Do full exhaust systems damage piston rings?

[jhoffa 8]

So I've been told that full exhaust systems damage piston rings and, as a consequence, the engine itself as a result of a poor mixture of gas and air. Here are some pics of a Z800 that a friend sent to me.

He told me that the mixture overheats and in the Z800 these carbon deposits accumulated after 6 months of use. As a result, this overheating creates rigidity and tightness in the piston rings which in turn damages the engine. Furthermore, some points of overheating begin to develop and that makes things even worse. 

He also tells me that with a full system you lose back pressure and this causes a retention problem in the piston rings. 

My question is this: is there any truth to this? The guy sounds like he really knows what he's talking about and I'm unfortunately under-informed in this topic. I want to get a full system but I don't want to damage the engine and I certainly don't want to lose power at the low and mid rev range. 

 

 

 

 

Edited July 17, 2020 by jhoffa

[geophb 120]

No. 

Incorrect tuning for modifications is the problem.

[klx678 382]

If incorrect gas mixture was a serious culprit in situations like that I'd think all those extremely lean running carbureted bikes would have been in deep trouble years ago.

I'm on board with geophb, bad tuning is bad for an engine.  Like not jetting or having EFI properly programmed for an aftermarket exhaust.

 

[1down5up 15]

I've heard both that running an aftermarket exhaust tends to run a little lean, and also that these bikes are fine without tuning. A tech at a dealer told me that an exhaust like Yosh doesn't change the fuel air too much, that the onboard computer can compensate.

[geophb 120]

21 minutes ago, klx678 said:

If incorrect gas mixture was a serious culprit in situations like that I'd think all those extremely lean running carbureted bikes would have been in deep trouble years ago.

That is a good point. 

Typically the efi/newer bikes are "higher strung" though.  more compression, timing, closer to stoich at higher load conditions, lighter components etc  which is why the new stuff is much more sensitive.

Idk what motor those pictures are of but it looks like direct injection, based on that center bowl I see.  DI engines typically run very close to stoich even at wot.  So no tune plus exhaust= BAM 

[1down5up 15]

11 minutes ago, geophb said:

That is a good point. 

Typically the efi/newer bikes are "higher strung" though.  more compression, timing, closer to stoich at higher load conditions, lighter components etc  which is why the new stuff is much more sensitive.

Idk what motor those pictures are of but it looks like direct injection, based on that center bowl I see.  DI engines typically run very close to stoich even at wot.  So no tune plus exhaust= BAM 

Any idea if the MT has direct injection?

[klx678 382]

Don't forget ignition systems that detect detonation and will alter timing to cut back on it.

I'm kind of saying there are a lot of riders who install headers and don't bother to get modules reflashed or the like.  Plus if it would cause the big bang it would be heavily covered in all kinds of forums and there would be some serious publicized notification from the exhaust manufactureres.  Just not seeing it in print.   Just recommendations to do flashes to get max performance    Most will simply recommend  reflashes, not emphasizing it beyond comments.    Just not buying the big bang thing, without any emphasis on the need for electronics modifications from retailers and manufacturers to avoid severe damage.  You'd think it would be emphasized.

I found that when looking for an exhaust that would work with OEM modules.   Some may recommend reflash or the like, but some say it may work fine with the stock set up.  I know one definitely stated it would work with the stock settings, Delkevic said their 18" can exhaust did not require fuel mix alteration for my 700.  

Side note,  I'm not understanding how lean running and high heat will cause carbon deposits.  I always thought hot and lean would not build up carbon, but rather would heat the center of the piston to the point of melting.  But maybe that's just two strokes.

Edited July 17, 2020 by klx678

[cornerslider 794]

3 hours ago, 1down5up said:

Any idea if the MT has direct injection?

No, it uses throttle bodies. They are similar to a carburetor, but controlled electronically, rather than mechanically (pressure & vacuum). That is the best way I know how to explain it? Maybe another analogy would be "analog" compared to "digital". The fuel injection system on our bikes is pretty low-tech compared to higher end bikes.

If you have the money to add an aftermarket/free-flowing exhaust, you should do something/ANYTHING to control the fueling. If choose not to, you won't really gain anything (other than noise), and you also risk a "lean" fueling condition that (may) damage your motor one day.... 

I've done a "piggy-back" fuel controller (PCV), as well as an ECU flash on several different bikes. Both will accomplish about the same thing. There are pro's/con's to each. I personally like the ECU flash. I don't want/need to be able to change my fueling myself. Some people do, and like the PCV more. I like to think of it as cross-country road trip.... You can take the interstate and "get there", or take the scenic route.... Either way, you can get to about the same point-

[1down5up 15]

1 hour ago, cornerslider said:

No, it uses throttle bodies. They are similar to a carburetor, but controlled electronically, rather than mechanically (pressure & vacuum). That is the best way I know how to explain it? Maybe another analogy would be "analog" compared to "digital". The fuel injection system on our bikes is pretty low-tech compared to higher end bikes.

