Getting Waste gate signal off throttle body? Dangerous?

[spence88mph]

Hi guys,

in the final stages of my turbo conversion, all that's left is the oil lines off the thottle body and the waste gate signal.

I've found a place I can connect the wastegate signal off on the throttle body, it's the line that went to the oil tank and the tube flits, it's just after the butterfly. Is it too late to get the signal there, do I need to tap a nipple into the charge pipe or afm? Or doesn't it make a difference?

No I dont have an intercooler, doing the stage one protomotive kit with only .5bar.

Cheers!

Spencer

[jbrinkley]

yes it's too late, if that's what you mean, needs to be before the plate
here's some tial stuff
http://www.tialmedia.com/documents/w3_tial_wginstall.pdf

[fredmeister]

Why does it need to be before the throttle plate? Is there a scientific reason? Not trying to be sarcastic, but thinking this thru from an enigneering standpoint.
I think after the throttle plate is better because it measures actual pressure in the intake manifold more precisely since it is after the throttle plate pressure drop. I have been running mine off the intake manifold without issues, (at least that I know of).

[jbrinkley]

what would negative pressure do to the WG?
honestly I don't know, it's just what tial says

[A930Rocket]

Mines located after the plate.

[930gt-40r]

mines is going after the plate, they hit harder that way.

[spence88mph]

Once the thottle is closed the wastegate wouldn't get the signal then but I spose that doesn't make much difference? The pressure would be built up through the whole section and shouldn't vary at any point through the charge part you would think. I dont know though, I'm green to all this.

But to give you a sneak peak, still haven't had first start, GT30R, Tial 46mm, V-Band RarelyL8 passenger exit:

[hobieboy]

Originally Posted by spence88mph

Once the thottle is closed the wastegate wouldn't get the signal then but I spose that doesn't make much difference? The pressure would be built up through the whole section and shouldn't vary at any point through the charge part you would think. I dont know though, I'm green to all this.

That's why there is a BOV to take care of throttle plate closing, i.e. vacuum, situation to prevent back pressure to the turbo. WG is to vent excess boost when you are on it.

Mine is after the plate as well FWIW.

[fredmeister]

So we have a consensus.....it seems better to tap in affter the throttle if yu want to gain that last ounce of extra boost because you are after the throttle plate pressure loss, thus allowing it to boost a little more thru the wastegate. Porsche tapped into the intercooler for some reason, but this was probably for a little extra safety because of the reasons above.
I have a lead in question, how much better is a tial at controlling boost over the stock WG?

[beepbeep]

Originally Posted by hobieboy

That's why there is a BOV to take care of throttle plate closing, i.e. vacuum, situation to prevent back pressure to the turbo. WG is to vent excess boost when you are on it.

Mine is after the plate as well FWIW.

BOV won't do anything to prevent vacuum in plenum chamber after the throttle. BOV is installed before throttle.


I personally wouldn't install WG signal after the throttle as it may induce peculiar surging behavior at certain throttle openings on some engines. It will also subject membrane to both boost and vacuum which might and might not shorten it's life, as WG membranes are only ment to be subjected to boost. YMMV.

[rsrmike]

Originally Posted by beepbeep

BOV won't do anything to prevent vacuum in plenum chamber after the throttle. BOV is installed before throttle.


I personally wouldn't install WG signal after the throttle as it may induce peculiar surging behavior at certain throttle openings on some engines. It will also subject membrane to both boost and vacuum which might and might not shorten it's life, as WG membranes are only ment to be subjected to boost. YMMV.

+1 Makes the most sense of all.

this sort of relates to the debate over where to tap the boost gauge signal...

Some of you guys may have noticed your elec. gauge read .8 or 1.0 bar at 1/4 throttle and relatively low RPM's.

It seems to me you would want the wastegate to open under these circumstances to keep the turbo from sucking more air past the airflow meter and possibly causing AFR issues, granted that would mostly affect a CIS car i think.

Another thing I've noticed when the signal is above the throttle plate is that upon closing the throttle, whatever air surge isn't relieved by the BOV tends to keep the wastegate open longer. A sudden vacuum would most likely cause the valve to slam shut and create a pressure spike on the hot side as the cold side is dealing with pressure spikes on it own from a closed throttle and a spinning turbine wheel. Seems like that may give the thrust bearing some added stress... I dunno certainly no turbo expert here...

I would love to know, on average, how much pressure loss is there really through the throttle body at WOT? Is it really that different? I know it depends on many variables but say an average 930 w/ k27??? Anyone know?

Thanks

[rsrmike]

I might add the best location is the one most conspicuous where there is less chance for a "uh-oh"...

[930gt-40r]

Originally Posted by fredmeister

I have a lead in question, how much better is a tial at controlling boost over the stock WG?

The Tial 46mm gate will control pressure better than stock because it flows more. In addition to that, the Tial is constructed of cast stainless and has better reliability than stock. I would buy mine again if I had to. I have never seen a Tial stuck on a Porsche.

[fredmeister]

BOV won't do anything to prevent vacuum in plenum chamber after the throttle. BOV is installed before throttle.


I personally wouldn't install WG signal after the throttle as it may induce peculiar surging behavior at certain throttle openings on some engines. It will also subject membrane to both boost and vacuum which might and might not shorten it's life, as WG membranes are only ment to be subjected to boost. YMMV
==========================================

As BeepBeep says....this sounds like a good reason not to tap into the intake manifold. I may change back to the intercooler location based upon this advice.
Though I think the intercooler sees some vacuum ahead of the thottle otherwise you would not see flow thru the CIS metering plate during closed throttle conditions, though it may be a small amount of vacuum....tell me if I am wrong.
This is why I like the forums,,,,,gets you thinking and learning something new everyday.

[dewolf]

Originally Posted by spence88mph

Once the thottle is closed the wastegate wouldn't get the signal then but I spose that doesn't make much difference? The pressure would be built up through the whole section and shouldn't vary at any point through the charge part you would think. I dont know though, I'm green to all this.

But to give you a sneak peak, still haven't had first start, GT30R, Tial 46mm, V-Band RarelyL8 passenger exit:

Hey Spence, looking good mate. You are gunna love it. Get an IC on it under the lid without the tail. BTW, I sold my 930 to Greg Steer of West Racing Cars. I'm on the hunt for GT3CS now.

[spence88mph]

Hey Scott, yeah I realised you sold it afterwards, I wish you had of told me I probably would have bought it. I think a mint 930 is going to go up in value over the next few years they're a bargain now. Anyway, I drove it last night for the first time, was so awesome!!!

I do need to get an IC now but getting something under the lid wont be easy, I might just put the tail on, just love the sleeper factor right now. I'm runinng 5psi and it feels about twice as fast as it used to be, pulls away cleanly in any gear, loving it! Good luck with the GT3CS, great cars!

[jbrinkley]

pretty cool huh Spence? I remember my first drive

[dewolf]

Can you fit a couple of small IC's in the wheel wells maybe?

[les_garten]

There are two good reasons to plumb in the wastegate control line before the TB.

1) That's where Porsche put it
2) That's where TIAL put's it.

Think how many Rice Burner's are out there running it that way right now?

These are the reason's why i put mine there. I also called TIAL at the time and they told me to plumb it in before the TB. Unfortunately with all the details of an EFI conversion, I don't remember why. A simple thing would be to call them and ask, rather than guess.

I may call them and repost if I remember, cause I'm now curious also.

[930gt-40r]

Les- I have plumbed it after the waste gate before with fine results, but maybe it is better before the TB.