Can anyone do a write up about cam gear settings? Thanks.
Can anyone do a write up about cam gear settings? Thanks.
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A multi-volume library could be written about cam timing, and several are available if you would like to purchase some...
Without getting into extremely boring engineering equations, which have limited practicality anyway, here are the basics as they apply to the 4G63 DOHC setup and the commonly used types of cams:
There are basically 2 reasons to mess with cam timing, one being to move the powerband around to match the mods in an effort to maximize the usable powerband, and the other is to "fix" cams that are a poor match for the mods in the first place.
Next, there are 2 basic concepts related to cam timing, which are the relationship of the cam to the crank, and the relationship of the cams to each other since we have a twin cam motor.
The relationship of the cams to each other are commonly referred to as "overlap", and the relationship of the cam timing to the crank timing is referred to as "lobe center".
Here is an excellent write-up, which I won't bother to recreate since it covers what is important: http://www.starracing.com/Cam%20Lobe...0Explained.htm
So, back to EVO specific stuff...
Do you have crappy cams, or do you have good cams? If you have crappy cams, cam timing will be very important since you need to correct for a poor cam design. If you have good cams, you can use the stock cam gears...
If you have good cams but want to move the powerband around a bit, here are some rules of thumb.
-Retarding both cams will move the powerband up a few hundred RPM. On the EVO with the HKS 272 cams, a popular setup is to use 2 degrees retarded for both cams. Since both cams are moved evenly, the overlap doesn't change, only the lobe centers change, causing the valves to open and close later. In this case, the cams spin half as fast as the crank, so 2 degrees at the cam is 4 degrees at the crank. The crank will be an additional 4 degrees through its rotation before the valves open/close.
-Advancing the Intake cam, and Retarding the Exhaust cam will open up the overlap a bit. This allows the cylinder to fill sooner due to the intake valve opening sooner, which can sometimes be advantageous in a turbocharged engine.Or, the exhaust cam can be retarded more than the intake cam, as in a -1 -4 setup. Both cams are retarded in this situation, but the exhaust cam is moved more, increasing the overlap. Advancing the intake cam helps to improve the idle quality since the Intake cam has a larger impact on the idle than the Exhaust cam does. If you leave the Intake cam straight up, and retard the exhaust cam a lot, the idle will be lopier, but still much better than if you left the exhaust cam straight up and retarded just the intake cam.
Ultimately this is one of those cases where a dyno comes in real handy. You move the cams around until you find the right combination. Unfortunately theory only gets you so far, and practice makes perfect...
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when you say crappy cams do you mean brand or degree? ie HKS vs. someone else or 264 vs. 272 (+)
i assume you mean cams that dont match the engine application very well, but clarification would be nice
People do not care how much you know until they know how much you care<br /><br /><br />[quote author=evomrguy link=topic=34096.msg6904129#msg6904129 date=1166072308]<br />Jeezus, this is the kinda thing best left to try on $500 1g t/e/l. If your board pick one up and let the ghetto bull shit mods fly. [/quote]<br /><br />forza ferrari
Ultimately the cam profile needs to be appropriate for the setup. If you have to tweak the cam timing just to make it run right, perhaps another cam profile would have been a better choice.
All da cars are Nekkid!Â* www.dsmporn.com<br /><br /><br />www.roadraceengineering.com
hmmmm ... would you consider the pipers a poor desing?? Since they do require for you to purchase cam gears and to adjust them in order to get the best results out of the cams.
''Yo, a$$G@@! This motherfucka's dead! Ain't no Chris Angel Mind freak, David Blaine trapdoor horseshit jumpin' off here!''
Moving the cam timing around to extract that last 5-10HP, and moving the cam timing around to make the low end throttle response not suck so bad are two different things.
I figure if the manufacturer knows you need to move the cams X amount of degrees to make it run right, they should have just put that into the cam profile from the beginning.
All da cars are Nekkid!Â* www.dsmporn.com<br /><br /><br />www.roadraceengineering.com
this is a hairy subject that i wasn't gonna tackle for some time... but since it's here i'll start compiling info. i'll sort through this crap later i have something to do atm.
Originally Posted by Ted BOriginally Posted by Ted BOriginally Posted by Ted B
Originally Posted by LudikrautOriginally Posted by Ted B
Originally Posted by earlyapex
search is your friend... wish i could of done a back to back of 272/280 +2 - 2 vs -2 -2 ...Originally Posted by leaveit2bevo
i want to try +4-2 on what i have or perhaps 280/280
''Yo, a$$G@@! This motherfucka's dead! Ain't no Chris Angel Mind freak, David Blaine trapdoor horseshit jumpin' off here!''
your mainly aiming for top end ... while advancing the intake by +2 or +4 will get you bottom end results....Originally Posted by leaveit2bevo
''Yo, a$$G@@! This motherfucka's dead! Ain't no Chris Angel Mind freak, David Blaine trapdoor horseshit jumpin' off here!''
+4 -2 on 280s is almost a two stroke engine... why do you want your intake valves to make out with your exhaust valves. it also won't idle unless you somehow attatch some cylinder extensions to make it 5 liters.
had that set up on the cosworth (i do realize is a different camshafts set up) but a +4 -2 worked wonders ... spool up and tq was beautiful... i also believe others have use a +2 -2 set up on the 280s HKS cams in order not to sacrifice all the midrange on the camshaft set up and not gain just top endOriginally Posted by trinyDeX
''Yo, a$$G@@! This motherfucka's dead! Ain't no Chris Angel Mind freak, David Blaine trapdoor horseshit jumpin' off here!''
cams
I'm running (I think -3/-3) right now on my stock turbo with 280 cams and its doing shit for me ... I wish I knew what TTP did with that Evo they tuned so I could try some new cam gear settings .. but it looks like I will try +2/0 at my next oppourtunity + a retune ... and if yields me yet even more shittier results I'll just flash back to my current tune and go back to the recommended -3/-3 ...
I'm having a ridiculously hard time making good power (numbers and powerband) even after 2 retunes ...
2014 WW Evo MR ~ Derick 3.0
Its a Stg 1+ with 280 cams instead of 264 or 272's .. Should be knocking on 300whp with a comparable curve ... and its been tuned ... twice ... I really gotta crack my cam gear cover off and see if its slipped a tooth or something- that or try new cam gear settings ... 264whp is just pathetic where as other evo's on that same dyno and similar mods were in the 300+whp range w/ comparable torque ...
2014 WW Evo MR ~ Derick 3.0
Would it be safe to try the +2/0 cam gear setting on a set of 272i/264e setup? Also how is the idle with this setting??? i currently have mine set at -3/-3 from the Vishnu site (what they recommend on the Stage 1+) and the cams lump pretty good...just wondering...dont get me wrong...i would perfer performance over sound anyday...