Boost UpgradeThe basics of power from a turbocharged engine, come from the turbo itself, and the boost levels produced.Really basically, it's put like this:
More/Higher boost = More power
That is until a point where components within the engine are so stressed, you get a BANG!
And everything cost loads of money and looks a mess!
Now, with Metro Turbo's, the far easiest way to increase power, is to `up` this boost level.
To do this you need the following:
Bleed Valve AKA Boost Adjuster
Uprated carb needle
Uprated carb spring
A way of measuring boost levels
Left: Forge Motorsport bleed valves Right: My bleed valve, spring and needle combo
Bleed valves are simple a device that is put between what's known as the wastegate, and the turbo on a rubber pipe.
See diagram below, and look at label 1a.
Basically boost from the turbocharger reaches a point (4psi) in the MT's case, some of this boost
flows through a rubber tube to the wastegate, which in turns moves the arm, which then opens a
flap at the exhaust end of the turbo charger, and boost is vented straight out the manifold, so the
boost is controlled, and maintained this way.
Get the idea yet?
Place the bleed valve marked with the red circles
( In the second circle, it is NOT the pipe shown, but hidden BELOW this pipe! )
Basically, putting a `tap` into this rubber pipe, and `bleeding` off some wastegate air, causes the flap
in the exhaust end to open later, because it is fooled by the fact that not all the correct boost is going
to the wastegate, and thusly, the turbo pushes more boost into your manifold/engine at a higher boost.
Unscrewing the tap a little more, causing more air to be bled off, causing more fooling, and more boost!
OK, what boost levels should I be aiming for?
Now, this is where it's debatable!
From experience, I have run (from the standard 4PSI)l;
6psi
8psi
10psi
and even 12psi
All these were according to a TIM Turbo Boost Gauge attached to the manifold!
( Which is not a 100% accurate way to measure boost levels )
My Tim Turbo Boost Gauge in a pod mounting
I was told by Avonbar (www.avonbar.co.uk) that I could run 8, 10 or 12psi using their hi-boost needle and spring combo.
He said, and I quote `If you want to go above 12psi, you're on your own`.
So, take note, above 12psi, and say bye bye!
I successfully ran 8psi and caned the car, NO PROBLEMS!
Not content with this, I upped to 10psi, and that is where
the boost level stayed, and I had NO problems, was it quick you ask?
Well, all I can say is, It could keep up with an RS Turbo up until about 80-90, where Metro gear ratios and high speeds don't mix!
But, anyway, it certainly gave people a shock from the lights!
But the actual MAXIMUM boost an MT produces is 7psi, so if you want to be safe,
then increase to this maximum level, and you should be okay!
Points to remember before upping boost:
Is your turbo charger in good working order?
Is your engine in good working order?
Is your gearbox in good working order?
...you get the picture, basically, don't crank the boost up on a shoddy Metro Turbo, it will almost certainly give up the ghost!
Another thing you can do is remove the wires from the boost regulator, it's located far right of the engine bay.
Removing the blade connectors, and taping them away somewhere, causes the boost to be constant
throughout the engine revs, so now, removing this `regulation` of boost, will allow you to get a constant
boost level from the bleed valve technique.
Its number 5 you should be looking at, remove the connectors, insulate them with some tape, and put them aside securly.
OK, thing to remember, by now, more boost means the turbo charger is working overtime, which means more heat!
A big no no in modding department, make sure, you have GOOD oil, if you're unsure when the last time you MT had an oil change,
now is the time to do it, and remember to use good quality 10w40 oil!
Ensure you have the correct mixture and quantity of coolant in your engine.
Ok, I have come up with an idea on how to control the boost from the cockpit, so you can run normal boost levels
when cruising, or saving petrol, and when you need extra boost, can whack the boost up safely, here's the idea:
What you need is a 3-way bleed valve AND a 2 way one.
What the idea is, is to set the underbonnet valve to the maximum desired boost level.
Then the to air bleed `nipple` is connected to a second 2-way valve in the cockpit.
The idea is that if the cockpit valve is closed, the first valve is basically inoperative, because where the air normally bleeds
off, is actually blocked by the cockpit valve, so you run normal boost.
Now, if you open the cockpit ( 2-way ) valve, you start to let the first valves air escape, and hey presto, increased boost!
The advantages of this, is that, no matter how much you open the cockpit valve, the boost won't increase above what
the underbonnet 3-way valve is set to, so you cannot let your Metro Turboo go bang!
Simple huh, and effective, I have yet to try this, and would appreicate comments, or mistakes that I have made on this.
In principal, I can't see why it should not work if there are no air leaks!
Why buy a £50 or more cockpit kit, when you can buy bleed valves for as little as £10 each!
