Twin Plugged Heads

[motoguzznix]

@ SP838

 

Sorry, my Emailadderss has changed, please resend to my new one:

 

motoguzznix@live.at

[Skeeve]

While I don't have any advice how much and in which areas (rpm/TPS) the ignition should be changed, it definitely should be retarded.

 

Looked into this question some years ago. The "8deg" # that has been bounced around in this thread comes from the difference btw the 37deg max advance on a stock V11 and the 29deg quoted by someone who had dual-plugged a v11 Sporti, iirc [Carl Allison mebbe?] Again, this is all "iirc," & you know how that goes, I've got an advanced case of CRS...

 

Anyway, the reduction at max advance wouldn't apply down around idle, so you can't reduce the map everywhere by that same amount. For the built in advance, it would probably be worthwhile to base it upon the same amount of starting advance from say, a small displacement 4-valve engine w/ centrally located spark, & see how it idles [smoothly or not?] Take a temp reading of the exhaust headers before the changes for a baseline comparison after: the readings should remain the same. If the exhaust is cooler, the timing is too advanced & too much heat is being retained in the head; if the pipes are hotter, the timing is too retarded & too much heat is being generated by the gases after they exit the cylinder.

[Skeeve]

Last summer, I talked to someone that had Mike Rich pistons in his V11 Sport, and he said the compression was a bit higher, AND his pre-ignition or pinging went away as well. I'm not sure if those pistons are domed differently or more efficiently , or what exactly caused the pinging to stop.

 

For some reason, I thought one of the V11 variants had dual pugged heads. If they do, you could probably utilize that ignition map to some extent. 

Ken

 

WRT the MR pistons: yes. There's a long thread about it from back around 2004? or 2005? maybe: the basics of it are this: Guzzi/Aprillia redesigned the combustion chamber on the V11 heads vs. the shape used in the 1064 motor used in the Spot/Sporti v11s, but apparently funds ran out or someone forgot to update the piston to match, & they kept on w/ the same pistons as before, so there was a mis-match in the squish zone, leading to all sorts of poor combustion issues, along with lower compression than was actually claimed by the factory. Mike Rish noticed this disparity, and came up with a set of pistons to better match the V11 combustion chamber [basically, finished the job the factory left undone.] So they actually produce the 10.5:1 CR the factory claims for the V11 motors, and do so by eliminating the "dead zones" of trapped, unburnt gases out at the perimeter of the squish zone which leads to lower emissions, better fuel economy & reduced pinging from a more turbulent combustion chamber at peak compression.

 

No V11 motor came w/ dual plugs. Dual plugging of V11 motors is more complicated than the dual-plugging of the old round-head twins because of a rerouting of oil passages with the square-head redesign. It can be done, but hardly anyone has bothered due to the added expense and difficulty of reprogramming the electronic ignition [until recently] vs. the comparative ease of changing advance in a distributor.

 

The original Brevona [1100 Breva w/ 2v heads] had dual plugs, & up to a certain engine s/n [iirc, the changeover was made below the 25000 production number?] had the same oil return locations as the V11 cases. The oil returns were changed on the later cases in preparation for the jump to the 1200 2v motor. This was per the Guzzi bible [which oddly enough, is not affiliated in any way w/ Piaggio or Guzzi, but compiled by our fine friends @ Moto Int'l. in Seattle...] So conceivably, the dual-plug heads off a sufficiently low s/n Brevona should drop right onto the V11 cylinders. Don't forget to get the twin-output coils to replace the single coils on your V11 while you're at it...

[docc]

The published compression ratio of the early V11 is 9.3:1. Were the later motors different?

[czakky]

I believe the 02 on (long frames) had a slight increase in compression, 9.8:1...?

[Zooter]

I believe the 02 on (long frames) had a slight increase in compression, 9.8:1...?

2002 models I looked up were all still 9.5:1

[czakky]

 

I believe the 02 on (long frames) had a slight increase in compression, 9.8:1...?

2002 models I looked up were all still 9.5:1

 

Sorry guess it was 03' on...

[sp838]

Scored some dual plugged heads from Germany

 

I have the correct ignition map thanks to motoguzznix, now I am trying to figure out which coils to use. The aftermarket coils I'm looking at are higher resistance than the stock MagMar BAE850AK coils we have stock, which are spec'ed at .5 - .6 ohm primary, 6 - 8 kohm secondary. Most of the Dyna coils for example are 3ohm primary. Silent-Hektik dual spark coils are 1.7 ohm. Is there any reason not use these coils with higher resistance? I put some dyna coils on my honda cb350 and it runs like a bat out of hell. It doesnt have a complicated and expensive ECU though, on the V11 I wouldn't want to fry any sensitive electronics... Any thoughts?

 

Thanks!

[sp838]

Well, the fine folks at TLM were of assistance. They said the coils from the Breva/Griso 1100 would work. Those are 1.5 ohm, so that leads me to believe that the SH coils would work too. Onward!

[gelos]

^{On the image of your own heads? I also currently working with my machinist to modify my heads. Can you present a detailed photo from the outside? We are looking for the right place, the space is verry small.}

^{I will use the dual coil from Breva too, resp.the same from Fiat 1000 ccm auto engine and map by motoguzzinix.}

 

^Thanks

[motoguzznix]

sp838 and gelos

 

When using the Breva/Fiat coils, don't go havoc with compression ratio.

I was pretty unsuccessful when tuning  a Breva 1100. We raised the compression to slightly above 11:1 and the engine pinged/knocked severely. To get it out from pinging, I had to reduce the ignition timing so much that all the gains from the CR were gone. All this because the coils were not able to burn the mixture correctly.

 

When the compression pressure gets too high (good VE, high CR), the spark is too weak with these coils. They are designed to fire 2 spark plugs of a 4-cylinder car engine. On such an engine, one cylinder is during overlap when the other is ready to fire! The spark during overlap doesn't need much energy so the other cylinder gets 90% of the energy available from the coils. In a twin plug Guzzi engine, both plugs in one cylinder are in need of the full energy which the coil can not deliver simply because it is not designed for that purpose.

 

When keeping the CR at 10:1 and the mixture not too weak it will work. But you cannot get the full benefits of twin sparks with these coils.

[sp838]

motoguzznix - the Silent Hektik coils sounding more like the way to go, they supposedly produce a 120mj spark, the MagMar coils are quite a bit lower (don't have the exact number but I was told it was around 55 mj.) Should I consider the dyna coils, or is 3 ohms resistance too much?

gelos - I will take some detailed pictures for you. The secondary spark plug hole goes through the oil input. The new oil input is moved over to the side.

[gelos]

Hi Ernst, your message about coils is bad surprise for me. My project is CR about 10,5 by redesign heads. Which coils do you recommend? What do you mean about japanese dual coils from Suzuki DL 650, primary 1-3 Ohm, secondary with caps 25-40 kOhm?

 

sp838-its kind of you, oil input goes into new place, but plug bore angle and position have not many option, it is my first attempt.

[gelos]

I tested today the Fiat dual plug coil on single spark V11. First cable goes into engine, second cable on simple test arrangement. The spark jump easy 20 mm distance. I think the coil must work solid into real engine running.

[docc]

Yikes! What a spark!!