Okay, first let me point out I am a rotor head through and through. And I won't ever change that... and I might get shot for even bringing this up but...



20b vs V8? There are more and more rx7 conversions to V8's out there. V8 is substantually cheaper and easier to get. Other than the point that one is a 20b and the other is a V8 (and this is a rotary forum), why would someone choose a 20b over a V8 (intellegent comments please... oh what the hell throw in the catty comments also https://www.nopistons.com/forums/pub...R ).



Of course I currently own: 20b, S6, S5, S5t2, and S313b. But I also recently picked up an Audi B6 S4, and that V8 puts out 340 hp of smooth running, high reving, torque producing joy! ... it is not your old 289, 350, or 454.



Thoughts? Just for discussion (I digress to my first point, that I am not looking to change... but someone might be)

I am surprised no one has an opinion on this matter... I am sure the title of this forum is "NoPistons"! and I know this topic is not about "toast" or something truly meaningful https://www.nopistons.com/forums/pub...#>/biggrin.gif . But there must be a reason not to switch over to cylinders!

V8s have a lot more parts, configurations, mechanics, aftermarket parts, etc. available to them.



I don't own a 20b, but there's a start.

And with more and more V8 adaptor kits (other than to an rx7 tranny) it allows you to take advantage of the readily available V8 parts!

One major factor is budget. For 10k you can have a nice v8 set up and it take 30k to have a nice 20b set up.

90% of the rotary comunity is on a tight buget. So v8 are in favor just beacuse off this reason. They all want 500hp rx7 but with a rotary platform becomes verry expencive.



I personally like to have unique toys.

I think that's it in a nutshell. Anyone can make a V-8 RX-7, and do it more cheaply than with a 20B, but a 20B is "different". The same things that draw people to the 13B are present in the 20B, and in greater amounts.



It's all about "The Road Less Traveled".

I like the unique aspect aswell!



The other big thing is "the smog man". You can always pass a car with a US motor to the newest year of the motor or chassis.



What about weight distribution? I know the 20b is heavy also, but?



I am surprised this conversation seems to support the V8's....

In a way that's my argument FOR the 20b. How many moving parts are there in a 3 rotor engine? The rotors and the output shaft. A v8 has 4 valves per cylinder, rocker arms, valve springs, pistons, rods, etc. There's going to be much more to break in an engine with dozens of parts. The rotary does have the issue of having the combustion stroke heating only a certain part of the housing, but there's one thing that is also key here. A 20b will rev like a beast. The v8 will rumble, it's like a Harley, but the 20b will scream like an F1 car. Tell me you would want to hear a lazy v8 instead of a rotary whenever you put some weight on the throttle.

Me likey 20b https://www.nopistons.com/forums/pub...IR#>/wacko.gif ....

For someone who's been building (and rebuilding), tuning, and flogging 13b's for a few years the 20b is simply the next logical step. It's different from a 13b, but not as drastically different as a v8. An example of a good fit for a 20b would be someone who has a turbo/port 13b with existing cooling, exhaust, oil, fuel, spark, drivetrain, and ECU support mods. For someone in this position, the sale of the unusable 13b-specific parts would bring the cost of a 20b swap down significantly. If you've got an unmodified car and no experience, a v8 may be the right choice for you.



I'm not sure what the motivation is for other guys, but I've got lots of rotary-specific parts/tools and 6 years of trial and error with a 13b that can be applied to 20b. Not to mention my preferred vendor (where I take stuff when I'm in over my head) is pretty much rotary specific. Also, I would never have found a modern aluminum v8 for what I paid for my 20b. Although I'll grant, I got a good deal.

When I did my 20b (which is still an ongoing project), I got a great deal. I picked up a late model complete long block for low $2k's, I also picked up a t2 tranny and modified my driveshaft. I agree with already having the rotary tools and knowledge, but I was able to do this for cheap, respectively!



Anyone could go get a crate V8 throw a carb (or fuel injection) for cheap and have reliable power. I believe the rotary is about "finesse". It is intelligent design, that takes smart thinking and design to create a platform to place this power plant. The V8 is about dumb brute force (reminds me of the redneck saying , "uh there is no replacement for displacement"... I apologize to any rednecks reading this... if they could read it https://www.nopistons.com/forums/pub...IR ). One thing I do not like about the V8 conversions is the tranny (everyone always throws a big honking hurts shifter and cuts the tunnel or the dash to get it in... not very refined). Has anyone seen an adaptor that connects to the Mazda Bell housing?



But what if finesse and refinement is part of my argument, what would you say if the engine swap was with a BMW V8 or even V12, or my Audi S4 4.2 V8 (it has a rumble, but it has refinement and high revs). Additionally modern cylinder engines are reliable...



