Any interest in cams?

[Bheezy27403_imp]

Well done sir. Some actual testing done in the correct order. So often you see these things done willy nilly. Looking forward to the rest of the results.

[PowerDubs_imp]

I honestly do not think there would be any benefit to straight timing the cams.

The stagger is only on the intake cam, the exhaust is already normal.

It would be an awful lot of work for probably a difference of one or 2 hp while loosing the wonderful sound the engine makes the way it is currently designed.


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[beardyweirdy@me.com_imp]

Actually, why would the ign timing be delayed for Cyl 1&2?
If they are evenly spaced no the crank shouldn't they fire at the same point?

Unless they are off set on the crank... just thinking...

[PowerDubs_imp]

I'm going to guess the crank timing and TDC is the same across all 4, but only the factory knows for sure.

While a normal engine times the ign across all cyl a certain degree BTDC, changing the cam timing can change where optimal ign timing is set. But just like the cam timing being slightly mismatched, having the ign timing off a bit in either direction isn't a big deal- unless you advance enough to detonate (not pre-ignition).

You can rock most settings slightly- cam timing, ign timing, fueling rich or lean to little effect.

Heck, for all I know just by changing the duration and lift- therefor effecting the charge pressures, maybe overlap, scavenging, etc- it is possible the factory ign curve will no longer be optimal as is. I don't care- and wouldn't expect it to make a huge difference anyway.

There are soo many variables to engine design, operation, modifications, tuning. Luckily in modern computer designed engines as long as you don't stray far from what the factory designed not much of that matters in the real world. It is when you start pushing the limits that it really takes on a whole new world of complication.

Example- I am leaving the cam timing alone. I am not putting in huge cams. I am not raising the rev limiter.

So- I shouldn't have to worry about valve float, valve spring coil binding, piston pocket clearance, but stuff still changes- cams allow more air, which needs more fuel, but I am *possibly* also lowering my dynamic compression ratio at lower rpm (static will stay the same)..and might be increasing it up top due to scavenging and velocity. All depends on overlap which I admittedly haven't bothered to delve into.

I could spend a LOT of time doing all sorts of calculations and measurements, tearing my engine apart or buying pieces off Ebay for benchwork- but I've been doing that for decades and luckily have learned enough to know when it matters and when it doesn't.

This is by no means a race bike. There are plenty of bikes now if you want 200hp.

For what I am trying to achieve- just a more natural old school engine breathing before emissions and cats required very mild cams and lean fuel limiting both power generation and cooling purposes on our air cooled.... nothing extreme is needed.

I think 100whp will be broken though.

[beardyweirdy@me.com_imp]

Roger that... looking forward to the results coming in.

[use2b_imp]

just throwing this out there.
I read that during development of this engine they had a problem with the heads cracking because of the heat from the top of the combustion chamber. their fix was this oil cooler cooling the top of the combustion chamber in the head. I am wondering if more HP would result in a cracked head ? i would love to hear about HP gains as i love that stuff but would never consider it myself as it would definitely rob my off the bottom straight up torque curve i love so much. I generally shift at 2500 RPM anyway. keep us posted , like i said i like to hear about advancement and engineering.

BTW - the largest HP gain i have seen posted comes from the wyvern 4 into 4 exhaust with 90.8 HP at the rear wheel posted on samurider cb1100 website
I find it hard to believe that a 13 HP gain is made by these pipes myself but mine is a very strong runner

[PowerDubs_imp]

I don’t expect to loose much, if any low end power with what I am doing.

I also don’t expect to have any reliability issues from heat for 2 reasons- I will not have to worry about staying lean or the cat.

Since I do not have the limitations Honda did- no emissions, I can cool with fuel just like in the old days.




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[emullick_imp]

My shop manual for '13 and '14 CB 1100 shows cam timing:
Intake Opens at 1 mm 5 degrees ATDC
Closes, # 1 and 2 28 ABDC
#3 and 4 38 ABDC
Exhaust opens 42 BBDC, closes 10 BTDC
Strange, but making changes will affect many other things.
Personally, I will not try to re-engineer the engine.
There are lots of other bikes to choose from.
On my CB 750 I had Yoshimura 812 pistons, new cam, and he flowed the head.
Back then there weren't nearly as many bikes to choose from.

[use2b_imp]

PowerDubs = some very good points i did not consider.

[PowerDubs_imp]

I’m not reengineering. Just adding a little more lift and duration. Easy Peasy.


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