BCIII Cams installed, flat spot at VTEC STG 1. Tune???

[Super-DA9]

Hey everyone.

Just got a set of Buddyclub Spec III+ Cams, ITR B18C valve springs and new valve seals installed in my DC2 Vti-R.

Car idles fine, drives smoothly and VTEC still works, you can REALLY hear it at 6000 holy sh*t.

However there is a flat spot at the point when VTEC stage 1 is meant to kick in, the revs climb, a bit slower, but there's a drop off of power until you get to like 5500-6000 and then BAM, big hit of power an very soon after stage 2 VTEC engages and the power continues. also there's not much of a sound change at 4400RPM which is when stage 1 engages and also where this flat spot seems to begin.

It's only REALLY noticeable when your accelerating reasonable hard.

the only other difference I've noticed is that the engine is a fair bit more "tappy" sounding now, but I assume that'd be because of the stiffer ITR dual springs.

I figured the flat spot could be one or both of a couple of things.

1: car needs tune and VTEC engagement points adjusted slightly to suit the cams, which are basically Jap Spec ITR cams with improved duration and lift.

2: Vti-R intake manifold not letting enough air through to suit the lift/duration/timing of the cams until the dual butterflies open up.

I read this on honda-acura.com in response to a flat spot on crower stg 2 cams:

"Here's the problem with having stock primary lobes and larger VTEC lobes. By increasing the lift/duration of the VTEC lobes, you change the RPM range at which they're effective.

With your stock cams, the VTEC switchover is about close to the point where the primary lobes run out of power and the VTEC lobes will make more power. If you just change the VTEC lobes and keep the stock primary lobes and switchover point, there'll be a flat spot in the powerband before the fat part of the VTEC lobes comes on."

I'm wondering if this is the case with my setup right now running stock tune.

Thinking that maybe a VAFC would do for the time being until later in the year when I get a hondata and drive to TODA? Any comments on the VAFC?

ANY and ALL input will be greatly appreciated.

[mooshie]

Just being picky but there is no stage 1 and 2 VTEC. The VTEC crossover on your B18C2 is at 4400RPM and the secondary runners in the manifold open at about 6600RPM which is probably the 'holy shit' sound

The issue is that you have an ECU which is expecting VTEC to occur at the standard point but cams which are designed for it to happen at a different point therefore the tuning is all wrong for the cams. as the revs rise this difference gets smaller and that is when you get good power.

I thought that BC Spec 3's are designed to crossover at 5500RPM however this is not an area I have looked at much.

If you are intending on getting a Hondata then just do it now, dont waste money, remember that the tune costs about as much as the ECU itself most of the time.

[Super-DA9]

oh ok, i thought stage 1 was when the intake rockers locked together for slightly higher lift and stage 2 was runners + middle rocker engage. I guess it must only be the middle lobe, then runners. so that means there's no sound change at 5800-6000 in type R's then, or any VTEC motor without runners. i guess i learned something new today haha.

it's annoying cause I like can't hear the crossover at 4400 anymore lol...

yeah i figured it must be to do with the tune.

aw man i wish i could get a hondata + tune now, and I would if the nearest place wasn't in sydney and if i was ballin' enough lol. I've gotta get them to do my ITB's at the same time and I don't have all the little bits and pieces + ecu + $1400 + money for one or two nights accomodation in sydney yet... wish i did though haha.

thanks for your input.

i guess my next question is, will the vafc/safc neo work for tuning on this setup? it seems to be able to adjust the three things that I need to change: air, fuel, vtec engagement. i'm thinking it may be worth it for the next 6-8 months to keep her running perfectly if i can find a great deal on one, maybe second-hand.

[VTec1987]

you spent good money on cams man, get a hondata to tune it to get the best out of these cams

[Super-DA9]

yeah man for sure, i will definitely get a hondata, but i just can't right now, only because nowhere at all can tune it unless I go to sydney and I live in canberra. i would really like to avoid going to sydney twice for the same thing. i'm trying to figure out if theres a way to get just a temporary tune now to get the air/fuel and hopefully vtec to the right settings here in canberra until i get the money to go to sydney, stay there two days and pay TODA $1400+ for ITB install + performance tune.

i totally get what your saying and if worse comes to worse i'll just have to work my ASS off for a couple of months and try to bring the final tune closer but if possible i don't mind spending $500 or so to have her running nicely until then