TOPIC:

Some of the newer (late 80's early 90's) water cooled bikes run 11.5:1 compression ratio on 93 Octane pump gas with carbs.

How much engine management is it going to take to get one of these old air cooled mills running nicely with 11.5:1 and pump gas?

Would running a tad rich to keep the head temp down and an electronic ignition with a knock sensor be enough?

From David Cronenberg's movie, Scanners


Post edited by: Duck, at: 2006/11/24 22:35

have you compared the cranking compression? it may be similar with just a higher ratio. I agree that it is higher because of the 4 valves per cylinder and liquid cooling, but it might not be that much higher.
for extra cooling, mount a couple fans by the coils aimed at the head, run an oil cooler in the regular spot, and hide another one under the seat or tail or someplace, and put a rad fan on it from a new bike. running rich might help too, but it may be hard on plugs.
if you want to go really wild, make a custom billet cylinder block, and make that part of the motor water cooled

77KZ650 wrote:

have you compared the cranking compression? it may be similar with just a higher ratio. I agree that it is higher because of the 4 valves per cylinder and liquid cooling, but it might not be that much higher.
for extra cooling, mount a couple fans by the coils aimed at the head, run an oil cooler in the regular spot, and hide another one under the seat or tail or someplace, and put a rad fan on it from a new bike. running rich might help too, but it may be hard on plugs.
if you want to go really wild, make a custom billet cylinder block, and make that part of the motor water cooled

No, I'm comparing volumetric ratios. The compression ratio is a geometric number. It's the ratio of volumes, BDC+CC to TDC+CC (Bottom Dead Center plus Combustion chamber to Top Dead Center plus combustion chamber). So, a piston kit advertised as 10.25:1 in a kz900 can be compared with a 11.9:1 in a late model ZX or 11.5:1 in my 80's Honda 400. I'm not worried about being able to turn it over. Also, I do not have a clue what the dynamic CR's are in these different engines. Knowing would make it easier to compare.

I was thinking that it might be possible to modify a GS1150 16V head and clean up the casting at the bottom of the fins with a round mill and press Aluminum tubing in for water cooling, but that's way more work than I'm interested in. As an aside, it might be interesting to look at a total loss water cooling mod to an air cooled head for drags. Weld up chambers around the fins. Add a chimney. Fill with water.

Basically I want to get the compression ratio as high as I can and still run on 93 octane pump gas. If I can get 11.5:1 with a 'smart' ignition system, then great. If the best I can do is 10.5:1 and I can get to 11.5 or 12 to one using fuel injection AND smart ignition, then I'd be willing to spring for a megasquirt kit.

I was hopng someone had already looked into or was doing this...

Post edited by: Duck, at: 2006/11/24 09:35

Post edited by: Duck, at: 2006/11/24 09:38

This is just so complicated to explain, that I doubt I can do it before my two typing fingers fall off

First off, ignition is advanced as the rpm increases (up to around 3600-3800 rpm) so that the mixture will have time to burn before the piston reaches BDC. If you have to retard the ignition to compensate for the higher compression ratio, you will loose power compared to a lower compression ratio with proper timing.

Secondly, calculated compression ratio is only useful for bragging rights, dynamic ratio is all that matters. It is entirely possible to build a motor with 10:1 calculated compression ratio that has a higher dynamic compression ratio (and has to run higher octane or less advance) than a 13:1 motor.

Third, the upper limit on dynamic compression ratio is the amount of heat that the cylinder and head can transfer to the surrounding air, and the octane of the available fuel.

In no particular order:

Cylinder filling is a very important factor in determining maximum compression ratio, with 24mm carbs on a 1170 motor you can probably get away with a 13:1 ratio on pump gas, as long as you keep the rpm above 5k. The small carbs will restrict the cylinder from filling completely and result in a lower dynamic ratio. The same thing applies to cams with lots of overlap, or that delay intake closing, the first allows mixture out the exhaust while the second pumps it back into the intake, Chevrolet used the second method in their hot rod 360-375 hp 350's in the late 60's and early 70's.

Combustion chamber design has a lot to do with it as well, the combustion chamber in the Jaguar V12 HE motors allowed them to run a 12.5:1 ratio on pump gas. The hemi chamber in the KZ's is pretty much the worst kind to use for high compression.

And I'm not even going to get into rod length ratio and it's effect.

Best advice I can give is to stick with proven combo's, unless you have the time, money, and facilities to do the research involved to extend the "Bleeding Edge" of technology

There is a whole lot more that could be said on the subject, but my two typing fingers hurt

I just remembered that Speedomotive has some info on the subject.

Post edited by: steell, at: 2006/11/24 12:46

steell wrote:

This is just so complicated to explain, that I doubt I can do it before my two typing fingers fall off

First off, ignition is advanced as the rpm increases (up to around 3600-3800 rpm) so that the mixture will have time to burn before the piston reaches BDC. If you have to retard the ignition to compensate for the higher compression ratio, you will loose power compared to a lower compression ratio with proper timing.

Secondly, calculated compression ratio is only useful for bragging rights, dynamic ratio is all that matters. It is entirely possible to build a motor with 10:1 calculated compression ratio that has a higher dynamic compression ratio (and has to run higher octane or less advance) than a 13:1 motor.

Third, the upper limit on dynamic compression ratio is the amount of heat that the cylinder and head can transfer to the surrounding air, and the octane of the available fuel.

