How to stop engine pinging

[Greg Field]

Two terms are useful when talking squish.

 

1) Squish area is the flat area around the perimeter of the combustion chamber that faces the flat area below it around the perimeter of the piston.

 

2) Squish clearance is the vertical clearance between the flat squish areas on the piston and combustion chamber.

 

In general, more squish area is better than less area, and less squish clearance is better than more squish clearance, provided that there's enough clearance that the piston doesn't smack the head.

 

On a hemi-head like on a V11, increasing squish area requires milling the heads.

 

Decreasing the squish clearance, which is often 2-3mm on a production Guzzi is more easily accomplished. The "right" way is to mill the base-gasket surface. It is "right" because then the cylinder swept area remains unaltered. The easier way is to experiment with the various-thickness base gaskets (at elast three different thicknesses are available, from the thin V700 base gaskets to the stock V11 base gaskets) available to get tighter squish clearance. On my Eldo, to get the clearance down to what I wanted required running it without base gaskets at all. Note, though, that using thinner base gaskets means at TDC the rings will now contact higher up on the cylinder. If there is appreciable wear to the cylinder, this could make a difference. On my Eldo, there was no measurable wear, so I felt OK doing this.

[dlaing]

When I got my Quat-D muffler my bike it aggravated the pinging at about 5000 rpm.

I custom mapped it with a PCIII serial on a tuning link dyno and the pinging got worse, because they leaned it in that area. Adding about 25 points to the PCIII map cured the problem, but I always thought that was too rich and retarding timing would have been the better solution.

I eventually traded the Quat-D for a pair of Mistrals.

The bike was still prone to pinging, but then I got Tuneboy and was able to easily eliminated the pinging through a mild change in timing.

IMHO timing is a better way to reduce it than fueling, especially if you are needing significantly more fuel than what people with same mods are mapping to.

Maybe squish is a better solution still.

We had a discussion on the forum where it seemed quite clear that the Mike Rich Piston provided a better squish effect than the FBF or OEM pistons. But in my opinion optimizing timing is a good idea....I am just not sure how to do it, yet...

[Skeeve]

IMHO timing is a better way to reduce it than fueling, especially if you are needing significantly more fuel than what people with same mods are mapping to.

Maybe squish is a better solution still.

We had a discussion on the forum where it seemed quite clear that the Mike Rich Piston provided a better squish effect than the FBF or OEM pistons. But in my opinion optimizing timing is a good idea....I am just not sure how to do it, yet...

 

Squish is better because it produces a more efficient burn, vs. timing which may sacrifice potential maximum power to a poor combustion chamber profile. But you use the tools that you have to do what you can.

 

As far as adjusting timing, would you break down & get a copy of Phil Irving's _Tuning for Speed_ already? Yeah, I know it's OOP: go to the library, & ask for it via interlibrary loan! So what if it costs you $10 to get them to ship it to you, & another $20 to copy it in its entirety? It's worth it! [Note: I'm not advising you to violate copyright. Extreme measures are called for when a publisher is stupid enough to let something this useful & popular go out of print. If it was still in print, I'd be telling you to find it on Amazon or bn.com. I wouldn't be surprised if making this book unavailable was part of some EPA/CARB/EuroSmog conspiracy! ]

 

To paraphrase: "it's best to find a long stretch of road, preferably with a slight uphill slant. You will want to be accelerating through the range where the motor pings, retard the timing until the motor stops pinging. At that point, you will want to try to hold the throttle steady, and adjust the timing to produce the greatest speed [or rpm]; this will be your optimum timing for that throttle setting. Repeat throughout the range. Obviously it is best to have a distributor with some means of adjusting the advance or retard on the fly, which is why this sort of tuning is usually performed by the factory during a model's development..."

 

I get the feeling Phil Irving would have killed to have some of the tuning abilities that we do today, what with EFI and incremental adjustment by laptop! Heck, I'd like to have that, at an affordable price! Right now, the products are on the far side of the Laffer curve: if the industry would wake up to the fact that they should all have a standard interface like the OBDII standard forced car makers to uphold, then DynoJet, TR, TuneBoy, et al would be able to make & sell their products in volume for $100/ea & make MUCH bigger profits than they do now selling their bits oney-twosey for discouraging prices... <_>

[Ryland3210]

We had a discussion on the forum where it seemed quite clear that the Mike Rich Piston provided a better squish effect than the FBF or OEM pistons. But in my opinion optimizing timing is a good idea....I am just not sure how to do it, yet...

 

I must say,in comparing the FBF pistons, it appears to me that the shortened skirts and lack of weight reduction on the sides around the wristpin are examples of cost reduction having too high a priority.

