upgrade DME with SW chip - a conundrum

[larrym]

I'm trying to figure out which S.Wong chip to order for my '89 930/25 9.5CR motor with a 28-pin DME that does not show up in the Redbook

background: this is a classic "compiled parts" project
this is in a 914/6 - 1-5/8 headers, 911 euro sport muffler (2pipes-out); no CAT, no 02 sensor connected (but do have ports in my header outlets - used 'em for tuning Webers a LONGTIME AGO); DME harness has the round 3-prong connector (for heated sensor);

DME is a 911.618.111.20 - (-082) - it does not appear in The Redbook

this DME came out of a PCA race car and had a chip in it marked "930/26" on a PCA-race-certification tag covering up the oem chip number

- my Redbook says 930/26 - req'd 93AKI - 98RON gas - which i can't get - so i just gave up on the idea of running it on street - I sold that chip cheap thinking i could not use it

- i did test run that chip in my car just to validate it worked, but can't recall if it "pinged" on 91 AKI gas - my current research suggests that 930/26 engines were 9.5 CR just like my 930/25 - so it might have been OK to use ? or maybe - the euro /26 chip simply had a more aggressive timing curve which is why it req'd 98 RON ??

(ah, well...... )

911Chips site shows both USA & Euro (non-02/CAT) chip choices and says the euro 930/26 is "high compression" - but i can't find any confirmation that it is above 9.5CR (the RoW 930/20 is 10.3)

Steve suggests i should just pick the USA version 91 AKI chip and run the 02 sensor on one bank - that idea is based on a "stock" usa DME 911.618.111.14 oem for 'w/CAT' profile; he suggests that it would generally perform better/cleaner if connected thus, than disconnected; he also writes that leaving the 02 disconnected would not be an issue above 5000 rpm (which i rarely see)

so my question(s): -what is my xxx .20 DME ?

if it's a RoW 930/26 DME, it would be a non-02/non-CAT profile,

second question: were 930/26's 10.3 or 9.5 CR - or both?

? why not buy the "euro" 930/26 chip for 91 AKI, since SW lets you choose which octane, and just forget about the 1-bank 02 goofiness?

??

all ideas appreciated

p.s. - am currently running a 02-delete aftermarket chip - it runs strong, but tends to be a bit fuel thirsty - compared to an 050 DME with the "-302 chip" which SW has written is one of the better oem chips ( i have 3 DMEs - never know when ya might need a spare )
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[Elombard]

Subbed

Can you send the DME to Steve and let him figure out the best program for your needs?

Interesting that he would rather see the O2 connected. I was hoping to go with out when I get a chip. One less 30 year old part to worry about. I kind of figured the 02 was just emissions related - not an issue in my area for a 84

[Quicksilver]

The DME is inconsequential. It is either 24 pin or 28 pin and that can be altered and they are interchangeable. The chip is the difference in how it works.

The real question is what you have in the engine. If you have a higher compression motor and different cams you need to know it so you can maximize the performance and avoid damage from detonation.

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The O2 sensor doesn't degrade performance as is often thought. It keeps the engine running in a narrower air-fuel ration range which of course will improve emissions and fuel economy. When you mash the gas pedal the engine management goes from "closed loop" to "open loop" which means it is just running from the tables in the chip and it ignores the O2 sensor.

In other words it means that if you have the O2 programming in the ECU and the connections on the exhaust you might as well run it.

[DRACO A5OG]

Just go with Steve's suggestion. He has never steered me wrong.

[larrym]

some days i forget to google - or forget to google the "correct phrase"

here's a slew of info about my DME & orig'l chip

the 930/26's were same 9.5 CR as USA 930/25's - not "high compression" as in 10.3 930/20

https://www.google.com/search?q=911.618.111.20&ie=utf-8&oe=utf-8

excellent summary of 930/26 variants here - PLUS - report on using the SW chip
Difference in compression on an US and an Europe car? - Rennlist Discussion Forums

930/26 was an '85-'86 3.2 variant - made 231 hp vs 217 hp of USA 930/25 - on same CR - was the DME/chip & no-CAT the only difference?

note - the 930/26 is listed as able to run either no-lead or leaded fuel - that makes sense b'cuz there is no 02 sensor to be contaminated by the lead

- which means one could run hi-test leaded race gas at the track with this setup if desired (in my racing days i found that my 2.8 "ran better" when using leaded fuel at track)

lightning wrote: "from -87 they have the same compression but a different DME setup.
I have a US car and living in Sweden I have removed the cat and replaced it with a cat bypass, but I think I would have been better off with a premuffler. I've kept the O2 sensor and replaced the chip with a new one from Steve W. The car runs excellent except for a little rich mixture"

here is the specific DME: at a euro (NL) shop Porsche 911 0 261 200 082 911.618.111.20 0261

so - it looks to me like i probably have a 930/26 RoW euro spec DME - non-CAT Non-Sensor - it was in fact setup for F Class PCA racing - photo below

I'll talk more with Steve, but it looks now that i should order the 930/26 euro chip for 91 AKI octane since he provides that option,- and just forget the CAT/02 stuff - good news!

another great link here for ID'ing all our 911 engines: Fahrgestellnummern Porsche 911

p.s. - i know about the FRWilke opinion - got one of his 911PowerProm chips - it was a waste of $$ - the damn thing had a super-aggressive timing curve and pinged like crazy on 91AKI - still got it if any one wants it cheap & wants to run race-gas (he no longer adverts 'em FS)

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