In no particular order:

Cylinder filling is a very important factor in determining maximum compression ratio, with 24mm carbs on a 1170 motor you can probably get away with a 13:1 ratio on pump gas, as long as you keep the rpm above 5k. The small carbs will restrict the cylinder from filling completely and result in a lower dynamic ratio. The same thing applies to cams with lots of overlap, or that delay intake closing, the first allows mixture out the exhaust while the second pumps it back into the intake, Chevrolet used the second method in their hot rod 360-375 hp 350's in the late 60's and early 70's.

Combustion chamber design has a lot to do with it as well, the combustion chamber in the Jaguar V12 HE motors allowed them to run a 12.5:1 ratio on pump gas. The hemi chamber in the KZ's is pretty much the worst kind to use for high compression.

And I'm not even going to get into rod length ratio and it's effect.

Best advice I can give is to stick with proven combo's, unless you have the time, money, and facilities to do the research involved to extend the "Bleeding Edge" of technology

There is a whole lot more that could be said on the subject, but my two typing fingers hurt

isnt he dreamy?types with 2 fingers,when the rest of us have to use just 1!

Duck, why noy just run E85 it is 105 octane and can sustain 13:1 stactic even with a little overlap (high dynamic cr).

Its as easy as enriching the mixture by 30% and youll see a great improvement in power due to the increase in compression along with cooler running temps from the alky.

In Atlanta E85 can be had at PS Energy they are located at 340 Whitehall street sw.

Peace&love;) , Darren

Post edited by: kyradawg, at: 2006/11/24 12:57

Post edited by: kyradawg, at: 2006/11/24 13:18

Post edited by: kyradawg, at: 2006/11/25 11:46

steell wrote:

...calculated compression ratio is only useful for bragging rights, dynamic ratio is all that matters. It is entirely possible to build a motor with 10:1 calculated compression ratio that has a higher dynamic compression ratio (and has to run higher octane or less advance) than a 13:1 motor.

Thats what I was talking about here, Steve just knows the technical terms
77KZ650 wrote:

have you compared the cranking compression? it may be similar with just a higher ratio. I agree that it is higher because of the 4 valves per cylinder and liquid cooling, but it might not be that much higher.

Scott

KD-

Thanks. I did not know e85 was available in Atlanta. Will have to read up. Want to make sure there are no corrosion problems. Heck, it may be just the excuse I need to use these gas ported pistons...

Thanks for the long message too. I grok that detonation occurs when pressure-temp combo reaches the right point for the fuel-mix and that it's a bit of a bear to model in a real combustion chamber. This business about combustion chamber shape. WAG, for the hemi, the dyamic pressure distribution has a peak at the focus???

As an aside...Do you happen to know the density of the deuterium plasma in a Farnsworth neutron generator?

Post edited by: Duck, at: 2006/11/24 13:53

Duck wrote:

...As an aside...Do you happen to know the density of the deuterium plasma in a Farnsworth neutron generator?

Depends on the target atom...

Fusion of deuterium atoms (D + D) results in the formation of a He-3 ion and a neutron with a kinetic energy of approximately 2.5 MeV. Fusion of a deuterium and a tritium atom (D + T) results in the formation of a He-4 ion and a neutron with a kinetic energy of approximately 14.1 MeV.

Pterosaur wrote:

Duck wrote:

...As an aside...Do you happen to know the density of the deuterium plasma in a Farnsworth neutron generator?

Depends on the target atom...

Fusion of deuterium atoms (D + D) results in the formation of a He-3 ion and a neutron with a kinetic energy of approximately 2.5 MeV. Fusion of a deuterium and a tritium atom (D + T) results in the formation of a He-4 ion and a neutron with a kinetic energy of approximately 14.1 MeV.

wireman wrote:

Pterosaur wrote:

Duck wrote:

...As an aside...Do you happen to know the density of the deuterium plasma in a Farnsworth neutron generator?

Depends on the target atom...

Fusion of deuterium atoms (D + D) results in the formation of a He-3 ion and a neutron with a kinetic energy of approximately 2.5 MeV. Fusion of a deuterium and a tritium atom (D + T) results in the formation of a He-4 ion and a neutron with a kinetic energy of approximately 14.1 MeV.

Well, Duck asked....

Plasma is an atomic nucleus stripped of its electron shell. A Farnsworth Neutron Generator creates neutrons by slamming atomic isotopes of hydrogen - "deuterium" or "tritium" together at high speeds. The reaction generates a neutron, and and He-3 or He-4 ion (helium plasma) as leftovers. Simple.

That clear things up for ya?

Pterosaur wrote:

wireman wrote:

Pterosaur wrote:

Duck wrote:

...As an aside...Do you happen to know the density of the deuterium plasma in a Farnsworth neutron generator?

Depends on the target atom...

Fusion of deuterium atoms (D + D) results in the formation of a He-3 ion and a neutron with a kinetic energy of approximately 2.5 MeV. Fusion of a deuterium and a tritium atom (D + T) results in the formation of a He-4 ion and a neutron with a kinetic energy of approximately 14.1 MeV.

Well, Duck asked....

Plasma is an atomic nucleus stripped of its electron shell. A Farnsworth Neutron Generator creates neutrons by slamming atomic isotopes of hydrogen - "deuterium" or "tritium" together at high speeds. The reaction generates a neutron, and and He-3 or He-4 ion (helium plasma) as leftovers. Simple.

That clear things up for ya?

well yeah i feel much better now!