1GGTE TVIS + Aftermarket ECU and BB Turdbro

[JustCallMeOrlando]

How would the head raise the compression? I thought on 1G's the difference in compression came from the pistons?

[Kedderz]

You tell me, im really not sure!

[web]

edit2 -

the above shows there is very little to gain lower down in the rev range in which I will be spooling 2700 to full boost at 3500, im not sure i really see the point to retain the TVIS system.

Funny to see that old graph quoted here - I'm the guy who wrote that, like ten years ago...
Here's the current link to said pic, speedtoys has been down for a while.
http://websworld.org/marcel/tech/tvis/story.gif
article http://websworld.org/marcel/tech/tvis/tvis.html
Note: no update this century, so any links in there may still be dead. Written for 4AG, but I'm sure it also applies to its 6 cyl version, the 1G



Here's the torque curves. Never mind the choppy looks - 90's technology baby!

Blue is flat and wide as it should be, with TVIS operational.
Red is a bit peaky with TVIS open all the time.
Green drops off quickly after peaking just over 4000rpm, with TVIS permanently shut.

My opinion still is: gutting the TVIS plate or removing it completely, unnecessarily throws away some driveability. With the 1GGTE not exactly a low end grunt monster as is, I personally wouldn't dream of ditching TVIS on any street driven car. You will drop from the blue curve down to the red - I know which of the two I'd prefer. And the graph above is for naturally aspirated: that bit of difference doubles up if it slows down the turbo(s) spooling as well. Especially significant with bigger turbos that are harder to spool to begin with.

Going against the "bigger is always better, ditch that farkin restriction" school I say: the big port head is simply too big for low rpm already. It's sweet for life between 5k and 8k rpm, but needed TVIS to work well below. The end result is a nice fat wide torque curve. A well designed system.

The flow numbers quoted above confirm that the stock intake already flows more than the head can handle. So you might see gains from butterfly removal on a motor ported and cammed for 8,000 rpm, but other than that... it's pretty pointless. There are other articles telling basically the same story about small vs. big port versions of the 4AGE. The small port is actually preferred at just about any rpm, because the big port is TOO BIG! Just read Bill Sherwood's excellent articles about the 4A-GE - I quote one phrase:

The small port head is the prefered type for performance in a road car, as they are easier to get up to about 200hp out of. (More than about 200hp the big port is best)

(link: http://www.billzilla.org/4agstock.htm#head )

Remember we're talking 200 naturally aspirated horsepower out of just under 1600cc. That would be equivalent to a 250hp naturally aspirated 1G-GE - way more than even the Gen3 turbocharged version ever made from the factory. So I think it's safe to say the big port head (as also fitted to the 1GGTE) is too big for anything but the most extreme high rpm applications, and needs this device (TVIS) that effectively *reduces* its port size, rather than having its port size enlarged by ditching said device.

It may sound surprising that such a thing (an intake that flows more than the head) exists in a factory engine, but that's how it is, and that's what TVIS is for. Ditch it for simplicity if you like, but it definitely serves a purpose, and does a good job at it too.

Many programmable ECU's have configurable rpm switches on board, making TVIS a breeze to hook up. And if yours doesn't, I believe even back in the '90s you could buy a separate rpm switch cheap, or break out the soldering iron and build one for under 10$ if that's your thing. So there's not much of a reason to disconnect or remove it altogether.

Another thing I read states that if you force them closed all the time, when you have sufficent inlet pressure they will open anyway.

No they don't - butterfly valves don't respond to pressure difference across them.

[web]

Some Hyundai's have a largish PWM-driven aux air valve that just uses 1 aux output pin on the ECU = they are a copy of a bosch item and looks a little like this:

Used on many early/mid 90's Volvos and some other European cars too. Probably easy to find.

[Kedderz]

As always on the internet there seems to be differing opinions. Craigs car doesnt have the rpm switch on his TVIS and on the dyno shows no big torque holes, he says that the butterflies open due to the pressure produced by the turbo at high rpms.

