where you need them too in the rev band. You can't change those ratios. So you just have to properly incorporate them into your plans. The shorter the diff ratio, the quicker you need to shift. (i.e.- you have less time to react)

It can get to a point where 1st and 2nd gears are almost useless...

If your transmission gear ratios aren't working in sync with you newly selected shorter ring and pinion gear ratio...you won't improve your acceleration times much at all. And worst case..you will end up worse off than when you stared. (performance wise)

The math has to work out...or you won't accomplish anything.

absolutely agree.... that's why the 3.62 (14% change) in DCT was a Failure.

But 4.10 (6% change) in the 6MT should not be too short.

[mPlasticDesign]

Originally Posted by J08M3

absolutely agree.... that's why the 3.62 (14% change) in DCT was a Failure.

But 4.10 (6% change) in the 6MT should not be too short.

Didn't Alex(Doba) sell his 3.62? Did he ever get his installed?