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hey people. i was told that honda have set vtec at the optimum position on each car. what i mean is if you lower the revs that vtec kicks in then it will hav a big effect on top end speed and obviously vise versa thus making you run a slower time in some cases. has honda got it perfect or what do people think. is vtec controller only good in highly moded hondas? :honda:
i personally think its a waste of money. there are plenty of otherways to mod your car
IME ... modifying the vtec engage point can add serious performace value to your car. I drive a DC5r with vtec modified to engage at 3100rpm under WOT, the torque is quite impressive compared to the mid-range torque of the stock ecu. Another difference is I have no noticable kick when vtec engages, only a very small change in sound pitch. My other engine modifications are only exhaust and intake
In my way of thinking, if there is a noticable difference in power output between 2 cam profiles when switchover occurs, then there is room to make a smoother, more linear switchover by adjusting the vtec engage point lower. Thus producing a more drivable car.
Aren't you running hondata davidd?? If so, you're tuning much more than just VTEC cross over and fuel correction to get your 'serious gains'.
In terms of performance, simply adjusting the VTEC crossover will not yield any extra performance. Like you heard, the factory has already optimised the VTEC point for a standard setup.
If you adjust air/fuel ratios and ignition timing as well however, then you can certainly improve on the factory setup. An Apexi VAFC allows you to adjust fuel along with the VTEC crossover, so tuning one 'properly' (not just VTEC point) can give good gains. I've heard B series engines gain around 10-15kw in the mid range just from a good VAFC dyno tune (and around 5-10kw up top). Would give you better bang than say a cat back exhaust IMO. Both would be around the 1k mark approx. But I dunno the VAFC(II) gains on K series.
Personally though I'd advise you save up for a full ECU tune. Due to the engine design, the K series has heaps of potential for you to unlock from the ECU.
Copy from another post... i replied to...
Changing the Vtec point on some engines both higher or lower can increase power by a very large factor, if you provide the correct fuel and ignition to support the early or late vtec change, and in the case of K engines cam angle as well.
Typically those if the car is almost fully stock there is no need to change the cross over point, slightly modified cars normally +- 400rpm or so from stock, and heavily modified car’s can vary heaps. This at least stands true for B H F and D engines. With the Honda K engine even stock form lowery the vtec point by 2000 or more RPM gives huge gains….. but once you make the engine breath better with a nice set of headers you increase the point from stock.. at the end of the day it all comes down to your car your modifications and the ability to how you can have your car tuned.
Regards James
interesting reads!
vtec controller can really $#%% up your engine in the long term. If you really want a vtec controller, save up abit more money to get the Apexi power FC. Follow the bang for buck if i was you.
Quote:
Originally Posted by thanh
ANY modification can severly feck up your engine in the short , mid and long term too - its more in the relevant tuning that can make or break any modified setup. :thumbsup:
i was told that if u adjust ur vtec to say cut in earlier... u gonna get a lag ...
like a turbo lag...
an educated guess - this happens , because only the CAM timing is altered and nothing else - so no extra fuel ,air or oil flow etc is availible at any rpm's below the stock vtec engage point. Adjust these to suit ( with a proper ECU etc) and the car should pull properly from any given "vteck" point :)Quote:
Originally Posted by |N|
*correct me if wrong* ! :thumbsup:
but isnt the power fc a power flow controller... i mean the vafc is for v-tec specifically ...
but i say that if you really want your v-tec to kick in efficiently without #$%^ing up your engine then to let the momentum up and wen you feel the need to let the cams change then to set it at that point..
i say to early no build up and top speed will be lost
too late and there will be no point of having the controller there in the first place ...
This thread is more technical, rather than Integra based.
*moved*
Vtec works on Rpm's and Oil pressure and a few other factor wich I cant remeber now. But I dont think its good to lower ur crossover point at all because all the oil pressure has not built up yet for the actuall vtec to engage properly.
As an answer to the original thread creators question, chnaging the vtec engagement alone, with no other tuning will have absoultly no effect what-so-ever on a cars "Top Speed" and "Max Power".
For instance if a car makes say 150Hp @ 7000 Rpm with 5500 Rpm VTEC crossover, if you change the VTEC engagment to say 3000 rpm, by the time it reaches 7000 rpm it will still be making 150Hp.
VTEC controlloer also has nothing to do with your gear ratios, final drive, or engine Rev Limit thus I can't see how it would affect your top speed.
-KB
For a stock unmodified car, the VTEC switchover point is optimum. If you alter your car by changing I/H/E, ECU or remapping the fuel maps, then the optimum point for VTEC switchover has changed. Only then will a VTEC controller be useful.
Oil pressure is maintained by the oil pump. Once your engine is warmed up, the oil pump will maintain oil pressure throughout the rev range. So you can engage the VTEC system at any point in the rev range. Of course, if you set your VTEC point too low, and your hi-lift cams are very aggressive, it means you are lugging your engine since not enough torque is preduced to increase the revs. Imagine doing this at WOT, not too healthy for your engine.