If you have the money to add an aftermarket/free-flowing exhaust, you should do something/ANYTHING to control the fueling. If choose not to, you won't really gain anything (other than noise), and you also risk a "lean" fueling condition that (may) damage your motor one day.... 

I've done a "piggy-back" fuel controller (PCV), as well as an ECU flash on several different bikes. Both will accomplish about the same thing. There are pro's/con's to each. I personally like the ECU flash. I don't want/need to be able to change my fueling myself. Some people do, and like the PCV more. I like to think of it as cross-country road trip.... You can take the interstate and "get there", or take the scenic route.... Either way, you can get to about the same point-

Wish i knew more about the CP2, all my other bikes except one have been I4's. I'm def partial to the flash for convenience, I'll prob change it twice, once now and once when I sell it. Reason I haven't flashed the ECU yet tho is I was still under warranty, and it voids it. Plus, I was told by a service guy that once it is flashed it removes the ability for Yamaha to do diagnostics.

Edited July 18, 2020 by 1down5up

[USMCFieldMP 49]

1 hour ago, cornerslider said:

No, it uses throttle bodies. They are similar to a carburetor, but controlled electronically, rather than mechanically (pressure & vacuum). That is the best way I know how to explain it? Maybe another analogy would be "analog" compared to "digital". The fuel injection system on our bikes is pretty low-tech compared to higher end bikes.

If you have the money to add an aftermarket/free-flowing exhaust, you should do something/ANYTHING to control the fueling. If choose not to, you won't really gain anything (other than noise), and you also risk a "lean" fueling condition that (may) damage your motor one day.... 

I've done a "piggy-back" fuel controller (PCV), as well as an ECU flash on several different bikes. Both will accomplish about the same thing. There are pro's/con's to each. I personally like the ECU flash. I don't want/need to be able to change my fueling myself. Some people do, and like the PCV more. I like to think of it as cross-country road trip.... You can take the interstate and "get there", or take the scenic route.... Either way, you can get to about the same point-

Direct injection or port injection has nothing to do with the throttle body, FYI. Both fueling styles use throttle bodies.

And the throttle body on this bike is cable driven, not electronic. The fuel system is based off of the MAP sensor (Manifold Absolute Pressure). This method of fueling is called "speed density"; it accounts the pressure, temperature, and sometimes another variable or two into its fueling map.

And much like cars, you'll still gain something with any small bolt-on modification that you do, as the MAP or MAF will see different flows. A tune can help any vehicle out though - even a stock one.

[cornerslider 794]

5 minutes ago, 1down5up said:

Reason I haven't flashed the ECU is I was still under warranty, and it voids it. Plus, I was told by a service guy that once it is  flashed it removes the ability for Yamaha to do diagnostics.

Honestly.... I think that's a "scare tactic" by Yamaha, as well as reason for Yamaha to get out of honoring the warranty (my personal opinion ). I had the same concerns about warranty issues when my FZ-07 was new (in 2016) as well. I went the PCV route for those EXACT same reasons. You can add a PCV without modifying any of the wiring/ECU. If you do have a warranty claim, you pull it off, put the OEM exhaust on. You're covered !!!! Once it was out-of-warranty, I pulled the PVC off the bike and sold it to another member on this site. I got my ECU flashed by 2WDW (a site sponsor, but I have no professional affiliation with them). If I knew back then, what I know now.... I would have skipped the PCV route, and gone straight to 2WDW. With the work the 2WDW did  with the ECU on my FZ-07, I was comfortable having them flash the ECU on my "new"  2019 R3 that I bought 6 months ago (potentially "voiding" the warranty).... 

Quite honestly, the CP2 motor that is in our bikes, as well as the XSR700, AND- the new T-700 adventure bike is nearly bullet-proof!!! Why else would Yamaha keep releasing different variations of same drivetrain, if there were any issues? I've been active in the motorcycle world for 40+ years. Yamaha has a proven record of "build-it -right", and keep re-releasing it with different body/colors/graphics for a decade or more- "repeat" until people don't buy in anymore...  It's  actually a pretty good "business model" if you think about it-

[cornerslider 794]

20 minutes ago, USMCFieldMP said:

Direct injection or port injection has nothing to do with the throttle body, FYI. Both fueling styles use throttle bodies.

