VVT on a boosted motor: learn me

What are the parameters that an ecu look at to control VVT on a boosted motor?

I imagine it depends on the mfgr. My friends Civic had a Honda ivtec system. It was just a four valve engine that ran on two valves until the oil pressure reached 100psi. Then the oil pressure would push something (I always imagined a splined rod) that brought the other valves into action.

Pagani on the other hand have individual electronic actuators that push on each individual valve (creating an infinitely variable "cam" profile).

Just out of curiosity, car are you boosting?

Ehh, bill im not sure thats how ivtec works. Its got two cam lobes (high and low) that it switches between. Its 16v all the time just switches between low lift and high lift lobe with a cam phaser on the intake side.

That said they dont give a crap about boost. They do what they do as they were designed to do while the turbo does what it does, you can tune the vvt to help move power around but idk if thats what your asking about

But oil pressure and rpm are usually what the ecu reads to base its vvt'ing on

damn. It's been a few years but I could have swore that's what I read in the article...

Searching now, I probably misread: "Phasing is implemented by a computer-controlled, oil-driven adjustable cam sprocket. Both engine load and RPM affect VTEC. The intake phase varies from fully retarded at idle to somewhat advanced at full throttle and low RPM. T"

Color me embarrassed

Ford has in on all of the Eco Boost engines.

In reply to Hungary Bill:

No worries, me and you are in the same old school boat but i was born new school enough to have to learn the new fangled vvt crap although i still havent and probably wont ever own one...my daily is older than me and i like it like that.

I think all modern turbo junk has vvt type stuff in but op are you asking about new stuff with the tech already or are you trying to put a turbo on a vvt motor?

dean1484 wrote: What are the parameters that an ecu look at to control VVT on a boosted motor?

Engine speed, load, conditions, what the driver wants- just like without boost.

Some will tell you that blowthrough will build boost faster, but I've never seen in car evidence of that- and I really hate it.

iceracer wrote: Ford has in on all of the Eco Boost engines.

Pretty much everybody has it on everything.

alfadriver wrote:

dean1484 wrote: What are the parameters that an ecu look at to control VVT on a boosted motor?

Engine speed, load, conditions, what the driver wants- just like without boost. Some will tell you that blowthrough will build boost faster, but I've never seen in car evidence of that- and I really hate it.

It makes a substantial difference! Off the top of my head, around 1000RPM later boost build on a 2nd gear run up.

Source: I'm an engine calibrator for Ford ;)

People who screw around with the cam phasing in 1.8ts can get much earlier spool. The cam phasing in that application appears to be on/off for emissions purposes rather than a dynamic change to tailor engine output at various loads and speeds the way newer engines do it.

The topic came up on eng-tips a few years back and one tuner noted something crazy like 2000rpm earlier spool in a MiVEC engine by using the variable cam timing instead of locking it out...

There's variable lift and variable timing, and multiple ways of implementing both. Vvt I guess is technically just the timing.

I guess on a boosted car you might want to have boost as an additional input to your vvt controller because you might want different amounts of overlap at no boost vs high boost.

I'm not an engineer who plays with this stuff though, so I'm just postulating.

engiekev wrote: Source: I'm an engine calibrator for Ford ;)

Hehehe. Let me introduce you two. Engiekev meet alfadriver. Alfadriver meet engiekev.

In reply to engiekev:

So am I. And I know of a lurker who is in my section. R&A.

engiekev wrote:

alfadriver wrote:

dean1484 wrote: What are the parameters that an ecu look at to control VVT on a boosted motor?

Engine speed, load, conditions, what the driver wants- just like without boost. Some will tell you that blowthrough will build boost faster, but I've never seen in car evidence of that- and I really hate it.

It makes a substantial difference! Off the top of my head, around 1000RPM later boost build on a 2nd gear run up. Source: I'm an engine calibrator for Ford ;)

Now I know your question. On a dyno, maybe. But in the real world it doesn't. BTDT. And it's horribly bad for both emissions and fuel economy.

Besides, who in the world wants boost at 1000rpm. That's why we have transmissions. Combustion usually blows under 1300.

Besides, who in the world wants boost at 1000rpm. That's why we have torque converters

Manual transmissions allow you to be in whatever wrong gear you want!

Although that can also be screwed up. Driving a friend's WRX is funny because the converter is so tight/turbo range so high that it will build maybe 2psi if you wait long enough brake torquing it at the line. Then you let go of the brake and you move out... and move out... and maybe five seconds later, the car catches up with the torque converter and the engine speed gets up into the powerband and WHAM 18PSI.

And then there's the polar opposite in my Volvo. Tiny close mounted twin-scroll turbo that allegedly makes peak torque at 1900rpm. Too bad it has a maybe 2500-3000rpm stall speed converter. I have never been able to tell, brake torquing it will build 11psi almost instantly but the brakes can't hold the car still at anything over 7, well before it actually gets to the stall speed. I think this means it needs a bigger turbo

chiodos wrote: Ehh, bill im not sure thats how ivtec works. Its got two cam lobes (high and low) that it switches between. Its 16v all the time just switches between low lift and high lift lobe with a cam phaser on the intake side.

Not that it's pertinent, but there was a K20 version that worked like Bill described.

Nothing in particular for the moment. I was thinking about vvt the other day and then was thinking about stand alone and obviously if I am going to tge trouble of putting a motor with vvt on it I would want to add boost. This all would require a stand alone ecu and in my case MS. So that would mean you would have to map tge vvt similar to fuel or spark and I was just wondering what engine parameters you would use. I was thinking it would be rpm and MAP.

In reply to dean1484:

Most of the time, MAP is a good substitute for load, but not for VCT. You can use MAP, especially since it would be more tuned on the fly than with a dyno.

Zomby Woof wrote:

chiodos wrote: Ehh, bill im not sure thats how ivtec works. Its got two cam lobes (high and low) that it switches between. Its 16v all the time just switches between low lift and high lift lobe with a cam phaser on the intake side.

Not that it's pertinent, but there was a K20 version that worked like Bill described.

Honda has had a bunch of different versions of VTEC over the years that have worked a bunch of different ways, as I understand it. What Chiodos is describing is the "original" VTEC YO!, with a completely separate lobe on the camshaft that is engaged when needed. This has the theoretical advantage of being able to alter phasing, lift, ramp, ect. - basically a completely different cam profile all together. Contrast this with i-VTEC, BMW VANOS, and a lot of the other VVT systems out there that I'm even less familiar with, which only have a means of altering the phasing of the cam via basically twisting the cam relative to its drive sprocket to either advance or retard timing.

I assumed so from some of your other posts, now I know the truth!

Robbie wrote:

engiekev wrote: Source: I'm an engine calibrator for Ford ;)

In reply to engiekev: So am I. And I know of a lurker who is in my section. R&A.

In reply to Zomby Woof:

Really? Teach me more, i havent found anything...and when i corrected bill, i read the wiki article on ivtec as a refresher. I was pretty sure they didnt do it the way he described but hey ive been wrong before. I just want to know for my own good, ya know?

Honda said: The 160 horsepower RSX employs a new version of VTEC to boost performance and reduce emissions that applies variable timing and lift to the intake valves only. Additionally, the RSX system is further simplified by utilizing only two roller arms per pair of intake valves (instead of the usual three). During low rpm operation, intake air is drawn almost exclusively through the primary intake valve, thereby creating a very strong swirl effect to maximize combustion. At 2,200 rpm, the secondary rocker arm engages the primary rocker causing both intake valves to open for the same lift and duration, substantially increasing airflow into the cylinder and boosting performance

http://news.honda.com/newsandviews/article.aspx?id=426-en