Blocking ABV with aftermarket ecu

[reecegze]

Hey guys i needa know 100% if its ok to block the abv off with an aftermarket setup ecu. Reason i ask is that my ABV is still connected and i have no longer any blue or brown vsv controls as its all ran by the ems ecu. Would my ecu be controlling the boost and not the abv??? or would the abv be still working but with the ecu controlling it when to bleed off. I run max 11 psi with a nevo 175mm so i am assuming the abv is not working due to the aftermarket setup doing something.

[BeRad]

you can block it, the stock ecu has no way to control it now, all thats for is boost cut, and the stock ecu would no longer be controlling ignition or fuel so has no way of cutting the boost, remove the thing, and let the wastegate do its job until you fit a boost controller and then let the ems do the cutting as should have been setup in the first place.


the abv i assume sends a voltage to the ecu telling it what boost the engines at when it reaches a preset voltage it will cut fuel or ignition to stop overboost. so it would be sending the voltage but the stock ecu has no power to cut the fuel or ignition , what is the stock ecu doing in the car? the fuel pump etc?

[mic*]

The ABV is controlled by a pressure signal which comes from the VSV. Without VSV control the ABV will not be working.

The VSV is actuated by the factory ECU based only on revs & load. It is actuated at high revs & high load to prevent overboost. It is also actuated when the revs & load are low - basically whenever the SC is clutched off. This is for economy so the engine doesnt have to breathe through the lobes of the charger.

With an aftermarket ECU the simplest thing to do is to replace the VSV signal to the ABV with a manifold pressure reference. This way the valve is open whenever the engine is off boost, keeping the economy, and always closed under boost for obvious reasons.

[reecegze]

Thats good news thanks for that saves me experimenting

[feral4mr2]

The ABV is controlled by a pressure signal which comes from the VSV. Without VSV control the ABV will not be working.

The VSV is actuated by the factory ECU based only on revs & load. It is actuated at high revs & high load to prevent overboost. It is also actuated when the revs & load are low - basically whenever the SC is clutched off. This is for economy so the engine doesnt have to breathe through the lobes of the charger.

With an aftermarket ECU the simplest thing to do is to replace the VSV signal to the ABV with a manifold pressure reference. This way the valve is open whenever the engine is off boost, keeping the economy, and always closed under boost for obvious reasons.

No, not at all.
i could explain it my way, but i'll post this instead.

Air Bypass Valve
The air bypass valve (ABV) serves two functions. The first is to provide a route for air to bypass the supercharger when it is not spinning. The second is to act as a blow-off valve when boost exceeds aproximatly 8 PSI. The blow off point varies significantly between cars from 8 to 10 PSI.
The valve is attached to the rear of the supercharger and is closed when the car is not running. It is in effect, a spring loaded plunger that blocks a port that runs from the supercharger inlet to the outlet. When the intake manifold pressure on the plunger exceeds the spring pressure, the valve starts to open, allowing the outlet side to discharge some of it's air back into the inlet. This sets the maximum boost pressure.

The bypass function is achived by adding a vacuum operated diaphram on the back side of the valve, which pulls the valve open. As soon as the car turns over, intake manifold vacuum is created, which is routed to the diaphram and opens the bypass port. As the throttle is opened, vacuum in the intake manifold drops and the valve starts to close. The valve starts closing around 4-5" of intake manifold vacuum and is fully closed by 1-2". Since the computer has activated the SC clutch when intake vacuum dropped to 8", the supercharger starts spinning while the bypass valve is still open. The valve starts closing with the supercharger already spinning thus creating a gradual smooth transition from an open to closed intake system.

The computer also controls a solenoid valve that vents the vacuum diaphram on the air bypass valve to outside air. By doing this, the computer can cause the ABV to close irregardless of intake manifold vacuum. This valve opens as soon as there is positive pressure in the intake, thus keeping the diaphram from working in reverse and pushing the ABV valve closed more tightly as intake pressure increases. The computer also holds the ABV closed this way when there is sudden vacuum in the intake, such as when you release the throttle during a shift. This way the intake system stays sealed to the supercharger while you shift and the system does not have to re-seal when you step on the gas again. After several seconds of closed throttle (constant vacuum in the intake), the computer releases the valve and disengages the supercharger.

Interestingly, connecting the diaphram directly to the intake system, thus causing the valve to cycle open during shifts does not produce any noticable change in throttle response.

taken from here:
http://shell.deru.com/~sgn1/AW11/Scnotes.htm




i like to remove and throw the ABV away if useing a clutched s/c pulley.

[mic*]

I have just searched for a good hour in the old threads for an invaluable link that was posted one time. No luck, but I still have the printed off version here - its from a Toyota servicing handbook i beleive, and describes the operation of the SC system - diagramatically represented by the setup on an AW11 4A-GZE.

The ABV is closed at ATM pressure. The VSV (variable solenoid valve) directly controls the pressure signal to the ABV. The VSV is controlled by the ECU.

When i disconnect the clip to my VSV on my 1GGZE, the valve never opens because the VSV stays closed and the valve sees ATM pressure constantly. (EDIT: and because the volume of air is trapped in the valve by the closed VSV, under boost the valve still wont open because the trapped air compresses if it tries to open)

Feral4mr2 what is it that is "No, not at all"? From your post the only diff i can see is that your reference suggests that the ABV closes progressivly as vacuum disappears, like wastegate creep. This is incorrect as the VSV controls the valve by blocking or unblocking the pressure signal. The VSV is - OPEN or CLOSED, no in between. The VSV is not a vent, how could this be on a MAF versions without a tube coming out of the airbox - which ive never seen? The computer DOES close the valve marginally before the clutch engages, but this said to be so the intake air spins the lobes a little first to lessen the load on the clutch.

