The V8 Owners Forum -

At the moment the fast idle on my MegaSquirt SD1 is the original EAV which only does cold start fast idle.

I'm doing a fairly major revamp shortly, and would like to change to a closed loop system.

The easy one would be a hotwire stepper motor as it bolts straight on, but others have said a PWM controlled 2 wire valve is more reliable. But of course isn't just bolt on.

Any thoughts?

Dave I would have a rotary idle valve over the Lucas stepper any day, I am referring to the Bosch style like used on BMW's etc far more reliable and more consistent in operation IMO free's up another 2 spare pins on the DB 37 too.

Anyone actually fitted a Bosch valve to an RV8 - and where did it go? The one I've seen has in and out at right angles and at the end of the unit. Can't really think where it would fit neatly.

I was hoping there might be an 'inline' type which could go where my SD1 flapperEAV is situated? Or one which could adapted to go where the hotwire stepper goes?

Any better ideas gratefully received.

Is this what your talking about, I got mine tucked under here
idle air control by jsf55 pics, on Flickr

I'll see if it will fit there. I've a feeling the SD1 throttle mechanism might get in the way. Thanks.

I came off one of the spare ports on the trumpet base.

That looks an interesting way. Although that port is in use for my autobox and heater. But the one to the front is the original for the EAV.

Been looking at this again, and none of the suggested places is ideal for my SD1.

What I'm thinking of doing is to make a plate which screws to where the stepper motor goes on the hotwire and fix it to that, with the outlet going through it into the plenum. Valve motor to the driver's side. Then a hose from the valve inlet to the existing plenum outlet beside the butterfly.
Trouble is there are a million variations on heater hoses, throttle linkage etc across the various models.

How about using a Gems plenum chamber, they use a small & neat stepper motor near the throttle plate opposite the throttle mech. Still has the same holes as the earlier plenums so the throttle bracket should still fit.

My setup:


I never had much luck trying to use the bosch type valve with resistor on one of the windings to act as a spring. My stepper motor works great.

Tom.

I'd rather stick with the original plenum if possible.

I've done some tests on the bench with the MS3, the the valve seems to work just fine using PWM. No resistor - just a diode added as per the instructions.

I've made a plate to take the Bosch valve where the stepper goes on the hotwire (over-run valve on my SD1)

What would be the best way to get a decent air seal between the valve outlet and plate? It is a pipe designed to take a hose, originally. Pipe is 22mm OD.

I wondered about using an O ring and making a second plate as a sort of sandwich for the O ring - but not sure how I'd make a suitable rebate in them to accommodate the O ring. Or just use something like hot melt glue?

Is yours a 2 wire valve?
I tried using a 3 wire valve which needed a resistor on one of the windings to act as a spring, I think the 2 wire valves actually have a spring to open or close them. Checking on MS manuals they actually don't mention the 3 wire ones anymore, maybe because they didn't work very well? Well mine didn't anyway.

I wouldn't use a hot glue gun personally for engine components, if the part is bolted and you just want to seal it can you use silicone? Or if you need the glue to secure the part as well some epoxy (two part) adhesive may work?

Tom.

The MS 3 manual does mention 3 wire valves. IIRC, the Thor used one.
My Bosch two wire has the valve spring loaded closed. PWM works rather like varying the applied voltage - it allows the valve to be opened to any position through closed to fully open.

Thing is the new valve will be pretty obvious on the back of the plenum, and I'd rather not see sealant there. Would look a bodge, to me.

On the SD1, the fan thermostat (a rod) is simply pushed in place into the rad. There is a sort of top hat rubber bush between them. That's the sort of thing that might work here - but would need to fit the 22mm pipe outlet from the valve. I've been looking at plumbing fittings since 22mm is a standard size - but no luck so far.

Here's what I've ended up with - mounted on a spare plenum.

That's a nice solution! Did you fabricate the bracket yourself?

Yes - it's just 6mm ally plate. Don't have any 'fancy' facilities here sadly - only hand tools and a pillar drill. Cut the hole for the outlet using a hole saw. Pretty tight fit, so just used some thread sealer to seal between them.