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This is a discussion on Vtec VS Non-Vtec in the Forced Induction forum
At least i didnt jump you and call you stupid or something like i'm sure someone would have. We are all wrong on something, i just find it more pleasing to correct you, even if you are wrong.. so that you know you were and ...
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|07-07-2003, 11:09 PM||#26|
At least i didnt jump you and call you stupid or something like i'm sure someone would have.
We are all wrong on something, i just find it more pleasing to correct you, even if you are wrong.. so that you know you were and to get the right answer.
Back to the guy's question.. controlling the vtec, wont help valve overlap, b/c the valve overlap starts when vtec does.. so if you set vtec at 4200, then overlap starts then.. it just doesnt overlap when it kicks in and after it is in vtec, its fine.. there is overlap throughout vtec.
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|07-08-2003, 12:55 AM||#27|
Again I could be completely wrong in this, but when I race I live in the higher rpms, because thats the only place I have any power.
|07-08-2003, 01:21 AM||#28|
Domeskilla is right- most vtec systems are 2-stage (hi and lo) but the s2k and the d15b and i also believe there was some other jdm motor (like a d13??) that has the 3 stage.
Now, Overlap is controlled by two things- the cam profile, and the degree of the cam gear. in other words, its all cam.
Overlap is good for one thing- making high rpm power. when you are spinning at 8000+ the time from open to close gets smaller and smaller due to the fact that the time it takes to open and close gets less and less. with a longer over lap, the top end is not killed, because the duration keeps the valve open longer even while moving super fast.
On a boosted car, overlap sucks. under 8000-ish, a lot of your air will simply push itself right through the chambers... out the exahust valves that are still open due to the cam, and never combust, thus impeeding your power potential. with a near stock overlap (such as a gsr cam's duration), little to none is leaked out, thus giving you the air in the cyl. to make the power- the whole point of a turbo in the first place.
the ideal cam for turbo is one that has a good lift (opens the valves high) at a near stock duration. thus, it allows a LOT of air to get in and out, but the time it is open and closed is not made longer.
This goes for ANY cam style... VTEC or NON-VTEC.
Now, back to VTEC vs. Non-VTEC... Why is VTEC advantegous?
By offering 2 (or more) lobes, the car can make bot good low end power, and still have a good top end.
Think v8's for a min here. they use a small cam for great torque off the line, but are dead at 6000 rpms.
sound familair? yup- the LS is the same way.
and you know what, so is the GSR, ITR and so on--- until it switches lobes. the cam profile of the low lobe is good for 5000 rpms, and then its over.... hello vtec, swap over and lock the middle lobe, and suddenly we are on a larger cam- one that wucks balls in the low end, but has a little more duration and lift for better top end power.
Ok, so now all the non-vtec whores are saying, ok- but why not just run a big cam (say, stock gsr vtec lobe specs) in the LS.
you can, but like i said above, your low end is going to fail- at least as far as power is concerned. you will have no torque until 5000 rpms, just about when youd hit vtec to go to the larger lobe that a vtec setup offers.
As for "I like the non-vtec due to its low end torque".
Well, let me tell you something. BOOST is your torque. Stop thinking like an all motor guy. This is the boost forum
Jeffie7 has a boosted b16a. at 2500 rpms, he has well over 100 ft/lbs at the wheels, as dyno proven.
you won't see 100 ft/lbs on even an LS until at least 3500+ and probably close to 4500 on a more built setup.
here's wildbill's LS dyno. P&P head, b16 pistons, crower 403 cams.. all motor, yes... but i'm just using this as an example.
ok, now notice what i said... its just around 100 from 1000-3000 and then slowly goes up in torque till it flattens out.
now, lets take a look at jeffie7's boosted b16 dyno.
Got torque? it just fucking climbs.... and that's before the vtec engagement of 5200-ish. That is what boost is all about.
so stop thinking like an all motor guy, and start thinking like a boosted guy- Air flow = power.
size, really doesn't matter.
On top of ALL of this:
-the LS head FLOWS like shit - air flow = power
-the VTEC bottom ends have oil squiters which help reduce heat and detonation on a boosted car.
and i could go on for days. but going back to m y frist post. there IS NO arguement. VTEC is a better technology, and will alwyas make more power- na or boosted.
however, for the inital cost of about 2000 less, the LS motor has great potential for a guy on a budget just looking for a little more umph... and not a 10 second car.
|07-08-2003, 01:40 AM||#29|
this seems to be a GSR vs LS argument, that being the ls has more bottom end torque and the GSR with hi rev VTEC. What about LS/T vs LSVTEC turbo? Comapring these two should answer the original question better. Personally, I don't see why vtec turbo is a bad thing, just get vtec cams ground to turbo specs.
|07-08-2003, 02:14 AM||#30|
there is NO point to building an LS/vtec/t
83mm sleeved GSR bottom end, stock 10:1 compression forged pistons, crower rods. otherwise STOCK motor, put 586 WHP to the ground.
do you REALLY need more than that? no.
|07-09-2003, 05:05 PM||#32|
I think the big reason most people either go boost or ls/vtec (besides money) would be the added compression you get from the VTec heads... it doesn't lend itself well to a whole lot of boost. You will have more reliable power from a straight boosted LS.
