Waste gate or pop off

[cly_mitchell]

'83 Turbo

When I run my car past 3000 rpm my pop off, well, pops off and stays open until I change gears. It happened intermittently to start but now its all the time. I have a boost controller on the waste gate. My turbo has about 2000 miles on it. My boost has alway read a little high on my gauge, 10psi. I believe the car is set up that way, as it runs a little rich at low speed. I can also feel a loss of power at pop off, 3000 rpm. The boost reads 10psi even after pop off.

So, it is either the pop off or the waste gate. I leaning toward pop off. But if the waste gate slams shut upon acceleration and does not open, it will overboost and pop off.

Any ideas?

[esprits4de]

'83 Turbo

When I run my car past 3000 rpm my pop off, well, pops off and stays open until I change gears. It happened intermittently to start but now its all the time. I have a boost controller on the waste gate. My turbo has about 2000 miles on it. My boost has alway read a little high on my gauge, 10psi. I believe the car is set up that way, as it runs a little rich at low speed. I can also feel a loss of power at pop off, 3000 rpm. The boost reads 10psi even after pop off.

So, it is either the pop off or the waste gate. I leaning toward pop off. But if the waste gate slams shut upon acceleration and does not open, it will overboost and pop off.

Any ideas?

What type of pop-of ? Some are known to get sticky springs.

Sounds like it.

[bigsi]

you could check the wastegate assy but stripping it like i have done.

be very very careful though.

get the car up on stands, get under by wastegate, undo the 4 bolts around the top of the unit, make sure you hold the bottom cup against the top tightly as the spring will throw it off otherwise and ifthe diaphram is stuck anywhere it could tear.

then carefully allow the cup to lower, if all is ok you will then be ablt to take the cup and spring away.

the diaphram is secured by two nuts underneath the valve stem, there is a metal recieving cup inside for the spring head, the other side of the diaphram is a metal retainer disk.undo the nuts, remove items and then check on the movement of the valve, if stiff, get a dremel with a rotary wire brush head and clean around the valve stem, apply some copper grease and move back and forth in the valve stem guide.

things should move easier, clean inside the top cup and if your diaphram is not torn or split but covered in gunk, gently wipe with some kitchen paper.

reassemble, but do not forget either side of the wastegate diaphram is a thin paper gasket that protects it from sticking to any of the parts of the assembly, you will have to either make some or buy some from pnm engineering. re attatch diaphram after placing first gasket on top cup thenplace one on the top of the seperator section and drop spring into cup then put one bolt through the top of the cup and push the bottom cup up to meet against the top section.

when you have enough closure tighten the first bolt a little amount, a couple of threads will do, then on the opposite side do the same then the remaining two bolts.

to tighten do this in an every other way same as tightening the wheel nuts back up after taking them off.

i will have pics on re-assembly for my thread shortly anyway.

hope this helps

si

[1984_lotus_esprit]

I used a second screw type jack stand to press up against the bottom of the waste gate

housing helped when reassembling. I found that trying to keep the all the holes in line, pressing

up against the waste gate spring and turning the long screws in the space limited

location rather difficult. My waste gate was sticking and needed a cleaning.

[bigsi]

im lucky as my whole wastegate assembly has been romoved from the manifold.

Edited January 19, 2007 by bigsi

[WayneB]

Clay, the factory dump valve is set to blow off at 12psi.

Are you getting your figure of 10psi from the factory Smiths boost gauge? They are not the most accurate of gauges and it might be giving you a falsely low reading.

8 psi=.55bar 10 psi =.68 bar 12psi=.82 bar

Either your boost controller is set too high or the fact your wastegate is now not operating as frequently as it should (when set to 8psi) its probably stuck and needs freeing off.

It might not be a bad idea to set it to 8psi for your normal driving (to operate the wastegate more often) and set it to 10 psi occasionally when you want more power.

[cly_mitchell]

Clay, the factory dump valve is set to blow off at 12psi.

Are you getting your figure of 10psi from the factory Smiths boost gauge? They are not the most accurate of gauges and it might be giving you a falsely low reading.

8 psi=.55bar 10 psi =.68 bar 12psi=.82 bar

Either your boost controller is set too high or the fact your wastegate is now not operating as frequently as it should (when set to 8psi) its probably stuck and needs freeing off.

It might not be a bad idea to set it to 8psi for your normal driving (to operate the wastegate more often) and set it to 10 psi occasionally when you want more power.

Thanks for all the input. Sounds like a wastegate cleaning is in my near future.

[dodgy]

Clay, the factory dump valve is set to blow off at 12psi.

Are you getting your figure of 10psi from the factory Smiths boost gauge? They are not the most accurate of gauges and it might be giving you a falsely low reading.

8 psi=.55bar 10 psi =.68 bar 12psi=.82 bar

Either your boost controller is set too high or the fact your wastegate is now not operating as frequently as it should (when set to 8psi) its probably stuck and needs freeing off.

It might not be a bad idea to set it to 8psi for your normal driving (to operate the wastegate more often) and set it to 10 psi occasionally when you want more power.

have you any idea how to set the pressure Wayne?

[WayneB]

Dave, they come pre-set at what ever the riveted tag says

As Ive never found any shims under the spring I presume they use springs of different tensions at Garrett to set the pressure.

