Leaving vtec on for track car
02-15-2006, 06:06 PM
#11
1.0 BAR
Thread Starter
Join Date: Feb 2003
Posts: 214
Re: Leaving vtec on for track car
There would be no torque available with vtec down low. If you know a Honda, and why they created Vtec, It was to be able to get a High Rev, Top End engine to be drivable down in the lower rpm range, because not everybody want to run a motor up in the 5000+rpm points every time they take off.
No I didn't just drop Vtec down. I didn't hop on the Honda BandWagon yestarday. If you researched you'd find most people often raise thy're engagement point.
No I didn't just drop Vtec down. I didn't hop on the Honda BandWagon yestarday. If you researched you'd find most people often raise thy're engagement point.
Lol.."if i know honda and why they created vtec." Vtec was created because they wanted fuel economy down low and still be able to make some power at the top end by flowing more air. There engines are well balanced and designed to be able to flow air up top which helps with the fuel economy in the lower rpm.
You do relize that an engine is just virtually an air pump.. The more air you can flow the more power you can make. Lets take for an instance.. you could have 40lbs of pressure flowing like 1000cfms of air at 1k RPM. assuming you had the fuel and spark readily available for that air you could make close to the same Tq and HP as if you were at 40lbs of pressure and 1000cfms of air at 8000 RPMs.
That being said.. I have no clue why you would RAISE the vtec engagement on any boosted application other than your turbo spooling after your stock vtec point of roughly 5500rpm. If you can flow more air at a lower rpm due to turbo or whatever doing it i dont see why you wouldnt switch to the dam vtec lobe and flow it?
And i have been researching turbos and hondas for 7yrs now. Im not anexpert but i know my fair share. Im trying to make something with good power throughout the whole powerband.. and not some dyno queen or straight drag car thats got a tq curve steeper than the
tallest rollercoast. Know what i mean? Having a big *** turbo that isnt spooled until 6k rpm and when its spooling it jumps a couple hundred HP withing 2k rpm doesnt exactly work at a road coarse. The drag strip yes. But thats not what im going for.
I guess the information i am looking for is the mechanical aspect of vtec. or someone that has had a similar experience on a boosted app. or some tech info on why it wont work.. Not "If i know Honda"
Thanks
Brian
02-15-2006, 06:25 PM
#12
0.0 BAR
Join Date: May 2005
Posts: 0
Re: Leaving vtec on for track car
First the high cam (VTEC) is held by a constant supply of pressure answer that question. As far as messing up the LMA's, that wouldn't happen. All they do it is keep the high cam rocker arm in check while it is not engaged. You could however mess up the pins that lock in the high cam rocker arm, since with low oil pressure they would be right on the edge in the rocker arm hole and would get scuffed and all mangled up.
As for keeping only the high cam. It would be stupid not to want the low cam. Having two cams is very benificial for making a broad torque curve throughout the RPM range. Just because the high cam allows more flow, doesn't mean that it will make power down low. In fact allowing more flow when the engine doesn't need it will only decrease intake velocity thus reducing the actual amount of air flowing into the combustion chamber.
At low RPM's the low cam will always make more power than the high cam, always, turbo or not. It it designed for making power in that RPM range.
As for keeping only the high cam. It would be stupid not to want the low cam. Having two cams is very benificial for making a broad torque curve throughout the RPM range. Just because the high cam allows more flow, doesn't mean that it will make power down low. In fact allowing more flow when the engine doesn't need it will only decrease intake velocity thus reducing the actual amount of air flowing into the combustion chamber.
At low RPM's the low cam will always make more power than the high cam, always, turbo or not. It it designed for making power in that RPM range.
02-15-2006, 06:47 PM
#13
1.0 BAR
Thread Starter
Join Date: Feb 2003
Posts: 214
Re: Leaving vtec on for track car
I dont believe this at all.. MOST Drag cars dont have 2 cams to get more tq lower end. They run a HUGE cam in it.. say F*ck the idle and dump as much air and fuel in it as they can. Like i said im on the track i dont care about gas mileage.
How can you prove that flowing more air down low with vtec on wont help? It just doesnt make sense. an air pump is an air pump whether its going at 1000rpm or 10k rpm.
Ok that doesnt answer my question.
Constant supply comming from the engine going the vtec solenoid which switches the the cam over.. then does the soleniod close trapping the oil pressure in there holding the cam in. And the way you disengage is by tripping the valve to let the pressure out assuming your rpms are dropping along with the oil pressure? or does the soleniod open and stay open assuming that when you let off the gass your oil pressure is gonna drop and it just disengages itsself?
If its the case that the vtec soleniod traps the oil in there .. then if i keep voltage on the soleniod it shouldnt matter if drop engine oil pressure because the vtec soleniod trapped the 80psi or whatever psi in there to hold it.
Thanks
Brian
How can you prove that flowing more air down low with vtec on wont help? It just doesnt make sense. an air pump is an air pump whether its going at 1000rpm or 10k rpm.
First the high cam (VTEC) is held by a constant supply of pressure answer that question.
Constant supply comming from the engine going the vtec solenoid which switches the the cam over.. then does the soleniod close trapping the oil pressure in there holding the cam in. And the way you disengage is by tripping the valve to let the pressure out assuming your rpms are dropping along with the oil pressure? or does the soleniod open and stay open assuming that when you let off the gass your oil pressure is gonna drop and it just disengages itsself?
