adjustable exhaust cam gear & how it affects K-pro setti

[6spd_ek]

I need all the information I can get on this... as I believe it can affect ACTUAL vtc & spark compare to what the ECU/K-pro thinks

how it affects it & how much it affects it would be great 8)

lol - I am starting to realize how little I know about this motor & K-pro

[Hondata]

Ignition and fuel timing is determined from the crank sensor.

The intake VTC angle is relative to the exhaust cam. Changing the exhaust cam will change the intake cam by the same amount.

Looking your other post to do with cam phase errors, what problem are you seeing?

[6spd_ek]

well the other issue is I think I may not be timed properly (cam install error - links that corresponded to OE cam gear lines were never marked - BEFORE cams were removed)... my timing marks (horizontal) line up exactly @ TDC when i think they should not

if you could post a picture of how vertical marks line up with #5 cam cap that would be great (in other thread)

if you have email I could show you some things - mine is adkr27@yahoo.com


back to exh gear - if I have it retarded 2 degrees & VTC set at 45, VTC is really 43 (but will read datalogging 45) & thats it, thats the only thing affected?

[chunky]

Ignition and fuel timing is determined from the crank sensor.

The intake VTC angle is relative to the exhaust cam. Changing the exhaust cam will change the intake cam by the same amount.

Looking your other post to do with cam phase errors, what problem are you seeing?

Can you clarify the statement in bold a bit more?

What you've said implies that with a retarded exhaust cam gear, the intake would be accordingly advanced to maintain the "expected" separation between the intake and exhaust.

[Hondata]

VTC works by comparing the intake to exhaust cam sensors. eg 25 degrees intake cam advance means that the ECU will move the intake cam until the intake cam sensor shows it is 25 degrees ahead of the exhaust cam. If the exhaust is rotated, then the ECU will adjust the intake cam by the same amount, notwithstanding mechanical limits.

[chunky]

VTC works by comparing the intake to exhaust cam sensors. eg 25 degrees intake cam advance means that the ECU will move the intake cam until the intake cam sensor shows it is 25 degrees ahead of the exhaust cam. If the exhaust is rotated, then the ECU will adjust the intake cam by the same amount, notwithstanding mechanical limits.

How does the ECU determine the "native" position of the cams? Is it solely from the pulse plates?

For example, I have the skunk2 stage II cams installed in my car with their adjustable exhaust cam gear. They recommend that the exhaust gear be set to -5 marks which translates into 20 crank degrees of retard. When the car starts up, does the ECU detect the the "new" orientation of the cams and make all adjustments relative to that? Or, does the ECU detect that the cams are 20degrees (crank) closer together and advance the intake cam to "real" 20degrees when the CAMCMD is 0 and showing the CAM as 0 also?

If the latter is the case, then the travel of the intake cam gear has an effective range of 30deg (20deg-50deg) while utilizing only the 00deg-30deg maps.

I would think that if the latter was the case, any attempts to use the 40deg or 50deg maps would result in an error since the intake cam would not be able to advance beyond it's mechanical limit. When I ran the car with the gear retarded all the way, the ECU showed that it advanced the cam 40deg and was using the 40deg map - something that would not seem to be possible if the latter scenario above was true.

If the latter scenario is true, could the issue be solved by widening and then shimming the keyway for the exhaust cam pulse plate?

Thanks in advance. :)

[Hondata]

If you retarded the exhaust cam 20 crank degrees then the ECU would generate a cam phase error. If the error was disabled (which, by the way, is something which should never be done) then the ECU would probably run the cam positions from an error recovery table - I'm not sure of what offset the intake cam would assume without testing it.

[chunky]

If you retarded the exhaust cam 20 crank degrees then the ECU would generate a cam phase error. If the error was disabled (which, by the way, is something which should never be done) then the ECU would probably run the cam positions from an error recovery table - I'm not sure of what offset the intake cam would assume without testing it.

Interesting. I have run the exhaust cam retarded 10 crank degrees for over 1000 miles with no error codes thrown. I've also run the exhaust cam retarded 20 crank degrees for a few days and few hundred miles with no error codes thrown. The cam phase error was not disabled in the .kal. The ECU also appeared to have no issues with a 40deg advance in the .kal showing 40deg for both CAM and CAMCMD.

