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+--- Thread: Calling all experts (/showthread.php?tid=7400)
Calling all experts - mantahead - 09-08-2016
hi,
i have a problem where the car splutters under load and puts out light grey smoke, it is far more noticeable when i run the turbo and supercharger together.
once the rear wheels break traction, she clears herself and is as sweet as a nut.
pump timing is correct, egts are normal, this is the second engine that has done this with the same setup, so that should rule out injectors.
All thoughts welcome.
here is a video that shows it at the start and then again at 58 seconds
https://youtu.be/FFIfP5Y68z0
RE: Calling all experts - hooblah - 09-08-2016
Main pulley hasn't sheared the key and spun has it?
RE: Calling all experts - mantahead - 09-08-2016
hi,
crank pulley?
i have extra key in it and on first engine as well.
RE: Calling all experts - R-3350 - 09-08-2016
the two things that come to mind are valve sealing and pre-chambers.
i hear what your talking about not quite sure exactly what it could be it sounds familiar though. i have had some aviation engines apart that had similar things at part load. turned out to be poor sealing on the exhaust valves from carbon buildup maybe when you have some maintenance time try a leak down test. another idea might be to look at your pre-chambers i have heard of various strange symptoms from them. if you do a leak down test and its leaking from the valves try staking them. you might have carbon build up between the seat and valve. the easiest way to get rid of it without pulling the engine apart is to feed compressed air into the cylinder like your doing a leak down test then with the valve cover off smack the valve rockers with a rubber mallet near the valve stem. or in an ohc engine use a stiff wooden dowel to hit the buckets. it makes a dramatic noise but its great at cleaning the seats and valves. its what we do in aviation to clean problematic cylinders so we don't have to overhaul an engine ( a full overhaul on large engines can run over 15000$)
RE: Calling all experts - TurboTim - 09-08-2016
Could the turbo be stalling out from trying to do too high of a pressure ratio at too low of air flow. I could see this happening because you have a supercharger and it's actually possible to boost at low rpm. Can you underdrive the supercharger and see if it goes away?
RE: Calling all experts - mantahead - 09-09-2016
hi,
aha, i wan't to put the question out before i commented, we are thinking the same thing,
my theory is that the shear amount of volume of air at low rpm has no where to go and can't get past the turbo wheel, and then that dirty air is getting back past the exhaust valves and into the cylinder, there is then no oxygen to burn the fuel.
the two wastegates on the exhaust manifold are set at 2.1 bar.
i fitted another wastegate on the supercharger set at 1 bar inlet manifold pressure.
these engines are known to have weak springs.
i have changed the supercharger drive ratio from 2.66 to 1.77 over crank,
i still have the same problem.
when the wheels are spinning she is clear, when the tyres are gripping the road she is not.
Also engine is still overheating.
RE: Calling all experts - F.R.A.S - 09-09-2016
Sounds like a valve spring problem to me.
RE: Calling all experts - barrote - 09-09-2016
Well , my engine does the same, or did the same, folowing that , or at the same time don´t u have nailing sounds acopanied by random cylinder failures , like it was in 3 or 4 cylinder?
if thats the case easy "springs" week springs . or said in other way too high EGP , the valve lifters compensate for a small opening and the engines cylinders leak, causing low compression temp/press , folowed by grey white smoke.
Since u have that Compressor screaming around probably u can´t hear the nailing.
RE: Calling all experts - mantahead - 09-09-2016
hi,
yea its like very bad nailing and off at least 2 cylinders and then smoke.
thats why i wiggle the car about to break traction, because i know once i break traction the engine will clear, lol
RE: Calling all experts - barrote - 09-10-2016
yep , as FRAS said , that improves with springs , but the thing is about the load on the EGP side , try to run it with less load on the exaust valves, or try some harder ones ...... there is risk of colision
good luck