174 replies to this topic

[Tom Hampton]

It doesn't cost 60k to go on a diet, Drago.

5 months, 50.lbs, shutting all the whiners up? Priceless.

And.... You can then be a skinny little shit like me!

[Jim Drago]

It doesn't cost 60k to go on a diet, Drago.

5 months, 50.lbs, shutting all the whiners up? Priceless.

And.... You can then be a skinny little shit like me!

all true.. but easier said than done  

That quote has to be from at least 5-8 years old?

[Bench Racer]

all true.. but easier said than done

That quote has to be from at least 5-8 years old?

5-8 years ago I brought my now 14 year old grand daughter to Road America, introducer her to Jim and told her Jim drives a Spec Miata and pointed to a car, ok all's good. Later were watching qualifying outside T7 downhill to T8 and I pointed out Jim and car. From the mouth of a little girl said very soberly, he fits in there. every time I think about this.   

[gerglmuff2]

does a "top prep" 1.6L have the mazdacomp diff or the torsen? does the torsen make the 1.6 chassis even more peaky and tough to drive compared to the mazdacomp diff? Advanced says the mazda comp isnt any faster on the perfect lap, and i believe it, but when the shit hits the fan and your all over the place, i gotta believe that clutch in back is more trustworthy. 


i just blew the diff in my 1.6 ... totally unrelated though i promise

[davew]

Just put the 1.8 Torsen in the car and forget about it. We did back to back testing of a mazdacomp diff versus a Torsen this spring. Same car, same driver, same track , same day. Found no repeatable difference in lap time. Feels a little different, no more than being a few pounds off on tire pressure.

 

A 1.6 diff will blow up. Not an IF or a WHEN. It will, so just bolt in the bigger unit and forget about it.

 

Dave

[Bench Racer]

Gordon, all laps are not perfect. I'll take the Mazda Comp L/S because when humping tall gators the Mazda Comp L/S will not open. The Torsen is heaver statically and dynamically. It has been stated on this site by someone (Saul) with more technical knowledge than me that generally when a Mazda Comp L/S is blown it's the gears/bearing housing which is trashed and the actual Mazda Comp L/S can be cleaned and reused.

[davew]

Gordon, all laps are not perfect. I'll take the Mazda Comp L/S because when humping tall gators the Mazda Comp L/S will not open. The Torsen is heaver statically and dynamically. It has been stated on this site by someone (Saul) with more technical knowledge than me that generally when a Mazda Comp L/S is blown it's the gears/bearing housing which is trashed and the actual Mazda Comp L/S can be cleaned and reused.

 

Exactly, the diff spins a tire when the car is in the airborne part of the gator, then slams into the ground and breaks the gears. The 1.6 gears are the problem, not the diff unit.

 

Install 1.6 diff, break it, replace it, repeat, repeat repeat.

or

Install 1.8 Torsen, Forget about it.

[gerglmuff2]

yeah i took mine apart and the diff itself looks alright (has a notch where the ring gear cracked), the pinion and ring are toast, as is one of the shoulders that bolts it to the case, cracked. i have a spare case, so im not super concerned about that. its more like, it will cost about the same to have it rebuilt as it will to put the torsen in. shims, bearings, a new ring and pinion are 400 bucks alone .... im thinking torsen at this point, but i really like how the car feels, esp the diff. 

[William Keeling]

yeah i took mine apart and the diff itself looks alright (has a notch where the ring gear cracked), the pinion and ring are toast, as is one of the shoulders that bolts it to the case, cracked. i have a spare case, so im not super concerned about that. its more like, it will cost about the same to have it rebuilt as it will to put the torsen in. shims, bearings, a new ring and pinion are 400 bucks alone .... im thinking torsen at this point, but i really like how the car feels, esp the diff. 

 

yeah i took mine apart and the diff itself looks alright (has a notch where the ring gear cracked), the pinion and ring are toast, as is one of the shoulders that bolts it to the case, cracked. i have a spare case, so im not super concerned about that. its more like, it will cost about the same to have it rebuilt as it will to put the torsen in. shims, bearings, a new ring and pinion are 400 bucks alone .... im thinking torsen at this point, but i really like how the car feels, esp the diff. 

check the runout on the diff -- sometimes bent when the ring gear is trashed

[trimless]

Raced a Mazdacomp for 6 years in my 1.6

It did finally blow up, but that would be expected based on my driving style.

