For All You St170'ers....

[Guest Matt Thorne]

After reading countless (mostly incorrect) posts on countless forums about how the secretive VVT on the Ford ST170 works, and how different methods of control with systems that can't really control it properly effect the power, we took it upon ourselves to create a standalone, mappable VVT controller specifically for the ST170 Zetec engine...

 

First lets first get some recorded, proven facts out there, all research carried out by us, on the dyno:

 

 

1. The solenoid is driven by 12v (switched via PWM to ground).

2. The cam swings approximately 45 degrees, and rests 'fully retarded'.

3. It is controlled by the Ford ECU.

4. Simply driving it with a PWM freq. will not work as oil pressure/temp/wear etc will effect the VVT valves flow, and hence cam position.

5. The Ford ECU monitors the cam position in relation to the crank position and then uses a PID control loop to Adjust the PWM duty to reach the desired cam angle, looked up in a map that is defined AT LEAST by RPMxLOAD.

6. VVT actuation does not begin until at least 1300 RPM.

 

With this in mind, we devised our controller, and the hardware and cam/crank decoding algorithms so we could track the position of the cams relative to each other. Then we did a few runs on the dyno, and the graphs can be seen below:

 

The following shows CAM ANGLE in relation to CRANK (240* is resting, fully advanced is approx 180*) as RPM increases from 1500 to 7000... very interesting...

 

 

What is worth noting is that control strategies such as 'turning the VVT solenoid fully on at 1500rpm' or other such bodges are NOT going to give the results that are needed. The cam is clearly shown to fully advance and then begin to taper back as RPM increases, with some other points we have decided for now to keep to ourselves

 

With this in mind it is clear to see that our system delivers higher torque at ALL points in the rev range as we can precisely position the cam (and map it to other modifications such as exhaust and intake etc) and get THE best from the engine, and not compromise with a simple 'RPM switch point'.

 

Stay tuned for some more info!

 

 

Part 2: On the Dyno Again....

 

So now we return to the rollers, this time we are going to do some definitive testing showing what is what. We are using for this our basic OEM St170 Focus bought for this project, so lets start with a base run in OEM configuration, note the horsepower... no people your ST170 is not and never was 170bhp...

 

For all graphs, OEM is in GREEN and the changed/test run is in RED. The dotted line relates to the right axis (torque) and the other line relates to flywheel horsepower (left axis)

 

 

Fig 1: OEM VVT Control vs VVT OFF (Fully Retarted/resting position)

 

As can be seen in Fig 1, there is massive lack of power across the rev range with some losses of torque in the region of 50 lbs/ft... so that's obviously a NO GO method of setting up your VVT.

 

The next, and very common method is to use a programmable output on your ECU and turn the VVT on fully at a defined RPM, in this case we are going to go for the 'forum accepted' RPM of 2250:

[Guest Matt Thorne]

Fig 2: Turning the VVT solenoid fully on at 2250rpm.

 

This going to cost a little over £5 for a relay and of course an ECU that can do it as well as a bit of wiring, but ok, so this time we get something a little better... sort of...

 

We lack torque at the get go, and generally we see a lack of power getting proportionately worse as RPM increases... so we get rubbish peak power, and an almost OEM bottom end torque... not the best compromise, but the most chosen one when tuning ST170s...

 

So what else can we do without a mappable VVT Controller? Well, we can choose to lock the cams mechanically at a set point, some say 22* advance, some say 33*, some quote a number that is not even attainable, so its probably a good idea, using our controller to 'set' a locked cam potision, not taking into account any mapping, just hold at X degress of advance for the whole power run. Here are the sequence of graphs at 10 degree intervals of cam advance...

 

Fig 3: 10 degrees fixed advance (OEM in green)

 

Fig 4: 20 degrees fixed advance (OEM in green)

 

 

Fig 5: 30 degrees fixed advance (OEM in green)

 

 

Fig 6: 40 degress fixed advance (OEM in green)

 

 

Fig 7: 50 degrees (maximum) fixed advance (OEM in green)

 

Okay so looking at this we can see that if you are going to lock your cam into a position, aim for approx 40* advance (fig 6). That's the 'average' best, and I say best if you are willing to live with a lot less lower bottom end torque, poor idle/emissions, and a fluffy top end/peak power. Note that in Figure 3 (30* advanced) we actually IMPROVE on the OEM power output at the RPM range 5500 onwards...

 

Of course this is going to cost something like £100+ to get the VVT lockout hardware, then the time to fit the hardware, change the belt, DTI the cam angle (and the tools and know how to do so).... the list goes on...

