TB bypass mod

IggDawg · Post by **IggDawg** » Mon Dec 30, 2002 2:45 pm

Anyone here try this? There isn't much mention of this back on i-club, since all of them are intercooled. But teh way I see it, the compresser spikes the temps pretty high, but then the throttle plate being 190-ish degrees spikes it even higher. Would it be beneficial to bypass the TB coolant line, or is the air already hot enough to make this worthless.

The only detrement to such a thing, at least in NA cars, is that the throttle plate can freeze up under extreme cold. But with the air charge already being so hot I don't see the need for this, even in sub-zero temperatures.

Post by **Legacy777** » Mon Dec 30, 2002 3:35 pm

I've done the Bypass mod on my 90 n/a Legacy. I think it did help with the responsiveness of the throttle.

I'm in Houston, so I don't have to worry about icing up any time soon.

Post by **DLC** » Tue Dec 31, 2002 9:31 pm

I think that on a turbo car, only in the worst case circumstances could the TB get iced up. The nice thing about a mod like this one is that it should be easy enough to make it reversible very quickly.

When i regain interest in the car, and when it stops snowing, maybe i'll do it.

Dave

totech · Post by **totech** » Tue Dec 31, 2002 9:58 pm

Dave,

I so agree....

When i regain interest in the car, and when it stops snowing, maybe i'll do it.

Although I managed to swap out my rear struts, in my driveway today.

Fronts tomorrow....

Funny how little emergencies change our priorities..... Car had become dangerous, so loose, original struts on a 91, 200K miles.
I picked up the car in September, and hoped it could wait till spring.//

entirelyturbo · Post by **entirelyturbo** » Sun Jan 05, 2003 12:12 am

200k on factory struts? Had you ever been down a brick road?

Mine were shot after 100k!! And, yes, I know all too well how our plans are changed...

scoobiedoo22 · Post by **scoobiedoo22** » Sun Jan 05, 2003 8:17 am

Did this too, you have one line running from the tubing going to the interior heater core(on the right side of the engine when looking at it with the hood up), this line goes to the TB and out the other side to the IAC Valve out the side and back to the coolant "passage" under the intake(on the left side under the intake), it is a little trickey getting the new rerouted line on and clamped but I did this when I had the engine yanked so access was easy, other than that just follow the lines.

entirelyturbo · Post by **entirelyturbo** » Sun Jan 05, 2003 7:19 pm

Okay, somebody explain to the stupid guy what's going on here

... Are you rerouting the coolant away from the TB?

IggDawg · Post by **IggDawg** » Mon Jan 06, 2003 1:58 am

Yup. there's a coolant line going through the IAC and the throttle body on the way to the heater core. It heats up the throttle body and throttle plate to 190-ish degrees, heating up intake air significantly. mustang owners have dyno'd the mod at 6-7 hp at the wheels. the throttle plate acts as a tiny radiator. can't block the coolant line since the IAC needs to be at engine temp to idle the engine correctly. so the best way to do this is to disconnect bth TB coolant lines from the TB and couple them with a brass home depot hose coupling fitting. this'll let the air charge temps be much cooler, and every 10 degrees works out to be about 1hp. so yeah.

vypa · Post by **vypa** » Mon Jan 06, 2003 2:13 am

im in charlotte nc so the winter is pretty mild... think id be safe doin it?

entirelyturbo · Post by **entirelyturbo** » Mon Jan 06, 2003 2:29 am

vypa wrote:im in charlotte nc so the winter is pretty mild... think id be safe doin it?

I'd say so, it'd take a real chill to freeze the TB...

I'm in FL, so this will probably only do me good...

So I presume there's an in and out coolant line for the TB, just like the IAC? How about just taking a longer coolant hose and routing it straight to the IAC, bypassing the TB? That can be easily undone if necessary...

If this is such a HP gain, then why did it come like this from the factory? To avoid freezing the TB, I guess, right?

Post by **Legacy777** » Mon Jan 06, 2003 3:33 pm

Yup.....under certain circumstances the TB could ice up, and that would be bad.

IggDawg · Post by **IggDawg** » Mon Jan 06, 2003 3:33 pm

subyluvr2212 wrote:
So I presume there's an in and out coolant line for the TB, just like the IAC? How about just taking a longer coolant hose and routing it straight to the IAC, bypassing the TB? That can be easily undone if necessary...

that's basically what unplugging the 2 lines and coupling them does. so yeah. that'd work nicely. in any event, be sure to cap off the metal lines from the TB so they don't corrode inside.

subyluvr2212 wrote:
If this is such a HP gain, then why did it come like this from the factory? To avoid freezing the TB, I guess, right?

homogenaity. they don't want to sell different cars to different regions of the US. they'd also have to say "you can't drive anywhere cold" and stuff like that. sales nightmare.

mTk · Post by **mTk** » Wed May 21, 2003 5:28 am

Just did this tonight, +/- 30 mins, i had everything i needed laying around so i thought i'd give it a shot.

