[raderj]

So the stock UCE has 8.5:1, right?  Anyone know what the 535 piston kit that comes from nfieldgear raises it to?

Also, what is too high for the UCE if you run 91 octane?  It seems to me like it could get up to 10:1 or so because other aircooled bikes do it.  Am I missing something?

[Maturin]

radarj,
What would you like to acomplish exactly by getting up to 535cc? Which mods are allready in place at your bike? Regards

[raderj]

My bike is only 2000 miles old, so no fast modifications are in place yet.  I do want to pep it up in the future, so I'm just doing research.

Here's an idea of what I would like to do if I could afford it:

535 piston ($80 to bore cylinder from a good guy I know)
19t sprocket
Air box removal, install K&N
Goldstar muffler
Power Commander (has anyone got this to work on an Enfield?)
Polished head
Bottom end work (if Ace figures out if it's necessary  )

Just dreaming though.  Right now I want to know about compression ratios!

[barenekd]

If you want to bump compression without the bore job, get an Electra piston.
Bare

[raderj]

Yeah, I know about the Electra piston.  It has a flat top so it increases compression.  I kind of want to go "all out" on my bike eventually.  That's why I want the 535.

[Arizoni]

Although it's just holding my thumb up (and my calculator fingers down), going from a 499cc displacement to a 535cc displacement would raise the compression from 8.5:1 to 9.11:1.

I would guess that a 91 octane fuel should be able to deal with that?

[SimonT]

My bike is only 2000 miles old, so no fast modifications are in place yet.  I do want to pep it up in the future, so I'm just doing research.

Here's an idea of what I would like to do if I could afford it:

535 piston ($80 to bore cylinder from a good guy I know)
19t sprocket
Air box removal, install K&N
Goldstar muffler
Power Commander (has anyone got this to work on an Enfield?)
Polished head
Bottom end work (if Ace figures out if it's necessary  )

Just dreaming though.  Right now I want to know about compression ratios!

Wow... i would love to do this.

Has anyone actually done significant work to a UCE?

[jartist]

Keep in mind that the 535 piston isn't dished.  By my calculations just going from the efi piston to the avl flat top piston gives you a 9.5:1 ratio.  If the piston tops out flush at the top of the barrel the 535 should give about a 10.3:1 ratio.  I've made a few assumptions and guesses concerning measurements and calculations but it should be in the ball park.

[raderj]

Some factors that come into whether an engine knocks are what the piston and head are made of, right?  Does anyone know if it would knock at 10.5:1?  The head is aluminum alloy of some kind, I'm guessing. Another gasket on the head would probably lower it enough if 10.5:1 is too high.

[jartist]

The AVL piston in the EFI supposedly did fine with low octane.  If the 535 really does approach 10.5:1 (it may end up being a bit lower if anything), your starting to get into mid to high octane gas range but shouldn't be a problem there.  The nice thing about starting with the AVL piston is that you can go back to stock if you want.  You'd have to get a new barrel to return to stock if you went to a 535 and didn't like it.  An AVL piston shouldn't take more than an afternoon to install.

[raderj]

That's true, but when I do eventually do this, I'm going all out! That's the plan anyway.  I want to make bike that can do the ton easily.  My bike feels good at 84 indicated already.  What's 16 more mph among friends?

[ROVERMAN]

Er? A bigger fine?

[Maturin]

Is a twin spark possible in a UCE? This could solve the problem of high compression knocking, would probably add lots of torque and save the fuell efficience (at least partially - not so important as we´re talking ´bout THE TON, right?). If you like to take a closer look at the head anyway, have an aditional look if there´s enough space for a second plug hole.
In India there is a 350 Thunderbird Twinspark, so why shouln´t that be possible with our 500?

[Arizoni]

The head on my 500 UCE has an unmachined spark plug boss.

I'm not sure how they handle the coil(s) on the TS.  I would guess they have 2 of them?

[TWinOKC]

Hey raderj,

All the mods you have suggested sound good to me.  Go for it young man!
Looking forward to hearing the results of your planned modifications.

Personally I don't have the balls to ride a RE 100 mph.

I wish you good luck.  

