re: Homemade larger HFM tube, was fuel pressure regulators.

[jkerouac@xxxxxxxxxxxxx]

re:  Homemade larger HFM tube, was fuel pressure regulators.

Can I point this thread in a related direction?

What oem fuel pressure regulators from other models or euro spec engines
can be swapped directly into an E36 //M3 (OBDII), us spec?

I've seen Dinan and others list higher 'special' fuel pressure regulators
in Euro HFM conversions, but these are only other factory fprs form 
other models.
Of course they won't tell which model unless you buy the parts.

So if someone would spill the beans on what to plug into my 97 //M3, I'm 
sure others would
take interest too.

Btw, purpose is to match the increased airflow with a larger HFM tube 
that I made.
     Seeing Dinan's beautiful craft$man$hip on larger tubes for the 
//M5, it seemed worth a try to make a new tube for HFM sensor on what I 
have.
I used 3 1/4 inner diameter plastic pipe and the rubber of a 3" plumbing 
clamp coupler.  this is 3/8 inch larger than the inner diameter of the 
factory tube.  The Euro HFM is supposed to be 1/2 inch larger.  Based on 
dyno results of a Euro HFM car, the cost of a Euro HFM conversion with s 
$norkel, plus what's needed to adapt it to your throttle, and either the 
euro airbox or an aftermarket $norkel, the larger HFM gives a definite 
improvement, but the co$t is not even close to justifiable.  Here, $8. 
is getting me a significant portion of the increase other spend $$ to 
obtain.
To adapt my new tube to the factory airbox, stretch the rubber out over 
the outlet from the air filter box, and over the inlet to the new tube.
The tubing fits just barely into the original throttle body boot. 
 Silicon spray helps a lot to squeeze this together.
You will need to use three sheet metal screw to affix the sensor from 
you HFM to the new tube.
The engine side of the sensor screws flush to the tube.  The electrical 
connector side of the sensor will prop up on the tube, leaving a gap.
     I used Kampel  "SeamFil" brand No. 940 Plastic Seam Filler to fill 
the gap.  Available at most electronics supply houses.  I chose this 
over silicon because it flows but doesn't run when applied, rapid dry 
time, and that it dries hard rather than squishy as a blob of silicon 
does.  Before filling the seams, leave the three screws about 3/4 turn 
loose from where the sensor is fully snug.  After you have built up the 
full seal between the sensor and the tube, let it sit for about 10 
minutes.  Then tighten back down about 1/2 turn on the screws.  1/3 hour 
later another 1/4 turn.  Use the engine side screw to aligh the sensoe 
element exactly centered in the new tube.
     Testing it out:
It took a few tries at starting, stalling, and restarting for the ECU to 
get the idea of the larger tube.
First I left the air filter box off to see if I would get a Check Engine 
light for over lean.  I did.  The original tube did not, so maybe I was 
onto something.  With the air filter box back on, a few cycles of 
starting and shutting the engine later, the light went out.
     Road testing:
     No Check Engine light for 20 miles in mild driving, moderate revs.
Took to redine in four gears, felt good.  Subjectively, the power band 
felt to have increased and pulled better into the mid 6000 range.
     According to the stopwatch, 60 to eight times in third are slightly 
increased, possibly half a tenth of a second.  I'll wait to get 100 
miles of driving fo the ECU to fully adapt to this.  Then time again. 
 Since 60 to 80 does not get the engine into its top rev range, I'll 
wait to the next dyno day to get actual numbers versus a recent test 
with the stock HFM tube in place..
     To see if there was any leaning out or hotter combustion chamber 
temps, I also pulled a couple of spark plugs, and they look the same as 
before.

     Flame away at me if you will, or give it a try if you're curious. 
 For $8., an Exacto Knife blade, and a few hours work, its worth the effort.

One negative is that the idle is slightly wavery occasionally.  Doesn't 
bother me, it might bother some of you. A washer with a smaller size 
hole constricting the inlet from the throttle body boot to the Idle 
Control Valve inlet tube ought to take car of that problem.
Enjoy,

'jk

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