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Discussion Starter #1 (Edited)
I purchased a turn key race car a month ago and it came with a T2-R out back. It does great overall; however doesn't do super well in lower speed turns. Pushes.

I have another Cobra IRS diff built up already with a new DPI Platinum LSD unit.

Anyone run both and/or can provide feedback on the units?

Car is a '93 Mazda RX-7 with a 438ci resleeved LS7, Aviad dry sump, GForce dog box, Cobra 3.27/T2-R rear, and 18x12's with 315's front/335's out back. 2400lbs dry with a little over 600hp. Entire chassis was sandblasted and then powdercoated. Won SCCA ITE West Coast last year with a 383 LS1 making 100rwhp/100rwtq less.

Thx

Some pictures! I'm pretty damn happy with the purchase thus far. Plan is to learn to drive it better, then potentially race in the future.







 

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I can't compare it to a T2R but the DPI Platinum is really good.

Expect some disconcerting noise on the first day or two if the unit is brand new.
 

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Your car is sweet.

IMO, I would tune about 11 billion other things for a low speed corner push before I changed the differential, especially since you already have a Torsen type. E.G. I would be very surprised if the push went away after you switch diffs.

DaveW
 

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Discussion Starter #5 (Edited)
It is a light push..... the previous owner is a Mechanical/Electrical Engineer and knows his sh*t. He mentioned it doesn't do well in slow speed corners and has been dialing in the car the past year. The big rubber up front probably isn't helping with this minor issue.

I plan to keep my testing going and get more familiar with the car. Next track day is 10/12 at Thunderhill again. To me the car is a beast and i simply need to learn it. I haven't been out in a car on the road course in 5 yrs! yikes.

Thanks for the feedback.
 

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Do you mean smaller front tires? Big tires up front would tend to reduce understeer.

IMO, I wouldn't switch any parts, just (as you plan) get used to the car and a minor shock/swaybar/spring adjustment will fix any minor problem.

A differential is a major change, not a minor one.

DaveW
 

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Definitely the sickest car I've seen in this forum. I run a DPI platinum track and have push. But, my chassis guy and I agree that it's very unlikely caused by the diff, the T2-R isn't much different so I'd look elsewhere. You probably have the push in high speed corners as well but you're just not driving it fast enough to notice the push in the high speed turns. Aero also hides mechanical grip issues in high speed turns.

My car has had chronic push for many years, over the last year I've worked with a very capable chassis setup guy who happens to be a multiple national champion auto-xer. We've dramatically reduced the push by adjusting the following:

Spring rates
Adjustable front sway bar
Adjusted the front roll center

The car is still not perfect but it's about 3 seconds a lap quicker at Thunderhill than it was before I started working with my chassis guy.
 

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My car has had chronic push for many years, over the last year I've worked with a very capable chassis setup guy who happens to be a multiple national champion auto-xer. We've dramatically reduced the push by adjusting the following:

Spring rates
Adjustable front sway bar
Adjusted the front roll center
Dude, where'd you find the adjustable front sway bar??
 

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Discussion Starter #13 (Edited)
Thx for the input. I'll simply learn the car more before I start tearing things apart. Baby steps as mentioned 1st.

My car has a stock car style adj hollow front adj sway bar on it. I'm sure it could be adapted to any Mustang if they don't sell them already. It looks like this:
http://bauerspeedracing.blogspot.com/2011/03/tri-point-engineering-front-swaybar.html

Ring gear on the Quartermaster triple 7.25" clutch setup is all chewed up and starter won't engage properly since last outing. Confirmed it this weekend after doing some work on the car. Plan to work on that later in October and fix a few other issues on the car.

I'm stoked on the car purchase. I did however forget how much $ it is to take a car to a track day with a truck/trailer/diesel/entry fees/hotel/food/race fuel and then hoping nothing breaks. Its an easy $700 not including tire wear, brake pads, rotors, etc.

Coupe de Surf- I know Mike at Maier Racing as well. He knows his sh*t but is pricey.
 

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Thx for the input. I'll simply learn the car more before I start tearing things apart. Baby steps as mentioned 1st.

My car has a stock car style adj hollow front adj sway bar on it. I'm sure it could be adapted to any Mustang if they don't sell them already. It looks like this:
Bauerspeed Racing: Tri-Point Engineering front swaybar

Ring gear on the Quartermaster triple 7.25" clutch setup is all chewed up and starter won't engage properly since last outing. Confirmed it this weekend after doing some work on the car. Plan to work on that later in October and fix a few other issues on the car.

I'm stoked on the car purchase. I did however forget how much $ it is to take a car to a track day with a truck/trailer/diesel/entry fees/hotel/food/race fuel and then hoping nothing breaks. Its an easy $700 not including tire wear, brake pads, rotors, etc.

Coupe de Surf- I know Mike at Maier Racing as well. He knows his sh*t but is pricey.

Small world! Mike comes up here every year for the SCCA Packwood NT and Ron Bauer (Bauerspeedracing) is a local I compete with in PAX. His DP Miata is the schnitz!!
 
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