I had my V8 converted RX-7 weighed.
01-12-02, 10:25 PM
#26
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Originally posted by RETed
Now, before anything, I'd like to complement you on a job well done.  I don't care for V8 conversions myself, by the pics show a pretty nice car.
So far you've presented corner weights.  Sure, you've hit the magical 50/50 static weight set-up.  It goes a lot more than that.
The stock set-up had a very low polar moment of inertia.  Due to the engine being actually mounted BEHIND the centerline of the front tires, this makes for a chassis the reacts very quickly to direction changes.  There is also dynamic weight number which are not very easy to measure with typical weight equipment.  The car might've hit the 50/50 mark, but how does it HANDLE versus a stock FC???
-Ted
Now, before anything, I'd like to complement you on a job well done.  I don't care for V8 conversions myself, by the pics show a pretty nice car.
So far you've presented corner weights.  Sure, you've hit the magical 50/50 static weight set-up.  It goes a lot more than that.
The stock set-up had a very low polar moment of inertia.  Due to the engine being actually mounted BEHIND the centerline of the front tires, this makes for a chassis the reacts very quickly to direction changes.  There is also dynamic weight number which are not very easy to measure with typical weight equipment.  The car might've hit the 50/50 mark, but how does it HANDLE versus a stock FC???
-Ted
01-12-02, 11:01 PM
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Originally posted by BlackSport0187
By a "work of art" I mean the body styling. The people who do add body kits and all that are just personalizing an already beautiful car design. What the hell does custom exhaust have to do with anything? How does that ruin the "work of art"? Was that even a coherent statement?
For some one so quickly to refer to others remarks as "dumbass", I thought you would have thought more before you talked. What's that about stealing? Did anyone catch that simile? I didn't think so. Oh, and I don't need to make myself feel better, my non-V8 engine already does that. lol.
Don't get so worked up, it was only my opinion dude.
Ike
By a "work of art" I mean the body styling. The people who do add body kits and all that are just personalizing an already beautiful car design. What the hell does custom exhaust have to do with anything? How does that ruin the "work of art"? Was that even a coherent statement?
For some one so quickly to refer to others remarks as "dumbass", I thought you would have thought more before you talked. What's that about stealing? Did anyone catch that simile? I didn't think so. Oh, and I don't need to make myself feel better, my non-V8 engine already does that. lol.
Don't get so worked up, it was only my opinion dude.
Ike
01-12-02, 11:51 PM
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Originally posted by SonicRaT
How the hell does adding a v8 change the body style and ruin the 'work of art' You can't deny the performance increase out of a v8, and I'm sure repair costs will be a hell of a lot cheaper as well, and according to the post with the weight it adds, it's very considerable. Why this is stupid can be obtained for two reasons, it's not original, and it's not rotar. Well, originality sure can't be a factor considering the swaps between N/A's and turbos. Being a non-rotorary could be the only complaint, as to how this ruins the car I have yet to conclude, since everybody's out to make their car faster. I'm sure you could drop the weight even more by swapping to 305 vortec heads while increasing performance as well. It wouldn't be impossible to maintain handling. Your welcome to hate it, and you're welcome to hate my horrific similies, (who ever said I passed english?) But the least you can do is accept that while not being rotary, they can still be an rx7, which is what this forum is all about. (Criticism is acceptable, I'm sure I made no sense at least once in my ramblings, but isn't that what forums are for!?)
How the hell does adding a v8 change the body style and ruin the 'work of art' You can't deny the performance increase out of a v8, and I'm sure repair costs will be a hell of a lot cheaper as well, and according to the post with the weight it adds, it's very considerable. Why this is stupid can be obtained for two reasons, it's not original, and it's not rotar. Well, originality sure can't be a factor considering the swaps between N/A's and turbos. Being a non-rotorary could be the only complaint, as to how this ruins the car I have yet to conclude, since everybody's out to make their car faster. I'm sure you could drop the weight even more by swapping to 305 vortec heads while increasing performance as well. It wouldn't be impossible to maintain handling. Your welcome to hate it, and you're welcome to hate my horrific similies, (who ever said I passed english?) But the least you can do is accept that while not being rotary, they can still be an rx7, which is what this forum is all about. (Criticism is acceptable, I'm sure I made no sense at least once in my ramblings, but isn't that what forums are for!?)
You are right about the cost of parts, but I look at it this way. American parts are cheap, but they also fail a lot more than Japanese parts. I would rather pay more for parts if they are better made and last longer, because in the end you may spend more buying cheap and low-quality parts then if you had bought quality-made foreign parts. A bit biased, but true in my experience.
