High Compression Pistons

[Richard]

Has anyone fitted FBF high compression pistons to their V11? I am looking at doing this and would be interested to hear any thoughts on the topic, please?

 

Richard

V11 Rosso Corsa

[Guest ratchethack]

Hooooboy, here we go. Richard, I assure you that my take is entirely objective and honest. I have no dog in this fight. Take that for what it's worth. There's been heated debate on this, which you will find with a search.

 

Many have evidently very different and entirely satisfactory results with the FBF hi-comp pistons. I can't speak for them. They have posted their opinions here extensively.

 

Many will no doubt jump on this thread with heated opposition to my post. Such is life.

 

I have a friend with FBF high-compression pistons in a 2000 Sport - it's the same Guzzi as mine. He bought it used with the FBF's installed. Without "race gas" it knocks like the bloody clappers. With race gas it runs like a Champ, and pulls magnificently from the bottom right up through the power band. It pulls significantly harder than my stock-piston-equipped bike. Mine runs like a Champ on high octane pump gas. For over a year now, my Pal would've given almost anything, including that enhanced powerband (and more) to have a Guzzi that runs as well as mine does on pump gas.

 

The bike also has a PC III with a custom map installed. The very best minds on the planet at Dynojet have labored extensively over re-re-re-re-re-re-mapping the PC III with entirely unsatisfactory results - again, trying to make it run acceptably well on pump gas.

 

Now, after almost two years of trying to live with the downsides of having to run on "race gas", my Pal is so discouraged and emotionally (and financially!) drained over what for him eventually became a gruesome ordeal, that he's selling his Guzzi rather than taking on the relatively simple and relatively low-cost task of replacing the high-comp pistons with stock pistons, which he has been advised to do by numerous top-caliber professionals who have worked so hard and so long on tuning it.

 

At this point, he doesn't want to hear another word about what "could happen" or "should happen" and no, they haven't found a way to retard the timing without taking on trade-offs that he isn't willing to consider at this point.

 

IMHO, my Pal found out the hard way why the previous owner sold off his Guzzi before it was even broken in, taking a tremendous financial shellacking on all the high-dollar go-faster gear he sunk into it. Now my Pal's in exactly the same boat nearly 2 years down the road.

 

It's been a very sad thing to witness. Fortunately enough for my Pal, he's been riding a very nice 900S the whole time he's had his Guzzi, or he'd have blown a head gasket - and I don't mean on his bike. . . . . .

 

BAA, TJM & YMMV

[dlaing]

Now, after almost two years of trying to live with the downsides of having to run on "race gas", my Pal is so discouraged and emotionally (and financially!) drained over what for him eventually became a gruesome ordeal, that he's selling his Guzzi

SNIP

How cheap?

I can probably give $4000, maybe more if I know the details.

With Piaggo Guzzi parts prices, it may be time to buy used Guzzis for parts...

[Guest ratchethack]

How cheap?

I can probably give $4000, maybe more if I know the details.

We're not talking about a beater. It's in pristine condition and (again) still not yet broken in. He could part it out and do far better than this with all the bling & go-faster crap on it. I wouldn't even ask him if he's interested at that price. I reckon if he gets interested enough beyond talking about selling (a month so far), he'll run an ad, which ain't happened yet.

[pete roper]

I'm afraid I too will probably end up being shouted down here but I'll repeat my usual caveats again.

 

The V11 motor is still essentially identical in architecture to the V7 of 1967. It's been bored and stroked and it's in a considerably higher state of tune but it's still an air cooled, twin cylinder motor with two valves per cylinder operated by a fairly heavy valve-train. The cam that is in it is very similar to what used to be seen as the choice *sporting* road cam fifteen to twenty years ago. Choice because it gave improved power without sacrificing reliability too much. The fact is that the V11 is already in a fairly high state of tune and if you do tune it for more power, which is of course entirely possible, you HAVE to accept some trade off in longevity and reliability, I'm sorry but that is simply the laws of physics.

 

While increasing the CR will theoretically give you *Free Horsepower* it will also undoubtably, increase your risk of detonation and will also almost certainly require changes to the mapping of the ECU if it is to work properly along with a higher octane fuel to combat the detonation risk. As Ratchet's mate has found out there is no such thing as a free lunch. In fact most lunches at this table will end up very expensive in the long run.

 

I'm not trying to discourage anybody from tuning the buggery out of their machines. If that's what they want to do? Go for it! But I do like them to gointo it with their eyes wide open and realizing that the cost will be high and the results probably less than spectacular when compared with simply buying a 3 year old CBR600, sticking some Race Glass on it and going to three or four track days a year!

 

AS far as areas to spend money and improve things? People are probably sick and tired of me banging on with the same old drum. Forget the motor, get the suspension right first. The standard brakes are pretty good but if you want to you can fling some dollars at different rotors if you want to look like Flash Harry. As far as *performance* improvements go I'd say improve the breathing by de-restricting the intake and exhaust systems and then either but a My15M or get a PCIII and some custom mapping done. My prefference would be a My15M but that's because I'm old fashioned and don't like the idea of having a 'Box stacked on a box' even though I'm happy to admit that the PCIII seems to work perfectly satisfactorily in most situations. I've also ridden a couple of bikes equipped with Cliff's ECU and they really are quite outstanding in how they deliver the goods. *Mechanical* hop-ups will be expensive, quite often disappointing and will invariably reduce service life. If you're willing to accept those sacrifices? Go for your life! and you will be encouraged and aplauded, just don't expect it to be cheap and easy.

