Spaceclam
Cruisin' Guzzisti
OK, so im going to start this off by saying it's long. I know. Before i did all this, i spend a LOT of time searching for information regarding milling griso/breva/v11 heads (same head design i think) and i found lots of little suggestions, but very few RESULTS. So what i am writing here right now is what i would have HOPED to find somewhere on the internet.
Background:
My engine pings, it always has. Valves have been set (came at 4 and 6, set to 6 and 8 ), TPS set (was way off), TBs set (also way off), i have fixed holes in my exhaust upstream from my o2 sensor, (defect) i have removed the emissions equipment, stepper motor, i have Todd's PCV/AT/ECU combo, (which helped the most) but NOTHING would get rid of it. Using the dynojet software, i put marks on my throttle grip for 40, 60, and 80% throttle (since the throttle cam isn't linear). I determined that it pings between 4k and 5k, at 60% throttle or above in 6th gear, and sometimes in 5th. Todd's stuff dropped my engine temps drastically, (it was running near 300*F at the heads prior) but it still did it, so i figured it must be something other than excessive heat.
I had heard that squish geomoetry/clearance had a lot to do with the v11s pinging, (although apparenty the rod/stroke ratio is different, so i couldn't drop the FBF or MR pistons in) so the only way to adjust things is to go in and start cutting metal. I figured why not, i'm good at throwing myself into the fire.
Initial observations
Well, first and foremost, i had a stripped engine stud bolt (the head was stripped from the factory) so i spend the better part of the morning drilling the head off. Once finally removed, I was able to get the head off without any further problems. What i found was interesting. the bike only has 7.5k miles on it, but there was a THICK "about .01" coating of carbon on the pistons, the left more so than the right. Some of it was oil, which suprised me, since the bike doesnt use any, but a lot of it was hard carbon, indicating that i am either running far too rich, or temps are a little too low, and thus carbon forms. I cleaned off as much as i could, and i'm going to let my hotter temps/some techron do the rest.
So at TDC, the deck height of my piston was .065, which isn't TOO bad except that there is a .030" deep chamfer on the heads as well, which is about .15" wide. This area on the pistons is flat, not angled, which means that not only do i have no effective squish, but the factory's "squish" areas didn't match at all, ant has a clearance of .095 on the inside of the band. This was not including the .01" thick carbon layer the solder strips were set on either, so the actual number should have been .105 They have been making this same basic engine since the 70's, you'd think they would figure something like that out. However, both cylinders had identical deck height. Gasp!
Stuff I did
Basically, in order to achieve any squish at all, i had to A) remove my base gasket and B ) mill .030 off my heads, to remove the chamfer (match piston geometry to the head). This gave me a .15" wide squish band all the way around the perimeter of the piston, with a .05 clearance, after removing some carbon. I could not comfortably go any further because my valves would get a little close for comfort (the valves were at .045 clearance) and i was at the end of my tapped adjustment range anyway. Yes, i could have fixed that, but i didnt want to.
So assuming the guzzi spec'd compression of 9.8:1 is accurate, i calculated that my new compression was 10.7:1. High enough that i was concerned about my geometry improvements being offset by the additional compression. But at this point, all i could do was shim stuff back up to lower my compression, so i figured i would just try it and see what happened.
The first ride
Before going out, i accepted the trims on my Autotune (which resets all the fields to 0), so that i Could see the changes before/after the ride. IT is normal for this bike (i have kept an eye on things) to have trims averaging about 5% from one day to the next, sometimes more, sometimes less.
It pinged. Not so much at first, but harder towards the end of the ride. I figured it was because i was TRYING to make things ping, so my chamber was real hot.
After the ride, What i found confirmed my initial suspicions about the AT. Even though it's a good piece of equipment, and the sensor may be very accurate to the gas it "sees", there are too many variables in combustion for it to accurately read inside the cylinder. I know this, because I found trims which averaged -15%, + or - in the area where it pings. That means it took fuel out of that area, bringing my fuel levels to LEANER than stock, even though the target AFR never changed, and is set to 13.2.