Making a car faster should not come by compromising it's essential accets. Anyone with the right amount of money and know-how can drop a V8 into anything, while that may make it faster that's not a gurantee to make it better. There is no RX-7 without the rotary, a V8 RX-7 may wear the badge but that doesn't make it right. I respect V8 RX-7 owners love for the looks of the car, but I do not respect their choice of powerplant.
"To forsake the rotary would be to forsake our own identity"
Ike
01-13-02, 12:38 AM
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Interesting choice of words, but how many of you have hit 200k miles in your RX7's without needing a rebuild? Now, if this were toyota I'd have to agree, those things can take 300k without a hitch, but I've yet to see or hear of an rx7 that's made it longer than 150k. However, I must agree american made parts have the worse quality available. Wonder what you would say if someone dropped in a Supra engine? 
I agree, a v8 in an rx7 seems like a slap in the face, but these are cars, car's are meant to be screwed with!
I agree, a v8 in an rx7 seems like a slap in the face, but these are cars, car's are meant to be screwed with!
01-13-02, 01:40 AM
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Originally posted by SonicRaT
Interesting choice of words, but how many of you have hit 200k miles in your RX7's without needing a rebuild? Now, if this were toyota I'd have to agree, those things can take 300k without a hitch, but I've yet to see or hear of an rx7 that's made it longer than 150k. However, I must agree american made parts have the worse quality available. Wonder what you would say if someone dropped in a Supra engine? I agree, a v8 in an rx7 seems like a slap in the face, but these are cars, car's are meant to be screwed with!
Interesting choice of words, but how many of you have hit 200k miles in your RX7's without needing a rebuild? Now, if this were toyota I'd have to agree, those things can take 300k without a hitch, but I've yet to see or hear of an rx7 that's made it longer than 150k. However, I must agree american made parts have the worse quality available. Wonder what you would say if someone dropped in a Supra engine?
I agree, a v8 in an rx7 seems like a slap in the face, but these are cars, car's are meant to be screwed with!
Supra engine in an RX-7 would be an improvement over the V8, but still a travesty. I agree cars are meant to be screwed with, I just don't like the idea of the V8 in a sexy RX-7. But hey, that's just me.
I'm enjoying this discussion,
Ike
P.S. Many non turbos go to around 250k before they crap out. Turbos last about 150k or so on average (with rebuilding of the turbos at 100K). These aren't exact facts, just a general rule of thumb.
01-13-02, 01:45 AM
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Originally posted by BlackSport0187
I thought I was being clean, did I say something that wasn't?
I thought I was being clean, did I say something that wasn't?
Proceed as you were.
This thread is actually kind of interesting. :p
Er uhh did someone say flame?
01-13-02, 02:20 AM
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Here's my $.02 on the subject...
Your V-8 RX-7 probaly doesn't handle as well as a rotary RX-7, turbo or n/a. It certainly doesn't handle the same as one.
The reasons for this isn't completely due to the increased weight, although that may be a factor. It's the placement of this weight that matters. You've proven that you have an even 50/50, which is good.
But the questions are...
Is the majority of the weight located towards the ends of the car, or closer to the center of it?
Is the center of the weight higher, or lower?
I would venture to guess that by installing a V-8 that the weight has been shifted more towards the ends of the car, and a good bit higher. Moving weight towards the ends hurts the car's turn in and how "nimble" it is, but chances are it makes the car easier to control. Since the output shaft on the V-8 is at the bottom of the engine, as opposed to in the center like on a rotary then you've definitely moved the center of the weight higher. Moving the weight higher is even more detrimental to turn in, and has no benefits as far as I know.
Not to knock your car. It's a sweet ride and you modified it to suit your needs, which is all that matters.
Your V-8 RX-7 probaly doesn't handle as well as a rotary RX-7, turbo or n/a. It certainly doesn't handle the same as one.
The reasons for this isn't completely due to the increased weight, although that may be a factor. It's the placement of this weight that matters. You've proven that you have an even 50/50, which is good.
But the questions are...
Is the majority of the weight located towards the ends of the car, or closer to the center of it?
Is the center of the weight higher, or lower?
I would venture to guess that by installing a V-8 that the weight has been shifted more towards the ends of the car, and a good bit higher. Moving weight towards the ends hurts the car's turn in and how "nimble" it is, but chances are it makes the car easier to control. Since the output shaft on the V-8 is at the bottom of the engine, as opposed to in the center like on a rotary then you've definitely moved the center of the weight higher. Moving the weight higher is even more detrimental to turn in, and has no benefits as far as I know.
Not to knock your car. It's a sweet ride and you modified it to suit your needs, which is all that matters.
01-13-02, 02:31 AM
#41
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I'm not so sure about the center of weight being higher, considering a lot of weight will be drawn to the bottom by a heavier transmission, but I'm sure it will want to push through corners as many v8's love to do. I guess we'll have to ask him to run a slamon course?
