eastendr
New member
After having a boost pipe blow off, I decided to carry out a full check of the clamps and general air-tightness, including all the vacuum lines. I have been getting sporadic over-boost for some time and wanted to get to the bottom of it.
Using a combination of a footpump with pressure gauge and several types of purosil hose, a vacuum pump and some smoke matches I found a number of small leaks.
Firstly I had been getting a hiss during boost from behind the instruments where I have a number of sensors for the SBC-iD boost controller, HKS camp and feed to the A pillar mounted boost gauge. These are all fed by a single purosil feed through the bulkhead. I had used a number of adaptors to link all the necessary pipes, but these were now worked loose and starting to leak. A change to the plumbing means that this segment now holds 20 PSI indefinitely.
I then checked all the heater control and vacuum reservoir segment, which had no leaks. Likewise the non-return valve (blue/black plastic) was fully functional.
Next up, the vapour purge / dump valve. This was leaking quite badly from the dump valve when over 10PSI was applied. This is a Bailey DV vent to atmosphere piston type valve. I stripped it down and cleaned the piston sealing ring and the rest of the internals. This is now performing as it should. The next leak was from the metal fuel purge valve where the purosil joined the nipple. Not wanting to use cable ties to secure the purosil, I looked for an alternative.
A phone call to John Sims about the number of small leaks found us discussing a better way of sealing the purosil. John came up with the excellent idea of tight rubber O rings rolled over the joint. A quick rummage in the spares rack found a whole load of suitable rubber rings. I have fitted 2 to a number of places where the purosil vacuum hoses fit over connection nipples, such as both vapour valves, dump valve, fuel pressure regulator etc.
This has bought about a remarkable improvement as all the small individual leaks add up to quite a loss ! I now have 20 hg of vacuum at idle again.
Next up, I thought I'd pressure test the boost control circuit. I have an EBC fitted and this is still fed from the banjo on the boost pipe, via small bore Aeroquip hose to the boost controller and finally to the Lindsey dual port wastegate.
There was a considerable leak coming from under the car in the wastegate area. Putting the car up on the ramp and dropping the undertray revealed that the nipple on the top of the wastegate had worked loose. I disconnected the Aeroquip pipe and tightened the brass elbow adaptor further in to the wastegate then reconnected the pipe. A new pressure test from above revealed there was still a significant leak. Moving the Aeroquip pipe around revealed the reason.
The Aeroquip had moved around and got too close to the the exhaust flange at some point and melted some of it's internals. In one position the pipe was leaking badly, in another position (small change) the seal was good. At last a reason for the intermittent boost control ! I replaced the section of Aeroquip between the boost controller and wastegate, and rerouted it further away from the hot areas, cable tying it in place.
The final pressure test shows slight leakage from the wastegate itself. A discussion with John Sims again confirmed that his Tial wastegate also leaks copious amounts of air from the control lines!
A final road test shows that vacuum is now much better, maxing at 22 Hg on the overrun and 18-20 Hg at (hot) idle.
The boost controller is now able to to control down to a rock solid 7.2 PSI. I haven't tested the upper limits yet because it was absoloutely pouring with rain and I was on the North Circular Road in quite heavy traffic.
I have now fitted a G-Force RR performance analyser http://www.gtechpro.com.
In pouring rain, with 7.2 PSI boost I managed 0-60 8.28 sec, 157.8 BHP @ 4869RPM, 179.6 ft-lbs @ 4477RPM. This is RWHP.
I'll be able to put some proper figures out when I've weighed the car accurately and got some decent dry flat road !
Using a combination of a footpump with pressure gauge and several types of purosil hose, a vacuum pump and some smoke matches I found a number of small leaks.
Firstly I had been getting a hiss during boost from behind the instruments where I have a number of sensors for the SBC-iD boost controller, HKS camp and feed to the A pillar mounted boost gauge. These are all fed by a single purosil feed through the bulkhead. I had used a number of adaptors to link all the necessary pipes, but these were now worked loose and starting to leak. A change to the plumbing means that this segment now holds 20 PSI indefinitely.
I then checked all the heater control and vacuum reservoir segment, which had no leaks. Likewise the non-return valve (blue/black plastic) was fully functional.
Next up, the vapour purge / dump valve. This was leaking quite badly from the dump valve when over 10PSI was applied. This is a Bailey DV vent to atmosphere piston type valve. I stripped it down and cleaned the piston sealing ring and the rest of the internals. This is now performing as it should. The next leak was from the metal fuel purge valve where the purosil joined the nipple. Not wanting to use cable ties to secure the purosil, I looked for an alternative.
A phone call to John Sims about the number of small leaks found us discussing a better way of sealing the purosil. John came up with the excellent idea of tight rubber O rings rolled over the joint. A quick rummage in the spares rack found a whole load of suitable rubber rings. I have fitted 2 to a number of places where the purosil vacuum hoses fit over connection nipples, such as both vapour valves, dump valve, fuel pressure regulator etc.
This has bought about a remarkable improvement as all the small individual leaks add up to quite a loss ! I now have 20 hg of vacuum at idle again.
Next up, I thought I'd pressure test the boost control circuit. I have an EBC fitted and this is still fed from the banjo on the boost pipe, via small bore Aeroquip hose to the boost controller and finally to the Lindsey dual port wastegate.
There was a considerable leak coming from under the car in the wastegate area. Putting the car up on the ramp and dropping the undertray revealed that the nipple on the top of the wastegate had worked loose. I disconnected the Aeroquip pipe and tightened the brass elbow adaptor further in to the wastegate then reconnected the pipe. A new pressure test from above revealed there was still a significant leak. Moving the Aeroquip pipe around revealed the reason.
The Aeroquip had moved around and got too close to the the exhaust flange at some point and melted some of it's internals. In one position the pipe was leaking badly, in another position (small change) the seal was good. At last a reason for the intermittent boost control ! I replaced the section of Aeroquip between the boost controller and wastegate, and rerouted it further away from the hot areas, cable tying it in place.
The final pressure test shows slight leakage from the wastegate itself. A discussion with John Sims again confirmed that his Tial wastegate also leaks copious amounts of air from the control lines!
A final road test shows that vacuum is now much better, maxing at 22 Hg on the overrun and 18-20 Hg at (hot) idle.
The boost controller is now able to to control down to a rock solid 7.2 PSI. I haven't tested the upper limits yet because it was absoloutely pouring with rain and I was on the North Circular Road in quite heavy traffic.
I have now fitted a G-Force RR performance analyser http://www.gtechpro.com.
In pouring rain, with 7.2 PSI boost I managed 0-60 8.28 sec, 157.8 BHP @ 4869RPM, 179.6 ft-lbs @ 4477RPM. This is RWHP.
I'll be able to put some proper figures out when I've weighed the car accurately and got some decent dry flat road !
