Overboost - but only with boost gauge in circuit?
10 December 2003, 08:49 PM
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Can anyone tell me why I now get overboost (CEL comes on plus rapid deceleration) with a boost guage connected?
I'm running a Dawes Device which is switchable in circuit or out of circuit via solenoids, so I can use standard setup or extra boost. The overboost only occurs if I add the boost guage to the setup and have the Dawes operating. Without the guage but with Dawes on I do not get overboost.
The only way at present with the guage in circuit that I can avoid this is to reduce the Dawes boost, but even at 12 psi I get the CEL coming on due to overboost in 4th gear.
Any clues?
Ive tried the gauge either side of the Dawes. One side reads correctly but with overboost occurring, whilst the other side only reads up to 5 psi but I don't get overboost...so I'm guessing the boost guage is the problem - causing fluctuations in pressure?? (have double checked the connections and they are all sealed inside with pft tape or whatever you call it
)
Any answers much appreciated as it is annoying and I'd rather do without the boost gauge if it's going to cause these problems.
Tony
I'm running a Dawes Device which is switchable in circuit or out of circuit via solenoids, so I can use standard setup or extra boost. The overboost only occurs if I add the boost guage to the setup and have the Dawes operating. Without the guage but with Dawes on I do not get overboost.
The only way at present with the guage in circuit that I can avoid this is to reduce the Dawes boost, but even at 12 psi I get the CEL coming on due to overboost in 4th gear.
Any clues?
Ive tried the gauge either side of the Dawes. One side reads correctly but with overboost occurring, whilst the other side only reads up to 5 psi but I don't get overboost...so I'm guessing the boost guage is the problem - causing fluctuations in pressure?? (have double checked the connections and they are all sealed inside with pft tape or whatever you call it
)Any answers much appreciated as it is annoying and I'd rather do without the boost gauge if it's going to cause these problems.
Tony
11 December 2003, 01:46 PM
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Tony,
If I am reading this right you have the boost gauge plumbed into the boost control pipework somewhere between the compressor and the wastegate?
If so then this will not give you accurate readings and will screw up the boost control.
It's manifold pressure you are interested so that's where it should be connected. On the later classics there is a spare nipple on the manifold not sure about new age cars.
Andrew...
If I am reading this right you have the boost gauge plumbed into the boost control pipework somewhere between the compressor and the wastegate?
If so then this will not give you accurate readings and will screw up the boost control.
It's manifold pressure you are interested so that's where it should be connected. On the later classics there is a spare nipple on the manifold not sure about new age cars.
Andrew...
11 December 2003, 02:41 PM
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Thanks Andrew.
I can't find one, but then again I'm probably looking in the wrong place.
Can you tell where abouts to look, offline if you want.
When I get a spare moment I'll have another look, but moving house tomorrow at long last
so I'll be busy for the next 2 days or more.
I've disconnected the gauge for now. I've got an AFR to fit at some stage, and as you're the expert on these sorts of things I'm presuming its B17 pin out on the ECU and that you can't take it direct from the OBD (if I've spelt it correctly) as you can with your ScoobyMonitor?
Tony
[Edited by Tony_W - 12/11/2003 2:43:05 PM]
I can't find one, but then again I'm probably looking in the wrong place.
Can you tell where abouts to look, offline if you want.
When I get a spare moment I'll have another look, but moving house tomorrow at long last
so I'll be busy for the next 2 days or more.I've disconnected the gauge for now. I've got an AFR to fit at some stage, and as you're the expert on these sorts of things I'm presuming its B17 pin out on the ECU and that you can't take it direct from the OBD (if I've spelt it correctly) as you can with your ScoobyMonitor?
Tony
[Edited by Tony_W - 12/11/2003 2:43:05 PM]
11 December 2003, 02:56 PM
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agreed. from your post, it seems that u have connected the boost gauge (BG) pipe in the wrong place.
What u r doing is effectively running 2 boost controllers, one being the Dawes and the other the BG pipe. The way they are connected, the BG pipe is "leaking" boost hence causing overboosting.
OK, solution, I hope:
From solenoid or dawes, track the rubber hose back to the wastegate/turbo. Then, from the turbo, track the hose to the inlet manifold. There must be at least a hose which connects the turbo to the inlet manifold (usually a black rubber hose similar to the diameter of a pen.
There should be a spare "outlet" next to the "outlet" the hose is connected to. This is the case with older cars. Connect the BG pipe to this additional outlet. (did this on my 93wrx)
If not, u can cut the pipe running from the inlet to the turbo and insert a T-piece and connect the boost gauge from there but it has to be before the turbo/wastegate. (did this on my 98 typeR)
hope this helps
What u r doing is effectively running 2 boost controllers, one being the Dawes and the other the BG pipe. The way they are connected, the BG pipe is "leaking" boost hence causing overboosting.
OK, solution, I hope:
From solenoid or dawes, track the rubber hose back to the wastegate/turbo. Then, from the turbo, track the hose to the inlet manifold. There must be at least a hose which connects the turbo to the inlet manifold (usually a black rubber hose similar to the diameter of a pen.
There should be a spare "outlet" next to the "outlet" the hose is connected to. This is the case with older cars. Connect the BG pipe to this additional outlet. (did this on my 93wrx)
If not, u can cut the pipe running from the inlet to the turbo and insert a T-piece and connect the boost gauge from there but it has to be before the turbo/wastegate. (did this on my 98 typeR)
hope this helps
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