If its the case that the vtec soleniod traps the oil in there .. then if i keep voltage on the soleniod it shouldnt matter if drop engine oil pressure because the vtec soleniod trapped the 80psi or whatever psi in there to hold it.
Thanks
Brian
02-15-2006, 08:01 PM
#15
1.0 BAR
Thread Starter
Join Date: Feb 2003
Posts: 214
Re: Leaving vtec on for track car
see my theory is...when you start making boost.. if you switch to the vtec lobe youw ill notice a descent different in hp and tq down low, say your car starts 1psi at 3200rpm if you can open it at say 3150..or already have it engauged at idle.. from 3200 at 1psi to 4500rpm + a couple hundred for it to fully engage.. you will already be making alot more hp and tq down low and not have to worry about your vtec engauging durring your powerband.
I mean on my ls 1.8l with a big turbo i was only getting 90 ft/tq at 3000rpm @ 2 psi...I now have the lude 2.2l and with vtec engaged hoping to have 6-8psi @ 3000 rpm im looking for a good 150-200ft tq. Huge difference. Of course completely different cars and engines.. but.. you can see what i mean by comparison, and how it would be beneficial going around a hairpin turn thats got a slight uphill tilt to it.. Assuming i keep traction it will pull alot harder.
I mean on my ls 1.8l with a big turbo i was only getting 90 ft/tq at 3000rpm @ 2 psi...I now have the lude 2.2l and with vtec engaged hoping to have 6-8psi @ 3000 rpm im looking for a good 150-200ft tq. Huge difference. Of course completely different cars and engines.. but.. you can see what i mean by comparison, and how it would be beneficial going around a hairpin turn thats got a slight uphill tilt to it.. Assuming i keep traction it will pull alot harder.
02-15-2006, 08:08 PM
#17
1.0 BAR
Thread Starter
Join Date: Feb 2003
Posts: 214
Re: Leaving vtec on for track car
like i said.. i have the studder box enabled in the ecu.. but im going for road course not drag strip. click that summit point link and check out the courses.. there pretty good. Like 250 bucks for instructional course.. and 200 bucks for actual course time. It is really fun.. i seemed to like it rather then driving for 12.9sec down a straight course, Personal opinion tho. Its a nice present from parents on bday, and holidays and whenever i can save up.
02-15-2006, 08:42 PM
#18
1.5 BAR
Join Date: Nov 2005
Posts: 828
Re: Leaving vtec on for track car
uh ok, i have read through this entire page and am not sure what advantage your trying to gain by activating vtec continuously ( which is impossible because it won't engage under a certain oil pressure) but i would think that setting your vtec to engage like 2-500 rpm higher ( like when your turbo is at full boost) would be more beneficial.
Rather than trying to run low rpm on a cam thats lift and duration is designed for operation above 4000K, which will only add to the about of performance loss and turbo lag because like someone already said, just because your ports are open farther does not mean you are actually flowing enough air to make use of it.
basically without going into a long explanation on cam design and fluid dynamics, thats a bad idea and won't gain anything.
secondly, vtec was invented for a purpose and it's not like it takes 20 seconds to engage so whats the point of having it on all the time anyway?
Rather than trying to run low rpm on a cam thats lift and duration is designed for operation above 4000K, which will only add to the about of performance loss and turbo lag because like someone already said, just because your ports are open farther does not mean you are actually flowing enough air to make use of it.
basically without going into a long explanation on cam design and fluid dynamics, thats a bad idea and won't gain anything.
secondly, vtec was invented for a purpose and it's not like it takes 20 seconds to engage so whats the point of having it on all the time anyway?
02-15-2006, 08:52 PM
#19
1.5 BAR
Join Date: Dec 2005
Posts: 1,427
Re: Leaving vtec on for track car
Originally Posted by dastinker8
I dont believe this at all.. MOST Drag cars dont have 2 cams to get more tq lower end. They run a HUGE cam in it.. say F*ck the idle and dump as much air and fuel in it as they can. Like i said im on the track i dont care about gas mileage.
How can you prove that flowing more air down low with vtec on wont help? It just doesnt make sense. an air pump is an air pump whether its going at 1000rpm or 10k rpm.
How can you prove that flowing more air down low with vtec on wont help? It just doesnt make sense. an air pump is an air pump whether its going at 1000rpm or 10k rpm.
unless you build some kind of frankenstien motor i dont see how your going to get the power you want below that rpm range, an air pump running at 1K rpm is going to pump less air just because its going slower then the one at 10K, your power will always be up top, and if your driveing a road course i dont see where you'd be below 3K rpm anyway? even on a city street driveing a little quicker then i need to i stay above 3K almost all the time, i'd imagine on a competitive road course i'd be above 3K ALL the time..
the short answer to solve your problem, learn to drive and quit bein a -----!
my turbo isnt fully spooled untill 5K rpm and from what it sounds like, i could kick your *** on a road course the first time on it because you cant drive
also the turbo being at 2psi by 3K compared to 6-8psi is the entire power diffrence, just get a smaller turbo that fits your application instead of trying to butcher your motor for something that will probably prove useless anyway
