LargeOrangeFont

iTrader: (7)

I would imagine the FD Torsen is on the low end of the bias ratio spectrum.

Lots of people run the T-2R, just not the RX7 guys. It is $200 more than the Trutrac. The .5:1 more bias ratio is great, but the best bang for the buck is the Truetrac. I have never heard anyone with a Truetrac say, or thought to myself "Damn I need more torque bias!" My car never does the "wag" that Blue TII was talking about. My friends 2013 track pack Mustang does it sometimes though. It has a T-2 in it.

If you want the "best" helical diff that is tunable, you want a Wavetrac. They are $900 I believe, and they are beautiful. Billet everything, all ARP fasteners etc.

eage8

iTrader: (9)

Yeah... I was already well down that rabbit hole haha. Wavetracs for IRS look like they're $1200 though, and that's way too close to an OS Giken to consider I think.

One advantage of the 1.5way clutch is that it locks a bit on decel, which helps with braking. (you won't lock the inside rear going into a corner because it's semi-locked to the outside rear). I didn't notice a huge difference when swapping, but a lot of guys swear by it and say it's the major advantage of the clutch type. It's probably a bigger deal on track when turn in speeds are a lot higher. *shrug*

LargeOrangeFont

iTrader: (7)

I have seen the IRS version for $875, but it could have been mislabeled.

Yes the 1.5 way will helping under braking, but also would hurt your turn in a bit. I had some inside rear wheel lockup, but have pretty much dialed it out now. I have an adjustable prop valve for the rear brakes, which caused the problem in the first place.

j9fd3s

iTrader: (3)

i'd agree. i looked in the FD training manual, and they have the equation for the bias ratio, but don't mention what it is.

they have some graphs, and the torsen has two lines, the low bias which is about like the clutch type, and the high bias which is higher...

the torsen is also a straight line, and the viscous and clutch types are not. the clutch has a little dogleg, and the viscous has a parabolic curve

eage8

iTrader: (9)

I'd be interested in seeing that graph...

after researching it a lot more I'm probably going truetrac... Apparently when torsen got bought a while back the metallurgy when to crap and the T-2Rs don't last at all anymore...

I also decided to go 5.14s instead of 4.88s

it's 66 mph in 2nd vs. 70 mph (at 9000 rpm) but increasing the rev limiter to 9500 rpm gets me back up to 70... and I think the higher rpms lower down will make up for it.

KNONFS

iTrader: (14)

How is the setrab oil cooler working out for you?

BTW - I need to read/educate myself on diffs, I have no idea what you guys are talking about

eage8

iTrader: (9)

Oil cooler is great, but mostly due to the fan I think which is really the whole reason I did it. going flat out for 60 seconds at relatively low speeds and then sitting in a parking lot for 5-10 minutes and then doing it all over again a few times doesn't lead to well cooled oil.... the fan fixed everything.

You should buy my current diff PM me if your interested lol

KNONFS

iTrader: (14)

NICE!

Can't man, flat out broke

j9fd3s

iTrader: (3)

http://foxed.ca/rx7manual/manuals/93...highlights.pdf

eage8

iTrader: (9)

Not surprisingly there is zero interest in my diff... but I pulled the trigger anyway

stuff that's on it's way
Ronin 8.8 Kit
Explorer 3.73 LSD + inner CVs
626 Turbo outer CVs

Stuff I still need:
True Trac
5.14 gears
mustang front diff flange
diff rebuild kit
custom length 3" aluminum driveshaft

Am I missing anything LOF?

SpikeDerailed

iTrader: (7)

Your diff setup would be great and I would love the 4.33, but I have a spare diff that was setup fresh with new bearings and a Carbonetic already just waiting to go in.

Interested to hear the results on how the 5.14 changed the car.

archaphil

iTrader: (1)

I would be all over your diff if I was not in progress of switching companies and keeping close watch on my emergency funds. I really would like to get into grip driving more.

LargeOrangeFont

iTrader: (7)

Part number for the small Mustang Flange is E9SZ-4851-A
Ford 12 pt driveshaft bolt 4 pack part number is N800594-S100
Get a Ratech solid pinion spacer for 8.8 to replace the crush sleeve when you rebuild the diff.
And you will need a Home Depot racing diff breather

Are you going to solid mount the front of the diff? I locked mine down because I have solid rear diff mounts

Drivetrain America has the cheapest price on the Truetrac typically. Call Summit directly, and send the guy you talk to this link. They will match the price and you will get free shipping from them.
http://www.drivetrainamerica.com/p-3...31-spline.aspx

LargeOrangeFont

iTrader: (7)

Also, when will you be swapping the engine? The car did 401/401 on the third pull.

eage8

iTrader: (9)

I'll probably just get a Ratech 3028K deluxe rebuild kit. Looks like that's the right one (IRS) and comes with the solid pinion spacer and shims.

I was planning on just buying another set of mazdaspeed rubber mounts for the back of the diff.