Terry

[Ducati Scotty]

You can put a twin spark in a UCE.  One of the ISM models has it.  Easy mod, just drill and tap the hole and get a Harley dual spark coil.  I've seen it done but there weren't any major performance gains.  It might help get more thorough combustion in remote areas where'd the quality of the gas is marginal.

Scott

[Arizoni]

Twin spark plugs reminds me of the Auxiliary Power Unit we designed for the Boeing 777.

We decided that because of the high altitude starting requirements to meet the aircraft's  ETOPS requirement we would design it with two igniters in the combustor.

During the Critical Design Review one of the Boeing reliability engineers popped up and pointing at the dual igniters said, "You've decreased the reliability of the ignition system by 50%.
With two igniters, the probability of a failure is twice as high."

One of our engineers countered with the obvious by pointing out that if one igniter failed there would still be one left to start the engine thus the likelihood of the APU starting was twice as high.

The units final design has two igniters.

For those curious, ETOPS is a FAA requirement for commercial aircraft with only two engines which will fly long distances over the ocean.
If one of the main engines fails the APU must be able to start and extremely high altitudes to take over the planes electrical requirements and to provide bleed air to restart the non-running engine.
With the APU providing the electricity, the remaining main engines generator can be shut down allowing it to be dedicated to just providing propulsion.

Officially, ETOPS stands for, "Extended-range Twin-engine Operational Performance Standards"  but we jokingly said it meant, "Engines Turning Or Prepare to Swim".

Getting back to the twin spark on a Royal Enfield, I agree that there is not much to be gained by using two spark plugs.
Twin plugs have a better chance of igniting crappy fuel or a fuel mixture that is badly out of adjustment but assuming there is not a misfire the other spark plug is basically just going along for the ride.

[raderj]

I feel if you have the proper piston and head shape for the "quench zone", that all the fuel will burn properly with one spark plug.  Not many internal combustion engines use twin spark plugs because the engineers design proper areas for the fuel/air mixture to burn.

If your chamber is all misshapen then not all the fuel will burn before the piston reaches BDC.  The 535 piston had a flat top, so this shouldn't be a problem.  It happens more with domed pistons that are "too high".  Like this:

[digstuffup]

I've been making plans along similar lines, higher compression piston + adding twin spark.
I was told that two ignition sources can also help compleat combustion in the cylinder to occur more rapidly.

[raderj]

I'm not sure if it will help or not.  It makes me wonder when high performance manufacturers and tuners don't utilize the two spark plug technique though...

[digstuffup]

alfa romeo use it.

[barenekd]

Airplane engine use twin sparks as a safety measure, in case one ignition system fails the other will keep running. There is a definite advantage to have both of them operating together, though. There will be a definite rpm and power drop if one of them is shut down.
Bare

[Desi Bike]

I had a 1982 Datsun/Nissan 200sx that was a twin spark. The manufacturer only really used it to help with emmissions. The second spark would burn up what was left unburnt.

Instead of carving up a head to add another spark plug, why not give an MSD 4217 ignition a try.  (Multiple Spark Discharge.. its like having many higher than stock sparks instead of just one at firing time.) Summit Racing lists them for $302, I know its a bit pricy, but atleast you wont have to replace the head if your plan doesnt work. The MSD could be resold if you dont acheieve what you are after and still have an intact head.

Read more here....
http://www.mpsracing.com/instructions/MSD/4217.pdf

[tooseevee]

I had a 1982 Datsun/Nissan 200sx that was a twin spark. The manufacturer only really used it to help with emmissions. The second spark would burn up what was left unburnt.

                     If that's true then the two sparks would have to happen at two different times with the 2nd spark retarded a certain number of microseconds. Whether there is one plug or two, unless they fire at different times, once the fuel/air mixture is burning, it's burning.

[raderj]

That MSD is pretty cool. You can program it and everything.  Know of anyone running it?

[Desi Bike]

I ran a MSD 6AL in a big V8 that I had in a monster truck in my redneck days. I was quite impressed with it, but I have no experience with the 4217.

[GlennF]

alfa romeo use it.

Mercedes Benz as well.

Two common applications of twin spark plugs are:
- high boost supercharged engines
- engines with oval pistons (for example the Honda NR750 with 8 valves and two spark plugs per cylinder).

