Other Engine Conversions - non V-8 Discussion of non-rotary engines, exc V-8's, in a car originally powered by a Rotary Engine.

Engine Conversions Handling Characteristics

Old 08-22-11, 07:43 PM
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Engine Conversions Handling Characteristics

Everyone knows that these ls swaps and 2jz swaps are going to make more reliable power to go in a straight line 7/10 times than our factory 13b's. Personally a 400+ rotary street car is all the power I need and is plenty easy to do nowadays...I've had an rx7 since 2004 and never blown anything up. But I've always been curious about these swaps or what have you.

But being a mechanical engineer I can appreciate what Mazda engineers attempted to do with our motors, the natural advantage it has is it's small compact size and still net reasonable power, therefore they mounted that baby as close to the center of the car within reason which results in a lower and more centered center of gravity, ie, more balanced and better handling car. I'm not a fan of just slapping a big motor in something and calling it good but I'd like to see if anyone has any footage of an ls or 2jz swapped fc or fd on the track against a relatively similar power level rotary. I've seen one ls1 fd vs turbo 20b fd and there really wasn't any comparison there...

THIS IS NOT TO DEBATE WHICH IS BETTER, I DON'T REALLY CARE. I just want to see if all that engineering effort that Mazda put into our rx7's was a waste and all you had to do was slap a big sloppy v8 in it and call it good
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Old 08-22-11, 10:27 PM
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My understanding is that a LS1/2/3 installed in a 3rd gen gives a lower CG. Weight is almost exactly the same. The LS1/2/3 also gives a much wider torque band.

Oh, and the LS1/2/3 series of GM engines are not sloppy (unless you mean sloppy as in lots of torque for a very reasonable cost).
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Old 08-22-11, 10:34 PM
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Originally Posted by rx7 SE View Post
Everyone knows that these ls swaps and 2jz swaps are going to make more reliable power to go in a straight line 7/10 times than our factory 13b's. Personally a 400+ rotary street car is all the power I need and is plenty easy to do nowadays...I've had an rx7 since 2004 and never blown anything up. But I've always been curious about these swaps or what have you.

But being a mechanical engineer I can appreciate what Mazda engineers attempted to do with our motors, the natural advantage it has is it's small compact size and still net reasonable power, therefore they mounted that baby as close to the center of the car within reason which results in a lower and more centered center of gravity, ie, more balanced and better handling car. I'm not a fan of just slapping a big motor in something and calling it good but I'd like to see if anyone has any footage of an ls or 2jz swapped fc or fd on the track against a relatively similar power level rotary. I've seen one ls1 fd vs turbo 20b fd and there really wasn't any comparison there...

THIS IS NOT TO DEBATE WHICH IS BETTER, I DON'T REALLY CARE. I just want to see if all that engineering effort that Mazda put into our rx7's was a waste and all you had to do was slap a big sloppy v8 in it and call it good
I don't think what you're asking for is what you really want or is even very feasible. You're neglecting a lot, mainly driver and suspension. Maybe what you want is a car with identical everything (max power, parts and setup) but different engines with the same driver under the same conditions. Can we throw in a pneumatic motor and gerbil power as well so long as they're similar package wise? The way you're thinking of it all is totally impractical. Plus this isn't a top tier racing class where every ounce, fraction of a horsepower, inch, etc is the difference between success and failure. We're for the most part just people with cars and we drive them. The majority of us don't compete at a professional level in a spec class so what does it really matter? It doesn't.

By the way I don't think the Gen III is just a big sloppy V8. I don't know what you mean or how you're coming up with that. And speaking of a 20b, throwing in an extra iron and rotor isn't going to shed weight.

Was the engineering effort that Mazda put in to the RX7 a waste? Probably not. Was it the best path to take? Probably not. Is it cool? Yeah. Does it all really matter? Not really.

Either way, here's a thread with some weight info.

http://www.norotors.com/index.php?topic=4020.0
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Old 08-22-11, 11:19 PM
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grannysspeedshop.com has a ton of info including weight for all generations, for a bunch of different swaps.
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Old 08-23-11, 03:49 AM
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Thanks, I've actually done quite some research so I'm familiar with the weight comparisons...just wanted to see if anyone had any footage of any engine converted 7's around the track. I'd like to get an idea of how they handle since I've never had the opportunity to ride in one. Most of the vids I find on youtube are just driving around town, burnouts, or dragstrip...
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Old 08-23-11, 03:54 AM
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Youtube
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Old 08-23-11, 10:28 AM
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I'm looking for it now...

I recall a youtube video of a 3-rotor being chased by a v8 swap. Both FDs. V8 was getting held up...