And the throttle body on this bike is cable driven, not electronic. The fuel system is based off of the MAP sensor (Manifold Absolute Pressure). This method of fueling is called "speed density"; it accounts the pressure, temperature, and sometimes another variable or two into its fueling map.

And much like cars, you'll still gain something with any small bolt-on modification that you do, as the MAP or MAF will see different flows. A tune can help any vehicle out though - even a stock one.

I'm fully aware of how the throttle bodies work on our beloved bikes.... I never insinuated that our bikes were "ride-by-wire" as most higher end bikes are... I was simply trying to help members that may not completely understand how "basic" the FI system on our bikes is. There isn't really a need to over-complicate such a basic FI system like the one on the FZ/MT-07 platform-

[USMCFieldMP 49]

I agree with the "scare tactic" by a Yamaha service tech. I worked at a Yamaha dealership 15 years ago. Warranty work for sport bikes was rare. When it did come in, no one cared what was on your bike. If they do, take it somewhere else.

I honestly don't think you'll have any issues that'll even require warranty work though.

 

24 minutes ago, cornerslider said:

I'm fully aware of how the throttle bodies work on our beloved bikes.... I never insinuated that our bikes were "ride-by-wire" as most higher end bikes are... I was simply trying to help members that may not completely understand how "basic" the FI system on our bikes is. There isn't really a need to over-complicate such a basic FI system like the one on the FZ/MT-07 platform-

You're description was essentially wrong though, which is why I clarified. It's a simple port injection, speed density system that is still found on modern cars. It has nothing to do with the throttle body.

Edited July 18, 2020 by USMCFieldMP

[cornerslider 794]

10 minutes ago, USMCFieldMP said:

I agree with the "scare tactic" by a Yamaha service tech. I worked at a Yamaha dealership 15 years ago. Warranty work for sport bikes was rare. When it did come in, no one cared what was on your bike. If they do, take it somewhere else.

I honestly don't think you'll have any issues that'll even require warranty work though.

 

You're description was essentially wrong though, which is why I clarified. It's a simple port injection, speed density system that is still found on modern cars. It has nothing to do with the throttle body.

Okay-  I thought we were talking about the FZ/MT-07? I honestly don't know squat about cars-

[1down5up 15]

13 hours ago, USMCFieldMP said:

Direct injection or port injection has nothing to do with the throttle body, FYI. Both fueling styles use throttle bodies.

And the throttle body on this bike is cable driven, not electronic. The fuel system is based off of the MAP sensor (Manifold Absolute Pressure). This method of fueling is called "speed density"; it accounts the pressure, temperature, and sometimes another variable or two into its fueling map.

And much like cars, you'll still gain something with any small bolt-on modification that you do, as the MAP or MAF will see different flows. A tune can help any vehicle out though - even a stock one.

So most like our motors are port injected then? I'd doubt Yamaha would run a more expensive, higher pressure setup in an inexpensive bike like the MT

[Spatt 399]

20 hours ago, geophb said:

That is a good point. 

Typically the efi/newer bikes are "higher strung" though.  more compression, timing, closer to stoich at higher load conditions, lighter components etc  which is why the new stuff is much more sensitive.

Idk what motor those pictures are of but it looks like direct injection, based on that center bowl I see.  DI engines typically run very close to stoich even at wot.  So no tune plus exhaust= BAM 

More likely clearance for the electrode.  Pretty common practice. 
 

GDI isn’t available in motorcycles yet.  Couple patents have been placed but I haven’t seen anyone announce it yet, it would be big news.  Unless I missed it. 

[Spatt 399]

Also no.  An exhaust will not damage rings.  Rings are in tension on the cylinder walls.  They ride happily in one place on the piston most of their life, they don’t rotate in the bore.  
 

I think it’s funny when people mention back pressure needed for an exhaust.   The exhaust stroke works because their is a pressure differential and this is why your exhaust valves are smaller than your intake valves. 
 

Increasing pressure isn’t needed.  If you add back pressure it actually impedes scavenging at the beginning of the intake stroke cycle.  You want that to clear the final bit of spent exhaust from the cylinder.  
 

Ask your friend what value he believes back pressure is adding to the rings.  Your ring is just a seal.  No difference of a piston ring or an o-ring on a piston pump.  That’s all a motor is.  

[USMCFieldMP 49]

 

On 7/17/2020 at 8:35 PM, cornerslider said:

Okay-  I thought we were talking about the FZ/MT-07? I honestly don't know squat about cars-

 

Technically, I'm talking about both; the FZ-07 runs the same style fueling system: port injection - the injectors spray in the intake runners before the intake valves. The fuel system really doesn't have anything to do with the throttle body, other than that they are both integrated into the intake runners/manifold.

