June 1st, 2014, 09:18 AM | #1 |
dirty boy
Name: Joe
Location: Johnstown, PA
Join Date: Sep 2012 Motorcycle(s): I don't even know anymore?? Posts: A lot.
MOTM - Apr '14
|
replacing exhaust cam with intake cam
There has been mention of this in a few different threads but no real info.
So the idea is that the intake cam has slightly more lift than the exhaust cam, running 2 intakes will give you more exhaust lift. Have seen things said like the following "yeah it might give you some gains" "no because timing will be off" Has anyone or does anyone know of anyone who has done this and the actual outcome? I'd like to get some solid feedback before i consider trying it.
__________________________________________________
I love the smell of burning pre-mix in the morning I don't think I'm a lot dumber than you thought that I think that I thought I was once. |
|
June 1st, 2014, 10:30 AM | #2 |
ninjette.org certified postwhore
Name: Eric
Location: Iowa City
Join Date: May 2009 Motorcycle(s): 2008 Kawmeracchi 350 2010 Project X Posts: A lot.
Blog Entries: 54
MOTM - Sep '18, Feb '16
|
I did it. And it made a huge difference with nitrous. But without nitrous it did not do much. There is a lot more lift with the intake cam then the exhaust cam and making the change to two intake cams has potential. I have not dialed them in yet.
But I know what I need and did move them in a good direction. I need to dyno it again to see what difference it made. But my feeling is it will make a difference when the cams are adjusted with a different center line.
__________________________________________________
Top speed 123.369mph. Ohio mile Worlds fastest 250 ninja |
|
June 1st, 2014, 12:19 PM | #3 | |
modaholic junkie
Name: Nick
Location: Athens, Greece
Join Date: Sep 2012 Motorcycle(s): 2001 ZX-12R, 2009 ninja 345cc and plenty of others in the past... Posts: 438
Blog Entries: 2
|
Quote:
1. imperative to alter (and experiment with) lobe center...as arough guide I recommend somewhere between 104-106 for intake and 105 (as is the ex cam adjusted from factory) for the intake cam at the exhaust... 2. if using OEM primary pipes with two intake cams you will see some little gains mostly in the low-mid range (about 1hp up to 9k) but no max hp gains... BUT peak hp will be broader in the high rpm range, the dive after 12k is smaller and if you give the thing a little compression by taking off the gasket under the block or miling the head for 0,2mm torque will be improved in the areas it suffers the most... 3. if you use a full exhaust system you will have a LOSS in the low rpm range because of the lack of backpressure and torque diagram becomes a "hill and valley" kind of thing UNLESS you increase base CR over 13:1 which saves the situation quite a bit. high rpm peak hp will have little gains but again the rpm band it is delivered broadens needless to say that in both cases muffler make no to minimal difference performance-wise... 4. I could provide more data if you had EFI since all P.C., bazaaz etc, help a lot by refining afr ratio but instead I think a have a couple of things to point out that I had mentioned long ago in a similar post a couple of years ago... I. it the intake of the 250 engine that lets the engine starving, not the exhaust... small throttle bodies(carbs), tiny ports, intake valves and intake cam DURATION @0,05"(the reason I don't mention overall duration is that it can be quite "deceiving" in many cases as to how "mild or wild" the cam profile really is AND is totally misinformative as far as valve acceleration and -most important- decceleration values it stresses the valve to). Considering you use oem valve springs there are certain limits of course...anyway ...if you make a regrind intake cam of about... say 234@0,05" (still "mild" profile, but easy to work on any engine stage) and port the intake you will FEEL the difference... combined with higher CR, it comes really close to the 300's performance...see why the 300 for only 50 more cc has bigger TB, Intake ports and valves but no change exhaust-wise... II. irrelevant to your question but I believe useful piece of info is another easy DIY work that helps a lot the engine's responsiveness and low rpm torque. Moving the rotor sensor by 2 degrees by making the holes with which it is bolted on the shell oval wider by about a little less than half an inch (1mm) Sorry I am not providing any photos but I don't keep any...
__________________________________________________
If noone has tried it before, I will !!! |
|
1 out of 1 members found this post helpful. |
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Need Exhaust Cam Ninja 250R 2008 - 2012 | SV Racing Parts | Items Wanted | 0 | October 5th, 2014 11:58 PM |
Finding carnage and replacing cam chain. | AFazakerley | 1986 - 2007 Ninja 250R Tech Talk | 91 | January 28th, 2013 07:52 PM |
So I have a mini HD cam... | Stingray1000 | Motorcycle Gear | 12 | June 19th, 2012 07:49 PM |
more gyro cam | alex.s | Videos | 4 | June 6th, 2012 07:44 AM |
cam timing | verandaman | 2008 - 2012 Ninja 250R Tech Talk | 0 | October 12th, 2011 01:27 PM |
|
|