If you are not racing to run up front a Torsen is best choice.  I wanted to win races so choose the Mazdacomp.

It is lighter, makes more power on the dyno ( less drag) and less slip over bumps. I would say it's faster at a many tracks I've raced, not doubting what Dave said but again this is my personal experience.  Durability is not it's strong point.

[OrangeCrush86]

Raced a Mazdacomp for 6 years in my 1.6

It did finally blow up, but that would be expected based on my driving style.

If you are not racing to run up front a Torsen is best choice.  I wanted to win races so choose the Mazdacomp.

It is lighter, makes more power on the dyno ( less drag) and less slip over bumps. I would say it's faster at a many tracks I've raced, not doubting what Dave said but again this is my personal experience.  Durability is not it's strong point.

 

I do not see how a Torsen would make more power on a dyno. Both a clutch type and torsen type diff are essentially static if both wheels are spinning the same speed (equal torque applied).

[Steve Scheifler]

I do not see how a Torsen would make more power on a dyno. Both a clutch type and torsen type diff are essentially static if both wheels are spinning the same speed (equal torque applied).

For one, rotating parts are larger and heavier. It’s small but not nothing. The bigger issue is likely the efficiency with which power is transmitted through the unit. And the wheels are almost never rotating at exactly the same rate so there can be a difference in efficiency there.

Saul, would you be able to offer an educated guess on the difference?

[speedengineer]

Rotating inertia differences would be absolutely negligible.  Zero measurable difference by any method we use. 

 

HP loss differences may be there, but small.  Frictional/viscous drag losses in bearings and ring and pinion should be slightly larger for Torsen, since larger diff.  But the differences would again be negligible. Some amount of power is absorbed inside the clutch disks in a mazda comp or cusco.  This is proportional to the diff clutch torque*difference in wheel speed.  Since difference in wheel speed is small, so is the wasted power.  Power is wasted in the torsen too, the friction in all those gears is what allows for the torque bias ratio that makes it a limited slip. 

 

The difference in performance would be in the way the differentials affect vehicle dynamics.  They function very differently.  I can't tell you which is faster because I haven't run both in the same car.  I like the way the clutch type drives though.  Also, Torsen suck on tracks where they get wheel spin. 

 

Torsen, slightly better weight distribution, more weight down low and slightly rearward.  Negligible though.

 

Torsen, more reliable...maybe  1.6 diffs do break, but I haven't personally seen that many fail considering the number of 1.6 cars I see on track.  I've seen way more torsen diffs being swapped out because they wear out and get inside wheel spin, thus need rebuilt. 

 

I'd only put a torsen in a 1.6 miata if it was an endurance car.  ymmv

[Steve Scheifler]

Generally agreed, but I’m also keeping in mind that what is considered “relevant” in this class is on a totally different scale than most. Witness the drama and hype over the CV joint cages which are likely minuscule even compared to the differences between a torsen and the old clutch type. Describing the Torsen you mentioned “the friction in all those gears”, which is where my concerns lie. Alrhough I haven’t gathered a lot of empirical evidence let alone scientific data my observations from running both at the same track on the same car are that the Torsen runs hotter. That may be in part about how, and how well, it dissipates heat but may also suggest lower efficiency. It also felt slower and my times were off, though there could always have been other factors. I switched before the end of the weekend and was back on pace relative to Tom in our second car.

[Pat Mcg]

Don't disagree with Dave... But.  Mazdacomp or Cusco is the best option for 1.6 IMO.. You have to take care of them.. Change fluid regularly.. Inspect the service plug for signs or issues.    But, for Champcar, WRL, or any other track event where you are racing more than 45Min at a time..  Torsen.   However, since you blew up your mazdacomp...   another option..   You can run a VLSD and get by.. The wheel spin will let your engine rev higher lol..    You can pick them up for about 150 bucks until you can buy the internal for a Cusco swap....  The CUSCO is outstanding.   Get it set up correctly and you will be pleased..  If the Mazdacomp can be rebuilt then obviously that's your best path...