Hondata

Just started the motor last night. This motor has 12.5cr with very large pri and sec lobes almost similar to killer vtec cams. The exhaust centerline has been set to 107degrees.

I could get the motor to idle at 850rpms with the usual killer vtec blurp.
But it's idling at the 7 to 8 column range. Initially the AFR from the LM1 was rich at 11.5 so with the live tuning map enabled, i reduced that part of the map down to about 14.3 and the AFR readings fluctuates from 14.3 to 15.2.

As i raised the idle speed to 1300rpm with live tuning, it slowly raised idle speed to about 1200rpm. Any higher settings does not raise the idle speed further. But at 1200rpm, its idling at the 6 to 7 columns.

At that point, i tried to change VTC timing which is set at 0 degrees to 5 and 10 to see if it makes any difference. But the CAMCMD does not change. It stays at 0 degrees. CAM angle is also 0 degrees in the datalog.

Does the ecu respond to VTC changes in the idle ranges? As i revved up, the CAMCMD does advance accordingly but not in the 1000 to maybe 3000rpm range. It only registers cam advance in the upper rpm range.

In the end, the motor idles happy at 1200rpm but after revving up, it will bog down to the 500rpm range at columns 8 to 9 and shuts off. I tried to increase the ignition timing in those areas to help bump up the engine speed, but the datalog shows the Ignition timing around 13degrees despite my inputs of about 18 to 20 degree.

What can i do to make it idle properly?

For large overlap cams, my understanding is to keep the cams at 0 to reduce the overlap, but this means alot of compression is lost due to the late closing of the inlet cams and reversion will happen. Should it be set to idle at more intake advance to reduce the reversion ( but increasing more overlap?)

2nd.) Would it help to advance the exhaust cams to around 112 degrees or more? This will reduce intake exhaust overlap.

Any help is fully appreciated!

VTC always returns to 0 when the throttle is released / at low rpm.

The critical thing is how much manifold vacuum you have, which doesn't sound very much at the moment. I would tune the lobe centerlines for best idle vacuum and then use the VTC to tune for max power.

Hondata wrote:VTC always returns to 0 when the throttle is released / at low rpm.

The critical thing is how much manifold vacuum you have, which doesn't sound very much at the moment. I would tune the lobe centerlines for best idle vacuum and then use the VTC to tune for max power.

I think the low manifold vacuum is due to the late closing of the inlet valves which causes reversion of the intake charge back up the valves.
is it possible to set the VTC to 10 or 20 degrees during idle? I did try that with the low cam set on live tuning and changing the numbers but CAM CMD did not respond to my inputs.

Can i adjust ignition timing at the idle area? I remember reading somewhere that flashpro uses ignition timing to adjust idle speed so its fixed at 13 degrees?

I advanced the exhaust by 2 cam degrees and the motor is idling fine. Its the overlap thats the problem.

A few blips on the throttle will send the rpms going down to the 500rpm range while the motor struggles to rev back up to 1000rpm idle. What can i do to help bump up the rpm?

I can't adjust the ignition timing around the idle area since the flashpro controls the idle via ignition timing. Its locked around 13degrees at about 1200rpms.
At 500rpm its about 0 to 5degrees.

Any strategies for this situation?