BOV on 4AG-ZE (seriously)

[Ben Wilson]

CALM DOWN, I'M NOT A WANNABE RICER!
I have no interest in whooosh noises or anything, but I'm trying to flesh out an idea here.

My custom inlet setup had too much distance between the throttle body and the engine making idle control impossible. I'm currently running a second throttle body just before the plenum with a cable joining the two TBs. Now it idles nicely, but I'm not happy with the throttle feel and there is a lot of junk in my engine bay...

I was talking to a friend about it and he asked why I didn't just ditch the pre supercharger TB and fit a blumb back BOV. I can remember thinking about this idea and discounting it, but I can't for the life of me think of why now.

The only thing I can think of now is that a BOV mightn't have enough flow capacity to carry all the air a SC12 will deliver on full song, but it should be big enough to vent the pipe and intercooler. I can't see why a cheap e-bay external wastegate couldn't be adapted and wastegates can flow a lot of air.....

Can anyone tell me what's wrong with this concept?

[nb86]

nothing wrong with the concept, but with the relatively high boost which would be available on narrow throttle opening you may have problems with the valve opening at unwanted times. im running a gze with a front mount and big cams, and after some advice from these forums and using the zero throttle map on the haltech ive managed a good idle with only the factory toyota throttle sans idle valve. its a little high (950rpm) but im happy. alternatively try the commodore stepper motor route, i haven't tried it personally but it works by all accounts.

[Ben Wilson]

Bear in mind that I could get a normal ZE to idle, it's just that with my large plenum, I think I've pushed it over the edge (I'm already using a Commodore idle motor).



The supercharger is switched by load, so I don't think I'd be getting too much boost at small throttle openings.

[Hen]

I've thought about it a bit too, and I feel that a reasonably sized blow off valve should be able to cope. However I've never heard of anyone doing it, so it looks like its a case of try it and see.

Even if the blow off valve is a bit too small, it will just mean that there is still a few psi of boost in front of the throttle plate. Hopefully not enough to cause things to bend.

It could be annoying during those times when the throttle is only part open, but enough so that the SC is switched on. The BOV will be venting something and probably making annoying noises, even if it is plumbback.

If you do go ahead with it, let us know the results.

Hen

[Valkyrie]

Hi,
Have you had a look at the recirculatory valve on the Eaton M90 that Commodores use? One of these might fit the bill.

Cheers

[roadsailing]

the point of fitting a BOV is to get rid of all that crap.

the supercharged V6 commondore motor needs a bypass valve because it isn't clutched, and it has the throttle body before the supercharger as per the factory 4AGZE setup.

[Valkyrie]

Hi,
Commodore set-up-
T/B - E90 - Engine
E90 has no clutch (Always blows air)

Ben's proposed set-up-
sc12 - T/B - Engine

The sc12 has a clutch, but it would not last if it switched on and off every single time there was a gear change, less throttle etc. This is the way Toyota has them set-up from the factory.
This would be the condition that the Commodore recirculatory valve would work well under.
Ben also said that he wanted no whooshing noises..............

Cheers.

[oldcorollas]

there was some discussion of this in the twin charge thread, and also on performance forums on a related thread abotu twincharging and supercharging.

one of the guys suggested that he was able to use an external wastegate, (TB after SC system) to regulate the amount of boost between the SC and the TB. Off the top of my head, i can't remember how it was done... i believe that there is a company (mayeb whipple/autorotor in the US?? Ken Bell?) that has specific wastegate style recirc valves for even very large SC's, so what you are proposing has been done before.

there is really no advantage to running a plumbback BOV, except for the filtered air argument.. and assuming that you are using MAP tuning, it may be better to vent some of this hotter air rather than recirculating it.

the main drawback is noise, and the main concern is that it will not flow enough air when you close throttle at high rpm and the SC is still engaged... with the prob being high pressures in the piping (and excessive strain on SC belt)

however, if you had some kind of pop-off valve to vent quickly above certain pressure, in conjunction with an external gate, there's no reason it would not work effectively...

also, your moderation of boost pressure will be worse, unless you have the wastegate boost referenced to throttle opening or similar.. an on/off boost situation may not be so good for driveability (unless you could set the wastgate to hold a max pressure and then use TB to alter amount getting in, but then you have higher mech losses)

[Ben Wilson]

I think I've got a nice solution worked out.

I was worried about what was going to happen at part throttle/low boost. It looked ilke balancing the springs was going to be a ral PITA, so I started thinking..

Who about if I hook up an electric valve like this one, and also hook up a simple electronic timer to the supercharger trigger line.

I'm thinking about actuating the valve with the trigger wire (before the timer).

That way, when I get off the throttle, the supercharger will still run for a couple of seconds or so (less clutch wear, less lag), but any excess air will be vented out the valve.

At low load (SC off), the valve will be open allowing the engine to work through a shorter inlet path completely bypassing the supercharger.

The instant the supercharger engages, the valve shuts returning things to normal.

Does this sound like it will work?

[takai]

It does, the only thing i would be considering is making the timer long enough that you can get between gears without the charger clutching on and off.

[TooF]

i think its whipple that supply/use a recirculating bov. upspro from www.mr2oc.com fried one of his whipple chargers by using the toyota abv which simply dosent flow enough for the better twinscrew charger (unclutched).


http://www.whipplesuperchargers.com/...sp?ProdID=1210

*edit*

this obivously isnt going to be quite the cheap option that an ebay wastegate will be but quite possibly its a *better* or at least more researched solution.

[Ben Wilson]

They just look like a butterfly valve (I assume), triggered by a vacuum actuator.

I'm leaning heavily towards the electric valve in the Autospeed article now...

[GTtwin]

Would this concept mean it becomes a "suck off valve"? Sounds a bit rude actually.

[Ben Wilson]

Nah - It will both blow and suck

[WindeX]

Hmmmm that sounds like a awesome idea. Because I am looking at running a SC14->I/C->TB->3sge, which would be the most simple solution for me, but the thought of moving my TB was making me cringe a bit, probably get better performance that way, but would like to charge it first. I'm getting excited again... Anybody see anything wrong with this idea?