GlennStile

Hello People

Im building a lotus 7 clone and am planning to use a rotary engine due to their low weight, high power output and small size.

The question is which one to use 12a, 13b ... what are the pro's and con's of each engine.

Thanks

Glenn

PS Im a turbo nut so whatever i use will be turbocharged.

PPS I also build / reprogram my own ECU's so it will also be fuel injected.

Scalliwag

If you can build your own ECU's and you want to go with a car as unique as a Lotus replica, go with a 20b (3 rotor) With a completely fabbed intake and exhaust/turbo header you can really make that motor look great and run it's *** off too!
A 12a would be lame to install in a car like that

mkoch1

Check with http://www.hurleyrotary.com/ I belive they are over in your neck of the woods. If you are in england you should be building and Ultima

drago86

definatly go with a 20b, periphreally ported either a large single or 3 smaller turbos (racing beat style) busted to some insane amount with a 250 shot of nos in there,.. ok, but seriously now, go with a 13b, depending on your funds you can get either an one out of a fc s5, or and fd, both can be had imported from japan from about 700- 2500 (fd will be more expencive) go with some sort of standalone liek a haltec, and a good streetport should do it for ya, and give yuo a chance to freshen up the internals aswell. Or if you have the funds just buy all the parts new and put it together. It also depends on how much hp you want out of it.

RecKleSs

Go with the 13B engine with stock 2mm apex seals. You might as well take advantage of street porting the engine before putting it into the car. The 20B will cost too much money and getting it to fit will most likely be harder. Your project sounds great and good luck.

Bridgeported

Well it comes down to how much power you want to make. A 13B would most likely be more than enough.

Scalliwag

Jeez guys! This guy is building a Lotus replica and has the knowledge to build and program ECU's.
It is not a matter of a 13b having plenty enough power.
I have read in another thread that this guy can program in most CNC programs and even has access to 4d equipment.
If anyone in the forum has ever been a candidate for a 20b it should be him.
Think of how wicked that would look! Besides, we're spending HIS money!

Evil Aviator

I don't see much advantage in the 12A engine. The 13B is just better overall, especially with torque, and it comes with easily-available fuel injection manifolds, turbo manifolds, and throttle bodies. Even when you can fabricate everything yourself, it's just so much easier to buy off the shelf when possible. The 13B-REW block is probably your best bet with an aftermarket turbo and manifold, assuming that the strange mounts are not a problem.

The 20B is a great engine, but I'm not sure if it will lend well to the concept of the Lotus 7. However, a turbocharged 20B would be the way to go if you want to build an American-style car with loads of horsepower up front, which would make your car something like the old Lister-Corvette cars. The Viking can accept a 20B.
http://www.laminarauto.com/

As stated earlier, you would probably gain more insight from asking Hurley about suitable powerplants.

80-CU.IN.T

Awesome combo. "13b W/ turbo." ( The 20B is too heavy.)
The lotus 7 is my third favorite car. Modified with a rotary, not much would be able to touch you on a road course. A perfect example of this is in the latest Sport Compact Car mag. Someone is already doing it.

First favorite is the LOTUS SPORT ELISE. Not availible is the USA. The swap I would like to do is now being done. I saw a grey one at the last Los Angeles Auto show with a Jap spec Honda in it. When I talked with the guy who is doing the swaps, he told me that he had already contacted Mazda for pricing on the New RX8 engine. He wasn't sure what he would use for a transaxle though.

My second favorite is what I currently own - Fd3 w/ single turbo.
"Please post pics of your project. During and when finished"

The power per weight ratio will be around 5LBS per HP. Very, very fast for a street car

Scalliwag

The horsepower could more than offset the weight. If the two rotor could outperform 3 and 4 rotors then the car that won the '91 LeMans should have had a 13b instead of a 4 rotor.
That's it!!! He needs a 4 rotor!

80-CU.IN.T

LOL - The Lotus 7 is very light. Getting 50 / 50 weight distribution with a 20B would be difficult. Why not use a 350 Chevy instead? Believe it or not the Chevy is lighter. 13B has one of the best power per weight ratios period. Turbo charged it is amazing and simple. I put down 379 RWHP in my RX7. Power starting as soon as I give it gas / any RPM. Small turbo ( RX6A) I could have made a lot more power with a larger one. ( NEXT CAR ) After I fix my side seal and with a few changes I should be able to make over 400 RWHP on 91 octane pump gas. " 1.3 liters Frigin awesome " And extremely light.

