Adjusting vtec

[SRV BOY]

What do I need to get to make my vtec kick in at lower rpm, currently I have an h22 in a 95 prelude, and the vtec kicks in 5,000 rpm. To my knowledge there is a chip that you can buy for this. Any ideas?

[boosted331]

You don't need to adjust vtec on a stock car with stock cams, it will do nothing for your performance.

[SRV BOY]

I want to adjust my vtec to kick in it at lower rpm, it kicks in too late at 5,000rpm

[SiGNAL748]

5000rpm is not too late. Honda set it at 5000rpm for a good reason. Boosted331 is right. Just don't touch it.

[SRV BOY]

How will it not do anything for performance, when the vtec kicks in you get a boost and the car goes faster. The hp is rated usually at 5,000 which is when the vtec kicks in. If i get the vtec kick in earlier, I will get a boost earlier. I will get better start off the line. I've seen people do it and they say it doesnt hurt the engine in anyway.

[94tegRS]

you wont get a better start off the line, you arent at anywhere near 5k when you leave the line, and if you are on the vtec lobes at launch thats just more power to keep your tires spinning longer before they bite. and the boost isnt the same lower, actually if you lower it it wont really be a boost anymore, I have seen a dyno and they actually do benefit a bit from lowering the vtec engagement to I think down close to 4000 or so, it just smooths it out so there isnt that spike, so instead of flattening out and then climbing quickl;y all the sudden it is a smoother curve, no gain in power, just a bit more than usual between the new angagement point and the old engagement point. on this dyno I saw though they had also richened it out 5% which is where it ran the best. they didnt only change the engagement point, they said it was cuz on the H22 they had to set the VTEC late to be able to import that engine to the US for emissions or something, dont quote me on it though. get an APEXi VAFC and you can control fuel and VTEC.

[88_SC_CRX_Si]

VTEC depends on the intake speed, rather then activation point. The air is not moving fast enough through the system yet, in the lower rpm ranges to take advantage of it.

Most cases they are dailing out some of the overlap VTEC uses, between the intake & exhaust valves, when adjusting the cams.

[94tegRS]

well, yeha I see people do that too, but I saw the dyno of a prelude VTEC where they richened it a bit and lowered the vtec engagement point a bit. either they staged the plots and did more than they said but only revealed the vtec/fuel adjustemnts or what, but I saw it, ont saying it would/should work with every honda. and the engine draws its air in so if the airbox was restrictive enough so it couldnt get the air it wants down at 4-5k, the engine would never make it to 7k. on a dyno the car isnt moving (you do have that fan but...) and it pulls strong to redline...

[88_SC_CRX_Si]

Originally Posted by 94tegRS

well, yeha I see people do that too, but I saw the dyno of a prelude VTEC where they richened it a bit and lowered the vtec engagement point a bit. either they staged the plots and did more than they said but only revealed the vtec/fuel adjustemnts or what, but I saw it, ont saying it would/should work with every honda. and the engine draws its air in so if the airbox was restrictive enough so it couldnt get the air it wants down at 4-5k, the engine would never make it to 7k. on a dyno the car isnt moving (you do have that fan but...) and it pulls strong to redline...

Just how much is a "bit"...

Granted, you can lower the point a few hundred rpm at the most. Butttt most peeps won't to drop it "way" too low. Honda chose that point for the best fuel milage, rather the performance.

One of the peeps on the "Resource" has noticed when dynoing the SOHC Z6 can have it's activation point lowered from 4800rpm to 4500 at the very most. Whereas the Y8 is best left OEM at 5200 rpm, however there will be differances between cars, because no two are the same.

[94tegRS]

it was just 5% as i remember

[eswaroop]

The VTEC cams are designed to have a profile which boosts torque at higher rpms only. If you switch to the VTEC cam at a lower rpm, your power will go down.

check this link out.

http://members.cox.net/revlimit/vtec.html

[94tegRS]

the low lobes on the cam dont have to be that moderate though, it is for good gas milage and good hgih end HP, not good low end AND good high end. up in the rpms that are getting close ot the crosover, it can use a higher lift.

maybe not on all cars, but on the RSX,, when you get the hondata reflash program, it lowers the actual crossover about 600 rpms. so it wont always hurt the car.

[jcrx]

MY vtec is set for lo--> hi at 5400 and hi --> lo at 4800, my stock setting was 5800 engage and 5600 disengage. I gained about 7whp with a littel more fuel through out the rpm range. Not using a wideband o2 to assure stoiac conidtions, just to be safe.

Point is, just lowering your vtec point doesn't mean you will get more power, as a matter of fact you can lose power by bogging, or starving the motor. You have to do it in conjunction with your mods, and it has to be a monitored process. You can easiy send your engine in cardiac arrest if you mess with the systems too much and not know what you are oing.

[civicHBsi91]

what a fag, he calls everyone n00bs and thinks he so great when he posts about his "prelude with h22 with vtec!! yo"

kid you think your all badass in one forum but move to another and ask a dumbass question, get a life

if anyone thinks im being harsh go read some of the posts by him in the street/track racing stories, he thinks he is a god of some sort there

[Ricochet]

The point's pretty much been nailed on the head, if you lower vtec engagement on a stock engine you'll actually lose power. To answer the question though, a simple vtec controller or VAFC will be able to adjust it.