20b In A Glc
04-11-2004, 01:31 PM
#803
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Join Date: May 2002
Location: California
Posts: 22,465
Originally Posted by Jeff20B' date='Mar 19 2004, 01:48 AM
Hey Mike, you know how your 20B FC actually lost weight with your 20B swap compared to the stock weight of a car in your particular year and options package? Well, I was just thinking my car might break even. Going from 13B to 20B, of course (the piston engine was rather small and probably lighter than a rotary).
Let's compare the weight of the 13B that will spend a short amount of time in the car vs a stripped 20B. First I'll list all the relevant heavy items on the 13B. Then I'll try to compare them to the 20B. Let's see what we can come up with.
The 13B has '74-'78 rotors, which are the heaviest 13B rotors Mazda ever made for a production engine. REPU flywheel which is supposedly 33LBS, which is the heaviest flywheel Mazda etc. R5 side plates were not the heaviest, but not the lightest; I think the intermediate was thicker than earlier ones (it seems heavier than my '73 and '74 plates). '74-'75 rotor housings. Early internal reg alt 50 amp is heavier than later FB and FC alts. Cast iron waterpump with stock cast iron impeller and housing (aftermarket tend to be aluminum with cookie-cutter stamped steel impellers). Possibly JDM Hitachi carb with cast iorn base plate (heavier than a Holley). Stock '74 intake manifold with a 1/2" or so thick mild steel ACV blockoff plate which adds unecessary weight (I'll replace it with a thinner aluminum one some day). Lastly, it'll have a GSL-SE cast iron exhaust manifold which weighs as much as my 20B header, yet is concentrated right at the engine. The battery is also staying up front for the duration of the 13B install too.
This 13B is typical REPU flavor, which is good because that's where it'll be going as soon as I'm done with it here, but it's a little heavier than what would be a good choice for the GLC as far as power to weight is concerned. Sure it could shed several pounds with lighter components, but only a light flywheel would make the engine *feel* more powerful, while reducing engine weight some. What to do? Install a supercharger on the 13B? Maybe in the REPU, but not in the GLC (the shock tower is in the way!).
Let's compare all that to the 20B. No stock twins, light steel flywheel with a 225mm disk and pressure plate, only one more rotor housing, rotor (lightest 13B until the Renesis), 80mm intermediate plate of unknown weight with a stationary gear, a 16cm length of E shaft with one rotor journal, 16cm of 17 or 18 tension bolts, and two extra runner castings on the intake manifolds (four, actually). Even the header's weight is spread over a longer area and further rearward. I'll also move the battery to the back. Even though that's not technically weight reduction, it's a reduction under the hood, where it's needed most.
I still have plans to use the dellorto untill I can afford something better (FI?). Also the cooling system will remain unchanged for both engines (no need to upgrade when these same components adequately cool a supercharged 13B).
So what do you guys think? Do you think the heavy 13B will give me an idea of how the car will handle with a 20B in it? I'm curious how the ride height and ride quality will be. I'll probably need to get some RX-7 springs and spacer them up or something.
Let's compare the weight of the 13B that will spend a short amount of time in the car vs a stripped 20B. First I'll list all the relevant heavy items on the 13B. Then I'll try to compare them to the 20B. Let's see what we can come up with.
The 13B has '74-'78 rotors, which are the heaviest 13B rotors Mazda ever made for a production engine. REPU flywheel which is supposedly 33LBS, which is the heaviest flywheel Mazda etc. R5 side plates were not the heaviest, but not the lightest; I think the intermediate was thicker than earlier ones (it seems heavier than my '73 and '74 plates). '74-'75 rotor housings. Early internal reg alt 50 amp is heavier than later FB and FC alts. Cast iron waterpump with stock cast iron impeller and housing (aftermarket tend to be aluminum with cookie-cutter stamped steel impellers). Possibly JDM Hitachi carb with cast iorn base plate (heavier than a Holley). Stock '74 intake manifold with a 1/2" or so thick mild steel ACV blockoff plate which adds unecessary weight (I'll replace it with a thinner aluminum one some day). Lastly, it'll have a GSL-SE cast iron exhaust manifold which weighs as much as my 20B header, yet is concentrated right at the engine. The battery is also staying up front for the duration of the 13B install too.
This 13B is typical REPU flavor, which is good because that's where it'll be going as soon as I'm done with it here, but it's a little heavier than what would be a good choice for the GLC as far as power to weight is concerned. Sure it could shed several pounds with lighter components, but only a light flywheel would make the engine *feel* more powerful, while reducing engine weight some. What to do? Install a supercharger on the 13B? Maybe in the REPU, but not in the GLC (the shock tower is in the way!).
Let's compare all that to the 20B. No stock twins, light steel flywheel with a 225mm disk and pressure plate, only one more rotor housing, rotor (lightest 13B until the Renesis), 80mm intermediate plate of unknown weight with a stationary gear, a 16cm length of E shaft with one rotor journal, 16cm of 17 or 18 tension bolts, and two extra runner castings on the intake manifolds (four, actually). Even the header's weight is spread over a longer area and further rearward. I'll also move the battery to the back. Even though that's not technically weight reduction, it's a reduction under the hood, where it's needed most.
