R200 4.11 and a L28et

[logan1]

Well i went through a lot of trouble to get myself and R200 4.11 out of a 1986 200sx Turbo car.

My intent was to eventually swap in a L28et motor and a BW T5 trans into my 240z in lieu of the existing L24 and 4 speed. However now i am told that a 4.11 rear end is not ideal for a turbo motor as my RPM's would be too low for the Turbo to kick in. If this is true then why did Nissan fit the 200sx Turbo car with a 4.11 R200 from the factory?

[dexter72]

I think the problem is not that the rpms would be to low, its more along the lines of you won't be in a low gear long enough for the turbo to spool up nicely. Thats the issue I had and some others have had depending on which trans people are using with a 3.90 or 4.11 rear diff. First gear was almost useless, I was shifting out of it so quick it was unreal. When in 3rd gear it was great. I had a turbo on my n/a engine, late model 5spd and a 3.90 diff. When I switched to a 3.54 turbo diff, First and second gear power was a ton better because I was in those gears longer. There should be a lot of info on this in the archives. I bet you can find a combo that you will be more than happy with, so you won't have to keep swapping parts.

 

Also the turbo on a 200sx is smaller the last time i remember seeing one.

Edited February 18, 2011 by dexter72

[nagaz]

Logan, if you decide to sell your R 200 please let me know !

Thanks!

[Hybrid240z]

Along the lines of what dexter stated, 3.54 or 3.7 gearing would be more ideal for the the datsun tranny gearing in a turbo application. For the 200SX turbo, I bet the gearing of the tranny in that car was more suited for the 4.11 gearing.

[B00STDZ]

Well i went through a lot of trouble to get myself and R200 4.11 out of a 1986 200sx Turbo car.

My intent was to eventually swap in a L28et motor and a BW T5 trans into my 240z in lieu of the existing L24 and 4 speed. However now i am told that a 4.11 rear end is not ideal for a turbo motor as my RPM's would be too low for the Turbo to kick in. If this is true then why did Nissan fit the 200sx Turbo car with a 4.11 R200 from the factory?

Alot of mis information going around in this thread!

 

Higher ratio(lower numbers) is better for the l28et. Switching to this lengthens the time between gears, allows you to reach a higher top speed, and allows you to stay in boost longer/ also allows you to build full boost in 1st gear.

 

Lower ratio(Higher numbers) such as the 4.11 ARE NOT ideal for an L28et!! Using a 4.11 gear ratio SHORTENS the time between gears, redlines TOO FAST, the l28et DOES NOT spool full boost in 1st gear with this differential! and allows for LESS top end and poor gas mileage.

 

 

Lower ratio/higher number diff ratios are ideal for Naturally Aspirated motors, NOT turbo motors of any kind! Even my z32 has a 4.11 and i hate it because when i mash the gas pedal to the floor on take off the max boost it can spool in 1st gear is 7 PSI!!! only 7 when the boost controller is set at 15 and the car is able to hit 15 in all of the other gears.

 

 

Also lower ratio diffs spin the driveshaft FASTER. Is this good? If you can keep the power on the pavement! If your breaking traction in boost and you have a really wide good set of tires your diff gear is way too tall. Do you want to go fast or slide around the road?

 

I have always viewed Lower ratio/higher number differential gear ratios as a way to make a LOW HORSEPOWER car SEEM fast. Which it does wake up a low horsepower car, but if your planning on putting some power down 300+whp, go with a taller gear unless you plan on buying really tall wide drag slicks to run on it.

 

Basically higher ratio/lower numbers is better in a sense, if the car seems sluggish with the diff gear most likely the gear is too tall. But too be honest this isnt very common.

 

The most desired ratio for a l28et is the infamous 3.36 r200. 3.54 will suffice. 3.7 lsd if you are on a budget and dont want to mess with the ratios and have an lsd.

 

I have a 300zx z31 3.7 ratio r200 lsd that has been converted to a 3.36 LSD in my orange car.

[bradyzq]

A little devil's advocate here:

 

The diff ratio is a torque multiplier. And driveshaft speed divider. Period.

 

If you're spinning through first and second no matter what the diff ratio, does it really matter how much boost you're making?

 

And might it not be nice to have extra torque in the gears you have some semblance of traction in?

 

And the "ideal" (is that the same as "best"?) ratio will also vary based on the turbo's boost threshold.

 

For example, if you have a huge turbo that normally spools around 5000RPM, wouldn't you rather have more effectively normally aspirated acceleration in the lower gears, as opposed to having a ridiculously long (and slow until boost hits) first gear?

 

EDIT: And don't forget about the transmission ratios. They can change the outcome of the ballgame too.

 

So, think in terms of overall ratios, not just diff ratios.

