EFI vs. carb models

[Clarke]

Just hope they don't start placing catalytic converters in the pipes like some companies. Suzuki is doing that with the otherwise sweet little TU-250. I bought one of the last 2008s with carbs and a tank with threaded badge holes. Just my choice. They are all fun, what the heck, FI, carb, won't have any choice with new ones anymore anyway.

 

[Speed3Chris]

Just hope they don't start placing catalytic converters in the pipes like some companies. Suzuki is doing that with the otherwise sweet little TU-250. I bought one of the last 2008s with carbs and a tank with threaded badge holes. Just my choice. They are all fun, what the heck, FI, carb, won't have any choice with new ones anymore anyway.

European spec EFI bonnies have pre cats in the headers which makes removing AI more problematic. US spec bikes don't have pre-cats in the headers. Its speculated that the stock mufflers on all EFI bikes have cats...but this is unconfirmed as I don't know anybody that has sectioned the stock exhausts to find out as most discard them anyway. They are sure heavy enough to have cats and another good reason to upgrade with better flowing pipes.

 

[PieMan]

Chris, the best figures I achieved from a standard EFI Bonnie with pipes, pods and a tune was 69.2bhp DIN @7,970rpm and the best figures from the same config with 39mm throttle bodies was 73.9bhp DIN @ 8,470rpm, so that's just over 4.5bhp at the top end and an extra 2ftlb torque @5,265rpm. I can see bigger increases coming with a ported head and/or larger valves, also a 904 should benefit more than an 865.

p.s. these figures are with pre-cats in the down pipes and AI removed, I haven't had any problems with the pre-cats

 

[Speed3Chris]

Chris, the best figures I achieved from a standard EFI Bonnie with pipes, pods and a tune was 69.2bhp DIN @7,970rpm and the best figures from the same config with 39mm throttle bodies was 73.9bhp DIN @ 8,470rpm, so that's just over 4.5bhp at the top end and an extra 2ftlb torque @5,250rpm. I can see bigger increases coming with a ported head and/or larger valves.

Thanks for that Mike. 4.5 hp seems very reasonable. Sounds like you turned up the rev limiter as well. The other thing is...there is real benefit to be derived by increasing the rev limiter with better cams like you have in your 790 motor versus stock 865 cams that fall flat at higher rpm. Believe there is 5 hp on tap just with 813 cams if spinning to 8,500 rpm.
I got to build my motor at some point.

 

[PieMan]

It's not just the cams as the EFI example shows. If your rev limit is set to 8,500rpm with standard 36mm carbs/TB's, as you go through the revs and approach 8,000-8,100rpm it starts to feel out of breath. With both the 38mm carbs and 39mm TB's you hit the 8,500rpm rev limit really quickly and with ease. Even the average 865 cams carry on making power almost to the rev limit, the revs just feel freer. :ride:

 

[Speed3Chris]

It's not just the cams as the EFI example shows. If your rev limit is set to 8,500rpm with standard 36mm carbs/TB's, as you go through the revs and approach 8,000-8,100rpm it starts to feel out of breath. With both the 38mm carbs and 39mm TB's you hit the 8,500rpm rev limit really quickly and with ease. Even the average 865 cams carry on making power almost to the rev limit, the revs just feel freer. :ride:

So if I understand you correctly Mike, what you are saying is with a stock EFI motor without opened up throttle bodies, maximum 69.2 hp is achieved at 7970 RPM and no further hp can be derived by spinning to 8500.
That makes sense and thanks for the clarification.
PS: your dyno tuning/map development talent for EFI bikes no doubt accounts for the excellent stock nos...well done.

 

[Stars&Bars]

I enjoy my 09 EFI Bonnie having just spun past 10,000 miles but wouldn't mind having a carbed version at all. Six one way half a dozen the other, as they say.
On the topic of hosspower, I like my stock motor and really have no intentions of hot rodding it up any higher. It does what it does very well and if I wanted more power, I would of bought a model with the amount I desired right off the showroom floor. I do agree that the stock peashooter muffs are just a little lower in tonal quality and are a bit heavier than I feel they ought to be but then again, my ears ain't what they used to be either after having been caught a few to many times without ear protection while waiting in a chow line while some airman run up the jet engine of to many F4 Phantoms in the hangar deck of the USS Coral Sea back in the early eighties.
The Bonnie is the most enjoyable motorcycle I have ever owned in over 30 years of messing around with these here donor cycles.
On the mag wheel models, it would be a major plus to be able to plug that tire and go but those spokes do look really retro and are one of the reasons I fell in love with mine so I plan on just keeping good rubber on her and keeping an eye peeled looking for nails and screws while out for a ride.
I sure hope all y'all enjoy yours as much as I do mine because it really is all about the experience of the ride and not just about how fast you can get to your destination.
Just my 2 cents worth.