I called it a night. it was 12AM, and about 43 degrees, according to my dash.
Second ride
Before i left, i cleared the initial trims, set my target AFR to 13.0 in the affected areas, and added 10% more fuel over stock in that range, just to get it started. At first, i was quite pleased. It had a lot more low end power, 1st gear is officially obsolete, it cold started better, and the pinging wasn't much of an issue. Of course, it's been raining like crazy around here so the canyons are pretty nixxed. Instead, i took a brisk 51 degree ride down mullholland, and back up the 101, using my "tuning marks" on my throttle to pull the bike from 4k and let the AT do it's thing. After a few pulls, it started pinging again. I was afraid that, after warming things up, i had actually made things worse. That is quite a sinking feeling, especially knowing how expensive this shit is.
I pulled into my house, hooked up the laptop and reviewed the fuel numbers again. the AT had taken fuel out again, such that it was pretty even with stock in the areas again, even though the AFR was set to 13:1. Since this had happened twice now, i am pretty sure the pinging thing is, at least now, mostly fuel related. And for some reason, the AT gets funny readings in that throttle/rpm range.
So it seems that i have to tell the AT to run much richer in those areas than it actually is, in order to get the results i want. But that's ok. I added more fuel manually again and set my AFR to 12.8, and I will keep my eye on the fuel graph for a while. Just for reference, stock is rather lean.
Final impressions
The pinging is a wash. After i made the corrections the first time, before the AT started changing things, pinging is EXACTLY as it was before. This either means that it isn't combustion/excessive heat related, or that my changes in geometry/squish were compensated for by the extra compression.
However, if you are a machinist/know a good machinist who does stuff for not a lot of $, i would reccomend doing what i did. It's about a day's worth of work, and if you have a shop, then it costs you nothing. Considering the only money i spent was on a new oil ring (cause i cracked mine like an idiot) i would say it was a good mod, well worth the money. I wouldn't pay somebody hundreds of dollars to do this though.
Performance wise, it's just snappier. It revs faster, it pulls harder on the bottom end. First gear is totally un necessary. I like it.
G'day, yall.
-Clam
Background:
My engine pings, it always has. Valves have been set (came at 4 and 6, set to 6 and 8 ), TPS set (was way off), TBs set (also way off), i have fixed holes in my exhaust upstream from my o2 sensor, (defect) i have removed the emissions equipment, stepper motor, i have Todd's PCV/AT/ECU combo, (which helped the most) but NOTHING would get rid of it. Using the dynojet software, i put marks on my throttle grip for 40, 60, and 80% throttle (since the throttle cam isn't linear). I determined that it pings between 4k and 5k, at 60% throttle or above in 6th gear, and sometimes in 5th. Todd's stuff dropped my engine temps drastically, (it was running near 300*F at the heads prior) but it still did it, so i figured it must be something other than excessive heat.
I had heard that squish geomoetry/clearance had a lot to do with the v11s pinging, (although apparenty the rod/stroke ratio is different, so i couldn't drop the FBF or MR pistons in) so the only way to adjust things is to go in and start cutting metal. I figured why not, i'm good at throwing myself into the fire.
Initial observations
Well, first and foremost, i had a stripped engine stud bolt (the head was stripped from the factory) so i spend the better part of the morning drilling the head off. Once finally removed, I was able to get the head off without any further problems. What i found was interesting. the bike only has 7.5k miles on it, but there was a THICK "about .01" coating of carbon on the pistons, the left more so than the right. Some of it was oil, which suprised me, since the bike doesnt use any, but a lot of it was hard carbon, indicating that i am either running far too rich, or temps are a little too low, and thus carbon forms. I cleaned off as much as i could, and i'm going to let my hotter temps/some techron do the rest.
