FBF Pistons before and after dyno charts

[FuelCooler]

Well, yes.

 

WARNING! THE FOLLOWING CIRCUMSTANCES MAY NOT APPLY!

 

I'M NOT SAYING THAT THIS IS NECESSARILY WHAT ALWAYS HAPPENS, FOR GOD'S SAKE!

 

NO SUCH IMPLICATIONS ARE EITHER MADE OR INFERRED!!

 

-- BUT ALL STATEMENTS ARE 100% TRUE!

 

I'll simply attempt to provide a little "counterpoint" here to all those who will tell you that high-comp pistons are the dog's danglies -- and there are LOTS of 'em out there -- possibly more'n a few who've actually done it and don't regret it!!

 

HOWEVER:

 

Many who install high-comp pistons seem to believe that they're some kind of free, magic "bolt on horsepower". While it's certainly true that with proper mapping and tuning (and fuel), you will certainly lift power and torque curves substantially, there are trade-off considerations that are all too often overlooked by the uninformed.

 

I have a friend who bought a 2000 Sport with high-comp pistons already installed off a dealer showroom floor, who went thru a horrendous year-long litany of gruesome problems trying to get the bike into a rideable state of tune. The problem as he saw it at first was to make the bike's tuning compatible with available fuel, so as to get it to run on California pump gas without pre-igniting, or detonating. It would ping horribly on pump gas -- to the point where he was afraid of holing the pistons. As long as he put high-octane "race gas" in it, it ran like a Champ.

 

Many's the time (every time I saw him, as a matter of fact) that he said he wished his bike ran like mine, so he could ride wherever he wanted, like I do.

 

After a year of not being able to ride it beyond a few round-trip tankfuls of his only source for "race gas" (without his wife driving behind with "race gas" in their van, an experience that as far as I know only happened once ), he had stopped riding it altogether in frustration and disgust, and eventually sold it off at a loss, after having expended much time and wasted effort with the very best Professional dyno tuning and re-mapping (including timing) expertise available. By that time he had come around to a different point of view on the cause of the problem -- high comp pistons WERE the problem (his conclusion -- NOT MINE!). In his newly "educated" view, he would have much preferred stock pistons to start with. By this time, he realized why the previous owner had traded the bike in long before it was broken in. But by then, he was so emotionally distraught over the whole ordeal (effort level and expenses), that he didn't want to install stock pistons -- he just wanted the thing out of his sight.

 

Keep in mind, please, that this is with 91 RON California Ethan-o-crap gasoline. Depending on wot you can get, of course, YMMV. THIS IS NOT wot I would have done, but he never had the heads off for a look to see what (if any) head work may have been done. Proper head work can do a great deal to improve squish characteristics and flow with high-comp pistons, which may (or may not) have helped.

 

In any case, many seem to ignore the fact that higher-comp pistons put more stress and strain on the entire engine and drive train. Now for those who tend to sell bikes off before they're broken in (as did BOTH the first and second owners of this particular bike ), of course this would not be important. . .

 

There's a reason mfgr's spec. stock compression ratio's. Unless you know wot y'er doing, you could be making a mistake.

 

And to each his own. . .

 

 

Ratchethack,

I know you wanted to avoid this kind of reply but...for the sake of science, hear me out

One of the problems I have is this: '----BUT ALL STATEMENTS ARE 100% TRUE'.

If you or your owner friend never had the heads / barrels off for a look I can't see why you (of all people) keep posting this (your friends) experience. How do you know someone (previously) didn't just mill a millimeter or so off the heads (the easy way) and claim it had high comp pistons? Did anyone check? Or maybe they did pistons and milling. Maybe the compression height was too high on the aftermarket pistons (manufacturing error), maybe there was a tolorance stacking issue with this particular motor?

I am sure the bike detonated badly on pump gas but ran 'like a champ' on race gas. I am sure it could not be 'mapped' out. These are things that you or you friend can and did verify. But without looking at and measuring actual parts to see what you have, you are making assumptions. Who knows that the pistons are the cause? They may be. I would feel much better about this post if it was you who did the modification and had the experience.

 

Cheers,

Steve

[WitchCityBallabio]

Wouldn't dual plugging the heads take care a lot of the problems experienced with pump gas with the high compression pistons?

