Jashue Posted January 23, 2016 Share Posted January 23, 2016 Can anyone here give me an explanation for why Honda designed the stock exhaust with the valve that improves flow at higher RPMs? Why not have superior flow from top to bottom? There has got to be a reason for it, but I just can't think of what it might be. It's been a long winter already and I can't wait for spring (I live in Central New York). I ordered a Dam exhaust last week and I suppose it's on its way. The after-market pipe will screw up the gear indicator display right? A re-flash will take care of that, right? I was going to get a re-flash anyway... I figure that I'll be taking my bike to the dealer to get the re-flash, the pipe and the shaft recall taken care of in one fell swoop. This is exciting stuff! Link to comment Share on other sites More sharing options...
bigtallguy Posted January 23, 2016 Share Posted January 23, 2016 I think it was supposed to be something about improving low end torque with added back pressure. The new exhaust shouldn't do anything to the gear indicator, that happens if you add a Bazzaz Z-bomb or something similar. Link to comment Share on other sites More sharing options...
Darrenk Posted January 23, 2016 Share Posted January 23, 2016 I believe you'll get a check engine light unless the sensor is bypassed. I'm pretty sure the ref lash will take care of it Link to comment Share on other sites More sharing options...
Member Contributer RC1237V Posted January 24, 2016 Member Contributer Share Posted January 24, 2016 The error code will come up if you disconnect the wire harness from the solenoid that controls the exhaust valve. If you only disconnect the cable that operates the exhaust valve (flap), there will be no error code. My bike ran fine without a reflash, but it was probably lean, as it is most likely already on the lean side even with the stock exhaust. The dealer can only update the computer, not reflash with a custom map - for that send it to Don Guhl, he did mine after a pipe and de-cat and he nailed it! Link to comment Share on other sites More sharing options...
Member Contributer Skids Posted January 24, 2016 Member Contributer Share Posted January 24, 2016 Can anyone here give me an explanation for why Honda designed the stock exhaust with the valve that improves flow at higher RPMs? Why not have superior flow from top to bottom? There has got to be a reason for it, but I just can't think of what it might be. It's been a long winter already and I can't wait for spring (I live in Central New York). I ordered a Dam exhaust last week and I suppose it's on its way. The after-market pipe will screw up the gear indicator display right? A re-flash will take care of that, right? I was going to get a re-flash anyway... I figure that I'll be taking my bike to the dealer to get the re-flash, the pipe and the shaft recall taken care of in one fell swoop. This is exciting stuff! Jashue, I have a DAM end can fitted and my gear indicator works perfectly well & I've not had a re-flash. Simply remove the cable from its housing and return the rotor to the original position so it can rotate. It thinks it is still opening & closing the valve and everything works fine. Anecdotally, fitting the DAM improved both the fuelling & pick-up on my 1200....but then it could just have been me wanting to believe that as I have no evidence otherwise. Link to comment Share on other sites More sharing options...
Jashue Posted January 24, 2016 Author Share Posted January 24, 2016 Good stuff! Thank you all for the input! Link to comment Share on other sites More sharing options...
Forum CEO HispanicSlammer Posted January 24, 2016 Forum CEO Share Posted January 24, 2016 Strict noise control laws in Japan, it is supposed to help torque it does somewhat but in my experience it severely limited throttle response in low gear. Replaced mine and put in a gear trick device (mind is drawing a blank on the name of the darned thing) that tricks the bike indicating 3rd gear while in 1st and 2nd. Link to comment Share on other sites More sharing options...
Member Contributer hvfrdave Posted January 24, 2016 Member Contributer Share Posted January 24, 2016 Strict noise control laws in Japan, it is supposed to help torque it does somewhat but in my experience it severely limited throttle response in low gear. Replaced mine and put in a gear trick device (mind is drawing a blank on the name of the darned thing) that tricks the bike indicating 3rd gear while in 1st and 2nd. Z-bomb, probably the best mod for the VFR1200 without breaking the bank. Link to comment Share on other sites More sharing options...
RoystonRocket2 Posted January 24, 2016 Share Posted January 24, 2016 Can anyone here give me an explanation for why Honda designed the stock exhaust with the valve that improves flow at higher RPMs? Why not have superior flow from top to bottom? There has got to be a reason for it, but I just can't think of what it might be. It's been a long winter already and I can't wait for spring (I live in Central New York). I ordered a Dam exhaust last week and I suppose it's on its way. The after-market pipe will screw up the gear indicator display right? A re-flash will take care of that, right? I was going to get a re-flash anyway... I figure that I'll be taking my bike to the dealer to get the re-flash, the pipe and the shaft recall taken care of in one fell swoop. This is exciting stuff! Anecdotally, fitting the DAM improved both the fuelling & pick-up on my 1200....but then it could just have been me wanting to believe that as I have no evidence otherwise. I also have a DAM on mine and it definitely improved fuelling and pick up. Link to comment Share on other sites More sharing options...
lshark Posted January 27, 2016 Share Posted January 27, 2016 the valve is all about meeting govt restrictions......i wouldn't get the Honda dealer involved in the Guhl reflash...the ECU is easy to remove, if you can't do it have an independent shop do it......the only thing that effects the gear pos indicator is the z bomb Link to comment Share on other sites More sharing options...
lshark Posted January 27, 2016 Share Posted January 27, 2016 the Guhl reflash is a night and day difference .....i had a 2010, put the zbomb on (1500 miles) before the Guhl option was available....made a nice improvement but had a drawback, the gear indicator....added a bazzaz Z-fifuel controller (17,000 miles) and that helped..... i did the Guhl reflash (38,000 miles) and the difference was amazing !!!! bike was totaled (44,000 miles) and i bought a brand new 2012....rode the bike stock for a few hundred miles and it was horrible, i'm spoiled...reflashed it and it runs better than the 2010 ever did......the Guhl reflash costs less than a PC V or Z-Fi and gives much better results, no splicing into the wiring harness, no external box under the seat....i've driven the 1200 in every mode....the Guhl reflash is the way to go Link to comment Share on other sites More sharing options...
Member Contributer Skids Posted January 27, 2016 Member Contributer Share Posted January 27, 2016 Surprised to hear your 2012 was horrible...in what way? I'm considering the Guhl re-flash but at the moment struggling to find a reason why I should. Link to comment Share on other sites More sharing options...
Member Contributer swimmer Posted January 27, 2016 Member Contributer Share Posted January 27, 2016 I've put 22k miles on my '12 that I bought in Oct '14. I like it fine with no re-flash but maybe its a case of not knowing what I am missing. Now that I am out of warranty my main hesitation for getting the re-flash would be the chance that it decreases my mpg. Link to comment Share on other sites More sharing options...
Member Contributer EhViffer Posted January 27, 2016 Member Contributer Share Posted January 27, 2016 Happy with the Guhl re-flash on the 2010 but having ridden my wife's 2012 many times can't say it needed it in the same way my 2010 did. Out of the box the 2012 we bought did not have the low rpm stutters the 2010 did. Just my own experience having both a 2010 and 2012 VFR 1200 in the garage. Link to comment Share on other sites More sharing options...
lshark Posted January 28, 2016 Share Posted January 28, 2016 the first second gear restrictions on my 2012 were just as bad as my 2010.....MPG is the same after reflash, Surprised to hear your 2012 was horrible...in what way? I'm considering the Guhl re-flash but at the moment struggling to find a reason why I should. the first/second gear restriction was annoying, bordering on dangerous imo.....the elimination of the on/off throttle choppiness and drive train snatch is worth the cost of the reflash.....the extra power is icing on the cake Link to comment Share on other sites More sharing options...
Member Contributer Skids Posted January 28, 2016 Member Contributer Share Posted January 28, 2016 the first second gear restrictions on my 2012 were just as bad as my 2010.....MPG is the same after reflash, Surprised to hear your 2012 was horrible...in what way? I'm considering the Guhl re-flash but at the moment struggling to find a reason why I should. the first/second gear restriction was annoying, bordering on dangerous imo.....the elimination of the on/off throttle choppiness and drive train snatch is worth the cost of the reflash.....the extra power is icing on the cake Annoying/dangerous how? I just don't see that on mine. Neither do I have any throttle choppiness and only very minor drivetrain lash. Perhaps I'm lucky.....or just too stupid to spot the issues. Link to comment Share on other sites More sharing options...
lshark Posted January 28, 2016 Share Posted January 28, 2016 does your bike pull evenly at full throttle through 1st gear or does it hit hard at 6000 rpm ???? Link to comment Share on other sites More sharing options...
Member Contributer Skids Posted January 28, 2016 Member Contributer Share Posted January 28, 2016 does your bike pull evenly at full throttle through 1st gear or does it hit hard at 6000 rpm ???? I'll let you know in 3 months time....I'm away digging sandcastles at the moment. Link to comment Share on other sites More sharing options...
RoystonRocket2 Posted January 28, 2016 Share Posted January 28, 2016 does your bike pull evenly at full throttle through 1st gear or does it hit hard at 6000 rpm ???? My 2013 pulls evenly at full chat. I've got the DAM exhaust on it and see no reason for a re-flash. It's pretty much as Skids describes and the drivetrain lash is only noticeable at very slow speed such as manoeuvres in car parks or similar. Give it the full beans with a hint of aggression and it's spinning up and the TC is cutting in anyway. Link to comment Share on other sites More sharing options...
lshark Posted January 28, 2016 Share Posted January 28, 2016 you really have to ride a reflashed bike.....you don't know what you're missing the first thing you have to do is turn that TC off Link to comment Share on other sites More sharing options...
