Backfiring?

[Way2Fast]

As I already pointed out, there is more to engine octane requirements than compression ratio and timing. Did you know you are actually changing the timing of the ignition event you change a fuel's octane?

There are many advantages and disadvantages to increasing an engine's compression ratio. To which "advantage" are you referring? If you are suggesting one may get better engine performance (power and economy) using higher octane, that would be true only if the rest of the systems are optimized to use it. An engine is not just a cylinder and piston, there is also the spark plug, ignition system, fuel delivery system, etc. Each of these sub-systems must be optimized for high octane fuel in order to use it.

Additionally, as you've pointed out, the engine's ECU controls ignition and timing across the entire RPM range. Considering this, why would lower octane fuel suffice for "puttering," but not full throttle? Wouldn't the ECU compensate during all engine operations?
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Yes, the ECU will do it's best to compensate for all engine operations. When "puttering" the engine is not being stressed enough to detonate so regular fuel use would be fine. When driven hard, the lack of octane will become noticeable and ignition timing will immediately be altered to compensate and reduce the tendency for "pinging" and possible engine damage. The resulting timing retard will result in lower overall performance. The Spyder engine is optimized for higher octane fuel
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How do you respond to my suggestion that if any advantages were to be had by using high octane fuel BRP would have suggested using it in the Spyder Operator's Guide?
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BRP only states that fuel with a minimum of 87 octane can be used. This is done to make the Spyder seem to be a more economical vehicle.
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Either you are sharing your opinion, or you have very specific information from a good source that leads you to believe using higher octane fuel will improve our Spyders' engine power and economy. Can you please tell us if your statements are just your opinion, or can you share your source?

Regards,

Mark

I am not only sharing my opinion on this matter, but that of BRP tecs.....without going into detail other than saying the factory testing center is practically in my back yard !! I answered some of your other questions but my replys appear as part of your above "quote"

 

[Danimal]

Well.... Kellogg's is in my back yard.... but I'm no expert on Frosted Flakes...... ;D


I'll go with the cold, hard data that was shared over at spydertalk.com... and save the extra money I would spend on 92 octane and buy some Frosted Flakes instead...... ;D

 

[Danimal]

I don't think what many are describing out here is backfiring..... just back-pressure. If your rotax backfires it will be VERY noticable..... loud POP..... NOT a bunch of small 'popping' sounds.

 

[Trypod]

I don't think what many are describing out here is backfiring..... just back-pressure. If your rotax backfires it will be VERY noticable..... loud POP..... NOT a bunch of small 'popping' sounds.

:agree: I had 2 older HD's, a 78 XL and a pre-evo FL, trust me, when those backfired, you knew you had a backfire. ;D I'll take the popping the Rotax gives me any day. :bigthumbsup:

 

[NancysToy]

I don't think what many are describing out here is backfiring..... just back-pressure. If your rotax backfires it will be VERY noticable..... loud POP..... NOT a bunch of small 'popping' sounds.

Tonight while we were riding, my BMW /5 ignition switch started cutting out. This happens with those blade type switches sometimes, when they get a bit corroded or dirty. As I was fiddling with it to get it to stay on, it quit for a second or so, then fired again...with a very loud backfire. Nancy was riding behind me on the Spyder, and thought for a second she had been shot! Definitely got her attention.

There are actually two kinds of backfiring. One occurs when a quantity of unburned fuel gets into the exhaust, as when my ignition switch quit. It then can ignite from the at of the exhaust or from the ignition, causing a very loud report! The other type has been attributed to an overly lean condition, and usually is seen as a small popping sound as you snap the throttle closed. This is still a backfire, just to a lesser degree. I fail to see how a lean condition can cause such a thing, and my theory is different, but that's what they say. Anyway, a lot of modern bikes, including my BMW R1100RT, have this condition. Heck, even my 65 Triumph Bonneville will do it from time to time, when conditions are right.

