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I was going to do a vtec head swap on my b18b, but will there be any differance between making 300whp on an ls head vs a vtec head? Will there be a better powerband on the vtec vs the ls? Reason I ask is because I had been told that 300 whp is about the safe limit of horsepower on any b series stock motor, so I figured that I'll just keep it at 300 and be safe, but someone in another thread said that it's more about a safe limit on torque, and for the stock b series it's 260. I want to be able to compete against a B18c1 turbo, and I figured that if the safe limit was 300, than if we are both at that limit, I can make more torque, but if the safe limit is torque, then the b18c1 can gain more horses and still be at the same torque. If this is the case, I may either just save up for a gsr motor, just say expletive it and just rock the ls head, or just do the swap and build the block later, which would probably be the best thing to do. I'd really like to do the ls/vtec turbo, but if it's not really gonna gain me anything, I won't. Any opinions?

PrecisionH23a

The gsr head will make for a more efficient set-up. Having a better flowing head will make more power.

If you have a chance to go with a vtec head I probably would rather than working with a more restrictive head. There is nothing wrong with non-vtec by the way... I've done a good bit of non-vtec set-ups that have made killer power with b18b, b20b, and h23a heads in the past.

BoostedEG6

you will make more at the same boost level with the GSR than the LS....

But like ^^ said there is nothing wrong with the LS head just takes alittle bit more

HiProfile

The difference is torque - where and how much.

Most stock/mild vtec cams will have a bit better low-mid range than the LS since the primary cam lobes are optimized for it, and topend is better because of the higher flow and secondary lobes optimized for high-rpm. As mentioned, the head is more efficient, meaning more power for same boost level.

With that said, an LS will need higher boost (making torque) to end up at 300whp because torque will eventually drop off. Concerning the torque graph, vtec heads will give you closer to a plateau, and LS head will give you a more conventional hump.

A good analogy I can come up with - you have to swing a lighter hammer harder to crack a theif's skull compaired to a heavier hammer. The head's flow numbers is the weight of the hammer, and boost is the speed you swing it.

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iTrader: (1)

It's better to have a platue, than have it hump back down though right? Is there a way to reduce, or keep torque the same while upping the HP? Like better flowing manifold to reduce the boost I have to push to end up at the same HP? Is that an accurate example?

Can someone explain what the differance is between torque and hp? I always heard that torque is what makes you accelerate (i.e feel it in your ***) and hp was like your top end. That's not a very techinical answer though? I know high hp cars that have relitivley low top end. What about cars who have a lot more torque than horsepower? What would be the differance? Is there anywhere online that anyone knows about were I can study up on it, or maybe someone who can explain it well?

HiProfile

It depends on traction when you get to a certain point. Ramping up to 300lb/tq to make 300whp is kinda useless if your tires can't hold it once you reach full boost. But since 300whp is usually still okay with good street tires, I can't see it being an issue.

To explain it a bit more - 300whp is 300whp, but if you make 300whp after torque has dropped a bit, that's more area under the curve. But that's assuming spoolup is the same. A good way to explain high torque/low topend HP is...jump in a moddified SRT-4. They have the typical Chrysler turbo torque hump, unless they do some big mods to the head, intake, and exhaust manifold.


IMHO its better to go with a built LS (stock head) with a very good (maybe BB) turbo. If you have the LS head, use it; its either buy two turbos if you go vtec initially (cheap turbo now, then 'baller' high-end turbo), or one vtec head and one turbo ('baller' high-end turbo) if you upgrade later.

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iTrader: (1)

Well, I already bought the head, it should be shipping soon, and I have a turbonetics BB turbo, so I got that covered? Can someone explain area under the curve and what is optimal?

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bump

adseguy

I think you forgot that HP is an equation off of torque.

HP = (torque*RPM)/5252 Ever notice how ALL graphs cross HP and torque at 5252?

The greater the area under the HP curve will be the fastest car. That's why you set shift points for the greatest area after you shift.

I'm the one in the other thread that said 260trq is about what B series engines should stop at. I think people forget (or just don't understand) that power comes from torque and RPM's just put time onto that power.

I like to equate it like a punch to a bag. The harder the punch the more torque. The more times you punch the bag per second would be Horsepower. One large hit might move the bag a little, but 100 small hits will send it flying...get it? So the engine gets "hurt" because it has to deliver the "power" of the punch. That's why GSR's/ITR/B16's can have more HP then LS's because they don't need as much torque to create the same effect (horsepower) Hope that explains it.