So I’ve been doing some reading back on posts, and found the above diagram which is really useful to help me understand what’s going on.
Basically, my car has had some modification in the past… which I think might be causing my problem.
After a trackday yesterday, when the car ran pretty well…the journey home the car was stuttering and jerking and the fuel gauge drops almost visibly… it’s obviously running rich…the smell of fumes is overwhelming at times.
So… the vaccum circuit on my car now looks like this :-
FuelPressureReg → InletTracts → MapSensor
and then :-
VacuumReservoir → Locking Solenoid → Charging Solenoid - Blanked Off Pipe (there is no Resonator Valve)
According to the diagram above, the Vacuum Reservoir should be connected into the Map Sensor hose too…could this be the cause of all my problems ???
Noticed Uldis seemed to understand this system pretty well… can you help ??
Yes, that is wrong.
Don’t know if you have a Lotus ECU or Emerald, but the latter doesn’t use the MAP sensor in the mapping (you could, and it would be good, but Dave Andrews doen’t normally map the MAP)
Anyway, the vaccuum reservoir is there in fact to smooth out the vaccuum pulses and store them for the fuel pressure regulator.
It serves absolutely no purpose on the resonator valve circuit, now that you have eliminated it.
I recommend you plumb in the vaccum reservoir to your first circuit (pressure regulator/MAP) and get rid of all the other solenoids which, not having the resonator valve, don’t do anything and are just another possible pipe to leak.
In fact, when I was having trouble with mine, upon removal, found a pipe with a leak, the b@stard!
Make sure anything you remove is sealed properly, you don’t want any extrra leaks there.
Yes, that is wrong.
Don’t know if you have a Lotus ECU or Emerald, but the latter doesn’t use the MAP sensor in the mapping (you could, and it would be good, but Dave Andrews doen’t normally map the MAP)
Anyway, the vaccuum reservoir is there in fact to smooth out the vaccuum pulses and store them for the fuel pressure regulator.
It serves absolutely no purpose on the resonator valve circuit, now that you have eliminated it.
I recommend you plumb in the vaccum reservoir to your first circuit (pressure regulator/MAP) and get rid of all the other solenoids which, not having the resonator valve, don’t do anything and are just another possible pipe to leak.
In fact, when I was having trouble with mine, upon removal, found a pipe with a leak, the b@stard!
Make sure anything you remove is sealed properly, you don’t want any extrra leaks there.
Good luck!
Superb…thanks Uldis… Standard ECU for me (still 177).
I actually did this today after looking at some of the pics you put on bookatrack… I figured it would be worth trying at least !
Seems to have helped I think, took it out for a quick spin and it seemed better. I still have the other circuit in at the moment so might look at blanking that off too.
Incidentally, what is the thing next to the MAP sensor that looks just like the MAP sensor ? - it looks to have an attachment point for a hose, but it’s not connected in my car and wasn’t in your pictures either ?
Thanks for your help mate !
Also made a ‘heath robinson’ extension to the air intake pipe to hook directly up to the side intake scoop…hopefully this will help too.
On the subject of MAP, one of the worst aspects of the Exige’s mapping is its use of the MAP signal to assess engine load, the cams used on the Exige engine have far too much duration to give a stable MAP signal at idle and low engine speed/load, hence the engine’s general running on low load and progression is poor since the ECU cannot accurately assess the engine’s requirements.
Mapping using Alpha-n (throttle position and engine speed)is far superior in these situations and the Emerald ECU deliberately makes little or no use of the MAP signal, as a result, progression, idle and low speed running are transformed allowing jerk free progression and smooth running in traffic. Reverting to the use of MAP on an engine like the Exige’s would not be ‘good’ it would be a retrograde step.
Have a read of the EMS article I have written which is published on my website and on Emertald’s for more details and a broader explanation.
Incidentally, what is the thing next to the MAP sensor that looks just like the MAP sensor ? - it looks to have an attachment point for a hose, but it’s not connected in my car and wasn’t in your pictures either ?
I seem to recall it’s the barometric sensor. Would be good to use it on the mapping so it can compensate at high alktitudes (Alps).
Dave for what its worth I’ve had exactly the same trouble.
Eventually traced it to the vacuum pipes coming out of the intet manifold having split due to heat…Very dificult to spot but having replaced them with new Vacuum hose( this is important as the petrol pipe I tried expanded in the heat and fell off) everything is fine
To add to the confusion my vacuum pipe runs directly to the MAP and the pipes from the vacuum tank just dangle in the breeze.
Dave for what its worth I’ve had exactly the same trouble.
Eventually traced it to the vacuum pipes coming out of the inlet manifold having split due to heat…Very dificult to spot but having replaced them with new Vacuum hose( this is important as the petrol pipe I tried expanded in the heat and fell off) everything is fine
To add to the confusion my vacuum pipe runs directly to the MAP and the pipes from the vacuum tank just dangle in the breeze.
I had the same thing with the vacuum pipe that leads to the inlet ports on the throttle bodies…that’s what got me looking at the whole system…
After trying several different pipes, I now have some Samco hose on all of the FuelPressureReg → Inlet Ports → MAP sensor + Vacuum Chamber.
If you have dangling hoses, I suggest you re-plumb it and blank the necessary bits off… It won’t run right if they are open to the atmosphere…
I had similar problems, and after replacing the TPS (probably a red herring) I set about changing all the vacuum pipes. Whilst doing this I noticed that one of the plastic T pieces which lie along side the cylinder head and broken, but because the whole lot is tight up against the head you couldn’t see it!. anyways, I replaced all pipes and T pieces and its back to its old self
If you want another T piece you might be able to re-use one of the ones from the various vacuum canister / solenoids - failing that just use a windscreen washer T-Piece BUT make sure it hasn’t got a one way valve in it though!
![http://www.corelabs.net/Vacuumreservoircircuitdiagram.jpg[/image]](http://www.corelabs.net/Vacuumreservoircircuitdiagram.jpg%5B/image%5D){kind=link}