FI+ shorter final drive

[M23]

It all depends..drag racing, or road racing. If the latter, which track and what are its' characteristics (a huge track with a lot of long sweepers, straights, or a track with more technical, tighter and closely consecutive turns). Nurburgring or Tsukuba? Drag Racing or Autocross? One size doesn't fit all is the point I am trying to make.

[AJPG]

Originally Posted by Dipstik-sportech

Well I proved my point on my own car so.........

I do agree that your cars if fast, with decent amount of whp and decreasing the FD is a good move for MT, specially if turbo.

Originally Posted by Poodles

If you're letting off the gas, you're limiting power and it's essentially pointless that you've added that power. What you're wanting is a close ratio gearset (though our 6 speed is a single overdrive unit and already a close ratio because of this), not a higher ratio final drive that will effectively make lower gears worthless.

Respectfully disagree; increasing the FD not necessary will make lower gear worthless. This car is a drift monkey and that increase in FD do help for drift, drama "on the street" or fun on the back roads.


Depends on the type of forced induction. Turbos work on load, and if you're gearing is too short, you won't build enough boost AND you'll be shifting too much and losing said boost, ultimately making you slower.


Here I agree completely, IMHO decreasing the FD should work better on MT, but an AT with centrifugal SC... Well the increase in FD is a must.



Comparing to hotrods is a moot point as our stock ratio is already the type of ratios they would run back in the day. Running a 4.56 was for rock crawling.

Again it depends on the trany ratios and they are wider on the AT. To compare MT with AT we should change the FD to close those gaps and make it "similar" no equal.


Correct, you just left out the need for a load to build boost on a turbo car

Agree


Shots fired![/quote]

[mrk1]

Originally Posted by Poodles

If you're letting off the gas, you're limiting power and it's essentially pointless that you've added that power. What you're wanting is a close ratio gearset (though our 6 speed is a single overdrive unit and already a close ratio because of this), not a higher ratio final drive that will effectively make lower gears worthless.

Comparing to hotrods is a moot point as our stock ratio is already the type of ratios they would run back in the day. Running a 4.56 was for rock crawling.

Correct, you just left out the need for a load to build boost on a turbo car

Shots fired!

Yup close ratio gear set would be sweet but as far as I know there aren't any available. That cusco kit only changes 1st and 2nd, not really worth opening a trans for that. So changing the FD makes more sense, I just like the sense of urgency and "punchy-ness" higher FD's give. I raised the FD on my last M3 and it was the greatest thing ever.

You really cant compare FD ratios from one car to another. Sure they are generally in the same ball park but its all relative to the gears in the transmission and also tire size has a massive effect. Hot rodders run those real tall slicks and rock crawlers use huge tires both of which counteract FD raises. Using my 04 M3 for example a 4.10 is as high as you would want to go on a street car. Jump back to the 90's era M3 and with that car 3.46 is as high as you want. It has to do with the ratios of the trans gears too. Go even farther back to the 80's and those M3's came with 4.10's.

[mrk1]

Originally Posted by HUNTERANGEL121

I believe this is my first thread...

Anyway, had the idea for a while now,what if you were to install say a 4.44FD along with some form of forced induction making around 280whp?

Overkill, wheelspin? What do you all think

Just wantes to bring this back up as my car is up and running now. I have a 4.44 diff and a 28RS turbo. I wouldn't call it spin city, maybe on stocks tires, im on 255 RE11's. However the car is rowdy and a blast to drive around back roads.

[DustinS]

Really glad you updated this. Looking forward to do the install on mine in a few months. I want to get the turbo kit squared away first (and tires)

[liquidsky44]

My car used to do a 5.5 seconds from 0-100kph with the 4.1 final drive, but after changing to Revolution 4.8 final drive the 0-100kph drop to 7.6 seconds. This modification was done at the same time with my new wheels. Wheels spec is 18 x 9" and tire is 245 40 18 Michelin PSS. I'm also running the avo kit on my automatic. Do I need a retune or remove the 4.8 final drive and install the original one back?

[jefri91]

Originally Posted by liquidsky44

My car used to do a 5.5 seconds from 0-100kph with the 4.1 final drive, but after changing to Revolution 4.8 final drive the 0-100kph drop to 7.6 seconds. This modification was done at the same time with my new wheels. Wheels spec is 18 x 9" and tire is 245 40 18 Michelin PSS. I'm also running the avo kit on my automatic. Do I need a retune or remove the 4.8 final drive and install the original one back?

What did you end up doing? Was thinking going 4.88 then supercharger but if it doesnt help with the autos then I might put it off

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[StraightOuttaCanadaEh]

Just remember the 2017 gen cars have shorter gearing already

[liquidsky44]

Originally Posted by jefri91

What did you end up doing? Was thinking going 4.88 then supercharger but if it doesnt help with the autos then I might put it off

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Updates:

With a new tune car was back to normal with the 0-100kph time of an average around 5.5s like the 4.1FD. Just like someone mentioned earlier in the thread that turbos need time to build boost. And with a few tweaks and adjustments the car is back to normal and performed great on short distance tracks.

[jefri91]

Originally Posted by liquidsky44

Updates:

With a new tune car was back to normal with the 0-100kph time of an average around 5.5s like the 4.1FD. Just like someone mentioned earlier in the thread that turbos need time to build boost. And with a few tweaks and adjustments the car is back to normal and performed great on short distance tracks.

ah so did you end up removing the FD or just some tuning helped to work with it better? Would you have stayed with the final drive if you had a choice or just straight to turbo? sorry for the list of questions, I've got an automatic and planning to go turbo after finding stage 2 tune wasn't enough for me and was wondering about final drive since it's way cheaper to go that route. I don't care about going over 120km/h just want the acceleration to be nuts from 0-120km range which includes daily driving on normal roads and highways.

[liquidsky44]

Originally Posted by jefri91

ah so did you end up removing the FD or just some tuning helped to work with it better? Would you have stayed with the final drive if you had a choice or just straight to turbo? sorry for the list of questions, I've got an automatic and planning to go turbo after finding stage 2 tune wasn't enough for me and was wondering about final drive since it's way cheaper to go that route. I don't care about going over 120km/h just want the acceleration to be nuts from 0-120km range which includes daily driving on normal roads and highways.

I stayed with the 4.88 FD but retuned the car. I'm still contemplating if I should remove it until now. Let's say if you have plans to upgrade your turbo or rebuild your motor I think you will need to go back to the oem 4.1. With a larger turbo and higher boost I think you would need to stay in gear longer to build up the boost and unleash the full potential of the turbo itself.