You can also alter the pressure by putting a plate under the spring and winding a bolt through the tapped hole in the bottom of the diaphragm housing (to increase tension on the spring) or you could just shim the spring until you get to the level of boost you require.

You couds also make it adjustable by either regulating the manifold pressure to the diaphagm (with a screw type regulator) or by applying some manifold boost pressure to the underneath of the diaphagm ( via the tapped hole in the housing) creating extra resistance for the pmanifold pressure to overcome, again using a regulator which with long enough pipe could be mounted in the cabin.

Ive never used one of those electronic boost controllers, but I hear they work OK too.

.

[1984_lotus_esprit]

I'm not keen on these little external valves I see being sold and advertised. S3 waste gate

regulates boost pressure based upon the boost air pressing against the waste gate's piston

and reacting against the spring on the other side of the piston. Attempting to regulate

the pressure by not either changing the spring or size of the piston on non computer

controlled S3s, doesn't really change the waste gates performance. Putting in a

bolt in the waste gate to limit the travel distance of piston, only makes the boost system

go "open loop" and provide uncontrolled boost once the mechanical stop is encountered.

I wasn't sure if a 10psi spring from new Esprit Waste Gate would fit, so I went to local

tooling and machine shops hunting for medium sized steel springs.

I set my waste gate to 12 psi by adding a second spring into the waste gate assembly.

I couldn't find one locally at hardware stores and tooling shops that was the right diameter

and spring K force/inch displacement. It took me about 4 or 5 tries of hunting and pecking

before I got a spring combination that provided the pressure regulation I desired.

My car has been running this higher pressure for 5 years. To me this is a "no brainer" to

where a valve can't get bumped to a dangerously high boost level.

When the season gets warm again, I plan on cleaning and re-adjusting the safety pop off valve.

When my car is "cold" it pops off at 12psi at the edge of my waste gate's regulation point, but

when the engine is warm the pop off valve goes at 14psi. I want to clean it, and adjust it

to where it pop's off at a more consistent 14psi to 15 psi. Up until last year, it was a consistent

15 psi, but from aging, it appears to have degraded a little.

Edited January 20, 2007 by 1984_lotus_esprit

[WayneB]

On the method that uses a bolt and plate bearing on the wastegates spring I forgot to mention the spacer that is put in between the top and bottom of the diaphagm housing (alowing the wastegate valve to go through its full lenth of travel)

I use a cabin mounted regulator, supplying regulated manifold pressure to the underneath of the diagphagm.

Mine is set for 10 psi

It works quite well.

This is the same way Zakspeed, Porsche and Toyota GB used to do it on the racecars that used this type of Garrett Airesearch non-integral wastegate back in the 70s/80s

Adding that extra spring was a clever method of doing it though!

[bigsi]

wayne look here at the pictures of mine, there are two washers before the top plate. this is how mine was when i opened it up.

http://www.glcforum.com/esprit/forums/inde...?showtopic=7812

[WayneB]

Yes, I see what you mean Simon, spacing the valve further away from the spring, pushing it up harder into the seat on the wastegate adapter (with the washers) would put the spring under compression increasing its resistance to boost pressure.

Edited January 20, 2007 by WayneB

[1984_lotus_esprit]

My waste gate casting has arc shaped vents to allow the air on the spring side to escape as the piston

travels, these would have to get plugged to allow that area to pressurize. And the spring

that was in my waste gate, was a linear type, so that no matter what one did with the adjustment

bolt, the force/displacement was always the same (I checked by compressing it with bar bell weights

and measuring the displacement). Adjusting the bolt would make sense as a pressure tuning method

if the spring is wound in a progressive manner to give more K or force/displacement as the

spring became compressed, but my waste gate spring wasn't wound in such a manner. So not all

waste gate assemblies are designed the same.

Gee Wayne, isn't it cold where you are at??? 250 miles east of me. I just got cold going to my

garage and looking under my car with a flash light to remind me of what my waste gate

assembly's unique physical features looked like. In that amount of time, it looks like you took

your waste gate apart.

[WayneB]

Thats the pic Simon posted of his waste gate diaphragm and valve..

I dont have any pics of mine apart as I didnt take any 6 years ago.

Yes its bloody cold today

My 1983 diaphagm housing is a solid (windowless) casting, maybe later versions were different (to try and combat tampering)

I doubt Lotus wanted people to be able to raise the boost pressure of the cars (whilst they were still under warranty)

[cly_mitchell]

The way the boost control works is a hose that runs from the wate gate to a valve in the cabin and from that valve to the mainfold. I have never adjusted it. It was installed by the PO. The motor is new, built by Auto Europe in Detriot. I thought they set the motor up so I haven't messed with it.

I feel the problem is with the pop off. Its either a weak spring or just needs cleaning.

As Ive never found any shims under the spring I presume they use springs of different tensions at Garrett to set the pressure.

You can also alter the pressure by putting a plate under the spring and winding a bolt through the tapped hole in the bottom of the diaphragm housing (to increase tension on the spring) or you could just shim the spring until you get to the level of boost you require.

You couds also make it adjustable by either regulating the manifold pressure to the diaphagm (with a screw type regulator) or by applying some manifold boost pressure to the underneath of the diaphagm ( via the tapped hole in the housing) creating extra resistance for the pmanifold pressure to overcome, again using a regulator which with long enough pipe could be mounted in the cabin.

Ive never used one of those electronic boost controllers, but I hear they work OK too.

.