Variable intake to lift torque dip

[burdickjp]

Originally Posted by serialk11r

Not true at all. Being able to time intake valve closure precisely lets you capture the maximum pressure (and thus mass) of air in the cylinder, but tuning runner length is what maximizes the amount of air entering the cylinder in the first place at any speed. Both VVT and variable length intake are commonly found on engines.

Think of it as a sprocket pulling a chain back and forth (representing the waves in the intake). Tuned VVT is like putting a ratchet mechanism on it, but the runners control the amplitude of the sprocket's movement.

The engine's breathing is a system that works together, all the pieces have influence.

I have no idea what you're trying to get at with chains, sprockets, and what that has to do with pressure wave propogation and amplitude.

Implementing even a discrete variable length manifold would introduce another variable to tuning, which would require many man hours to optimize for what would likely be very, very little gain.

[serialk11r]

Originally Posted by bur****jp

I have no idea what you're trying to get at with chains, sprockets, and what that has to do with pressure wave propogation and amplitude.

Implementing even a discrete variable length manifold would introduce another variable to tuning, which would require many man hours to optimize for what would likely be very, very little gain.

Well, the peak pressure in the cylinder while the valve is open is determined by the intake runner. Variable timing lets you close the valve when there's the most air in the cylinder.

The intake absolutely matters a lot, it's why the FA20 has pretty good torque around 3000rpm despite having a cam profile better suited for 6000rpm operation.

Discrete length manifold is really easy to tune, just run the engine with either length and see at what speeds one makes more power than the other.

The hardest part is actually building the darned thing, which isn't even hard, just a lot of dollars for the power you get.

[burdickjp]

When you have just a discrete system, yes, that's easier, but now you have to tune the continuously variable VVT system and the discrete intake system. Fully optimized you are basically tuning two VVT tables and switching between them. This can be reduced to a single VVT table once you've fully optimized.

That I remember, intake runner length doesn't change pressure, it changes frequency, but it's been a while since I've needed to know any of this off the top of my head.

[serialk11r]

Originally Posted by bur****jp

When you have just a discrete system, yes, that's easier, but now you have to tune the continuously variable VVT system and the discrete intake system. Fully optimized you are basically tuning two VVT tables and switching between them. This can be reduced to a single VVT table once you've fully optimized.

That I remember, intake runner length doesn't change pressure, it changes frequency, but it's been a while since I've needed to know any of this off the top of my head.

Correct, but you need the frequency to be "in tune" with the valvetrain frequency for the peak of the wave to land where the valve is closing every cycle, which is how you improve VE.

Good point about tuning VVT, but you don't need to tune the whole table twice. You already know that with shorter runners, you don't want to be using the shorter length setting below like 3500rpm, and the stock table is already good to go for the stock manifold configuration. So you just directly modify the table from 3500rpm up with the short runner setting. Chances are it'll produce more power in the "torque dip" area anyhow and higher harmonics are much weaker so just leaving it like that is probably close to optimal. OEM variable length intakes are basically rpm switched like this afaik.

Also you don't even need to touch the VVT at higher rpm where it's already on max retard, so it's not too bad.

[burdickjp]

Originally Posted by serialk11r

Correct, but you need the frequency to be "in tune" with the valvetrain frequency for the peak of the wave to land where the valve is closing every cycle, which is how you improve VE.

That's what VVT does.

[serialk11r]

Originally Posted by bur****jp

That's what VVT does.

No, you're forgetting that the piston is also moving. You can catch the pressure wave at its peak, but the piston could be well on its way up and you'd be late.

Or, you can use common sense and realize that many engines come with both systems, for good reason.

[burdickjp]

Originally Posted by serialk11r

No, you're forgetting that the piston is also moving. You can catch the pressure wave at its peak, but the piston could be well on its way up and you'd be late.

Or, you can use common sense and realize that many engines come with both systems, for good reason.

The piston is usually on its way up when the intake valve is closing.

Originally Posted by serialk11r

Also you don't even need to touch the VVT at higher rpm where it's already on max retard, so it's not too bad.

Are you sure? It doesn't seem to be that way on the Zx6.

Continuous intake VVT allows the harmonics of the intake to operate over a larger RPM range. Most of the benefits can be had with good intake and exhaust choices and tuning, tuning, tuning.
What I'm getting at is that it would be prohibitively expensive to try to add to a car aftermarket and the gains would be marginal at best.

[KoolBRZ]

Originally Posted by Hemp Bike

Thinking about the infamous torque dip. Has anyone had any success with a variable intake manifold?

Making an intake manifold to remove the torque dip would be very expensive. You could turbo the car for less money. I would recommend getting an OFT and learning to tune with RomRaider instead.
I'm going to be working on removing as much of the torque dip as I can, today.
I'm using my OFT to tune out the dip, as much as I can, by gradually changing the AVCS "safe" intake and exhaust tables in RomRaider. It is an acquired skill but the learning curve isn't too steep for me. I had it adjusted for good power, mileage, and very little dip with my old EL header, but I just went to a PLM long-tube header, and the torque dip came back, with a vengeance!

Since the OFT holds 5 tunes plus stock. I can use my existing tune in the middle slot, adjust just the intake table, 2 points lower, 4 points lower, 2 points higher, and 4 points higher. Load them in as 2low, 4low, 2high, and 4 high, get out, and drive. I will then compare them to my existing tune to gradually seek out the right direction and amount of change to remove as much of the torque dip as I can. Then I will do the same for the exhaust table. I just love tuning my car myself and not relying on anyone else to tune it for me.

P.S. @shiv has just released a Procede controller to be used, instead of a throttle switch, to control the Phantom Electric Supercharger. It can be programmed to control up to 4 - 5 devices if my memory is correct. What if you got a variable intake with an electric switching valve, a variable muffler with an electric switching valve, and a Phantom Electric Supercharger. You could control all three with the procede controller, and program it using the same type of 3d spreadsheet mapping that the engine ECU uses. THAT would be awesome!