Vtec Controller

[BSRacer]

Welllll,
I've bought a ef8 CRX SiR, it's still in Japan and arrives here in Jan. I've already started buying performance goodies on ebay (Sad I know, but it seemed like a bargain). I got a R-Spec Vtec controller (VTC82X) for like AU$130 shipped. Anyways I know vtec normally comes on at about 5500rpm, whats the optimal for speedy launches and general thrashing???

[z3lda]

how much it cost you for the rex inc. on road cost and everything ready to rock n roll, if u dont mind me asking

[BSRacer]

$8400 landed and fully complied, rego comes on top of that. it's got 120,000ks and is stock except for wheels. I'm pretty pleased.

[NEWKON]

Welllll,
I've bought a ef8 CRX SiR, it's still in Japan and arrives here in Jan. I've already started buying performance goodies on ebay (Sad I know, but it seemed like a bargain). I got a R-Spec Vtec controller (VTC82X) for like AU$130 shipped. Anyways I know vtec normally comes on at about 5500rpm, whats the optimal for speedy launches and general thrashing???

Hi there,

the optimum point really depends on what modifications you've done to your car. Some modifications require you to raise the vtec point in order to achieve the smoothest power curve, whereas others require you to lower the vtec point.

For the most though, it usually tends to be around the 4500-5000rpm mark :)

[VTEChnique]

Hi there,

For the most though, it usually tends to be around the 4500-5000rpm mark :)

I STRONGLY Dissagree !!!!!!!!

Honda puts the switch point on B16A's at 5500 for a REASON !!

BUT if you want to play, as said on here about 47 times now, set VTEC to 7000 RPM.. dyno it.. then set it to 1000RPM.. dyno it.. this way you get a graph for the non-vtec cam-lobes then also the vtec cam-lobes.. overlay the 2 graphs and where they intersect, is the OPTIMUM place to swith into VTEC.

now remember you ultimately want a linear power curve.. not flat then witha big crazy spike when VTEC comes in, nor do you want to be making no power at low RPM and then VTEC switches and you cant notice anything but your fuel gauge going down.

even with a modified engine, more likely than not you'd be extending your redline, therefore to get a more linear power curve, you'd be moving VTEC up in the RPM range. A friend of mine is making over 150+HP at the treads on his tired B18C just running MOTEC and intake and exhaust.. his VTEC is at 6300-6500RPM and believe me it CHOPS !!! M y old SOHC VTEC was peaqking and I was reaching for the shifter just as his VTEC was kicking in !!!

Having said THAT, there IS however an advantage to a VTEC controller. the switch-OFF point is programable on SOME VTEC controllers.. it may switch ON to VTEC at 5500RPM, then not OFF untill 4500RPM.. this has potential advantages in say exiting corners etc..

[NEWKON]

Hi there,

as mentioned in my post above, on some vehicles, it does require the vtec point to be raised.

Ultimately though, this is determined by the modifications done to the car. You won't believe how much difference simple modifications such as I/H/E will do to your air/fuel ratio.

From all the Honda's that we've setup on the dynapack, around 80% of them required the VTEC point to be lowered, not raised. The ones where we found they had to be raised were on those using CAI's. We've never had to raise the vtec point to over 6500rpm though. Doing so is silly, as the low/mid lobes simply do not make more power over 6000rpm.

On a stock car, if you've remapped the ecu (either piggyback or replacement), the optimum point is around the 4500-5000rpm range. This is what gives the smoothest (i.e straightest) power curve.

The reason why Honda set the vtec point so high is so that its customers are able to feel a more pronounced vtec kick, and also for economy reasons. This comes straight from Honda's mouth ;)

The only reason to lower the vtec point to below 4000rpm though is if you are going turbo. Lowering the vtec point too low on an N/A car results in the engine not getting enough air pressure, hence the car feeling flat. This is not a problem on a vehicle with a small, quick spooling turbo :)

This is just my own thoughts though, no harm intended :D

[VTEChnique]

Desmond, NOT having a go at you or anything - obviously you've had a lot more experience with this than I have, but I still cannot agree that VTEC at such low RPM is a good thing. There is always an exception to the rule, but from MY experience the VTEC point is very well optimised from factory. +/- Fuel Maps can be altered to get some big gains, but to be completely honest, the VTEC point stays the same.

do you have any dyno charts of your tuning before and after ??? would be interesting thing to add to this discussion.

As for the B18C with VTEC at 6300-6500ish (tacho may be out a bit..) it IS making very good power the whole RPM range but the VTEC is VERY strong. and pulls right to and through 9000RPM..

[NEWKON]

I'll see what I can do about getting our customers graphs up :)

What Intake/Exhaust was your friends B18C running? We've found that with several exhausts (Spoon in particular), the high-rpm characteristics is so good that to get the maximum out of your engine, you have to raise the limiter by 500rpm - thats on a stock B18C.

[BSRacer]

Hmmmm, Interesting, I had heard lowering to about 4500 would be best, anyhoo we'll see. Thanks guys.

[dundas]

i set my accord with basic mods to 4700.. you can feel it kick in and its good- ^_^

[KB]

The reason why Honda set the vtec point so high is so that its customers are able to feel a more pronounced vtec kick, and also for economy reasons. This comes straight from Honda's mouth.Hey just out of interest on my SOHC VTEC D16y8, VTEC engages at 5600RPM, (Redline at 7000RPM). My power curve is extremly linear. There is no "Kick". And I can't feel the low-cam start to die out before VTEC engages. Seems it is set a relativly good position.

But that could be because it is a SOHC :p.

[NEWKON]

The "Small VTEC", as we like to call it, is more for economy than performance thus you won't feel the big kick as you do with the "Big VTEC" models ;)

[KB]

The only reason to lower the vtec point to below 4000rpm though is if you are going turbo.But I thought the point of VTEC is to creat an overlap, meaning that both valves can be open at the same time. So when intake comes in, It pushes some exhaust out and vice versa exhaust going out sucks some air in.

So I thought that If you have a turbo, then when VTEC engages the turbo blows air strait through during overlap. Thus people with DOHC VTEC car's usually use cam gears to overcome this.

Or maybe I could be wrong? :p
Can someone correct me? Im altually quite interested.

-KB

[civiceg9]

ask Hondata to answer your question. I think he would know best ;)