If the problem is frequent and persistent, it can have yet another cause. Burned exhaust valves, or valves out of adjustment (too tight) can cause some of the fuel mixture to leak into the exhaust pipe, then be ignited by the spark plug. I, too have seen this on my BMWs when the valves need adjusting, as well as on other bikes and cars. If your problem is frequent, and increasing, I would report it to the dealer. Let him be the judge of whether it is really a problem or not. That way at least if something fails later, you have reported it in a timely fashion.
-Scotty

 

[SpyderMark]

I love Google! Here is everything you ever wanted to know about exhaust pops and gurgles...

http://www.mikuni.com/tg_backfires_in_exhaust.html

Regards,

Mark

 

[1BlackWidow]

i have the aftermarket Hindle on my Spyder, and it definitely backfires a lot more than with the stock. I posted about this a month or so ago. See that post for more responses.
Good Luck!

 

[NancysToy]

I love Google! Here is everything you ever wanted to know about exhaust pops and gurgles...

http://www.mikuni.com/tg_backfires_in_exhaust.html

Regards,

Mark

Thanks Mark,
That explains why a lean mixture can backfire or pop. Too lean to fire in the combustion chamber. Well, gotta run. I've got an ignition switch to clean on my R75. Can't be scaring the Missus out of a year's growth anymore.
-Scotty

 

[Spydyr]

Re: What Type of Gas

There are a lot of interesting opinions here. I'd like to make reference to the 2008 Can Am Roadster factory shop manual($135 and 479 pagest of technical information). Page 469 , technical specifications, Compression ratio 10.7:1. Page 473, Fuel, North America, regular unleaded, 87 or higher. Page 185 , ignition timing , The crankshaft position sensor, the manifold absolute pressure sensor, and the throttle position sensor are the primary sensors used to control the ignition timing.

The ECM doesn't know what fuel it is using or at what octane and it doesn't adjust the timing accordingly. The BRP engine management system doesn't use a knock sensor, which is used in systems that are capable of retarding timing if detonation is could be a serious problem(Turbocharged or supercharged engines).

Cleaner burnng fuel injection lets the spyder run 87 octane, not a computer that adjusts timing. Carburated engines can't come close to accurately supplying fuel for varying loads, rpm, and air temperature, thus at higher compression ratios, they produce more oxides of nitrogen that don't meet emmisions standards, along with the occasional pinging.

When talking about 87 or 93 octane, they're so close your almost splitting hairs.

If you use a fuel with an octane rating far enough from the recommended rating, that it would damage your engine, your going to notice how poorly it runs long before it has a chance to harm your enigne.( like high octane race fuel or low octane diesel fuel).

With a compression ratio of 10.7:1 I would think that 91 or 93 would run better and get better fuel economy but I haven't had a chance to experiment with different fuels yet. I'm only on my third tank of 87. So far I'm getting 30 mpg and I don't think it runs as good as it should. I'm going to try 3 or 4 tank fulls of 91 and then 93, and compare seat of the pants data and fuel mileage.

 

[trumphair]

I got a lot of popping with my Hindle. Then, I put on Ken's O2 mod (I put on the air filter too) and it almost completely went away.

 

[Danimal]

Removed in protest of censorship. All of my tips will only be availabe elsewhere online.

 

[Way2Fast]

Well.... Kellogg's is in my back yard.... but I'm no expert on Frosted Flakes...... ;D


I'll go with the cold, hard data that was shared over at spydertalk.com... and save the extra money I would spend on 92 octane and buy some Frosted Flakes instead...... ;D

Wise ass remarks only show your general lack of intelligence ! Maybe if some of you buddies worked at Kellogg's and shared their knowledge with you, you would have learned something about "Frosted Flakes" !! Save your precious pennies and use regular fuel. I'll stick to 93. By the way, I have the Hindle and never had any pops !

 

[NancysToy]

C'mon guys, lets not get personal!

