let's talk about VTEC here,...

[6766]

If the standard B series engine let say B16a, Vtec open at 5600 rpm,then we rechip or use Vafc to open the Vtec early than that ,let say 5000 rpm or 4800rpm , does this cause any harm to the engine or the Vtec system?

 

[shiroitenshi]

I won't try to guess the reason why, but decreasing vtec point isn't always the formula for power.. I can see why people think so..

"hey, when the vtec engages I feel the VTEC POWER yo!"

"so if I set it earlier, it should it earlier right?"

well, it is true to a point, like maybe 5200-5400, but 5000rpm is a bit stretching it.

 

[fobs]

i forgot i started this thread,... :hmmmm:

here's a scenario,...
my vtec engage 5.2k
when tuned with vafc,... the tuner put it at 4.8k,...

as i was informed,... honda made the vtec crossover for a reason,... that is : at that point, or maybe a bit lower than that (engineers always tend to have a safety range) ur engine produces top power,...

lets say two cars : same car model with same engine,... after a few years,... with wear and tear,... the engine will not be exactly the same,...

so, tuning wise,... u might tune one car to have vtec engage at 4.8k,... the other might be suitable to hv vtec open at stock 5.2k,... it all depends on that particular engine,...

as bro shiro stated,... if ur stock vtec crossover point is at 5.6,... u might have it set to abt 5.2-5.4,... coz 4.8 i think is way too low,... unless ur engine is in stage four modification,...

my engine only stage 0.5 (shiro,... winked) hahhaaaaaaaaa!!!

 

[shiroitenshi]

heh.. lol at stage 0.5 fobs.

anyway, if set it too early, there's the problem of having not enough oil pressure to engage the vtec. hondata recommends more than 3000rpm because of that possible issue.

as to what kind of damage it causes, I'm not sure.

people using hot cams like toda c's and such usually have the vtec point higher, not lower as some people may think.

 

[6766]

my stock engine open at 6300 rpm so i lower it at 5500rpm..i hear it open at 5500 rpm but i feel the vtec kick still at 6200-6300 rpm..i heard someone said that what i heard at 5500 rpm is the butterfly open...but still just a curiousity if im using standard part not like toda and other performance will it damage the engine or its better to leave the vtec point as it is ...cheers to all sifu :)

 

[6766]

As sifu Shiro stated "people using hot cams like toda c's and such usually have the vtec point higher".I think this is because their car can rev to higher rev very easy not like mine its a lil bit heavy so thats why i lower the Vtec point..

 

[fobs]

more important,... if ur powerband is smooth up,... meaning no vtec jump,... u get from point A to point B faster than when u feel the vtec 'kick',...

hahahaaa!!! my car no vtec kick liao,.... g force all da way!!!

 

[shiroitenshi]

Well, if you think you gain more power from earlier vtec point, then go for it.

The only concern you might have is that you don't have enough oil pressure to engage vtec, and your vtec will turn on intermittently, resulting in jerking.

I'm still unclear what damage if any that will result from that.

This is an excerpt from hondata SManager.

The VTEC window is a variable VTEC switch point based on engine speed and engine load. Usually you want the VTEC point to move higher with lighter engine load. The above screen shot shows VTEC switching at 5000 rpm when the manifold pressure is 5 inches vacuum or above (which is close to full throttle), reducing in a linear fashion at 6000 rpm to 15 inches manifold vacuum.

Do not set the VTEC switch point too low as there will be insufficient oil pressure for the rest of the engine. As a guide do not go below 2000 rpm.

Do not set the VTEC switch point too high as the high speed rocker arm will float on the lost motion spring and damage the valve train. As a guide do not set the VTEC point higher than 6500 rpm.

As you can see from the bold and underlined, opening it too early can result in less oil pressure for the REST of the engine, so that's a possible problem there.

That's a guide only, but usually tuners never set their vtec point past 5K mark, unless the car's stock vtec point is already low, at 5.2K, like fobs.

 

[fobs]

That's a guide only, but usually tuners never set their vtec point past 5K mark, unless the car's stock vtec point is already low, at 5.2K, like fobs.

hehe,... u mean below 5k,...

anyway,... i'm no tech master or expert,...
so these are juz what i see/hear

other fren of mine with h22aR manual,... vtec was at abt 5.5,... now set to 4.8 hi, 4.7 lo. with afc neo

another fren with f20b dohc,... vtec point remained the same at 5.3, with e-manage,...

 

[hattech-v]

kill the vtec... :)

 

[integram]

i had a spoon vtec controler in my b series n i realise lowerin da xover point below 5k leads to a slight power loss compared to 5.5k or 5.2k.....i hav disconected my controler n i feel da power gains r beta nw runin on stock xover point.....cheers n happy new year to all zth bros....