2ND generation rx-7 --- v-8 conversion kit.

[GTi-VR6_A3]

the only thing i cabn add is that while the new rx-8 will make some 200 sumthin HP its lb ft of torque will only be like 138. that is my one and only arguemnet agains t rotaries NO TORQUE. wtf can i do with all that hp if i cant grip anything. other wise they are friign wierd and badass. and v eniges have their own right in being cool. this stupid argument will go on for ever.

-GTi-VR6_A3

[FunkLord]

its true that rotary engines lack torque... but torque is a function of horsepower. low torque at low rpm's is just crappy, but in a racing situation low rpm's arent used... so it's not an issue.. however low torque at high rpm's can be compensated with gearing. 150lb-ft@9000rpm with a 5:1 differential will have the about same turning power as 300lb-ft@4500rpm with a 2.5:1 differential... the 9000rpm engine will move through the rpm's faster, but will probbably have a powerband about double the range of the other one... maybe 4000-9000 as opposed to 2000-4500.... if both cars have the same HP, then the lighter one will cross the finish line first. this applies to all engines, not just rotary VS piston... but its also how those hondas can be fast with no torque.

but low end torque is just so much more fun for daily driving.... so like i said, it all depends on your goal.

[FunkLord]

one more thing..... formula 1 cars have 3L of displacement. they rev to 18000ish rpm's. they seem to do alright. world rally cars have 2L of displacement. they do ok too.

getting air in and out of the engine is what makes its power... 3 basic ways to increase it... displacement, rpms, and volumetric efficiency (boost). to go fast you need a lot of one of those, have a lot of 2, and you're guaranteed for tons of power... have a lot of all 3, and you're in for one hell of a ride.

[GTi-VR6_A3]

welli got owned in general even though i know most of that i could never have worded it like that hahahah good show and welcome to AF...

-GTi-VR6_A3

[BluStori]

Originally posted by GTi-VR6_A3
the only thing i cabn add is that while the new rx-8 will make some 200 sumthin HP its lb ft of torque will only be like 138. that is my one and only arguemnet agains t rotaries NO TORQUE. wtf can i do with all that hp if i cant grip anything. other wise they are friign wierd and badass. and v eniges have their own right in being cool. this stupid argument will go on for ever.

-GTi-VR6_A3

um... ok... have u ever driven an RX-7??? even tho it lacks torque... it can outperform many other cars in its class... mazda is known for their handling... until u drive one urself, please dont come to a conclusion that rotaries cant grip... cuz they can. The new RX-8 will be beast.

opinion: placing a v8 in an fd is full of stupidity... ud mess up the weight, the front would be more heavier than the back and ur killing the name (RX)...

[GTi-VR6_A3]

Originally posted by BluStori


um... ok... have u ever driven an RX-7??? even tho it lacks torque... it can outperform many other cars in its class... mazda is known for their handling... until u drive one urself, please dont come to a conclusion that rotaries cant grip... cuz they can. The new RX-8 will be beast.

opinion: placing a v8 in an fd is full of stupidity... ud mess up the weight, the front would be more heavier than the back and ur killing the name (RX)...

another rx-zealot.... ive had way to many of these arguments. as for handling i didnt say jack shit about their handling i know its good ive ridden and a few and they are cool cars. im just saying that I would like a car with a lb ft of torque in the area of its hp.

-GTi-VR6_A3

[FunkLord]

"I would like a car with....."

thats exactly what i'm talking about....there is no best... different cars are better for different people... most people cant understand that... rotary engines are better for me, but i dont expect everyone to see it my way... and i certainly dont think everyone should have one, at least not yet.....

[Chris V]

Originally posted by BluStori


um... ok... have u ever driven an RX-7??? even tho it lacks torque... it can outperform many other cars in its class... mazda is known for their handling... until u drive one urself, please dont come to a conclusion that rotaries cant grip... cuz they can. The new RX-8 will be beast.

opinion: placing a v8 in an fd is full of stupidity... ud mess up the weight, the front would be more heavier than the back and ur killing the name (RX)...

I HAVE driven an RX7. Many of them, in fact. And didn't you read the thread u pto this point? The V8 does NOT upset the balance, becasue the car remains front/mid engine. Weight is added pretty much evenly front to rear, and not that much weight to boot (about 150 lbs in the typical install, spread front to back, with the battery moved rearward means the balance is identical if not better than stock!

What's stupid is holding on to this myth that the cars get ruined.

