RarlyL8

Yes, the same part is used on the 450 and 560 SL series. The extra 2 ports being blocked off on the 930 application.

PorschePhD

You can also modify the fuel head for higher CFM.

UT_tech

Nathan,

I think I forgot to address your earlier question:

Quote:
Originally Posted by UT_tech
In the event of a complete controller failure the control pressure will stay put at the last value. That's one of the great features of CIS, there's a mechanical fail-safe underneath the control loops.

Could you elaborate on this for us please?

TIA

In the later CIS-KE system the control pressure is set by an "analog" solenoid which is called the EHA (Electro Hydraulic Actuator) valve. The CIS-KE controller changes the current into the EHA valve which varies the opening of the valve, which in turn changes the control pressure. In CIS-KE there is no mechanical "backup". If the EHA valve, the controller, or the electrical connections fail then the engine will stop or run very poorly. The tradeoff is that the EHA valve is much more precise and reliable than the mechanical WUR.

In CIS-K the mechanical WUR adds the ambient air temperature to the temperature of the internal heated bimetal strip. If the engine is warm enough you can unplug the electrical connector from the WUR and the engine will continue to run. It you leave the connector unpplugged the AFR will go down eventually (after a long time delay) and the next start cycle won't come out of warmup mode but the car would get you home.

When the digital WUR was designed we tried to get a comprimise between the CIS-K and KE flavors. The digital WUR varies the control pressure using a needle valve driven by a stepper motor. If you unplug the electrical while the car is running then the control pressure will remain frozen at the point when the controller was unplugged. The stepper motor stops stepping and the force of the motor magnets holds the needle in position which keeps the control pressure constant. In this case the AFR would continue to be regulated by the mechanical system albeit at the value of the "frozen" control pressure.

nathanUK '81 930 G50

That makes sense, thank you.

How does the UTCIS sense temperature?

UT_tech

The temperature sense is again a combination of the new and the familiar. There is a temperature sensor inside the controller box which accurately measures the ambient air temperature inside the engine bay. This sensor is attached to a heater and the heater/sensor sits inside a small mass of plastic. When the car starts the sensor heats up the mass and the thermal intertia keeps the sensor hot for a delay time after the car is shut down. This delay is temperature dependent. Thus the engine goes back into warmup mode sooner in cold weather.

This is important to note because some installers have asked us if it's OK to lengthen the wire bundle and locate the controller inside the car. The controller has to be inside the engine bay.

We used to have the temperature sensor on the body of the WUR itself but we ran into noise and reliability problems. The ambient air temp sense is more than accurate enough for the cold-start cycle so we've kept it.

JBL930

What happens if the unit fails and holds the needle valve at a high control pressure, say when you're cruising, and with you being unaware of the failure with the unit you then proceed to drive the car hard, wouldn't it go lean and detonate?

Ag02M5

I'm guessing running an AFR gauge in the car at all times is about the only option.

Would be nice if you could force the car into limp mode in such a situation. Another thought is to add some sort of triggered kill...but that could get hairy depending on where it happened. But I would prefer some protection in this case myself.

RT

UT_tech

I agree, the worst case would be if on race day the engine is idling and at that very moment the controller stops regulating. The idle would not change and you would not notice anything until you gave it full throttle. You'd see the AFR rise almost immediately under full throttle, whereas with the unit regulating the AFR should go down. An AFR gauge is a very handy little piece of gear.

A triggered kill is an intersting idea in general for any modified 930. Perhaps a programmable condition of boost pressure and AFR? With an idiot light just below the kill threshold?

JBL930

Is it not possible to make the unit go into full enrichment position if it fails? It would be WAY better to have the engine bog down over fueling than to see it go lean at WOT!!!

Ag02M5

I like that idea! Give this man a prize.

JBL930

An AFR gauge is undoubtedly necessary for tuning and logging AFR whilst on the road, please do not even dream that it'll give you enough time to prevent detonation, BTDT.
Once you've ascertained that your injectors are all giving equal flow, and you've made every possible attempt to get the best from your fuel head (IA mod or whatever) then you need to be in control of your control pressure, the WUR does this in a safe way by wasting a lot of fuel (crude but functional), the UTCIS unit looks like it can do it in a different realm all together, i'm a believer, i really am.
I am just concerned that you can do some gentle motorway/freeway cruising for a few or a few hundred miles and the unit will freeze at the cruise setting, then you boost away like the mad bastard we all are when you're feeling that way out, and you're going to go lean and melt down.
There is a problem here that needs addressing, one of these units is going to fail, it's the law of averages, if it fails and dumps every available drop of fuel in then the car will bog to a stop (Option A,B and C), if it doesn't then you're in the lap of the Gods..............

Ag02M5

zeitronix is an option with the programmable trigger to sound an alarm when afr is out of whack. might be quick enough to save meltdown.

ThunderC4S

Does the UTCIS have an altitude compensation sensor/circuit ?

UT_tech

Yes it does. You might have noticed that there's a altitude setting in the PC software under File, --> Settings. That's setting is there to work out the differences between the absoute values reported by the UTCIS over the data link and the gauge value displayed by the PC software. The UTCIS knows what pressure is at altitude but a laptop doesn't!

WERK-I

Steve,
Thaks for all your support. Quick question; was the fuel head in your test vehicle have the black fuel head(Euro) or the silver(U.S.)?

Dave