Dump Valve fitment
Now, if you don't fit an Intercooler, or even if you do, you can still fit an after market Dump Valve!
You need to drill a hold in the side of the plenum chamber, so remove it, simple task if looked at, there is 2 13mm bolts
behind it, remove and remember where all pipes go!
Drill a hole about 25-30mm in diameter at the LOWEST point of the sloped side of the plenum chamber, if you don't,
and the fitment is too high, you won't be able to close the bonnet properly, the dump valve tends to stick out!
Then find some metal pipe, about the same size as the dump valve opening, I used some of my dumbbell weight bar,
I cut it off, and then weld it to the metal plenum chamber!
Can't weld? Easy, buy some Chemical Metal, and make sure its sealed well!
I did, and it's as strong as a weld!
Home-made dump valve extension!
You then need about 1 inch of rubber pipe to fit the dump valve to the plenum extension, I got 0.5metre of clear hose for
a stupid price, something like 50p from the local hardware store.
Next, once the dump valve is fitted, connect some vacuum pipe to it.
Now, this is the mistake I made!
When you release the throttle when driving, the dump valve gets `pulled` open by the vacuum feed.
I originally had it connected to the existing feed that fed near the carb, big no no!
It'd NOT strong enough to pull open the dump valve!
So, remove the inlet manifold (refer to a Haynes manual), and you need a special `nipple` (oi, no sniggering!)
that is the correct size to fit a vacuum pipe to, get one from a local car dealer, Halfords, Les Smiths etc.
Drill a correct size hole, making sure NOT to drill the water jacket in the manifold, there IS a round blank panel
on the manifold, drill it and screw the nipple in there, then connect all the stuff back together, and go for a test drive!
Drill where circled using a correct sized drill bit!
Every time you put your foot down, and release the throttle, you should hear a TISSSSHHH...as the boost is dumped to the engine bay.
If not, check for leaks, and correct fitment!
One thing to remember, you don't need the crappy standard dump valve as fitted on the MT as standard!
Its located in the front of the plenum chamber, and consists of nothing more than a spring and a bung, remove these,
cut some cork to size, and plug the hole!
Number 2 & 3 are the standard dump valve components, remove them, and plug the remaining hole!
Below are some dump valves for Forge Motorsport (www.forgemotorsport.co.uk)
They are (from left to right), a Competition dump valve, a fast road dump valve, and a piston dump valve.
Apparently, Forger DV's are goddamn loud!
Goto their site, and check them out!
Points to remember:
If you buy a cheap DV, it will almost certainly have a RUBBER diaphragm, its OK, for a while, and then they split!
Leading to boost loss and non-working DV's! Get a decent KEVLAR diaphragm, they're only like £10, or buy a DV with a Kevlar
already in it!
Or, get a piston one, they don't split!
Don't bother buying any Metro Turbo DV fitting kits, there NOTHING in the box worth the money!
You still HAVE to make a hole in the plenum chamber, be warned!