 

Pete

[Greg Field]

RH:

 

Bike is in SoCal, right? Have him take it to Ed Milich, and pay Ed to set the squish right on both cylinders. I'm betting that'll bring the pinging down to manageable levels. Or, if he wants to bring it to Seattle, I'll do it.

[Guest ratchethack]

Greg, my Pal's been taking it to Todd Eagan, co-GuzziTech Guru Host with Ed. My Pal's pretty tight with Todd. Todd may have more hours on my Pal's map than on his own V11 Sport-engined Jackal. If there were a way to set the squish to solve this, I reckon Todd would've had it done by now (for all I know he's already tried it). But it was a good thought. The chief problem now has become a level of mounting frustration that's moved on into the disgust zone. It seems to transcend the will to do anything now but get rid of it.

 

Like I said, it's a sad sad story.........

[Greg Field]

If someone hasn't, they need to go inside the engine and see what's wrong. Measure the squish, and set it very tight and the same on both sides. I may be wrong, but I'm guessing Todd did all his work with digits and maps. This is a job for a machinist.

[Guest ratchethack]

As I recall, Ed likes at least about .040 squish. Do you agree?

[Wick]

Pete,

Please define "Flash Harry". And, how is it going with the set-up of the oil windage plates.

 

Wick

[pete roper]

Soory, I forget that these boards are international.

 

'Flash Harry' was a character in a couple of movies from the late '50's early '60's made by the Ealing studios in England. Ealing produced a vast array of superb acting tallent and some very, very high quality films but it is probably most famous for it's post-war productions of 'Light Entertainment' which are collectively known as the 'Ealing Commedies'. Despite their seemingly lightweight nature they were in fact burning satires on the 'State of the British Nation' during a period of austerity and empirical decline and remain, if viewed in this light, hillaroius. Especillaly for those of us who grew up during this period.

 

'Flash Harry' was the archytypal 'London Spiv' from those post war years. A bloke on the fringes of criminallity, fencing a bit of stolen gear here, running a betting shop on the sly there, brokering crooked deals but never really getting involved. You get the picture? The most important thing about 'Flash Harry' was that he was/is all 'Mouth and Trousers'. He can talk the talk and walk the walk but behind it there is nothing but bullshit! Just like the rest of us really!

 

If you *can* find a decent film hire store that carries such obscuranti as Ealing Commedies can I suggest

 

Passport to Pimlico

 

The Man in the White Suit

 

The Tichfield Thunderbolt

 

and either of the St. Trinians films.

 

If you want to go all esoteric on me? F@ck off

 

Pete

 

Tried to edit an failed. Just as an addendum, George Cole played 'Flash Harry. He later went on to play Arthur Daley in the wonderful TV series 'Minder' which was a time capsule for what it was like living in London during my youth

 

Pete

[guido]

Ratchet. Your friend should install a couple of thicker gaskets, and lower the compression that way. It is really that simple. Fiddling with the mapping is not going to achieve much. You can only richen the mixture so much and fiddle the timing to a certain degree. If he hasen't installed a second sparkplug, you simply have a long spark travel, high temperature and pressure, and the the mixture will self ignite somewhere far from the spark plug.

It is really limited by the quality of fuel available, and if he doesn't want to run on race gas, lowering the compression with a set of thicker gaskets is the simplest and cheapest method.

[pete roper]

Ratchet. Your friend should install a couple of thicker gaskets, and lower the compression that way. It is really that simple. Fiddling with the mapping is not going to achieve much. You can only richen the mixture so much and fiddle the timing to a certain degree. If he hasen't installed a second sparkplug, you simply have a long spark travel, high temperature and pressure, and the the mixture will self ignite somewhere far from the spark plug.

It is really limited by the quality of fuel available, and if he doesn't want to run on race gas, lowering the compression with a set of thicker gaskets is the simplest and cheapest method.

 

Errr? guido, with all due respect what could possibly be the point of fitting higher compression pistons and then fitting thicker gaskets? The detonation is *mainly* due to the CR being too high now. It CAN be treated by getting the squish height correct but only to a certain degree. if, for some reason, this motor won't take the mods then nothing is going to improve it apart from major head work. Fitting thicker gaskets is simply going to f@ck up the squish and lower the CR. So why bother with the very expensive piston kit in the first place?????

 

Pete

[luhbo]

... So why bother with the very expensive piston kit in the first place?????

 

Pete

 

Because he (the Pal) already has them.

 

What Guido says is exactly the same what I have experienced 20 years ago. A friend of mine decided to enlarge his LM1 engine with plaine simple 1000 SP pistons, although special aftermarket LM1000 pistons with high (highest) domes already were available.

He also built in another camshaft, the inlet valves of a SR500 and mounted 40er Dell'Ortos. The result was the most pleasant Guzzi engine I've ever seen. Never pinging, as powerfull as the 3C-Laverdas and the Ducs, consuming around 5l/100km and less, and all that with standard LM3 cans. Really silk smooth.

 

I believe that was mostly the result of the very compact combustion chamber formed by the LM heads in combination with the cut-down looking piston domes. Besides the very positive and short flame paths such a combustion chamber also gives the advantage of a definitely smaller surface, so the piston stays cooler, the gas stays hotter and the explosion forces are working more centralised over the piston bottom. I think what I call advantages could be seen as disadvantages for any high compression pistons sold for Guzzis.

 

A very nice example of a high CR system can be found on Buell engines. Reshape the Guzzi heads to something like that and it might work better.

 

Hubert

[big J]

Wouldn't twin plugs sort this?