turbo boost problems

Ok I have a Thema LS Turbo. The 205BHP model. My reserc valve failed so I
changed it for a Forge Motorsport one. However if I released the accelerator
pedal just before the turbo kicked in it would cough and jerk the car. I
have now put a standard reserc valve in and the problem has gone. Wierd?



I need some advice please also; I have put in a bleed valve and opened it
ever so slightly so it pulls just over 1 bar (1.5 overboost). However in
gears 4, 5 my injector light comes under prolonged acceleration. I want more
boost in gears 1,2 and 3. I do not care about gears 4 and 5. So basically
how do I increase boost in gears 1,2 and 3 and reduce it in gears 4 and 5 as
to keep within the limits of the engine. I have been told that 1.2 is MAX
for the LS Turbo. At the moment I am a 1bar in gears 1,2 and 3 and 1.3 bar
in gears 4 and 5.


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"vlg" <vlg DeleteThis @btinternet.com> wrote in
news:bluqk7$aqg$1@sparta.btinternet.com:
 >
 > I need some advice please also; I have put in a bleed valve and opened
 > it ever so slightly so it pulls just over 1 bar (1.5 overboost).
 > However in gears 4, 5 my injector light comes under prolonged
 > acceleration. I want more boost in gears 1,2 and 3. I do not care
 > about gears 4 and 5. So basically how do I increase boost in gears 1,2
 > and 3 and reduce it in gears 4 and 5 as to keep within the limits of
 > the engine. I have been told that 1.2 is MAX for the LS Turbo. At the
 > moment I am a 1bar in gears 1,2 and 3 and 1.3 bar in gears 4 and 5.

Get a decent boostcontroller, at least a ball and spring type. Bleed
valves suck and exhibit the characteristic you mention now ; building
substantially more boost in higher gears. My friend uses a bleed valve to
control his BOV (to keep it shut at idle). That's about the only thing
they are good for.

A ball and spring controller usually makes it spool faster too, by not
opening the wastegate partially WAY before set pressure is reached like a
bleeder does.

You may even need an electronic boost controller to make boost exactly
equal in all gears, as there will always be a slight difference between
the gears with any type of purely mechanical boost controller. Some might
even allow setting boost per gear.

Either that or you add switch valves that switch between different manual
boost controllers, one for low gears and one for high gears. You could
fab something with microswitches on the gearbox to engage them, or do it
manually (in that case, don't forget!)

It may also be that in the first couple of gears, the turbo can't keep up
with engine rpm's (that rise very fast in low gears). There isn't much
you can do about that, although a ball and spring controller should
certainly help even that situation, by keeping the wastegate shut better
than a bleeder does.

Well, I think I gave you a couple of ideas to try... good luck!

Marcel<!-- ~MESSAGE_AFTER~ -->