1991 BMW 318is rally cross build

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john vanlandingham

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irish44j

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Yeah, read through his whole build, don't know him personally but he seems sharp for sure. Ratio on mine? it's a 4.10 open, looking for a 4.10 LSD for all the torques.

Honestly you may be fine and/or better off with a different ratio - I run a 3.91 (small case) LSD for rallycross, and a 3.73 (medium case) LSD for stage. There have been almost no times where I've wished for shorter gearing, especially with the Conforti chip adding a higher redline. 4.10 LSD is fairly rare since (IIRC) they only came in the 318is from 1991, whereas the 3.73 LSD is pretty easy to find off the 6cyl cars made over many years.

Now that's nice but since you didn't put your first and last name--as is the one inflexible rule on this forum----we don't know who you are, or--since you didn't put you city and state (or Province) as is part of that same rule---we don't know where you are...and what you've done..
Reason I say that is cause the Intra-webz if swarming with all sorts of people and all the words look the same just one letter after another so the only way to weigh the words is by knowing who we're talking to, where they're from and what they've done..

I think this guy has a 4 cylinder..Lemme go look, OK,. Be right back.

Ok I'm back..Lookie at the piccie:


Welllp that thar shooooore looks like a 4 to me..In fact it looks just like the one I tore down just so I could measure the fawk outta everything with my trust super accurate electronic Very-nears..
Early version was 1800, later 1900. Not a particularly rip snortin' a-rootin and a-tootin' stump pulling, devastation wreaking motor (although plenty of potential just lurkin...brough ha ha!!!)
So one that seems like it could use some help making the carro scoot.

There is a pretty common correlation between engine size (assuming they kinda run and are no unusually big dogs), tire size overall and end use of vehicle--and final drive...

Now for grass-o-cross makes zero difference...its just more fun if a car has a bit of yank to it..
But for stage rally where 95% of what we do is 25mph to 90mph again and again and again all weekend...pretty typically a 2,0 motor making some beans on 13/14" tire might have 4.88 gears and same on short 62cm 15" tires we'd expect to see about 5,0 to 5.15 final drive..
Been that way for decades...
Of course that presumes a gearbox with ratios intended to do 25 to 90...not 30 km/hr oder vollgas immer gerade aus auf der autobahn! and mid-range sacrificed for top speed.

So welcome aboard and all but man to say "3.73 (medium case) LSD for stage. There have been almost no times where I've wished for shorter gearing" is well sehr interessant, junge..

Maybe explain not what--you just said what, but 'splain to the Oh Pea and me : why you don't wish any shorter. Do you not like acceleration? Short gearing = free acc. (that's pronounced like 'axe' , short for acceleration) Of course with the pick-up truck like 1st gear ration go short and you make the 1st gear suitable for "loading onto trailer only" gear but fawkit just go 2nd thru 5th...

But please why?

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formyhealth

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john vanlandingham

Now that's nice but since you didn't put your first and last name--as is the one inflexible rule on this forum----we don't know who you are, or--since you didn't put you city and state (or Province) as is part of that same rule---we don't know where you are...and what you've done..
Reason I say that is cause the Intra-webz if swarming with all sorts of people and all the words look the same just one letter after another so the only way to weigh the words is by knowing who we're talking to, where they're from and what they've done..

I think this guy has a 4 cylinder..Lemme go look, OK,. Be right back.

Ok I'm back..Lookie at the piccie:

Welllp that thar shooooore looks like a 4 to me..In fact it looks just like the one I tore down just so I could measure the fawk outta everything with my trust super accurate electronic Very-nears..
Early version was 1800, later 1900. Not a particularly rip snortin' a-rootin and a-tootin' stump pulling, devastation wreaking motor (although plenty of potential just lurkin...brough ha ha!!!)
So one that seems like it could use some help making the carro scoot.

There is a pretty common correlation between engine size (assuming they kinda run and are no unusually big dogs), tire size overall and end use of vehicle--and final drive...

Now for grass-o-cross makes zero difference...its just more fun if a car has a bit of yank to it..
But for stage rally where 95% of what we do is 25mph to 90mph again and again and again all weekend...pretty typically a 2,0 motor making some beans on 13/14" tire might have 4.88 gears and same on short 62cm 15" tires we'd expect to see about 5,0 to 5.15 final drive..
Been that way for decades...
Of course that presumes a gearbox with ratios intended to do 25 to 90...not 30 km/hr oder vollgas immer gerade aus auf der autobahn! and mid-range sacrificed for top speed.

So welcome aboard and all but man to say "3.73 (medium case) LSD for stage. There have been almost no times where I've wished for shorter gearing" is well sehr interessant, junge..

Maybe explain not what--you just said what, but 'splain to the Oh Pea and me : why you don't wish any shorter. Do you not like acceleration? Short gearing = free acc. (that's pronounced like 'axe' , short for acceleration) Of course with the pick-up truck like 1st gear ration go short and you make the 1st gear suitable for "loading onto trailer only" gear but fawkit just go 2nd thru 5th...