[dlaing]

Squish is better because it produces a more efficient burn, vs. timing which may sacrifice potential maximum power to a poor combustion chamber profile. But you use the tools that you have to do what you can.

 

As far as adjusting timing, would you break down & get a copy of Phil Irving's _Tuning for Speed_ already? Yeah, I know it's OOP: go to the library, & ask for it via interlibrary loan! So what if it costs you $10 to get them to ship it to you, & another $20 to copy it in its entirety? It's worth it! [Note: I'm not advising you to violate copyright. Extreme measures are called for when a publisher is stupid enough to let something this useful & popular go out of print. If it was still in print, I'd be telling you to find it on Amazon or bn.com. I wouldn't be surprised if making this book unavailable was part of some EPA/CARB/EuroSmog conspiracy! ]

 

To paraphrase: "it's best to find a long stretch of road, preferably with a slight uphill slant. You will want to be accelerating through the range where the motor pings, retard the timing until the motor stops pinging. At that point, you will want to try to hold the throttle steady, and adjust the timing to produce the greatest speed [or rpm]; this will be your optimum timing for that throttle setting. Repeat throughout the range. Obviously it is best to have a distributor with some means of adjusting the advance or retard on the fly, which is why this sort of tuning is usually performed by the factory during a model's development..."

 

I get the feeling Phil Irving would have killed to have some of the tuning abilities that we do today, what with EFI and incremental adjustment by laptop! Heck, I'd like to have that, at an affordable price! Right now, the products are on the far side of the Laffer curve: if the industry would wake up to the fact that they should all have a standard interface like the ODBII standard forced car makers to uphold, then DynoJet, TR, TuneBoy, et al would be able to make & sell their products in volume for $100/ea & make MUCH bigger profits than they do now selling their bits oney-twosey for discouraging prices... <_>

Thanks!...again.

The way I have been doing it so far is to use low octane fuel, find a hill and run it up to find the ping points. I have only done this once, because I figured it can't be good for the engine. Once I get a working WBO2 sensor <_ i get the fueling correct first and then move to timing while watching resulting a ratio.>

I figure if I can get very light pinking everywhere under accelerating load on 87 octane at about a 13.5/1 A/F, I can then enrichen to about 13.0/1 and run 91 octane. I am not sure at all of these A/F numbers. I am just throwing them out as a rough possibility.

Reading the book will surely help. Reading this forum sure has.

[RonV11]

I'm going to jump in here even though this isn't a direct MG experience. However, I had the exact same problem with my Superhawk (1000cc, VTwin). In my case it was the TPS. It was out of adjustment and was signaling the ECU to advance the timing before it should. Once adjusted to spec. all was fine. As I hadn't seen this mentioned, I thought I'd share. Now if the MG doesn't use the TPS in the same manner, just ignore the above comment.

[Dan M]

I'm going to jump in here even though this isn't a direct MG experience. However, I had the exact same problem with my Superhawk (1000cc, VTwin). In my case it was the TPS. It was out of adjustment and was signaling the ECU to advance the timing before it should. Once adjusted to spec. all was fine. As I hadn't seen this mentioned, I thought I'd share. Now if the MG doesn't use the TPS in the same manner, just ignore the above comment.

 

 

Excellent point Ron. I believe TPS will indeed have an effect on timing curve.

[Pierre]

It's amazing how many threads are going right now dealing with the same issues. Pistons, cams, head milling, timing. They all inter-relate so I guess it's not surprising.

 

1. I think the MR pistons may help reduce ping by extending the squish band up into the chamber a little further. Those who have examined the stock, the FBF and the MR pistons have opined that Mike's have a flatter top but carry the squish band up into the dome a little. Still, I wouldn't start with pistons to address ping;

 

2. Squish IS a significant compnent of getting a proper burn, and reducing tendency to ping. Optimum squish (according to the literature) is .030" and the thickness of a crushed V-11 (torqued) head gasket is .032" I believe ... so if you mill the heads until the piston kisses the head w/o a head gasket (should be tested by hand cranking, of course ) you get pretty close to perfect. For some reason I recall reading that milling the head as opposed to the barrels yields better results - but not sure on that. Mike Rich of course knows and I'm sure would be happy to tell you all about it.

 

When I'm trying to figure out what actually works in the real world I generally go to the literature available for Harley twins. More hop up work on air cololed twins has been done there than anywhere else - and it's been refined over decades. OTOH, Harley addressed a lot of issues issues by going to a different shape (bathtub) for the combusion chamber, so it's not an automatic crossover anymore in terms of what works. The second best place is to read what V-8 push rod race motor builders are doing. An old fashioned Dodge Hemi race moter holds a lot of secrets to how to make power, but of course water cooliing, better gas and the move to shallower combusion chmbers has rendered much of that obsolete ... except of cours on our Guzzis - a design firmly planted in that same era.

