Jeff20B

iTrader: (13)

I need to know the weight of the 20B-only stationary gear front-intermediate housing, and if it really is 80mm long. I've taken a tape measure to it before, but can't remember the exact length.

How much do the rest of the extra parts in a 20B weigh? Let's see... extra rotor=9lbs, extra rotor housing=7lbs, extra section of eccentric shaft=10lbs (these are all guesses).

The car supposedly has a 50/50 weight ratio like all Mazda's rotary cars. I've already removed the huge AC compressor, but the power steering is staying. Both are mounted with a cast iron bracket. I'd like to replace this bracket with the 20B's aluminum one if possible (the 20B mounts the PS pump above the AC comp). If not, I could trim the iron one down and shave a few pounds while keeping the PS pump low for better center of gravity.

I'm going to move the battery to the trunk (probably in the spare tire hole) to try to move its weight lower and closer to the center of the car. I'll also stop using the cast iron waterpump of the old 13B in favor of the newer aluminum type (stock 20B or FC). I may even ditch the stock clutch fan, but I'd like to keep it if possible. The tranny will be moved back probably by 100mm and only 60mm of engine will need to go forward. The stock engine location is centered over the front wheels, so this should have a positive effect (fingers crossed).

Do you guys think the car will still have a 50/50 weight ratio after all of this? Do you also think it will be nearly the same weight as a fully stock (with AC) car?

bermuda20b

Weigh the 2 rotor engine you have taken out and then weigh your 3 rotor engine. I is what I did and is a good start. I do have a curious question....If you are going to move the tranny back 100mm and move the engine forward 60mm, how are you going to keep everything together?

Jeff20B

iTrader: (13)

If a 20B really is 160mm longer than a 13B, I needed to absorb that extra length in the engine bay. I saw several threaded tranny mount holes under the tranny hump and was going to use a set closest to 100mm or maybe a set even futher back if the firewall will let me get away with it without too much hacking/cutting/beating with a BFH. The rest of the length would then need to go forward by 60mm. That's why I may not be able to keep my stock clutch fan. Even moving the rad forward will mess up the fan shroud, so a custom one would need to be made etc. The problem with moving an engine forward in a pre-'86 car is that they all used front cover mounts, so I need to possibly reuse it with modified motor mounts. I'd like to add 20B style side engine mounts to the unibody frame and/or the crossmember.

j9fd3s

iTrader: (3)

i looked at a disassembled 20b on monday and that center housing looks heavy, it also looks 80mm.
on my 1st gen i want to keep the ac and loose some wieght, so its getting an fc ac bracket.
the 20b has both wtaer pump hosing patterns so any aluminum one will fit.
if you can move most of the extra weight of the 20b back i think you will be really close to stock in wieght distribution.

mike

Jeff20B

iTrader: (13)

Thanks for the info!

Do you know if an FB cast iron water pump would fit? I only ask 'cause I think it's lighter than the old style and I've got one sitting here. I'm planning on an aluminum one, but to save money, I'm going to at least test fit it to the engine first.

j9fd3s

iTrader: (3)

the only difference between 74-85 and 86-02 is the alternator bracket bolt. i know when put the later pump on an early motor you seal the hole and put a helicoil in it. i think going the other way you dont have to do anything, though

mike

Jeff20B

iTrader: (13)

It'll be great to find out! Man, your info has been extremely helpful! I just hope my experiences can help you with your project in some way.

peejay

If by 50-50 you mean "anywhere from 49/51 to 55/45" then yes RX-7s have 50-50 weight distribution.

I really doubt that the pre-RX-7 models had anywhere near 50-50.

I say don't worry about weight distribution too much... static weight distribution is meaningless unless the car is sitting still. I tend to enjoy my cars when they are in motion

j9fd3s

iTrader: (3)

[QUOTE]Originally posted by Jeff20B
It'll be great to find out! Man, your info has been extremely helpful! I just hope my experiences can help you with your project in some way. [/QUOTE

i'm done with mine, hopefully in the next week or so i get to find out about this 50/50 thing...

mike

Jeff20B

iTrader: (13)

Lol peejay, I was just going by the the door frame thing that lists GVWR and GAWR. It listed front and rear as the same weight, while on my REPU the front was way lighter than the back. I've seen RX-7s with the same weight front and back too. I know it's pretty much a suggestion instead of a truth, but I'd imagine it to be fairly close to what a four tire car scale would say.

j9fd3s, let us know!

j9fd3s

iTrader: (3)

oh actually i need a revlimiter for my 1st gen, at the track we had it spinning way over 8k. it doesn't really seem to mind that much though

mike

Jeff20B

iTrader: (13)

I went ahead and weighed a bunch of stuff to try to get an idea of how much heavier a 20B will be than the '76 13B it's going to replace. All weights are in LBS.

