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Index > @ the Pickup Bed (General Topics) > Thread: Rotary swap
Thread: Rotary swap [' This thread is 2 pages long: 1 (2) ']
Klaus43


Rotorhead
Posts: 1259
posted June 15, 2004 03:06 PM

Low-end grunt???

From a wankel rotary? Better spring for a supercharger...
(Or, just gear down and wind it out!)

       
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1repuwannabe


1st Gear
Posts: 26
posted June 16, 2004 12:33 PM

oops i know that rotaries don't have low end grunt..( smacking head against wall). they are able to turn outrageous rpms based an thier design and the fact that they have only 7 moving parts, no valves to float etc. klaus can you tell me what kind of hp i can expect out of a 12a or 13b motor. my present engine has a aluminum head and a cast iron block, 8v, 2bbl carb.

       
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brad


Rotorhead
Posts: 1672
posted June 17, 2004 10:36 AM

quote:
oops i know that rotaries don't have low end grunt..( smacking head against wall). they are able to turn outrageous rpms based an thier design and the fact that they have only 7 moving parts, no valves to float etc. klaus can you tell me what kind of hp i can expect out of a 12a or 13b motor. my present engine has a aluminum head and a cast iron block, 8v, 2bbl carb.


rpm's aren't too outrageous. 12a motor 8000 redline. 13b less, mabye 7k-8k depending on year of motor.

stock repu 13b 4port made 110hp @ 6000rpms, 117 ft/lbs @3500rpms. a good well built streetported 13b 4port with big carb and exhaust can make 220hp at the flywheel. 230+ with big chokes and no mufflers.


____________
-brad-
74 REPU Lawn Green
81 Rx-7 racecar. 12a J-
Bridge

       
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Klaus43


Rotorhead
Posts: 1259
posted June 17, 2004 11:09 AM

If price is no object...

...you could probably port and bolt together up to 300 HP... but that wouldn't come without a commensurate price tag. Besides, then your chassis has to accommodate all that extra power effectively...

       
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rotarydave


Hauling
Posts: 108
posted June 17, 2004 11:56 AM

You were talking about numbers what you can do where things can go.... here are some of the dyno numbers from our engines that we did at Atkins Rotary......

These engines were originally built for specific RPM/HP/Torque numbers like generators, boats etc but this shows the numbers these can do and potential.

this is the worst one of the bunch
12a stock porting 7 inch supercharger 390cfm Marine holley

output 12lbs boost
max torque 156 ft/lbs @ 6700 rpm
max hp (flywheel) 225 @ 8000 rpm

13b 6port stock porting (86 NA rebuilt block)5 inch supercharger 390cfm Marine holley

output 11 pounds of boost
max torque 196 ft/lbs @ 5800 rpm
max (recorded) hp (flywheel) 264 @ 7600 rpm
test (target rpm was 7200) was concluded at 7600 rpm hp numbers had not peaked

13b 6port street port (based on 86 NA block) 7 inch supercharger 390cfm Marine holley

output 9 pounds of boost
max torque 178 ft/lbs @ 7200 rpm
max (recorded) hp (flywheel) 276 @ 9000 rpm
test concluded at 9000 rpm hp numbers had not peaked target rpm was 8500

Note that all of these engines were using "SMALL CARBS", all of these engines are fully capable of running past 8k rpms of course you don't want sustained runs past this but they can handle the occasional blast if it is a well built engine. I am currently using a 13b with a supercharger bought from a fellow forum memeber here is the info on it and what i am doing with it

http://www.mazdarepu.com/board/viewthread.php3?FID=6&TID=821 orig thread

Remanufactured 13B - '86 type block with early front cover, S/C fitting in front cover. (stock porting)
New Wrapover manifold. (s/c manifold)
New Oil Pan & pickup - REPU pan.
New Waterpump and Housing.
New Complete Dual Electronic Ignition System.
New Holley 390 Carb. with Electric Choke, throttle bracket and clamp.
New K&N Air Filter and Housing.
New Air Filtering Lid.
New Special Clutch Kit Package: High Performance Clutch, Throw Out Bearing, Pilot Bearing, and Seal.


