No reason really...The first bunch of dyno runs were started about 2.5K, but the last set were done from 3K upwards.

I don't know if I've ever dyno'd a rotary from idle. :)

Ive never seen any engine done from idle. They are always brought up to 3rd gear and then floored from about 2-2.5k.

So no TII parts huh. ;) Well, you're brave, ill give you that. Sounds like a big ford 9" is in your future...... ;)

don't be too stubborn. A $100 used T2 rear will be a hell of alot smarter than custom halfshafts and some Kaaz LSD stuffed into the N/A rear. I know your a smart guy, just loose the N/A idea thats burned into your head and go the cheap effective route.

It's not like you are gonna be in the Guiness Book of World Records for the fastest all N/A turbo Rx-7

I wouldn't trust an NA diff behind any serious amount of power. If you are cleanly breaking the tires loss it may last for awhile, but if you get any sort of traction or wheelhop, its likely going to eat away quickly. The only NA diffs that I have seen lasting on V8 swaps are with an automatic transmissions with relatively low power, and even then their days are numbered.

Any NA (and quite a few TIIs) that I have seen take "alot of abuse from a v8 swap" has ended up in pieces. Suit yourself if you want to try it.

:suspect:

^^ you know you want to admidt it makes more sense, but I guess Pride isnt Free

I believe Aaron's after the fact that so many people are against it.

Would a TII diff work and be stronger? Obviously, the guy's not handicapped. But can an N/A rear end take some SERIOUS power and stand up to an awful lot of abuse? He's proving that right now. All the people who tell the newbies around here "don't bother leaving your N/A rear in the car after the TII swap since it won't hold the power" are eating their words while Aaron burns around twon with 400bhp blazing through his N/A diff. Will a TII diff take more? Sure. But this is holding up quite well. And even a TII diff has its limits. Locals are busting axle cups on hard launches with slicks at Aaron's power level. So why bother going that route since it'll break anyways? (same mentality as the N/A rear to begin with....you see?)

The car is a turbo'd N/A I don't know what's so hard to understand :)

its all in how you drive the car. things break when you race. If you launch with a n/a rear and slicks something will break. Why would you race a 400hp car without slicks???

Lots of reasons. :) I ran 18" rims with 255 tires when I raced my 400hp TII. Hooked nicely actually....

back on topic...............---->

If I wanted a TII, I would have bought a TII or done the TII swap. It would have been a bit easier then what I've done so far. :)

I considered using the TII diff, but why? Most of them are high mileage, and getting to the point where they are just plain worn out (as are many of the TII transmissions as well...) anyway. If I'm going to have a diff rebuilt, why would I not just stick with the NA diff and fill it with superior aftermarket parts? Philosophically it's far more in line with with I've been doing with the car so far and it's going to be far better then a TII unit. Besides, at more then 400 HP the TII parts start to get a bit delicate as well...So the choice boils down to starting with an NA diff and having it rebuilt with new stuff, or starting with a TII diff and having it rebuilt with new stuff. No advantage either way except the fact that the NA unit is a direct bolt in. Then if the half-shafts break, I just have new direct replacements fabbed up and I'm good to go...

I've been putting big power in front of NA drivetrains for the past 7 years and have not had a single failure. :)

zbrown is launching his GT42 powered REW car on the anti-lag using an NA rear end and slicks. :D

Partly. I like to mess with people. To this day I still get at least one PM per day that says I can't turbocharge the NA. Could have fooled me... :)

Hell, when the car was NA I was doing 8K clutch dumps on slicks at the track. I broke my "unbreakable" driveshaft twice. :D

Bingo. Either way I need to fill a diff with aftermarket parts so there's no point in starting with the TII pumpkin over the NA unit.

