Originally posted by brekekex
[B]
Can someone tell me WHY they think the ls/vtec is soooo unreliable?
I have points to make here, but I will save it untill I get a repy from someone with a valid argument.
I want to see how many people assume things, or just repeat what they heard, and how many people put actual intelligent thought into their opinion.
Enlighten me. =)
-T [/B]
This was posted in another thread, and it piqued my interest. I would like to get an intelligent discussion about LS/vtec. I would also like this thread not to turn into a war about swapping vs. LS/vtec, or anything else like that. Just straight facts about what many don’t even know about. Like Thomas said, if you have experience, please post, but, if you are going to repeat things that you have heard from your cousin’s best friend’s brother, then please don’t bother posting. I just want to get some straight facts about what others (and myself) don’t know too much about. I have heard plenty on the “unreliablity” issue. Granted, it is a concern, considering many of these new breed of engines haven’t been on the road a long time (considering what the B16/7/8s have mileage wise in our cars). So, sit back and relax, and join in the discussion.
the problem with this conversation is that there are too many levels of ls/vtec. At the most basic level (stock block w/ vtec head) its not very reliable if you rev it out like a vtec engine. But if you do some relatively simple mods to the block before hand then it seems it can be a very reliable engine.
at the beginning a lot of people were doing half ass jobs and having problems (everything from piston-valve contact to oil leaks and busted bottom end parts) this gave it a bad name in the eyes of many people.
from what i’ve seen, the most important recommendation is to get stronger rod bolts, followed by a vtec oil pump (and water pump too). Balancing the rotating assembly and shotpeening the rods seem to be up there too.
Some people have been saying that they want to go ls/vtec, but don’t want rev higher than the stock redline. I believe that defeats the benefits of vtec by not taking advantage of gearing to make a car with a low torquey engine faster.
daver, the main reason why low rpm reving vtec engines are dumb is the cams. the vtec cams are designed to make power beyond 7k rpms (some cams even up to 9000-9500!).
"its not very reliable if you rev it out like a vtec engine. "
You said it dude… “if”.
If redline is kept to a sane level, and respective of the amount of bottom end work that has been done to an engine, then the B18 WITH a vtec head will last as long as one without it.
And hell yeah it will make more power… and it will cost less than a set of 62404’s with springs and retainers.
And whether you go vtec or not, if you really want to make a lot mroe power, youll have to rev higher (unless you add boost or displacement).
Well I can see it stayed a intellegent conversation for about 2 minutes. Heres some facts I have picked up over the last weeks researching my options, LS/VTEC vs Turbo on the LS.
LS/VTEC…
The reason the bottom end on a LS is so rel. weak compared to the b16a and b18c engines is that the rod and strokes on these are different. The LS will make more power, because of that rod and stroke ratio. The only problem is that the smaller the ratio gets, the more force is put into the rods, and consquently the rod bolts, crank, bearings etc. You can build the bottom end to avoid these problems.
Personally, I wonder if you were to do the LS/VTEC with a 92 B18A with a good bottom end and lo miles with a B16a head, could we just swap in new bearings and the vtec oil and water pumps? I see the benefits in shotpeening the rods or swapping pistons to avoid potential confrontations between the pistons and the valves, but this would make a rather simple project turn into a full rebuild. Its not that I dont have the time, or dont want to spend the money, but some people dont want to pull the rods and crank and then have to re-hone the block and re-ring while what they have is sealing really good.
So if anyone else has some intellegent comments other than the u cant rev to 9 grand…(no ****!) please feel free to join in as I’d like to hear some tech on whats really the problems or worries with ls/vtec. (Guru? Amerikan?)
Haha… I wonder if you, after doing some research, understand WHY is it that a low rod to stroke ratio has a detrimental effect on an engine… and yeah, no **** you cant rev it to 9k without preperation of the block and its internals…
Soo… the B18A/B and B20B/Z are so relatively weak compared to a B16 and B18C due to its undesireable r/s ratio…
Did you during your research, ever compare r/s ratios of a B18A to that of a B18C?? Haha… they are not far off, sorry.
Granted, the B18C has a more favourable r/s ratio, but not by much.
They are still a great deal away from a B16 in terms of rod lenght and stroke.
Anyways… I do believe that most people are aware of this, but thanks for sharing your vast knowledge with the rest of us.
I am merely trying to get the message across, that an ls/vtec is like any other motor, in that it needs to be build respective to ones expectations and goals.
If you choose to take your healthy B18A (or any variation of the non vtec 1.8L and 2.0L engine) and install a vtec head on it, you will see very decent gains relative to what you put into it.
It seems that people assume that if it says vtec, it must be wound out to stratospheric rpm’s, and with that kind of attitude, the B18A will never be a reliable engine once a vtec head is mated to it.
here’s a continuation of my above post that i don’t think i explained very well.
If you do the ls/vtec swap and don’t rev the engine any higher than stock, you’ll completely miss half the point of the high winding vtec power (as far as the other factory “gutless” vtecs engins go anyway). It will essentially be the same as leaving the b18 in non vtec form 'cept with a higher cr, ported head and more aggressive cams (as far as the “high end” goes). There will definately be lots more power with the ls/v without rip revving it high because of the afore mentioned mods, but read on. Vtec is basically a gimmik that takes advantage of gearing. Its not the hp you “feel” during acelleration at all, its the torqe. Consider this hypothetical race scenario - two cars - all things being equal (same tranny, same peak torqe, same weight, etc., etc.), the vtec car won’t acellerate any harder than the non vtec counterpart, it’ll just acellerate for LONGER, in any given gear. So the two cars will be neck and neck (or so) until the non vtec has to shift into second, then the vtec will walk away with 2000 more rpms of good torque still to go in first gear (bye bye). hp is really just an “artificial” measurment derived from torqe. It describes how much force (or work) the engine provides in a given amount of time. So the impressive looking hp figures on vtec engines (the gutless factory ones anyway) simply mean that the engines are still making good torqe at high rpms (ie. good “force” in a short amount of time). The Gsr can pull harder at freeway speeds than the LS because it can downshift to 3rd, where the LS has to stay in 4rth. The gsr isn’t making more “power” (not the best word to use here) here, it just makes it in a better spot to take advantage of the gearing to produce a “faster” car.