I put this into my 74 Rx4 never dynoed it it does not have anything special on the inside either it is a stock 86 type block. On the track i am currently doing 14s in the 1/4 mile with all of the stock drivetrain (no LSD) I am launching at 4000 and shifting about 9500 the only problem i have had is fuel delivery (need bigger fuel pump)

i hope that this helps and i will post other numbers as we get them

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1repuwannabe


1st Gear
Posts: 26
posted June 17, 2004 03:22 PM

great numbers!!!!! now i need to get with the guys who have experience with my kind of swap. i can get a 12a from the junk yard for 160 and a tranny for 60 what do i need to look for??? i have a 79 courier any idea what dimensions are for the motor mounts of should fly by the seat for my wallet???

       
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rotarydave


Hauling
Posts: 108
posted June 17, 2004 04:04 PM

check the other thread over in the engine section i posted some ideas there

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1repuwannabe


1st Gear
Posts: 26
posted June 30, 2004 11:05 AM

how is it going?

hey b1300 and you other guys doing the swaps. how are they going?? i'm still doing research for my project and need to learn as much as i can.

       
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thestilettoman


Newbie
Posts: 6
posted June 30, 2004 01:06 PM

Rotary Swap Suggestions

I am not the expert like RotaryDave from Atkins - those guys do this for a living. But I have done several swaps and built a few rotaries, may have some useful suggestions.

There are many refits available using Weber, Holley and Dellorto carbs. I like the stock carbs because they start and run really well for normal driving. I built a ported 12A for a 1984 RX-7, and made a simple adapter for the RX-4 (13B) carb. With street porting and a Racing Beat header, we measured 130hp at the wheels, which is about 155-160 at the flywheel. Unless you are going for all-out power, I recommend you consider what I did: Use the Racing Beat or similar template to port the secondary intakes, just clean up the oval shape for the exhaust, and likewise clean up the primaries BUT DON'T ENLARGE THEM. This gives you good low end and drives like a stock motor until you put the hammer down and the vacuum secondaries open. I removed one coil from the spring in the vacuum actuator for the secondaries, to get them open sooner. I also altered the bleed port for the vacuum actuator, RotaryDave can probably explain that better than I.

Having said all this, I strongly recommend a 13B for the truck, as it is much heavier than the early RX7 or RX3, and you really need the torque. All my comments about the porting apply equally to the early 13B, but you must know which intake you are using before you do the porting. Some years had the primaries in the center housing, some had them in the end housings. RotaryDave can probably tell us which year manifold had the bigger runners, I just can't remember.

I am sure some will disagree with this, but I think any NORMALLY ASPIRATED early style rotary with more than 170-175 hp is going to have poor driveability for daily driving, especially in a truck. You probably won't like the gas mileage either. If you want more power than that, put in a V8. It is cheaper, more reliable, and driveability is not an issue. I am getting 18 mpg with my 84 RX7 with a 300 hp Ford 5.0 V8, and I drive it pretty hard.

I have a well engineered adaptation of the brakes and hubs from a 1990 RX7 convertible in my 84 RX7, front and rear. The stopping power is outstanding.

I also built the white extended cab REPU in the photo gallery, and a 13B powered 1980 GLC, which I drove for over 100,000 miles. My homemade convertibles are shown at rx7.org, under Feature Car, September 1997.

I can provide photos and more details if anyone is interested in my projects.

thestilettoman@msn.com Located near Seattle
____________
stilettoman

       
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Jeff20B


Moderator
Posts: 661
posted July 01, 2004 02:14 AM

You did a GLC? We need to talk.
____________
'74 REPU
'76 Cosmo
'77 MG Midget 13B
'81 RX-7

       
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rotarydave


Hauling
Posts: 108
posted July 04, 2004 04:18 PM

I am not nearly the expert you think i am, but i would have to agree with many of the things that others have said. I know that for everyday driving a nice ported and polished 13b 4port with a Holley kit is awesome, you still get good mileage out of it and have the power to get on it when you want to. I am not a fan of the Dellortos although there are many others who are, it does allow you to use a 6 port motor over an older 4port, Racing Beat did make a kit for the Holley and the 6 port but are currently not selling that kit due to problems with the secondaries on the carb they were using. As far as what combination of housings/intake provide you with the biggest porting in stock configuration I am not really sure right off hand, all of the ones we have built lately we started with Rx7 12a plates because of the gas nitriding. I have to go up to the shop here in a little bit to do some work on the bosses airplane and i will look at the housing stash and see what i come up with.

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