 

I had a Porsche 911 that I had substantial amount of work done for the track. Compression (pistons) was increased substantially, but because I had the heads dual plugged and added a hotter electronic coil system, it ran fine on pump gas.

 

I'm assuming as it was also air cooled, that similar results could be had with the Guzzi engine no?

[Guest ratchethack]

Ratchethack,

I know you wanted to avoid this kind of reply but...for the sake of science, hear me out

One of the problems I have is this: '----BUT ALL STATEMENTS ARE 100% TRUE'.

If you or your owner friend never had the heads / barrels off for a look I can't see why you (of all people) keep posting this (your friends) experience. How do you know someone (previously) didn't just mill a millimeter or so off the heads (the easy way) and claim it had high comp pistons? Did anyone check? Or maybe they did pistons and milling. Maybe the compression height was too high on the aftermarket pistons (manufacturing error), maybe there was a tolorance stacking issue with this particular motor?

I am sure the bike detonated badly on pump gas but ran 'like a champ' on race gas. I am sure it could not be 'mapped' out. These are things that you or you friend can and did verify. But without looking at and measuring actual parts to see what you have, you are making assumptions. Who knows that the pistons are the cause? They may be. I would feel much better about this post if it was you who did the modification and had the experience.

 

Cheers,

Steve

Steve, I'm only making an observation as I clearly stated up front.

 

The dealer who sold the bike was the dealer who put the high-comp pistons in it, so it's not as if the owner didn't have pretty close access to all that was done. I simply do not have many of the details myself, because I wasn't made privvy to them. Take the experience for what it is, related to me by the owner directly, repeatedly, over a year. The guy learned a lot more than he ever wanted to know about compression ratios by the time he dumped the bike, he regretted the fact that the engine wasn't stock, and he was miserable the entire time he owned the bike, except for two days -- the day he bought it, and of course, the day he sold it.

 

I put this account out there because I think that at the very least, it should give pause to guys who might otherwise get themselves in over their heads, and it might stop someone from making a mistake. Now if they have fuel quality well in hand, have a solid understanding of what they're doing, and have access to a credible engine builder who also knows Guzzi's, well then I reckon they might well be covered. I figure they're apt to be tested, regardless.

 

I know my friend would've well appreciated hearing this kind of an account the day before he made the plunge.

 

It's a story that not too many who've done something like it are apt to tell, but I'll bet there's lots more of 'em out there than meets the eye. Why is this? Many (including my Pal) are none too keen on telling it -- simply because it doesn't reflect too well on his level of knowledge and understanding of engine dynamics -- and to some degree, on his willingness to use common sense.

 

Caveat emptor.

[FuelCooler]

Steve, I'm only making an observation as I clearly stated up front.

 

The dealer who sold the bike was the dealer who put the high-comp pistons in it, so it's not as if the owner didn't have pretty close access to all that was done. I simply do not have many of the details myself, because I wasn't made privvy to them. Take the experience for what it is, related to me by the owner directly, repeatedly, over a year. The guy learned a lot more than he ever wanted to know about compression ratios by the time he dumped the bike, he regretted the fact that the engine wasn't stock, and he was miserable the entire time he owned the bike, except for two days -- the day he bought it, and of course, the day he sold it.

 

I put this account out there because I think that at the very least, it should give pause to guys who might otherwise get themselves in over their heads, and it might stop someone from making a mistake. Now if they have fuel quality well in hand, have a solid understanding of what they're doing, and have access to a credible engine builder who also knows Guzzi's, well then I reckon they might well be covered. I reckon they're apt to be tested regardless.

 

I know my friend would've well appreciated this kind of an account the day before he made the plunge.

 

It's a story that I reckon not too many who've done something like it are apt to tell, but I reckon there's lots more of 'em out there than meets the eye. Why is this? Many (including my Pal) are none too keen on telling it -- simply because it doesn't reflect too well on his level of knowledge and understanding of engine dynamics -- and to some degree, on his willingness to use common sense.

 

Caveat emptor.

 

Well, I ain't too smart, but sometimes I might expecting too much of others (not you Ratch). Guilty.