So at TDC, the deck height of my piston was .065, which isn't TOO bad except that there is a .030" deep chamfer on the heads as well, which is about .15" wide. This area on the pistons is flat, not angled, which means that not only do i have no effective squish, but the factory's "squish" areas didn't match at all, ant has a clearance of .095 on the inside of the band. This was not including the .01" thick carbon layer the solder strips were set on either, so the actual number should have been .105 They have been making this same basic engine since the 70's, you'd think they would figure something like that out. However, both cylinders had identical deck height. Gasp!
Stuff I did
Basically, in order to achieve any squish at all, i had to A) remove my base gasket and B ) mill .030 off my heads, to remove the chamfer (match piston geometry to the head). This gave me a .15" wide squish band all the way around the perimeter of the piston, with a .05 clearance, after removing some carbon. I could not comfortably go any further because my valves would get a little close for comfort (the valves were at .045 clearance) and i was at the end of my tapped adjustment range anyway. Yes, i could have fixed that, but i didnt want to.
So assuming the guzzi spec'd compression of 9.8:1 is accurate, i calculated that my new compression was 10.7:1. High enough that i was concerned about my geometry improvements being offset by the additional compression. But at this point, all i could do was shim stuff back up to lower my compression, so i figured i would just try it and see what happened.
The first ride
Before going out, i accepted the trims on my Autotune (which resets all the fields to 0), so that i Could see the changes before/after the ride. IT is normal for this bike (i have kept an eye on things) to have trims averaging about 5% from one day to the next, sometimes more, sometimes less.
It pinged. Not so much at first, but harder towards the end of the ride. I figured it was because i was TRYING to make things ping, so my chamber was real hot.
After the ride, What i found confirmed my initial suspicions about the AT. Even though it's a good piece of equipment, and the sensor may be very accurate to the gas it "sees", there are too many variables in combustion for it to accurately read inside the cylinder. I know this, because I found trims which averaged -15%, + or - in the area where it pings. That means it took fuel out of that area, bringing my fuel levels to LEANER than stock, even though the target AFR never changed, and is set to 13.2.
I called it a night. it was 12AM, and about 43 degrees, according to my dash.
Second ride
Before i left, i cleared the initial trims, set my target AFR to 13.0 in the affected areas, and added 10% more fuel over stock in that range, just to get it started. At first, i was quite pleased. It had a lot more low end power, 1st gear is officially obsolete, it cold started better, and the pinging wasn't much of an issue. Of course, it's been raining like crazy around here so the canyons are pretty nixxed. Instead, i took a brisk 51 degree ride down mullholland, and back up the 101, using my "tuning marks" on my throttle to pull the bike from 4k and let the AT do it's thing. After a few pulls, it started pinging again. I was afraid that, after warming things up, i had actually made things worse. That is quite a sinking feeling, especially knowing how expensive this shit is.
I pulled into my house, hooked up the laptop and reviewed the fuel numbers again. the AT had taken fuel out again, such that it was pretty even with stock in the areas again, even though the AFR was set to 13:1. Since this had happened twice now, i am pretty sure the pinging thing is, at least now, mostly fuel related. And for some reason, the AT gets funny readings in that throttle/rpm range.
So it seems that i have to tell the AT to run much richer in those areas than it actually is, in order to get the results i want. But that's ok. I added more fuel manually again and set my AFR to 12.8, and I will keep my eye on the fuel graph for a while. Just for reference, stock is rather lean.
Final impressions
The pinging is a wash. After i made the corrections the first time, before the AT started changing things, pinging is EXACTLY as it was before. This either means that it isn't combustion/excessive heat related, or that my changes in geometry/squish were compensated for by the extra compression.
However, if you are a machinist/know a good machinist who does stuff for not a lot of $, i would reccomend doing what i did. It's about a day's worth of work, and if you have a shop, then it costs you nothing. Considering the only money i spent was on a new oil ring (cause i cracked mine like an idiot) i would say it was a good mod, well worth the money. I wouldn't pay somebody hundreds of dollars to do this though.
Performance wise, it's just snappier. It revs faster, it pulls harder on the bottom end. First gear is totally un necessary. I like it.
G'day, yall.
-Clam