EDIT:
Can't find it. Oh well. I'm mounting a 2JZ on my bumper just to **** off rotards.

Also, as mentioned above, I love how rotary fans (the uneducated ones, really) will bad-mouth an LS1 all day, but if you slapped in a heavy *** 20B they will praise your amazing accomplishment.
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Old 08-23-11, 11:13 AM
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Originally Posted by CKxx View Post
I'm looking for it now...

I recall a youtube video of a 3-rotor being chased by a v8 swap. Both FDs. V8 was getting held up...



EDIT:
Can't find it. Oh well. I'm mounting a 2JZ on my bumper just to **** off rotards.

Also, as mentioned above, I love how rotary fans (the uneducated ones, really) will bad-mouth an LS1 all day, but if you slapped in a heavy *** 20B they will praise your amazing accomplishment.
I would personally do the same thing just because I've seen maybe 5 20b's in person my entire life, loved the sound and it's performance. I see an ls motor just about everyday...it's not unique, all personal preferences anyway. But getting back to the point, a 20b is not what Mazda designed the rx7 for either so that's not really the comparison I've been trying to find. Thanks for looking tho
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Old 08-23-11, 11:16 AM
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They handle nearly the same. I would bet that a LS1 T56 combo is the same weight or lighter than a turbo 20B with all associated hardware. I don't know what a 20B weighs, but the LS1/T56 combo is heavier than the Turbo 13B by 60lbs (maybe as much as 80). Once you throw on a bigger turbo and bigger intercooler etc, that gap closes significantly.

The significantly heavier item for the ls swap is actually the transmission, not the engine. The t56 is 125 lbs but that is the best place to add extra weight, low and in the middle of the car. The balance of most LS swapped cars (FC and FD) is at or very near 50/50.

My car was NA so between the LS1/T56 swap and Ford 8.8 IRS rear end swap, I will have added 150-200 lbs to my car. I expect it to be around 400-420 WHP and weigh under 2700 lbs.
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Old 08-23-11, 11:28 AM
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Originally Posted by mattp View Post
I don't think what you're asking for is what you really want or is even very feasible. You're neglecting a lot, mainly driver and suspension. Maybe what you want is a car with identical everything (max power, parts and setup) but different engines with the same driver under the same conditions. Can we throw in a pneumatic motor and gerbil power as well so long as they're similar package wise? The way you're thinking of it all is totally impractical. Plus this isn't a top tier racing class where every ounce, fraction of a horsepower, inch, etc is the difference between success and failure. We're for the most part just people with cars and we drive them. The majority of us don't compete at a professional level in a spec class so what does it really matter? It doesn't.

By the way I don't think the Gen III is just a big sloppy V8. I don't know what you mean or how you're coming up with that. And speaking of a 20b, throwing in an extra iron and rotor isn't going to shed weight.

Was the engineering effort that Mazda put in to the RX7 a waste? Probably not. Was it the best path to take? Probably not. Is it cool? Yeah. Does it all really matter? Not really.

Either way, here's a thread with some weight info.

http://www.norotors.com/index.php?topic=4020.0
Sorry if I didn't make myself clear, with all the car footage out these days I figured it wouldn't be hard to find 2 rx7's of the same generation but different powertrains racing around a track (hopefully in car footage). That's all I need help finding, I can do the rest of the analyzing myself.


They handle nearly the same. I would bet that a LS1 T56 combo is the same weight or lighter than a turbo 20B with all associated hardware. I don't know what a 20B weighs, but the LS1/T56 combo is heavier than the Turbo 13B by 60lbs (maybe as much as 80). Once you throw on a bigger turbo and bigger intercooler etc, that gap closes significantly.

The significantly heavier item for the ls swap is actually the transmission, not the engine. The t56 is 125 lbs but that is the best place to add extra weight, low and in the middle of the car. The balance of most LS swapped cars (FC and FD) is at or very near 50/50.

My car was NA so between the LS1/T56 swap and Ford 8.8 IRS rear end swap, I will have added 150-200 lbs to my car. I expect it to be around 400-420 WHP and weigh under 2700 lbs.
Thanks for the info, did you track your fc before the swap as well?
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Old 08-23-11, 01:33 PM
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Originally Posted by rx7 SE View Post
Sorry if I didn't make myself clear, with all the car footage out these days I figured it wouldn't be hard to find 2 rx7's of the same generation but different powertrains racing around a track (hopefully in car footage). That's all I need help finding, I can do the rest of the analyzing myself.




Thanks for the info, did you track your fc before the swap as well?
Yes I put well over 2000 track miles in 18 months on my FC before I started the swap. It was pretty fast on shorter tracks for a full weight NA FC with street tires (NT05s).

