Controlling Boost levels

chodjinn · Post by **chodjinn** » Mon Aug 20, 2007 11:07 am

Just ordered/enquired about my megasquirt ecu and decided to not use it for controlling the boost at the moment.

So, I'm wondering what would be the best way of doing so (apart from buying a boost controller . . .

)

I have twin turbos with external wastegates. In my mind they have a spring to control the boost level - does this need changing to alter the boost? Originally they were set to 7psi, but after 20yrs of abuse I managed about 5-6psi last time the car was driven.

How can I manage the boost with my set up?

(Ideally want control for 4-8psi approx.)

bill shurvinton · Post by **bill shurvinton** » Mon Aug 20, 2007 1:22 pm

The way all boost control is done is by an adjustable air bleed, which can be done by a number of methods, mechanical or electrical. Going below the spring setting (i.e. 4 PSI) is a little bit harder as you need valves on both sides of the wastegate to reduce opening pressure. Weaker springs are sometimes available.

chodjinn · Post by **chodjinn** » Mon Aug 20, 2007 1:43 pm

Well this is the thing Bill, trhe original kits were fixed at 7psi, but I never saw it that high on the old engine (however, two blown head gaskets might not have helped).

Okay, say I sack off the low-boost idea and just go with a mechanical controller (e.g. a cheap on from an R5 GT turbo etc), will it allow me to run more than 7psi without changing the wastegate spring settings? I want to do this as easy as possible. If its too much hassle then I just wont bother and leave it at a fixed psi.

How do they plumb in?

stevieturbo · Post by **stevieturbo** » Mon Aug 20, 2007 8:02 pm

mechanical controller.....bleed valve.

Cheapest adjustable ones are available from fish tank places....Last ones I bought were about £1.10 for 2 lol

Single boost source, bleed valve, tee, bottom port of wastegates. ( to blow them open )

Job done.

There are many other ways to "bleed", but if you want cheap, the above is cheap.

Or buy a half decent brass/alu bleed valve. Do beware though. There really are some cheap crap ones out there, that bleed so much air, you will have no control.

The plastic fish tank jobbies are crap, but in terms of control, they are actually quite good.

chodjinn · Post by **chodjinn** » Tue Aug 21, 2007 7:31 am

thanks Stevie.

Had a look last night, and can get a bleed valve relatively cheaply, plus an additional block thing (as i have two turbos). You can also get add-ons to fix the upper/lower boost limits which is quite useful. Not going to do it right away, but certainly food for though.

cheers

olly