Wargasm

In order to get more exhaust flow out of a 20B (target of 450-550 RWHP), is it possible to just install 13B-REW or maybe 87 TII rotor housings and then port them? Do they fit, or are the holes where the tension bolts go too small?

Thanks for answering this newbie-ish question,
Brian

87 TII
93 R1 T04S

KraftDinner

The 20B rotor housings are near identical to the 13B-REW ones, not TOO much difference. If your goal is 450-550 rwhp, you don't need to change much with the engine.
I estimate that a completely stock internals with stock twin turbochargers should yeild you about 450 rwhp @ 12-15 psi.
And I know, that a streetported 20B with stock twins will give you about 525-550 rwhp at 15psi

Evil Aviator

Attila the Fun's 20B FC has 13B-REW rotor housings:
http://www.cris.com/~Asam/20B.html

Wargasm

Kraft: Hmm, I have some pics of a 20B exhaust port somewhere here on my computer and I think that they were a little more curved on the bottom and smaller overall than a 13B REW port.

What do you do for engine management on these cars? It's my understanding that they won't run on the stock ECU due to not having the auto tranny hooked up. On another note, does anyone sell manifolds to go to a single turbo?

Thanks,
Brian

Evil Aviator

Yes, you need to fool the stock ECU into thinking that the auto transmission and variable exhaust is still hooked up. You can search this 20B forum for threads on the subject. IMO this isn't worth the trouble, especially since the 20B-REW only made about 300hp in stock form. If you are going to spend $10,000+ on a 20B conversion, then I don't think that another $1,000-1,500 for a standalone EMS is out of line, especially since it will bump you up to the 400-550hp level and it will allow for better fuel control to help keep you from frying your new project.

As far as I know, nobody offers a production turbo manifold. However, you can get one custom built, and Racing Beat sells a 20B exhaust flange which will save you a lot of trouble.

Wargasm

Evil Aviator... good info...

I was lucky enough to get a test drive in George's RXX-7 over the 4th weekend, and ever since then my mind keeps coming back to that over and over. I've always wanted a 20B!

I am trying to research how much it would cost me to make a 20B convertible somewhat similar to George's... I already have a running 87 TII (could use a tranny and diff rebuild) that I could cannibalize for parts to put into a 'vert chassis. I'd just need a 'vert chassis, a 20B, oh, and about a million other parts.

I'd love to buy his car, but I'm not too sure that I want to/can afford to drop that much money all at once into yet another toy! (I work for Worldcom hahaha). Maybe you guys will say I'm nuts... would it be better to just buy his?

Used 20B - 3000
Vert Chassis - 5000
Rebuild 20B with 13B REW rotor housings - 3000
Single turbo stuff - 3000
Intercooler - 1500
Radiator - 500
Engine management stuff - 2000

Anyhow this is a very rough first estimate. I know that I probably have to add another 5000 for misc crap that will come up.

That puts me at about 23K. Is this even remotely right? I don't really care how much it costs, but I'd like to figure out if George's car is the better deal or not.

Thanks for reading my 20B-Newbie post!

Brian

87 TII
93 R1 T04S

j9fd3s

iTrader: (3)

the difference between what it would cost you to build one and goerges car are small enough that, unless you want to do the wok you might as well get his.

mike

94RHDFD

iTrader: (3)

www.alamorotary.com has a single turbo manifold and dp for sell for a FD, I think the asking price is $2000 for pair, I THINK.

Attila the Fun

iTrader: (1)

368 rwhp at 14.7 psi (1 bar) using stock rotor housings and turbos. No porting or other internal modifications.

Horsepower doesn't really tell the story, though. 428 lb/ft of torque at the rear wheels feels and performs substantially different than a 2-rotor with the same hp. Ask Brian.

Attila the Fun

iTrader: (1)

Not unless Peter lied to me. At the time the motor was being re-built, Mazda was back-ordered on 13B-rew housings. Peter called and left the choice up to me - wait a minimum of three extra weeks or go with the stock housings. Since I was suffering from rotary withdrawal and wanted my car back yesterday (or sooner), I told him to use the stock housings.

As I understand it, that decision cost me about 100 - 120 hp, but I haven't really noticed any sense of deprivation, so far.

Attila the Fun

iTrader: (1)

A 20B is kind of like LSD - you get flashbacks.

QUOTE]I am trying to research how much it would cost me to make a 20B convertible somewhat similar to George's... I already have a running 87 TII (could use a tranny and diff rebuild) that I could cannibalize for parts to put into a 'vert chassis. I'd just need a 'vert chassis, a 20B, oh, and about a million other parts.