01-13-02, 02:47 AM
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Originally posted by Felix Wankel
The crank in a V8 is probably right in the same place as the E shaft on a rotary once placed in the car.
The crank in a V8 is probably right in the same place as the E shaft on a rotary once placed in the car.
This is all going back to that polar moment of inertia thing that somebody brought up earlier.
01-13-02, 09:52 AM
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Actually, the crank is lower than the eccentric shaft. The E-shaft is in the center of the engine, and there is half the engine lower than the E-shaft, above the crossmember. The V8 sets the bottom of the crank at the top of the crossmember. the weight of the V8 is actually quite low in the chassis, as the sump goes below and behind the crossmemmber.
Look at the pics of my engine compartment. Notice how small the V8 looks, and how far back it sits. (also notice lack of battery up front) the weight of mine ended up 49/51 f/r (though the corner scale stuff was done back in '94, when I built the car, and I don't have it anymore to scan in... hell, I haven't even owned the car since '98) I don't recall there being that side to side disparity, either, (a small one with the driver in, but not that much). And, since mine was a Sport with no options other than the suspension and brake stuff from the Turbo, it was quite light to start with, ending up at 2720 lbs overall. I also used the Ford small block, which is smaller and almost a hundred lbs lighter than the Chevy.
All the weight is fully between the wheels, so the polar moment is low. Gawd, I wish I stil had the car, so I could just show people. So many people assume so much about what will and won't happen to the cars.
I also have video of my car autocrossing. I need to find a way to get it from Hi-8 to .mpeg, though, so I can post it for everyone to see how flat it corners, and how well it actually worked. Turn-in was crisper, and oversteer was more prevalent, but overall, the car worked better after the conversion than before (and it wasn't a slouch before, being an autocross winner already)
Look at the pics of my engine compartment. Notice how small the V8 looks, and how far back it sits. (also notice lack of battery up front) the weight of mine ended up 49/51 f/r (though the corner scale stuff was done back in '94, when I built the car, and I don't have it anymore to scan in... hell, I haven't even owned the car since '98) I don't recall there being that side to side disparity, either, (a small one with the driver in, but not that much). And, since mine was a Sport with no options other than the suspension and brake stuff from the Turbo, it was quite light to start with, ending up at 2720 lbs overall. I also used the Ford small block, which is smaller and almost a hundred lbs lighter than the Chevy.
All the weight is fully between the wheels, so the polar moment is low. Gawd, I wish I stil had the car, so I could just show people. So many people assume so much about what will and won't happen to the cars.
I also have video of my car autocrossing. I need to find a way to get it from Hi-8 to .mpeg, though, so I can post it for everyone to see how flat it corners, and how well it actually worked. Turn-in was crisper, and oversteer was more prevalent, but overall, the car worked better after the conversion than before (and it wasn't a slouch before, being an autocross winner already)
01-13-02, 10:01 AM
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I'm not so sure about the center of weight being higher, considering a lot of weight will be drawn to the bottom by a heavier transmission, but I'm sure it will want to push through corners as many v8's love to do. I guess we'll have to ask him to run a slamon course?
01-13-02, 11:46 AM
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you know a turbo on the passenger side would even things out a bit 
. Any plans for getting that thing on a dyno? I'd like to hear how much it's putting out!
BTW congrats, it looks great!
. Any plans for getting that thing on a dyno? I'd like to hear how much it's putting out!BTW congrats, it looks great!
01-13-02, 02:47 PM
#50
Originally posted by Little Donny
I don't really know why everyone always brings up how a v8 destroys the handling of the 7 without bringing up this point.
90% (or more) drivers of RX-7's never even push their car to the limits of handling. I've driven my car very aggressively on the street many years but never really pushed the limits until I was lapping Homestead Intl Speedway. I don't care what anybody says, you cannot drive your car as hard on the street as you will on a track. It's totally different. So... bottom line is most drivers aren't going to probably even notice much of a difference unless they take it to the track and end up pushing into the weeds.
Also I thought that the 2nd gen handled great then I rode in a 3rd gen around Sebring... wow!
I don't really know why everyone always brings up how a v8 destroys the handling of the 7 without bringing up this point.
90% (or more) drivers of RX-7's never even push their car to the limits of handling. I've driven my car very aggressively on the street many years but never really pushed the limits until I was lapping Homestead Intl Speedway. I don't care what anybody says, you cannot drive your car as hard on the street as you will on a track. It's totally different. So... bottom line is most drivers aren't going to probably even notice much of a difference unless they take it to the track and end up pushing into the weeds.
Also I thought that the 2nd gen handled great then I rode in a 3rd gen around Sebring... wow!