I digress to my first point, I am a rotary guy! I love the motors, and I do this for fun! In fact I look at other cars and try to assess how well they would do with a rotary instead of cylinders.

It also reminds me of high school, mid 80s 13b's (S4's and GSLSE's) against 5.0 mustangs... what a great rivalry!... until they had to shift!

for my sports cars this is the only v8 I would consider



http://thekneeslider.com/archives/2007/07/...8-liter-455bhp/



u can also slap couple turbos to it

i think the main reason to go v8 is the power is more reliable. Some people have gone through 3, 4, 5 + engines, granted this is speaking 13b. I think the 20 b community is more careful, i also think the 20b is probably more reliable then a 13b. Though i think an ls1 or so is still more reliable.



Now someone may argue yeah but look at power/liter ratio, and while that is impressive to get so much power out of a small package it should actually be a weight/power comparison in which case the v8 would come out ahead especially when reliability comes into play. The rotary engine was designed to wear out and needing to be rebuilt, there is really no way around that.



I think the rotary engine is a badass little engine, which is why i still have mine, though if it blows up or needs to come out again im really thinking of going LS1. 20b is just too expensive for my pockets and if it blew you're looking at another engine and a half rebuild price.

Re: 20b vs V8
 

I think I remember someone posting about a 100lb weight gain from a stock 13brew to an LS1. So if you are going big power, you are going to need a beefier trans anyway. Most people are going with t56 right? I dont know Ive been out of if for a while. So less weight with an LS and a trans ready to go. I have a 20b from a cosmo clip. Had good comp #s, but I broke it down for storage and the center rotor is trash. Thats a costly rebuild for just the kit alone, now I need a new rotor and housing. At some point the trans issue will arise.
LS is not an engine to laugh at. You can build them to rev sky high and still go forced induction. ZR1 has 650hp with a warranty. You really cant beat that.
I will still build the 20b because;
I like the engineering in a wankel.
I like the sound.
I like the simplicity.
BUT when I look at superlite coupe and other serious projects I would only consider a LS, or maybe radicals approach. V8 from hyabusa parts. Ohh ohhh. Now that V8 puts the 20b to shame.

Re: 20b vs V8
 

I got a first gen which I feel is the most common rx for the v8 swap. Now don't get me wrong, I love the v8 and the torque that comes with it, but putting anything other than a rotory in a Mazda seems sacrilegious. Its kind of like putting a GM 427 in a Cobra, you just should not do it.

If I was to put a larger motor in my car it would have to be a 3 rotor 12a, just to keep it first gen. I found this while surfing one day.
http://www.hurleyrotary.com/page.php...ntpageref=6264

Re: 20b vs V8
 

10a vs 4 cylinder

12a vs v6

13b vs v8

20b vs v10

26b vs v12

therefore if it was me and i wanted to whip my neighbour in his v10 id be looking into a 20b whereas if my neighbour had a v8 i wanted to whip id be racing him in my 13b. notice as my list starts it basically means the years as they bought out rotary size specific engines to compete with general production piston engines, minus the 26b that never came out for us to buy damn.

Re: 20b vs V8
 

The 20b is an over priced engine, but someday I too would like to build one. The car I'm building now is a 6port turbo holley carb. I'm soon upgrading to a msd 6al programable for my leading. I don't use trailing ignition. I have found no benifit using trainling ignition with an msd. The fully programable ignition will give me better on/off boost prefomance on the street rather than locking my distributor at 10btdc.

I'm not sure but I think I can use a waste fire setup on a 20b. I think 2 rotars are in sync and 1 is 180 out. Using a stand alone ignition and a carburator would lower the cost of a 20B significantly:)

Re: 20b vs V8
 

As for the v8 swap. The lsx is not only a great engine but the t56 has two overdrive gears making it the only swap that could actualy work in an rx7. Al other motors including the 2jz lack the proper transmission gearing to make the swap any good, they would be screaming at 70mph. I feel the rx7 biggest problem is the transmision gearing. I feel like I could pick up a lot of time just by using a close ratio gear box. I'm currently looking for a good affordable upgrade. The lsx is a challange to beat in any type of racing but its my goal to beat it in everyway:) I've never had problems beating lsx's in camaros but now my 1980's 1.3liter is competing with modern lsx v8s in the same car. I've made an excel spreedsheet, type in tire size, trans gearing, rear gearing and engine rpm and it translates it to mph

Current goals for my car 450whp street port blowthrough set up, tall gearing 25+mpg. This is my third build and they say "third times a charm".