But please why?

lol you're a hoot! I wish I could find 4.55s or 4.88s (from the factory that is) I just don't have the green right now to drop on a custom unit. Also, I am GREEN meaning I have no rally experience so I figure stock and relatively low budget is best... for now any way.

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john vanlandingham

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formyhealth

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john vanlandingham

Now that's nice but since you didn't put your first and last name--as is the one inflexible rule on this forum----we don't know who you are, or--since you didn't put you city and state (or Province) as is part of that same rule---we don't know where you are...and what you've done..
Reason I say that is cause the Intra-webz if swarming with all sorts of people and all the words look the same just one letter after another so the only way to weigh the words is by knowing who we're talking to, where they're from and what they've done..

I think this guy has a 4 cylinder..Lemme go look, OK,. Be right back.

Ok I'm back..Lookie at the piccie:

Welllp that thar shooooore looks like a 4 to me..In fact it looks just like the one I tore down just so I could measure the fawk outta everything with my trust super accurate electronic Very-nears..
Early version was 1800, later 1900. Not a particularly rip snortin' a-rootin and a-tootin' stump pulling, devastation wreaking motor (although plenty of potential just lurkin...brough ha ha!!!)
So one that seems like it could use some help making the carro scoot.

There is a pretty common correlation between engine size (assuming they kinda run and are no unusually big dogs), tire size overall and end use of vehicle--and final drive...

Now for grass-o-cross makes zero difference...its just more fun if a car has a bit of yank to it..
But for stage rally where 95% of what we do is 25mph to 90mph again and again and again all weekend...pretty typically a 2,0 motor making some beans on 13/14" tire might have 4.88 gears and same on short 62cm 15" tires we'd expect to see about 5,0 to 5.15 final drive..
Been that way for decades...
Of course that presumes a gearbox with ratios intended to do 25 to 90...not 30 km/hr oder vollgas immer gerade aus auf der autobahn! and mid-range sacrificed for top speed.

So welcome aboard and all but man to say "3.73 (medium case) LSD for stage. There have been almost no times where I've wished for shorter gearing" is well sehr interessant, junge..

Maybe explain not what--you just said what, but 'splain to the Oh Pea and me : why you don't wish any shorter. Do you not like acceleration? Short gearing = free acc. (that's pronounced like 'axe' , short for acceleration) Of course with the pick-up truck like 1st gear ration go short and you make the 1st gear suitable for "loading onto trailer only" gear but fawkit just go 2nd thru 5th...

But please why?

lol you're a hoot! I wish I could find 4.55s or 4.88s (from the factory that is) I just don't have the green right now to drop on a custom unit. Also, I am GREEN meaning I have no rally experience so I figure stock and relatively low budget is best... for now any way.

Like I said and the new guy Josh said too: grass-o-cross, just 1st and second and have fun.
Anything will do.
Stage rally is another kettle of fish..

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turoc

Wilson had posted this the other day on FB:
http://www.motamec.com/motorsport-parts/motamec-parts/lsd-differentials-crown-wheels.html

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john vanlandingham

Like I said and the new guy Josh said too: grass-o-cross, just 1st and second and have fun.
Anything will do.
Stage rally is another kettle of fish..

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irish44j

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john vanlandingham

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irish44j

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Yeah, read through his whole build, don't know him personally but he seems sharp for sure. Ratio on mine? it's a 4.10 open, looking for a 4.10 LSD for all the torques.

Honestly you may be fine and/or better off with a different ratio - I run a 3.91 (small case) LSD for rallycross, and a 3.73 (medium case) LSD for stage. There have been almost no times where I've wished for shorter gearing, especially with the Conforti chip adding a higher redline. 4.10 LSD is fairly rare since (IIRC) they only came in the 318is from 1991, whereas the 3.73 LSD is pretty easy to find off the 6cyl cars made over many years.

Now that's nice but since you didn't put your first and last name--as is the one inflexible rule on this forum----we don't know who you are, or--since you didn't put you city and state (or Province) as is part of that same rule---we don't know where you are...and what you've done..
Reason I say that is cause the Intra-webz if swarming with all sorts of people and all the words look the same just one letter after another so the only way to weigh the words is by knowing who we're talking to, where they're from and what they've done..

I think this guy has a 4 cylinder..Lemme go look, OK,. Be right back.

Ok I'm back..Lookie at the piccie:


Welllp that thar shooooore looks like a 4 to me..In fact it looks just like the one I tore down just so I could measure the fawk outta everything with my trust super accurate electronic Very-nears..
Early version was 1800, later 1900. Not a particularly rip snortin' a-rootin and a-tootin' stump pulling, devastation wreaking motor (although plenty of potential just lurkin...brough ha ha!!!)
So one that seems like it could use some help making the carro scoot.

There is a pretty common correlation between engine size (assuming they kinda run and are no unusually big dogs), tire size overall and end use of vehicle--and final drive...