[Chris V]

Originally posted by FunkLord
theres some pretty pathetic and ignorant responses here.... a v8 has its advantages... so does a rotary... the worlds fastest rx-7's are all rotary powered. a 20B engine has the potential for 4-digit HP on the stock engine block. a v8 will have more low end torque, and in the 450-500hp range, will be more streetable. but when you get up to the higher hp ranges, both of them throw streetability out the window... probbably a supercharged v8 would have the best streetability with the highest HP... but superchargers arent cheap.

Sure, the pwrlds fastest RX7s are rotary powered. THey are HUGE dollar cars, too. The guys doing the V8 (and turbo V6) swaps are making very fast cars on extremely limited budgets, which is the point. Get the speed and reliability of an understressed enigne in a light car, for low dollar amounts. My complete conversion cost me less than $2000. Considering I was working at a $7/hr job at the time, there was no way to build the same power and reliability into a rotary for my budget, and the car wasn't worth ANYTHING as a dead RX7.

And 400-500 hp is more than enough in a street car of this weight, so why spend more on a race engine of either type?

Ignorant? I've been building rotaries for a long time, as well as non-rotary cars. I've swapped rotaries into nother sports cars. Been racing for a couple decades. I've read the Carrol Smith series on "Engineer to Win" to build national championship winning sports racers. You want to say my responses are ignorant becasue, out of all teh rotary cars I've had, I KNOW that it's cheaper to get a lot of streetable power from a lightweight V8, and so chose to go that route with this particular car?

even if you make a v8 rx-7 as light as a stock t2... you can still make the rotary rx-7 lighter.

No one ever argued that. What I said was that converting an N/A RX7 to V8 power STILL leaved the car lighter than the stock Turbo. If the stock Turbo isn't a bad handler at it's weight, then the V8 version will not be, either. Get it? I could have made MY car lighter, too, as I didn't do ANYthing to make it lighter. It STILL handled better than it did stock, and better than a stock Turbo (in fact, as was proven on the autocross track, it also was better than many modded turbos...)

The argument isn't that you can't make them lighter, it's that it's not ruining the car. Period.

the block itself it lighter. any weight reduction can be done to both versions. even at the same weight, the rotary one will have a lower center of gravity because of how the engine sits...

THe differnce in engine weights isn't that much, and the rotary sits comletely above teh corssmember, with the eccentric shaft (the crank in a V8 car) held considerably higher up. The difference in CG is barely any differnt, and certainly not enough to negatively affect the V8 car. Been there done that, not working from "theoretical speculation" like some RX7 purists do...

a n/a v8 wont be able to make as much power as a turbo 20b. but a turbo v8 would be able to... but again... turbocharging a v8 isnt cheap or easy. and in terms of gas mileage and reliability... i ask you this: would you swap a 1.6L honda engine into your car? probbably not.

A 450 hp turbo 20B wieghs more than a 450 hp/ NA V8, makes less torque, and is vastly more expensive. It isn't about the total ultimate potential, it's about whet you get per dollar. Dollar for dollar, you get more from the V8 swap than you do from a high powered rotary. I dont' spend more to get less in a computer, and I don't spend more to get less in a house. Why should I be required to in a car, just to satisfy someone's quasi-religious feelings about a unique engine?

theres plenty more to go into, but the fact remains that everything has its ups and downs. you have to evaluate your own goals and see what suits you best.

And this would be the perfect response, but it doiesn't seem to work this way. Those of us who have built V8 7s always have to be on the defensive from people who can't seem to let the religious furor go, and ALWAYS call us ignorant, rednecks, or even blashemers!

i drive a rotary powered rx-7. heres my reasons
-handling

I had that too. In fact, mine probably handles better than yours does, as I proved regularly on the autocross track. Here's a video of the start of an autocross run:

http://mywebpages.comcast.net/cvetters3/rex1.MPG

[/b]-its different... most people dont even know what it is let alone how it works[/b]

I have to agree. I loved being able to rebuild the engines on my kitchen table if I had to... Like aI said, I've had a lot of rotary powered cars, and worked on many more. But I daresay my last car was vastly more unique than the legions of cheap, beat up secretary mobiles that the average 2nd gen RX7 is.

-power:weight

Of the engine? Or of the whole car? In stock form, it doesn't really have a lot of either. The stock '86 Sport I started with had 145 hp. With only the addition of 150 lbs overall, I had almost 400 hp. And since teh 185 hp '87 Turbo wighed more than my 400 hp '86 V8 car (with no provisions made to lighten it further) then I had better power to weight ratio even then.

-rotary's love turbos, and so do i.

Ahhh, rotaries do good with turbos like any engine. Unlike any engine, they can't handle detonation, so you have to be ULTRA careful not to let the rotary run hot or lean. One single ping can destroy an engine, while it takes a lOT of detonation to ruin a piston engine.