Anyhow, this issue is of particular importance to me because my engine has less than .015" of v2p at 50deg advance. Technically, things should not touch, but the knock count goes crazy when the cam advances to 50deg, so I limit the cam angle to 40deg via the ECU. This is with no advance/retard on the exhaust cam. By the logic you have set forth, if I retarded the exhaust cam by 10deg crank, the intake cam would advance to a real cam angle of 50deg while showing 40 in the ECU.

When I retarded the exhaust cam 10deg and 20deg, I never saw the knocks that would typically accompany a 50deg advance on my motor (I don't have a modified cam gear at present to stop the cam gear from hitting 50deg).

I'd like to find out more about this situation. My experience tells me that the ECU is unaffected by exhaust cam retard - perhaps by re-calibrating the relative TDC signal from the intake and exhaust pulse plates at startup and then (via the CAMCMD spike) advancing the cam to 50deg and seeing if the system can advance 50deg from the baseline phase gap.

Of course, that's all conjecture. Do you have any suggestions on how I might go about measuring the actual intake cam angle while the engine is running? Possibly by capturing the cam position sensor data?

[Hondata]

With non stock cams to determine the actual position of the cams you need to use a degree wheel on the sensor end - not easy to do.

You're hitting the pistons with the valves. 0.015" is far too little - there is 0.030" stretch in the rod at high rpm, and the piston can rock around too.

[chunky]

With non stock cams to determine the actual position of the cams you need to use a degree wheel on the sensor end - not easy to do.

You're hitting the pistons with the valves. 0.015" is far too little - there is 0.030" stretch in the rod at high rpm, and the piston can rock around too.

Yeah, I know that .015" is too little. Even at a 3000rpm VTEC, I'd get the insane kcount. I replaced the valves while the head was apart for other reasons. I only attempted 50deg on the dyno for a total of 4 pulls that were aborted as soon as VTEC hit. No real damage was seen in the motor when I replaced the valves.

I noticed while I was putting the cams back in last night, only the exhaust cam pulse plate has a TDC indicator (a double bump occurs on the pulse plate at TDC). The intake cam doesn't have this. So the ECU can only know if the exhaust cam is at TDC.

As far as knowing the position of the cams, I was thinking that maybe capturing the raw sensor data and then analyzing it might allow me to see what the VTC system is doing.

Thanks for your responses!

[6spd_ek]

Anyhow, this issue is of particular importance to me because my engine has less than .015" of v2p at 50deg advance. Technically, things should not touch, but the knock count goes crazy when the cam advances to 50deg, so I limit the cam angle to 40deg via the ECU. This is with no advance/retard on the exhaust cam. By the logic you have set forth, if I retarded the exhaust cam by 10deg crank, the intake cam would advance to a real cam angle of 50deg while showing 40 in the ECU.

for some reson I was thinking the opposite... I thought if you retarded the exh cam you are actually retarding the intake cam... ie exh cam is at -5 with intake set at 40 vtc (in the ECU) you are really at 35

vtc will locate the the intake cam in relation to the exh. cam - don't forget when you retard the exh cam you are retarding the exh cam pulse plate - & any VTC advance is on the retarding exh cam pulse plate

maybe if doug or derek see this they can tell us which bold statement is true

chunky i think your clearances are tight enough... but explains how you ran 40 vtc when exh cam was retarded -10 degrees or more - your actual VTC was 30 (or less if you went more than -10 deg on exh cam)

[chunky]

Anyhow, this issue is of particular importance to me because my engine has less than .015" of v2p at 50deg advance. Technically, things should not touch, but the knock count goes crazy when the cam advances to 50deg, so I limit the cam angle to 40deg via the ECU. This is with no advance/retard on the exhaust cam. By the logic you have set forth, if I retarded the exhaust cam by 10deg crank, the intake cam would advance to a real cam angle of 50deg while showing 40 in the ECU.

for some reson I was thinking the opposite... I thought if you retarded the exh cam you are actually retarding the intake cam... ie exh cam is at -5 with intake set at 40 you are really at 35

vtc will locate the the intake cam in relation to the exh. cam - don't forget when you retard the exh cam you are retarding the exh cam pulse plate - & any VTC advance is on the retarding exh cam pulse plate

maybe if doug or derek see this they can tell us which bold statement is true

On second thought, I think you are correct. The intake would need to be retarded to dial out the overlap created by retarding the exhaust.