Been gaining some interest in the 20b conversion after Cameron took me for an enthusiatic ride awhile back. He built my 13b motor and I added 99 twins but I break loose in second gear at 12 psi with new 265 by 18 S-3's on the rear. He dynoed me around 300 which doesn't meet alot of the (claims) I have read on this forum but it is a realiable and an enjoyable daily driver. Cam is running 305 by 18 Hoosiers on the rear and breaks loose under acceleration. I was wondering what others folks have sucessfully run without getting loose?

On another subject, I understand speed shifting (not excessive) can be detrimental to the stock transmission with the additional torque of the 20b. I have owned (2) 3rd gen's and the transmissions are a weak point even with 2 rotors. What options are available that you folks have installed (other then a heavy old borg warner) that can fit up without an engineering convention.........what are the costs (i.e an after market six speed...5- 6 k?)

Appreciate the lessons learned from those who have been there as I am trying to assess the reality of the tradeoffs............

Thanks in Advance.
Andre

 

I'm hoping that 335 is wide enough. I have a Tri-Point flare kit. Will run treaded on the street and slicks at the track.
I'm hoping for between 600-700 hp at moderate boostlevels.
Have a Kaaz diff with the TII 4:10 gears. I may switch to a gear that is taller, this would help, if only a little with traction. Plus 1st gear may not be so useless.
As for trannies I will be running a Jericho 5-speed dogbox. Changing gearing in dog-ring trannies is snap, so making any gear as low or tall as needed is no problem.
There are a few guys in this forum who still use the TII trannies with success. Howevere I doubt they are slamming gears.

p.s. will be picking up my engine tommorrow and will try to post pix this weekend so I can have my turn to show it off

 

Rx7 Heaven.

Apprecaite the response. must be exciting to be picking up your motor tommorrow. And cannot wait to see the pic....

I guess I didn't include the rear end, but should have. Only familar with the Jericho tranny's from hotrods, not rice burner installations,

Does it bolt in? what is required?

Andre

 

There is no such thing as a transmission strong enough to handle the power, yet still be light in weight.

Some transmissions from other street cars that have been installed on street RX-7's wtih 20Bs are the WS6's T56 unit, the 2JZ Supra's V160 unit, and the Ford T5 transmission.
There isn't any transmissions that will bolt right in and handle the power. You will need custom work done, transmission tunnel modifications, adaptors, etc.

A racing transmission, or custom transmission will cost anywhere from $3000-$30,000. A few guys have installed the HKS box which costs around $8,000-$10,000. For my high powered 20B I will be installing a T56 transmission and Ford 8.8" rear end with 4.10 gears.

 

Bridgeported,

Appreciate the info, I am sure you will have a bullet proof combination for your high horsepower application.

I was thinking of a 450 to 550 hp setup while retaining good handling attributes. Can/has the stock transmission been modified to support this range of torque/horsepower?

Also what are your plans to place all that power to the ground in a street scenario? or are you building a strip car?

Thanks again.....

 

I am looking to put down around 600 - 650rwhp and I will be using the cusco 1.5 LSD, stock 98 tranny and 4.30 gears

I'm going w/ the stock 98 tranny because my car won't see alot of strip time most highway running

 

The stock transmission should be able to handle a 450-550 hp 20B with some upgrading. A setup like 20B 3rd Gen is going to use sounds like it would be pretty good for your application as well.

For those reading this, a good point to remember is the difference between 20B and 13B power outputs. A transmission can't just handle X amount of HP. A 20B with say 600 rwhp will rip apart the stock transmission in no time, but a 13B with 600 rwhp will not be as rough on the unit and the transmission will last longer.

My car will remain a street legal, daily driven car, but of course tuned more towards drag strip performance than anything else. I don't want this thread to get too off topic, but if you want to discuss my project plans, you can click on my website link or private message me. I just made the site a few days ago, so there isn't much info on it yet.

 

Why do you want to use the low 4:30 gear, especially when you say you are doing mostly highway running. Is that what the fd came with, I don't think so, but I don't know too much about fd's.. I'm sure you will hate it when you are breaking the tires loose everywhere and stopping at every gas station between all the smokey clouds of rubber. Not to mention, 1st gear will be completely useless. Most track racers (no turbo/no power = needing all the help you can get to accelerate and never topping out) use 4:30. I would imagine it would be popular for drag cars also. I think it is a bad choice for any car that has good power and is street driven. Just my opinion though.

 

The 4.30 gears and a lightweight flywheel will help with acceleration and keep me in the upper rpm powerband, which is what I want. 4.30's are stock gearing in the 98 - 00 RZ model FD's. As far as 1st gear being useless, running on the highway I will never be in 1st and I won't be launching hard from a dead stop. I also plan to road race alittle which the 4.30's will help in keeping the rpm's high.

 

I was thinking 3.73 or 3.55 gears when I finally get to start really working on mine. I have a T56 built and ready just need an adapter or custom scatter shield.

Tire size...... I am gonna run 17's day to day and matching 15's with ETStreets for the track and maybe some street racing Widths...... gotta see what will fit.

I've had to put my 2nd gen project on hold till I get a house But I'm still researching and trying to get all my ducks in a row before I tear into everything.

 

When I start my project, I'll be using a T56 as well, and my rear end will be a Ford 8.8" but I'm going to go with 4.10 gearing.
Wheels will be 16" diameter.

 

Bridgeported/20B 3rd Gen,

Sorry have been out of pocket but I appreciate all the responses though......

Is the 98 stock tranny stronger then the US '94 version?

I find it interesting that folks are tackling this issue with different hardware options. I would like to retain the independent rear suspension for the handling advantage, as I am not looking for extreme horsepower. Cam is an experienced track driver and his car handled very well in his hands. He was able to take 90 degree turns beyond what I had experienced and his 13 inch brakes were simply amazing in their stopping power.

I do hate the thought of replacing the subframe and repositioning the rack and pinion. I am paying special interest to the MVA motorsport thread. If there is reality in their products, the installation would appear to be simpler, less expensive, and less intrusive.

Assuming that the power train strength can be achieved for the 450-550 hp range with more research or education on my part, the application to the ground still concerns me. Are there folks who have completed their 3 rotor conversion who could speak to their experience with this issue. I believe Cam was running "Forgeline" rims (not sure if I have that right). He was running 305/35/18 hoosiers and under hard acceleration, he had to feather a bit.

I know with my 265/35/18 S3's, the rear breaks loose in 2nd when the secondary turbo kicks in at only 300 rwhp. The 3rd Gen is a light car with short wheelbase and can have tendency (if you are not careful) to sweep ends especially with the additional horsepower of a 20B.

I know you folks have worked hard at your projects and I enjoy the lessons learned from your experiences.

Andre

 

Well everyone needs to remember that the lower the side wall of the tire the easier it is to break loose. A 275/45 will break loose before a 275/60 because the side wall of the 60 series isnt as stiff as the 45. and with the side wall flexing it will absorb the energy and allow it to be transfered to the road. the low profile tires were designed for cornering forces

I was gonna go with the 17's for day to day use cause they would look good. but swaping to a set of et streets on 15's so I can get that grip that will be elusive on our applications. I still dont know what widths Ill be using ......