-in my opinion, a rotary engine has a superior design, it just lacks the overwhelming R&D that piston engines have

This might have flown as an excuse back in the day, but development of new tech happens so quickly anymore than somthing that's been around since the '60s can be developed as far as something that's been around since the turn of the century. Back then, learning didn't happen at a rapid rate, so decades of development back then can happen in a year or less now, because you get to build on everything that's gone before, and use computer power to accellerate that development. The rotary has too many limitations to be able to be used in widespread applications.

and that one day all cars will be rotary powered...it almost happened once already! as long as the internal combustion engine doesnt become obselete first...

Hydrogen wiil be the fuel of choice in the next 20 years, if less, due to all teh new developments of the last 5 years, and the new Presidential decree to get away from foreign oil dependency (billions of dollars have now been set aside for hydrogen ICE and fuel cell research and the construction of the hydrogen infrastructure.) This is something I'v ebeen keeping close tabs on for the last 5 years, and you would not believe what is happenning. Hydrogen fuel cell buses are already in use. Hydrogen ICE cars arte already in use. Refueling stations and storage systems are being put to use in more and more places, and the Oil companies are paying for a lot of that development, because they know the first one to set up a successful hydrogen infrastructure will rake in the profits.

[Chris V]

Originally posted by FunkLord
its true that rotary engines lack torque... but torque is a function of horsepower.

Ummm. no. Horsepower is a calculated value from the measurement of torque. Torque is work. Horsepower is work over time. It's a function of torque x rpm. Period.

low torque at low rpm's is just crappy, but in a racing situation low rpm's arent used... so it's not an issue.. however low torque at high rpm's can be compensated with gearing. 150lb-ft@9000rpm with a 5:1 differential will have the about same turning power as 300lb-ft@4500rpm with a 2.5:1 differential... the 9000rpm engine will move through the rpm's faster, but will probbably have a powerband about double the range of the other one... maybe 4000-9000 as opposed to 2000-4500.... if both cars have the same HP, then the lighter one will cross the finish line first. this applies to all engines, not just rotary VS piston... but its also how those hondas can be fast with no torque.

but low end torque is just so much more fun for daily driving.... so like i said, it all depends on your goal.

Like your last sentence says, low end torque is more useable for daily driving. And a low, wide powerband is more suited to the average street car, as it does it's job better in moving the mass of the car, passengers, and cargo around. A high powerband can be fun, in the right venue. The street isn't really that venue.

[GTi-VR6_A3]

wow mr chris v went at it and pwned for almost a page. good for him. finally some actual fact based arguing.

-GTi-VR6_A3

[FunkLord]

here we go

Sure, the pwrlds fastest RX7s are rotary powered. THey are HUGE dollar cars, too. The guys doing the V8 (and turbo V6) swaps are making very fast cars on extremely limited budgets, which is the point. Get the speed and reliability of an understressed enigne in a light car, for low dollar amounts. My complete conversion cost me less than $2000. Considering I was working at a $7/hr job at the time, there was no way to build the same power and reliability into a rotary for my budget, and the car wasn't worth ANYTHING as a dead RX7.

so a v8 makes for a better budget-racer. no argument here.
i've said it once and i'll say it again.. it depends on what your personal goals are. with a $2000 budget i wouldnt come close to my goals. but my budget is a little more than $2000. a lot of my budget is for the suspension and other things. unfortunately, none of my friends are selling me their 400hp drag engine for a grand.

And 400-500 hp is more than enough in a street car of this weight, so why spend more on a race engine of either type?

if your goal is to make a pass faster than 11 seconds, then you need more than 500hp.

Ignorant? I've been building rotaries for a long time, as well as non-rotary cars. I've swapped rotaries into nother sports cars. Been racing for a couple decades. I've read the Carrol Smith series on "Engineer to Win" to build national championship winning sports racers. You want to say my responses are ignorant becasue, out of all teh rotary cars I've had, I KNOW that it's cheaper to get a lot of streetable power from a lightweight V8, and so chose to go that route with this particular car?

i didnt say your responses are ignorant. i said there have been some pathetic and ignorant responses on this thread. and i'm sure you'll agree.

It isn't about the total ultimate potential, it's about whet you get per dollar. Dollar for dollar,

not everyone is trying to go as fast as they can for as cheap as possible.

'86 Sport I started with had 145 hp. With only the addition of 150 lbs overall, I had almost 400 hp

you're comparing a stock engine to a modified engine...

In fact, mine probably handles better than yours does

maybe, what do you have in the way of suspension mods?

