[T3] ] Bad day at the (FI) office

[Daniel Nohejl]

Keith, 

This is what I was wondering about….the relevance of the head temp sensor across the driving experience. I was reading around on the Rennlist forums about 914 D-jet and wasn’t sure if the info about that sensor was correct for Type 3 as well.

Here’s the thing I don’t quite get: on any given day, the TS could be reading 100, 80, or 60 ohms. In my experience that has a big effect on drivability. How does one determine the baseline CHTS resistance reading to adjust the MPS to?

 In my experience over 4 motors I have to adjust it every few months because it seems that the system doesn’t   keep up with the season. I can’t imagine, though, that this was a system that needed to be adjusted 3 or 4 times  year. Hell, even a choke on a carb only needs adjusting once or twice a year!!

Daniel


> On Mar 24, 2016, at 8:54 PM, Keith Park <topnotch at nycap.rr.com> wrote:
> 
> You shouldnt be stumped, its doing exactly what I would expect.
> 
> 
> 
> FIrst off, once again... the head temp resistor is for WARMUP CURVE ONLY,
> you want under 100 ohms at running temp, way under 100 is fine.
> 
> 
> 
> Adjust the pressure sensor for main mixture, fuel pressure gives a fine
> adjustment on that, with todays NYS winter blend E10 gas you will need to go
> WAY richer than factory, if you running E15 DONT, thats much worse (Jim's
> gonna smack me, but the AFR meter will tell you what is and should be).
> 
> 
> 
> SO:
> 
> 
> 
> adjust main mixture first, with head temp sensor stock (NO resistor) use
> your MPS.
> 
> 
> 
> THEN, if you want to richen up the cold start, you add a SHUNT (parallel)
> resistor to the head temp sensor to never let it get as high when cold.
> 
> 
> 
> Once your main mixture is right THEN we look into idle issues, and remember,
> you may have fouled out the plugs when running too rich, this could be
> causing some of the odd behavior.
> 
> 
> 
> Keith
> 
> 
> 
> For fun, when I got home, I checked the resistance of the temp sensor with
> the resistor in place and it was 153 ohms. Without the resistor, it was 82
> ohms. Clearly, my 100 ohm resistor is only giving about 70 ohms of
> resistance. I know that Jim says the resistance number isn't that important
> here, but 70 ohms made a huge difference in idle, drivability, and AFR.
> Should this be so or does this point to another issue?
> 
> 
> 
> In any case, we're kind of back to where we were a month or so ago, with
> three options:
> 
> 
> 
> -keep the resistor and lean out the mixture a bit at the MPS  (back towards
> original calibration)
> 
> 
> 
> -remove the resistor and richen the mixture at the MPS (further away from
> o.c.)
> 
> 
> 
> -remove the resistor, return MPS to o.c., and do something else that I'm
> unsure of. I'd have to do something though because if removing the resistor
> made it as lean as it did today, then recalibrating the MPS to original
> would make it even more so as original is clockwise from where I am now. 
> 
> 
> 
> I'm definitely stumped!
> 
> 
> 
> 
> 
> 
> 
> Topnotch Restorations
> 
> topnotch at nycap.rr.com
> 
> http://www.a383ina68.addr.com/radiorest/main.htm
> 
> 71 Squareback  "Hothe"
> 65 Notchback  "El Baja Rojo"
> 
> 93 RX7  "Redstur"
> 
> 87 Golf  "Winterat"
> 
> 
> 
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