Suspension setup for a v8 swap

[steel330i]

R3V Fam,

I’m interested to hear what everyone is running for their suspensions and rear diffs / axles/hubs on their swapped e30’s? I’m planning mine out now and currently have a running donor 98 SS with LS1/T56 and the Sikky kit for install. But my 91 318i is bone stock otherwise and original so needs everything to be replaced (e.g. bushings, FCAs, brakes, etc.).

I also picked up the Garagistic weld on reinforcement kit and a spare z3 full suspension from a junkyard but. It sure what I can use from it in this build.

Thank you for any replies and suggestions!

-Travis


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[jbontke]

The springs for the 6cyl would be sufficient. If i remember right, the m20 weighs slightly more than the LS1.

[varg]

The springs for the 6cyl would be sufficient. If i remember right, the m20 weighs slightly more than the LS1.

I'll bring back these classic images.


I swear the LS1 image gets smaller every time I see it. But it's 609lbs. I don't know if the exhaust manifolds were on the M20 for this weigh-in, but they clearly weren't on the LS. So no, it's 100lbs+ weight gain with a small aft CG shift since it's shorter and has a heavier transmission.

[jbontke]

I'll bring back these classic images.


I swear the LS1 image gets smaller every time I see it. But it's 609lbs. I don't know if the exhaust manifolds were on the M20 for this weigh-in, but they clearly weren't on the LS. So no, it's 100lbs+ weight gain with a small aft CG shift since it's shorter and has a heavier transmission.

I was basing the view on engine weight (418lbs for LS3 with acc and loaded M20 at 397lbs). I did not even think about the transmission weight. I have a T56 next to a ZF and the T56 is much heavier and larger. The T56 and v8 would definitely change the center of gravity. How would you adjust the spring rate as the CG is shifted back? It would be interesting to see a corner balance scale of a before after LS swap.

[iansane]

I swear the LS1 image gets smaller every time I see it. But it's 609lbs. I don't know if the exhaust manifolds were on the M20 for this weigh-in, but they clearly weren't on the LS. So no, it's 100lbs+ weight gain with a small aft CG shift since it's shorter and has a heavier transmission.

I'd say it's a pretty significant aft cg shift since most of the weight increase comes from the mammoth t56.

I run GC/konis front and rear and the front dropped an extra 1/4" or so when the iron block gen3 engine went in. I just picked up a set of scales and am actually kind of curious on what the car weight is now though...

My rear diff is a stock medium case, parts store replacement axle shafts, stock small rear bearings/hubs.

[varg]

A T56 is ~123lbs dry, a G260 around 75lbs so say you're adding something like ~48lbs in the tunnel and ~67lbs over the front axle based on the weights in the famous Vorschlag image. You are not going to get a "significant aft CG shift" out of that if you mean the car's CG. I should be more clear that I mean the engine and transmission assembly has a small aft CG shift vs M20, the swap itself won't move the car's CG back at all. There is simply too much weight added too far forward to have a net rearward shift, even if the CG of the powertrain is further back. I'm only so into these numbers because I looked into this extensively when I was deciding whether to LS swap my E30 or build another car. If I had to guess based on what I've seen over the years an LS swapped but otherwise fully equipped E30 will probably be something like 55/45 and an iron block truck engine swap probably around 58/42, after all, 100lbs is about 3.5% of the 2800lbs+ a swapped car will weigh.

We look forward to seeing the results of you weighing your car, it's unfortunate that weighing a build is so rare but the scales are damn expensive and even most shops don't have them. Though your iron block engine is not exactly an apples to apples comparison to an LS swap, you could put a jack under the center of the engine and take about 100lbs off if it suits your fancy since that is the demonstrated weight difference between iron block and aluminum block. Yeah, I know, the boomers on the forums seem to always claim it's 80lbs, but every actual on-the-scales comparison I've seen shows around 100lbs. While I haven't seen them side by side myself I never saw convincing evidence that the L33 block is significantly different from an LS1 block.

[steel330i]

I'd say it's a pretty significant aft cg shift since most of the weight increase comes from the mammoth t56.

I run GC/konis front and rear and the front dropped an extra 1/4" or so when the iron block gen3 engine went in. I just picked up a set of scales and am actually kind of curious on what the car weight is now though...

My rear diff is a stock medium case, parts store replacement axle shafts, stock small rear bearings/hubs.

