e30 M3 minor rust repair.

[xworks]

vacuum pipe for the fuel pressure reg. coloured red below to make it
a little easier to see........



So with the plan to rob my vacuum signal at the same point the easiest
way to do it was change the little plastic 90 degree elbow for a "T" piece......





Fuel pressure reg. gets to keep it's signal and I get my new signal for
the Map sensor, everybody's a winner.......







Next up on the "shit to do" list was sort out an air temp sensor.
As well as knowing how much air is going into the engine the ecu also
needs to know what temperature the air is. Colder air will need more fuel,
warmer air less, and the spark timing will differ also depending on the air
temperature.
On the original set up on all e30's the air temp sensor is built into the airflow
meter, so unless I rigged up some sort of bluetooth jobbie to help the airflow meter
in the rubbish bin communicate with the ecu something was going to have to change.
Below is the solution..........



Its a little Bosch air temp sensor. Basically the probe end of the sensor
is fitted sticking out into the incoming air to the engine. The ecu sends down
it's usual 5 volts to the sensor and the voltage travels out into the sensor where
it meets a little variable resistor. This little resistor changes resistance depending
on how hot or cold it gets. Cold air coming into the engine the resistor cools down
and has a high resistance, as a result only a little of that 5 volts makes it through to return
back out the other pin on the sensor and back to the ecu.
Likewise, with warmer air been drawn into the engine the resistor heats up and has
less resistance, as a result a lot more of that 5 volts makes it back up to the ecu.
So now the ecu has an accurate way of measuring the temperature of the incoming air.

With all that said, obviously the sensor needs to be mounted somewhere where it's
measuring the actual air been sucked into the engine, so, a quick rummage around in the
spare parts box came up with a female fitting the same size thread as the sensor.......



Once the fitting had been filed down to an appropriate size a similar
size hole was cut in the intake snorkel..........

[xworks]

Ok, deep breath........
The reason I say it's not 100% necessary is that the vast majority of people
running aftermarket management systems on this engine seem to do so perfectly
well with just the throttle pot for calculating the load. However there could be some
benefit to having one of these as well, maybe, I don't know, time will tell.
Here's the short version of what it does and how it might be useful.

Like almost every sensor on the engine the ecu sends 5 volts down to it and
watches what voltage comes back and then alters the fuel and spark accordingly.

What the map sensor does is measure the vacuum in the inlet manifold. When the
throttle is shut with the engine ticking over the pistons are still travelling up and down
trying to pull air into the engine and the result of this is a fairly hefty vacuum on the
engine side of the throttle butterfly. As you open the throttle air starts to rush in to fill the
cylinders and the vacuum drops the more you open the throttle. So by using a map
sensor to read the vacuum in the inlet manifold the ecu can get a pretty good picture
of how much air is actually entering the engine, which is what it wants to know
to do it's calculations. In fact Map sensors are used on a huge chunk of mass production
cars to do just this instead of throttle pot's.

So why the fu*k am I using a throttle pot then?

Well, Map sensors work grand when you have a nice standard big fat manifold with one
single butterfly. The suck, suck, suck of each cylinder is evened out as one big suck in
the nice large chamber of the inlet manifold. As a result of this when you tee off a little signal
pipe to the map sensor to read the vacuum, you get a nice clean signal as the pulsing effect
of each of the four cylinders sucking at different times is smoothed out in the open space
of the manifold.
As the S14 engine has individual throttle bodies this presents a bit of a problem, tee the vacuum line
into just one of the throttle bodies and the Map sensor has a bit of a mickey fit. Instead of getting
a nice smooth vacuum to read it's now jumping all over the place as the one cylinder it's now reading
off is sucking then nothing, then sucking, then nothing etc. etc.
I'm hoping this problem will be overcome a little at least by where I've chosen to take a tee off
vacuum pipe for the map sensor, but we'll get to that in a minute.

Before that it's probably worth explaining why the hell I'm going to the extra effort of fitting a Map
sensor in the first place. One distinct advantage a Map sensor has over a throttle pot is at very
small throttle openings. The type when your just crawling along in heavy traffic and barely pressing
the accelerator or cruising along in a high gear with the throttle barely pushed. In a car thats to be
used as a daily driver as opposed to a flat out rally/race/track car, the more accurate the ecu can sense
whats going on at these small throttle openings the more responsive it can be to adding just the
right amount of fuel and spark timing to give a smooth drive. And when it comes to measuring how much air is entering
the engine at these low throttle openings the Map sensor has the upper hand over the throttle pot.

So, the plan is to use the throttle pot as the main source of info for the ecu to work out the
incoming air but also send it the info from the Map sensor as well in the hope's that using
both sensors it'll be able to get a more accurate idea of whats going on and maybe result in
a smoother driving engine.

