jimlab

As I mentioned before, because it's a "different" design, Mazda was able to sell the SAE on calculating the rotary engine's displacement based on only one rotation of the eccentric shaft, effectively underrating the engine's displacment for tax purposes.

If you define displacement as the firing of all combustion cylinders/chambers, then a 13B's displacement would be 3.9 liters (6 x 654cc) over 3 rotations of the eccentric shaft. However, since piston engines fire all cylinders on only two rotations of the crankshaft, equivalency is more closely approximated by adjusting the displacement of the rotary for the same number of rotations. Since 4 chambers are fired during two rotations of the eccentric shaft, a 13B is more closely equivalent to a 2.6 liter (4 x 654cc) piston engine.

Show me a "geared" 6 cylinder engine. Why do you insist on trying to make this as difficult as possible, when it's really quite simple?

I'm sorry, but the way you look at it has no relevance here. The way governing bodies in racing look at it is probably what you should pay more attention to, and they typically double the displacement rating of a rotary for the reasons I've explained.

BASTARD

iTrader: (4)

I think we all get the point that you love your LS* motors... good for you , they are nice engines... no doubt about it

but how many times are you going to aruge the point... seems like every forum all you do is bitch about how the rotary engine is under rated in displacment and over rated in its abilities... do you just copy paste...I think we are all tired of your rambling

p.s.

My ATM card has zero moving parts and every year it's abilites increase... go figure

jimlab

To you, it isn't. Let's be clear about the fact that you're judging the viability of an LS1 conversion based on your own financial status.

Actually, magazine dyno tests have proven that LS1 crate motors can produce 39x horsepower out of the box. Cam and head LS1s regularly put down low 4xx RWHP. A crate LS3 (436 SAE rated horsepower) with a cam and long tubes just put down over 500 RWHP.

You're placing far too much emphasis on ratings and not paying any attention to what real-world results are.

jimlab

If you don't like it, stay the hell out of the OEC forum. It's pretty simple, really.

slo

iTrader: (1)

Its fully possible to build a 400+ whp 13b that lasts over 100K miles between rebuilds, but you would have to be pretty lucky for it to actually happen, as a minor failure like a fuel pump or even a bad tank of gas can grenade the engine.

The limiting factor of how long a relatively high HP turbo or non turbo Mazda rotary lasts, if nothing goes catastrophically wrong like a major overheat, bad tank of gas that doesn't get noticed in time etc, is apex seal and rotor housing wear, and the stock parts could certainly do 100K. With GOD on your side or the correct alignment of planets and stars if your so inclined, its possible that you could exceed 100K miles of regular abuse.

With ceramic apex seals which basically don't wear out and don't significantly wear the rotor housings you could probably go much farther.

Some stock 13b-rew's last over 100K, which is truly amazing as there are about 15 minor failure points that would lead to total engine failure. Mazda fucked up on lots of the details of the 13B-REW, that they got right with the 13BT.

Ive been looking for a deal on an LS1 for a Miata swap project for some time, on the west coast the best price I have seen was 3K for an engine and trans that had lots of miles and was one of the earlier engines.

Maybe I should put the 13b-rew in the miata and put the LSX in my FC..

Roen

iTrader: (2)

Just find a 3.9L 6 cyl and adapt a custom output shaft with a overdrive gear in it. (Just to be facetious). Or, change the r&p gear to compensate (i.e. from a 4.1 to a 2.733). It's a theoretical discussion, but given enough research, I'm sure a working prototype can be given.

I'm not trying to re-establish any displacement conversion ratings. I'm just introducing a different school of thought. Because piston engines operate on a 1:1 ratio, there's no thought regarding gearing of the engine. Because the rotaries operate under a 3:2 gear ratio, it's hard to directly compare displacement, especially if you look at the way the engines produce their torque pulses (the frequency and amplitude of the combustion events).

Let me as a question then:

If I had to make a twin of a rotary engine in piston form, would I take a 4 cylinder engine with twice the displacement, same power, redline, 1:1 tachometer, and ring & pinion gear set, or would I take a 6 cylinder engine with three times the displacement, same power, 2/3rd of the rotary's redline, a 3:2 tachometer (where 2000 rpm on the engine would read 3000 rpm at the tach), and a ring & pinion gear set at 2/3rd's ratio of the rotary, which engine would perform the closest to the rotary engine? The 4 cylinder or the 6 cylinder?