Did you use coupe postings or vert? GC spring and Koni shock/strut?


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[iansane]

A T56 is ~123lbs dry, a G260 around 75lbs so say you're adding something like ~48lbs in the tunnel and ~67lbs over the front axle based on the weights in the famous Vorschlag image. You are not going to get a "significant aft CG shift" out of that if you mean the car's CG. I should be more clear that I mean the engine and transmission assembly has a small aft CG shift vs M20, the swap itself won't move the car's CG back at all. There is simply too much weight added too far forward to have a net rearward shift, even if the CG of the powertrain is further back. I'm only so into these numbers because I looked into this extensively when I was deciding whether to LS swap my E30 or build another car. If I had to guess based on what I've seen over the years an LS swapped but otherwise fully equipped E30 will probably be something like 55/45 and an iron block truck engine swap probably around 58/42, after all, 100lbs is about 3.5% of the 2800lbs+ a swapped car will weigh.

We look forward to seeing the results of you weighing your car, it's unfortunate that weighing a build is so rare but the scales are damn expensive and even most shops don't have them. Though your iron block engine is not exactly an apples to apples comparison to an LS swap, you could put a jack under the center of the engine and take about 100lbs off if it suits your fancy since that is the demonstrated weight difference between iron block and aluminum block. Yeah, I know, the boomers on the forums seem to always claim it's 80lbs, but every actual on-the-scales comparison I've seen shows around 100lbs. While I haven't seen them side by side myself I never saw convincing evidence that the L33 block is significantly different from an LS1 block.

I guess I'm confused in what you're saying. The weight is farther back but the CG won't change? Is that what you're saying? I'm honestly not trying to be combative, just understand what you're expressing. I would presume that since most of the weight being added was behind the axle centerline it would contribute to moving the CG back but I could be wrong.

I would consider my e30 a porker. It came to 2974 with a full tank of gas, A/C, P/S, full interior and no attempt at weight savings.
1576 front
1398 rear
Looks like 53/47.

My corner weights are ALL jacked up. I need to play with the coilovers to see if I can balance things out a bit but I've never done that before.

It's kind of funny. I'm almost finished swapping a vq35/cd009 nissan engine into an old 85 celica and it came to something ridiculous like 50.5/49.5. Weight balances can be tricky to estimate.

[varg]

So no aft cg shift at all then. I had to look to find it but my last weigh-in was
1,394lbs F
1,388lbs R
~50/50
This is my turbo E30, there's a 10" subwoofer in a small box with the amp bolted to it against the ski pass, and a chevy truck windshield washer bottle is bolted to the battery box cover, and a little 2 ton floor jack (similar to this: https://www.harborfreight.com/2-ton-...ack-64874.html) next to the sub box instead of the missing OE jack. I also filled the tank up on the way to the shop when I had it weighed. Seems I over-estimated how front heavy an E30 is, or at least mine is, though mine was originally a 318is and supposedly is missing some sound deadening because of that. I could've sworn stock a 325i was 52/48 or 53/47, guess I was wrong.

In the end it's moments. The moment arm is a little shorter with an LS but the weight is more. The engine cg is maybe a couple of inches further back but it weighs more, the transmission is in the same spot and heavier, it has more influence than the engine itself. So the move back isn't enough to make up for the extra weight. In the end, in order to have a net rearward CG shift more of the weight gain has to be on the rear wheels than the front wheels, and that's just not happening when half of the weight gain is directly over the front subframe. How much length does an M20 have over an LS actually?

[iansane]

I gotcha. Yeah, it actually looks like my cg is farther forward than say yours is. Maybe I should throw my tool kit back in the car to balance out that big v8. Ha!

The LS is a bit shorter but that huge waterpump makes up for it, and then some.

[steel330i]

Thanks for insight here gents, but what suspensions are you running on your builds to support the weight shifts?


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[iansane]

Thanks for insight here gents, but what suspensions are you running on your builds to support the weight shifts?


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Oh yeah, I forgot to ask you what you meant by 'coupe or vert postings'? And yes, GC spring with koni strut/shock.

[steel330i]

I meant springs not postings… spring rates for convertible seems higher and thus better for LS1? Or too high ride height?


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[steel330i]

Oh yeah, I forgot to ask you what you meant by 'coupe or vert postings'? And yes, GC spring with koni strut/shock.

Any pics of your ride height with the GC / Koni setup?


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