BMW K1100LT and k1200RS cam specs
Turbo Mini Forums

Hello people, Just ran to the next town and had both the K1100 LT cams and the K1200 RS cams run on a cam doctor. So many specs out there and inaccurate numbers So here is what i found out. First the cams are identical intake and exhaust. Even though they are marked differently the indexing on the cam gear must be the difference. Second the duration is seat to seat. in other words the LT 256 duration is exactly 256 @.006 which is the lash. This is important if you are trying to figure out your dynamic compression. LT cams 256 degrees seat to seat. intake opens approximately 22 btdc closes 54 abdc overlap 44 at 106 LSA.
RS cams are 284 @.006 36 open 68 closed overlap at 106 LSA is 72
Turns out the cams cannot be welded because of the material and the fact they are hollow.
It looks like i have to get two sets of RS cams to regrind them. Anyone have set.? Aaron

Edited by hydrolastic on 21st Nov, 2014.

Racecar spelled backwards is Racecar

Good info. Where are you located then? And why do you need two sets???

Hello turbo dave. I have i set already, three engines one for me one for a guy in my club and one to blow up! the mini my race team runs in the 24 hours of leMons races where we run the cars till they finish or blow up! Seattle Wa USA

Racecar spelled backwards is Racecar

Excellent info, Thanks for sharing

Yes i moved to the darkside

Instagram @jdm_brett

Aaron , you wouldn't have the .050 timing would you ?

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

also, peak lift?, as it's be the easiest way for people to check,

Good info but the Rs cam overlap value needs ajusting since factory bmw timing is 102/106

im guessing at 205 to 211 and 233 to 239.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Hello, So tested two lobes on each cam so there is a little bit of a difference even though the cams look excellent. These are the largest lobes.
The timing for .050 is
LT 216.1 duration .313 lift
RS 239 duration .346 lift

Racecar spelled backwards is Racecar

LT Specifications:
Intake duration 256@ .006 (@050 216)
intake valve lash 0.15...0.20mm (0.059...0.079)
Exhaust duration 256 Same as intake
Exhaust valve lash 0.25...0.30mm (0.010...0.012)
Lobe separation 106
Advance 0
Calculations: (these numbers calculated)
Intake open BTC 22
Intake close ABC 54
Exhaust open BBC 54
Exhaust close ATC 22
Intake center 106
Exhaust center 106
Degrees overlap 44
Lift .312 7.92mm
RS Specifications:
Intake duration 284 @ .006 239 @ .050
intake valve lash 0.15...0.20mm (0.059...0.079)
Exhaust duration 284 same as intake
Exhaust valve lash 0.25...0.30mm (0.010...0.012)
Lobe separation 104
Advance 2
Calculations: (these numbers calculated)
Intake open BTC 40
Intake close ABC 64
Exhaust open BBC 68
Exhaust close ATC 36
Intake center 102
Exhaust center 106
Degrees overlap 76
Lift .346 8.71mm

Racecar spelled backwards is Racecar

So guys, Here is the DCR calculator that i use
http://www.corvetteforum.com/forums/c6-tec...#post1567653356 post #28
The calculator is seat to seat numbers with 0 valve lash (I asked him) which is why i went to the cam doctor to measure the cams. A lot of cams state duration without lash and on a mini five port you can lose 4 to 8 degrees on each end of a cam lobe. To use it you just put in stroke and rod length. You can also go to the 60 number in the left column put in 50 and the rest changes in order. if you have a lower compression you can enter it in one of compression boxes.
The american two valve engines are said to run on 91/92 octane (95 ron) at 8.5 DCR. But i ran the lemons mini at 8.75 DCR on 92 and 175 psi cranking pressure 59 degees IVC. The stock bmw runs about 9 DCR It is commonly said that a 4 valve aluminum head can run 9.5 The honda guys say that you can run into the 10's DCR ( the head chamber is similar to the BMW) I have spent hours on it and it really lets you know where your engine is at.
Then you measure your chamber and your dish enter all those numbers in this calculator
http://www.pcengines.com.au/calculators/Ca...omp%20Ratio.htm
Manipulate these numbers till you know how much to grind out of the head and or piston. Thats it! Aaron

Racecar spelled backwards is Racecar

blimey ,thats a hell of a ramp on the 256 ,
thank you aaron very usefull data.

regards

robert

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Great stuff.
One question, are the ramps each side of full lift equal too, as we are running the cams backwards on the mini. If so would that effect the best timing, or even wear things out quicker.

Yes I'm pretty sure the cams are symetrical

Yes Nick, Symmetrical, both sides the same. Interesting thing the cam grinder told me was that the lobes are ground flat and the way they get the buckets to spin is to have the lobes just off center to the center of the bucket. He said that they have had buckets that didn't spin and it is just to make the wear even in the bore. I also have checked on bucket availability and the BMW dealer says that the buckets range from 2.55 mm to 3.2 mm in .05 increments. They are however 25 dollars apiece and if you need 16 thats 400 dollars! So this regrind could get expensive. Aaron

Racecar spelled backwards is Racecar

talk to SC they have quite a few buckets and might be willing to do some swapsies

Shave the valve stems and fit lash caps

Yep a very expensive regrind! I'm sticking with the standard LT cams n lifters the head came with, it runs nice and quiet.
Although now armed with your info on the cams I'm going to run through the timings again and see how close my guesstimate was. I aimed to set mine for about 10degs before n after tdc, about 106(coincidence) full lift. Although not to scientifically.

Ok, So i have done a little bit of research combined with the cam grinders recommendations looks like a 262 duration with a 106/106 would get a 57 ICA right where i want to be for a static comp of 11 and a dynamic of 9.16 It gives me the option of advancing the cam to 1 or 2 degrees and increasing the lca to 107 to raise the dynamic CR since the big race is held a track that is 400 feet which will lower it to 9.14 dynamic CR. which is exactly where a BMW k1200 RS runs at so i can run it on 91 octane or 95 ron.

Racecar spelled backwards is Racecar

Hydrolastic what other engine specifications have you got or have decided on. You going forced induction? Fuel injection?

So Nick, Three engines each one with a different purpose Mikes engine is getting fuel injection and will be on his five speed he wants a rock steady idle and no flat spot off idle. He is also an accomplished track day driver and wants power like his 1460 MED engine he has in the car now. It will use the SC typhoon ecu as he is familiar with the system. All three will use the bmw gasket because we can raise and lower the CR by removing and adding layers, Mikes is getting the 10.8 compression ratio and mine will be 11 or 11.1 and the race engine will get 11.5. I just got a second gear for the wide ratio double groove gear set so i intend to use that with a 3.1 FD in my car I will be using fuel injection as well but i am using the self learning system cause i am a technology nitwit. The race engine will get a carb however, I think i will use a HIF 44 on a plenum and runner setup similar to what the turbo guys use. It will get a welded crank and Mike and i both ordered fully counterweighted cranks from heritage Garage. They will take any power we can throw at them and are dead smooth as well. Perfect if i want to turbo or supercharge it later. This is a long term project as we only just ordered the cranks and it will be 3 to 6 months before we get them. But i hope to have everything else ready by then and since the race engine gets a regular crank it should be ready and running by june. Lots of stuff to do. Build deck template and narrow the rods offset bore the block etc. Kind of bummed EFI minis disappeared as i remember there was a lot of khead people there. Thats it for now.

Racecar spelled backwards is Racecar

Already did the center main bearing strap and the ARP bolts

Edited by hydrolastic on 29th Nov, 2014.

Racecar spelled backwards is Racecar

Here is a photo of the crankshaft

Racecar spelled backwards is Racecar

Well, that looks tasty.