I'd love to buy his car, but I'm not too sure that I want to/can afford to drop that much money all at once into yet another toy! (I work for Worldcom hahaha). Maybe you guys will say I'm nuts... would it be better to just buy his?[/QUOTE]

Yes.

QUOTE] I know that I probably have to add another 5000 for misc crap that will come up. [/QUOTE]

$10,000...and that assumes that you can do all your own fabrication, tuning, etc.

QUOTE] That puts me at about 23K. Is this even remotely right? I don't really care how much it costs, but I'd like to figure out if George's car is the better deal or not. [/QUOTE]

It is. (trust me)

Attila the Fun

iTrader: (1)

Obviously a man of high intelligence and great wisdom.

Attila the Fun

iTrader: (1)

Mine has twin, Electromotive Tec-II units. According to Russ, at Electromotive, the new Tec-III will handle a 20B with only one unit.

Evil Aviator

Oh, in that case I apologize for the misinformation. However, the text in "Part 2 - The Engine" of your web site implies the use of FD housings.

Attila the Fun

iTrader: (1)

In that case I apologize for not being clearer. That section of the website was written before the car was delivered, since many folks on the "Big List" were asking for details. At the time of writing, the intent was to upgrade the rotor housings.

As Burns wrote, "The best laid plans o' mice and men gang aft a'gley." The Mazda back order qualifies as "a'gley".

From what I've been told, I would have gotten more hp, but all of it would have been above 5500 rpm, and I would have lost some of the low-end torque. With the stock housings, the 20B is a torque-monster. 850 rpm in fourth gear is comfortable around-town cruising. (I rarely do it, but I don't worry about it like I did when running only two rotors.)

I want to emphasize that I wasn't trying to embarrass you, just make sure the facts were available to the other folks in the forum.

Greg

HAHAHA, he better throw in a wastegate and oil lines for $2k. Anyways, it looks good

Evil Aviator

Burns also wrote, “Liberty's in every blow.” Nietzche wrote, “What does not destroy me, makes me stronger.” Evil Aviator wrote, "It is impossible for anyone to embarrass me in this forum; only I can do that."

j9fd3s

iTrader: (3)

and i said "how hard could it be?"

mike

Kurgan

Blah blah blah, sell your car in the for sale section

Anyhow, yes, yes you can use 13b-rew or 13bt rotor housings on the engine. OR, you can remove the stock exhaust sleeves on the 20B housings and replace them with 13B-REW or 13BT sleeves, like I had done. If you are going to port the motor, and your 20B housings are good, save yourself $1500 (or more) and just replace the sleeves... but it is a pain in the ***.

setzep

Hey Kurgan how the hell did iyou get the sleeves out of the rotor housings? I've tried to remove the spring pins from a old housing I have here and those suckers do not want to come out! Whats the easiest/least amount of damage way of doing this?

RX-Heven

iTrader: (1)

Which series sleeves would be the the best choice and why? HP/Torque gains/losses @ high vs. low rpm's.

Kurgan

The magic of Don Marvel at Marvelspeed did it... he said it was a BITCH... He soacked them in parts cleaner for over a week, then ground out part of them and eventually was able to get them out. A lot of work (so I'm told, I did not build this engine), but for the DIYer, its much cheaper if you have good housings...

Marvel put 13B-REW sleeves in mine. I honestly don't know what the difference between the 13BT and 13B-REW sleeves is, but I don't THINK it is much... does anyone have a comparison pic, I'd like to see for myself... Should have took some pics of my old 13BT engine before I shipped it off, but hind site is always 20/20... doh.

RX-Heven

iTrader: (1)

I just talked to Rob @ Pineapple Racing (my plates are finally being lapped and other stuff cryo'ed) and he recommended NOT swapping exhaust sleeeves due to the labor involved (he also confirms that it is a major bitch) to remove the spring steel that Mazda uses to hold them in place with. Apparently the risk in screwing something up by drilling out the spring steel is not worth it because most likely you would need a new rotor housing, unless you half-*** it back in there and inevitably end up with a loose exhaust sleeve. He recommends just porting them out with a nice carbide bit (or bits)...carefully.

Kurgan

I recommend that you swap the sleeves or replace the housings REGUARDLESS of cost... unless you have NO plans of using a single turbo. The sleeves are so gay on the 20B that it restricts flow like a ******* potato stuck in your exhaust pipe.

Is you're going to be using the stock twins forever, then the sleeves are ideal... they direct the exhaust pulses towards the turbos through the header in the ideal fashion for stock twins.... i still think you would make more power with stock twins and different sleeves.

RX-Heven

iTrader: (1)

It seems most people agree that the 20B sleeves are too restrictive for a single, but why not just port them out as Rob recommended. Save the money, eliminate the risk, end up with something as good if not better than swapping them out. I will be using a big single on my engine so I am just exploring options.