 

On 7/18/2020 at 9:03 AM, 1down5up said:

So most like our motors are port injected then? I'd doubt Yamaha would run a more expensive, higher pressure setup in an inexpensive bike like the MT

 

Modern motorcycles use EFI via port injection; older bikes were carbureted. I think Honda patented a direct injection system about a year ago, but I'm skeptical on how soon it'll be introduced to the mass market. They're generally a decent bit more expensive and require additional components... also motorcycles don't have nearly as stringent laws, like minimum MPG laws. DI systems also increase your upkeep (Google 'DI intake valve coking' to learn more).

 

On 7/18/2020 at 10:51 AM, Spatt said:

Also no.  An exhaust will not damage rings.  Rings are in tension on the cylinder walls.  They ride happily in one place on the piston most of their life, they don’t rotate in the bore.  
 

I think it’s funny when people mention back pressure needed for an exhaust.   The exhaust stroke works because their is a pressure differential and this is why your exhaust valves are smaller than your intake valves. 
 

Increasing pressure isn’t needed.  If you add back pressure it actually impedes scavenging at the beginning of the intake stroke cycle.  You want that to clear the final bit of spent exhaust from the cylinder.  
 

Ask your friend what value he believes back pressure is adding to the rings.  Your ring is just a seal.  No difference of a piston ring or an o-ring on a piston pump.  That’s all a motor is.  

Bingo. Modern EFI systems have the ability to account for changes in air flow too. That's the beauty of EFI - you really don't NEED to retune, but as I mentioned before, a retune can help just about any vehicle, even a stock one.

[geophb 120]

17 hours ago, USMCFieldMP said:

Modern EFI systems have the ability to account for changes in air flow too. That's the beauty of EFI - you really don't NEED to retune, but as I mentioned before, a retune can help just about any vehicle, even a stock one.

NO!  Not true.

Only efi with a wide band from factory can "tune" themselves with short/long term fuel trims.

Bikes such as the fz/mt07 with only an o2 sensor/narrow band can not. Its only used during cruising and light throttle.  Any thing outside 14.7:1 afr and the narrow band does not read it. 

[USMCFieldMP 49]

3 hours ago, geophb said:

NO!  Not true.

Only efi with a wide band from factory can "tune" themselves with short/long term fuel trims.

Bikes such as the fz/mt07 with only an o2 sensor/narrow band can not. Its only used during cruising and light throttle.  Any thing outside 14.7:1 afr and the narrow band does not read it. 

That's simply not true. Narrowband O2 sensors are used to set STFTs and LTFTs; you don't need a wideband. Additionally, STFTs and LTFTs are inactive once past a certain throttle percentage.

And I never said the bike would "tune" itself, just that it can account for changes in airflow - which is an absolute necessity. You are right that there will be no adjustment at WOT, but the stock tune on ANY vehicle - bike or car - has enough of a safety cushion purposefully built in to allow for bolt-ons like intake and exhaust before requiring a tune.

[geophb 120]

2 hours ago, USMCFieldMP said:

That's simply not true. Narrowband O2 sensors are used to set STFTs and LTFTs; you don't need a wideband. Additionally, STFTs and LTFTs are inactive once past a certain throttle percentage.

And I never said the bike would "tune" itself, just that it can account for changes in airflow - which is an absolute necessity. You are right that there will be no adjustment at WOT, but the stock tune on ANY vehicle - bike or car - has enough of a safety cushion purposefully built in to allow for bolt-ons like intake and exhaust before requiring a tune.

You are correct that the factory ecu will use the narrowband to change the fuel trims accordingly BUT it can only do this at lamda 1.0 (14.7 afr) +- .4 afr   AND the ecu target is 14.7 afr for all adaptive learning (because of narrowband limitations).  So as far as adjusting for modifications it is essentially zero.  Because high load and high throttle inputs are the critical areas as far as tuning goes, where afr is far richer than 14.7 (i.e. in the 13 range), where the narrowband CANNOT read.  And yes the factory tune disables adaptive learning at anything above 41% throttle.

Just trying to keep the information straight. This is directed by no means to you personally.  I just don't want future readers thinking the ecu will tune itself, because it will not.

 

[raysigh 9]

I'm confused by this thread now. 

If I have an aftermarket exhaust, I thought the reduced back-pressure is what causes an increase in the air to fuel ratio making the bike run leaner (and possibly hotter - possible valve damage in the future?).

Can this not be remedied by baffles to replicate the back-pressure the factory exhaust comes with - thereby negating the need for an ECU reflash or fuel remap?