Ahhh, rotaries do good with turbos like any engine. Unlike any engine, they can't handle detonation, so you have to be ULTRA careful not to let the rotary run hot or lean. One single ping can destroy an engine, while it takes a lOT of detonation to ruin a piston engine.

the average rotary engine makes more gains from a turbo than the average piston engine. just use common sense while tuning.. its not that hard.

i'll finish replying later, i have to go to work

[FunkLord]

And this would be the perfect response, but it doiesn't seem to work this way. Those of us who have built V8 7s always have to be on the defensive from people who can't seem to let the religious furor go, and ALWAYS call us ignorant, rednecks, or even blashemers

i have nothing against a piston swap. i'm all for it. i may one day put a piston engine in my car. but right now, my goals dont call for that. to me it would be a waste of time and effort. rotary engines have advantages and disadvantages, and i dont expect that everyone would be better off with a rotary. its a different engine, and people have different things they are working towards. some people worship the rotary engine and get very defensive about it. i see nothing wrong with having such a love for the engine. it is afterall an amazing design. i think its great that they can appreciate it on another level. i do however, disagree with them bashing everyone who does a piston swap. i see it as one more rx7 saved from the scrap yard.

Ummm. no. Horsepower is a calculated value from the measurement of torque. Torque is work. Horsepower is work over time. It's a function of torque x rpm. Period.

torque is also a function of hp and rpm. it goes both ways. but the bottom line is having as much HP as possible for as long as possible. is what gets you over the finish line. what i said with the theoretical engines still stands. torque is a twisting force, not go-fast power. if gobs of low end torque is what wins races, then why don't we see a lof of diesel engines at the track?

A high powerband can be fun, in the right venue. The street isn't really that venue.

daily driving is not my venue. i wont be using my car to run errands and such. it will be used for racing. a streetported turbo rotary will have a huge powerband... starting from 3000-4500 (depending on the turbo) up to 8 or 9k depending on the size of the ports. even if i had low-end power, i wouldnt really need it for daily driving. being able to floor it from stoplight to stoplight or bumper to bumper without having to launch isnt realyl what i'm after. if i need power to pass someone, i can downshift. its not a big concern for me.

[FunkLord]

heres a video that makes a very good comparison of the rotary engine and piston engine. it should answer all your questions.

http://members.shaw.ca/funkotron/boing21.avi

[Chris V]

Originally posted by FunkLord


torque is also a function of hp and rpm. it goes both ways. but the bottom line is having as much HP as possible for as long as possible. is what gets you over the finish line. what i said with the theoretical engines still stands. torque is a twisting force, not go-fast power. if gobs of low end torque is what wins races, then why don't we see a lof of diesel engines at the track?

Torque vs horsepower, a primer:
http://vettenet.org/torquehp.html

Basically, you are not correct. Torque is NOT a function of horspower. Torque is a real force. Horsepower is a measure of that force over time. And the diesel racer argument? A lame argument always brought up by people who simply don't understand torque and rpm.


hp = Torque X RPM / 5252

Now, what does all this mean in carland?
First of all, from a driver's perspective, torque, to use the vernacular, RULES :-). Any given car, in any given gear, will accelerate at a rate that *exactly* matches its torque curve (allowing for increased air and rolling resistance as speeds climb). Another way of saying this is that a car will accelerate hardest at its torque peak in any given gear, and will not accelerate as hard below that peak, or above it. Torque is the only thing that a driver feels, and horsepower is just sort of an esoteric measurement in that context. 300 foot pounds of torque will accelerate you just as hard at 2000 rpm as it would if you were making that torque at 4000 rpm in the same gear, yet, per the formula, the horsepower would be *double* at 4000 rpm. Therefore, horsepower isn't particularly meaningful from a driver's perspective, and the two numbers only get friendly at 5252 rpm, where horsepower and torque always come out the same.

In contrast to a torque curve (and the matching pushback into your seat), horsepower rises rapidly with rpm, especially when torque values are also climbing. Horsepower will continue to climb, however, until well past the torque peak, and will continue to rise as engine speed climbs, until the torque curve really begins to plummet, faster than engine rpm is rising. However, as I said, horsepower has nothing to do with what a driver *feels*.

You don't believe all this?

Fine. Take your non turbo car (turbo lag muddles the results) to its torque peak in first gear, and punch it. Notice the belt in the back? Now take it to the power peak, and punch it. Notice that the belt in the back is a bit weaker? Fine. Can we go on, now? :-)

The main reason you don't see too many diesels racing (though have you seen the European diesel truck road racing series???) is that you can't gear them up to take advantage of gearing. You run out of top speed. If you gear them low enough to get good top speed, you lose the torque multiplication that affects accelleration. Which is why trucks usually have so many gears. the powerband is so narrow that you have to spend more time shifting to keep it in a tiny LOW powerband. They'll pull buildings down, but becasue they don't rev well, they aren't very fast.