ls/vtec question

jigglenuts · Post by **jigglenuts** » Sun Dec 10, 2006 10:38 am

i have a b18a, if i were to do a vtec head what gains would i see .
also if i do go turbo would the vtec be an advantage or not.

like i said before im new to the world of hondas and i realy havent a clue,so this may seem like a stupid question to some ,but its info that i need .
id rather look like a fool and ask then spend alot of money for nothing and feel like an ass. so any one who could help me with some question /answer time i would be very greatful , thnx Dan

:tree2:

Silver Knight · Post by **Silver Knight** » Mon Dec 11, 2006 5:48 am

jigglenuts;4074 wrote:i have a b18a, if i were to do a vtec head what gains would i see .
also if i do go turbo would the vtec be an advantage or not.

like i said before im new to the world of hondas and i realy havent a clue,so this may seem like a stupid question to some ,but its info that i need .
id rather look like a fool and ask then spend alot of money for nothing and feel like an ass. so any one who could help me with some question /answer time i would be very greatful , thnx Dan

:tree2:

you would see some pretty good gains. its just slightly faster than an ITR. people do the ls/vtec mostly for torque. as for turbo, yes it would be an advantage. why wouldn't it be? if you do go turbo you may want to but it some CTR pistons to help lower the compression.

HondaChild · Post by **HondaChild** » Mon Dec 11, 2006 6:03 am

Silver Knight;4283 wrote:you would see some pretty good gains. its just slightly faster than an ITR. people do the ls/vtec mostly for torque. as for turbo, yes it would be an advantage. why wouldn't it be? if you do go turbo you may want to but it some CTR pistons to help lower the compression.

yea one thing about builting an LS/vtec is that the compression is usaully pretty high if your planning on running it on boost. and for horse power gain yea you will be able to tell the difference.

Spork · Post by **Spork** » Mon Dec 11, 2006 6:17 am

HondaChild;4292 wrote:yea one thing about builting an LS/vtec is that the compression is usaully pretty high if your planning on running it on boost. and for horse power gain yea you will be able to tell the difference.

not true. look at the ls/vtec link i posted in the engine tech forum, you can build the motor with a ton of different pistons and have compression from 9.6 to 12.4:1! thats a huge range. I'd hardly call 9.6:1 high compression for boost.

and Allex- CTR pistons offer the HIGHEST compression available, not a good bet for boost. the stock LS pistons offer the lowest compression, but I don't have any experience with them to know if they would hold up to 8000+rpms and boost. or if you'd be better off with other ones. P72 GSR pistons are the next lowest compression stock pistons @ 10:1, maybe those would be your best bet :dunno:

But yes, an ls-vtec build would help you, even with boost as long as you build it right.

Post by **budget_crx** » Mon Dec 11, 2006 6:33 am

about VTEC being an advantage for boost, I would say realistically no. The reason being VTEC cam profiles have a longer duration which, on the exhaust side, can cause reversion back into the combustion chamber due to the extra restriction of a turbo. A longer duration will be more likely to have this happen.

As far as the intake side goes, the longer duration and higher lift will help flow more air in, more air = more power, but it will also be harder to tune as the VTEC can be considered an irregularity in the a/f ratio. this is no big deal with a good tune though.

so basically I'm saying non-vtecs and sohc vtecs respond better to boost than do dohc vtecs. unless you have a killer build with a turbine that flows good enough that it is hardly a restriction in your exhaust system, but good luck with that.

jigglenuts · Post by **jigglenuts** » Mon Dec 11, 2006 7:22 am

budget_crx;4305 wrote:about VTEC being an advantage for boost, I would say realistically no. The reason being VTEC cam profiles have a longer duration which, on the exhaust side, can cause reversion back into the combustion chamber due to the extra restriction of a turbo. A longer duration will be more likely to have this happen.

As far as the intake side goes, the longer duration and higher lift will help flow more air in, more air = more power, but it will also be harder to tune as the VTEC can be considered an irregularity in the a/f ratio. this is no big deal with a good tune though.

so basically I'm saying non-vtecs and sohc vtecs respond better to boost than do dohc vtecs. unless you have a killer build with a turbine that flows good enough that it is hardly a restriction in your exhaust system, but good luck with that.

so in other words just doing a lil head work and maybe cams would be enough if i am going to boost which i will be soon.

Post by **budget_crx** » Mon Dec 11, 2006 2:16 pm

jigglenuts;4345 wrote:so in other words just doing a lil head work and maybe cams would be enough if i am going to boost which i will be soon.

oh yeah, just a polish would help immensely on any honda head.

jigglenuts · Post by **jigglenuts** » Mon Dec 11, 2006 3:08 pm

Thanks

Waffles · Post by **Waffles** » Mon Dec 11, 2006 6:18 pm

budget_crx;4305 wrote:about VTEC being an advantage for boost, I would say realistically no. The reason being VTEC cam profiles have a longer duration which, on the exhaust side, can cause reversion back into the combustion chamber due to the extra restriction of a turbo. A longer duration will be more likely to have this happen.

As far as the intake side goes, the longer duration and higher lift will help flow more air in, more air = more power, but it will also be harder to tune as the VTEC can be considered an irregularity in the a/f ratio. this is no big deal with a good tune though.

so basically I'm saying non-vtecs and sohc vtecs respond better to boost than do dohc vtecs. unless you have a killer build with a turbine that flows good enough that it is hardly a restriction in your exhaust system, but good luck with that.

Jake, leave it to your ass to bring truth into the world of Hondas. Most people don't understand cam profiles and when you need more/less lift and duration. Remember kids when it comes to cams bigger is not always better.

Spork · Post by **Spork** » Mon Dec 11, 2006 6:26 pm

btlfedgolf;4399 wrote:Jake, leave it to your ass to bring truth into the world of Hondas. Most people don't understand cam profiles and when you need more/less lift and duration. Remember kids when it comes to cams bigger is not always better.

I've commented on that in other threads on here, the vtec heads may not be best heads for boost, but they flow better than the stock b18a/b heads, and in a lot of cases easier/cheaper to get ahold of than porting/polishing an a/b head and replacing the valve train.
But if you want to invest in building the stock b18a/b then go for it, I plan on it for my next project (or an sohc vtec turbo)