brillo

The kind folks at Mazmart are going to be offering a 4.10 rear end soon for our RX8's to replace the stock 4.44.

Paul indicated that they would ship a full differential (with the new gear installed) and you would send your core back to Mazmart. This is nice, as I'm not sure I want to go messing inside the differential. Price is not set yet, but keep in mind the work that they are doing with the price.

I thought it would be interesting to discuss the advantages / disadvantages of this swap. Obviously, the biggest advantage in my mind would be better gas mileage (especially at hwy speeds). I figure that the 4.10 gearing would make driving at 70mph be the equivalent of driving at 65mph in terms of RPM's, which netted me almost 2-3mpg more. As for city driving, I'm guesing another 1 mpg or so, but I don't think it would be as noticable

As far as disadvantages, obviously, acceleration would suffer slightly, the question is how much. I'm guessing our 5.8 0-60mph would rise to 6.1-6.2 ?Anyone have a calculator for this?

Discuss

Moostafa29

That might be a nice option for the forced induction folks out there. The added mpg would probably offset that which we lose with a turbo/sc. The N/A people would suffer horribly trying to accelerate, but if you don't really push it much, it might be nice. I'd be interested pending pricing, but more than likely I'll stay where I am. Great news though, looks like our aftermarket is finally starting to pick up.

Nemesis8

iTrader: (3)

I would rather have a taller 6th gear in the tranny

A "taller" gear, meaning that the rate of increase in engine speed vs vehicle velocity is higher than a "shorter" gear. The result is that the taller gear will pull harder, but will reach maximum engine RPM at a lower output shaft (wheel) RPM than a shorter gear. Neither is better or worse, taller gears accelerate better, shorter gears give you a better top end speed. I don't want to cruise at 145, I want to get there fast.

StealthTL

iTrader: (1)

O.K., you're confusing the hell out of me -

-first, the stock ratio is 4.444.

-second, can we agree that "taller" gears are numerically LOWER and therefore accelerate slower, given the same power input. Seems some people are a tad confused.

I would definately consider a switch to a 4.1, I would welcome the cruising rpm reduction and it would actually increase my top speed, because 6th gear is useless, and 5th redlines.

Aisin makes a set of 5.55 for the RX-7, and Feed makes a replacement '8 set at 4.7, but I haven't seen anything lower, and I like the "plug&play" aspect.

I think the speedo is gearbox based? So it would always read too low?

S

Fanman

I agree with Nemesis give me a unit with a taller 6th gear only & you have my money. Depending on the price I would not mind a 4.10 diff, even if it hurts my acceleration a bit (hell, gives me an excuse to turn up my boost a bit more).

PUR NRG

I'm in the opposite camp. Even boosted I'd prefer a shorter final gear in order to get that much more acceleration.
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brillo

sorry for the stock gearing mistake, I changed it to a 4.44.

I don't think the acceleration difference from a 4.44 to a 4.10 would be that noticable, but in fairness, my experiences with changing out final drives were with cars with alot more power.

Magic8

What if you do this and add the 17" wheels?

PUR NRG

Oh yes, definitely noticable. At a rough guess I'd say something like half a second in 0-60 times.
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r0tor

iTrader: (1)

put it on the ol simulator...

looks like .2 sec slower to 60mph, but only .1 sec slower in the 1/4 mile and actually trapping a bit higher due to still being in 3rd gear instead of shifting to forth right before the lights. However, it requires an even higher clutch dump then before to acheive those results.

also expect top speed to be down to ~149 instead of ~155 mph

rotarygod

^Those numbers are so close no one will ever know it.

Sapphonica

With the extra horsepower & torque of FI, the 4.11 would be a much diff gear.

I'll bet the 0-60 & 1/4 mi times would be lower with 4.11 than stock, since you would build some speed in 1st before shifting, reducing the 1-2 shift time penalty? As it is, 1st gear is just a stump puller when FI.

Nemesis8

iTrader: (3)

So, you need a 5-Speed??

Moostafa29

I'll take that bet.

swoope

iTrader: (5)

stock tires with turbo.

4.10 will win the 1/4 mile.

just my opinion, i could be wrong.

beers

kw1k

yeah this would be a good idea for ppl with turbo's .

I'm soon going to be ordering the FEED 4.77 gears. my gas should be fine on the normal roads. Highway its going to hurt me a bit , but thats fine!

Moostafa29

I could be wrong also, as I'm no expert in this subject. But if everyone is saying that something like the FEED 4.77 gears would aid in acceleration, I don't see how going to something below stock would aid as well. Any experts care to explain?

brillo

if its really only a 0.2 sec slower, then thats worth the mileage improvement, no one I know could tell the difference, you'd have to be at a drag strip to notice.

rx8wannahave

That's really what I would want also, or maybe a 7th gear...lol

The RX8 would have MUCH better fuel economy if our RPM's at 75mph was more like 3K instead of the 4K it is now.

But like stated, I'm glad to hear more and more mod's for the RX8...the future looks bright!

PUR NRG

One word: autocross.
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swoope

iTrader: (5)

sorry so late,

my thoughts are quicker hook up with the extra power of a turbo, and maybe one less shift in the traps.

just an educated guess buy running a na car.

beers

GeorgeH

iTrader: (2)

4.44 to 4.1 is a 7.6% change. Basically, with 4.1 gears the car will feel like it has 7.6% less torque in all gears across the rev range. I'm sure you'd feel it if you jumped from a 4.1 car to a 4.44. The other thread has a comparison between a 4.1 S2000 and a 4.5xx, and the 4.5xx car clearly pulls the 4.1 car.

QBallz

I created a quick Excel spreadsheet that shows the MPH differences at different RPMs. I stoled the formulas from somewhere let me know if they are wrong. If you like the spreadsheet and want a copy PM me with your email address.

Mazmart

iTrader: (12)

The rumors are true. We ARE working on the diff conversions. All of these units will be assembled by professor Engman whose experience exceeds all of us put together. I will make some announcements about these and other neat things shortly. Many people will be happy.
Paul.

Nemesis8

iTrader: (3)

I raise my glass to you sir