Edited February 18, 2011 by bradyzq

[JMortensen]

Just wondering why you guys aren't just starting in 2nd gear. There is potentially an argument to be made for the 4.11 if it got you through the 1/4 mile at an advantageous rpm, or if it worked out better for a road course or autox or something like that. But if the argument is that you can't build boost in 1st, put it in 2nd seems a simple solution. In general though I agree that a taller diff works better for cars with a wide power band, and short gears work better for a car that has to stay in a narrow power band.

[B00STDZ]

See the way I see it if the turbo spools at 5000 rpms. higher ratio/lower numbers would be better because say your redline at 6000

 

Alright your in 1st gear. high ratio rear end. say at 5000 when the turbo spools you hit... 20 mph... and by 6000 your at 35 mph...

 

Same turbos/tranny/setup

Low ratio rear end. say at 5000 when the turbo spools you hit... 15 mph... and by 6000 your at 20mph because the engine winds too fast not allowing it to build full boost.

 

 

So the bigger the turbo the more essential it would be TO have a high ratio! You want to MAXIMIZE your time in boost. say with a 3.36 between 5000-6000 you spend 1.2 seconds in boost building up more speed. with a 4.11 between 5000-6000 you spend probable only .5 seconds in boost, not building boost completely, and not aquiring as much speed.

 

This is just gearing. If you have a 4.11 and you have that big of a turbo pushing that much power. Not only will you spend LESS time in boost, NOT build full boost, and NOT aquire as much speed, But traction, If boost hits like a hammer and is a quick spirt most likely youll be spending more time sliding around than going forward.

 

 

 

 

With a NATURALLY ASPIRATED car that seems sluggish with TALL drag slicks, you should probably run a lower ratio/higher numbers in your differential to push the traction threshold to aquire the best time possible.

[logan1]

Considering all the information above and the fact that i already have the BW T5 and the 4.11 R200. I'll see how the trans and diff combo feels with my L24(mild racing cam) and looking into building a high compression L28 since i already have an excellent E31 head on my L24.

 

Once again thanx a bunch for all the help.

[bradyzq]

Sorry, but speaking of misinformation, there is some in your post:

 

See the way I see it if the turbo spools at 5000 rpms. higher ratio/lower numbers would be better because say your redline at 6000

 

Alright your in 1st gear. high ratio rear end. say at 5000 when the turbo spools you hit... 20 mph... and by 6000 your at 35 mph...

 

 

If you're going 20mph at 5000RPM, you're going 24mph at 6000RPM in the same gear, wheelspin notwithstanding. No two ways about it.

 

Same turbos/tranny/setup

Low ratio rear end. say at 5000 when the turbo spools you hit... 15 mph... and by 6000 your at 20mph because the engine winds too fast not allowing it to build full boost.

 

Same here, 15mph @5000 = 18mph@6000. Actual numbers for a 4.11:1 diff and a T5 or Z 4-speed are about double these numbers.

 

 

So the bigger the turbo the more essential it would be TO have a high ratio! You want to MAXIMIZE your time in boost. say with a 3.36 between 5000-6000 you spend 1.2 seconds in boost building up more speed. with a 4.11 between 5000-6000 you spend probable only .5 seconds in boost, not building boost completely, and not aquiring as much speed.

 

What you've just described here is the car with the 4.11:1 diff accelerating MUCH harder than the car with the 3.36:1 diff. If it goes from 5k to 6k in less than half the time with a diff ratio less than 25% higher, it's accelerating, or "acquiring speed," harder, way harder.

 

This is just gearing. If you have a 4.11 and you have that big of a turbo pushing that much power. Not only will you spend LESS time in boost, NOT build full boost, and NOT aquire as much speed, But traction, If boost hits like a hammer and is a quick spirt most likely youll be spending more time sliding around than going forward.

 

With a NATURALLY ASPIRATED car that seems sluggish with TALL drag slicks, you should probably run a lower ratio/higher numbers in your differential to push the traction threshold to aquire the best time possible.

 

Assuming straightline acceleration, I don't want to spend MORE time doing anything. Which car would you rather have, the one that spends 9 seconds in boost on a 10second 1/4 mile pass, or the one that spends 13 seconds in boost on a 14 second pass?

 

The difference in torque (which is effectively acceleration) between 3.36:1 diff and a 4.11:1 diff is 22%, as in you get 22% more torque to the ground in any given gear with the 4.11:1 diff. If you can break a car with the 3.36:1 diff loose, well, of course, with 22% more available torque, you'll do the same with the 4.11:1 equipped car too. I'm simply saying that depending on the turbo/overall setup/intended use, one shouldn't dismiss the 4.11:1 diff outright.