Suction jet pump stock setup/ITBs question

[zaq123]

Anyone using stock SJP with ITBs? Trying to keep any vacuum I can. Am I understand correctly that it will influence the idle? Looks like newer BMWs have a solenoid to keep that idle influence under control (makes a sense) but e30 doesn't have one.
How does stock SJP setup doesn't influence the idle? I can't wrap my head around it

[digger]

What is a suction jet pump ? If you mean a seperate vacuum pump don't worry about it initially it probably won't be required. It doesn't affect idle anyway

[TobyB]

There are 2 of those- one in the gas tank of a plastic bumper car,
one attached to the brake booster of similar cars.

I took mine out- it was just too ugly to contemplate. I have yet to lose
brake boost- and this, on a PRO3 car.

It only really works under significant throttle- at idle, the booster is pulled
down to manifold, so it can't be a vacuum leak.

fwiw.

t

[ForcedFirebird]

What are you trying to keep vacuum for? The e30 doesn't rely on vac for anything except the brake booster, which has a diaphragm in itself. In my GM building days, the A/C controls are actuated via vacuum, so they had a vacuum ball to hold vac, and many guys modified them when running larger cams...

https://www.gmpartscenter.net/oem-parts/gm-tank-asm-crcont-vac-dia-156-0mm-14056624?origin=pla&gclid=Cj0KCQiAsJfhBRCaARIsAO68ZM4kNARR21mylP9kpsfybD7H1Z1jPzuhMrqcdRvq1nWD2B7FI--Xm5saAkSFEALw_wcB

[zaq123]

Thank for replies guys. I meant a venturi pump for the brake booster. Just not sure if I should integrate it into ITB setup to help the booster in any low vacuum situations. I understand how it works but don’t understand how it doesn’t affect idle on stock e30 since it is a constant vacuum leak. On newer Bmw’s, they use a solenoid to control the leak but on e30, it is always open and basically works like ICV with a small opening.


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[ForcedFirebird]

FWIW the e30 m20 with ITB and pulling vac from a single runner works great.

[e30davie]

Thank for replies guys. I meant a venturi pump for the brake booster. Just not sure if I should integrate it into ITB setup to help the booster in any low vacuum situations. I understand how it works but don’t understand how it doesn’t affect idle on stock e30 since it is a constant vacuum leak. On newer Bmw’s, they use a solenoid to control the leak but on e30, it is always open and basically works like ICV with a small opening.


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Can you explain how it works? and why they even have it?

On my m20blocked off the "return" of the pump on the brake booster, mainly cause i changed the intake and it no longer has a home. Can i just run a normal vacuum line with a non return valve like every other car ive ever seen? would be much neater...

[zaq123]

Can you explain how it works? and why they even have it?

On my m20blocked off the "return" of the pump on the brake booster, mainly cause i changed the intake and it no longer has a home. Can i just run a normal vacuum line with a non return valve like every other car ive ever seen? would be much neater...

jet pump is there to increase the vacuum. On e30, it is serving only the brake booster. On some modern boosted cars where the vacuum is an issue, they can run all kind of things while replacing mechanical/electrical pump. i.e. 4wd control system etc

The idea is simple: pump uses the air that gets sucked in by the engine from the intake boot into the intake manifold (bypassing TB). The Venturi effect creates a low-pressure zone at the throat of the pump and that that low-pressure zone gets connected to the brake booster, increasing available vacuum.

[ForcedFirebird]

All the ITB kits we have installed just deleted the suctiin pump on the cars that had it (not all m20's did). Just run the booster hose to a single in/out check valve and to a runner or vacuum block. Brakes work fine on all the cars we have done.

[e30davie]

Thanks for the explanation. Seems like a good idea in theory. In practice I'm not sure how much difference it makes. But i suppose bmw did it for a reason?

[ForcedFirebird]

Only some e30's have them, e36's didn't get them.

[digger]

keep it simple, you dont have a lairy cam so you arent going to lose a ton of vacuum

[zaq123]

Only some e30's have them, e36's didn't get them.

Yeap, I think e39s got them next. Later BMW started to use a solenoid to control pump's air flow

https://www.newtis.info/tisv2/a/en/e64-635d-cab/repair-manuals/11-engine/2MTHLBB