Or, maybe it'll all go tits up and I'll end up fu*king the Map sensor in the bin.
We'll see.

One thing I am sure of though is it's time for more pictures and less bullshit.

Mounting the Map sensor..........



popped up into the vise and two little M5 rivet nuts bonded into the underneath.....





and then bolt her up to the harness bracket thing that sits on the engine
bulkhead........





after which it's time to plumb her up with that vacuum line so she can read the
engine vacuum. The location I have gone with is from a little rubber pipe that
comes up from the idle control valve and feeds air into the throttle bodies when
the butterflies are shut. This air feed is what keeps the engine breathing when the
throttles are shut and as it feeds all four cylinders I'm hoping that the vacuum in
this pipe should be smooth enough for the Map sensor to do it's thing.

In the pic below you can see the pipe connecting into the throttle bodies and
the arrow is pointing to a little "tee off" already in the pipe as standard.......



The reason for this is the smart people at Bmw already rob a vacuum signal
off this pipe to operate the fuel pressure regulator...........

[xworks]

But there was one more issue to take care of before the throttle pot
could be fitted. The new throttle pot uses M4 size bolts to mount it
on the engines it's used on, and, we need to use M5 sized bolts to nail it
on to our S14's throttle bodies. As a result the little "collars" on the throttle
pot are too small for the M5 bolts to pass through.........



So they need to be removed. After taking a quick look again at the total charge
on the main dealer invoice for the throttle pot to help suppress the urge to use a
hammer, an M5 bolt and appropriately sized socket are used instead.........



The whole lot gets popped up into the vise and the bolt is used to GENTLY
squeeze the collar out into the socket........





With the two collars removed the throttle pot could now be bolted up into place.......



Next item on the agenda isn't strictly 100% necessary to run the engine
but it's something I'd been reading up on and was keen to try out and
it is a Map sensor (Manifold Actual Pressure)...........

[xworks]

Now, while all that works out just nicely for the standard ecu, unfortunately
it's not worth a flying fu*k for our new ecu. Our airflow meter is gone
and we now need a lot more info from the throttle than just fully open or
fully closed. If we're going to be looking at how much the throttle is open
to gauge how much air is coming into the engine then we're going to need to
know exactly how much the throttle is open all the time.
So we change the throttle "switch" above for a throttle potentiometer shown
below...........



Although it bolts on in the same place and has the same amount of wires
going to it, the inner workings of a throttle pot are fairly different.

Once again the ecu always is sending 5 volts to the throttle pot,
but the difference this time is that 5 volts enters the pot and travels around
a resistor track slowly dropping voltage till it exists the far side where
only about half a volt has made the full journey.........



Now this time instead of a little arm connected to the throttle shaft
we have a little "wiper" which is hooked up to the middle pin of the
throttle pot. This little "wiper" rubs up against the resistor track and
carries the voltage at that point back out the middle pin and off to the
ecu.

With the throttle only pressed a little bit the wiper is pressing against the
beginning of the resistor track where the 5 volts is still strong and it carries
back the voltage at this point to the ecu........



As you begin to open the throttle a bit more and the wiper moves
around (it's connected to the throttle shaft) the 5 volts has started
to drop around the resistor track and as such the amount of voltage
the wiper is sending back to the ecu drops off.......



Right up until you start nearing full throttle where theres only
a small amount of that original 5 volts left to send back to the ecu.......



So basically depending on the voltage going back to the ecu it
can now figure out exactly how much you have the throttle open,
and as a result, start figuring out how much air is entering the engine
so it can do it's calculations of how much fuel to add and when to
fire the spark.

Now, with the bullshit taken care of it's on to actually nailing
the new throttle pot in to place.
With the old throttle switch and it's mounting plate removed theres a
fair bit of throttle shaft left sticking out...........





And as only the tip of this shaft is needed to stick into the new throttle pot
we're going to need a spacer to take up the gap. I've gone with one made
by Massive, available here.......

http://www.massivebrakes.com/accessories.php

[xworks]

Well, it's taken a bit longer then expected but it's finally time for another little update.
The last of the big obstacles to getting this car back on the road was always going to be
the engine management. As you've probably seen I've made a fair few changes to original
engine specification and as a result the original ecu in its standard form is no longer
suitable to take care of the fuelling and ignition requirements of the engine.........



As the engines breathing capabilities and compression ratio have both been increased
these two factors alone would have left the original fuel and ignition maps inside the
stock ecu unsuitable, however there has been one other major change in the hardware
that meant changes were going to be necessary. The stock ecu's main
method of measuring the amount of incoming air so it can figure out how much
fuel to inject is the airflow meter.........




and thanks to my new fancy airbox the airflow meter has now been relegated
to measuring the stagnant air in the bottom of the bin........