Now for grass-o-cross makes zero difference...its just more fun if a car has a bit of yank to it..
But for stage rally where 95% of what we do is 25mph to 90mph again and again and again all weekend...pretty typically a 2,0 motor making some beans on 13/14" tire might have 4.88 gears and same on short 62cm 15" tires we'd expect to see about 5,0 to 5.15 final drive..
Been that way for decades...
Of course that presumes a gearbox with ratios intended to do 25 to 90...not 30 km/hr oder vollgas immer gerade aus auf der autobahn! and mid-range sacrificed for top speed.

So welcome aboard and all but man to say "3.73 (medium case) LSD for stage. There have been almost no times where I've wished for shorter gearing" is well sehr interessant, junge..

Maybe explain not what--you just said what, but 'splain to the Oh Pea and me : why you don't wish any shorter. Do you not like acceleration? Short gearing = free acc. (that's pronounced like 'axe' , short for acceleration) Of course with the pick-up truck like 1st gear ration go short and you make the 1st gear suitable for "loading onto trailer only" gear but fawkit just go 2nd thru 5th...

But please why?

John, was just filling in my profile as you were posting about it, so no worries there.

Obviously I'm aware he has a 4cyl M42 car (as the car is a 318i), and since I've rebuilt a several of M42s (and have had one in my car for four years), I recognize them quite well.

As to the diff ratios, that's primarily personal preference. Since he is rallycrossing an M42 car, and I'm the currently the SCCA DC and NEDiv defending champion in an M42 318, I figure my personal preference has worked pretty well so am sharing my opinion on the matter.

From a more pragmatic point of view, the 318 3.91 and 4.10 are small-case diffs with two clutch packs (25% lockup) and less strength/fluid capacity. The 3.73 (and other 6cyl diffs) are medium case with stock 40% lockup and the option to remove the spacer and put a third clutch pack in for 60% lockup. I neglected to mention this because after all these years I don't even think about it offhand. But that's why we use the 3.73 for stage (which we are admittedly new at this year) - as well as the pick-up-truck first gear being entirely useless in an M42 car with higher ratios, as you mention.

As I mentioned for rallycross though, on most courses a 4.10 will require low 3rd with the M42/G240 on typical tire diameters. Low 3rd is not where he wants to be with this engine - losing time without torque and with extra shifts. With the 3.73 or 3.91 he can run entire courses in 2nd at most rallycross venues up high in the revs where the M42 makes all of its power, and not waste time with extra shifts. Not an issue on a stage course, but on a short rallycross course an extra shift or two could cost the win.

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john vanlandingham
In a way I'm trying to edjimicate the young Oh Pea, cause he like YOUNG and from Portland so while he can certainly splain me all about fixie bikes and skinny jeans and sideburns he probably doesn't understand too well about the role of gearing being a torque multiplier...or as i put it for the uber-mellow Waste coasters
"What the motor doesn't make for "ax", the gearing does".....

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formyhealth

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john vanlandingham
In a way I'm trying to edjimicate the young Oh Pea, cause he like YOUNG and from Portland so while he can certainly splain me all about fixie bikes and skinny jeans and sideburns he probably doesn't understand too well about the role of gearing being a torque multiplier...or as i put it for the uber-mellow Waste coasters
"What the motor doesn't make for "ax", the gearing does".....

Just so you know, I don't know anything about bikes, skinny jeans or sideburns (though I've got an excellent red beard) and Portlandians are to cool for me, I live in the capital of Oregon, Salem. You've got a couple things right though, I'm young and don't know shit about shit, which is good I guess, means I've got a lot of room to grow.

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john vanlandingham


And while I have know a few real cutinas who were very friendly in the best sorta way, in general I say "meh, a little too much striving for the detached, hip, cynical thing"

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formyhealth
Just so you know, I don't know anything about bikes, skinny jeans or sideburns (though I've got an excellent red beard) and Portlandians are to cool for me, I live in the capital of Oregon, Salem. You've got a couple things right though, I'm young and don't know shit about shit, which is good I guess, means I've got a lot of room to grow.

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Nate.Vincent
I just happen to have a small case e36 LSD differential with a 4:44 ratio. Only has 60K on it.

Interested?

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Nate.Vincent
I just happen to have a small case e36 LSD differential with a 4:44 ratio. Only has 60K on it.

Interested?

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Robert Culbertson

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formyhealth
Just so you know, I don't know anything about bikes, skinny jeans or sideburns (though I've got an excellent red beard) and Portlandians are to cool for me, I live in the capital of Oregon, Salem. You've got a couple things right though, I'm young and don't know shit about shit, which is good I guess, means I've got a lot of room to grow.

Not a whole lot of hipsters in Salem, just a bunch of mall rats. I grew up just outside of Salem in the Independence/Dallas area. There are some great roads out there if you know where to look.

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formyhealth

That's funny, I grew up in Independence as well (Went to Central High). I know there are some good roads back by falls city area.