- Turbo Boost page 4 of 6
So, why do I not see 0.7 bar on my boost gauge ?, I have adjusted the pre-load on the wastegates as much as I dare, the boost solenoid makes the “ppphhhrrrttt” noise as it should when being tested by the using the tech1.
Boost pressure is fed into a T piece from each of the compressor sides of the turbos, this then goes to the boost solenoid, then a pipe goes from the solenoid to the wastegate actuators.
I rigged up some air pressure to the boost solenoid, and put my gunsen gauge on the exit of the solenoid which would normally go to the wastegate actuators, I wanted to simulate what happens when the solenoid is actuated by the tech1 with air pressure.
When I operated the solenoid, it let all the pressure out of the exhaust at the bottom of the solenoid for the duration of its activation, when it stopped the gauge returned to the same pressure…….ok, this is kind of what I expected………
Then I wondered what would happen if I reversed the pipe connections, so I did.
This time the gauge needle went mad between about 4psi and 6psi, ie not all the air pressure was being let out……ie it was being metered ??…..mmmmmmmm
I scoured the manual to find out which way around the pipes should be, ie does the pipe from the turbo pressure side go to the top or the bottom ??
The diagram showed the output from the turbo compressor side connects to the top of the boost valve, not the bottom as mine was connected !!!!! holy shit looks like I found the problem. A quick call to helpful club member Dave Kember who checked his own LC (thank god for this club !!) confirmed this.
I reverse the pipes and go for a spin, carefully feeding in the power because I don’t want anything nasty like excessive turbo boost, so I keep close eye on the gauge.
WOW!!, easy up to 0.7bar spot on !! with nearly full throttle, with full throttle it pushes further still to about 0.8bar on the gauge !! fantastic. Back off the throttle and then plant it showed an increase right to 0.8 – 0.9 bar then quickly settling to 0.8bar, then foot slightly off and boost sits at 0.7
Remembering Malcolm’s experiment, which is just to disconnect the solenoid revealed no boost over about 0.6 bar……..great, confirmation again.
Ok, so looks like I overlooked the obvious, why did I not check the hose connections to start with ?, easily said I suppose. I assumed they were correct, I’d never taken them off before. How could they have got mixed up ?
I dug out the old boost solenoid (fitted with the old superchip) although it looks much the same with a pipe connector top and bottom, because the mount bracket is to one side the exhaust is on the top when fitted, compared to the std unit when fitted the exhaust is at the bottom………so if you swap pipe position for pipe position , they will end up the wrong way around.