Ford Zetec FIDLE, ISCV, 2 wire Idle Valve Frequency Measured

[Michael]

I don't know how many threads I've come across asking what frequency to use for Ford 2 wire Idle Control Valves, ISCVs, ICVs, FIDLE or whatever you want to call them. The answers are usually along the lines of: try 30Hz, try 100Hz or 300Hz even 3Khz I have seen, nothing definite.There are so many out there, I couldn't help thinking that someone must know an optimum frequency to operate these valves at, they are an electro-mechanical device and so will have a resonant frequency which is probably the best frequency for them and I am also sure that Ford would operate them at the resonant frequency. It is a question to which I also would like an answer. My MS1 V3 installation now has a few thousand miles under its belt and apart from a few niggles I am very happy with it and confident in its reliability. The Zetec and MS installation has needed a bit of bird's nest wiring as it has developed and now needs taking apart and re-wiring and to an extent re-plumbing. However, at this stage I have not entirely cut its ties to the old Ford EEC-IV ecu: I can swap it for the MS in a few minutes and drive on it if need be. So I decided that before I rip out the EEC-IV associated bits I would measure the actual frequency used by Ford for their ISCV. here's the answer: 300Hz:

Ford EEC-IV 300Hz Lo Res.jpg

This is with my MS1 V3 with Idle valve Frequency set at 70 under Idle Control Tab:

MS Freq 140Hz set at 70Hz Lo Res.jpg

Now the calculation shown in the Idle Control Tab: "10,000/x" makes sense: 10000/70 = 142.85 - near enough! OK so to set it to 300Hz as per Ford, I need 30 in the Idle Valve Frequency Box. In fact 30 was a bit high and after a bit of trial and error I found that 33 gives as near as matters 300Hz at the ISCV:

MS 300Hz Set at 33Hz lo Res.jpg

This may be different for other valves, but knowing Ford once they have a formula, they will stick to it. From my tests I know it applies to the following valves: 928F-9F715-AE as used in Escorts. I have one of these fitted as I have the EFI escort manifold on my Zetec, also applies to 938F-9F715-AC as fitted to 2.0 litre 1995 Mondeo.

Hope this helps someone,

All best Wishes - Michael.

[elutionsdesign]

Well done.

[john.p.clegg]

Congrats.

I don't know why but I changed mine from 70 to 33 in Jan/Feb ' 09 and its fine...

John

[jsmcortina]

One thing to note is that while this may be the correct frequency, on MS2 frequencies above 78Hz use a reduced precision.

James

[john.p.clegg]

Micheal
You are obviously a well clued-up ( and kitted out ) gent running Ms1 V3 on a Ford EEC and have clarified the operating frequency of the Idle Valve..next quest ( should you wish to accept it ) would be to sort out the standard cranking pulsewidths/afterstart and warmup enrichments and idle control settings ...and any other info you can glean from the standard EEC outputs..

Thanks
John

P.S. Was going to drop a zetec and EEC into my Lotus Elan but decided to uprate to Ms EFI instead..

John

[Matt Cramer]

We've put an oscilloscope on a couple Fords and found they run at 300 hZ from the factory. However, as James noted, driving them at a lower frequency can give you more resolution on some codes, and they will run at the lower frequency without issue. It is not clear if there is one single correct answer here.

[Michael]

Update
By the time I did the measurements above on the MS1, the engine was warm and all seemed fine - don't panic. When I came to a stone cold start this morning (10degC) the idle speed was nearly 3000rpm, so either WUE or something more directly related to yesterday's changes. More likely the latter: reducing Idle DC at lower temp to 22 sorted it all out. Also reduced the Cranking DC to 20. These, esp cranking DC, want refining over the next few days in the usual MS way of things!

Thanks for all your responses, I note James' and Matt's comments and have to say that empirically it wasn't bad at 70 (140Hz) which I had from the base tune from DIYAutotune, but I do think my install is better at the higher frequency. Specifically, during WUE when the idle valve is acive, the idle is a bit smoother, also the transition from idle to drive off is better.

John, These are questions I have pondered myself, mainly in pursuit of a snappier startup. In fact plugging the EEC-IV in reminded me how good an OEM start can be, like, "K brmm" and its off from cold. With MS its more like, turn key, count to 4 or 5 and its off. However, once started MS is far superior. So yes, one could 'scope the injectors to get the pulsewidths at startup and during warmup, but I'm not convinced it would be really helpful as the injector strategies are likely to be different, batch vs full sequential for a start. Although technically you could synch it to the Crank sensor and derive the total fuel injected per cycle and do the maths to translate that to MS. I think, at the end of the day, I'll continue to tease out the Cranking DC and Priming PW until I get the Startup perfect. (Amongst other things I have to work outside, no garage, and it can be blistering cold this time of year in this part of the world, that is, if it's not raining!)

As a matter of interest this is pretty much a bog standard 2.0Litre Zetec dropped into a 1973 Rover 2000TC (P6). Mechanical install was done 7 years ago and ran on EEC-IV until September when I installed MS.

All Best Wishes - Michael.

[john.p.clegg]

And the Seasons greeting to You...

John