Another comment, the reason the LS is so rich with its torque is because it is a larger displacement bottom end than the GSR (1837cc vs 1789cc).
|07-18-2003, 05:00 PM||#34|
The main advantage of a non-vtec turbo setup is the same advantage of a non-vtec NA setup: it's half the work to tune. With one cam profile to tune, your job is a lot simpler.
To tune a vtec motor properly, I was taught that the low and high cam lobes must each be tuned independently on the dyno: 1 session of tuning with the vtec solenoid unplugged, 1 session with a +12V signal fed to the solenoid full time. Superimpose the graphs on top of each other, cross over vtec where the HP curves cross.
That's a lot more work. I can totally see how vtec motors get a reputation for being difficult to tune compared to non-vtec or domestic motors.
I'm still waiting on a downpipe and manifold to be sent for my non-vtec motor. I can't claim to be a pro, but I've spent more than my fair share of time getting schooled and a ton of time learning about engine operational theory to help my ECU development efforts.
Everything I've read or seen tells me that a vtec motor with *appropriate cams* tuned properly will make more power than a non-vtec motor of comparable compression, displacement and cammage(is that a word?) - its like a non-vtec motor with not just one but TWO good turbo cams...
I think the non-vtec vs. vtec argument stems more from people trying to turbo vtec motors that do not have cams friendly to boost (ITR, for example. Every time I see a turbo type R, I say to myself "what a waste"). There are tricks you can do with cam gears and ITR cams (dialing cams back at each other to decrease overlap) but ...
|07-20-2003, 11:29 PM||#35|
All I can say is I have a 93 civic hb with a non-vetec B18b1 and my friend has a 91 civic hb with a Ls/vetec motor and we raced and I was a car lenght ahead of him the whole time.we raced two times and both times I beat him.maybe he is not tunned right,I dont know but I still beat him.I have also raced a crx with the B16 in it and I beat him to.Alot of people are impreased with the way my car works with a non-vetec motor.thats my two cents worth.
|07-22-2003, 09:21 AM||#37|
doh VTEC is not a power adder.. VTEC helps keep the TQ from dropping in higher RPMS so they dont have to shift as early as non vtec engines.. hence giving them the advantage
heres a small article on it
how do you like the TQ on a LS over say a gsr? its just about the same.. ????
People really misunderstand VTEC and the difference between power and torque.
The first misunderstood fact is that acceleration is a function of torque at the wheels, which is engine torque times gearing, less any drivetrain losses. Not horsepower per se (but see more below).
The second misunderstood fact is that variable valve timing does not increase torque (or, as a result, acceleration) at higher revs. Its objective is to prevent torque from dropping as revs increase. When you look at the torque curve for a VTEC car like the NSX:
you can see that it's quite flat from roughly 3500 RPM to about 7500 RPM, and there is no huge increase above the VTEC crossover point of 5800 RPM. If it didn't have VTEC, you would see the torque drop rapidly as revs rose above that point.
The advantage of a wider, flat torque curve like this is in gearing. Cars without VTEC would be forced to upshift by around 6000 to 6500 RPM for optimal acceleration, and when they upshift, they lose acceleration because of the loss in gearing. This is why VTEC cars are so much faster than their torque numbers would imply - because they gain an acceleration advantage from their ability to stay in a lower gear before upshifting.
If you would like a more lengthy explanation, including how horsepower numbers reflect this, read this excellent article about the difference between torque and horsepower, and how gearing comes into play.
Another informative website, that explains how Honda's VTEC system works, is here, with links to similar topics on that site.
|07-22-2003, 07:15 PM||#38|
i really see no point in comparing n/a dyno charts to a boosted, built and tuned b16a dyno.....
install the same turbo setup on the ls and see what happens
and if youre trying to say that a b16a has more low end than a ls, stock for stock, youve never driven a stock b16 powered car
|10-23-2008, 09:15 PM||#41|
ya singe camz gots one stage where its just the intake valves open up
b-swaps or dohc like the gsr gots two where its the intake and exhaust
i heard something bout 3 stage...someting bout these older ZC motors from japan that are like dseries and a dohc Dseries motors. im not too sure how it works
but i know if u listen to a a gsr on a dyno you can hear to sexy vtec cross-overs
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