dastinker8

wow obviously you didnt read this page. Like i said before.. Using a bigger cam and forcing more air down in the lower RPM range should yeild more power... yes i agree engagin vtec at a low rpm where the engine cant flow the air because its NA is a bad idea.. just as everyone else has stated i am stating again. I AM BOOSTING.. FULL BOOST AT 3000RPM. Meaning when my engine is turning at 3000rpm i have 8psi ready to be shoved through my intake ports, and when since the vtec lobe is open longer i can put more air in there cause i have pressure ready to go. Just as if you put cams in your car at lower rpms youll have higher hp and tq number if you your system can flow the air.

Im trying to figure out how to keep vtec open or engauged all the time. From what ive been reading there is a spring at the other end of the cam that pushes back when the spring force > oil pressure it switches the cam back. I still havent been able to locate weather the solenoid that engauges the cam keeps the pressure in there or whether it is always open. I see in uberdata you can set when your vtec disengauges... so u would think it keeps the pressure in the system and isnt dependant on the engine oil pressure after it has been engauged. In that case i could set that number to 1 RPM.. then when i start the car engauge vtec it wont ever disenguage.. I just wanna make sure it works that way tho.

Tom-Guy

Yep, at about the same time your bearings dis-engaged from your bottom end.

*sigh*

I told you how to rig VTEC so it was constant, if it were easier to just engage it when there's oil pressure don't you think I'd have told you?


Which has nothing to do with VTEC, and everything to do with turbo.

There was a link to some DIY boost controllers a minute back, they had one that would control wastegate so that boost pressure reflected throttle angle. It's still not a truly linear power curve, but allows for a large degree of controllability. If you want to be a road track boostard, then look into it.

dastinker8

ok obviously you either didnt read how i said the engine worked, or you dont know how an engine works.. At 1k flowing 1000cfm and same fuel will yield the same results at 10krpm flowing 1000cfms. I have confirmed most of this info with my buddy whos a mechanical and aerospace enginneer. He told keep it in vtec and youll get more power as long as you can flow the air and supply the fuel.


So i guess now im just looking for how to keep the vtec engaged all the time.

Dr.Boost

Why not get one of those VTEC eliminator thingy mabobbers? :1
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Tom-Guy

No, it doesn't work that way. Lazy ports != fuel economy... and that's what B-VTEC heads have when tooling around town; lazy ports. Hell, they are so hogged out from the factory that they ------- suck as NA heads unless you're going to push more than 180+ whp, otherwise you stay straight LS. Just because the factory had to fangle things that way in order to meet emissions and a bunch of other horseshit has no bearing on how an optimised setup actually performs.

The simple explaination you've been offered about VTEC has about as much bearing on what is actually going on as telling a child that the engineering textbook you're reading is like their Dick and Jane reading primer, just with less pictures.




Yes, no, and on second thought let's turn my first yes into a no for practical applications.

Engines behave dynamically, and at 1000 rpms vs 8000 rpms your pistons speeds vs flow vs combustion speeds vs thermal transfer vs crank angle vs a bunch of other ---- are going to be all sorts of fucked, with any available camshaft you can name. That's your practical application "no."

As for making the same hp/tq at 1000 rpm vs 8000 rpm off of the same airmass... heh. You do realize that horseshit numbers are a function of the almighty torque @ whatever rpm you are measuring at?