While it's fine and dandy to take the simple approach and define the equivalent using the double displacement method, I'm more interested in establishing a baseline to compare to piston motors, while taking into account the rotary's unique performance characteristics.

Here's the backup for my idea. It's original research (not done by me), but makes sense once you read through it and analyze his points.

The conclusion that I have is that the rotary engine is an underperforming 6 cylinder motor that needs to catch up with the current stock of high performance 6 cylinders. Though, its power did equal the 6 cylinders that were put in sedans of its time. Or people can view it as a overperforming 4 cylinder @ 2.6L, but that's the easy way out. But for me, I'm hoping that R&D can be taken to a point where the 1.3L rotary engine will start making NA power similar to the high performance 3.9L/4.0L V6's or I6's that we have around. When applying gearing, torque and rpm should change, but power shouldn't, so the rotary engine has no excuses not to perform to that level. But, to make it easy, I agree, every race classfication just doubles the displacement. What's not consistent is if the rotary can compete with 4 cyls or 6 cyls. That depends on the organization. Personally, I'd rather see more consistency in the classifications as opposed to altering the displacement factor of the rotary engine with respect the race results.

With the LS1 Miata, would you be worried about traction issues?

jimlab

You don't have to take into account the rotary engine's "unique performance characteristics". All you have to do is monitor the volume of air consumed over time to prove that they're equivalent.

slo

iTrader: (1)

Trying to measure displacement for comparison between different engine types and not making number of crankshaft revolutions equal is retarded.

Roen

iTrader: (2)

By unique performance characteristics, I meant low torque and higher rpm range.

Agreed, but once you introduce gearing, you no longer have an unique piston counter-part.

Actually, what's even funnier is that 6 cyls consume more air than 4 cyls per time right? Then it's funny that the piston configuration that I come up with that comes closest to performing like the rotary fails the volume of air over time test, if the gearing is moved from the engine to the differential. And if the gearing is done at the differential, then the engines that do breathe like the rotary don't perform like them. Interesting dichotomy.

Any one want to give an answer to the bolded question that I presented in my last post?

It's a problem of essential gearing vs. inessential gearing. The piston's gearing is done at the tranny and the diff. The rotary's gearing is done at the tranny, diff and engine. Why can't we combine the gearing of the rotary's engine and diff and use the combined ratio in the piston's diff, holding both tranny's equal and adjusting the piston engine to produce the same peak power at 2/3rd's the rpm of the rotary engine, of course. After all, gears just torque multipliers, right? If you don't like regearing the diff, you can individually regear each of the tranny gear's to 2/3rds of what they're supposed to be. If that's the case, then because the gearing in the engine affects induction and exhaust cycles, but the gearing at the diff doesn't, does the importance of the air per time method decrease? Just something to think about.

This exercise isn't to measure displacement of a rotary engine. That's a can of worms that no one should really touch, since no one will ever agree on it. It's to answer the question, what kind of piston engine is most like a rotary engine?

This would mean that I could put together a car with a piston engine that breathes completely different than the rotary engine, but performs just like one. All I have to do is to find a proper low power engine from the late 80's/early 90's that displaced 3.9L. Find the right cams to adjust the powerband to where it peaks at 160 bhp at 5000 rpm. Mate it to a tranny with the same tranny ratios as a 5-speed NA tranny and use a 2.733 R&P gearset in the diff. Equalize the weight to an NA rotary engine with all accessories and you would have a piston engine that drives just like a rotary engine! But they'd breathe differently. Contradiction?