I haven't seen a very comprehensive post of what you did with your breather. link?

don't tempt me the v8... it'll be a hard decision if I even blow up my current engine again...

LargeOrangeFont

iTrader: (7)

That kit does not have the solid pinion spacer, it just has a crush sleeve. The axle seals in that kit are for a cobra style diff and won't work for the Explorer. It does have the needle bearings, but those rarely if ever go bad. A standard rebuild kit is about $70 shipped. If you need new axles seals (you probably won't) get them from the ford dealer.

eage8

iTrader: (9)

damn... you're right... I was looking at some of the other 8.8 kits and they did.

305K it is + a 4105 pinion spacer.

LargeOrangeFont

iTrader: (7)

I went a little overboard and used 3/8 tubing and a catch can. 1/4 in tubing will work fine. I drilled and tapped the cover for 1/4 NPT and used a 1/4 NPT to 3/8 90 degree barb. I ran the vent from the diff to a go kart catch can mounted in the back of the car. You could just run some tubing to a sintered bronze filter under the car and be done. Just don't leave it open at the diff cover, you will lose diff fluid out of the vent as you drive.

The catch can I used is here: https://www.amazon.com/dp/B00DPX6I9Q..._uoXsub0N4BZZ5

BLUE TII

iTrader: (9)

Also, when will you be swapping the engine? The car did 401/401 on the third pull.

He just needs the right turbo.

Here is my 13B FC dyno.

BLUE TII

iTrader: (9)

Not that I am against V8 swaps.

Looks like I have the chance to buy my friends totaled LS2 GTO. I am having trouble deciding on whether to put the LS2 in my FD RX-7 or RX-8 though...

Leaning toward the 8 since my FCs turbo setup will fit in the FD but not the 8. Plus the 13B setup is ~200Lbs lighter than the LS2 setup and I do like the FD more so it would be a shame if the 8 was faster.

LargeOrangeFont

iTrader: (7)

That curve looks good!

The 8 is a much harder V8 swap than the FD. An LS2 swap is only 50-75 lbs more than a 13b with a turbo/intercooler etc. Most of that weight is the trans. If you are talking about a non turbo 13b you are probably pretty close to that 200 lb difference with the NA trans. ZDan weighed his car before and after and it was almost a wash in his FD.

valley

iTrader: (1)

Fully dressed 13bt is ~120lbs lighter than a fully dressed ls1. IIRC, the ls2 is only 5-10lbs lighter than the ls1. People who do swaps do more than pull an engine and put another one in which is why people looking for facts go by part weight as opposed to "final" weight; anything you can do to make a swap lighter can be done to the original car.

LargeOrangeFont

iTrader: (7)

The final weight and weight balance is all that really matters. A fully dressed twin turbo 13b from an FD weighs around 390 lbs. An LS1 out of a crate is around 430 lbs with cast manifolds and a steel flywheel.

It may be close to that 200 lb difference for a stock 13bt in an FC, but after modifying the 13bt with larger turbo, intercooler, etc. the weight is much closer. Everyone's modified cars are a bit different. Keep in mind most everyone's car (FC or FD) keeps a near 50/50 weight balance after the swap if they keep the LS engine NA. Pretty much everyone moves their battery to the middle or back of the car, but that is about it as far as taking significant weight off of the front of the car. I moved my battery and run a lighter one in the bin area, and removed unnecessary wires from the chassis harness.

I did not notice much difference in handling after the swap. The car is still very well balanced, and now is brutally quick. It is nice to be able to run 91 octane fuel, and not have to worry much about engine temps on the track.

BLUE TII

iTrader: (9)

The 13BT from my dyno is ~300lbs.

Stock 2nd gen 13BT was 370lbs and everything on mine is lighter than stock and much taken off.

For example, stock 2nd gen 13B NA is 340lbs- 13B race weight 233lbs.

Full dressed 13BREW is actually 425lbs and LS2 is 490lbs and then the beefier T56 weighs a bit more than the Mazda Rtypes.

It is however, much easier to take weight off the 13BREW than the LS2.

BLUE TII

iTrader: (9)

The final weight and weight balance is all that really matters.

Yes.
200lbs more weight isn't the end of the world and actually I would probably like more weight up front in the FC that motor is in. That 2500lb full interior car has 52% rear weight bias on the corner scales with the 13B and it feels like a mid engine car- I hate it.

Front end is light on turn in and when you are on the gas its just all understeer as you have one tire kinda on the ground and the other in the air.

I affectionately called the FC my "overpowered **** box" before the new turbo and after the new turbo I am finally convinced its time to part it out.

So, LS2 in FD because its easier and is only ~70lbs more than the 13BREW I raced with so it will handle about the same (which is a good thing).

13BT EFR 7670 in the 8 because it *just* needs new manifold/dp/lines and weighs the same as the 13BMSP in the car so will handle about the same (which is a great thing).

That sounds like a good plan. I am seriously having a hard time deciding which to LS swap.