Low vacuum readings

[zaq123]

ive got the other style vacuum system connect direct from booster to post throttle without the other line. dont know what the function of the additional line is. if it a straight Y-piece isnt it just a leak?

It's not the straight Y, just like reaoem description says - air pump aka jet pump aka venturi pump. Below is a cross section from e39 but e30 one has a similar idea behind it

[Julien]

M52b25 injectors are 17.5lb/hr 4 point spray. I know they're larger than stock but ECU adapts easily.

Turns the cause was valve clearances. Today we adjusted them 0.20mm at camshaft side. On some valves the gaps were 0.10mm and smaller - last time we adjusted them when head was on table. Problem solved, the idle is good now on LPG, need to clean injectors for gas to work properly but otherwise it's good. Haven't checked vacuum yet tho

Did the vacuum change?

[Mixzzz]

ive got the other style vacuum system connect direct from booster to post throttle without the other line. dont know what the function of the additional line is. if it a straight Y-piece isnt it just a leak?

It seems like it is just some kind of bypass and removing didn't change a lot... Also is ICV supposed to be spring loaded? Because my doesn't spring back when closed...

[digger]

ive got the other style vacuum system connect direct from booster to post throttle without the other line. dont know what the function of the additional line is. if it a straight Y-piece isnt it just a leak?

[Mixzzz]

that link takes me to the realOEM homepage so not sure the part you mean

Fixed

[digger]

that link takes me to the realOEM homepage so not sure the part you mean

[Mixzzz]

Yeah you always need to adjust them after you torque the head onto the block. Tight clearances increase overlap so Vacuum should improve making it correct

http://www.realoem.com/bmw/enUS/show...diagId=11_0861
I was wondering whether part #1 is just a tube that just splits or there should be something in there? Because mine is empty and I quite can't seem to understand the point of it.

[digger]

Yeah you always need to adjust them after you torque the head onto the block. Tight clearances increase overlap so Vacuum should improve making it correct

[Mixzzz]

the engine the cam came from was a stock 2L, they seem to idle fine they use basically identical electronics to the m20b25 but different chip. the smaller engine wouldn't cope as well as a bigger engine.

people use a 272 cam upgrade sometimes which actually increases overlap, it idles not quite as smooth but perfectly fine if the rest of the system is in good condition

if you had it as far off as a tooth i could see some issues but a few degrees i cant see it causing a 20% change, note without hearing how it sounds and the exact symptoms it it is hard to diagnose. maybe the stock motronic is much more fussy than the ECU i use but like i said it worked fine in a m20b20 engine

on a 4V per cylinder engine with separate inlet and exhaust cam it would make a noticeable difference

you can get an adjustable cam gear and new timing belt and set it up in the straight up position, its not that difficult. you might find you prefer it retarded for how it drives

what does the compression test say? you would hope the valves are sealing that is for sure...

what are the specs of the M52b25 injectors?

M52b25 injectors are 17.5lb/hr 4 point spray. I know they're larger than stock but ECU adapts easily.

Turns the cause was valve clearances. Today we adjusted them 0.20mm at camshaft side. On some valves the gaps were 0.10mm and smaller - last time we adjusted them when head was on table. Problem solved, the idle is good now on LPG, need to clean injectors for gas to work properly but otherwise it's good. Haven't checked vacuum yet tho

[digger]

the engine the cam came from was a stock 2L, they seem to idle fine they use basically identical electronics to the m20b25 but different chip. the smaller engine wouldn't cope as well as a bigger engine.

people use a 272 cam upgrade sometimes which actually increases overlap, it idles not quite as smooth but perfectly fine if the rest of the system is in good condition

if you had it as far off as a tooth i could see some issues but a few degrees i cant see it causing a 20% change, note without hearing how it sounds and the exact symptoms it it is hard to diagnose. maybe the stock motronic is much more fussy than the ECU i use but like i said it worked fine in a m20b20 engine

on a 4V per cylinder engine with separate inlet and exhaust cam it would make a noticeable difference

you can get an adjustable cam gear and new timing belt and set it up in the straight up position, its not that difficult. you might find you prefer it retarded for how it drives

what does the compression test say? you would hope the valves are sealing that is for sure...

what are the specs of the M52b25 injectors?

[Mixzzz]

the big thing that reduces engine vacuum is cam overlap. when you advance the cam the overlap doesn't change. ive advanced cams 8* before and there was no real difference in idle quality (i never checked vacuum though). you can get an adjustable cam gear for the m20 but i would be looking elsewhere for issues first. do a smoke test, etc

Well, today we plugged literally every hole that it had and the vacuum didn't change a bit, it was at 52kpa, maybe went up to 55kpa but not for long. Had to use silicone on the thing that screws onto manifold with three screws and has a tube running to fpa. I am really starting to think that it has to do something with the cam timing, some more sources confirm, that when running a retarded cam you get better vacuum and smoother idle.

[Mixzzz]

Using oil has nothing to do with good or bad compression. It's a good test to do. Depending what you find a leakdown might also help

If I'm losing compression the only place where it could leak is past compression rings cause I doubt that valves would could be leaking already after the machine shop.

[digger]

Using oil has nothing to do with good or bad compression. It's a good test to do. Depending what you find a leakdown might also help

[Mixzzz]

youtube will have some

Im going to do a compression test tomorrow, but my dad doubts theres a problem in compression since my engine is not using oil(after 9Kkm it has used only 0.6l and some of that leaked out due to small crack in HG). Is it possible for compression rings to go bad but the oil control ring could still be good? Also if my compression readings are good, should I still try to do the leakdown test?

[digger]

youtube will have some