Let's talk weight
 

There's a lot of heated talk all around the internet about how much weight the V8 adds. Some people say as much as 200lbs. I can. So, I was wondering if the people that have weighed their cars ( any generation 7 ) could chime in here and say their current weight, the current set up they're running, and if possible, how much their car weighed pre swap. Thanks.

You're asking the wrong question. Anything you can change/take off/add with a swap you can do without a swap. This is why people talk about how much an individual part weighs and compare them.

Surprised you didn't see this:

https://www.rx7club.com/other-engine...eight-1063061/

The LS swap weighs more mostly because of the t56 transmission, which is low and in the center of the car.

My FC handles about the same with the LS1 in it. I had an NA in my FC and needed a couple suspension adjustments for the extra power. My car is a partially gutted track car, and is around 2650-2700 lbs.

Thanks for the reply. I understand. I was just hoping to to get some figures to show averages/examples of what people ended up with after swaps. There are people that say it adds 200lbs and such and I know for a fact that with an FD that's not the case. I don't know about previous generations though.

This is very straight forward. Thank you!

It might add 200 lbs in a NA FC, especially considering most add T2 rear ends. That is 40 lbs right there. My S4 NA FC was ~2550 before the swap. I am under 2700 now and partially gutted with a roll bar.

This is not really an apples to apples comparison as I found out a bunch of years ago when I thought I could get my swap weight down to what my ITS cars weighed. The weight of the engine and trans is not really the issue. As soon as you start adding bigger wheels/tires, bigger brakes, dual exhaust, etc., the weight starts adding up. My swap weighed 2766 w/out driver and had both front seats, door glass, dash. ITS car weighed in at 2680 with driver. ITS wheels weigh 9-12 #'s each (15") and uses stock brakes. My swap had 17"wheels that weighed around 20# each and I run 13 1/8" front rotors and 11 1/2 rears. Extra seat weighs around 38# and as you can see it all adds up. Bottom line, the car handles like and RX7 with a ton of torque. I run a big front bar and no rear bar and prefer a square wheel/tire setup. Running staggered might require running a rear bar depending on driver preference and I've played with different sizing on our NASA car which runs 285 fronts and 315 rears.

95 ls3 fd
no ps or ac
stoptech bbk
03 cobra rearend
lizard skinned interior
enkei rpf1's 9.5 all around

weighed 2765 with a little under half a tank

94 Full interior
All accessories in working order
LS1/T-56
Battery moved to rear
80+lb of stereo in the back
WAAAYYY too much dynamat
18x10 CCW's all round
3030lb with a full tank on a semi truck scale who knows how accurate :-(
Slightly rear biased with stereo. About 49.2/50.8 Should be about 50/50 without it.

Mine weighed 2780 lb. with 1/8th tank of fuel before engine swap, 2800 with 1/8th tank after LS2/T56 swap, but before bigger wheels/tires/brakes, roll bar, A/C, p/s, and Accusump.

With ~50 lb roll bar, 17x8.5 17x9.5 TE37s with 255/40-17 265/40-17 Z1 Starspecs (heavy tires!), A/C, p/s, battery in bin behind passenger seat, 8.8" Cobra diff, full interior, buncha Dynamat, main and sub amps between rear shock towers (sub removed), ~25 lb of Accusump in the spare tire well, with 3/4-tank or ~15 gallons:
total = 2949 lb (should be ~2855 lb empty)
front = 745L + 742R = 1487 (50.4%)
rear = 724L + 738R = 1462 (49.6%)

With me in it and 3/4-tank:
total = 3114 lb
front = 795L + 759R = 1554 (49.9%)
rear = 796L + 764R = 1560 (50.1%)

LargeOrangeFont said it. Most of the weight is in the t56 transmission. The thing is huge, but it sits low in the middle of the car. My 88 tii ls1 fc sit's at 2890 with full interior, huge battery, and ps pump.

50/50 for the win
 

I have a similar setup with an LS2, Its amazing how its still anywhere close to 50/50!

It's very hard to get exact numbers since most change other things.

I can tell you my '88 TII with an aluminum block 5.7 + turbo kit + T56 + full interior (heat/power everything, sound deadening, stereo, etc) weighed 2806 lbs on calibrated corner scales. 51.9/48.1 F/R weight balance.

94 stock LS3/T56 with PS and A/C. Full interior/stock leather seats and roll bar.
Sunroof etc. with me in the car and half tank of fuel. Accurate corner balanced and cross balanced/aligned.

3219 lbs (with driver) 2980lbs without driver
Front 50.7%
Rear 49.3%

Cross weights within 1 lb.