 

[Speed3Chris]

I too have an '09 EFI bike only with spokes. Your comments bring discussion full circle. You and Ark make the case for leaving the bike stock and the other guys who have changed everything weigh in with the virtues of doing that. I like the middle approach as I think there are opportunities to improve the bike without reinventing it. Each style reflects the personality of each rider…what makes the bonnie platform so versatile. The bike is simple enough to alter any direction you want or just leave it alone and ride it as is. With you and Ark stating that you like the factory pipes…I have to say I just don’t get that. Which does allow me to understand all the indignation about Tors on this forum from the loud pipe club which further underscores how different each of us are as riders and yet we all like the same basic motorcycle.

Yesterday, I took my bike out for a brief fall ride and stopped for gas. There was a cool guy there on a real minimalist chopper…very bare bones hardtail really raked out. I had to talk to him and asked him if he made it and he said yeah. This thing was 60’s style beautiful in that it didn’t have a single part that wasn’t needed to get it down the road. The front tire looked to be no wider than 2 inches…and pretty skinny in back as well. I asked him if it was fast and he said, good enough but you didn't really want to ride it over 80 anyway...lol. I asked him what kind of frame it had and he said old Triumph. I wish I had my camera.
With all this discussion, time for a pic:

 

[PieMan]

I find it hard to understand anyone who would buy Bonnie and keep the standard factory pipes. They are fitted just for the sake of the law and make a Bonnie sound anaemic, I'm sure if the factory could get away with it they would fit TORS as standard.

I personally don't agree with all the talk about how crap TORS are, they're not bad silencers. I have carried out lots of testing with many silencers and yes if you want the very last ounce of power, you wouldn't use them. But they aren't bad silencers if you want good power, lower noise and like the style, they will get you within 90% of any power pipes out there and virtually the same power if the engine is tuned correctly compared with power pipes that have a half arsed engine tune. It's surprising how many owners spend many hundreds, even thousands on engine mods but consider the final fuelling/ignition timing/dyno time that brings all the mods together, as an extra and not part of the package.

 

[Speed3Chris]

I find it hard to understand anyone who would buy Bonnie and keep the standard factory pipes. They are fitted just for the sake of the law and make a Bonnie sound anaemic, I'm sure if the factory could get away with it they would fit TORS as standard.

I personally don't agree with all the talk about how crap TORS are, they're not bad silencers. I have carried out lots of testing with many silencers and yes if you want the very last ounce of power, you wouldn't use them. But they aren't bad silencers if you want good power, lower noise and like the style, they will get you within 90% of any power pipes out there and virtually the same power if the engine is tuned correctly compared with power pipes that have a half arsed engine tune. It's surprising how many owners spend many hundreds, even thousands on engine mods but consider the final fuelling/ignition timing/dyno time that brings all the mods together, as an extra and not part of the package.

It is really your dyno testing in fact that validates the Tors mufflers and so thanks for adding this measure of science Mike. When Tors are put down here by guys who prefer louder pipes I ask the question which never gets answered. Name a muffler that flows as well as Tors but is as quiet. There is never an answer. There are mufflers that deserve honorable mention...like the Dom tourings or Staintunes but both are louder. I know for fact that Sleepers and Togas don't flow better and they are much louder.
That said, I agree with you and would say most that the factory pipes go against the grain of what a motorcycle should sound like.
Especially emasculating the beautiful exhaust note of the vertical twin. Maybe in 50 years when all motorcycles are electric this convention will fall by the wayside.

 

[PieMan]

Maybe in 50 years when all motorcycles are electric this convention will fall by the wayside.

Fortunately I'll be pushing up the daisies by then. :cheers: