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Discussion Starter #1
I searched the 900 forum, and, still have questions about de-baffling the stock exhaust? I know that many members have done this 'mod' while waiting to gather the cash for a full exhaust system- so, there must be a ton of people who know the answers!

* What is the largest drill bit (1/2"?) that will fit between the inside wall and the the center baffle? Someone mentioned using a 15/32" bit, but, he didn't say it was a tight fit...

* What is the I.D. of the center counted baffle? I would like to use the largest possible bit to smooth the flow through the baffle. People had mentioned that there is a 'plug', or, a plate in the baffle, which should be punched out to increase flow...

* Has anyone used a variety of bit sizes to vary the hole sizes in the inside plate? I was considering putting 5 1/2" drill holes-evenly spaced- and then adding holes to increase flow by using progressively smaller bits each time. If anyone has already done that- how well did it work?

* Will a 3 1/4" hole saw be the MAX size that will fit the I.D. of the stock exhaust pipe? Apparently, for some reason, a 3" hole saw is not effective, but, 2 3/4" works, as well as 2 1/4"- but, so does a 3 1/4" hole saw. I'm sure why this is the case- but, if I can buy a hole saw that 'fits' the I.D. perfectly, I will buy that one.

My intent is to: deepen the sound of the stock exhaust, while increasing flow and reducing some of the back pressure. But, I also plan on modifying the stock airbox very soon- so, I will need to determine air/fuel controller works best with the 903cc engines fuel injection. ("Search" is my friend, but, also feel free to add input- looking for 'idiot proof', as I'm not strong with complex programming systems!)

At this point, Stage 1- cover plate removed, baffle cut back & 4 holes drilled in plate seems to be what everyone who has done it- wishes they stayed with. But, like everyone else, I will probably end up going Stage 2, with at least 8 holes- if not more. Which means I will have to marble it to reduce popping & whistling (varying the hole size may reduce it? Hopefully?)

At the end of the day, I would like to get the MOST: horsepower & torque available from this motor without tearing it down at all. So, intake & exhaust is where I will start, and, stock is what will cost the least. Besides, I love the look of the stock exhaust... Intake- I have no problem installing whatever aftermarket product produces the most (tuned) power- it's less of a concern.

Hate to create another de-baffle thread, but- experienced people will save me from cutting twice- which is expensive on chromed stainless steel!

Thanx in advance!

Dave
 

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I can't speak to the de-baffle questions, as I went ahead and replaced the stock pipes with aftermarket ones, but I can say that you will definitely need to look a controller if you modify the air intake for better flow. I would just suggest researching the controllers out there and getting the one that best fits your situation. I have the Dynojet PC V with the additional Autotune module. I am very pleased with the performance of the modules, and would recommend them to you with no reservations. Not the cheapest option available, but well worth the investment, imho.
 

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Not sure where you've found people that wish they stayed with 4 holes. I'm glad I removed the baffle completely and it seems there's quite a few like that. For one, 4 holes makes it a little louder; but not really a lot deeper. A full debaffle makes it a LOT deeper while only a little louder than just holes drilled.
 

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Along with a modified air intake, does a full de-baffle (of stock pipes) warrant a fuel controller - or is it only for aftermarket pipes (with modified air intake)?

Romper
 

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Discussion Starter #5
Romper- From what I have read- If you de-baffle AND modify/replace your intake, then you MUST add a fuel controller to prevent the bike from running lean, and, burning your pistons &/or rings. On lots of bikes, it's first noticeable by bluing of your exhaust pipes up by the cylinder, which is caused by heat. However, if you only change intake OR exhaust- you should be fine.

Romans 5.8- it was a common comment in a couple of the threads that I found when I used the "SEARCH" button? The common deal was: everyone did Stage 1, but, wanted a deeper, fully tone- so, they went Stage 2 (Hey, what's a few more holes amongst friends, right?). Often, looking for an even deeper tone, and, perhaps more power- they bought hole saws and just plain removed the inner plate & baffle altogether. Those people commented that they wished they had stayed with Stage 1 for the following reasons: Not much deeper with Stage 2, but, loss of back pressure may have reduced power, and, complete removal made the bike sound "thrashy" (not my word).

Sigmund-The only fuel controller I have looked up is the PC V (and accessories!) which could end up costing over $800.00 if I'm not careful. Thank you for your endorsement, it makes plunking down that kind of money a little easier, but, as stated above- I'm not good with those things, based on my personal experiences with stand alone engine management systems, Lemmiwinks, and other air/fuel management systems used on custom, turbocharged cars from my past. I need something Ron Popiel sells- "Set it and FORGET it!", because, if I can 'adjust' something, I will, which will ultimately lead to engine destruction. If you need a couple of really good moorings, lemme know- I have a few former engines that are available!

So, I'm cheap, and, REALLY love the look of the stock exhaust on a very clean, de-badged VN900C (it's friggin' perfect!), and, I would love to be able to get more air in as well- so, Cobra FI2000, or, DynoJet PC V w/ Autotune & broadband O2 sensor- here I come. But, I do want to make the mods in stages, which is where my questions come from. But, I will probably remove each exhaust, over wrap it and put it in a vise, so, access will be a little easier. Which had me thinking that maybe it will be easier to scrub off the inside weld of the baffle at the mount to make removal a little easier...

Also, if anyone has removed their throttle plates (inside the air filter housing, behind the throttle body butterflies) please share how it's working? It is supposed to increase throttle response, but, I'm not sure if it works, or, if it can damage the engine? Will removing them be aiding by adding the fuel controller?

BTW, I am looking for 'a little more' not a bigger engine. I like everything about the VN900C, and, don't want to ruin a good thing. But, if I can grab another 8-10 HP and a few Ft./Lbs of torque in a weekend of wrenching- I'm all for it. I don't want to shorten the engine life, or, end up with a peaky motor either, just a schnitzle more of a good thing...
 

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Just do the full debaffle. The 4 hole 8 holes sound like they have that helicopter effect to me. The full debaffle is a deeper tone. I did it in stages just to see and the full debaffel is the only way to go. Really is not very loud. In my opinion.
https://www.youtube.com/watch?v=lcCaN3rCbVw

I did take out my throttle plates. To me it is more hype then its worth. It might help a little. But ended up putting them back in. I have also read where others put them back in because they where having issues after removing them. idk.

I did do the intake, fuel processor, and cobra pipes. Then had it on a dyno. I gained 10 hp and 4lbs of torque. for a 1000 dollars was it worth it. Not in my opinion. I have taken off and sold the intake and processor. Honestly I think the bike runs a little better. I also would pull the cobra pipes and put the stock fully debaffled pipes back on. But I don't want to deal with shipping them.

If I did it all again here is what I would do. full debaffle and run it. No need to marble it. It will backfire and pop a little bit but no worse then it already did. You just could not hear it with the baffles in. Then just change things for cosmetics, looks, and comfort.
Justmy2cents
 
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