All in all, the valve made only a little difference to me on my 1g under normal conditions when it wasnt working. But when you do a long hwy drive for example, heatsoak was bad and the economy would get shit. This might be different on a 4A with an IC, but for me the answer was keep the ABV, and just plumb it straight to manifold. No more VSV, or ECU control. And the SC stays cooler.

[feral4mr2]

And the SC stays cooler.

when the ABV is open it's recirculating already heated air back through the s/c, how can this keep the s/c cooler?

Feral4mr2 what is it that is "No, not at all"?

my no not at all refers to your explaination that the vsv itself sends the signal to the ECU.

The ABV is controlled by a pressure signal which comes from the VSV.

IMO this is incorrect, the ECU sends a signal to the vsv telling it whether to open or close.
there are 3 ports on the vsv, when the soleniod is closed it breathes through the other open port that has the little filter doobie on it. (bit of useless info?)

The VSV is actuated by the factory ECU based only on revs & load. It is actuated at high revs & high load to prevent overboost. It is also actuated when the revs & load are low - basically whenever the SC is clutched off.

the ECU from my understanding over the years operates the ABV vsv based on boost/vacum, not rpm's. plus i cannot see how the engine can be overboosted when the boost level from the s/c is governed by the OD of the crank pulley, which is why i feel the ABV is a waste of added hardware. (again IMO).

This is for economy so the engine doesnt have to breathe through the lobes of the charger.

the engine still breathes through the s/c even when the s/c clutch is not activated. sure it might suck a little into the system via the ABV bypassing the s/c, but through a hole the size of a 20 cent peice it wouldnt be a great deal. the s/c free spins when it's 'turned' off, so it is still providing the engine with air.



*edit* again this is what i've figured from my own experience of playing with 4agze AFM set-up's.*

[reecegze]

So i still should remove my abv ????? Even with my aftermarket ecu and car boosting 11 psi on a afm engine
Confused to wether my abv is still working now :S

[feral4mr2]

how does your s/c get switched with the aftermarket ecu?

with a stock ECU, IMO the ABV is not needed when your running a clutched s/c pulley thats switched on/off by the ECU. i've run my previous gze in the feral with no ABV.

you have the blue ABV vsv not hooked at all. so i would say no, the ABV would not be working at present anyway.

i get a solid 14psi from ~5200rpm up in the lil feral with my 175mm pulley. no ABV operational.

[TooF]

ive always run the ABV with just a manifold reference signal, ive always unhooked the blue VSV so the abv is operated just by manifold pressure.

ive had no grief with it leaking, mine sees up for 17psi of boost with my 180mm pulley.

[reecegze]

how does your s/c get switched with the aftermarket ecu?

with a stock ECU, IMO the ABV is not needed when your running a clutched s/c pulley thats switched on/off by the ECU. i've run my previous gze in the feral with no ABV.

you have the blue ABV vsv not hooked at all. so i would say no, the ABV would not be working at present anyway.

i get a solid 14psi from ~5200rpm up in the lil feral with my 175mm pulley. no ABV operational.

Yer my ecu controlls the S/C clutch on/off My blue and brown is non existent goneski's
i might plate it up just in case ..

[Drew]

just tee it to the fuel pressure reg signal ,mine has been like that for 4 years with no dramas.

[mic*]

Firstly i never said the VSV itself sends an electrical signal. I said that it sends a pressure signal (poor choice of words perhaps) to the ABV. The VSV when it IS being actuated by the ECU's electric signal, sends atmospheric air to the ABV - from your little port thingy. When the ECU stops the signal, the VSV is off and allows the ABV to see the intake pressure. A vacuum will open the ABV.

So -> VSV on = ABV closed.
-> VSV off = ABV open.

The "revs and load" comment is also secondhand from the same toyota handbook. And since i have no manifold pressure sensor that i can find on my 1G, i cant see how the ECU could use anything but load, i imagine by TPS. The revs parameter comes into play at high revs. At high revs the ECU turns the VSV off, so the ABV is open. In this role the ABV is bleeding off some of the intake charge around in a circle. It limits the max boost, or to use toyota's words - "limits overboost"

The SC stays cooler comment is to do with off boost driving on my unclutched setup which i didnt make clear sorry. It stays cooler because whenever there is a pressure ratio accross the charger heat is generated. Pressure ratio is the MOST proportional thing to heat generation, as is simillar to a turbo. Agree?

When the ABV is closed, my SC trys to pump every available molecule of air from its inlet to its outlet. Big pressure ratio -> very hot. With ABV open, air goes round in a circle, allbeit getting a bit of heat each time, but the pressure ratio across the charger is almost non existent so heat generation is much less.

The importance of the ABV for a clutched setup, while driving under vacuum is perhaps not as strong, but simillar. With the valve closed, every bit of air that the engine breathes MUST be pulled through the lobes. Its NOT a negligable inlet restriction in my book, and the charger will get hot from it, as there is a constant pressure ratio across it.

When i had my clutch operational, i did on many occasions look at the engine free running. The belt spins, obviously, but the face of the clutch, which connects to the splined supercharger shaft does not. Never did, even up to 2000rpms. So on my 1g i know that 2000rpms worth of air can be breathed EASIER through an open ABV than by sucking it through the lobes...


Even if only for the fact that its easier than getting rid of it, i would plumb a manifold siganl to the ABV and keep it. From fuel pressure reg as said. Thats the source of mine...