It was incredibly easy to do, and i can definitely feel a difference in the temp of the TB, it is MUCH cooler.

MK

Aaron's ej22t · Post by **Aaron's ej22t** » Thu May 22, 2003 2:26 pm

what all is needed and could you post a pic?

legacy92ej22t · Post by **legacy92ej22t** » Thu May 22, 2003 11:36 pm

i live in central P.A. it gets kinda cold here but almost always stays above 0 F.do you think i could get away with it year round or is it more a summer mod?

mTk · Post by **mTk** » Fri May 23, 2003 2:56 am

All you need is a bit of hose and some hose clamps. I am not sure what the exact size of the hose. The digicam i have blowz, but i'll try

I think you will be fine all year round. The only way to find out is to do the mod and see if anything bad happens

MK

mTk · Post by **mTk** » Fri May 23, 2003 3:28 am

Best i can do for now:

See the prongs on either side of the bottom? Coolant flows through those, remove the hoses that go to them and join the hoses together.

MK

Post by **Legacy777** » Fri May 23, 2003 4:02 am

here's some more pics of the lines and the fitting.

http://www.main.experiencetherave.com:8 ... ypass1.jpg
http://www.main.experiencetherave.com:8 ... ypass2.jpg
http://www.main.experiencetherave.com:8 ... ypass3.jpg

subiecar · Post by **subiecar** » Mon May 26, 2003 8:42 am

This is a great idea for an NA car, but if you have a turbo with both oil and water cooling fittings, it`s better to run the coolant thru the turbo from these lines (I`ve done it on mine.) BUT, if there`s a way to cool the water down below engine temps, I`d be all ears. Any ideas??--Rod

vrg3 · Post by **vrg3** » Mon May 26, 2003 12:14 pm

subie_do, are you talking about aftermarket turbos? The stock turbos are already watercooled.

If you really wanted to cool the water before sending it anywhere you would essentially just need to run it through a heat exchanger or radiator. Seems kind of self-defeating, though, since the car's cooling system is meant to regulate temperature at around 200 degrees Farenheit.

Brat4by4 · Post by **Brat4by4** » Thu May 29, 2003 5:09 am

I'm a genius!! Ok, here we go. Let's say someone is running an Air-Water Intercooler with a good-sized heat exchanger and a nice pump (like me

) This water is not going to be around 200 degrees all the time like the engine coolant... and if it does... it doesn't matter (more on that later). Plus using this water, you don't have to worry about freezing your throttle plate in the winter or anything cuz the water IS warm but not HOT. Hence it will warm up on cold mornings just like Subaru intended.

And since this is the water that is already cooling your intake charge... it is impossible for it to heat the TB to a point where it would warm the air!! This is the water from your INTERCOOLER, remember? So, if for instance your AWIC water gets above coolant temperatures... something is already wrong with your Intercooler or heat exchanger, and a TB that could be a little cooler if it was running coolant will be the least of your worries. Plus, the TB is not going to be able to cool that air down any where near the same effect as it being really hot and warming it up (before any bypass mod). I think I'll try to do this when i install my stuff. This seems the safest bet and it doesn't circumvent any saftey feature Subaru designed in AND will keep more things on the intake at the same temperature.

Post by **Legacy777** » Thu May 29, 2003 1:52 pm

Only issue with that is you're heating your water from the TB. By how much I don't know. But theoretically you could be increasing your intake charge temps by increasing the amount of heat going into the water.

Brat4by4 · Post by **Brat4by4** » Fri May 30, 2003 3:02 pm

That amount of heat would be miniscule compared to the heat the turbo throws out, in fact this water might cool down the TB, also, under full boost. Anyways, you want the heat IN the water rather than anywhere else. Man, this means the TB might be like a second very small intercooler. Plus the heat exchanger I have was designed to cool down a 1200 cc engine. I really can't see any downside to doing this... besides screwing with the head of any mechanic that tries to work on the car. "What the h&##..."

entirelyturbo · Post by **entirelyturbo** » Mon Jun 02, 2003 12:34 am

Well that sucks, I did it, started it up, and watched the coolant slowly stream from the coupling.

Forget it, I try to help the car out in this 90+ weather here in FL and it won't cooperate...

Post by **Legacy777** » Mon Jun 02, 2003 4:45 am

what type of coupling did you use & clamps?

You should use a barbed fitting. and the stock clamps are fine.

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