Electronic BOV for <$100

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Kimmo
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Electronic BOV for <$100

Post by Kimmo » Wed Jan 09, 2008 5:30 pm

To do this mod, you need to grab one of these kits from Jaycar for around $20.
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Basically, it looks at the signal from the TPS, and opens the BOV for a predetermined time when the throttle snaps shut.

The assembled kit:
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Pretty easy stuff; even if you've never made anything like it, you'll be right as long as you can solder, and you make sure you're putting the right components in the right way...

Slight mod here; since we don't have a TPS, this is a voltage supply for a retrofit.
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The top right of the black wire is a regulated 8V supply; the two solder pads indicated by the screwdriver are terminals, one of which is spare but the track between them needs to be scratched away.

Here's the idle switch with a nicely-placed hole in the cover.
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It doesn't matter if the hole's a bit big or whatever. Notice the hole in the switch itself is almost the same as the ones in some volume knobs... : )

Go the hack on the throttle spindle.
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You need to make some room in the switch hole for the potentiometer shaft.

10k&#937; pot mounted in place. The shaft needs to be trimmed pretty short... a single layer of electrician's tape gives it a snug fit in the hole.
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For peace of mind, I went a bit OTT and dismantled the pot to remove the sticky shit (soaking in solvent won't do it) in order to free it up, but that's prolly unneccessary...

Irrigation solenoid - $40-odd from a plumbing supplies joint.
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Bit of radiator hose for the curve. In hindsight, the reducer on the outlet was prolly a mistake

Inlet pipe modded to suit.
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I reckon up near the throttle is prolly the go

TPS wired up:
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Short black wire is obviously grounded; long black wire goes to that 8V supply, and the green wire is the signal.

BOV in place
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It's powered by juice I pinched from the removable link to the reverse light switch, which also powers the the circuit itself, since it switches off with the engine.

Circuit inside a zippy box:
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Green and black wires are the TPS supply and signal; red and black are power and ground (I soldered it onto the ground eyelet on the plenum), and there's a couple more for the solenoid. Once it's all together, you just tweak a little trimpot to open the valve for as long as you want (about a second or so, I guess), then you adjust another as you flip the throttle to get the sensitivity right.

BOV plumb back:
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The idea with the reducer and the skinny hose was to get some velocity happening, and squirt it into the inlet of the turbo...

It lines right up...
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Problem is, I can't even tell the difference with the BOV disconnected, so I guess there's too much backpressure going on, or the solenoid itself is too restrictive...

I'll have to get a straight outlet barb and run some long hose the same diameter as the inlet through the window to see if the solenoid's any good, I guess... how hard should a blow-off valve blow?
A more expensive item may be necessary, but for now I'm blaming the skinny tubing.

I guess my turbo's prolly having an easier time of it, at least

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Panda_ET
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Post by Panda_ET » Thu Jan 10, 2008 6:15 pm

not wanting to be a Kent but what are you expecting to feel from it? to be deadly honest with a turbo that size you wont feel anything. Mine felt laggier after snapping throttle back open with bov connected. The bov (for that lag feeling between shifts) only made a difference on the T2, the T25 preferred performance wise to have no bov at all. Normal bovs dont expel much air anyway Id say yours pumps out just as much.

tho you can rest easy that your turbo is being saved :P
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Kimmo
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Location: Footscray

Post by Kimmo » Thu Jan 10, 2008 8:24 pm

I would expect it to depend on little more than PSI and the volume between turbs and throttle, myself... with my lower turbs and modified inlet pipe (no cooler) I'm still only looking at 2.5-3l @ 8PSI, but I'd expect to hear a bit of a puff...

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Kimmo
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Location: Footscray

Post by Kimmo » Tue Jan 22, 2008 8:09 pm

Here we go; it's not even working.
j0of wrote:those solonoids won't work for air, they have a little magnetic driver inside that requires water to come through a very fine hole to release, air wont fill it out it will just force past it..
So maybe I can figure out some way to mod the fucker for air...

In the meantime, You could do this with something this... dunno what they cost, but it looks pretty similar to my irrigation solenoid.
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