RoystonRocket2 Posted January 28, 2016 Share Posted January 28, 2016 you really have to ride a reflashed bike.....you don't know what you're missing the first thing you have to do is turn that TC off Why? And...erm...why? Link to comment Share on other sites More sharing options...
Tamworth Posted January 28, 2016 Share Posted January 28, 2016 the first second gear restrictions on my 2012 were just as bad as my 2010.....MPG is the same after reflash, Surprised to hear your 2012 was horrible...in what way? I'm considering the Guhl re-flash but at the moment struggling to find a reason why I should. the first/second gear restriction was annoying, bordering on dangerous imo.....the elimination of the on/off throttle choppiness and drive train snatch is worth the cost of the reflash.....the extra power is icing on the cake stock 1st gear is not dangerous in any way unless you're going full throttle in 1st, then the power comes in a little abrupt, very few mature riders go hard in 1st like that and when you do you usually know what to expect.. The Guhl reflash does nothing to remedy the snatchy low speed, it simply removes 1 and 2nd restrictions. Yes it makes a huge difference in 2nd gear hard acceleration, but that's the only improvement on a 2010 Link to comment Share on other sites More sharing options...
CandyRedRC46 Posted January 28, 2016 Share Posted January 28, 2016 Can anyone here give me an explanation for why Honda designed the stock exhaust with the valve that improves flow at higher RPMs? Why not have superior flow from top to bottom? There has got to be a reason for it, but I just can't think of what it might be. It's been a long winter already and I can't wait for spring (I live in Central New York). I ordered a Dam exhaust last week and I suppose it's on its way. The after-market pipe will screw up the gear indicator display right? A re-flash will take care of that, right? I was going to get a re-flash anyway... I figure that I'll be taking my bike to the dealer to get the re-flash, the pipe and the shaft recall taken care of in one fell swoop. This is exciting stuff! You do not need superior flow at the bottom. An engine is an air pump. At low RPMs, it is not pumping much air. So you do not need a high flowing exhaust at lower RPMs, but it does need to be quiet, specifically at half of peak horse power RPM and lower, AKA the vfr1200, which has a 10,000 rpm hp peak, must meet a certain decibel requirement from around 5,000 rpms and lower and after 5,000 RPMs or so it can be a little louder and it will need more exhaust flow as well. This is why Honda and a lot of other manufactures as well are always doing things to either lower the sound levels at the lower half of the power band or when this is not easily done, they will simply lower the peak hp RPM with ignition or throttle by wire limitations. This is why the vfr800 had the airbox flapper and vtec (which also improved emissions, mpg and debatably lowend torque), to keep the bike quiet at lower rpms, while still being able to provide air flow at higher rpms. This is also why the cbr1000rr has the ignition timing pulled by 9 degrees from 9000 RPMs until redline, to lower the peak hp rpm from 12,000 to 10,000 rpms, this way, the cbr only has to be quiet until 5,000 rpms instead of having to be quiet until 6,000 RPMs, which is a lot easier to accomplish. This is also why there is a simple zbomb fix for the cbr too. An engine never "needs" back pressure or an air box restriction for torque, you just simply do not "need to flow as much air at lower rpms as you do at higher RPMs and usually most things that add flow coincidentally add noise and vice versa as well. You don't need back pressure or air box restrictions. You do need to maintain air velocity, but backpressure, restrictions and velocity are not always related, though most people seem to think so and use these variables interchangeably, but they are not always interchangeable. Link to comment Share on other sites More sharing options...
Volfy Posted January 28, 2016 Share Posted January 28, 2016 does your bike pull evenly at full throttle through 1st gear or does it hit hard at 6000 rpm ???? Other than drag racing, I cannot think of a reason why I would want to ride WOT in first gear. Even when riding track, which is as aggressive as I would ever ride any of my bikes, the amount of time spend below 6k RPM in 1st/2nd gear is very very brief. For road riding, smoothness is king, and good throttle control rarely means anywhere close to WOT. It does mean keeping the engine in its powerband. The VFR1200 isn't a raw HP kinda bike. To me, it is much more enjoyable to ride it like a proper sportbike... than a dragster. For me, stock '10 with no bomb and no reflash serves me just fine. I do have a servo eliminator to keep the ECU from pulling a fault code after removal of the stock exhaust. But... everybody rides differently. Enjoy it however you see fit. Link to comment Share on other sites More sharing options...
lshark Posted January 29, 2016 Share Posted January 29, 2016 do you wear a bow tie when you ride your proper sportsbike ??? Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.