 OVERBOOST
PROTECTION
Written by Cory B.
Ever had your wastegate
line blow off? Wastegate fail? Ever just set something
up wrong and blew an engine? Me either. But that sure
as heck doesn't mean I am gonna sit around and wait for
it to happen!
I
have designed an overboost protector around a Hobbs
pressure switch. What this system does is turns off
the power to your coil when desired "overboost" setting
is reached. What you do is set the Hobbs switch slightly
higher than your boost setting on your wastegate, EBC,
MBC whatever. Once that pressure is reached due to a
boost control failure, bam, coil is turned off. And as
we all know, an engine needs Air, Fuel, Spark and Compression
to run. IF you take away spark, the engine CANNOT create
boost or run any longer. The beauty is, once you go back
below that set "overboost" setting on the Hobbs
swich, bam, power is back on. Now your car drives like
normal again so you can drive it home and find out what
went wrong. It is so simple, I can't believe I haven't
seen it before.
Items
needed:
One
Hobbs pressure switch. Sold at most forced induction
related sites, as they are very popular with many many
setups/kitsAbout
5 ft of 16g wire depending on how exactly you route
this setup
About
1ft of vacuum hose
Zip
ties of course
A
couple crimp-on connectors for the Hobbs tabs and relay
if you choose
A
SPDT relay (5 pin automotive relay. Should have pins
85, 86, 87, 87a, and 30)
*S14
owners only*-you will prolly need more 16 gauge wire
to run due to the location of your positive coil wire
Items
recommended:
A
multimeter. I used this so I could set my Hobbs switch
up with my air compressor. Use the Ohm setting and
alligator clip the probes onto each connector of the
Hobbs switch. Then just adjust the screw so you get
resistance only past desired boost level.
An
accurate boost gauge(I used my AVC-R)
Now for install
instructions: (DISCONNECT BATTERY BEFORE YOU DO ANYTHING!)
Number one: Clip
your stock positive coil wire(black with red stripe on
both S13 and S14. S14 guys, you will have to look near
the distributor cap to find it/and prolly have to run
a little more wire to wherever you choose to mount the
relay) and strip both ends. Run the ECU side of the coil
wire to pin 30. Run the coil side of the positive ignition
wire to pin 87a. Solder on that 16 gauge piece of wire
to pin 85 or 86(doesn't matter as the relay coil is not
polarity sensitive. Make a small "jumper" out
of a piece of 16 gauge wire and run it from pin 30 to
pin 86 or 87(doesn't matter as the relay coil is not
polarity sensitive)
Click on picture
to enlarge.
Number two: Run
the 16 gauge wire from pin 85 or 86(whichever you chose)
to wherever you plan on mounting the Hobbs pressure switch.
I recommend putting it near the intake manifold to get
an accurate pressure reading on what is entering your
engine. You'll need to set the Hobbs switch approx 2psi
higher if you use a hotpipe boost source. But I wouldn't
recommend that as the Hobbs switch box clearly says to
avoid high heat. I mounted mine here:
Click on picture
to enlarge.
Number three: Find
a good ground point. Run some 16 gauge wire to that point
and ground it using a crimp-on connector. I used whatever
that ground is on front of the passenger side wheel well.
Sand the contact point well
Click on picture
to enlarge.
Number four: Tap
into a good boost source. FPR line is probably your best
bet.
Click on picture
to enlarge.
Number five: Crimp
the connectors onto your ignition tap wire and the grounded
wire and connect them to your Hobbs switch.
Number six: Remove
that rubber plug on top of the Hobbs switch and tune
it. I removed the vacuum line from the intake manifold
and used an air compressor. But in order to do this,
you must have a multimeter and use the method I described
above. If not, you will more than likely need to do trial
and error.
I
tested this with the limit at about 7.5psi and it definatly
works. Feels just like your engine had no spark. Go
figure!haha But as soon as boost drops below that,
the engine comes right back on and runs normal. So,
unlike common "pop
off valves", you will NOT have an abnormally rich
condition on the way home to replace your wastegate line.
And this is ADJUSTABLE!!!
Before you boost away,
try jumping the Hobbs switch terminals to see if the
car shuts off and that you did everything properly. Just
touch each end of a small piece of wire to each terminal
on the Hobbs switch while the car is running to make
sure it shuts off. If not, then this is useless to you
still and you made a mistake somewhere.
I set mine at about 15psi
and I run 12psi most of the time. So, if a wastegate
line ever blows, I'm ready!
[ Go Back ] |
