[T3] Bad day at the (FI) office

Keith Park topnotch at nycap.rr.com
Tue Mar 29 16:45:16 PDT 2016


" you're saying that below 100 ohms just registers as warmed up and it
doesn't matter if it's 99 ohms or 1 ohm.'
YES!  thats the jist of it, so long as it gets below about 100 ohms hot,
87 sounds just right!

Ray is a smart guy, but he has holes in what he knows, he doesnt (or didnt
when I conversed with him a few years ago) know that the E version of D jet
that the T3's got even existed!  E version in the T4 and other worlds was
basicially like our D version (70-1).  Ray is also incorrect on the effect
of small vacuum leaks on the system and how the injectors react to fuel
pressure.  I calibrated a stock D system to built T4 2056 for my Square a
few years ago, I tried his suggestions, each and every one, and some were
good while others led me nowhere, in the end...  the combination of big
engine, light flywheel and light vehicle were what my speed transition
problems were at 1200 and 1800RPM, you can feel the issues with a stock
motor but when you double the HP and torque they become unreasonable and
these transitions werent worked out of D jet till the T3 E version came out
with the new pressure sensor.

When the engine is basically at temperature, oil 180F the difference in
mixture you want between that and 220F when the engine is on the high end of
temp is negligible, and this is what I found when doing my calibrations,
that head temp sensor is there so it wont stall at 70F or below, your
pressure sensor and pressure switch do the hot mixture adjustment.

25.8 on NY E10 is perfect IF your cruising at 70, if your cruising at 60,
its a bit low. Id rather see it a tad rich than too lean.

Dont worry about idle AFR, its relatively meaningless,all that matters is
how smooth the idle is, the numbers are relative, there is no load and your
sensor is in the wrong spot for the low exhaust flow at idle anyway.

900RPM is excellent setting for idle.

Timing NEEDS to remain consistent during calibration, get a ventilated set
of points in there, your dwell and timing wont wander with ventilated
points, Napa still sells them, I think they are erlich?  Id have to look.
your fuel pump switch wont hurt the points, neither will keeping the
ignition on, you just got cheap solid points in there.

YOur making good headway and discovering important little things,  and
its good to try things, maybe you will find out that the early brains react
more to resistance at a lower value than the later ones do, but the early
systems werent quite as stable either and they may have done some correction
on that in 1970, that I dont know.

Keith




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"
 
-----Original Message-----
From: type3-vwtype3.org [mailto:type3-vwtype3.org-bounces at lists.vwtype3.org]
On Behalf Of Daniel Nohejl
Sent: Tuesday, March 29, 2016 7:16 AM
To: type3 at vwtype3.org
Subject: Re: [T3] Bad day at the (FI) office

> the ECU really needs to see below 100 ohms (approx) to go full lean, (no
warmup enrichment) otherwise the pressure  sensor wont track properly.
> below 100 and the ECU essentially sees it as a short.  Many different
sensors were used but their cold resistance was the difference, so it
changed "how much choke" your engine had at a given cold temp.

Well, on Sunday my sensor read 87 ohms without the resistor so then wouldn't
I need a resistor in order for the ECU to not read the sensor as a short? Or
am I misunderstanding what the effect of the ECU reading the sensor as a
short would be? In other words, it sounds bad to me but perhaps you're
saying that below 100 ohms just registers as warmed up and it doesn't matter
if it's 99 ohms or 1 ohm.

> adding a shunt resistor mimic's this, but adding a series resistor gets
you over 100 ohms and richens up the hot mixture, this can mask the real
problem and is not a good way to adjust hot mixture as then the hot mixture
can wander somewhat and you dont want that.  These sensors were just for
gross cold warmup adjustments.. they are not that accurate or linear.

Ray Greenwood has been telling me something different for the last few
months now..at least since November when I first put a resistor inline with
the temp sensor. He says that the CHTS shouldn't read below 70 ohms because
then there's no room for it to offer any additional enrichment on, say, a
hot day in August at 70 mph on the Thruway. In other words, he suggests that
the CHTS continues to influence the mixture well after warmup. I'm not
really sure which is true: either it does or it doesn't (or maybe it partly
does or partly doesn't). As mentioned, I can use a variety of low ohm
resistors and see what effect that seems to have on the AFR at idle and
while driving after warm up. 

Anyway, in general, things seem to be better. We went away over the weekend
and on the way out of town, we leaned out the MPS a wee bit closer towards
its original position. Our highway cruise AFR is kind of lean..anywhere from
14.5 to 16.5 but our MPG over the 260 miles was a modest 25.8. I imagine if
we were too lean, our MPG would have been much higher. 

Toward the end of the trip, I started noticing that the idle AFR went back
to rich even though we hadn't touched it again and that the idle sounded too
high. When we got home, we took out the dwell meter and timing light. First,
the idle was at 1020 rpm so we brought it down to 850 but it was unstable
and hunted slightly so we brought it up to around 900 which is where it
seems happiest. We noted that the dwell had changed from 48* to 52* in 1600
miles. I've never had that happen before. Also, the timing was a few degrees
advanced..closer to the second timing mark than the first. We tried to reset
the points but there was such a big tit on one side that it was hard to get
the feeler gauge through so we just put in new points and re-did the timing.
Once we did that, the idle AFR went from 11.5 to 13. Seems like the advanced
timing was messing up the MPS and the a/f mixture. 

I've yet to have a set of points go bad on me in only 1600 miles.
Admittedly, I only have about 70,000 miles of VW driving under my belt but
still..Part of me wonders if repeatedly having the key in the ignition in
the on position while toggling the fuel pump prime switch hastened the death
of these points. Maybe I can power the switch from an always hot fuse and
see what happens?


_______________________________________________
VWType3.Org mailing list - type3 at vwtype3.org
To unsubscribe or change subscription options, visit:
http://lists.vwtype3.org/listinfo.cgi/type3-vwtype3.org
If you need more help, contact: gregm at vwtype3.org



More information about the type3-vwtype3.org mailing list