All that aside, the “stock” ls/vtecs do seem to make pretty impressive power even at the low/high rpm range and it seems to drop off at around 7500 (which isn’t all THAT high revving). Also, you still get to keep the good low end drivability that you would not get with the modded straight LS engine, thanks to vtec.
Any comments or corrections here? L8tr,
d
ps. I’m still trying to find a completely stock ls/v dyno chart; anyone know where?
Why can’t you guys just take the money you will spend on doing an LS/Vtec motor (I would think give or take 4000+ in change for all the parts), and use it on an otherwise stock JDM B20Z, a fuel computer, external fuel pump, and a turbo kit? I am willing to bet that this will be faster than an LS/VTEC motor.
I’d say start with the b20, drive that around for a while, then throw a b1a1 head on that beast for a CRvtec. Not only will you end up with a better set up, but you spread the build-up fun out longer, which is half the joy (i think).
turbo is generally out of the question for most people i think though, because the issue with ls/v is reliability and longevity. Turbo almost anything will be more power than a basic ls/v, but there goes the peace of mind. Besides, turbo is cheating
Yeah…so now that were on my other idea of turbos…Lets keep it Ls/vtec. This has been a good discussion in here…maybe Dan will share some of his knowledge with us.
Brexek- I did compare the R/S ratio on the engines, and yes I did realize the B18c is quite close to the B18a. The b16a is nowhere close. As far as I understand the R/S ratio, the lesser the ratio the more force is directed straight into the rod…correct me if I’m wrong cause I’d love to hear more about this stuff…
Jim
Yeah, the B16 r/s ratio has been declared as near “perfect” by some…
With a lower r/s ratio, piston speed increases dramatically… hence forces on the rod bolts and rod are greater, especially during deceleration and on the intake stroke, it is then that the crankshaft has to pull the rod and piston down.
Also, with a short rod, at 90degrees ATDC, the rod sits at a very steep angle in relation to the cylinder walls, so there is a lot of force transferred directly to the cylinder wall.
This angle, combined with high piston speeds, means that the rod/piston has to change direction (up/down and side to side) very quickly.
The upside of this is that, power can be made at lower rpm’s compared to a higher r/s ratio engine, and this makes the engine behave better at low rpm also.
There is a lot more to all of this… and its all well beyond me. =)
You say this:
"If you do the ls/vtec swap and don’t rev the engine any higher than stock, you’ll completely miss half the point of the high winding vtec power "
and this:
"All that aside, the “stock” ls/vtecs do seem to make pretty impressive power even at the low/high rpm range and it seems to drop off at around 7500 (which isn’t all THAT high revving). "
in your post… soo… in reply to the first comment I will say that, stock B16 cams will peak at a lower rpm in a 1.8L engine with a shittier r/s ratio, than in a 1.6L with a good r/s ratio.
But then you seem to agree with me on that in the second comment…
Otherwise, I agree with most of what you said.
Yep, i was kind of talking about two different things in that post. Taking a vtec engine and not winding past a comparable non vtec’s redline is wasteful, but its not soo bad with the LS/v because it provides gains ALL through the powerband. So i hear anyway (i don’t have one), i’m still looking for a completely “stock” ls/v dyno chart to compare.
Eehhh. just when I finally decided that I should stock up on LS goodies, this thread starts up…
Well okay here’s some food for thought:
Stock LS/VTEC:
B16A1 w/ dist, im = $350-400
New valvesprings to prevent any float from tired springs = $125
New valveseals = $35
VTEC ECU = $250
Fittings = $150
GSR Oil pump = $75 used
GSR Timing belt = $75 (approx)
This gives approx $1060
worked LS:
62403’s/404’s = $275 used
Crower Valve springs = $175
Chipped ECU = $150
New valveseals = $35
Headwork, valvejob, IM work = $400
This gives approx $1035
In my case I will add to both setups cam gears & headers ($400). You want a short geared tranny, add another $350.
We must all realize what LS/VTEC is doing and how I see it.
To add more power to your LS you usually start with the cams… Add some lift & duration. You need springs as well. Well, as we all know the VTEC head incorporates the high lift & duration cam into its 3rd lobe, and only giving it to us where it makes a difference (at vtec x-over point).
Let’s discuss the powerband of these different engines BELOW 7500rpm with the stock LS tranny and assume things just get better with a short geared tranny.
Hey, I got a question. <br> How does an ls tranny affect an ls/vtec setup compared to a gsr tranny? Which is better for the power being produced? <P>www.jcbadcura.elitecaraudio.org
Rich-
The reason I don’t want to build my Ls is that I have heard complaints about having cams in the engine as it contributes to horrible daily drivability…(not that LSVTEC is perfect either).
But I would rather take on the challenge of building a reliable LSVTEC. I’ve had the chance to take a ride in a ITR the local shop owns and it is Freakin awesome when that mofo switches to the big bad vtec lobes. I’d like to keep my stock lobes and have the bragging rights to saying I built a powerful reliable LSVTEC…(yeah i know its gonna be hard)
Jim
jwork: I’m up to the challenge too, but for the same money, I want an engine that will make as much power if not more than a built ported LS AND be as reliable and have a good life span. Come to think of it, I’d probably rebuild the bottom end the following year.