high compression rotors on a NA 20b
 

I've read a few other post and saw some hp numbers with a bridgported na 20b but nothing with high compression rotors and a bridgeport. What kind of power could be expected with that setup, and how reliable would it actually be?

Ok honest question here...

Where would you get high compression rotors for a 20b? Or can they be machined? From what I remember the 20b rotors are actually a wider size rotor than a 13b rotor, am I right? Basically is a high compression 20b even possible?

Hmmm, that is interesting. I have seen na 12a race engines that had lightened rotors that I believe were high compression, and bridgported making somewhere around 200rwhp. Rotorsports racing here in NC is making them and they cost about 10k an engine. Brian who owns the shop explained to me that they will last 3 seasons of hard racing....so it got me wondering if a 12a can make that much power what would a 20b do with the same stuff done to it.

you can use the 89na rotors, they are high compression and should go right in

mike

ok, thanks j9fd3s, I wasn't sure..

im not 100% i havent actually done it, but all 13b rotor interchange so why not the 20b?

mike

uhm, never heard anything about that. Maybe for some weird weird reason you are thinking of a 20a (2.0 liter 2 rotor)

Could be it node.. let me see if I can find the page that I saw it on so that I can go check..

Yeah you guys are right the 13b rotors should work, sorry for the mixup, I looked at this page a while ago http://www.alamorotary.com/Rotary%20Engine%20Info.htm where they compare 20b parts to others and I thought the 20b's were bigger somehow, but again I was wrong.

Another question though are the '89s the only year with high compression n/a rotors or pretty much any year n/a 13b rotors will work?

89-91 n/a have the higher compression, think it's 9.7:1??

The Cosmo engines already run 9.0:1 CR.&nbsp The 1989-1991 Kouki non-turbos run 9.7:1 CR's.&nbsp You're talking very little gains (on pump gas) for so much trouble...

You ever TRIED looking for 3 Kouki NA rotors??? :D




-Ted

Actually i've never heard of 3 kouki na rotors. Can you explain their characteristics? Would the gain really be that small on pump gas with slightly higher compression rotors?

RETed is one of the few people I've seen around here who calls them kouki (Series 5, 89-92) and zenki (Series 4, 86-88). My friend calls the diff years of silvia like that.

I gotcha.

yeah i know i went thought heartache to get the 2 that i have

mike

go turbo it's faster

in one of my RX7 Magazines they show a NA 3rotor on the dyno 470 HP

Hmm, let's see... street port the 20B and simply run the stock turbos parallel for 550bhp, or go through all that trouble and expense to convert the 20B into a loud NA and get 470bhp. Wow, that's a tough choice. :)

Well 550hp sounds a little overkill to me, although it would be fun to have. If i'm not mistaken a na 20b would be extremely reliable, and if it can still make 400-450rwhp then thats all I really need for the street. Too bad the conversion is so expensive, I would love to drive around a 20b.

A 400-450rwhp NA 20B isn't going to be streetable due to noise and porting issues. This is the kind of power that Roger Mandeville was making with his 13G GTO 3-rotor race car. I'm not sure what it would cost right now, but Mazda Comp sold their 3-rotor NA for over $42,000 USD back in 1989. I figure that it would cost you at least this much to build one from a used 20B-REW block, but once again I don't see the point since the stock 20B-REW can make more streetable power. George Samuels is getting over 400hp out of his stock 20B-REW with only 10psig boost and full emissions. Pettit makes 550hp reliably with the stock turbos and street porting and 15psig boost.

What about 250hp and 250 ft lbs of torque? Don't want to be the devils advocate but I bet you wouldn't have to open the motor for that. And low end throttle response should be great.
I know the turbo cancels out noise but if its plumbed right with the right silencers and muffler it seems it would sound like any other motor.

Yeah maybe running turbo with low boost would be the way to go, especially if you can pass full emisions. I'm sure it would still be extremely reliable too.

Yes, I think you could get that kind of performance with a NA 20B. Although not very scientific, you can multiply the desired 20B performance by 67% to find the 13B equivalent. For example, your 250hp * .67 = 167hp, which is easily obtainable from a NA 13B. Yes, I know the 20B ports are different, etc., but at least this gets you in the ballpark. Generally, 150bhp/rotor is going to be the max race output for a 13B/20B NA rotary on pump gas unless you are one of the elite rotary gurus like Rick Engman.

The turbo cancels out noise no matter how it is plumbed, although the turbine bypass air going through the wastgate isn't going to benefit from the noise reduction effect. Exhaust noise is created from the high-velocity, high-temperature exhaust violently shearing with the outside air. The turbine wheel absorbs both temperature and velocity from the exhaust stream, which reduces the exhaust noise by up to 50%. My TII didn't have any mufflers on it at all, and it was about as loud as a stock 2Gen NA.

About how reliable is a 3 rotor turbo? About the same as the 13B?

That 470hp number being throw around was from the R.E. Amemiya car that ran PERIPHERAL ports for run those power numbers.&nbsp You can't street something like that.&nbsp Realistically, you're looking at 300hp at the MOST from an NA 20B.



-Ted