On the up side. You're a bright guy, you're thinking, you're playing with ideas. Get some books on engine theory, flow, head porting, etc. The commonly available ones you find in the bookstore that are centered around the V8 stuffs are awesome. Cut your teeth on those. Post what you're thinking, I'm more than happy to offer perspective. I'm just not going to pick through... everything here... and try to patch a sinking ship. Sorry for that dismal metaphor, but it applies :P




PS - Oh, yeah, and engine is not an air pump. It's an open cycle reciprocating steam engine, driven by the expansion of water vapor created during the combustion reaction. Don't listen to the hot air heat guys telling you a bunch of hot air (literally!) pushes the piston down. Monitoring pressure rise over time in a bomb for equivalent stochiochemic between two known fuels with a more-or-less known chain of combustion, say, isooctane and methanol, shows the fuel that converts to water vapor first (methanol) building pressure substantially sooner - compared to isooctane, where the combustion reaction is 85% complete before 11% of total pressure is built. See where I'm going with this? It's ALWAYS more complex than you think.

signorelli21

omfg , what i was talking about in regards to cam design and not running a high progile cam at low rpm is because if you have a high lift, high duration cam at low rpm, you have what is called overlap. this is where both your intake and exhaust valves are open at the same time, so if your running 8psi at 3k and you have 30deg of overlap (or whatever) then you will end up pushing most of your boost pressure out the exhaust. this is not an issue at higher rpm because the intake/exaust velocity actually helps air fill and exit the cylinders.


i also just discovered that there is a site called www.meetblackpeople.com
why the hell isn't that considered racist?

Tom-Guy

Can I offer a practical applications "no" for that? :P

If you are boosting, save for specific high rpm high boost situations where bmep drops off and system dynamics get really pimpy like you were a NA ride which has nothing to do with this explaination so I'm going to insert a comma now and get on with my point, you have a lot more exhaust pressure than intake pressure... how are you going to cause blowthrough in a situation like that?

If you are using a commonly available turbo (something already commonly used on a Honduh), we can equate specific output to airmass ingested... and it's going to take the same amount of power output to spool a turbo, which you aren't going to get if all your intake charge is wasted. To make a crude comparison, two identical engines save for one has more duration and less LSA so there is blow through, you are going to have to make, say, 75 hp to spool a .57 trim T3/T04E w/ .63 AR stage 3 turbine. Which isn't going to happen if all your intake airmass is wasted with blowthrough... you quite simply wouldn't spool if it were such an issue, not without jacking around on turbine sizing.

Now, I'm going to turn right around and contradict what I just typed. I can do this; I am vast, I contain multitudes. Besides, like I said in my last post, it is ALWAYS more complicated:

Not all of this power comes from the spent exhaust leaving the combustion chamber - some of it could be coming from (carefully engineered!) blow through. Blow through, and cam overlap, and shorter than popular in the domestic world LSA (116 or greater? Meant for low revving high bmep engines, not small high winding 4 cyl.), etc, are all GOOD things. The first puff of intake charge strokes up against a superhot intake valve, which in turn superheats the initial intake charge. Awesome! We've just pushed a little more thermal mass into our combustion chamber and lowered our knock limit and safety limit. Vizard found the equivalent of two points of octane rating from ceramic coating intake valves *alone*, can you guess why?

So, the all-around best thing we can do is blow that ---- right out the exhaust. Doing this further serves us in two ways, which are linked together in a chain:

1) While the initial intake charge is "superhot" compared to what IAT readings would suggest, it is still substantially cooler than the single hottest part in the infernal combustion engine... the part that takes the biggest thermal buttraping and is expected to like it... the exhaust valve. More heat passes to our soon-to-be ex-intake charge, as it cools the exhaust valve while exiting stage left.

2) Ever hear the term "afterburn"? It's easy to induce with a little ignition retard right @ the point of greatest blow through. If we are savvy, we engineer the blow through to match the point at which the turbo needs to come alive. Now we have created a high pressure situation in the manifold that goes to spool the turbo, where that pressure would otherwise be wasted pressing the piston downward. Bah! In an off-boost situation, what good is that?