 

What we really need to do is change the cam angle based on in this case RPM alone to give us the best of 'all' worlds. Luckily, here's a graph we made earlier of all runs overlaid...

 

Fig 8: VVT locked positions against OEM VVT (RED)

 

Now lets go along the highest torque line and pick the curve that best represents the most torque at that point/range and punch those numbers into our VVT controller....

 

We need to run (RPM -> CAM ADVANCE (degress))

0-1000 -> 0*

1000-2000 -> 50*

2000-3000 -> 40*

3000-4000 -> 50*

4000-5000 -> 30*

5000-5500 -> 20*

6000+ _> 10*

 

Final graph coming soon....

 

Remember that all of these results are based on a factory ST170 Focus running OEM management, we have simply disconnected the VVT solenoid, tapped in our system to the cam and crank sensors and plugged into the VVT solenoid with our controller. God knows what the factory ecu is doing fuelling and ignition wise whilst it loses control of the cam, but we can all agree this is the WORST CASE improvements to be had over the current methods of VVT RPM switch on and VVT Lockout using our mappable VVT controller...

 

Our controller is also 3D, so we can actually map it via throttle also, giving even more gains..... more data to follow on a nice Mk1 Escort fitted with a NODIZ Powered St170 on Bike Carbs... stay tuned...

 

The cost? £240inc. And time to fit? Well if you go with a system from Chester Sports Cars you get a fully click-n-go loom, so maybe 30 minutes to fit, and its already basemapped, so that's immediate, safe gains with no intrusion into the engines timing belt area...

[richyb66]

Is this something you're selling? If it is then really should be here:

 

http://www.rhocar.org/index.php?showforum=17 and should comply with the For Sale rules.

 

Apart from that, it looks like you've done some very good work.

[Bob Tucker]

He cant post in for sale as a communit user

[theduck]

Don't see what the market is for this? Surely you should just buy a suitable Ecu to start with instead of adding this to an alternative setup. An EC1 will give the required control for the VVT and work with OE sensors etc and can be bought for £600-700 inc all the required connectors and software for mapping.

[richardm6994]

Duck.....I think there is a market for this as I've seen a fair few threads questioning the control options for the vvt.......

 

There looks to be a fair bit of work done developing this and could be useful for other members....and who knows.....maybe some club discounts can be sorted

[richyb66]

I think there is a market for this as I've seen a fair few threads questioning the control options for the vvt.......

 

 

 

So paying £15 to join and posting it in the appropriate area might be a worthwhile investment then.

[Guest wargob]

I also don't see the market you would have to be running an old ECU not to control VVT almost all new ones do now days !

[richardm6994]

So paying £15 to join and posting it in the appropriate area might be a worthwhile investment then.

 

+1

[Guest Matt Thorne]

Well the Omex 710 doesnt control it and thats £950+

 

In fact, almost all ECUs say they control it but in fact do not support it properly (ie not closed loop)

 

It also means if you are running the ST already on an ECU that doesent, or carbs etc, you can upgrade for very little cost and get free horsepower that has been hiding from you ... Its a good market and thanks for the positive feedback.

 

I will post up once its completed, and if it is, and there's some interest I will register and offer you guys a good deal

 

Will kep you all appraised

 

Matt

[theduck]

Duck.....I think there is a market for this as I've seen a fair few threads questioning the control options for the vvt.......

 

There looks to be a fair bit of work done developing this and could be useful for other members....and who knows.....maybe some club discounts can be sorted

 

My point was those people should be being told to buy the right ECU, not to buy the ECU they fancy and splash another £240 on this. As someone else posted about an Omex ECU thats £950 + this unit at £240, thats rather a lot of money when you can buy a quality ECU for half the price that does it all properly, even closed loop, all in one unit!

[Guest zoomzoom]

This must be running with the OE variable inlet manifold, which is a bit bulky for a kit car.

 

If its proper closed loop control, and not just switching on and off as some ECU claim is closed loop control then its a good idea, but needs to be for throttle body/bodies for a kit car ,

A conversion for a tin top would work say a mk2 escort

 

Good luck with it

[Longboarder]

Lots of posts from me on this subject. Coming to ST170 from zetecs I was never happy with the omex 600 I had originally bought to run the zetecs and which I couldn't afford to replace, let alone facing the work involved in stripping the engine loom out of the car. I switched to fixed cam (cost a bottle of Glenfiddich) over a year ago with the comment that it must be better to have the timing roughly right some of the time rather than wrong all of the time (with solenoid switch-over) and it has certainly made a difference. I agree the bottom end leaves a lot to be desired. I run 22 cam degrees of advance having tried various cam timings. Incidently catcams give information that suggests total cam change available on the ST VVT mechanism is 30 cam or 60 crank deg, whichever you prefer to express it as. You say 45 deg total at one point and then picture a dyno-run at 50 degrees.

