VTec+Turbo? A good match?

[Mr_Root]

Could you guys tell me is a high rpm engine (VTEC) + Turbo a good match in case of longer use. I'm less interested in 1/4 mile sprints but more on long km/mile travels at high speed. I'm a european, we drive faster on the highways (quite often over 200 km/h)

[pvang31019]

yes, best combo in the world

[buh_buh]

I've heard VTEC and Turbo may not be such a good idea, but I don't know exactly why, your going to have someone else answer the question, but I believe that is why it is more common to turbo an H23 engine rather than a H22.

[pvang31019]

you have to tune out valve overlap....just get it on a dyno and you're set

[Predator]

For high speed travels its IMO a good combination but for acceleration it isnt (well it is too but it hasnt such an big effect like charging a big engine) because the turbo gives u also first at about 2000 rpm power!

[Type R]

hmm... I heard that like Turbo is better for FI cars and Supercharger is better for NA cars.
Is this true?

[piscorpio]

Originally posted by Type R
hmm... I heard that like Turbo is better for FI cars and Supercharger is better for NA cars.
Is this true?

What do you mean? Turbocharging and Supercharging are both forms of forced induction, once you do either your car ceases to be Normally Aspirated.

[Type R]

ok.
yeah.
Its just something that my friend told me.
But I just wasn't sure if he was correct.
But I was right.
He was wrong.

[^YellowBandit^]

Originally posted by pvang31019
you have to tune out valve overlap....just get it on a dyno and you're set

Good call. Blowby is also an effect to consider. At speeds of over 200kph, it could damage the engine.

[neouser]

I'm going to have to disagree with everyone here. I also used to think that you were better off putting forced induction in a non-VTEC Honda, but have since changed my mind. The old theory was that the valve overlap would produce excessive blowdown and, with it, a loss of power. However, one just can't overlook the fact that the more air you move into a motor, the more power you make, period. VTEC allows a stable idle while opening up to allow more airflow at higher rpm. True that you will have more blowdown as an occurance of overlap, but here's a few points to consider. First of all, blowdown means more traveling out the exhaust path. So what's good about that in a turbo car? Well, since a turbo runs off spent exhaust gasses, a little extra pressure going down the exhaust end can help spool it up a little earlier. (Especially if you move the VTEC crossover a down a bit.) Secondly, even though pressurized air is pushing against the intake valve, the scavenging effect is not completely wasted. The vacuum created by the exiting exhaust gasses can still add a little bit of velocity to the incoming charge. As everyone knows, air that's in motion tends to want to stay in motion. What does that mean? More air getting in the cylinder. Third, it is the nature of a turbocharger to create massive backpressure. Think about it, the turbo is directly in the path of exhaust flow. The bit of overlap creates a force against the backpressure and can prevent reversion from occuring. Finally, at high rpm, the speed of valve occurance is so swift that blowdown is really a minor issue. However, the additional lift and duration guarantees that you get a healthy charge into your cylinder. According to the book "The High Performance Honda Builder's Handbook" by Joe Pettitt, the 450 hp GSR buildup they did suffered some blowdown under 4000 rpm. That's under the point in which the VTEC high lobe kicks in. (4400 rpm) The top end was just fine. Anyways, the gist of it is that you really can't hurt from having dual cam profiles.

[MatT3T4]

Turbo & VTEC are friends. They just don't like to make an entrance together.

In other words, depending on which turbo you utilize, and what motor you have, you may need a VTEC controller (A'pex, R-Spec, etc...), to make sure your turbo spools before your VTEC engages. If they both commence together, your car will bog out, and you won't like your life. If your turbo spools at 2,500rpm, then your VTEC should engage around 4,500rpm. If your turbo engages at 4,500rpm, your VTEC should engage around 5,500rpm, and so on and so forth. As long as your turbo spools before the VTEC engages, you are set.

BUT, in your case, that may not be your biggest problem. Driving the way you do on the other side of the world, I would be more focused on tuning and cooling. Driving like you guys do over there, if your a:f ratio is not perfect, and you don't have ample cooling ability, you will start detonating...

[fritz_269]

If you're lucky enough to have a DOHC VTEC engine, you can even go one step further. With adjustable cam gears, you can advance the exhaust timing to dial out overlap.

FI engines do generally want less overlap than NA engines - but exactly how much depends on a lot of factors. Adjusting the relative timing of the intake and exhaust events on a dyno lets you hone in on the amount of overlap that works best for your particular setup.

DOHC VTEC + Turbo is very good.

[neouser]

Originally posted by MatT3T4
...In other words, depending on which turbo you utilize, and what motor you have, you may need a VTEC controller (A'pex, R-Spec, etc...), to make sure your turbo spools before your VTEC engages. If they both commence together, your car will bog out, and you won't like your life. If your turbo spools at 2,500rpm, then your VTEC should engage around 4,500rpm. If your turbo engages at 4,500rpm, your VTEC should engage around 5,500rpm, and so on and so forth. As long as your turbo spools before the VTEC engages, you are set....

Sup Matt...

Hrm...I was under the impression it would be better to have VTEC crossover BEFORE turbo spoolup. That way, the additional exhaust gasses from the higher airflow and the larger exhaust cam would help spool up the turbo quicker. Or does the turbo grossly hinder the exhaust flow of VTEC? I can definitely understand not having the two engage at the same point, but wouldn't an earlier engagement be more beneficial than a later one? Just my thoughts on it.

[MatT3T4]

These things sound fine on paper, but don't work out right in the real world. Depending on what turbo you have, you may be setting your VTEC as low as 1,500rpm. It isn't really pheasable when it comes to actually doing it. It probably can be done, but I would stick with the turbo first, then the VTEC. Another problem is electronics. ~Forgive me, I have been out of Honda tuning for about 6 months now~ But don't most electronic VTEC controllers limit how low you can set the VTEC? I am almost positive my old V-AFC would not allow it to go that low...

[neouser]

Originally posted by MatT3T4
These things sound fine on paper, but don't work out right in the real world. Depending on what turbo you have, you may be setting your VTEC as low as 1,500rpm. It isn't really pheasable when it comes to actually doing it. It probably can be done, but I would stick with the turbo first, then the VTEC. Another problem is electronics. ~Forgive me, I have been out of Honda tuning for about 6 months now~ But don't most electronic VTEC controllers limit how low you can set the VTEC? I am almost positive my old V-AFC would not allow it to go that low...

Probably not. The Jackson VPAC does let you start at 2500 though.

http://www.jacksonracing.com/pages/partsacura.html

Don't most turbo kits, outside of custom setups, made for Hondas spool at about 3000 rpm anyways? I would imagine that dropping VTEC to 2500, with a turbo, would drop the boost threshold a couple hundred rpms as well as improve throttle responsiveness. Then again, you're the one that had the "Beast", so I'll take your word on it...