TB bypass mod

georryan · Post by **georryan** » Mon Jun 02, 2003 8:46 pm

so will this mod give about 6 hp to a turbo also?

-Ryan

Post by **Legacy777** » Tue Jun 03, 2003 12:29 am

Don't expect this to give you any hp. It's possible it could....but the main thing it does is improve throttle response.

georryan · Post by **georryan** » Tue Jun 03, 2003 7:51 am

ah ok, that makes more sense. I was going to say... hehe
How significant of a change is it though? Is it that noticable? Is it worth doing??

-Ryan

mTk · Post by **mTk** » Tue Jun 03, 2003 11:04 pm

georryan wrote:ah ok, that makes more sense. I was going to say... hehe
How significant of a change is it though? Is it that noticable? Is it worth doing??

-Ryan

Definitely worth doing, parts cost is sub $5, to me it's one of those simple do it because you can mods.

MK

Aaron's ej22t · Post by **Aaron's ej22t** » Tue Jun 03, 2003 11:15 pm

okay, guys. i am almost done with this mod, i just need to put the throttle body back on. curious though, couldn't you just run one whole new hose instead of connecting the two old ones with a coupler?

i used a 3/8in brass coupler and screw style hose clamps. i hope it does not leak.

entirelyturbo · Post by **entirelyturbo** » Wed Jun 04, 2003 3:16 am

I was thinking about doing the one-hose thing myself, but the hose that goes into the TB comes from way down near the block, with what I believe to be fuel lines interfering with it. So it's possible, but not necessarily any easier...

Aaron's ej22t · Post by **Aaron's ej22t** » Wed Jun 04, 2003 4:36 pm

also, is it okay to leave the two inlets on the throttle body uncapped ?
(where the hose use to connect)

entirelyturbo · Post by **entirelyturbo** » Wed Jun 04, 2003 5:13 pm

I think you're supposed to cap those off somehow or moisture will build up inside...

czo79 · Post by **czo79** » Thu Jun 05, 2003 6:09 pm

maybe those of us in cold climates could put splitters on each end of the coolant hoses, and put valves on so we can turn on and off the TB cooland bypass. I think I might want this in the winter....although is the purpose of it to warm the charge temp quicker? or is it to prevent the throttle from freezing up in winter? Can it even do this? I guess that could suck... Has anyone whose had their TB off recently, or even just intake, tell us if they noticed their throttle plate being out of alignment, so it would go over 90 and end up being a restriction at full throttle? I remember someone mentioning this and meaning to check it out, but havn't yet.
Thanks
Micum

Mark Ward · Post by **Mark Ward** » Fri Jun 06, 2003 12:48 am

Funny..
My old Datsun with Mikuni Side drafts only every froze on me once...
How can this happen on the Subaru?
What freezes?

Oh.. I live in Canada, where it only warms up for 2 months -JK..

Mark

Post by **Legacy777** » Sat Jun 07, 2003 3:58 am

The TB is an orifice, variable one at that.

When you pass gas/moisture through an orifice, you will have a pressure drop, and also a temp drop. When you have that pressure drop, moisture can precipate out of solution with the air, and when it's cold enough, and humidity conditions are just right, you could conceivably get ice build up on the TB/throttle plate.

entirelyturbo · Post by **entirelyturbo** » Sun Jun 22, 2003 8:24 pm

Okay, it's been done successfully this time.

The coupling consisted of a male/male piece, one end went into the hose, other into the other piece. The other piece was a male/female piece, one end of course going into the other hose, and the other end going into the other piece. There's probably a more concise way to describe that, but anyway, the two pieces weren't tight enough together, that's why it was leaking. And I used the plugs off of a new Purolator fuel filter to plug the coolant lines on the TB.

So I tightened it and put some RTV sealant on the threads. And I used screw-tight hose clamps instead of the standard ones.

So now that it's been done correctly, allow me to say I didn't feel much difference. I think it may have idled a little smoother, and there was definitely a little extra throttle response. As cheap as it was, I guess it was worth it. I'll give it a few days to evaluate it though...

Mr.Pessimist · Post by **Mr.Pessimist** » Thu Mar 18, 2004 8:57 am

Well, I just got done doing this mod. I've been thinking about it for a while and finally got some time...now that finals are over.
I havent taken the car out for a run yet, but it started up fine with no leaks.
Good call on the capping off of the TB passage, I would have never thought of that.
This mod took me a couple of hours. Given I didnt have real good tools to work with and I was bridging the entire gap with a metal tube, not an intermediate hose with two male couplers(which I would now probebly recommend). I used screw tightened hose clamps as well. Here's the real kicker on why it took me so long...I didnt remove the TB. Yes, yes...I actually worked around the TB and all the other wires and stuff. My, can we say frustrating? There is really NO room to work with under the TB, but I also might have saved time not having to put the TB back on.