But of course there's a kink in this equation. Proving equivalance for NA engines is pretty simple. Turbo engines are a different story. Never thought about pulley-driven chargers either. But at least, for an NA engine, I've shown how you can make a piston counterpart of a rotary engine.

jimlab

No offense, but you're ******* loony. End of discussion.

grade247

this thread is great. this is one of those topics that neither side will agree on either because people are to bias for either a LS swap or the rotary but me on the other hand hell when mine goes I might do a swap but i am thinking more along the RB20 line nothing wrong with I6 power and sound

Josh18_2k

iTrader: (3)

lets move this in a 2jz direction.
i love the way they sound too.
lol

oh btw for the guy asking about how many parts you have to throw at an ls1 for 400hp-
https://www.rx7club.com/v-8-powered-rx-7s-299/just-dynod-v8-rx7-693824/
im sure there are better examples but thats just one i ran over today.
and of course the almighty t-rex cam on unported stock heads-
http://www.thunderracing.com/dynogra...n=read&pgid=60

grade247

ha ha ok now I was trying to keep it on a budget with the RB swap a 2J lol there is a guy doing that swap on here in a FD and wow pricy lol just the swap alone without the mods cost him close to 15k lol

Snyper

As many times as it takes. So far ive not heard a single accurate arguing statement that proves that swapping an LS1 into an RX7 will ruin the car. I have however made, AND HEARD statements that show the improvement an LS1 engine makes when merged with an RX7 body.


Heres my opinions on the Swap. from a 13b

Pros:
-Torque
-Reliablity increase
-Better gas mileage
-Better emmissions(for those of us who have to deal with it.)
-Much easier/cheaper to make stupid power(reliably)
-The looks you get when you pull into a parking lot looking like an import sounding like a drag car.

Cons:
-Goes against the beliefs of a true rotary guy
-umm
-uhh
-initial cost is more expensive than just rebuilding the rotary engine
....
uniqueness can't be determined because it goes both ways, one way you have a car that runs(and runs pretty damn good) without a single piston or sheer size like 99% of the cars on this planet, but the other way you have a car thats supposed to sport a very small "import" engine then you pop the hood expecting to see a big turbo, and see CORVETTE, it kind of raises an eyebrow.

now id like for someone pro-rotary to type out a pros/cons list that can be proven...now I hope none of you take this the wrong way, I just want to see what others think on the other side of the fence, so if you need to respond with a smart *** comment, just save it for yourself.

BogusFile

The Idealist duke it out with reality in a romantic quest to prop up the underdog.

turbotommy

iTrader: (3)

Snyper... check your PM

TehMonkay

iTrader: (-1)

Bench racers.

RETed

Funny, I would think it would be cheaper.
It's about that much here.
I think in Vegas, a gallon of milk goes for about $3?


What am I going to do with an engine with no tranny?
It looks like those T56's are hard to find.
I put up a link to a local board who claims that LS1 + trans are going for $3k to $5k - why can' t you accept that?


Which means headers into a 2-into-1 collector dumping into a stock-type exhaust system.
The 2-into-1 usually adds to the price.


You're sitting on the sidewalk looking at the ground...
You see a pair of red shoes walk by, and you look up...
Pretty girl.
You see another pair of red shoes walk by, and you look up...
Pretty girl.
You see another pair of red shoes walk by, and you look up...
Pretty girl.
Is it reasonable to come to the conclusion that all pretty girls wear red shoes?


Build a 400hp FC for $4,000, and I'll pay you $4,000 cash for the car in person.


-Ted

RETed

Build me a 400hp FC with an LS6 for $6,000, and I'll pay you $6,000 in cash in person.


-Ted

Snyper

im talking about the motor specifically.(if you read)...but thats fine, give me 6k and ill build you a motor with money left capable to support over 700hp....reliably. Im still waiting for the Pros/Cons.

Eat-Pez

iTrader: (1)

Uhh... buy a tranny....

The FC I built for $4k, I paid $1600 for my LS1 and bought the T56 3 months later for $400. It needed about $50 worth of parts to fix a very common problem that arise with them. Obviously, the seller didn't know about this problem and how easy it is to fix.

ya

I know they go for that. The fact is, I don't pay that. I hold out for deals. Why can't you accept that?

Damn it, it doesn't cost that for the guy I use.... Holy crap. How many times do I have to tell you. $120-$150 for a Y from headers to catback. He's done it on quite a few RX7s as well as an Astro van that someone cut out my cat. I bought some shorty headers for it and had him make me a Y.