There's a clatter of different solutions to solving this particular problem and the
route I've chosen to take is an aftermarket ecu. The brand I've chosen to go with
is DTA and the model is an S40. It's the entry level ecu in the DTA range and although it
lacks some of the bell's and whistles of the more expensive ecu's out there it should
do everything I need it to just fine.
He said,
with his fingers crossed.



Unfortunately, as with most things in life, and, on reflection, almost everything
in this bloody restoration, things aren't just as simple as they first seem.
Along with the ecu change there was going to have to be some changes to the
rest of the hardware too.
As mentioned earlier the main method of measuring the quantity of incoming air
to the engine (the airflow meter) had been dumped because of it's restrictive nature,
so we're now left with the dilemma of how the new ecu is going to figure out how
much air is inbound.
And the answer is a throttle potentiometer or throttle "pot", if, like me, your mentally
challenged when it comes to speling.
The S14 engine already has a throttle pot of sorts bolted to the end of the throttle bodies........



But, if you crack it open what you'll find is it's actually a "throttle switch"
rather than a "throttle pot"...........



The standard ecu already has the airflow meter to tell it how much air is coming into the engine
so all it uses this switch for is to see if your foot is off the throttle or demanding full warp speed
with the throttle pedal planted deep into the carpet.

In the pictures below you can get an idea of how I think it works.
(not be be confused with how it probably really works.)

The body of the switch is bolted solid to the throttle bodies so it's not moving,
but, the little arm in the middle of it (purple) is stuck on the end of the
throttle butterfly shaft, so as you open and close the throttle the arm moves around too.
Along with the arm there a little switch and a set of contacts inside here too.
The ecu is constantly sending 5 volts to throttle switch (middle pin) and
when you have your foot off the throttle that little purple arm is resting on
the idle switch closing it's contacts.........



This allows the 5 volts to travel in from the middle pin, through the
closed switch and back out the bottom pin and off back to the ecu,
as shown in the pic above.
Once the ecu see's 5 volts coming back this wire it knows your off the gas
and the engine needs to idle, so it stops looking at the info coming from the
airflow meter and instead just concentrates on using
the idle control valve to keep the engine ticking over nicely.

The minute you start to press the throttle the little purple arm moves off this
switch and the contacts open again (can usually be heard as a little click).
From a tiny bit of throttle to almost full throttle the little arm moves around
inside not touching either the idle switch or the full throttle contacts.........



As the little arm isn't pushing either switch closed the 5 volts coming
in the centre pin has no route to take back to the ecu. Once the ecu
see's no voltage coming back from either wire it knows your motoring
along and it needs to pay attention to the airflow meter to see how much
air is coming in so it can calculate the fuel and spark.

The final use for the throttle switch is when you mash your foot to the floor.
As you pass the 90% throttle open point the little arm presses the set of
full throttle contacts closed. Once again the 5 volts coming in the centre pin now
has a route to make it back to the ecu..........



The 5 volts travels over the contacts and out the top pin back to
the ecu and once the ecu see's voltage coming back this wire it knows
that you require full warp speed and it adjusts the fuelling and spark
accordingly.

[monoi]

I'm suffering withdrawal symptoms!

[Thizzelle]

pics down

[Bartholomeo]

Some say, that when he fired it up, they saw only dust and burned rubber leading to the horizon....

[Car Addict]

not to add any pressure, but it has been just over a month any word on an update?

[amcink]

THANK YOU, THANK YOU, THANK YOU

JUST AMAZING!!!! Loss of Words

I'll buy the booklet also

[Car Addict]

That book would be the next bentley manual for the E30 community, except with way more content and actual good photos. well worth the money to have.

[///M42 sport]

that would be awesome...pdf/book def worth paying for

[siazul]

epic thread/build.

[Massimo]

Oh man I can't wait for the next installment now. I am looking into installing Megasquirt into my car soonish, and although the documentation is good and I have a reasonable idea on what I am doing, a full write up of a standalone install would be the greatest addition to the internetz. EVER!

Thank you so much you have made my day.

[xworks]

yeah it's been a while, sorry on that. Christmas brought productivity
to a complete halt. The switch to an aftermarket engine management system
is just about complete though. This took a fair bit more effort (learning) that I had
previously thought. I've about 300 pic's here of the whole installation and plan to
start writing it up just as soon as I can get some spare time. All effort's are going
into getting her to the rolling road at the moment. All going well I should have
some drivel up within the next 2/3 weeks, will try and make it worth the wait.

Thanks Matt for the offer on converting to PDF, much appreciated. The plan
at the moment is to try and get all this crap into some sort of indexed manual
for folk who want it when the fat lady eventually sings. Hopefully accompanied
by a dvd with all the pic's in full size.