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Rasta Monsta
Joined: 12 Jul 2006
Posts: 11733
Location: PacNW
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 Posted: Wed Dec 03, 2008 3:41 am Post subject: |
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Unlike some, our O2 sensors are single wire, and not a voltage source. The reading comes from varying resistance at different AFRs. This is why the directions for the generic sensors stress that the wire length be carefully preserved when a new sensor is installed (because wire length affects resistance), and why splicing into the line likely alters the signal reaching the lambda computer.
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Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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tconner
Joined: 16 Aug 2008
Posts: 10
Location: Flagstaff, AZ
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| Posted: Wed Dec 03, 2008 5:53 am Post subject: |
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| Quote: | | Unlike some, our O2 sensors are single wire, and not a voltage source. |
I have not run into an oxygen sensor that varies its resistance according to AFR but I will surely look into that. The following Bosch single wire sensor:
http://shop.oreillyauto.com/ProductDetail.aspx?MfrCode=BOS&MfrPartNumber=11027&PartType=291&PTSet=A
is the one I just installed on the 931. I know this one outputs a voltage because I have measured it with nothing connected to it except a volt meter.
| Quote: | | Why not just anodize or powder coat the aluminum? |
That is good idea. There are some pretty tight tolerances on the body so I would have to make sure the added thickness from anodizing would not present any problems. You are right though anodizing the aluminum body would likely be cheaper than machining it from stainless.
Viton is ethanol safe and is available in most o-ring sizes.
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ideola
Joined: 01 Oct 2004
Posts: 15550
Location: Spring Lake MI
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| Posted: Wed Dec 03, 2008 6:12 am Post subject: |
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| tconner wrote: | | Viton is ethanol safe and is available in most o-ring sizes. |
I'm not so sure on that one. I have encountered several reports of Viton failure in E85 systems. One of the reports came from a forum member here who works for Shell and is currently doing R&D on pumping systems for E85.
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Rasta Monsta
Joined: 12 Jul 2006
Posts: 11733
Location: PacNW
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| Posted: Wed Dec 03, 2008 7:47 am Post subject: |
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Well, I could be wrong. . .it has happened before. . .once!
*EDIT*
Crap, after looking around the Net a bit, I think I am wrong! I could have sworn the instructions that came with my last sensor stated the wire length had to be the same b/c the sensor varied resistance, but everything I have found supports the low voltage scenario you described.
Dang, I hate being wrong. Good thing this will be the last time for a while.
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Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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tconner
Joined: 16 Aug 2008
Posts: 10
Location: Flagstaff, AZ
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| Posted: Thu Dec 04, 2008 1:14 am Post subject: |
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Wow not even viton? Ideola, do you know what people are using for o-rings and flexible parts when they do an E85 conversion?
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ideola
Joined: 01 Oct 2004
Posts: 15550
Location: Spring Lake MI
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| Posted: Thu Dec 04, 2008 1:30 am Post subject: |
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Tom
No, I haven't found any references regarding suitable replacements in the aftermarket for o-rings. Teflon-lined braided stainless is widely regarded as the best option for flexible lines, but bruni opined that teflon was not a suitable material for o-ring type seals.
ourkid is the guy I mentioned earlier who is working on this at Shell (over in the UK). It might be worth your while to send him a PM and compare notes. He's the one who shared with me the problems they were having with Viton seals failing in different mixtures of Ethanol and gasoline. As I understand it, the problem is not so much finding an Ethanol-safe material, it's finding a material that will hold up to varying mixtures of Ethanol and gasoline; of course, E85 is a mixture and its exact formulation can vary almost daily depending on the refinery and time of year.
Coincidental to my earlier exchange with ourkid, I stumbled across an article on Oct 19th in the Oct 2008 issue of Racecar Engineering magazine, page 8, that discusses new seals that have been developed and released by Stäubli (http://www.staubli.com). According to the article, these seals were developed to replace conventional Viton seals, specifically for race cars that are increasingly demanding bio fuel alternatives. To quote the article:
| Quote: | | To accommodate the new fuels successfully, Staubli has introduced an upgraded range of seals based on perfluoroelastomer material. Connectors with this type of seal are marked JKV and are suitable for all types of fuel, including bio-fuel in concentrations from 10%-85%. |
Might be worth investigating further...