If they hate this, they are going to despise me for my brake setup... And transmission selection when the NA unit finally dies... :D

The TII diff has a larger, and stronger 8" ring gear. The LSD unit used in the S4 TII is also nearly indestructible, they are commonly used as an upgrade for FD's torsen unit, and I have never seen or heard of one breaking, possibly because other things will break much sooner than the LSD unit can reach its limit. They can also be rebuilt if you are want to make sure its fresh and grabs hard.

Do what you want, I'm not trying to argue with you, just saying, I wouldn't want an NA diff in my car, in fact, the TII diff is on it way out as soon as I get some custom axles for my new rear made up, although, I have other reasons, besides strength to go with a different rear end.

Since you mentioned V8 swaps, it may not be a bad idea to take a few pages out of their book, a pinion snubber and/or a diff anchoring bracket will go a long way to help from tearing the front mount off the subframe. The stub shafts and ring gear will then be the most likely things to break. Stub shafts are fairly random, but you'll likely take a few teeth out of the ring gear before it comes completely apart, so just listen for it howling.

Then you know no people who run real power :lol: I've personally watched 3 S4 TII diff's give up the ghost at Toronto Motorsports park. One of them in a pretty spectacular manor @ half track.....and I'm not there very regularly either.

Read above statement :) And if you don't believe me, come up to the track and ask the prep team who had to scour the around for 20 minutes picking up/sweeping chunks of ring gear :rofl:

Damnm, that much power in a turboed n/a. I went the opposite way with a tii drivetrain and n/a rotors. So far its doing awesome at 19 psi on pump gas (93 though). But yours looks hella good doing it.

Reread my post...the LSD units are generally the strongest part of the diff, the ring gear is certainly not. I've seen the diff housing crack in half, and tons of broken ring gears, I've still yet to see a broken S4 TII LSD unit...not saying it hasn't happened, just saying they are damn tough from what I've seen.

plz post when your stock differential mount rips in half

Nearly, yes. But I've see a few pop. Generally the case cracks at the pinion and then all sorts of destruction happens. Or the half-shaft flange shears off...

The whole concept of the car is turbo-NA, so if I am going to swap a diff it's going to be with something totally custom and not based on TII parts.

Yep, that's next on the list. Next spring I'm going to drop the subframe and with with urethane bushings all around, with the pinion snubber.

Posts like this remind me of 7 years ago when people would say "plz post when your engine blows up". :D

I'm not saying the NA diff won't blow up, but at 500 RWHP the TII diff will too.

Keep up the good work Aaron, I love to see the progress. What a beast that car has become.

Good work!

That of course depends on the application, we run turbo diffs at 500 HP with zero problems on road courses. Drag Launches CAN certainly be quite a bit harder on drive train parts. But, for those who dont drag thier cars regularly the TII and FD units are VERY stout. Certainly nobody can argue they ARE NOT stronger than the NA FC and FB units...

I think the weaker link in both turbo and non turbo cars is the transmission. Again the turbo unit is more stout but even 300 RWHP can grenade one......seen it multiple times.

very nice!

is this on 9.4 or 9.7 rotors?

next time can you have them turn off the shading and the curve smoothing?

That's sort of the point...Depends on what you are doing with the car. I fully expect to break either diff when launching the car on the anti-lag with a set of slicks. :) But during lapping days (if I ever manage to actually get out there...) I won't be worried in the least....

[QUOTE=patman;7318317]very nice!
is this on 9.4 or 9.7 rotors?
[quote]

9.4:1

Sure, but next time will likely be next year, so I don't know if I'll remember. :)

wow aaron very impressive im happy to see what youve accomplished if you dont mind me askin what are your et's at the 1/4?

Very nice run's, really decent power.


That's a bad-ss FC :icon_tup:

nice results.

When I was making around that power level I was starting to have traction problems in 3rd, with an LSD...

If you plan on hitting up st. thomas this year and want to borrow my slicks just let me know, I see 11's in your future :)

Why are HP and TQ crossing each other at 6k? HP is based on TQ and they always cross each other at 5,252. Something is up with how the dyno is setup...

HP=TQ * rpm/5,252.

:Wconfused