singledownloop
singledownloop Reader
11/20/17 4:45 p.m.

I'm swapping the B18 engine in my pv444 for a LS engine.The B18 weighs 340 lbs and the LS weighs 450 lbs.The car has a 51/49% front to rear weight distribution?Can someone tell me what the front to rear weight ratio will be with the extra 110 ponds the LS adds to the front?Is it possible to figure out how far I would have to move the LS engine back to get 50/50% weight distribution?I've taken the volvo engine weight and front to rear weight ratio from a original factory volvo manual.,thanks.

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
11/20/17 4:56 p.m.

This is a word problem from school, isn't it?

What's your total weight right now? I don't think we can solve without that. We may need wheelbase to figure how far back it has to go for 50:50.

Also, what's your transmission weight change? How about the rear end? Cooling changes?

Keep in mind that nothing spectacular happens at 50:50. It's a point on a continuum, not a magic number. The change in power delivery will overwhelm any slight percentage difference front:rear. This is a concept many people have trouble with. The correct answer to your real question is "move the LS as far back as you can without messing up ergonomics or handicapping other parts of the design".

rslifkin
rslifkin SuperDork
11/20/17 5:25 p.m.

I'm with Keith on this one.  And the big thing is, avoiding weight hanging out past the front (or rear) axle will likely affect the car's behavior more than the absolute front / rear weight distribution.  Of course, moving the engine back (up to a point) will help both. 

singledownloop
singledownloop Reader
11/20/17 5:45 p.m.

In reply to Keith Tanner :

Factory weight  2200 lbs 

102" wheelbase

 60 lbs added to 40 lb stock trans weight.

 40 lbs added to stock 130 lb rear end weight

Exchanging brass radiator for aluminum radiator/electric fan so no cooling system weight gain.

Thanks I appreciate the help.

 

 

 

 

singledownloop
singledownloop Reader
11/20/17 5:48 p.m.

In reply to rslifkin :

No added weight past front axle or rear axle.All weight added will be between front and rear axle.

SVreX
SVreX MegaDork
11/20/17 6:05 p.m.
singledownloop said:

In reply to rslifkin :

No added weight past front axle or rear axle.All weight added will be between front and rear axle.

How is that possible?  Doesn't the engine sit in front of the front axle?

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
11/20/17 6:12 p.m.

So, even though we know the answer is "as far back as you can", here's the math.

Current front weight: 51% of 2200 lbs, or 1122 lbs.
Rear weight: 1078 lbs.

Add 110 lbs to the front (engine), 40 lbs to the rear (rear end) and 30 lbs to both front and rear (trans). That gives us 1262 front, 1148 rear or a total of 2410.  I'm cheating a bit on the trans, the weight will be split front:rear but I have no idea in what ratio because I don't know this car's layout so I just split it evenly. In reality, probably more like 2/3 ends up on the front.

1262 is 52.4% of 2410 lbs, so you'll end up at 52.4:47.6.

To get to the theoretical 50:50, you'll need to push that engine/trans far enough back that nearly 60 lbs ends up on the rear axle. That means you're going to want it a LONG way back. Like probably into the driver's lap in this four-seater.

It would be a lot easier to take other weight off the nose (move the battery, redesign the front subframe, lightweight panels) than try to make that engine fit. On my MG, I was able to take a lot of weight out of the front end by ditching the massive control arms and subframes and replacing them with lighter weight modern parts.

rslifkin
rslifkin SuperDork
11/20/17 7:19 p.m.

Swapping to the lighter radiator does remove a few pounds from the extreme front end, so that's definitely a help. 

NOHOME
NOHOME UltimaDork
11/20/17 7:30 p.m.

Man...I love reading about other people struggling with this E36 M3! wink

singledownloop
singledownloop Reader
11/20/17 7:32 p.m.

In reply to Keith Tanner :

I've owned several MGB's so know if you got a LS engine to fit under your hood then it'll fit under the hood of my PV444.I'm 5' 5" and can't even reach the clutch/brake pedals if I move my stock factory seat to rear most position..Given my height and distance between back of dash and firewall I could move my engine 6" to the rear without dash mods or relocating the seats.What would the front/rear ratio would this be,thanks.

singledownloop
singledownloop Reader
11/20/17 7:38 p.m.

In reply to rslifkin :

Sorry about not being clear when I said I wasn't adding weight in front of the front axle.I plan to mount the front of the engine to crossmember so there'll actually be less weight in front of the front axle then stock.

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
11/20/17 7:43 p.m.

I can't figure what the F:R ratio would be with the engine back 6", not with the info I have.

Fitting the LS engine into the MG involved pretty much cutting off everything in front of the firewall. My F:R distribution is the same as stock.

singledownloop
singledownloop Reader
11/20/17 8:30 p.m.

In reply to Keith Tanner :

Keith I definitely appreciate the info you've already shared.Did you ever decide to go ahead and put the miata rearend in your MG?I've owned a chrome bumper GT,a super nice chrome bumper MGB,a daily beater rubber bumper MGB,and a nice rubber bumper MGB I put a aluminum 215 buick engine with a T5 in it I upgraded the shocks and swaybar and short wide tires on 8" rims.I had to sell 3 of them during a divorce.I kept the driver rubber bumper MG until 1999 when I bought a new miata sport during a blizzard.

wspohn
wspohn Dork
11/21/17 3:12 p.m.

Easiest way to tell is to put the engineless car on the scales, ballasted for new engine weight.

And don't neglect the driver - when I corner weighted my Solstice (not a competition car, just did it for the hell of it when we did the alignment) the balance shifted toward the rear with the added weight of the driver.

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