Welded Open Diff
 

Didn't want to hijack dvcn's timeslip thread, but it made me think. For predominantly drag racing, would it be a + or - to have a welded open diff as opposed to beating on a tor$en? Just thinking from a cost issue here, plus always hooking up two.

I guess so long as you dont have to turn.

I don't think it would be better other than possibly being stronger than a Torsen, assuming it is welded correctly, but it would suck for everything BUT the drag strip.

While I would never do this to any car I owned, I have ridden in my friends sr20 swapped 240 with a welded diff and the thing griped fine on the 110 freeway at speeds that never went below 90(Yeah, he had to use 2 lanes on that double apex turn by the park[for those of you that know the 110]) but otherwise there was no drama. I was very supprised. Anything other than highway driving sucks ass thoug, and he has been known to accidentaly kick the tail out on some onramps because of the diff.

Talk to Rappadan....if I remember correctly he is/was running a welded 1.8.

Not for me, just curious and it struck me last night.

Come to think of it, I had a friend with a 240 that he bought with a welded diff, the tires would chatter during anything but straight line driving

you'll drag tires on slow speeds all the time. Can't beat it for predictability though. You always know what its gonna do when you give it gas.

I saw a AE86 go sideways on the highway once and slam into an adjacent volvo. Found out he had a welded diff.

if you slam into a wall because of a diff. you don't know what the f@#k you were doing, or you were driving like an asshole and would'a crashed anyway. i have friends that have 240's they daily drive/drift, and i daily/track my miata with no problems for the past year. i love it at the track and i hate it in tight grippy parking lots. i'm always on ultra summer tires though which makes it worse. my friends cruise on normal tires and it's not so bad. alot of spec miata guys sell their aftermarket diffs and get an open one welded if that tells you anything.

Where the hell did you hear that..

The preferred differential for Spec Miata is still the clutch-type. While it is true that many national and regional drivers are upgrading to the 99+ TORSEN type differential as allowed by the 2007 General Competition Rules published by the SCCA there are still several top level teams that will swap out the clutch type for track specific needs, and various events where the .1 - .2 s/lap difference makes a difference. The torsen is heavier (markedly) and a bit "slower" but much more reliable. Very few, if any, competitive drivers are using a welded open diff. Not only is it slow, it is not legal as per the GCR. For the record I do not believe the open differential is technically legal either, but it's so damn slow no one would care if you used it, and I did for several years when funds were limited.

-Blake Thompson
SM 97
2008 June Sprints Also-Ran
IsellMiataParts.com

One other minor correction, spec miata guys would be selling their aftermarket diffs because they are not legal for competition within the current Spec Miata rules. Only OEM differentials are allowable:

9.1.8. Spec Miata Specifications
alternates listed below.
b. 1990 to 1993 Miatas may use the stock, unmodified viscous limited slip differential or the MAZDASPEED Motorsports Development limited slip differential, part number #QN10-64-A00 (previously TOY1-27-200 & 0000-02- 5501).
c. 1994 and newer cars may use the stock Torsen limited slip differential.
d. The 90-93 Miatas may convert to the 99-05 differential housing and the 4.3 differential gear ratio from the 99-05 model years. This conversion includes the driveshaft and half-shafts. The original 90-93 model rear suspension uprights must be retained.

emphasis mine

Damn gett'em

yeah your right about the sell to get oem type. and i won't name names but yeah, they did that cuz it was cheap and noone cared or called them out on having a welded diff. before they eventually changed it when they had the cash for the torsen. i wouldn't pick a welded diff. obviously, over a lsd, but it's gotten the job done so far, wayyy better then open (on my turbo'd miata). but yeah, that is against the rules.) i guess the guys i know sold the aftermarket lsd's and used the money to get some safety stuff they needed. they didn't mention that part to me. but, like you said, worked for you too for a while huh?

i think this guy is drag racing though, so all this info is useless to this thread, and i'll remember this info if i ever build a spec miata, thanks.

honestly have you ever seen one driven in a straight line...or someone who owned one that wanted to drive them 2 wheels in a row??

So, you are trying to tell us that you are running 29psi on a welded diff? And A LOT of SM drivers are running welded diffs too? Texans are so amusing sometimes!!

It's not a Texan thing...

my screen name refers to my galant vr4.

Attachment 212530

Attachment 212531

not my miata

Attachment 212532

although if i cared to, my miata is fully built, i would just need bigger injectors and a slightly larger turbo (gt2860 is in it now) to be efficient at that boost pressure. and yes, i would run it on my welded diff.

and no, if you read my previous post you would know why i thought that, but apparently it does happen if the desire to race is there and the deep pockets aren't.

The preferred differential for Spec Miata is still the clutch-type. While it is true that many national and regional drivers are upgrading to the 99+ TORSEN type differential as allowed by the 2007 General Competition Rules published by the SCCA there are still several top level teams that will swap out the clutch type for track specific needs, and various events where the .1 - .2 s/lap difference makes a difference. The torsen is heavier (markedly) and a bit "slower" but much more reliable. Very few, if any, competitive drivers are using a welded open diff. Not only is it slow, it is not legal as per the GCR. For the record I do not believe the open differential is technically legal either, but it's so damn slow no one would care if you used it, and I did for several years when funds were limited.
-Blake Thompson
SM 97
2008 June Sprints Also-Ran
IsellMiataParts.com

and yes we are pretty amusing although not nearly as amusing as u mormons!
i'm sorry i meant to say ''morons''. whateva, same thing. then again, i'm from michigan, but i got down here soon as i could!

I think the sentence you highlighted was worded wrong, he was referring to running an open differential for several years, not a welded diff.