13 2nd gen 13B rotor housing
14 12A eccentric shaft
9.5 13B rotor
5.5 '74 13B intake manifold
28.5 '73 RX-2 rear side housing (the heavy one)
5? stationary gear
75.5 grand total

I didn't have a front stationary gear handy to weigh, so it's only a guess. The 20B's intake manifold is large but probably mostly hollow. Aluminum can't weigh all that much. The extra sheet metal in the oil pan is neglegible. Am I forgetting something?

I've heard stories of people saying a 20B weighs some 200LBS more than a 13B. Can that be right? I'll be stripping the 20B like everyone else. With the removal of the Cosmo's AC compressor and lines (and soon the condensor) and moving the battery to the trunk, that 75.5LBS of extra weight up front should come in close to the amount taken out. I'm going to weigh some removed AC parts and the battery whenever I can.

j9fd3s

iTrader: (3)

it feels like 200lbs more when you put it in the car.....
its probably the wieght of a 13b with the rx3 steel (i have one i know) and another rotor, rotor housing + the extra stationary gear.

mike

Jeff20B

iTrader: (13)

So it probably is right at or around 75 extra LBS? Man, I wonder if the car will be lighter after the 20B is in? I suspect it will be, but I still can't believe it.

Oh yeah, I forgot about the thermal reactor's weight compared to the 20B's turbos/NA header. Do you know how much the turbos weigh? I bet I'll save a decent amount of weight right here.

Is the reason the 20B feels heavier in the car due to how it fits in an FC? The tranny doesn't get moved back, so all the weight goes further forward in the car. I'm planning on trying to move most of the engine rearward as much as possible in my car. Do you think it will feel like 200LBS?

j9fd3s

iTrader: (3)

dude its gonna be lighter, ive lifted thermal reactors before, that thing wieghs as much as the engine! the turbos were heavy, maybe 50-60lbs. one of the reasons it feels heavy when you put it in is because its longer enough that you can't jump in the engine compartment and wiggle it around like a 13b. you have to do it from outside, your back will thank you

mike

Jeff20B

iTrader: (13)

Whew that's a relief! My hood pops open from the back so I may not need to remove it. I didn't need to remove my REPU's hood for engine removal, so I'm hoping I can get lucky again. There's no room to jump in there though. Or maybe there is...

j9fd3s

iTrader: (3)

i haven't taken a hood off (except for the 20b) in years. there is no reason too, it slows you down.

mike

Jeff20B

iTrader: (13)

So the stock turbos are like 50-60LBS? Ouch! I suspect a single large utrbo would be quite lighter. Lighter still is just an NA header.

Heh, I forgot about the airpump. That ought to save a pound or two, heheh.

peejay

If removing four 10mm bolts slows you down, how many weeks does it take you to remove the engine?

it's four bolts. Mark it and remove it just to get it out of the way...

Besides, if you don't remove the hood, then you won't be able to go on that first road test with the hood still off I think that might actually be mandatory for an engine swap. I'll have to check the Gearhead's Etiquette Manual...

j9fd3s

iTrader: (3)

its no fun to drive a 1st gen with no hood, all you can see is the radiator cap. it slows you down because you can be doing other things than taking the hood off, and it wont get damaged sitting arounf the shop either

mike

Jeff20B

iTrader: (13)

My MG Midget project hasn't had its hood on for quite a while. I'll be doing a first road test hoodless

Jeff20B

iTrader: (13)

I got a pretty good look at an empty engine bay of a CD Cosmo yesterday and I'll tell you that a school bus V8 could fit in there! Well, it might not fit under the hood, but length and width would be ok. I also don't expect any sway bar problems either.

I still haven't weighed those AC parts. I'll make a list when I've gotten them all out of the car and add them to the rest of the old stuff I've removed. I'm also thinking of getting a T2 tranny because my auto is acting up. Anyone know how much lighter a T2 5 speed is than the old school autos? Just the starter alone is worth 5LBS! Man, this 20B install will make the car lighter.

j9fd3s

iTrader: (3)

we measured up an 86 b2000, and a 60's mercedes, for a 20b. the truck is really tight, no room at all for an ic, the benz has tons of room....

mike

Node

iTrader: (1)

a 20b in cymfc3s's mercedes? LOL
sleeeeeeeeeper

Jeff20B

iTrader: (13)

I've taken some pics of an '86 B2000 with a 13B in it. They'll be on my webpage soon. The way the engine was put in there, it left tons of room between the pullies and rad. I think it's around 160mm or so. My friend held a dollar bill between one of the pullies and the rad to let you all get an idea of how much room there is. Hmm, a dollar is about 156mm and there was still space on either side of it. If the front cover style mount can be converted to side mounts and the oil pick-up tube's mini sump won't interfere with the centerlink and/or swaybar, then a 20B can fit in my friend's B2000! Heh, a B2000 with a 20B in it... that has a nice ring to it.