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bruni
Joined: 26 Jul 2008
Posts: 114
Location: South Africa
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| Posted: Thu Dec 04, 2008 4:29 am Post subject: |
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| Quote: | | but bruni opined that teflon was not a suitable material for o-ring type seals. |
It wasn't me, Teflon is used in many sealing applications, however I have only seen it in square section not round
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1982 931
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ideola
Joined: 01 Oct 2004
Posts: 15550
Location: Spring Lake MI
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| Posted: Thu Dec 04, 2008 5:59 am Post subject: |
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| bruni wrote: | | It wasn't me |
Whoops! My mistake, it wasn't bruni, it was jrcook320 in this thread.
Sorry bruni!
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ideola
Joined: 01 Oct 2004
Posts: 15550
Location: Spring Lake MI
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| Posted: Thu Dec 04, 2008 6:14 am Post subject: |
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Just a follow up...doing a quick search on Kalrez o-rings at mcmaster.com (as suggested by JR Cook) returns this:
http://www.mcmaster.com/#kalrez-o-rings
Kalrez apparently is a Perfluoroelastomer compound, which is the same material referenced in the Staubli article I mentioned above. We'd have to get measurements on the o-rings to price out a retrofit kit for a fuel dizzy...
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tconner
Joined: 16 Aug 2008
Posts: 10
Location: Flagstaff, AZ
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Rasta Monsta
Joined: 12 Jul 2006
Posts: 11733
Location: PacNW
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| Posted: Wed Jan 07, 2009 3:15 am Post subject: |
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Love your pressure gauge. Would it be suitable for permanent engine bay installation?
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Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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tconner
Joined: 16 Aug 2008
Posts: 10
Location: Flagstaff, AZ
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| Posted: Fri Jan 09, 2009 7:38 am Post subject: |
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Currently the gauge is not designed for permanent engine bay install. However, if we used a more expensive silicone tubing it would work just fine in the engine compartment. If we get a few more requests I will look into that.
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jrcook320
Joined: 02 Nov 2005
Posts: 67
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| Posted: Tue Jan 13, 2009 10:12 am Post subject: |
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It's cool to finally see test results on these.
ideola, Kalrez is probably the best o-ring you can buy for chemical resistance, but they're expensive. What about the aluminum body of the 925 FD?
| Quote: | | Love your pressure gauge. Would it be suitable for permanent engine bay installation? |
You can probably get away with any fuel pressure gage. I bought this one at autozone to make my own pressure test kit. I decided to install it permenantly because I like to keep tabs on my fuel pressures.
The steel fuel line is from a volvo 240 turbo cut in half with high pressure rubber fuel line clamped on. Sounds ghetto but I haven't had any leaks for 2 years.
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| '81 320i Turbo | T25, 931 CIS, 250hp, 13.92@100mph | e21 Legion Page | My E21 Videos | |
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gegge
Joined: 27 Jul 2007
Posts: 1124
Location: Sweden
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| Posted: Thu May 14, 2009 11:15 pm Post subject: |
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I am seriously considering buying one of those gadgets, anyone interested in group buy in the near future?
For some reasons, I would like to keep the CIS and with this device I do think it is possible to strech the capacity beyond 250hp by reducing the controlpressure at high boost and rpm.
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Carl Fredrik Torkildsen
924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs |
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ideola
Joined: 01 Oct 2004
Posts: 15550
Location: Spring Lake MI
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| Posted: Thu May 14, 2009 11:43 pm Post subject: |
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| gegge wrote: | | I am seriously considering buying one of those gadgets, anyone interested in group buy in the near future? |
It's not real high on my list, but I constantly think about adding one of these to the 941. So yes, depending on what discount we can negotiate, I would be interested, although I can't promise or commit anything at this moment.
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