Ok Ive made a few try, 4400 and 4700 it still bogs, 5000k it engage alrigght.
I’de like to lower the VTEC engagement point to gain more powerband. IMO it could be done by retarding the exhaust valve, this way, it would open later and then will allow the vtec lobe to let air and maybe lower this point to 4400 like a GSR and hence not making the engine bog.
Am i mistaken, any opinions ?
I think could make for a very interesting discussion.
I think one factor involved is that at the lower rpms, it’s not moving enough air to compensate for the increase fuel that the ecu is dumping via the vtec map.
I remember when I got tuned with the Skunk2 Stage 2 cams, we had to shift the engagement point to from 5500 to 6100 rpms to get rid if the slight bogging and smooth out the power band.
Lets see hear what the experts have to say. A tuner’s input would be ideal.
Funny db2, I had to do the same thing with those cams… actually, I think I had it bumped up to 6600 rpms or so on a b16. Otherwise, I think you’re exactly right… there’s no guarantee that lowering it is the right move because it might not be flowing enough air at that RPM to match the fuel delivery. It’s best to make any VTEC changes on a dyno, where you can see the results. It’s pretty straightforward when you can see it on the screen… you basically have 2 torque curves, one for the low lobes and one for the high lobes. Imagine you dyno the two separately, as if they’re physically two different cams. Then you superimpose the two torque curves on each other and pick the point that makes the two curves into as fluid of a single curve as possible. It may be higher than stock, it may be lower than stock, it may be stock… it depends on a lot of factors.
steronz, you are exactly right as well with this statement.
"you basically have 2 torque curves, one for the low lobes and one for the high lobes. Imagine you dyno the two separately, as if they’re physically two different cams. Then you superimpose the two torque curves on each other and pick the point that makes the two curves into as fluid of a single curve as possible "
The tuner some how disabled the vtec system and made made several pulls while adjusting “things”, then he re-enabled the vtec system and continued tuning form there.
I think or best results for the engagement point was somewhere around 6300 and 6500, but he set it at 6100 stating that it should be a few hundred rpms before. Honestly…I love the fact that vtec engagement was that high… with the little increase in low and mid range power, I didn’t have to venture into the realm of vtec for everyday driving and the bonus was ~28mpg.
Ok guys you are talking about air flow. I think there is much more flow on our turbo cars than a NA car, which in that case would make it easier to lower the VTEC engagement. My setup is B18 base + B18C head, around 9.8:1 CP.
Stock GSR vtec point is 4400, i dont see why mine would be as high as 5000…
Tuner’s Point of view?
Hope this link help some to understand and for some follow up with it.
Scroll down to about halfway it explain about vtec points.
5800-6300 rpm would be much better and I hope one of the ranges works for you as every persons car act differently no matter what we do.
RiccyLSR, a tuner’s input, just like in the link you posted.
Very nice read, thanks.
weird to find a post here and vtec was a 4400 ( hit dyno xxxx 10 psi)
mine is fine around 5500