I've driven LS1 FCs and they are truly excellent if done right.

For a track car the LS1 was a more reliable choice VS. a turbo II swap. Had I started with a TII I may have just rebuild what I had and that definately would have been cheaper.

The cost of a built turbo 13B and a rebuilt turbo transmission and the cost of my built LS1 with built T56 were very similar. Also, for under $1000 I could have another 50-75 WHP via a head and/or cam swap.
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Old 08-23-11, 04:37 PM
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Originally Posted by LargeOrangeFont View Post
Yes I put well over 2000 track miles in 18 months on my FC before I started the swap. It was pretty fast on shorter tracks for a full weight NA FC with street tires (NT05s).

I've driven LS1 FCs and they are truly excellent if done right.

For a track car the LS1 was a more reliable choice VS. a turbo II swap. Had I started with a TII I may have just rebuild what I had and that definately would have been cheaper.

The cost of a built turbo 13B and a rebuilt turbo transmission and the cost of my built LS1 with built T56 were very similar. Also, for under $1000 I could have another 50-75 WHP via a head and/or cam swap.
very nice. Well, may be something I'll have to look into down the road, thanks for the unbiased comments...I hope to get to ride in a swapped rx7 one day, one thing nobody can deny is that Mazda did an excellent job when building our chassis, whether it's fb, fc, or fd.
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Old 08-24-11, 05:35 PM
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Watching videos is a lot of fun and very entertaining but it won't allow the viewer to evaluate how well a car handles. It has to be experienced first hand, behind the steering wheel.
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Old 08-27-11, 11:06 AM
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Smile FD corner balance: ~2900 lbs, 50/50 f/r, torque=fun

I just had my car out autocrossing on a pretty slow track and it handles, as far as I can tell, just like it did before with the rotary. Taking some corners at speed when I can find them... feels the same to me. And if anyone is curious about the weight, mine came in at just over 2900 lbs w/o A/C, but full interior and a full tank of gas - 20 miles worth of driving (say gallon less than full... about 6 lbs). So my car gained about 100 lbs (before it was about 2800, 1/2 tank gas). Distribution with the v8 is 50/50 front/rear. Cross weights about 4 lbs off. As for vertical CG... dunno. The crank is pretty heavy.. I'd guess 50 lbs, it's pretty low. The clutch/flywheel (I have the Ls7 clutch and heavy *** LS2 flywheel) is heavy too. Heads are aluminum, composite plastic intake manifold... I'd say it's probably comparable to the old rotary setup. I'm not good enough of a driver to notice anyway

Car made about 350 whp/340 tq thru factory exhaust manifolds and cats (btw I put it on a California smog machine a few weeks ago it burned clean as a whistle! the tech was blown away) with a nice fat torqueband. Basically from 2.5-6k I have 300+ ft-lb to play with. 4:10 final drive ratio... instant throttle response. it's so fun to drive. I love it. I'm glad I drove the car rotary for almost 5 years because I have a HUGE appreciation for the v8 setup, IMO it makes the car so much more enjoyable!!!!! I'd argue that the torque of the engine makes it easier to drive on a track/thru turns as there is no ramp in the torque due to forced induction. It's a lot easier to steer with the gas pedal now than before



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Old 09-07-11, 02:22 PM
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I noticed absoultely no difference in handling with my cast iorn 302 FB. I noticed it's not so much the handling is different, it's the fact that it becomes scary easy to push the car past it's handling limit when your packing 3x as much power.

just my $.02
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Old 09-16-11, 12:39 AM
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I've extensively tracked both rotary and LS FD's. The handling characteristics of the FD are still there with V8 in the car. My car is 50/50 front rear and cross. Here is my LS1 FD going around Road Atlanta:
http://www.youtube.com/watch?v=IFY00PAK_Ps

And my rotary FD at Road Atlanta a couple of years ago in Dec 09:
http://vimeo.com/8034361

Dec 2010 in LS1 FD:
http://www.youtube.com/watch?v=p2mkQz_L4N8

I can take alot more of the variables out as when I first built the car, I had the same coilovers, sway bars, and alignment settings on both cars. Horsepower level was the same. Same wing. Same track, same tires, similiar weather conditions based off my constant(a handful of cars that were running the same times both events). When hp level is the same, the LS1 is significantly faster due to the fact that I prob. have 100 more ft lb's of torque over the rotary. There are variables obviously that make the cars difference. For example, rotary car has a M2/race shop roll bar opposed to the LS1 car having a full cage.
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Old 09-17-11, 07:00 AM
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Thank you for posting Brent. Just what I was looking for!
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