allanallen 528 2 Cars Posted May 24, 2006 Alrite guys, Im in the process of making up an inlet manifold for a set of r1 carbs ive spaced out to match my mi head. I can make the manifold 2 different ways; 1, very short (1.5-2) pipes coming straight from the head at 90 degrees and the carbs sitting at the same angle as the engine. 2, longer pipes with a bend in them, bringing the carbs further forward and sitting level (similar to the boggbros one). Im leaning towards option 1, I believe the carbs will run at this angle but am worried about air flow to the carbs as theyll be pointing towards the bonnet rather than the front of the car. please let me know your thoughts opinions on this as I dont have much knowledge on this sort of thing. cheers al Share this post Link to post Share on other sites
Rik 0 Posted May 24, 2006 For option 1. Are you not going to have clearence issues with the pipes coming out at 90 Deg? I'm not fully understood what you mean but i know at 90 Deg they wont fit! Option 2 sounds good, i'm not sure how th ebend should be so i'll be interested in seeing what comes of this thread. Rik Share this post Link to post Share on other sites
Pug_101 0 Posted May 24, 2006 I assume your using DCOE's therefore shouldn't the carb sit horizontal so the floats work properly? Also option 2 with the longer manifold will give more low down torque. Option 2 sounds right to me and as it's basically a copy of a well known system should work Ok. Plenty of carb'ed Mi on here so should get some more feedback soon. Cheers Share this post Link to post Share on other sites
Dom9 2 Posted May 24, 2006 I assume your using DCOE's No, these are R1 bike carbs... The only thing that worries me is the bonnet - Carb clearance issue for option 1. If you look at an R1 bike, you can see that the engine sits at a similar angle to the Mi16 in the 205, so I would have thought that it would be fine to have the manifold pipes coming straight out of the head and the carbs sitting at that 20° odd angle. Like the others have said though, you may not be able to get the optimum length for pulse tuning in the inlet. My best guess would be that you would want a fair bit more length than you can achieve with option 1. I'm guessing that's why the Bogg Bros use something similar to option 2. By putting a curve in the manifold and running them almost level, you are able to utilize the space between the radiator and the head to get a little more induction length. Frankly, I think either will work and option 1 is nice and simple. It may be worth finding the induction length calculator on google, think someone posted a link in another thread, perhaps petert, to work out the kind of length you want. Once you know that length, see whether it can be accomodated by option 1, if, in the unlikely event it can - go that route! If it can't then you have option 2, which is slightly more complicated but will result in getting the best out of your engine! Whichever route you choose, post lots of photos!!! Share this post Link to post Share on other sites
allanallen 528 2 Cars Posted May 24, 2006 DOM9, I dont think i've got enough of the info to fill in the induction length calculator. Does it drastically alter power/engine caracteristics having a short inlet length?? I'd like to go down route no. 1 as of its ease and because i haven't relly got the facilitys available to bend the pipe. Another option i thought of could be; 3, have the pipes coming off the head level and modify the top engine mount to clear the pipe.(hope that makes sense). Share this post Link to post Share on other sites
Rippthrough 98 Posted May 24, 2006 (edited) Bike carbs should run well at allsorts of angles, they have to work when the bike's on one wheel (front or back) and cranked over side to side. Edited May 24, 2006 by Rippthrough Share this post Link to post Share on other sites
M3Evo 0 Posted May 24, 2006 Think it's pretty safe to say that inlet tract length does make quite a difference and that there's not all that much room if you come off the Mi head with a perpendicular inlet system, as I've found with my DTH bodies. On my own engine, I ended up making a very short (about 150mm) and very large diameter (48mm tapering down to 40mm) inlet runners and it's definately cost me some low down torque (on the arse dyno) although having said that it all comes flooding back at around 2250rpm. Share this post Link to post Share on other sites
Dom9 2 Posted May 25, 2006 As Alex says, the difference could be quite surprisingly large, but it will move the power around teh rev-range, so you will usually get it back at some point... I guess you have to decide what rev-range you are looking to work in! Post up the link to the calculator again and let's take a look. I guess the best thing to do is go through th ethread that discusses the inlet tract length and copy something similar to that... I'm guessing it's going to be a fair bit longer than you can achieve with option 1. I don't think option 3 really helps much in that regard... Go with option 2, it will make things easier in the long run I reckon! Share this post Link to post Share on other sites
allanallen 528 2 Cars Posted May 26, 2006 dom9, on my third option i meant modify the top mount to clear a longer pipe not the carbs themselves. doing this would give a longer inlet tract but the flow would have a sharp 20degreeish corner as it reaches the head. i quite like this idea as i dont have to do any pipe bendin. heres the link i was lookin,not sure if its the right 1. I'm tryin to find out the spec of my cams off the guy i bought the engine off. http://www.btinternet.com/~mezporting/exhaust_length.html Share this post Link to post Share on other sites
Dom9 2 Posted May 26, 2006 The simple answer is to avoid any sharp changes in angle and 20° will definitely affect your flow, how much and whether it is actually that detrimental is anyone's guess but I reckon you could get option 2 done pretty easily if you make friends with some guy with a pipe bender... If you're really lucky, you might find some hot girl with a pipe bender, but I doubt it... I haven't looked through that link in detail but it looks like it's for the exhaust manifold, in which case, my intial response is to say it's wrong. However, it may be that it can be used for the inlet by substituting the exhaust duration etc for the inlet duration... Let me see what I can do over the weekend as I have it all written down somewhere, whatever happens though, you will need your cam spec! Share this post Link to post Share on other sites
allanallen 528 2 Cars Posted May 26, 2006 dom, your right it does look like its for exhausts, didn't notice that before. i'm waiting on migti (off this forum) to let me know the cam specs. As for the pipe bending, i did a google search for 'hot girls bending pipe', the results where fairly interesting but not very helpful Share this post Link to post Share on other sites
