Low boost and nothing to engine

[jesprit]

Please help me

In brief:

1989 UK Turbo SE

My exhaust came apart today and on fitting in back together, I'm only producing 0.5 bar boost and none of it is going to the engine.

In detail:

My exhaust came apart just after the cat and before the silencer. There is some sort of valve here in it's own unit with a cable going off somewhere. We fitted it back together, and since doing this, have a low amount of boost - none of which is going to the engine. What is this thing and does it have to be put back in a very specific position? Is this in fact what is causing my boost loss or is this nothing to do with boost?

Please help me or I'll have to cry off the Virginia Water meet tomorrow.

If anyone can provide advice over the telephone, that will be most appreciated. My number is 0780 308 2078.

Thanks very much in advance.

Jason
'89 SE

[lotusguy]

jesprit said:

Please help me In brief: 1989 UK Turbo SE My exhaust came apart today and on fitting in back together, I'm only producing 0.5 bar boost and none of it is going to the engine. In detail: My exhaust came apart just after the cat and before the silencer. There is some sort of valve here in it's own unit with a cable going off somewhere. We fitted it back together, and since doing this, have a low amount of boost - none of which is going to the engine. What is this thing and does it have to be put back in a very specific position? Is this in fact what is causing my boost loss or is this nothing to do with boost? Please help me or I'll have to cry off the Virginia Water meet tomorrow. If anyone can provide advice over the telephone, that will be most appreciated. My number is 0780 308 2078. Thanks very much in advance. Jason '89 SE

Jason,

Simple! One of two things is happening, but either one restricts the exhaust flow, limiting the amount of exhaust available to spin your turbine.

The valve you refer to is the EBPV (Exhaust Back-Pressure Valve). It's purpose is to close upon cold start to bring the Cat up to operating temperature more quickly. Since these valves live in the hot, corrosive exhaust stream, they are prone to sticking and/or failing. I suspect your's is either sticking or mis-adjusted. Many owners simply incapacitate the valve by removing the butterfly, wiring the valve open or removing it altogether and replacing it with a spacer available from a variety of sources. Check that the valve opens fully and freely and that it is properly adjusted to do so. If not, incapacitate it.

Another possibility is that your Cat matrix has collapsed. This is not uncommon. What happens is that the ceramic matrix breaks and the pieces clog the exhaust stream again restricting exhaust flow. This is also very possible as you were moving the exhaust as you refit it. Start the car and listen to the Cat as you lift off the trottle (preferably with a friend outside the car next to the cat. If you hear any sort of rattling, then is a god bet that your Cat matrix has collapsed. The fix is to either replace the cat, or to use Lotus Tool #1 (broomstick handle) and continuously jam it into the Cat until all the ceramic matrix is removed leaving you with essentially a hollow tube. Hope this helps. Happy Motoring!... Jim'85TE

[jesprit]

Hi Jim,

Thank you very much for your reply. Exhaust Back-Pressure Valve - that's the kiddy :-) This appears to be moving OK. We have sprayed it with a bit of WD40 and, although a little squeeky to begin with, appears to be alright now. I put my hand up into the cat and there appeared to be a gauze at the end. Is this normal or is this the gunk you're talking about and I need to smash through this with the broom handle?

Many thanks again for your help.

Jason

[lotusguy]

jesprit said:

Hi Jim, Thank you very much for your reply. Exhaust Back-Pressure Valve - that's the kiddy :-) This appears to be moving OK. We have sprayed it with a bit of WD40 and, although a little squeeky to begin with, appears to be alright now. I put my hand up into the cat and there appeared to be a gauze at the end. Is this normal or is this the gunk you're talking about and I need to smash through this with the broom handle? Many thanks again for your help. Jason

Jason,

Glad to hear you're on the right track, but lubricating the EBPV w/ WD-40 will be as temporary as the next time you run the car. As the exhaust temperature far exceeds the burning point of WD-40, you will flash it off or burn it immediately. Best to remove the valve and clean it up properly using a stiff wire brush to remove rust and exhaust deposits, or as I said, remove it altogether or wire it open. It's only purpose is to speed the heating of the Cat to operating temp, but on these cars, the Cat comes up to temp rather quickly anyway.

As far as your Cat, you really should not see anything clogging the end, be it gauze, ceramic bits or the like. I will not recommend nullifying an emissions devise, but if there is a restriction in the exhaust stream preventing you from getting full boost, it's safe to say that removing that restriction will correct the problem... If your state/country has strict emissions testing, replacement of the Cat may be necessary for the car to be certified. Happy Motoring!... Jim'85TE

[jesprit]

Hi Jim.

Thanks very much for the information. We dismantled the exhaust and EBPV valve area again and reassembled it making sure that the butterfly valve could fully open and hey presto, my Loti is working again. However!!! I have another problem now. The car is
overboosting like mad, going all the way to the end of the gauge on the boost valve. At this point, after 5 seconds or so the engine cuts out until all is normal again. From other posts I am guessing this is the Wastegate stuck open as I have read other people having this problem.

Thanks again.

Jason

[lotusguy]

jesprit said:

Hi Jim. Thanks very much for the information. We dismantled the exhaust and EBPV valve area again and reassembled it making sure that the butterfly valve could fully open and hey presto, my Loti is working again. However!!! I have another problem now. The car is overboosting like mad, going all the way to the end of the gauge on the boost valve. At this point, after 5 seconds or so the engine cuts out until all is normal again. From other posts I am guessing this is the Wastegate stuck open as I have read other people having this problem. Thanks again. Jason

Jason,

Very possibly a stuck wastegate. You are hitting the rev limiter which cuts the ignition spark. Good Luck! Happy Motoring!... Jim'85TE

[JEsprit]

Hi Jim.

I just wanted to let you and others that read this post in the future know that I managed to rid my overboost by resetting the ECU. I guess it must have gotten its knickers in a real twist with the EBPV sending incorrect information and thought the overboost was OK. I dismantled the actuator arm from the wastegate and made sure it was nice and free and it was fine. No stickiness at all.

Thank you once again for helping me. As a consequence, my car and myself had an absolute blast at the PistonHeads meeting yesterday.

All the best,

Jason