fast tickover help
Discussion
I have just fitted a set of ported 4.2 inlets to my 4.5. The butterflies have been increased in size to 48mm the spindles thinned and the inlet tract widened and polished and matched to the cylinder head.
I have fitted the new system and have been very careful on its assembly using new o rings etc on its assembly.
I set up all the throttle pot's etc to the recommended (and various other settings) postion and monitor the lamdas etc using a laptop...all seems fine. Lamdas trigger, adatives adjust etc etc No faults on the screen.
If I reset the adaptives and start the car from HOT or COLD the engine fires up and ticksover at 950rpm....all fine. However as the engine increase in temperature and the ecu starts to adjust the mixture, the engine speed increases to 1450rpm and I cannot get it to drop. The throttles are fully closed, the throttle stops are wound out of the way and the link bar is removed. I cannot seem to find any air leaks.
Am I missing something? Any ideas on what might be causing this and how I can resolve or is it definatley just too much air getting in.
I am using the 4.5 injectors in the 4.2 manifold but I dont think this is a problem.
I have fitted the new system and have been very careful on its assembly using new o rings etc on its assembly.
I set up all the throttle pot's etc to the recommended (and various other settings) postion and monitor the lamdas etc using a laptop...all seems fine. Lamdas trigger, adatives adjust etc etc No faults on the screen.
If I reset the adaptives and start the car from HOT or COLD the engine fires up and ticksover at 950rpm....all fine. However as the engine increase in temperature and the ecu starts to adjust the mixture, the engine speed increases to 1450rpm and I cannot get it to drop. The throttles are fully closed, the throttle stops are wound out of the way and the link bar is removed. I cannot seem to find any air leaks.
Am I missing something? Any ideas on what might be causing this and how I can resolve or is it definatley just too much air getting in.
I am using the 4.5 injectors in the 4.2 manifold but I dont think this is a problem.
Air is getting into the manifold, bypassing the butterflies as the manifold expands.
This will not be easy to find.
Could be that the butterflies are not a good fit, or that the machining was done without the inlets bolted to the heads.
Or just unlucky. But is sounds like its all comming apart again..
This will not be easy to find.
Could be that the butterflies are not a good fit, or that the machining was done without the inlets bolted to the heads.
Or just unlucky. But is sounds like its all comming apart again.
.Definitely either an air leak or more likely the air gaps around the throttles are too big.
I have some experience of this as when I put my ported inlet manifolds back on I had a hard job getting the idle down. Even now, my idle is set with the idle screws fully out and the engine settles at around 1000rpm when hot.
I would recommend you remove the throttles and check that they are air tight with the throttles closed. Changing the butterflies around may help a bit.
I have some experience of this as when I put my ported inlet manifolds back on I had a hard job getting the idle down. Even now, my idle is set with the idle screws fully out and the engine settles at around 1000rpm when hot.
I would recommend you remove the throttles and check that they are air tight with the throttles closed. Changing the butterflies around may help a bit.
I agree with you guys and think the most likley cause is leakage around the butterflys. What I cant understand is the new butterflys fit far better in their manifolds than the original 4.5 ones. If you shine a light from behind the butterflys the original 4.5 has gaps everwhere. The new system has virtually no light passing around the edge.
The only thing I can think that may explain this is that the original 4.5 had petrol sprayed all over the front of the butterfly as the injector is on the airbox side.
This may have helped seal the gaps but in my mind appears to be a silly position to put the injector. Lucas and seimems spend 1000's of pounds developing a perfect atomised spray pattern and TVR then go and trash it by letting the fuel dribble round the butterfly.
The only thing I can think that may explain this is that the original 4.5 had petrol sprayed all over the front of the butterfly as the injector is on the airbox side.
This may have helped seal the gaps but in my mind appears to be a silly position to put the injector. Lucas and seimems spend 1000's of pounds developing a perfect atomised spray pattern and TVR then go and trash it by letting the fuel dribble round the butterfly.
before dismantling try spraying the carb cleaner around where the inlets bolt to the head (so long as it won't damage any of the seal there, youll have to ask around / check sensibility first) - it may not be leaking past butterflies, but leaking where the whole assy fits on the head?
I had this on another car years ago, turned out to be air leak under the carb, found it with a tin of WD40, just sprayed it around until the fault dissapeared, turns out I was one of the numpties who had tightened the sprung bolts up fully and crushed the o rings! How we live and learn :P
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