Engine cylinder Technical Question

[jgendr]

The R1150 motors have a bore and Stroke of 101mm X 70.5mm where
The R1200 Motore have a Bore and Stroke of 101mm X 73mm

excluding the physical differences of dowel pins, The Jug's are physically the same but with a 2.5mm longer length correct? Has anybody that you know of ever tried an 1150 to 1200 conversion where that have swapped the 1150 jugs and heads with the 1200 jugs and heads?

I know this is not the normal procedures and way out of the scope of the engineering intentions but I have a really off the wall idea I'm playing with. The Compression ratio of the 1150 is 11.3:1 where the 1200 is 12.0:1. If my math is correct if one was to adapt the 1200 jugs onto the 1150 the result would be an additional 20cc's of chamber space. resulting in a new compression ratio of about 8.5:1. Is it feasible?

I really done want to get into a discussion as to why I'm barking up that tree and I can assume you have a good idea of why, I just don't want to debate the reasoning.

[sweatmark]

Um, difference in stroke means swap the crankshaft?

[jgendr]

Um, difference in stroke means swap the crankshaft?

No that is not my intention. I need to lower the compression from 11.3:1 to into the neighborhood of 8.5:1

I was just wondering if anybody on this board was more familiar with the differences between the jugs. being the stroke is different between the two

[towerworker]

Um, difference in stroke means swap the crankshaft?

Why would you need to swap the crankshaft? (assuming the jugs bolt up anyway) I'm not real sharp but it sounds like an intriguing idea. But wouldn't you want to change out connecting rods as well? What would be the benefit of simply changing the jugs resulting in a lower compression ratio and I assume reduced power?

[riceburner]

Wouldn't it be easier just to swap the engine for a R1200C motor?? (or possibly those cylinder/head assemblies).

[towerworker]

I remember the R1200C was a detuned version of the 1150. As I remember it had something on the order of 20 less hp.

[peels]

edited...I was going to ditto sweatmark.

I re-read it. I see what youre doing.... you want LESS compression. For forced induction of some sort im guessing...? I HIGHLY doubt anyone has done EXACTLY this yet. good luck!!! feasible, yes... but you might get to be a guinea pig.

is there not a lower compression piston that is available somewhere? that seems so much easier.. maybe shorter rods? if those weren't available, only then Id consider swapping heads.

this is my ATV world mindset though. :/ beemer stuff probably harder to mod or get a hold of. I even remember guys running thicker head gaskets so they could run more boost.

[riceburner]

I remember the R1200C was a detuned version of the 1150. As I remember it had something on the order of 20 less hp.

Any idea how? Maybe it was exactlyl as described above - simply a slightly longer cylinder to give lower compression? (adn slightly longer pushrods or primary chain)

[peels]

id bet its the piston, or rod. not the jug.

but its a guess. I was curious so I've been looking. not really much to go on. just that piston is a different part # between the two. the 1200c shares a piston with some 1100's and 850's.

http://www.ascycles.com/Illustrated_cat ... at=11_1832

now Im even more curious.

[jgendr]

Yes Peels; "HOT ROD BEEMER"

You guessed it, "Forced induction Beemer" when I bought the bike the guy was into Subaru's also and he had a Take off STI turbo that he through into the deal. So we're taking "Turbo Beemer"

In all the years of technical builds I've done the only way to increase stroke is a crank swap. Yes this may need rods and pistons to maintain clearances. For instance a 383 stroker motor uses a 350 block, 400 crank and special pistons to keep clearance to the head. the long stroke of the 400 crank is the gain in stroke. so that being said:

If the 1200 has a 73mm stroke and the 1150 has 70.5 stroke, "assuming" BMW was smart and follow best production practices the 1200 has to have a longer stroke crank same rods, same pistons but the jug's would be machined to the longer tolerances.

My scenario I am proposing keep the 1150 crank, rod's, and pistons "shorter stroke" but use the 1200 jug's, and heads "longer stroke" thus gaining in the neighborhood of 20cc's of combustion chamber. The resultant is a compression ratio reduction from 11.3:1 (stock on 1150) to approximately 8.5:1. This lower compression ratio is more conducive to Turbo or Super charging the intake. less chance of detonation, and less chance of blowing head gaskets. That is why I do not want to try stacking head gaskets in this situation.

Now here is the curve ball... I can also accomplish the same effect by shimming the base of the jugs about 100 thousandths gaining the same 20cc in the combustion chamber too.

Now strap on a turbo and start tuning from 5 psi of boost and see how far we can push it. Also there will have to be a wide Band o2 sensor and may have to go Megasquirt EFI. since these bikes use Bosch injectors stepping up is no big deal.

