Willicuddy

5.1 gearing would be insane.

You better have a quick wrist to deal with all that shifting

Willicuddy

All this gear talk is making me feel like I'm on a Mustang forum

tiltmode43

iTrader: (15)

Only difference then will be the contact rubber, will have to run wider if you want same area of contact...

Thank you nmarz77, finally someone who understands why I'd like to see a dyno, I'm not thinking necessarily for increase but to see how it changes exactly. I'm sure given the fixed ratio vs stock this could be calculated but Im way too lazy for that

nmarz77

Yeah I think the only thing my brain wants to do right now is IMAGINE what it would look like on paper......it's screaming "NO MORE F*CKING MATH ON A FRIDAY!"

I'm gonna do some google searches to see if I can find a dyno comparison of a before and after gear change so we can get and idea of what it might look like.

staticlag

Well, the dyno in horsepower only mode (which is the dyno mode normally used for "horsepower" pulls)

Will measure inertial change in the large roller.

Even with the gear amplification the engine itself will not be able to "change" the inertia of the roller fast enough to show a torque or horsepower increase.

This is shown in the fact that dyno pulls in 3rd, 4th or 5th gear most always result in the same graph, even though each of those gears has a different "drive"

A dyno will not show change from this gear.

crimson-rain

hey staticlag, you have the RB flash also right? How come you weren't taking the RPMs into the "10000RPM" zone?

Nice vids.

tiltmode43

iTrader: (15)

Smarty pants tehe, I just assumed that because torque was coming in earlier it'd show on the torque curve.

Rotor Kreuzer

Great review! I thought it was a straight swap, and that everything required for the install would come included with the FEED gear. Guessing an AT will need all these also?

nmarz77

Ok well after a quick search I found an explination for us and a graph that show how the torque and horspower differ with the installation of a different gear. Check it out!

http://www.wallaceracing.com/reargear.htm

nmarz77

Ok here is one more link for ya. This one is really good because it explains how different performance upgrades(including gears) shift torque around. The only one that would apply to our cars though is the gearing explination.

http://clubs.hemmings.com/clubsites/...and_torque.htm

mdw1000

Just do what I did and have it sent to Mazmart. They will take care of everything else for you.

staticlag

Yes, but as I said in my post, in "horsepower only" mode the dyno will not change, that is, the engine will not produce any more torque or horsepower for any given rpm.

Now is is different than the "road simulation" mode that is discussed in these articles that graph horsepower and torque versus road speed on the x axis.

Maybe these graphs are what you are looking for in conceptualizing the change.

4.44 stock


4.77 FEED


Now, what is seen is a shrinking or shortening of the gearability of the car. By shortening the gear graphs the engines power is concentrated for any given speed. You spend more time in the sweet upper spot of the engines powerband rather than the boggy lower end.

Its just like any of the other gears in any car. Imagine the power difference between being in 3rd gear at 40mph versus being in 6th gear at 40 mph. You still have the same engine putting the same power out, but 6th gear is greatly lengthened versus 3rd gear.

This is the same thing, but only it shifts all the gears at once, making all of them stronger at any given roadspeed at given at the expense of top speed.

staticlag

Did they replace your bearings? Or did they just switch them over?

staticlag

You "can" re-use all the parts off the old piece, but they are all wear items, just like brake pads or oil or antifreeze. So while your in there its not a bad idea to give some preventative maintenance.

TimzSI

all the bullshit comments on the video forum are hillarious. Glad you're enjoying it man, seems very worth while.

nmarz77

Well I guess the confusing thing here is weather or not you are trying to measure the actual torque at the rear wheels or at the crankshaft. Dynos always correct the torque to try to get it to where it should be at the crank, so you're right, there should be no change in torque on the dyno sheet. If we measured the actual torque at the wheels though we would see HUGE numbers and big differences in torque output depending on what gears were selected. For easy example if we had a car putting out 160 lb/ft of torque at 5500rpm like mazda claims, and we were in 5th gear with a 1:1 ratio, with the stock 4.44 final drive the output torque at the wheels is actually 4.44 times 160 which makes it 710.4 lb/ft. now with your FEED 4.77 you should gain an additonal +/-7%. 160*4.77=763 lb/ft.

So you're putting down an additional 63 lb/ft of torque where the wheels touch the pavement. Sounds like a lot but when you consider you already had 710 to begin with, it's not a massive improvement. Now going through first gear would be 3.76x4.77x160=2,870 lb/ft with the FEED.

I know this has nothing to do with the dyno chart but it just looks cool on paper.

staticlag

I completely agree with you

WoodsOfGreenRx8

They are quite hilarious.

mdw1000

I actually did a core-swap with Mazmart and got a whole "new" differential. It was actually built from a used diff from another AT, but considering Rick Engman built it I consider it better than new. Plus the diff that they used was actually a bit lower mileage than my original. I'm not sure which parts are new and which are used (other than the FEED gear being new and the diff housing being used), but Mazmart has such a good rep that I wasn't really worried about it. Their quality and customer service are top notch. I have since bought a water pump from them which is a top-notch piece.

FYI - Mr. Engman did have to do some machining on the FEED gear to get it to within what he felt were good tolerances for a street car. But I can't complain - this diff is smoother than my OEM diff. And it is an LSD.

I bought the FEED gear, had it shipped to Mazmart, they built the new diff, had it shipped to me, my mechanic installed the new diff, and then i shipped the old diff to Mazmart.

Feel free to PM Paul at Mazmart about my diff build.

zaku

My car had this final drive, too. Recently I sent my ECU for knight sports swap for cancel of speed limiter, fan control and extend rev limit from 7500 to 8500rpm (sorry I had a AT one). Can I get my top speed back?

WoodsOfGreenRx8

Unless you are racing open road courses, do you actually need your top speed?

zaku

you're right. but I just want to know the effect of another 1000rpm

kersh4w

iTrader: (3)

what kind of rx8 do you drive that can hit 185?

im pretty sure rx8s top out at 148. so its not reducing it from 185 to 160ish. its putting it from 148 to about 135.

and this would also further kill gas mileage. highway speeds = higher rpm = lower mpg.

Rotary Rasp

iTrader: (2)

bout 160 stock

staticlag

This mod lowers possible top speed, not actual top speed.

By shortening the gears it puts the engine into its powerband when its 150-165 mph. So it actually will increase the cars ability to redline in 6th, in other words it makes 160mph+ easier for the car to do.