Vacuum Accesories on a turboed engine



How would you run Vacuum accesories with a turbo?..Especially the brake booster?...would you have to use an airpump?..or hydraluc booster?
or a booster made for turbos?
You tap them off the inlet prior to the turbo. Use a vacuum reservoir, too. This is a sealed tank with a check-valved inlet, and an outlet hose that can be teed off to all required vacuum accessories.

Regards, Adam.
If there isn't a good signal there, for some reason, the diesel powered cars and trucks come with a vacuum pump.

There in the junk yards.

Diesels come with a pump because they don't make any vacuum at all, even when their foot is off the go-pedal. A regular turbo motor makes vacuum when your foot is off the gas just like a regular motor.

8) where you draw vacuum from depends on you set up. a draw through setup you pull vacuum from the base of the carb before the turbo. on a blow through setup you still draw from the carb base, but you need to install a one way check valve to prevent vacuum accessories seeing boost pressure, with the exception of the dist vacuum advance. if you have the right canister there you can use it as a boost retard system.
BTW, you may be in trouble if you have an old-style automatic tranny that needs vacuum signal for control. You might be able to make a draw through work but not a blow through.
run one line form teh inlet of the turbo with a check valve to a vac canister. then another line with check form the manifold. one works while off boost and the other while under boost.

I dont think there will be a problem with the vaccuum signals. My dad and brother built a draw thru turbo 200 with the vaccuum ports in the manifold and everything worked just fine.
Ok..i prolly woud have thought of it sooner or later, just couldnt of those things that you just cant get trhough your head. Thank you much....

Im planning on a blow through, so a vacuum resevoir with a check vavle sounds good. Im not running many accesories and my tranny is a manual 4 speed. Its in a 74 ford everything is mecahnical riht now....just getting stuff together along with ideas of how to do stuff so i dont have to figure them out later.
How would you get vaccum ahead of the turbo? With no restrictions (hopefully) ahead of the turbo there should be no vaccum. Or at least not enough to matter. The same as deisels not producing vaccum in the intake manifold because there is no restriction like the throttle plates in a carb. Also the same as a carb/gas engine at W.O.T. Somewhere around 1.5 inches or less. And I thought they only got that much because the carb body itself was a slight restriction.

Not trying to make waves, but it just doesn't make sense to me. :(
You are right!...hmm...thinking....theres a way..i know there is..just cant think of anything off the top of my head and i havent spent too many hours over a turboed engine to realizer how its done or find out how its doen...but its done..theres too many turboed gas engines out there to be this type of puzzle...its gotta be simple...

Would the lines coming to and from the vacuum canister be the restrictions to create a vacuum in the canister? When the turbo is sucking air from the canister, it becomes under negative pressure?..the engine is sucking air from the canister when there is no boost at idle. hence the check valves to keep the booster from blowing through the canister into the engine manifold and the check valve to keep the engine from pulling airthrouhg the canister from the turbo side?

Someone tell me if thats right?....i dont think totally....but partially? :x
let me try and say it again. There will be no vaccuum problems with a turbo. Just hook up as a normaly aspirated engine and you will be fine. There will always be vaccuum in the manifold.
SnowDragon3":97e83fgt said:
let me try and say it again. There will be no vaccuum problems with a turbo. Just hook up as a normaly aspirated engine and you will be fine. There will always be vaccuum in the manifold.

Not with a blow-through and not with most EFI applications where the T/B is mounted downstream of the turbo.
8) and not under boost. if you are going to use a blow through setup, use a vacuum pump. either the electric one gm uses on their diesel cars or the engine driven ones ford uses one their diesel trucks.
You don't need the pump. It is not needed on a throttled engine. The only reason diesels use them is because they are unthrottled. For the most part, if you put your foot to the floor on a N/A engine, you're not going to have very much of a vacuum. The only time you get a decent vacuum is when your foot is out of the throttle (either off or light-throttle cruise), which will give you a vacuum whether you have a turbo or not.

I havent delt with EFI so I cant vouch for that. But we have built a running Turbocharged Ford 200, and all vacuum hookups work just as a N/A engine.
Vacuum is produced when the engine calls for more air and the butterflies are closed, creating a vacuum with or with out a turbo.
How about with the vacuum modulator on the C4? It reads low vacuum at WOT and helps hold the shift. There are different "color striped" modulators for different vacuum pressures, but what will it do when it sees 7 or even 15psi at WOT?
Now you're making things difficult! Back to my original comments about pre-the forcing implement. Rootes style superchargers can't run vacuum accessories in the way outlined for light turboing above. Look at a blown car, and see where the booster vac line comes from.

I don't know whether it's a straight tee, or some kind of venturi effect created, but taking the vacuum before the forcing would be one way to go with a C4; the other is full manual. :p

Cheers, Adam.
My old Cortina V6 ran a blow through setup. The stock Solex 35 2-bbl throttle body had all the fittings in the standard postions. The solution to the C3 modulator valve was to get rid of the trans and replace it with a US 2.8 Mustang C4! Then you have similar problems with it!

My solution was to:- the 1956 Ford Prefect's vacum canistor (this allows you to build residual vacum under certain conditions).
2.The Impco LPG carb runs a balance line which allows the carb to communicate to the convertor. No fuel pump, no rising rate fuel pressure issues.
3.Limit boost to 6 pounds. (My IHI RB06 or whatever it was was too small, and was given to me by a work mate off his old Fiat 125P Turbo!). Downside was an engine with about 115 hp at 5200rpm only got to about 155 hp estimated...still lots of fun in a little 2450 pound car that would rev to over 6500 grand or more!

The brakes were always boosted correctly, but the modulator set-up was a real pest, and I never was able to make it shift as well as it should. The booster ran off the Prefect's vacum canistor, and the modulator off an old White Air meter reservoir used for concrete testing.

The Holley Performace book talks about boost referencing. If you can make the trans "see" the normal vaccum, you can do anything.

In most normal sitations, 6 pounds of boost is not enough to create a situation where there is no vacuum for brake boosters and auto trans modulation. Above 15 pounds, there sure is!