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Just a question in regards to MIVEC tuning (posted here so its seen). Can you get piston to valve clearance issues with advancing the intake cam to its max range (28.8 cam degree’s) on a set of Kelford 272’s in a built 9.5:1 CR engine?
Of all the threads I’ve read, no one really goes into it being an issue. I’m ASSUMING that it won’t be a problem, but I would hate to find out the hard way. I’m just trying to wake the bottom end up on the 2.0L as best I can. Looking at the VVC map in the AEM shows that it hasn’t really been tuned.
Last edited by EVO GOES VROOM; Apr 2, 2020 at 12:46 PM.
It's a good question. I am inclined to say that the piston should not hit the valves using an unmodified Mivec gear since the mivec gear uses oil pressure to advance and retard timing. Some engines which have sat for a while will start before oil pressure is fully built and as long as the mechanical timing is fine, there should be no issues. Those bump stops in the mivec gear should be failsafes. Some people actually drive around on broken MIVEC solenoids, which could be stuck in either position. I would also look at some of the MIVEC maps on here in the tuning section to see how aggressive they get.
They 240ZTwinTurbo, how do you find the R2's?
Did make any gains from what you swapped from?
Went from S2 to R2 when on 10:1 2L in anticipation of stroker in the future. Didn't do any before/after from what I remember so you would have to search my build thread for any comments provided at the time. When I pulled the head for the stroker the tops of the valves had been mushroomed so I had to replace all the valves. Somehow they were beat by the rocker arms, which was a mystery to Curt and everyone else I contacted. We thought perhaps the aggressive ramp rates require higher oil pressure in the head so I removed the HLA and also went with the cast early rocker arms. Car really like to rev to 9K on the 2L, but doesn't feel like it is happy above 8.5K on the stroker.
I logged this a few years back and there was some explanation for it. Search mivec map vs actual by me in ecuflash if you're curious.
Problem is that I didn't raise the "MIVEC Intake Advance Max" so it was at the default value of 28.#. I swore I had raised this value, but perhaps I went back a tune revision for some reason and forgot to change it back. I played around today and raised it, but didn't want to push past 32deg. I'm going to play around with running negative overlap on the topend to see what it does to AFR. Perhaps it will breath better if I go to -2 to -4 degrees.
Problem is that I didn't raise the "MIVEC Intake Advance Max" so it was at the default value of 28.#. I swore I had raised this value, but perhaps I went back a tune revision for some reason and forgot to change it back. I played around today and raised it, but didn't want to push past 32deg. I'm going to play around with running negative overlap on the topend to see what it does to AFR. Perhaps it will breath better if I go to -2 to -4 degrees.
the one drawback to vipec. No negative values in mivec table for me
the one drawback to vipec. No negative values in mivec table for me
it did nothing on my gtr with stock head & cams on the Dyno, but maybe it will on this setup. If the AFR leans out then it is making more power and I will try a back to back tomorrow going negative above ~6500 rpm.
Went from S2 to R2 when on 10:1 2L in anticipation of stroker in the future. Didn't do any before/after from what I remember so you would have to search my build thread for any comments provided at the time. When I pulled the head for the stroker the tops of the valves had been mushroomed so I had to replace all the valves. Somehow they were beat by the rocker arms, which was a mystery to Curt and everyone else I contacted. We thought perhaps the aggressive ramp rates require higher oil pressure in the head so I removed the HLA and also went with the cast early rocker arms. Car really like to rev to 9K on the 2L, but doesn't feel like it is happy above 8.5K on the stroker.
I experienced exactly the same problem. R2's on my 2.4 with supertech std size valves. I pulled the head and all the exhaust valves on top of them where rocker arms have contact with them have been stripped in a point where the rocker arms where hurting the retainers. I also had kiggly HLA for a while which I removed and sold. I got back to the oem. I did not figure out why all my exhaust valves and retainers were hurt, while the intake valves were fine. The only assumption I could make was that the exhaust valves had the wrong tip height. I had the sodium filled valves if that matters
I experienced exactly the same problem. R2's on my 2.4 with supertech std size valves. I pulled the head and all the exhaust valves on top of them where rocker arms have contact with them have been stripped in a point where the rocker arms where hurting the retainers. I also had kiggly HLA for a while which I removed and sold. I got back to the oem. I did not figure out why all my exhaust valves and retainers were hurt, while the intake valves were fine. The only assumption I could make was that the exhaust valves had the wrong tip height. I had the sodium filled valves if that matters
Glad to hear I was not alone. Did you stick with the R2's?
Glad to hear I was not alone. Did you stick with the R2's?
I am switching to S3's as we speak. But i am keeping r2's too, in case i do not like them, but I have a feeling that S3's on 2.4 will be even better. If i lose maybe a few hunderd rpms probably I will not even notice it enough to bother me. If not, I will move back to r2's
