What to call a thread about 2 stage boost controllers? :)

[hillfolk'r]

yea i guess its better to keep boost in,than vent it to atmosphere,,how doi restrict it,,take anyshop air regulator,withan airhose  attatched,and put an open airchuck in it,with the thing closed,,start dialing it slowly,,air passes slowly,,turn it more,more air,,well just use this idea "backwards" to raise boost,,,,i do have a couple of those air switches around but idlike tofind one witha larger hose attachment,,,they only have like a 1/4inch airline push on fitting,,it may work ok,,,,actually something is wierd  now using this turbo on the 1.9,,its  lowest boost islike 14 psi,,used tobe like 10-11 on the 1.6,,must be extra exhaust volume overwhelms wastegate?

[Baxter]

So, for a restrictor I could use the bleed valve like the e-bay link, but block off the vent port (un ribbed one) with a injector blank end, that would give me a adjustable restrictor.



The air switches are easy to come by from the AAZ and such, I was thinking of using the one that is used to open the wastegate. Old MKII polo's also have them, well, the Formel E's did in the line from the green vacuum reservoir. Think they wen't to the vac retard on the Dizzy. Anyway, by the by I have all the bits and some cool aircraft looking switches.



Thing is though, if it's just a restrictor all it will do is slow the air flow down won't it? if you are cruising at a constant manifold pressure won't the pressures on either side of the restriction eventually even out? leaving you with a stock system?

[jtanguay]

Well there are a few factors that will limit the amount of boost to reach the LDA.   The restrictor will eventually leak out enough pressure to equalize both ends.   For this to happen you would need full boost for at least 1-2 minutes.   The fact that the fuel would be limited would also decrease the actual boost by a small amount as well.

I would have to say that in a daily driver it would be useable, but for someone who has their foot to the floor 90% of the time, it would be better to have the bleed valve since eventually when the pressure would even out, it would probably take that much time to release the pressure.

I suppose you could get fancy and use a regulator, but $$$.

[fspGTD]

Depends on which turbo you are talking about.

If it's one with a poppet type wastegate, the wastegate should be designed to draw some air from the boost pressure diaphgram chamber by the valve stem/guide somehow, to help cool down the wastegate.  So simply adding a restriction in the wastegate pressure hose will cause a pressure drop and raise the boost pressure.  The 1.6lTD KKK for example has the boost pressure chamber on the diaphgram side where the wastegate valve stem is, so some of the pressurized air flows right into the valve guide around the stem.  Cooling air for the the 1.6lTD Garrett wastegate flows through a much more convoluted path, traveling through a portion of the wastegate valve stem that is cross drilled.

However, if the turbo has a "swing valve" style wastegate, like the 1.9lTD KKK K03 turbo, I don't believe any airflow will be drawn away from the wastegate diaphgram pressure chamber.

[fspGTD]

Oh right, the LDA!  You are absolutely right.  (Guess I need to pay better attention.  :wink: )