[peels]

Yes Peels; "HOT ROD BEEMER"

You guessed it, "Forced induction Beemer" when I bought the bike the guy was into Subaru's also and he had a Take off STI turbo that he through into the deal. So we're taking "Turbo Beemer"

In all the years of technical builds I've done the only way to increase stroke is a crank swap. Yes this may need rods and pistons to maintain clearances. For instance a 383 stroker motor uses a 350 block, 400 crank and special pistons to keep clearance to the head. the long stroke of the 400 crank is the gain in stroke. so that being said:

If the 1200 has a 73mm stroke and the 1150 has 70.5 stroke, "assuming" BMW was smart and follow best production practices the 1200 has to have a longer stroke crank same rods, same pistons but the jug's would be machined to the longer tolerances.

My scenario I am proposing keep the 1150 crank, rod's, and pistons "shorter stroke" but use the 1200 jug's, and heads "longer stroke" thus gaining in the neighborhood of 20cc's of combustion chamber. The resultant is a compression ratio reduction from 11.3:1 (stock on 1150) to approximately 8.5:1. This lower compression ratio is more conducive to Turbo or Super charging the intake. less chance of detonation, and less chance of blowing head gaskets. That is why I do not want to try stacking head gaskets in this situation.

Now here is the curve ball... I can also accomplish the same effect by shimming the base of the jugs about 100 thousandths gaining the same 20cc in the combustion chamber too.

Now strap on a turbo and start tuning from 5 psi of boost and see how far we can push it. Also there will have to be a wide Band o2 sensor and may have to go Megasquirt EFI. since these bikes use Bosch injectors stepping up is no big deal.

Now strap on a turbo and start tuning


I feel slightly more manly after reading this post. and ill be damned if I didnt just do the Tim Allen tool time grunt. more powa! lol

shimming with thick gaskets was done on atv's. so you can run more boost. or to eliminate detonation on a crazy build....Yamaha Raptor 700's.

weve left the realm of anywhere I can be of useful now though. LOL

[peels]

check this out.

someone was doing a SUPERcharged build here... not sure how or if it turned out....

maybe theres something useful in there?

http://r1150r.org/board/viewtopic.php?f=2&t=30181

[jgendr]

check this out.

someone was doing a SUPERcharged build here... not sure how or if it turned out....

maybe theres something useful in there?

http://r1150r.org/board/viewtopic.php?f=2&t=30181

Man that's a great build. it was right up my alley up until the point he fell off the face of the earth. i wish there was a way to get back in touch with him.

[sweatmark]

Quick google for head gasket :: CR

If you’ve never computed compression ratio before, this is worth experimenting with on a number of levels. For example, stroke has a much greater effect on compression than bore, which is why the short stroke/small displacement engines require such small combustion chambers. Other areas worth investigating are variables like gasket thickness. Replacing a thick 0.051-inch composition head gasket on a 350 with one of Fel-Pro’s 0.024-inch rubber-coated head gaskets can pump the squeeze factor from 8.68:1 to 9.16:1.

Read more: http://www.superchevy.com/how-to/46778- ... z3J0y6HJxA

Depending on piston and combustion chamber shape, your intended 2.5mm bump via R1200 cylinders might result in CR too low for 0.5-1.0 bar boost application.

I would probably change head gasket first, custom pistons second, to move CR for boost.

If you don't already have a copy, I recommend this if you can find it:
http://www.amazon.com/Motorcycle-Turboc ... 884313078/
Features a little info about the original R1100RS turbo.

During my Buell days, was inspired by this guy and his conscientious turbo development work:
http://www.streetfighterperformance.com
He provided project details on a couple of Buell enthusiast boards like BadWeb.

[peels]

whoa.

the streetfighter link. nice work, and a GREAT read. guys got some skill (and free time)

I want those CP custom pistons. not for my motor. I just want to put them in a glass display case and stare at them. GORGEOUS. LOL

[kirby]

custom pistons is the easiest way by far to lower the compression. (quite a decrease from stock!)

Although it would have to be well thought out any of the custom piston venders could do it but the cost would be up there for ...say a couple of sets. If others wanted to do it..the numbers would cut the cost.

Done this in aircraft engines

mike

[jgendr]

Anybody know of any tuning software that is capable of reprogramming the Motronis ECU's on these bikes?

[ROXTR]

Just a quick question for clarification's sake, when you're referring to the R1200 specs is it the oilhead or camhead engine?

FYI the 1150R/GS compression ratio is 10.3:1, the 1150RT/RS compression ratio is 11.3:1, the R1200C ratio is 10.0:1 with the only real difference being pistons (flat vs domed).

The difference in displacement between the 1150 oilhead and 1200 oilhead lies solely with the crankshaft, the cylinders are identical; 1130cc vs 1170cc.