[ace.cafe]

There is quite a lot to bite-off and chew with this subject.

After 5 years and 20 engines, I'm still probing the upper limits of the Iron Barrel compression potential for street use.
My recommendation is if you are thinking about trying something, keep it into the 9:1 range, or thereabouts. The existing fuel for the street really isn't that great.
If you can use alcohol or race gas, then go for whatever you want.

[barenekd]

There is a definite advantage to have both of them operating together, though. There will be a definite rpm and power drop if one of them is shut down.

Understand, though, most airplane engines have something in the neighborhood of 5" bores, so their flame front takes longer getting from one side to the other. The two plugs cut at flame front distance in half, ergo, the power gain using twin ignition. Using the standard mags, it's highly unlikely that the two plugs actually fire simultaneously as the timing method isn't that accurate. Close, but no cigar.
Bare

[raderj]

After 5 years and 20 engines, I'm still probing the upper limits of the Iron Barrel compression potential for street use.
My recommendation is if you are thinking about trying something, keep it into the 9:1 range, or thereabouts. The existing fuel for the street really isn't that great.
If you can use alcohol or race gas, then go for whatever you want.

The UCE isn't an iron barrel, is it?

[Ducati Scotty]

No.  Iron barrels are the original engine for the Royal Enfield.  The cylinder is literally made of cast iron and the compression ratio is around 5.5:1.  Next came the AVL, Advanced Lean Burn.  Pretty similar design but the cylinder was steel lined aluminum alloy and the compression ratio was higher, 8.5:1 I think.  Last and latest is the UCE.  A similar design but with many new featues: hydraulic lifters, electronic ignition, electronic fuel injection, and Unit Construction.  Unit Construction means the engine and transmission share the same lubricating oil.  They were separate in the earlier designs and still are in Harleys and a few other bikes.  Each of these iteration runs cleaner and is more powerful than the last.

Scott

[Gregorin]

Oh, my man!
 I had a compression ratio of 11:1 This thing works! Enfield is becoming a monster compared to Yamaha F6, but ...
 What thou shalt not, and I could not I stand on the bike are ...
 very large and annoying vibrations. After driving just 30 miles You will not feel anything in my fingers on the hands, for example. It has been my experience. So I took off my clip is enabled, cam, which were a requirement for high performance. Now it is in the machine compression ratio 6,5:1 and the original cam on it.
 But think about how to install pistons 9:1 compression, camshaft competition, which lie in the closet. Perhaps to make it bearable option.

[Maturin]

I just mentioned the possibility of a twin-spark-ignition system, because it may help to avoid motor pinging. That happens frequently when compression is raised, and today you often simply don´t know what kind of fuel you´re actually burning.
A more serious effect may affect the low end, whose load will be raised considerably with raising compresson. Ace mentioned a special  bearing that could suffer and he didn´t know about it´s quality. I don´t remember it - anyone does?
Gregorin, is your bike a UCE? Hard vibes are not a good sign as they´re hitting the bottom end equally hard. Regards

[GlennF]

A more serious effect may affect the low end, whose load will be raised considerably with raising compresson. Ace mentioned a special  bearing that could suffer and he didn´t know about it´s quality. I don´t remember it - anyone does?

He was worried the bigend might suffer the same problems we saw with the AVL/Electra engines.

Basically in at least some of the AVL's the big-end rollers run directly on the con-rod rather than in an outer race and tended to fail under load (as the conrod eye is too soft). The design is both more likely to fail and likely to fail more catastrophically than a big-end using outer races.

The concern is the same design (possibly with a hardened conrod eye) may have been used in the UCE engine. Hence IF it should turn out the UCE actually still uses an AVL style bottom end, then a bottom end rebuild (potentially with a better conrod and big-end) would be a judicious move before increasing compression too much.

On the other hand if the UCE bottom end is a new design there is probably nothing to worry about.

[raderj]

I just mentioned the possibility of a twin-spark-ignition system, because it may help to avoid motor pinging. That happens frequently when compression is raised, and today you often simply don´t know what kind of fuel you´re actually burning.

You do if you run Trick