Just wondering what you guys think the pros/cons of each approach are...
For the 20B I'm thinking N/A reliability but high install cost...

The TII is an easier install, but not as reliable...

Just for context, this would be used in a car taking part in a very long distance race.... ...the kind with minimal service stops (fuel efficiency plays a small part.. unfortunately)
And this car would be expected to keep up with the 'big boys' (ferraris, porsches, audis... etc)

The car this would be installed in is a fully stripped, roll-caged 89 GXL chassis with a full TII driveline swap and whatever driveline strengthening you guys feel is necessary...

Any suggestions would be greatly appreciated...

 

The 20B will not be any more or less reliable than a TII engine unless you plan on converting the 20B to a NA. A built 20B is going to tear up that TII gearbox, so you may want to stick with the 13BT.

The 20B will have more torque to get you out of the corners, but the 13BT will give the car a slightly better polar moment of inertia. I assume that you will use a dry sump either way, so the front sway bar problem will not be an issue. It is difficult to choose between the engines without knowing all the rules of your racing class. What do the winning RX-7 teams use in that class?

 

Evil Aviator, I've got a question about the oil pan on a 20B. It has two sumps. The main large one in the rear, and a very small one in front under the front cover. Is that small one necessary if going with a custom pan?

 

That small one up front is where the oil pickup line comes down from the engine. So, unless you consider relocating that and fabricating a new oil pickup, it is very necessary.

 

This is a little off track but since were talking about about oil pans is there a custom Pan for an FC or does the stock one need to be modified?

 

mazdacomp has a bigger oil pan for the 13b fc.
they also have 20b drysump plates

mike

 

Moroso also sells oil pans for RX-7's.

 

Yeah, what he said.

I looked for a way to rework the oil pickup, but I just didn't see any way to do it that was less difficult or less expensive than making a custom sway bar. Maybe someone else has better idea?

 

run the oil throught the sway bar! d'oh its soo simple, and the swaybay bushings will stay quiet too

mike<---thinking about making swaybar brackets

 

Hmm, that's interesting. So you're saying that the pickup tube runs from the front cover, along the bottom of the engine, and then down into the big sump? I ask only because I thought the pickup tube was on the intermediate housing like on two rotor engines.

Man, all I'd need is to shorten the pickup tube and relocate the sump further forward. A little weld here, a little weld there and my custom pan would be done!

Evil, Kurgan, please tell me I'm right.

By the way, I always thought it was a little stange how the 20B didn't have the long oil cooler line coming from the lower corner of the rear housing like the older 12As and 13Bs did. I guess Mazda needed an inspection plate there more?

 

Just a side note - these oil pans are not designs for stock FC or stock FD applications.&nbsp I believe they are made for earlier R-100, RX-2, RX-3, RX-4, 1st gen(?) engines...


-Ted

 

This car, when built, would not be competing in any 'sanctioned' racing class (but no, not street racing...)
The question was to compare the reliability and power of a 20B that has been converted to N/A versus a lightly modded 13BT (consider each engine having the same horsepower... thats the amount of modifications done to the 13BT)

Speaking of HP, any ideas on the approximate output of a normally aspirated 20B engine?

 

I thought that I remembered seeing 86-91 and 93-95 in the Summit import catalog a few months ago, but now they just say 13B.

 

A little bit of info here.

https://www.rx7club.com/forum/showth...threadid=57662

https://www.rx7club.com/forum/showth...threadid=51238

Really dependent upon porting.

 

yah, to swap a 13b into a pre rx-7, you either need to have a nla rx-4,5, repu oil pan (13b rear sump) and pickup, or take a gsl-se pan and put it on backwards. this requires welding up some of the mounting holes and redrilling them. except for the motor mount bolts, they have not changed the oil pan mounting patterns

mike

 

mmaragos: thanks man... I think I may end up going the route of a 20B with stock twins on it... more room for tweaking...

 

man it sounds like you're interested in a gumball rally

 

ahhahaha... First prize to Therx7ist, he (almost) got it right... but it's a cannonball run, the gumball is just one of several cannonball runs...

(so all you guys know, this is still a ways in the future, so don't expect some black RX-7 domination in the next cannonball run you hear about... )

(Mainly the wait is so that I have the $$ to pay for the tickets afterwards ...and the taxi to where ever I want to go, 'cause I got a feeling that I won't be drivin much for a while after that.... ...but It'll be worth it... )