1800 pound lotus 7 with driver - 400RWHP = 4.5 LBS per HP. "Scary fast for a street car

GlennStile

Thanks allot guys

I did consider using a 20b but believed that the weight would start to become to much of an issue.

Like scalliwag says, I have the facilities to build just about anything and but as I have found HP is not the be all and end all of building a car.

I have built FWD street cars with over 350bhp and in our wet(ish) climate they are not the best things to drive. still great on a dry day

I think it's gonna have to be a turbo 13b, 400RWHP should be plenty since im looking at a 1400lbs max weight+ little old me.

BTW we get 98octane fuel over here straight from the pump, gotta be some reason we pay so much

80-CU.IN.T

98 octane 400 RWHP no prob.

lotus 7 w/ driver 1600 USA pounds
13B 400RWHP

4 USA pounds per HP. And it goes extremely fast around corners too.

protlewski

just make the fuel system really beefy because that is what happened to that srx-7 in SCC febuary issue. On the track it had fuel starvation. But it did manage to pull a 1.157g's on the skid pad.

GlennStile

trust me , i know all about beefy fuel systems

on one of my cars i run a 2 fuel system , basically pump
fuel and staged toluene injection.

Its allot cheaper for me to buy 114octane toluene than it is to buy pump fuel. you guys just dont know how good you have it

Scalliwag

How much does the stock motor in a Lotus 7 weigh?
I would think that the near 50/50 weight ratio is calculated with a motor in it so that would be good to know.

Scalliwag

Here is a cool link to a rotary Lotus http://www.myhreco.com/lotus/index.htm

GlennStile

Scalliwag : There isn't really a standard engine weight for a seven, they have been built with a huge range, caterham build them with k-series rover engines but also with hayabusa and firebird bike engines. The JPE was a very quick se7en built with a Vauxhall(opel) 2 litre 16 valve engine with 250bhp basically the lighter the better.

That's a really handy site, I haven't seen any detailed info on the net about rotary se7en's

and see,(80-CU.IN.T) I told you 1400 US Lbs

80-CU.IN.T

Scalliwag -

I don't know the weight.

I owned a 1965 Lotus Cortina. Same motor 1635cc. It put out 163 RWHP. ( Very Modified) The car weighed 1685 LBS. wet with me in it. Very easy and fun car to race. The engine was in and out regularly. I wasn't competitive. Driver error. I could pick up the engine and put it on my bench with no prob. I was stronger then. I can pick up my 13B and put it on a bench also, just not as easily now.

KneeDragonR1

If it had to be rotary, I would use the 13BT.

It is a relatively simple beast that is capable of good hp. Parts are reasonably priced and readily available.

With a stand-alone computer and large single turbo you would be set.

A 20B would be nice, but the added complexity may approach a level of diminishing returns.

Non-rotary I would cop the Westfield plan and use 2 Busa engines for a 2.6 liter 8-cylinder. Technologically the Busa engine is superior to the 13B. If needed, several turbo kits are also available.


KneeDragonR1

ShortBusRiot

SHHHHHHH come on man i havent got it yet

Evil Aviator

The reason you pay so much is because of the punitive taxation practices of your government which we had the guts to revolt against over 200 years ago.

Your 98 pump octane is most comparable to the US 93-94 pump octane. We have to use a different octane rating system than the other countries because, well, just because. Seriously though, the US uses an average of the Research Octane Number and Motor Octane Number to arrive at what we call the Pump Octane Number. The PON is actually a better indicator of quality control, despite the fact that it confuses every other country in the world.

GlennStile

I did think of using a couple of hayabuse engines but at approx £3000 each the cost outweight's the benifits.

I have been offered a re-built turbo 4 port 13b for aprox £200 (very good price)

Bridgeported

Wow! That's about $329 USD for those wondering. Hook me up if you decide not to buy it!

GlennStile

I know, i Know. The tax on fuel here is a complet rip-off, over 70%!.

Regarding RON/MON we actually use the same method.
European standard EN228 this corrisponds to the US ASTM D439 standard. The Research Method and Motor method are standard across all international standards (DIN 51 756; ASTM D 2699 and ASTM D 2700).

The PON standard (RON+MON)/2 is what you see on the yellow decal on the pumps at the gas stations and represents an average of the two but i wouldent say it's a better indicator. For racing terms MON is the best guide since it is tested preheated with varing ignition timing and higher engine speeds.

but regardless the additivies i use (such as toluene) push the RON, MON and PON values up allot and lower the cost :P