Modern chain 8V vs old belt 8V differences?

[Mi_ka]

What are the differences between the two engines?
Ok, the new 8V is a pretty different architecture with the belt driven cams, the CARC assembly, the alternator set atop, the modern injection system, the capacity differences, the catalysts...

But how do the combustion chamber setups compare to each other?
How do the engine characters differ?
Sounding differently?
Was the old 8V more/less reliable?
More maintenance needed?
Does the old belt drive offer any advantage over the modern chain drive? (ok, when everything has been assembled properly at the factory.. :roll: )
Was the old injection fueling any good?

I see that the old belt 8V still exists in the MGS-01.
Does someboy know if it is the same? An major redesigns or just gone from 992 to 1225 cc and added a modern fueling system?
What may have been the reason for the belt engine's discontinuation for road use at the start of the decade?

Plain old curiosity...

 

[Penis Rotor]

Despite their seeming similarity the 'Old' Hi-Cam and the 'New' Hi-Cam are completely different motors sharing very few components that are even remotely similar.

First and most obvious thing is that the new motor is liquid cooled. The old belt drive motor remained primarily air cooled with only a single oil pump of dubious quality delivering oil primarily for lubrication and to cool the bearings. The new engine has dual pumps, one low volume, high pressure for the bearings and one low pressure, high volume, for the cooling side.

The old motor was also much, much more complicated and expensive to produce. It has some lovely touches to it like the vernierable cams that could of come straight off a 1940's race bike, and in fact that is what it resembles in a lot of ways. Problem is that this made it horribly expensive to produce.

The belt towers also has the problem of blocking air flow to the front of the heads and the design was kept in the factory for years while they worked out an alloy that wouldn't crack and fail when it got hot! Even so creacked heads are ot unknown on Daytonas, especially those with 'Hop-up' mods. Being liquid cooled the new motor doesn't seem to suffer rom any of these problems.

The new combustion chamber and head design is superior in many ways to the old one. The exhaust valve seats are cooled by oil galleries and the casting, even above the combustion chamber, is very thin and cooled effectively by torrents of oil that cascade out of the camboxes and their surrounds. It's one weakness is that unlike a truly 'Modern' cylinder head the ports are side-draught rather than downdraught and this encourages, along with the very narrow included valve angle, loss of incoming charge while the valves are on overlap. This is exacerbated if an unrestrictive pipe is used and is worsened if the harmonics of that pipe are wrong. While to a greater degree the older motors will respond well to 'Traditional' tuning methods the new 8V requires a bit more cautious approach to getting the best out of it.

The chain driven cams have consierably less overhang to the sprocket than the belt driven cams do to the cam-wheels meaning less stress and being 'Internal' to the motor have fewer leak points. The MGS-01 motor also, unlike the Daytona/Centauro units, disposes of the dummy shaft across the top of the crank to allow the increase in capacity in that motor. While outwardly similar in appearance the MGS-01 motor is also a very different beast in many respects to the 'Daytona'. Although obvously of a very similar desighn there are marked differences. While still listed as an option built to order the fact is all the 'Old' Hi Cams that are being used are being, (If they still are.) built up from NOS, nothing for them is manufactured any more for build.

Despite the fact that many see the Nuovo Hi-Cam as not a 'Real' Guzzi motor as it was primarily designed at Noale rather than Mandello it retains enough traditional 'Guzziness' to appeal to most Guzzista while at the same time having the punch to appeal to many who previously wouldn't consider the brand. The sad thing is that Piaggio seems determined not to put it in a 'Sporting' package which is what many people are crying out for. I'm a great fan of the new 8V. It is simple well made and robust. In comparison the 'Old' hi-cams were highly-strung, temperamental and fragile. That's why I never bought one. That and the fact they did nohing that much better than my old pushrod bikes! A fact confirmed by the factory when it kept the 1100cc motor for the V11 Sport series and consigned the 'Old' hi-cam to the dustbin of history.

As I said in the opening paragraph, the two engines are chalk and cheese, night and day. In terms of performance they are quite similar but the Nuovo hi-cam has a bit more to come whilst maintaining its reliability. the old engine was already stretched in tock trim to the limits of its performance envelope.

YOMV.

Pete

 

[Mi_ka]

Big big thanks Pete!
As all these have been very rare birds in Greece I have never heard of their quirks but always wanted to!

Never heard the term "vernierable cams" in english before - what are they exactly? Cam timing gear "slots" permitting timing adjustments? Googling "vernierable cams" I only came accross other posts by you giving even more info on the engine!

Any info about the sound/feel/behavior differences between the vecchio/nuovo 8Vs?
Was there any real benefit against the 1100 for real life roads?

 

[Penis Rotor]

The outer camwheels are 'Slotted' internally and these have a multi pointed 'inner wheel' that bolts to the end of the camshaft. By moving the inner wheels around in relation to the camwheel outers allows you to change the cam timing by very small increments.

Parts #'s 26 and 25 in this pic

Early Hi-Cams used the P8 controller which is a lot less sophisticated than the W5AM and it shows.

Pete