Also the car ran 0-60 on the Vbox in 3.8 second with as you can see a slow 1-2 shift and street tires!
Not bad for ruining the balance of the car with an LS Swap lol

The car with N/A power is so much more linear and easy to modulate the power and makes it a joy to drive.
The cars are a lot of work to make right so don't go into it like its a breeze. There are always things that can be improved on the refinement of the swaps but the trail has been blazed and they are now working on retrofitting the stock FD power steering pump on the LS front accessories. Plus all the Subframes are nicely worked out with the Samberg parts.

I sold my car but for a guy who turns all his own wrenches it's a great swap. If you pay someone to do the work plan on it getting expensive fast.

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Wet weight with spare tire and tools etc is 1260 for my car
Cross weight 2kg difference 50.2/ 49.8 including the rollcage
I didnt spend much time with the scales.. it should easily go 50/50

Been thinking to bring the weight down another 100 150lb with carbon doors and hatch but im affraid i will lose the comfort because its still a daily car

I didnt realize it was for v8 swaps. Sorry

Well, now that you posted in this section you are obligated to V8 swap your car! hahahahaha :lol:

Im actually very happy with my 13b... you might have to switch back to 13b and save some weight :)

my LS7 FD with a full tank of fuel, 3 gallon dry sump tank, no passenger bins or rear carpet/spare/tools, dual 3" to 3.5" exhaust with cats and heavy muffler, odesey 26lb battery in driver side bin, widebody kit with 315 front/335 rear (very heavy tires), T56, cobra 8.8" diff, full sound deadening, Touring model with sunroof (rear Bose removed) was 2840lbs. no a/c with factory R1 seats. Put on the scale 49.5% front/50.5% rear

there is a stock body FD with ls/t56 power, stock rear, setup for autocross and is totally gutted.... it is 2553lbs and full tank of fuel. http://www.norotors.com/index.php?topic=14851.60

I came in at 3077 with me in the car (150 lbs) and a full tank of gas. 49.9%/50.1% front/rear.

My FC is 2908 with me in it and full of fuel. 51.8% on the front wheels. Its right at 2600 with no fuel.

still much lighter than newer cars.

Mine weighed in at a hair under 2800 before I gained 50 pounds with a full tank.
93 base ls6 t56
fiberglass fenders
Fiberglass hood
Aftermarket bumper
No stereo or components
no ac or ps
Turbo II led
18x9,18x10 forgestars
No spare or any hatch interior
gonna grab some scales from work and try again, seems like those scales read about 25-30 lbs per axle low just off what I'm seeing here.

Ive heard in a FC, LS1 weighs 100lbs more than a 13bt, aftermarket turbo with a FMIC setup.

Its funny that that there is no easily accessible definitive answer, I've seen a couple claim the same and or marginal weight gains with the ls when staying in race trim (no ps or abs on an all aluminum setup).
I've even got 1 thread I've seen that full ac and ps setups tipped the scales 27 pounds over rotary weight, with about 50-60 pounds more on the read axle and the front actually being lighter (due to a majority of weight being low in the transmissions area).

I have a full belt 87 FC race car with a SBF and T56. Dry weight is 2590 and weight balance is 53F/ 47R. I could probably take maybe 60 to 70 pounds more out of it. With fuel and driver weight its 2845 LBs. If I had used an aluminum LS I'm sure I could have the car at around 2300 and change dry and better balance of course.

To get the definitive answer one would have to buy a scale, buy the parts and document the weights.

However, most all the people doing LS V8 swaps into RX-7s aren't obsessed with weight, so they don't bother to document weight that precisely. They just want an RX-7 with plenty of reliable power and smog legality is a big bonus to some.

I was more curious about weights than V8s (heyyyyyyyyyy), so I purchased a high capacity digital draw scale (they are cheap now).
So far I have learned my full accessory, stock 13B-REW with oil/coolant drained and no downpipe weighted 407lbs ( I was expecting 420lbs). Results will vary.

Here are links to an FD owned by a someone obsessed with weight and rotaries if you are interested-
2385lb "full interior" (modded interior) single turbo street FD

https://www.hoonigan.com/blogs/daily-transmission/super-light-1994-mazda-rx-7-r2


https://www.rx7club.com/build-threads-292/fd3rs-recap-thread-1130035/

Holy shmolies! They were right!

https://cimg2.ibsrv.net/gimg/www.rx7...69deab0d75.png

Yup!
Fully dressed LS V8 engine (497lbs) is right around 90lbs more than a stock fully dressed 13B-REW engine (407lbs).

Now, it is a LOT easier to take 150lbs off the 13B-REW rotary engine than the LS engine if we are talking modified engines...

