VHPD IACV

[r10crw]

Having recieved an emerald from Hiscot (thanks again) Im looking at wiring it in in the next few weeks. The last time I did this I just removed the IACV and blanked off the pipes then used the throttle stop to set the idle, is this still the accepted method?
Cheers Craig.

[steve_weegie]

Hi Craig,

I'd certainly keep the valve if possible... Will probably help the engine idle a lot better in the Aberdonian weather system

I know the S2 IACV isn't directly compatible with the emerald, but I'm guessing the 340R VHPD has an S1 style??

Cheers,

Steve

[Mikie711]

Craig, what your talking about doing is effectively running the VHPD as if it had Jenvey DHTB's fitted. If that's the case then there are a couple of things you need to do. Dave Andrews has the procedure on his web site so to save you searching....................

"First..
Turn off idle control in the software!!!!
Make sure the engine is hot
Make sure the idle advance is no more than 5 degrees,
Slacken the locking nut on the balance mech

Then..
i) make sure there is some slack in the cable.
ii) measure the airflow between TB 1 & 2 against TB 3 & 4.
iii) if 1 & 2 are low, increase by turning the balance grubscrew clockwise, if 1 & 2 are high reduce by turning counter clockwise. If they balanced lock up the adjustment grubscrew and ensure you have 1000RPM, if they are balanced and at 1000RPM go to viii)
iv) adjust the overall idle adjustment screw if idle falls or rises too much, set idle to 1000RPM
vi) if you have adjusted the overall idle adjustment screw then make sure you re-align the throttle pot in the software immediately.
vii) go to i)
viii) Let the engine idle and go to the live adjustments screen

Look at the lambda scale and adjust the fuelling until it shows two or three bars into the yellow, try trimming the fuel up and down two or three points and note the point at which the idle starts to fall in either direction, then go for the middle point which should give a clean and reasonable idle. If the idle starts to fall when you are adjusting the fuelling *then you are going in the wrong direction*, start adjusting in the opposite direction, The fuelling is right generally when the idle is at its fastest, if the Lambda scale doesnt appear or appears way off then it could be that your sensor is faulty. If the idle speeds up , adjust using the idle adjustment screw *NOT* the fuelling or timing, reset the throttle pot each time you adjust the idle screw. Recheck the balance.

When you have the idle stable and smooth at 1000RPM and the lambda reading consistently in the yellow by 2-3 bars then the idle is OK. Reset the throttle pot and set idle control on in the software with values of 25 degrees and an update rate of 10, then all should be well.

It might take a while to go round the cycle a few times, be patient, take your time, its worth the effort.

If you dont have a near perfect idle then you have not followed the above, I have never known it to fail."

This is for Jenvey's so the balance procedure might be a bit different but the idea is the same. I did this on mine and a couple of caterhams and it works spot on, rock solid idle so much so you wouldn't know it wasn't on a plenum. If you need a synchroniser to measure the air flow give me a shout. Be happy to pop out when your ready

[r10crw]

Thanks Mike, used to have a balancer for my old MGB but havnt seen it for a long time! Ill let you know how Im getting on and if you fancy giving me a hand that would be great. With the 340 Ive got to fit a complete new ecu plug so got that from emrald this week so will hopefully get it done next week. Want to have the car running (engine) before stripping it all out to fit the gearbox, just help me eliminate any future faults.
Steve cant remember exactly but dont think the emerald is capable of controlling a VHPD IACV, think the elise ones were controlled by PWM signals but the 340 is a bipolar stepper motor.
Thanks Craig.

[steve_weegie]

Sounds very like the S2 IACV Craig - the emerald conversions that i've seen on the S2 need a bit of logic strapped onto the emerald output to control the valve. If you can set the idle on ignition alone then all well and good, else I believe Mr Iddon may have a working circuit to do the conversion

[robin]

Indeed, but not perhaps worth the bother - craig, if there are 4 wires running to your IACV then it is bipolar and not compatible with emerald. If it has 5 wires then it is unipolar and will work.

If it is bipolar then you can either do without (as per Mike's posting of DVA's comments, I guess) or you can try and fit a unipolar one plus a chopped off loom to match and wire it in.

Cheers,
Robin

[Mikie711]

Guess it's the unipolar one I have spare Craig and I probably have the remains of the loom for it as well.

[robin]

Given that you're chopping the loom plug off for the Emerald, then taking Mike's IACV and loom is the simplest way to go if you need to, Craig.

BTW, the idle should always be better on throttle bodies than a plenum, for just about any engine. All 4-stroke petrol engines will push some air/fuel mixture back out of the inlet port on the compression stroke at low RPM. With a plenum that will cause turbulence to a neighbouring port and so you get the odd misfire. With throttle bodies, the per-cylinder throttle will limit the amount of this interference, so (timing and fueling permitting) you get a rock solid idle. This will be much more noticeable on engines with wild cams, less so on engines with variable valve control.

Cheers,
Robin

[r10crw]

Just for folks future reference, the VHPD uses a PWM controlled IACV motor which has just the two wires. The emerald ECU is able to drive this also. Thanks for the offer Mike but should be ok, probably still have you round for other stuff though .
Thanks Craig