And that's the short explaination, ignoring a lot of stuff.

dastinker8

Ok Joseph Davis can you tell me what you think would happen since you seem knowledgable with the honda engine .
Its an H22a1. Lets say i replaced the intake cam and took off vtec, however the new cam i had,has the exact same size. lift duration as the vtec lobe.
1. How well would it idle?
2. If you had to compare Tq number from a stock h22a1 vs the tq number of the h22a1 with the new vtec cam as described above which one would be higher?
3. If you had to compare tq numbers from the engine at 3000rpm @ 8psi on the stock h22a1 low cam vs.. 3000rpm @ 8psi on the h22a1 that had that cam with the vtec sized lobe.
4. Do you think there would be blowbye on the setup using nothing but the vtec lobe, and how bad would it affect it.

5. Do you know how the soleniod works to where it either traps the pressure in and is released by the ecu or whether it stays open and when the pressure drops it disengages vtec by the loss of oil pressure


Heres my theory on how vtec works.
Pressure builds up at the soleniod. The ecu reads the engine pressure and if its high enough at the number marked in the ecu it opens the soleniod for a set amount of time and then shuts, keeping the pressure inside. When the rpm drops and it reaches the disengage number set in the ecu. the soleniod opens again and the spring helps squirt the oil out disengaging vtec also checking to make sure the oil pressure inside the engine has dropped. This makes the most sense otherwise the cam would be slidding around depending on the pressure inside the engine. Make sense? What do you think.



Thanks Brian

Tom-Guy

1) Never done it to an H22, but I had a hand in ghetto-rigging a kid's B16A1 w/ GSR cams. The guy was too damn cheap to buy a KS so he could have OMG JDM VTEC, but he had no problem slapping a Volvo WOT switch onto his TB to activate VTEC whenever he floored the gas. When he clicked it at idle (low oil pressure, damaged pins/high cam rocker arms not LMAs thnx for the correction earlier) the idle got a little lumpy, like a mild cam, but not enough to cause the engine to stall or need a higher idle. Your results should be similar, at worst case ou'd have to up idle to 1000 rpms *shrug*.

2) Since peak torque occurs in VTEC on most of the Honduhs I see stock dyno charts for, your peak value and position is going to be unchanged whether or not you disable the low cam.

3) I dunno, only ridden in one boosted H22. I know that VTEC helps spool when you bring it in a little early, but at what point that occurs on an H22 I do not know. If the built H22 I've been supposed to tune "next week" for the last two months were ready, I might have a good answer for you. Worrying about actual power at 3000 rpms, I don't think it matters that much.

4) Blowby is different from blow through. :P All blowby is bad. For a stock cammed Honduh, you'll get nothing but good out of the high cam and what blowby it has. There is a reason a lot of Honduhs run mild NA cams + boost, works great. The Web cams for my LS have 25 extra degrees duration over stock, and cam gears at 0,0 I have a touch more LSA but still more overlap than stock... not to mention a ---- ton of lift.

5) The solenoid doesn't trap pressure, it *provides* pressure. Oil doesn't go to the pins that lock the rocker arms until it switches on. It's not going to keep pressure from falling off, since it provides system pressure. As far as the pin-lock system being leak free if you could fangle something to act as a "plug"... the fact oil pressure falls off ~20 psi upon VTEC engagement lets you know that it isn't leak free. Pull out the rocker shafts, flip the pins in the arms, that is the only way to do it. That's how the VTEC killer setups work.

As for how VTEC works:

- You hit RPM @ load that tells the ECU to trigger VTEC.
- ECU sends 12v power to the VTEC solenoid, simultaneously switching fuel/ignition maps
- ECU checks for VTEC pressure switch close, letting the ECU know there is sufficient oil pressure
- If not enough pressure, ECU gives up clicks CEL
- If plenty of pressure, ECU continues to feed 12V to the solenoid as long as there is RPM @ load and oil pressure.

Dr.Boost

Correct me if I'm wrong(and I'm sure you will), but doesn't V-Tack activation also depend on vehicle speed? I thought you had to be going a certain MPH in order for V-Tack to activate, along with all that other ----? I've never owned me a V-Tack Honduh so I don't know for sure. :1
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