how to...
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| Fit a bleed valve 16vt/20vt | by Spunky M / Andy Macdonald (16vt) |
Important - Doing this modification can easily damage your engine. If you are unsure of what you are doing then don't do it. Spunky M and coupe-sport take no responsibility for any damage that may result from doing this modification. Removal of the electronic bleed valve limits some of the ECU safety features. But if you want
to then.... |
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Remove the two pipes coming from the bottom of the valve and thread them back towards the engine to give more length to play with. Put them directly onto the opposing nozzles of the passive bleed valve and there you go. The centre nozzle is bleed to atmosphere.As usual, it's a good idea to put the odd cable tie or jubilee clip on the pipes to stop them falling off accidentally. The one thing that you do notice with this mod is that you can get full boost when the engine is cold - while it's not really a problem as long as you don't floor it as soon as you set off (not good practise anyway), I thought it would be a good idea to have the option of switching to minimum boost for when the engine is cold and for when I want to save petrol and tyres... |
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...To do this you need something to block the airflow on the exhaust of the passive valve - another electronic boost valve was the ideal option for me as I had a spare one lying around - I think they cost about £40 from Fiat. Alternatively you could use the original electronic valve (which is now just sat doing nothing in terms of boost control) as long as you replace it electrically so that the ECU thinks it is still there - you could do this with a simple resistor (the resistance of the electronic valve is 24 ohms) but you will need one that can dissipate at least 8W comfortably. If using the electronic valve you need to bung the nozzle nearest the electrical connections and then connect the exhaust from the passive valve to the nozzle next to it. The nozzle on the top of the electronic valve now becomes the exhaust to atmosphere BUT only when you apply 12v to the electrical connections (via a switch inside the car). |
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...For the 16v turbo, the
electronic bleed valve is the cylindrical object seen in the blue rectangle (behind the
pipe). It will have 3 pipes and a wire coming off it. |
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attach these to the opposing sides of
your nice new passive bleed valve (red rectangle). Leave the valve venting to atmosphere.
(the middle port) |
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I also made a small black line on the new
valve to indicate where my max setting was so that if i ever had to turn it down, ie for
servicing |
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Setting up... Many people advise against
fitting these devices - and with good reason. If you go mad with the boost level, or if
the fuelling runs lean it is possible that you'll blow up your engine! Also, you are
removing some of the control features from the engine management system. However, keep
things sensible and you may find your coupe is suddenly a much nicer car to drive car.
Personally I wasn't really looking for more power (O.K. maybe just a tiny bit) but wanted
to make the acceleration more consistant and smooth. I've never been convinced of the
control loop of the electronic valve and was never keen on the way it used to make the car
feel like Jekyl and Hyde (probably spelt that wrong). I think one of the reasons for this
is that the electronic valve gives what is effectively an overboost function at around
2500-3000rpm (can be seen on dyno curves) but I think that this is just the result from
the slow response of the valve to regulate boost pressure. Anyway I didn't like going from
no boost to overboost then back to normal full boost - I felt it made the car less
drivable. The electronic valve also decreases boost if the revs rise too quickly i.e. in
first and second - all this has now gone with the passive. The valve I used is made by a company called Le Mans and it is a brass 3-way adjustable type. It is available from all Halfords stores priced around £15. Installation really is the easiest thing in the world - taking around 10mins from start to finish. I decided to bypass the electronic valve completely (you still have to leave the electrical connections on) rather than add it with a T-piece in the actuator pipe.
You really need a boost gauge
to do this properly. As I wasn't checking fueling when setting the boost pressure, I
started with the valve fully closed. This means that the actuator is connected directly to
the compressing side of the turbo and results in minimum boost pressure (about 0.6bar in
my case). The first thing you notice at 0.6bar is how much smoother the power delivery is
but of course without the push to the back of seat. I'd consider using this setting all
the time for when the wife is driving or when I want to save on petrol. Anyway - 0.6bar is
obviously no good for me so I opened the valve an eigth of a turn and went for another
spin. The turbo pressure builds fairly gradualy with a gentle accelerator in the higher
gears so it's easy to back off if the boost goes too high. Anyway, an eighth of a turn
gave me about an extra 0.1bar so I opened it until I was getting a nice solid 1bar of
boost. This should be well within the 20VT's capabilities (it normaly hits at least 1.2bar
on overboost with the std electronic valve in). I left the boost at 1bar and
when for a good blast. The first thing that hits you is 1bar of boost in 1st & 2nd
gear - Jeeeeeeeeeezus I could go through a set of tyres in a day if I wanted to!! - the
thing pulls like a demented dentist, but the thing is, you ease off a bit and it all calms
down and is completely controllable - it's completely up to you if you want to shread
tyres or not, which is just the way it should be. Oh yes I'll stick with 1bar of boost in
1st gear thank you sir. With the electronic valve I noticed that the boost would really
drop off as the revs built past 5000rpm (sometimes to as low as 0.5bar) and I could see
that this was partly due to the electronic control of the valve in my analysis with a
digital hand held scope. With the passive valve in, the boost does still drop after
5000rpm but by nowhere near as much (drops to just under 0.9bar) which I guess is due to
exhaust back pressure / slightly weak actuator spring. I'm still not sure why the
electronic valve wanted to reduce the boost so much more after 5000rpm - maybe just a shit
program but I cannot ignore it could have been due to the ECU detecting the engine
knocking or the fuelling running lean (although fuelling looked fine at full boost in 4th
on rolling road). So before I increase the boost any more it's over to a turbo techincs
rolling road in York just to make sure everything is O.K. I may tweak the boost to about
1.2bar while it's on the dyno and see what I get. Well I'm DEFINITELY staying with the passive valve - a rock solid 1bar of boost in every gear resulting in what feels like a much flatter more predictable torque curve. Well pleased with the results for £15.
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Stuck in a Frame / No side Frame then click the link below |
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Installation