 

I'm having trouble with understanding the fixed cam timing power curves. You have run at 10, 20,30,40,50 degree advance. Presumably the ford ecu has various points where the cam advance is 10, 20, 30, 40deg and at these points the curves should coincide. Nowhere does the 10 degree curve touch the ford curve, yet you state the ford ecu starts at zero and there is no advance before 1300rpm. Shouldn't it cross somewhere? (Maybe it does in your amalgamated curves.)

Similarly the 30 degree and 40 degree advance curves are both identical at 4000 and 4500. Are you saying that 10 degree cam angle change have no effect on your engine at those points? My own rolling road operator found 2 degrees of cam angle change, 44 to 46 gained 4 wheels hp at the top but lost bags of torque lower down. I think 10 degree jumps are far to big. You must do more detail work to convince me.

 

Have you had any problems getting an ECU and your device to share the crank sensor and TPS signals? It would seem a possible problem.

 

I would love to have the VVT working properly and a simple add on unit for a reasonable price would tempt me. My engine is far from standard and the top end was impressive in a magazine RR shoot-out despite having replacement unmapped injectors in two days before. It was obviously a bit rich on the day. Getting the VVT working as intended would fill the holes in the bottom end of the torque curve. I will stay very interested but 240 is a bit much.

 

Nigel

[Guest Matt Thorne]

Lots of posts from me on this subject. Coming to ST170 from zetecs I was never happy with the omex 600 I had originally bought to run the zetecs and which I couldn't afford to replace, let alone facing the work involved in stripping the engine loom out of the car. I switched to fixed cam (cost a bottle of Glenfiddich) over a year ago with the comment that it must be better to have the timing roughly right some of the time rather than wrong all of the time (with solenoid switch-over) and it has certainly made a difference. I agree the bottom end leaves a lot to be desired. I run 22 cam degrees of advance having tried various cam timings. Incidently catcams give information that suggests total cam change available on the ST VVT mechanism is 30 cam or 60 crank deg, whichever you prefer to express it as. You say 45 deg total at one point and then picture a dyno-run at 50 degrees.

 

I'm having trouble with understanding the fixed cam timing power curves. You have run at 10, 20,30,40,50 degree advance. Presumably the ford ecu has various points where the cam advance is 10, 20, 30, 40deg and at these points the curves should coincide. Nowhere does the 10 degree curve touch the ford curve, yet you state the ford ecu starts at zero and there is no advance before 1300rpm. Shouldn't it cross somewhere? (Maybe it does in your amalgamated curves.)

Similarly the 30 degree and 40 degree advance curves are both identical at 4000 and 4500. Are you saying that 10 degree cam angle change have no effect on your engine at those points? My own rolling road operator found 2 degrees of cam angle change, 44 to 46 gained 4 wheels hp at the top but lost bags of torque lower down. I think 10 degree jumps are far to big. You must do more detail work to convince me.

 

Have you had any problems getting an ECU and your device to share the crank sensor and TPS signals? It would seem a possible problem.

 

I would love to have the VVT working properly and a simple add on unit for a reasonable price would tempt me. My engine is far from standard and the top end was impressive in a magazine RR shoot-out despite having replacement unmapped injectors in two days before. It was obviously a bit rich on the day. Getting the VVT working as intended would fill the holes in the bottom end of the torque curve. I will stay very interested but 240 is a bit much.

 

Nigel

 

Longborarder...

I know what you are saying about crossing over, but I think that the Ford ECU will be doing some 'limping' when it realises that it cannot control the cams positions, which explains this. And the lines coincide enough for what was simply dyno runs minutes apart. Some heatsoak here and there etc perhaps, but the general shape of the curve is what we were aiming to illustrate, which I feel has been very conclusive.

 

In terms of sharing signals, we use an opamp differential decoder, high impedance, so as in this case, the standard (or other ECU) doesn't know that we are 'listening in'.

 

We will be doing a more incisive run on a real world application next week, that being a Mk1 Escort with an ST170 on carbs

[Guest Matt Thorne]

Oh sorry missed this also, the 10* advance is not really seen or actioned by the ford ecu,, and certianly not at WOT (which power runs are).

 

If you have a look at the excel plot you see the ford cam positions, they all start at 20 odd degrees advanced. At idle the cam is left at 0 degrees, up until maybe 1300 rpm/.

 

The base angle is read at that point (below 1300rpm ) as 240 degrees, the excel plot top line is 220*, hence the 10 degree run is not seen anywhere, as ford dont ever run that angle.