Also, I used copper tubing for the bypass, anyone see any problems with that? any reactions with the coolant?

vrg3 · Post by **vrg3** » Thu Mar 18, 2004 1:42 pm

Heh, that must have been a pain working under there.

The copper tubing should be fine. The outside will eventually oxidize all the way, turning green. The oxidation will actually protect the rest of the pipe. As for the inside, I don't think copper will hurt the cooling system; at least some radiators are made of copper.

THAWA · Post by **THAWA** » Thu Mar 18, 2004 4:14 pm

This sounds hottt, anyone know what size tube it is that runs there? about how long in length too

anyone know for sure what size fittings should go in the tb holes?

vrg3 · Post by **vrg3** » Thu Mar 18, 2004 4:27 pm

The stock coolant hoses are 7.5mm, so 5/16" ought to fit pretty well. If you go to the hardware store the smallest length of copper tubing you can usually buy is a foot, which ought to be more than enough.

THAWA · Post by **THAWA** » Thu Mar 18, 2004 4:30 pm

I was thinking of just getting enough hose to cap it freom both ends, then cap it off at the tb. is that 7.5 id or od?

vrg3 · Post by **vrg3** » Thu Mar 18, 2004 4:45 pm

Ah, yeah. One piece of hose replaces the throttle body and the two hoses that connect to it. These hoses are all 7.5mm inner diameter.

entirelyturbo · Post by **entirelyturbo** » Thu Mar 18, 2004 5:48 pm

I didn't take my TB off either, and I think I did it in about 45 mins...

I used a brass fitting, I think. I didn't think about using brass in a cooling system completely made of aluminum until now, but I haven't had one single problem, so I'm not worried about it.

Mr.Pessimist · Post by **Mr.Pessimist** » Thu Mar 18, 2004 6:18 pm

What? Do you think your better than me?

Yeah, like I said before, I wouldnt recommend the single piece of tubing because that's where I had the most trouble. It was also a piece of scrap laying around the garage so I didnt really know its OD off hand and it fit REAL snug, almost too snug, so I had to use some lube to get the tubing in the hose. All of this work tryin the get the hoses and tubing to mate up while hunched over the engin bay trying to work around the TB.

You guys probebly used a barbed and tapered fiting right? That seems like it'd be the easiest way to go.

Yeah, tapered would really be nice now that I think about it. I was trying to fit the OD of the tubing into the max ID of the hoses.

THAWA · Post by **THAWA** » Fri Mar 19, 2004 2:35 am

Well I think I'm going to try and just get one long 7.5id tube and run it from the iac to whereever it supposed to go after the tb. Then take the tube from the tb to whever that's supposed to go and connect it to the other side, in a sense making a circuit for the tb itself.

entirelyturbo · Post by **entirelyturbo** » Fri Mar 19, 2004 3:25 pm

I'm kinda confused by what you said. Understand that when this mod is done, you should have NO coolant hoses attached to the TB whatsoever.

The coolant flows from the pipe off the top of the block on the driver's side, to the TB, then to the IAC valve. You can connect the two hoses that are already attached to the TB, or you can remove them and put a hose straight from the pipe off the top of the block to the IAC valve.

THAWA · Post by **THAWA** » Fri Mar 19, 2004 3:28 pm

yeah, im saying tht im going to put a tube from the block to the iac straight

then im going to take the tube that was going from the block to the tb and put that on both ends of the tb, assumming its long enough, so that is closes the tb lines

vrg3 · Post by **vrg3** » Sat Mar 20, 2004 4:08 am

Nitpick: subyluvr2212, the coolant actually flows in the other direction: through the IAC valve first, then through the throttle body.

I just thought of something -- when you do this mod, is it important to clean out the coolant passages in the throttle body and let them dry out before you cap them off? It seems to me that if you leave stagnant moisture in there it could corrode.

ciper · Post by **ciper** » Sat Mar 20, 2004 4:19 am

I feel the opposite.

The throttle body should NOT be capped. Let the air circulate and clear out. I mean its copper and aluminum, how often is the outside of your engine rusting?!

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TB bypass mod