 

Here's a squish calculator: http://www.rbracing-rsr.com/squishcalc1.html

 

And here's an article discussing squish: http://www.nrhsperformance.com/tech_squish.shtml

 

The reason a big bore kit can be so effective IMHO is that it does 3 things - more displacement, higher CR, and extends the squish laterally the width of the increased bore. Mike's pistons extend squish in the other direction - pushing it up into the dome, or so those who have studied them tell me. Never asked him directly. Doing it that way (if in fact that's what he's done) also changes the angle of the squish - but if I was over my head before, that concept takes me into wilderness I'm not sure I can see my way through. Again, I'm sure Mike could tell you all about it. Hell of a resource and very generous with his advice.

 

Fun stuff. Sounds like a proper winter project for a denizen of the northeast facing 2 more mothhs of winter.

[pete roper]

Pierre, Im not familiar enough with V11 heads to know. Is there a chamfer on the edge of the combustion chamber in the head? If so that would explain Mike's sloped squish band and would certainly be a major consideratory factor in which would be the *best* pistons for combustion chamber shape and squish. If there is a chamfer then I can see nice benefits from Mike's shape, as I said, he's far more experienced in such things than me.

 

With earlier heads there is no chamfer so the *squished* charge will have a greater direction change and therefore require more energy to get it to *work* as well as being less efficient.

 

Pete

[motoguzznix]

Pete

 

I once posted a scetch with the V11 combustion chamber shape here The discussion then was very similar to the actual thread including Daves piston comparison.

The MR Piston is ideal to cope with this combustion chamber.

To make the best of the stock pistons, you have to rework both cylinder and head to get a working squish area.

 

The LM4 combustion chamber has no chamfer in it but the V11 and 1100 Sport do have.

[pete roper]

The 'Big Valve' head/piston combination are one of the most horrid I've ever seen! I do remember on the 1100 Sport motors I've had apart that the combustion chamber shape was greatly improved, smaller valves too with better back shape. I couldn't remember about the chamfer but seemed to recall someone else mentioning it recently.

 

Pete

[chrisfer81]

I have a V11 2002 with front cross over (no O2 sensor), completly stock, with good adjustment check.

 

I have pinging problem since 3000tr/min -> 5000tr/min throttle large open.

 

I try to solve with PCIII 20% more rich in the pinging zone, the problem was partialy solved...

 

I have buyed Direct Link and just go back of 3° in this zone the problem is completly solved without any fuel enrichen.

 

I think really the solution is spark advance, try Tuneboy (or direct link) is the best way to solve pinging problem.

[dlaing]

I have a V11 2002 with front cross over (no O2 sensor), completly stock, with good adjustment check.

 

I have pinging problem since 3000tr/min -> 5000tr/min throttle large open.

 

I try to solve with PCIII 20% more rich in the pinging zone, the problem was partialy solved...

 

I have buyed Direct Link and just go back of 3° in this zone the problem is completly solved without any fuel enrichen.

 

I think really the solution is spark advance, try Tuneboy (or direct link) is the best way to solve pinging problem.

So, now where you were pinging the timing is just about perfect, so power and efficiency are now MUCH closer to optimal!

You must have a big smile on your face! At least that was my experience when I got the Tuneboy (not that the PCIII never gave me smiles, tuning the ECU just does so much more)

[Steve G.]

I've had issues with my V11 since brand new. Mine is untouched except Staintunes and Ferracci airbox, there have been no changes at all in the pinging situation. And I use 94 ocatane Chevron only on this machine. It seems to do it when near a full throttle, and only in the 5000-6000rpm rev window, which is a shame as this is a particularly usefull rev range where torque and hp are in a good usefull area.

If I travel in the USA, I find I'm short shifting the bike before 5000, where the best fuel you can find away from big hub cities is 92 octane.

I'd like to find the issue, but am not willing to spend thousands in pistons and head work to fix it, I find this method a real head shaker [V11, no pun intended].

Ciao, Steve

[GuzziMoto]

Milling the heads on a Guzzi is not that expensive. It is easy to pop the heads off, take 'em to a machinist to have them milled,and stick the heads back on. You do need to clay the pistons for valve clearence, but that is not as hard as it sounds. Even if you pay someone to do the whole job for you, it still should be under a grand. And adjusting the timimg with TuneBoy or some other way is a more direct approach to pinging. I think that improving the squish is a good thing to do that can help with pinging by adding turbulence in the combustion chamber. It also improves power(we all like more power, right). But taking a little timimg out is a more direct approach that does not have the same benefits as squish, but it should stop the pinging. EIther way, it is not an impossible to solve problem. And it is rewarding when you improve your bike over stock. That's a thrill most Jap bike owners will never truely know.