No. Assumptions make an *** out of U and Ptions.

Why don't you roll up to the Mazda factory and say, "How much do you guys build these cars for? Ok, I'm going to buy one from you for that price. I'll be there tomorrow to pick it up." That's just ignorant. Why would I build a car and sell it to you for cost when I can double my money selling it to someone else?

And I never said that I built a 400hp FC for $4000. I said that I got it going down the road for $4000. It still looked good with stock rims and paint, but I spent more on wheels/tires, paint, and engine upgrades to get it to 450hp.


Before wheels and paint




After

2Fierce

iTrader: (7)

I think I finally understand what Ted is trying to say, and what answer he really wants from you guys, for just one second.



YOU can build the car for 4k, YOU can sell the car for more, no one is expecting you to do labour for free. That would be stupid.

If hypothetically I don't have access to a garage, or tools, (+ live in Canada where Hondas are everywhere and even TA's and camaro's are rare), it would take a while to really wait for a deal unless I bought it from the states and than I'd have to get raped at customs + shipping. Anyways, the point is the cost of what a shop would charge to do this swap PROPERLY vs what it would cost to build up the 13bt INITIALLY (like someone said earlier) is quite significant.

The ls1 is a great engine, hypothetically I really wanna do this swap (maybe) but no tools, no garage, no experience kind of limit me. So, how much would it cost hypothetical ME in your estimations? That's what I think Ted is really asking you guys, not what YOU paid. But having someone do all the labour, what would someone who wants their car done in a month pay?

thanks

Eat-Pez

iTrader: (1)

I can definitely do an FC in a month. I've done an FC with a paint job in a month.

Before


After


Disregard the dates on the photos. Either the seller had the car for sale for quite a while, or the dates on his camera were wrong.

Of course, that buyer paid a premium considering engine modifications, color change, metallic paint, wheels & tires, TII rear, 5lug swap, etc.

If you just want a swap in an FC, I'll do it for $1500 labor, and you buy all the parts. Engine tranny, $3k, cooling system $250, fuel sustem $150, exhaust $150, nickel and dime **** $500. Those are typical costs.

And Ted, I've changed my mind. $4k gets you a 400hp V8 FC. As with every major deal that originates on the internet, I'll need a deposit. Paypal is 6111@excite.com. 20% gets you started.

jimlab

Ted's a big boy. If he wants to ask a specific question, he can do it himself. If all he wanted to know was the cost of a turnkey conversion, he could come right out and ask without quibbling over whether or not you can find an LS1 + T56 pull-out for the prices that people -- who have no reason to lie -- have quoted.

It's asinine to assume that the only source for LS1 pull-outs is ebay or online forums or boards. There are wrecking yards all over the damn place that don't advertise that will sell you a complete assembly, with harness and computer for less than the premium you'll pay for on ebay or a forum from someone who doesn't mind waiting for someone willing to pay top dollar. Tens of thousands of 6-speed Z-28s were built and a lot of them are now stuffed. It's not like this is a rare combination.

My Cobra IRS conversion was completed for about $7,000, give or take, but that doesn't mean that it will cost anyone else $7,000 to swap a Cobra IRS into an FD. I insist on all new parts, and many of the parts were developed by me, so I ate the R&D costs. If you don't mind living with the stock gear ratio in a used pumpkin, the biggest costs are the 300M axles (~$500) and the mounting cradle itself (~$500-650), and you can find a complete pumpkin for $300 or less. If you have the time to hold out for a deal, you can also find Cobra axles used on ebay instead of buying a brand new pair ($500) and tossing everything but the inner CV joints like I did.

Do complete Cobra IRS pull-outs go for a lot of money on ebay? Sure they do. For people in a hurry to find all the parts or who don't want to have to piece together everything they need, that's the price you pay. That doesn't mean you can't find a deal at your local wrecking yard or wait (like Pez) for the right deal to come along on individual pieces.

Personally, I think Ted's just bitter that he can't afford anything being talked about. I almost spit soda all over my keyboard when I read his post about paying someone $6k cash.

2Fierce

iTrader: (7)

Pm sent