I still have plans to use the dellorto untill I can afford something better (FI?). Also the cooling system will remain unchanged for both engines (no need to upgrade when these same components adequately cool a supercharged 13B).
So what do you guys think? Do you think the heavy 13B will give me an idea of how the car will handle with a 20B in it? I'm curious how the ride height and ride quality will be. I'll probably need to get some RX-7 springs and spacer them up or something.
04-11-2004, 02:20 PM
#804
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Join Date: Nov 2001
Posts: 2,284
Thanks for unsticking this thread.
I've since gotten the 13B and all the components I mentioned into the engine bay, and it's low in front. I swapped out the ealy internal reg alt with the later one because it's smaller. I also threw on a shorter belt. I hope I won't need to borrow my chopped alt bracket and super short belt from my MG. I bet I will need the low profile air filter assembly though.
I think I've hit equilibrium of the front springs already. It's really softly sprung now with all that weight. The back of the car still feels good though (and it looks lifted hehe). I think I'll get some RB or Eibach springs and also some 1" spacers if the ride is too soft. Those aftermarket springs lower the car like 1", which would probably hit the bumpstops. I can push on the bumper with my knee and cause it to hit the bumpstops already.
The front of the car also feels heavier than the rear with my floorjack. Yeah, I know a light 13B would probably be the best engine for this car, but you've got to admit a 20B is just too cool to not want to do in something this small.
I've since gotten the 13B and all the components I mentioned into the engine bay, and it's low in front. I swapped out the ealy internal reg alt with the later one because it's smaller. I also threw on a shorter belt. I hope I won't need to borrow my chopped alt bracket and super short belt from my MG. I bet I will need the low profile air filter assembly though.
I think I've hit equilibrium of the front springs already. It's really softly sprung now with all that weight. The back of the car still feels good though (and it looks lifted hehe). I think I'll get some RB or Eibach springs and also some 1" spacers if the ride is too soft. Those aftermarket springs lower the car like 1", which would probably hit the bumpstops. I can push on the bumper with my knee and cause it to hit the bumpstops already.
The front of the car also feels heavier than the rear with my floorjack. Yeah, I know a light 13B would probably be the best engine for this car, but you've got to admit a 20B is just too cool to not want to do in something this small.
04-12-2004, 12:50 AM
#806
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Join Date: Nov 2001
Posts: 2,284
Yep. I'd like to get a feel for the weight vs engine output going from 13B to 20B, since they should end up being pretty close (in weight lol). Besides, the 20B is still not ready to even test fire yet (lots of little things to do on it, I know I know), but the 13B is rebuilt and I have enough parts around here to get it running really soon. The only thing that's standing in my way is a radiator mod I'll need to have done at a radiator shop. Everything else has been cheap so far with this 13B install. I even had a beehive oil cooler that had been stretched for a 13B.
04-12-2004, 12:56 AM
#807
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Join Date: Nov 2001
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The oil tube, that is. I've got a system worked out where I'll monitor the oil temperature during the first run of like 45 minutes or whatever it is (gotta look it up before I do the deed). Then once I'm satisfied with oil temps, I'll mount an air oil cooler in front of the rad (can't mount it below due to lack of space) and see if water and oil temps go up with a restriction in front of the radiator. Then I'll line the front of the cooler with tape to further block airflow (to mimic hot air blowing from the cooler into the rad). If it's still good, then I'll know the 20B will be ok with that setup. There's no way I'd use a beehive on the 20B. Also, I won't be pushing the 13B very hard since it's a rebuild, and hopefully won't stay in the car very long if you know what I mean.
04-12-2004, 01:04 AM
#808
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Good old DLIDFIS. It just needs a couple wires and it'll be done. So easy.
You know, I have enough components to have used my MSD 6AL with an FC leading coil if I had wanted to, and could find the room, and were willing to drill through the inner fender well, but I decided against it because the 20B will be fine with 0/180 degree leading sparks and three diamond coils (already installed and ready to go). I won't hook an MSD to two coils in parallel ever again (CD spark, 50% reduced amperage etc). I think I'll save the 6AL for my '73 12A with porting and carbon apex seals (9k RPM!).
You know, I have enough components to have used my MSD 6AL with an FC leading coil if I had wanted to, and could find the room, and were willing to drill through the inner fender well, but I decided against it because the 20B will be fine with 0/180 degree leading sparks and three diamond coils (already installed and ready to go). I won't hook an MSD to two coils in parallel ever again (CD spark, 50% reduced amperage etc). I think I'll save the 6AL for my '73 12A with porting and carbon apex seals (9k RPM!).
04-12-2004, 01:09 AM
#810
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Join Date: Nov 2001
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Here you can see the OMP lines are hooked to the carb and the lower radiator pipe is at a bad angle that points it right at the motormount. If only I had some brazing experience. I don't want to learn on this radiator. I don't have a decent torch either.