 

[Danimal]

Geesh..... can't anyone take a joke in this forum? :joke:


Sorry, but I'm more willing to take information from some of the various experts out here at face value - especially when they give links and sound explanations to back up what they are saying.... instead of just "someone heard from someone that works with someone at the BRP testing grounds.....etc...".

If you have reports and sound documentation to back up what you believe about 93 octane on the Spyder.... please share.... until then.... I consider it your opinion... which you are obviously allowed to have.

 

[RTGENE]

Hey Mr. D
Kellogg's make me smile and so did your comment.
smilingene

 

[SpyderMark]

Re: What Type of Gas

There are a lot of interesting opinions here. I'd like to make reference to the 2008 Can Am Roadster factory shop manual($135 and 479 pagest of technical information). Page 469 , technical specifications, Compression ratio 10.7:1. Page 473, Fuel, North America, regular unleaded, 87 or higher. Page 185 , ignition timing , The crankshaft position sensor, the manifold absolute pressure sensor, and the throttle position sensor are the primary sensors used to control the ignition timing.

Finally, someone with a shop manual speaks up!

The ECM doesn't know what fuel it is using or at what octane and it doesn't adjust the timing accordingly. The BRP engine management system doesn't use a knock sensor, which is used in systems that are capable of retarding timing if detonation is could be a serious problem(Turbocharged or supercharged engines).

This was my understanding as well. I was fairly certain the Spyder does NOT employ a knock sensor. If this IS the case, then higher octane fuel is a complete waste of money. However, as the old song says, if it makes you feel good, do it...

Cleaner burnng fuel injection lets the spyder run 87 octane, not a computer that adjusts timing. Carburated engines can't come close to accurately supplying fuel for varying loads, rpm, and air temperature, thus at higher compression ratios, they produce more oxides of nitrogen that don't meet emmisions standards, along with the occasional pinging.

Ahhhh, another true tech head! Regarding modern electronically controlled and actuated fuel injection, I am truly amazed at the strides that've been made in the last few years in this area. The precision newer EFI systems are capable of is so far beyond what was state of the art just a decade ago, it's almost the difference between fuel injection and carburetors.

With a compression ratio of 10.7:1 I would think that 91 or 93 would run better and get better fuel economy but I haven't had a chance to experiment with different fuels yet. I'm only on my third tank of 87. So far I'm getting 30 mpg and I don't think it runs as good as it should. I'm going to try 3 or 4 tank fulls of 91 and then 93, and compare seat of the pants data and fuel mileage.

I think you already answered your own question; the "system" as a whole is set up to properly burn 87 octane. Unless you change the computer's fuel injection mapping, there are no electronic controls that can advance ignition timing to take advantage of the slower burning high octane fuel.

Of the many that've tried, I've yet to see a credible report of performance or economy gains using higher octane fuel. Unless I hear differently from a BRP tech expert, I consider the case closed.

Regards,

Mark




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[Rotaxrocket]

When I was riding Harleys I had a ongoing issue with the pop from the exhaust. I spoke with one of the older mechanics told me that I had an "air leak". Supposedly when decelerating fresh air is drawn in around an air leak in or around wher the pipes are joined. This can be at the head to pipe or the pipe to muffler. He said usually on Harleys it is the head to exhaust pipe. An issue of negative pressure drawing fresh air in and mixing with semi-combusted fuel. Once the exhaust donut was replaced and some high temp sealer was put on there I didn't have any more issues. It may not work on Can Am Spyders as it may be something else. :doorag: :bigthumbsup:

 

[Zerocool]

I would agree with you based on observing my :spyder: recently.

My Hindel exhaust backfires more frequently than I'd like; between that and the squeeky brakes, one would think my name's Jethro Clampit (think Beverly Hillbillies) rolling along in an old jalopy.

The other day, when it was very humid, I stopped at the store, ran in quick, and when I came out I noticed a small puddle from the condensation under the pipe where it connects in. I'll have it checked out in a week when I take it in for service and let you know if that solves the problem.