The 13b is also shorter (farther back in the bay) and the CG is lower. But, I doubt 95% of people could care or tell about the weight difference.

I heard about the weight ratio, is the LS1 takes it from 50:50 to 51:49, which really should be hardly noticeable. Not sure how to calculate it.

I weighed my modified 13B-REW again before putting it in.

360Lbs
Power steering and simplified stock sequential turbos.
Weight reduction- emissions delete, AC pump delete, lightweight pulleys, manifold porting, dirt/grime removal.
Weight additions, enfini Y-pipe, Greddy TB elbow, Winchester oil Pan, updated iron LH motor mount, 8 cans of satin black paint :naughty:

The takeaway is an emissions strip and AC delete takes 50Lbs off a stock 13B-REW.

FB with Iron Block
 

My FB with a LT1 and heavy 17x9 weighs 2477lbs

1st post for me mine is a bit heavier
my 84 Rx7 weighs 2920lb with me in it and about 1/2 a tank of fuel.

455 Pontiac . 200-4R trans
headers, dual exhaust, aluminum intake
manual steering
stock 13" tires wheels
full interior
Jegs aluminum radiator

That username is awesome! The engine weight with a manual transmission can easily be lowered with aluminum flywheel... Back in 2005 I had a heads/cam LS1 making 440rwhp and it was pretty much 50/50 with 285/30/18's at all corners and 2800lbs with a heavy dual 3" mild steel exhaust and stock body panels. On the skidpad it did 1.13g's and handled great with fast turn in.

I used to own a full race wide body FD on 320mm Hoosiers at all corners/CCW C10
https://cimg2.ibsrv.net/gimg/www.rx7...40bb0e6430.jpg
18x12's, 438ci LS7 with G-Force 4spd dog box (80lbs) running a 14lbs clutch/flywheel.... fully gutted, fiberglass doors, fulll cage, tubed front clip, CF hatch, lexan front/rear windows, no side windows, no a/c, basic aluminum dash with display.. and it was 2470lbs with 8 gallons of fuel. That car ripped on the track. This picture is when the new owner had it and repainted the car plus added some front aero work.... did a MAST Motorsports $20K 416ci engine, Quaiffe sequential trans, and other goodies! The car had about $100K into before he bought it... then he put easily another $40K into it after I sold it to him.

I weighed my car, it was 2477 lbs with heavy wheel/tire setup (50lb per corner) and not much other weight reduction measures. Iron block LT1

The CG of a rotary is actually pretty high,when you factor in that the oil pan has to necessarily be short and flat, so the whole mass of the engine has to sit over any crossmembers. The high crank centerline means the drivetrain has to sit high as well.

It's kind of the same problem that Subarus have. Yes technically the CG of the engine is low relative to the crank centerline, but open the hood and you notice that the crank centerline is actually as high or higher than the top of the bumper.

All out LS V8 with custom smaller diameter flywheel, bellhousing, starter and the dry sump.

LS block is a deep skirt design where the main bearing caps have additional bolts through the block skirt.

I don't have the exact measurement from the center of the crank to the bottom of the skirt, but I believe it is around 2.5". On a lower displacement LS the rod swing minimum depth past the skirt is 3.6" and closer to 4" for the higher displacement (7.0) LS, plus 1/8" CNC dry sump pan below that.

I believe with lost of $ you could get a dry sump race LS down to 6.225" from crank to bottom of dry sump pan for a low displacement/stroke LS and more like 6.5" for an LS 7.

Again, about the same as the 6.5" with the MFR 13B dry sump with usual thick 0.25" dry sump plate; 6.37" with 0.125" dry sump plate.

Its just all that mass above the V8 crank that makes it look like the crank center line is lower than the 13B.

I'm not seeing it, though. You can set an LS down to where the damper is touching the rack, there is no way to get the crank centerline that low on a rotary unless you lay it on its side like the airplane guys do. And the transmission is going to be sitting a bunch higher, as a result.

Corvettes are an interesting take because I am convinced that part of the reason for having the transaxle is so they could set the engine lower in the chassis. GM automatics hang down really low from the crank centerline (as do most RWD autos) and by putting the trans in the back, they could srt the engine down so low that the flexplate practically drags on the ground, and cut the oil pan depth to the bone. It was kind of an eye opener the first time I saw a C5 in 1997 and saw that the tops of the tires were about the same height as the top of the engine!

The Transaxle in the vettes are the same transmissions used in the Camaros bolted to a rear diff. They could be as low if they were bolted to the engine. Front engine with rear transaxles are normally done for weight distribution.

The high drive-line/eccentric shaft is the blessing Rx-7 owners needed to have pretty much most transmissions fit without having to cut much if anything out of the floor.