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Discussion Starter · #1 · (Edited)
I have datalogged it many times... out of the blue VTC command spikes to 45degrees while driving. this is well after the motor is started & warms up.

in the past I heard when you start the car the ECU will test VTC... we'll its not when the car is started but it happens a couple of times during the driving cycle.

know your clearances :rolleyes:

explained by hondata http://www.hondata.com/forum/viewtopic.php?t=9701

here it is on a k24a2 (25* gear) @ 1:00 (on the calibration there is no vtc setting higher than 25vtc)



luckily for me everytime I have seen it happen it happens at partial throttle EDIT - it appears at part throttle on the low cam. So you don't really have to worry about the ecu "vtc sweep" unless you are running a vtec killer setup. But there are other concerns - mainly oil pressure
 

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I agree 100%, degree your cams, check your p2v and v2v clearances if you want to have a good, long lasting motor.

Getting a vtc gear machined is not that much or that hard to do. So spend the $50 and save your $5000 (or more) motor.

Stefan
 

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I wonder if its a completely random event or if the ecu chooses when to do it based on parameters. It would be stupid to have the ecu do this on the high cam as im sure Honda would have known people using aftermarket cams would have a good chance of popping their motors. Glad I switched to an RBB VTC gear with the Blueprint stage 3s im using.
 

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Discussion Starter · #4 ·
I wonder if its a completely random event or if the ecu chooses when to do it based on parameters. It would be stupid to have the ecu do this on the high cam as im sure Honda would have known people using aftermarket cams would have a good chance of popping their motors. Glad I switched to an RBB VTC gear with the Blueprint stage 3s im using.
I have datalogged the event 3 or 4 times... each time TPS is very low (5-7%) partial throttle on the low cam. I do not drive around on the biglobe all that often especially for an extended period of time. I will continue to log & monitor it tho

BTW - who can machine a stock TSX gear for me? thanks in advance
 

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I've never seen a CAMCMD spike happen in VTEC. It's already widely known that if your primary lobes are not 50deg VTC safe, then you cannot rely on the ECU to keep the cams from advancing beyond desired limits. This also applies for k20a3 cams that have a very large main lobe or for VTEC killer cams.

I can't think of a single major brand camshaft for the 3-lobe VTEC system that has p2v interference at 50deg advance on the primary lobes. VTEC lobes, yes. For the 2-lobe VTEC system, almost all of the stage III cams require a modified cam gear.

Too add my own experience, I drove around for 1+ yr, or about 20k miles with cams that were not 50deg safe on the big lobe (45deg max) and never had any v2p contact issues. When the motor came apart, there were no signs of contact on the pistons. If you are 45deg safe, then you shouldn't set the ECU to aim for more than 40deg as there is some hysteresis resulting in +2-3deg from the target.
 

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Well I have a tsx engine and cam angled which is locked in at 30 Degrees. I haven't had any problems, but then again I don't really daily drive the car. It really sucks if happens but hey shit happens. Even if you have Vtc machined something else might fail like tensioner.

The VTC spike maybe something to do with software glitch? Just thought..
 

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I was always under the impression that if one would over-rev (mis-shift example) that the mechanical momentum would naturally override the ECU. And isn't that an area most prone to P2V incidents? I sent my VTC gear to supafly to machine to 45deg.
 

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I was always under the impression that if one would over-rev (mis-shift example) that the mechanical momentum would naturally override the ECU. And isn't that an area most prone to P2V incidents? I sent my VTC gear to supafly to machine to 45deg.
the oil in the chambers of the VTC gear do a pretty good job of preventing accidental advance from a mechanical overrev.
 

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A user named suprfly supposedly used to machine them. I have PM'd him asking if he still does it but I haven't gotten a response.

Does anyone know exactly what needs to be machined and how much needs to be machined off?
This is an article that I used as a baseline for my upgrade "ideal".
http://www.hondata.com/tuning_the_tsx.html
The person to get in touch with is "supafly". I think he is a moderator here too. If you go with someone else to machine the gear you'll want to specify that you want a transition in the corners so it's not a straight corner but a 'lil rounded for strength.
 

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I ran DC4 cams with Wiseco 12.5 pistons on a 50* vtc gear and limited cam angle to 32* in k-pro. I never really datalogged to see if it would do a vtc sweep but I know it does in low cam range, but not in vtec. I have definitely revved my motor to 10k rpm's or higher on accident a few times and never had contact issue. Motor looked perfect when pulled apart. If you're worried about it, get a TSX vtc gear machined or get 50* safe cams.
 

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Great info. I will be remembering this for when I get my big cams.
 

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I wanted to know about using 50* vtc Im gonna b using dc4 with 12.5 pistons n I hav a 50* vtc n I herd that i can adjust n set the 50* vtc to 30* thru kpro does anyone know about this n is this as safe as getting a modified vtc.......
 

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Yes, when you tune you set the cam angle maps to lock the cam to wherever you want it.

But this thread is about the +/- difference between whats on the map and what the VTC/Engine physically does.
 

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im gonna clay my motor to check clearences, but how do you know what max vtc is safe? do you need to keep taking your motor apart after claying it to see which is the max before vtc? do i need to have a 25, 30, 35,40, 45, & 50 degree vtc individually checked? like another member said, the difference from 30vtc to 40 vtc could be more power but how can you tell without wasting all your time? im confused?
 

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im gonna clay my motor to check clearences, but how do you know what max vtc is safe? do you need to keep taking your motor apart after claying it to see which is the max before vtc? do i need to have a 25, 30, 35,40, 45, & 50 degree vtc individually checked? like another member said, the difference from 30vtc to 40 vtc could be more power but how can you tell without wasting all your time? im confused?
I would start @50(if you have a 50 degree cam gear,if not then go as far as the cam gear will go) and check that way.If you don't have p2v contact @ max advance you won't have it less than max.
 

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I wanted to know about using 50* vtc Im gonna b using dc4 with 12.5 pistons n I hav a 50* vtc n I herd that i can adjust n set the 50* vtc to 30* thru kpro does anyone know about this n is this as safe as getting a modified vtc.......
Basically same setup as you are doing...I posted 2 above you. I ran a 50* gear on DC4 cams, limited to 32* on my cam table on K-pro. Never had an issue and drove it for ~3000 miles including countless dyno pulls and 1/4 mile passes. Motor looked perfect when pulled apart. Doing another very similar build very soon with some changes.


im gonna clay my motor to check clearences, but how do you know what max vtc is safe? do you need to keep taking your motor apart after claying it to see which is the max before vtc? do i need to have a 25, 30, 35,40, 45, & 50 degree vtc individually checked? like another member said, the difference from 30vtc to 40 vtc could be more power but how can you tell without wasting all your time? im confused?

I think there should be .080 inch clearance between valve and piston, that's your max VTC. Pretty sure that's the right clearance. There are other threads about it on here also. You don't have to clay the motor, just put it together, flip the rocker arm pins around on one cylinder or two so vtec is always locked then turn the piston to TDC and with a dial indicator push down on the valve (open it more) till the valve touches the piston. That will be your baseline for p2v clearance. Now I'm not 100% sure on this, but I have heard from others that you can skip the chain a tooth to simulate valve angle and continue measuring that way. I believe each tooth on the intake gear is 12.5* but am not 100% sure so please do not be mad if I'm wrong.:)
 
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