To those with 20b's

How does your car drive compared to your 13B? I know people make big Hp #'s with the 13B's and RE's, but the relieablity of those motors is not very high. The biggest problems i see with at 20b is:

1. Heat, and lots of it
2. Weight and positioning. Will cause the braking and handling feel of the rx7 to become heavy and unresponsive.

Can anyone who has this conversions (i have a T2) tell me what the do and dont like about it? Its alwasy good to hear from actual users....

Graham

 

1. yes, mine is perfectly fine on the street, but on the mountain or on the track it wouldnt take it

2. no not really, its a little worse than stock, but not detrimentally so. my brakes barely work so no comment on that

pros:
engine is a lot easier to work on than a 13bt. i can pull anything off the motor in 15minutes, usually without pulling the intake.
its smoother,
it offers effortless acceleration
and it sounds great

cons:
thristy, with the e6x it got 11-14, the e11 is 16-18.8, its now "ok"
its hot! granted its stock twins, but it still has cooked the paint on the passenger side frame rail

mike

 

i love my 20b!
I have had a 3rd gen and lots of 2nd gens and
by far the 2nd gen 20b car is the most fun to drive out
of all the cars that i have had, coming in a close second
the turbo convertible is fun to
As for running hot i have a idea that i hope to follow up on
before next year that i think will solve the running hot problem.
will post as soon as i get it all set up.
the extra openings in the nose also solved the hot running
problem i had on the highway, didn't matter how hot it
got this summer on the highway the engine temp stayed at
185F as soon as i got into traffic wow did it get hot, thought
my legs were going to cook!


matt

 

It drives a little better. With the wider wheels and tires on the back, I can use the torque to just scream through turns. As for reliability, I've got 40,000 miles on it, so far, and the engine is as strong as ever.

You're absolutely right about the heat. If I were starting from scratch, I'd re-engineer the front of my car to increase airflow.

As far as weight, the total is 3340 lb. (convertibles are much heavier than coupes), and the distribution is 51% front and 49% rear (battery in trunk).

On the track and in daily driving, the handling and responsiveness are not impaired. On an autox course, it plows a bit, due to the smaller front tires. If I wanted to run a lot of autox, I'd go for a different tire and wheel combination.

Hope all that helps.

 

Great thread!

When I run the car in Canada there is NO heat issue. When I am in Vegas heat is an issue. Part of my problem lies in that I have a front mounted I/C so not enough airflow is getting to my rad. Engineering over the winter involves putting in an aux set of fans between the i/c and rad to get more airflow while in traffic and putting duct work in so the airflow from the front has to go through the rad. Air takes the path of least resistance and when driving, air for the most part goes around the rad and not through it.

 

This is also the norm for a stock FC, so I'm not sure if it has much to do with your modifications. I have found that playing with the tire pressure helps, as does swapping the power steering rack for the better manual rack, but I did not completely eliminate this problem until the Mazda Motorsports (ITS) suspension was installed on my car. I wish I could give a technical explanation for the problem and solution, but I have no formal education in car suspension theory, and this is the best I can do. Maybe one of the suspension gurus can explain this better?

 

Yeah, this is a good thread. I can't wait to add my own comments on my 20B.

 

Back from the dead

I'm esp. interested in ppl's opinions of handling, since the weight distribution is a major concern of mine...(esp. in FDs)

Attila the Fun, I just noticed you're local...and I didn't know you have a 20B RX7. You think I can take a look at it sometime...maybe even get a ride in it?

 

Yeah. I thought of moving to Canada as a solution for overheating, but a number of other issues (wife, job, citizenship, polar bears, etc.) made me drop the idea.

 

After installation, my weight distribution is 51% front and 49% rear. No problem, but that's in an FC.

If you mount the 20B back (through the firewall) in an FD, handling is no problem.

Sure, you can see the car. Send me an email at asam@cris.com, and we'll see what we can work out.

 

Sorry to take so long to reply. The automatic notification isn't always reliable.

You're right about the tire pressures. 45 psi in the fronts makes it handle very differently. It's still not competitive with the 8.5-inch-wide wheels, but for two autocrosses per year, it's not worth worrying about.

Without getting all technical about it, the front contact patches just aren't big enough to handle the kinetic energy pushed through them by tight, low-speed turns.

Since the tightest turn on a track (like turn 4 at VIR) still gives you more wiggle room than most autox courses, it's rare to overdrive the front contact patches, unless there is a failure inside the helmet.

 

What accounts for that excellent weight distribution? Is the FC heavier in the rear than the FD? Or is there more room to fit the 20B further back in the engine bay?

Nice...I'm emailing ya
LOL. If 8.5" isn't large enough in the fronts, what is? 9.5s? I didn't even know you can go larger than 8.5s in the front?

 

- An FC convertible has almost 300 lb of additional bracing amidships to make up for the loss of torsional rigidity caused by the loss of the metal top, so the center of gravity is shifted toward the back.

- The rollbar and the Dynamat add weight behind the center of the car. (I put in a whole roll of Dynamat to cut the noise from the Borla exhaust I had in the 2-rotor days.)

- The battery has been moved into the trunk.

- The 20B is only about 100 lb. heavier than a 2-rotor (according to Peter Farrell), so it's not such a big change in the cars balance.

With the Tripoint fenders, I could fit 315 x 40 x 17 tires under there. When I inquired about the fenders, Tripoint sent me a photo of their autocross car with that size tires on all four corners. Realistically, I would just get another pair of 10" wheels to match the rears. That would, I think, be adequate for good autox handling after fiddling a bit with the tire pressures.

 

my car wieghed 2860 with the 3 rotor and 2780 without. no other changes were made to the car

 

Hmmm...so roll bar, battery in the rear, and some dynamatting. Sounds like a plan Might even consider another fuel tank for race fuel. I think that would def. even things up a bit.

Is that an FB??

 

No it's an Fc. Fb's are in the 2300-2500 range stock.

 

What about coolant temps for you guys driving around on the street? When you get in low rpms situations does the coolant temp start to climb? I've talked to a couple guys that around town going slow and also on the interstate cruising at a low rpm thier coolant temps climb higher than they would like. Makes me wonder if the water pump is sufficient, I know a lot of guys use thier 13B water pump. It might not flow enough when you add 50% more displacement.

What have you guys experienced?

 

Electric fan with a huge *** AFCO Racing radiator...
Water temps are not a problem for daily driving.
But then again, we got no turbos.

Side note, we're starting to get progress on the turbo front.
Our first turbo is in the mail, and we'll see if fitment is going to be a problem...


-Ted

 

I knew that lol. I have an Fb. Gross weight is 2350 or something like that But for some reason, when I looked at his avatar, it looked like an FB. Then when I looked at it again right now, it looked like an FC

Yea Stephen, I heard that coolant temps were the major issue as well. Oil temps were just fine, but I def. recall that coolant temps are worrysome. What other ways can you address that issue, other than a huge radiator? Is there a bigger/better water pump? (Why isn't the stock 20B pump good enough?)