I might have an opportunity to have a custom cam shaft made for the Ralliart and if so, more could be made. To see if it would be worth it, I'd like to see how many would be actually interested in buying a cam shaft. No price or anything yet, but how many are actively looking to buy a Ralliart Cam Shaft. I am not garaunteeing that i'm gonna do this, its just a thought at this point.

 

Well, I would definitely be interested. However, this is something I would not buy until I saw exactly what the gains/drawbacks would be.

 

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Quick question: what does an aftermarket cam shaft do? I'm not that familiar with those...

Would it change the cam profile so that the valves would open more (or less?) in a specific MIVEC mode???

Also, don't these need custom gears to work properly???


As you can see, I really don't know much about that tuning method...

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Im a bit nervous about it but I'm leaving the country for 3 weeks so I may leave the ralliart at the shop. Does anybody have any info on how cams work and whats involved, any possible problems that might arise? I realize that we have MIVEC and that will only complicate things. I really don't know much about it.

 

I'm not sure the MIVEC would make any difference... since the more agressive profile should get the valves to fully open anyway.


Anybody with some actual knowledge of this who could step in tough???

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I think the guys in PR might have some insight on this......as I have no clue.

 

I think witha bigger cam your valves may drop too much. And this would cause the piston to hit it causes alot of damage to the engine. Not sure though.

 

A re-grind for this car will be very complex I really hope if you do plan on leaving your car in a shop it's a good quality shop. Generally with a cam you would see a loss of low end torque and a gain in high end. So if done properly it could be really good for mivec. It will also make your idle fairly choppy.

I don't know really all that much I'm sure some other people on here have more insight on the pros and cons.

 

Not quite... in my view, the idea here is not to open the valves more than they do when the high-revs MIVEC profile is engaged... it would rather be to see if any gains can be achieved by opening them a bit more when in the lower-revs profile...

This can only be done on the dyno, beginning with the same profile for the lower and higher mode and then gradually removing some of the lower cams height... and measuring the resulting curve with each modification. Then you analyse the dyno sheets and decide which configuration was the best... and produce the corresponding cam shaft.

One way you can work on the higher-revs mode could be to try and play woth the durations though... I'm not quite sure about that part.

Anyway, the two elements of the cams/valve tuning are lift (the lenght of displacement) and duration (the time the vavle stays openned). I'll let you imagine all the possible scenarios that can result from those two variables, taking into account that they can be adjusted for both valves (intake and exhaust).

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Yeah... if not done by someone knowlegeable, you can actually loose a lot of low-end torque and not gain anything appart from poor gas mileage. But anyway, you can count on far worst mileage than stock... even when done properly.

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You´re right but only if its too big; if someone makes aftermarket cams, they HAVE to make sure that there is enough clearance between the valves and the pistons (at least until a certain degree of advancement or retardness of the cam) or else they wouldnt work at all.

At least on Honda VTEC engines what I have seen is that in the stage 1 and 2 cams, the VTEC profile gets enlarged (though not sure if its for more lift, duration or both) while the normal profiles are kept within normal specs for drivability. Also, the larger the profile, it is recomended to swap the valve springs and retainers for stronger ones (specially but not limited to when the engine is going to be revved very hard) to keep the valves from floating and hiting the pistons.

What I´ve heard about the guys here in PR is that they have already found a way to advance/retard the cam (kinda like a sproket) but without the need for one.

Hope this helps with some questions

 

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Great info man!


There is a ton of knowledge coming out of PR but nothing making it's way to the market... I wish an American aftermarket company would hook up with some of these guys and market a strong performance products line for the RA (and 2.0 Lancers for that matter).

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i think there is a guy that has an other cam in the car... not a custom grind per sé more like a swap.. but ill confirm this on the morning...

 

Cam... we are SOHC people.

 

a couple things to consider...

do they want to make a turbo cam or NA cam? turbo cams dump fuel in low RPM's and give ****ty idles (kills the point of MIVEC), but this helps you spool up really really fast.
NA cams would probably leave the lower lobe with little change, while focusing on producing power up high.

Also, our car makes interesting use of pulse overlap. That is, if the cams where much different in either direction, the engine characteristics would be very different because of the way pulse of intake overlaps with a pulse of exhaust. this is especially delicate at the point where the MIVEC switchover occurs. Its both to make is smooth for the driver and smooth for the engine. Disrupting this could have unexpected results. Increasing this overlap just a bit too much will probably make you flood/puddle and decreasing too much will probably make you misfire/stall. To compensate, as you alter one cam profile, you would want to alter the other to compensate.

since the 2 profiles are so closely related, developing the cam isnt a trial and error thing like with other cars (get on a dyno, shave bit, dyno, shave a bit & dyno, etc, etc). Instead they would have to be simulated mathmatically using a pretty fun set of linear equations to ballance a change in the high profile with a corresponding change in the low profile.

that said, keeping the proportions as they are now may also not be ideal, so any trial & error would have to be done to figure out the desired overlap stagger before you even worry about lift/duration! And then you still have to worry about the sanity of the engine (smooth idle, safe redline, etc)!!

most shops are used to hondas where you want to modify the cam for peak power. not us. the ralliar is made for peak torque. the shop would have to be aware of this and develop for it. that is why the mivec switchover point is so crucial, as that is where peak torque is achieved. electronics would also probably be required to manage the mivec engagement point

in summary, our car has a VERY complex cam. To do it right, it needs some very skilled engineers, not just a few shop techs. I would want a contract in writting if I were to leave my car with a shop to do developmental cam work, as just as much can go wrong as right. either way, keep us posted, as if it happens, i would be very happy. Also ask about valve springs and cam gears, as they woud probably also be needed