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Drag Racing On Miata Torsen Diff, How much Torque can it take?

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Drag Racing On Miata Torsen Diff, How much Torque can it take?

Old 01-06-05, 03:59 PM
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Drag Racing On Miata Torsen Diff, How much Torque can it take?

I currently about ready to do my rear end upgrade for my first gen. Its going to mainly be used for drag, but some fun out in the twisties too.

Whats going in this stup, will be a supercharged S5 13B TII motor, with a weber carb. The main goal for this project is to give that rotary some much needed torque. The charger should be pushing 10PSI on low boost, and 17PSI on high boost. motor will have a large street port as well

This is going in a 1st gen GSL-SE by the way. What im planning on doing to the rear end is changing out to a 4.44 ring and pinion set, and upgrading the differential to a torsen differential out of a miata. Ive heard that theres actually two versions of this differential one possibly stronger than the other??

Anyway, I need to know exactly how much torque can I give to the rear diff?? Its going to have continual hard launches because Im using it for drag, and I need something that will not break easy. The only other option id see would be to upgrade to a ford 8.8", but i want to keep that option as a last resort.

Im sure some you racers out there have tried the torsen, so how did it work for you?
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Old 01-06-05, 04:11 PM
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On my turbo Miata I broke axles before I broke the Torsen. IMO however a rebuilt clutch type would be a better and cheaper choice in your situation. ISC also makes a 7" aluminum spool but that would ruin the car for the twisties.

There is a Type 1 and Type 2 Miata Torsen. IIRC the Type 1 came out of the 94 cars and is a 2-way. All the later models are the Type 2 and are 1.5 way. Seems like I've also heard one is stronger but can't remember.
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Old 01-06-05, 04:30 PM
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You should just do the 8.8". In stock form I doubt you will be able to break it.. plus it has tons of gear options. Upgraded axles and LSD will be good for well over 800hp (I doubt you will make that).

8.8" won't need narrowing. You remove the brackets from your stock axle and transfer them over to the 8.8". Then you need a new driveshaft and some different backspacing rims. Many of the V8 RX-7 1st gens do this mod.

Upgrading the gears in your 1st gen using the stock setup will be $$$$ and the Miata Torsen I doubt is very strong. Torsens don't last long with lots of drag racing abuse.

-GNX7
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Old 01-06-05, 06:06 PM
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I think the same Miata diff is used on the S2000 and they break alot of rear ends (ring and pinion mostly, I think) doing drag launches. That's in stock S2K's, so if you up your power levels to there you'll probably have issues.

-Andy
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Old 01-06-05, 08:09 PM
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I know for a fact the stock miata torsen can't even come close to holding up to a stock ford mustang 5.0 V8. But of course we're talking a lot of torque. For drag racing use you probably will have problems if you're running a modified turbo 2 rotor. If you're not going the turbo route you'll probably be ok.
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Old 01-06-05, 08:41 PM
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well keep in mind im going to be going supercharged, so im going to be having torque EVERYWHERE, especially on launches.

I did some more research, and people say they have been pushing 300+ HP on them and launching the **** out of them no problem. no mention on torque tho, as thats what it going to kill it.

I talked to my teacher in class today too, he used to race mustangs in the legal stocker class at the national level. He said he used the torsen once, and broke it on a one-two shift. Of course thats alot more torque than im talking about for my application.
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Old 01-08-05, 01:23 PM
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well if youre gonna run slicks and drag launch, then run the ford rear end.
no question.

its not even worth the hassle of tryng to make the miata diff hold up unless theyre all free parts.

look up some of the miata guys tht have swapped in 5.0 ford v8's and see what they think.. a stock 5.0 might put out a similar torque to your proposed engine setup.
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Old 01-08-05, 04:03 PM
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well, this car is still my daily driver, and the torsen swap I can do in a couple of hours, where as Id have to have the car down for a little bit to do the ford swap, then have to worry about the brakes, have to get new wheels if I dont use adapters, not to mention the fact that I cant weld, so Id have to have someone else transfter all the mounting points

i went to miata.net and asked them what they think, and I'll let you know what they say
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Old 01-08-05, 04:09 PM
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Originally Posted by AMRX7
I think the same Miata diff is used on the S2000 and they break alot of rear ends (ring and pinion mostly, I think) doing drag launches. That's in stock S2K's, so if you up your power levels to there you'll probably have issues.

-Andy
why would a mazda diff be used on a honda? is this true ^
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Old 01-08-05, 06:38 PM
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the miata guys seem to think they may not be able to take more than 250 ft/lbs of torque. I still havent been able to get an answer as to what breaks, weither its the diff itself, the ring and pinion the axels or what.
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Old 01-08-05, 09:01 PM
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Originally Posted by PureSephiroth
why would a mazda diff be used on a honda? is this true ^
The S2000 guys were paying premiums for aftermarket r&p's until someone figured out they were a Mazda part.

-Andy
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Old 01-08-05, 10:30 PM
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well heres the best responce ive heard from the miata guys:

The Torsen will handle a beefy 302 without any trouble whatsoever. There was one in Denver that was spinning the wheels all weekend long at the meet out there. The trouble would come if your foot were to accidently "slip off" the clutch at a high engine RPM and the Torsen and/or your tranny becomes toast. The car does not weigh enough to create sufficient resistance to destroy the differential from shear torque of even a rapid normal clutch release or full acceleration with street tires.

However, put on some wide sticky meats... then, if you try real hard.... rev the engine to say, 4000 RPM and release the clutch real fast, you deserve what you get. Downshifting to the wrong gear can be fatal with these tires also.

A voice of experience. If it's been made, I've hatched it, and replaced it. From 1926 to 2003. One of 'em I did 10 times in a row.

If the torsen can handle a beefy 302 without any problems, then a suprcharged 13B should be OK
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Old 01-09-05, 10:18 AM
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Hornbm,

Did you read what the guy said? The V8 Miata was not getting any traction, that is the reason it was not breaking parts. You can put 1000 lb/ft of torque through a stock driveline and never have any issues if you can't get traction. If you are planning on drag racing, I am assuming you will be looking for maximum traction. Sounds like you might be in trouble with the torsen with good traction and drag launches.

Andrew
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Old 01-10-05, 04:17 AM
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The miata guys who run 5.0s in their cars use the rearend from a thunderbird so you may want to look into that. I have no idea if it will work on your car but i works for the miatas and their diffs work for you so my guess is the thunderbird diff will work for you.
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Old 01-10-05, 12:27 PM
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Originally Posted by andrewb70
Hornbm,

Did you read what the guy said? The V8 Miata was not getting any traction, that is the reason it was not breaking parts. You can put 1000 lb/ft of torque through a stock driveline and never have any issues if you can't get traction. If you are planning on drag racing, I am assuming you will be looking for maximum traction. Sounds like you might be in trouble with the torsen with good traction and drag launches.

Andrew
right on.
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Old 01-10-05, 01:40 PM
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good point I should have read that more carefully. Honestly, im really leaning to trying the torsen out. If it breaks then i'll move to a ford 8.8, but I want to put an end to this question.
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