[1JZ-Rolla]

By the nature of a butterfly's design, I can't see how pressure could open it? You sure Craig wasn't referring to boost through the diaphragm/valve system actuating the butterflys to open? Think about it: If positive pressure alone could open a butterfly, then your throttle would be "blown" open each time you back off and the turbo built pressure against the front of the throttle body, while the manifold behind was in a vacuum state... it doesn't happen.

If the butterflys are already open and don't have a return spring, then sure, they would stay open with positive pressure (but really there'd be no positive pressure anyway since its the same either side of an open valve), but since it starts from closed, how could the airflow or pressure, which acts equally on each half of the butterfly, push it open??

I'm confoosed wif da logik

[Joshstix]

If the shaft of the butterfly valve was off centre then pressure differential could open it but that's not the case here. I have to assume there is just nothing being used to regulate the air flow to the TVIS actuator so it sees vaccum when the manifold does and boost when the manifold does. The problem with that is I expect there is advantage to be had in keeping the valves closed until there is actually positive pressure in the plenum but this way it will close them before there is even atmospheric pressure in the plenum.

[Kedderz]

there is a vacuum tank which is used and a VSV which bleeds off air which is switched by the ECU.

technically it should still work without the bleed, just using the vacuum tank which will act as a buffer of sorts.

[web]

Craig probably has TVIS permanently open, but may not realize it. Either that, or he's replaced the stock actuator with a wastegate actuator, ditching the vac system.

It also won't show large HOLES in the curves - just a torque curve a lot less fat than it could've been. The difference is easy to see, but without a back to back comparison it's not bad enough to easily spot any large holes in the curve. Just a sizeable bit of driveability, that's all.

It's not a matter of opinion whether boost can push them open, it's just mechanically impossible. Don't take my word for it, grab a spare throttle body or any other sort of butterfly valve, push at the valve (apply pressure on both sides of the shaft) and see if you can push it open. You'll find it won't move, provided you apply equal pressure either side of the shaft just like boost would.

And that's still assuming there IS a lot of pressure difference across the butterflies, which there isn't. There's enough across a shut TVIS valve to cause a good bit of power dropoff at high rpm with the valves shut, but definitely not full boost pressure.

The actuator won't open them under boost either, unless it's replaced with a wastegate actuator or something. Which would work... kinda. RPM based control is a lot better than boost based though.

[Kedderz]

At atmo pressure, ie no vacuum, the butterflies are openned as you probably know. Tonight im going to set my aircompressor to 20 psi and apply that via the vacuum tank and lets see the behavior.

Also thanks for the input

[1JZ-Rolla]

So on that theory Kedz, the butterflys would be closed under vacuum, but open at anything equal to or above atmospheric pressure? And therefore you could potentially have the butterflys open at 1500 rpm with full throttle from a rolling start, getting no benefit from the increased intake velocity with 1 lot of ports closed?

This is the longest roundabout discussion, lets hope you find a conclusive result tonight

[YLD-16L]

So on that theory Kedz, the butterflys would be closed under vacuum, but open at anything equal to or above atmospheric pressure? And therefore you could potentially have the butterflys open at 1500 rpm with full throttle from a rolling start, getting no benefit from the increased intake velocity with 1 lot of ports closed?

This is the longest roundabout discussion, lets hope you find a conclusive result tonight

Sounds like a job for the research lab of Prestige Worldwide


Sounds like the only time these things will be acting as you are hoping for is under light load cruise where it will be barely noticeable.

[Kedderz]

How about you both teach me how to measure/swap shims if needed?

Please, theres a happy meal in it for you both if you promise to be good?

Phil- the vacuum tank will act as a buffer of sorts remember but yes that situation could come to pass, just as it would on a stock ECU setup.

[YLD-16L]

the vacuum tank will act as a buffer of sorts remember

The tank will only add a delay measured in mS.

I thought Justen wrote you a tutorial on the shims, you just needed a micrometer.

[Kedderz]

Have a tutorial yes but 5 minutes with someone who has done it before will set me 100% on the correct path, thats how ive always learnt

This TVIS thing is shitting me to tears so many varying views and none of them take into account the inlet manifold which has been ported/honed/balance tube fitted.