 

At least this post will remind people not to throw out their stock pistons if they make the swap. I would gladly buy a set (or two, Brent) of used, undamaged FBF or Mike Rich pistons at a reasonable discount if folks are not happy with them. Folks, feel free to PM me if you are too embarrassed!!!!

 

Cheers,

Steve

[Dimitris]

Very interesting infos.....

 

I always "feed" her with Shell 100 Octane Racing Fuel (or BP or something equal). I still intend to call FBF in Italy and proceed to this upgrade (keeping also the stock pistons )

[Skeeve]

I would gladly buy a set (or two, Brent) of used, undamaged FBF or Mike Rich pistons at a reasonable discount if folks are not happy with them.

 

I don't think you'll be having too many takers on your offer for the Mike Rich pistons. From memory of the pictures of the stock pistons vs. FBF vs. Mike Rich units side by side, the FBF pistons look very much like the stockers, only more so, ie: profile section of the Matterhorn. The MR pistons in comparison looked like something out of Monument Valley: very flat & mesa-like.

 

The stockers & FBF pistons were the old way of raising compression, which worked great back in the days of widely available 98 (r+m)/2 octane pump gas. Crank up the c.r. by putting a high-dome piston inside the chamber, add more spark advance, fire it off 38-45deg BTDC, & wait for the flame front to travel all the way around to the far side of the worl^H^H^H^H, uh, chamber. Does this method still work since the demise of leaded gasoline back in the 80s? Eh, not so much. Go the airport and get a gallon can of 100LL to add to your fuel, kiss your catalytic convertors or oxygen sensors goodbye, and bid "Farewell to the Ping." [bTW, don't think I'm recommending this as a real solution. It'll work, but it's not exactly 'practical.']

 

The Mike Rich pistons seem to function by making the most of the available squish, leading to a much more compact combustion space. Frankly, they're what Guzzi should have delivered from the outset. I suppose if Ratchet doesn't want any higher c.r., he'd still be well off getting the MR pistons & machining a couple thou' off the top: he'd still have stock compression, but be able to run on regular. Maybe that's what I'll do when I get some $$$ again... [sigh]

 

[dlaing]

[motoguzznix]

Some comments on the pictures above:

 

The Mike Ritch piston is the only piston designed to cope with the V11 combustion chamber shape - it follows the chamfer in the stock chamber thus allowing a real squish area and a CR quoted 10.5:1. Very good.

 

The FBF piston is flat on top outside and does not cope with the chamfer of the combustion chambers - so you get 11:1 CR without a real squish area.

To remove the chamfer you have to mill approx. 1 mm off the head. This will further increase the CR supposedly to around 12:1, which is maybe too much even for a twin plug installation to cope with. No good.

 

The stock piston is the same design like the FBF and even in stock configuration a lot of V11s tend to ping, resulting from the design without squish-area. My KR had a measured CR of 9.15 from new and pinged sometimes!

When optimising the squish area by milling 1 mm off the heads and shortening the cylinder barrels by 0,45 mm to deck the pistons with the cylinders, the CR will climb to approx 10.5. Very good, will work fine on single plug with mapping to suit.

 

Same result as with the Mike Rich piston, but the combustion chamber shape is slightly better due to the lower piston crown. But the Mike Ritch piston will probably work without any machining of head and cylinder barrels. But the stock piston is a good, stout item, maybe a little heavy but adequate for the job in a street engine. For a race engine, the weight will get more important.

 

The conclusion for me: the least desirable design is the FBF piston - you would be better by modifying the heads and barrels and retaining the stock pistons.

[FuelCooler]

If I go this route, (if no one sells me a used set! ) it would most likely be Mike Rich, but I would want to talk to him first. I used to make pistons. Anyone know who his initial supplier is?

[dlaing]

If I go this route, (if no one sells me a used set! ) it would most likely be Mike Rich, but I would want to talk to him first. I used to make pistons. Anyone know who his initial supplier is?

I vaguely recall speculation that they are Wiseco.

[Guzzirider]

The FBFs are made by Wiseco as well.

[dlaing]

The FBFs are made by Wiseco as well.

Now that you refreshed my memory, it was the FBF's I was thinking of that were from Wiseco, not the the Mike Richs'.

But they could both be. Wiseco appears to be the leader in aftermarket pistons