Question for CIS Junkies

[Mike Czech]

Does anyone know whether a 033 WUR can be swapped with a 017 WUR without modifying pressures? I just did it on my '77 911S and it appears to be running fine, but I haven't hooked up the pressure guages yet and looked up the charts to verify pressures, etc.

- Mike

[boyt911sc]

Originally Posted by Mike Czech

Does anyone know whether a 033 WUR can be swapped with a 017 WUR without modifying pressures? I just did it on my '77 911S and it appears to be running fine, but I haven't hooked up the pressure guages yet and looked up the charts to verify pressures, etc.

- Mike

Mike,

Are you aware that WUR-033 is for '76-'77 CIS USA cars? And the WUR-017 is for '76-'77 CIS RoW/Euro? They look identical from the outside but differ in their heating resistance. When you get a chance, measure the resistance (Ohms) of the WUR's and you'll find the difference. Both of these WUR's are usable for your engine but they have different characteristics. They have about 10 ohms difference between them.

Tony

[Mike Czech]

Tony, thanks for the quick reply. Thanks for the info. For some reason, I thought that the 017 was California, and 033 was rest of USA. Otherwise, what are the different characteristics to which you refer?

- Mike

[Paulporsche]

Mike and Tony,

See chart in lower right hand of Bosch manual. Looks like 017 and 033 have the same spec.

[Mike Czech]

Cool. That's great. Mean's I can use my 033 (once it's rebuilt) as a replacement. Thanks much for the info.

- Mike

[boyt911sc]

Originally Posted by Paulporsche

Mike and Tony,

See chart in lower right hand of Bosch manual. Looks like 017 and 033 have the same spec.

Paul,

I wish WUR-033 and WUR-017 are identical in its performance characteristics. The charts you provided is for the control fuel pressures which are very helpful. Although both use the same chart (CP versus temp.) the transition control fuel pressures from CP to WCP is different. So if you measure the control fuel pressure versus time, the chart would show the difference between the two WUR's. The key difference is the amount of time for the bi-metallic deflection to get to the same CP value because of the heating resistance (ohms) in the WUR's.

Here is a simple explanation about the difference between -033 and -017. WUR-033 will get quicker or faster from CP 'A' to CP 'B' (WCP) than WUR-017 on a given engine under same operating conditions. I have collected experimental data to prove this point and it just not so happened to read the technical bulletin.

Here is another one. If we both took a math test and both had a perfect score (all answers correct). You finished the test in 10 mins. and it took me 30 mins. Both got all the answer correct, so what the difference between your performance and mine (example)? Do you still have your SC?



Tony

[Mike Czech]

Very interesting. So in layman's terms this means that (if the WUR is to be assumed similar to an automatic "choke") that the 033 makes the fuel pressure transition from cold running to warm running at a faster rate than the 017. If this assumption is correct, that would mean that a 017 would be better for cooler climates, i.e. it runs richer for longer?

- Mike

[RarlyL8]

Generally speaking, the warm up time on all Euro WURs is longer than that of WURs built for the USA. If vacuum and Lambda functions are not an issue then a Euro WUR can replace a USA WUR in all but extreme environments such as possibly AZ or FL.

[boyt911sc]

Originally Posted by Mike Czech

Very interesting. So in layman's terms this means that (if the WUR is to be assumed similar to an automatic "choke") that the 033 makes the fuel pressure transition from cold running to warm running at a faster rate than the 017. If this assumption is correct, that would mean that a 017 would be better for cooler climates, i.e. it runs richer for longer?

- Mike

Mike,

WUR-033 has about 25 - 26 Ohms heating resistance value. While WUR-017 has more between 35 - 37 Ohms. The greater the resistance (Ohms) the lower is the current flow (ampere) through heater and takes more time to deflect the bi-metallic spring.

Tony

[Mike Czech]

Understood. Thanks much for this.

- Mike

[Paulporsche]

You're right, Tony. Actually I'm a little surprised Bosch didn't publish the time aspect along with the charts.

Depending on Mike's location and how he drives the car, the variance in time may not be an issue.

And yes, I still have Ol' Yeller. 38 years old this month. It's a 77 so it's an S, but the engine is an 80, enlarged to3.2L. Still running great!