Throttle body coolant bypass
 

Just about to strip my engine and while doing so will be doing this mod. I would like to know if this requires a pipe to bridge it or can I just block off the hoses from the engine?

Cheers,

Wayne.

You can block the hoses which lead from the water cross pipe on the block to the ICV and TB.

Just for info. why is this mod done?

There is no need to block the pipes, on my MY97 i bypassed the throttle body using the pipe from the iscv and connected it straight to the return if that makes sense.

:wonder: :wonder:

Blocking of at the cross pipe just makes a nicer finish with less water hose to see.

The reason its there is to stop icing of the throttle body in freezing conditions, the compromise is a warm throttle body passing on its heat to the air you've just tried to cool via the IC.

So for a slightly cooler charge the coolant pipes are bypassed (or blocked off).

now the compromise is the chance of a stuck throttle when, say coming off the motorway after a long drive in arctic conditions.

V. rare but it did happen to JGM a few years back

If you dont flow the coolant through the icv wont you get idle problems?

Not at all as its sole purpose is to keep the throttle body warm, it serves no other purpose.

I had this done to my car 8 months ago and even with the temp in minus figures had no issues with a sticking frozen throttle :)

Banny

I just don't like the idea of the hose being there i it isn't doing anything. Thanks for the replies!

Throttle body icing isn't really down to outside temps being freezing; it has to be cold but not freezing; its down to humidity and the venturi effect.

Granted its rare as you'd have to be operating with the thottle opened more than quarter of the way (which is about half travel at the pedal), but less than full throttle for a sustained period of time to get enough flow and cooling effect during cool humid ambient conditions to get any ice formation.

So the chances of it happening are rare. But it was put there just incase.

alright Wayne,

Did this on my old 99 uk and have done it now on my 98 wrx, no problems even at this temp and just bridged the gap by disconnecting on of the pipes to the throttle body and reattaching to one of the pipes (can't remember which one).

Here is a guide I originally posted on sheffieldscoobys.co.uk for the MY99 uk:

I read on Scoobynet that the Throttle body is surrounded in coolant to stop it iceing up in winter.

But in summer it acts as a heater around the throttle body and if you disconnect the pipes you get cooler inlet temps....see post number 13 here https://www.scoobynet.com/general-te...ncy-graph.html

So I thought I would do it and document the process on a MY99 UK Turbo.

Here goes, apologies for the rubbish photoshop efforts.

1, Remove the intercooler by loosening the clips/pipes highlited in green and the two bolts eitherside of the intercooler (only on has been marked) Then tip the intercooler towards you to remove, place on even ground and try to not damage/touch any fins.

https://img218.imageshack.us/img218/...ides003ex8.jpg
By damocell, shot with Canon PowerShot A80 at 2007-08-04

2, the two pipes in question are highlighted below in green, the blue arrow shows where the end of one pipe is going to go to the other end of the other pipe.

https://img218.imageshack.us/img218/...ides004ul8.jpg
By damocell, shot with Canon PowerShot A80 at 2007-08-04

3, Clamp the left hand pipe in the above picture using a brake pipe clamp to stop coolant loss and remove from the throttle body. then remove the end of the pipe marked with the blue arrow and connect the left hand pipe to where that pipe connected.

https://img218.imageshack.us/img218/...ides007ov3.jpg
By damocell, shot with Canon PowerShot A80 at 2007-08-04

The blue arrow shows where the pipe used to go.

Make sure the spring clips are on tight and refit the intercooler

Takes about 30 mins max

Hope that helps

Damo

^ Exactly what I did ^

thinkim going to do this mod as well

Did this mod too and drove back from Germany last week in -10C with no icing (with FMIC so no heat soak from a TMIC to protect it)

Has the added benefit of reducing the rate of climb of charge temp in closed throttle situations such as decelerating into corners or at standstill.

I've done it, no idea how much of a difference it makes, did it in conjunction with the inlet insulators, every little helps!

Have had this mod on mine for the last year or so with no probs at all. All helps to keep the charge cooler/denser. I think these sorts of mods are failry minor but when cumulatively done with other things like manifold spacers and coolant tank insulators etc, you're probably getting a good improvement. I recall Harvey doing loads of work on cooling/insulating years ago and made some interesting finds.

im going to this 2moz

A couple of the older posts about this say that its a great mod for a couple of quid.
Looks too me like it costs nothing, as you are looping the flow back in. Is that right, or do you need anything else?

Yep, that's right & I've just done it today - took about 5 mins. as I have a fmic & nothing needs to be removed!

I just took the 3 relevant hoses off (pipe to icv, icv to throttle, throttle to block) & just connected up one length of silicone hose from the pipe to block, hence bypassing the ICV & throttle body.

Looks tidier with less hosing everywhere as well.

Done this yesterday, car feels better :)

can this be done on pre 96 imprezas?

Certainly can

EXCELLENT that this thread was brought back up as i posted this yesterday lol:lol1:
https://www.scoobynet.com/general-te...ttle-body.html

Do the connectors on the throttle body where the pipes used to connect have to be blocked off,or can they just be left open as in the pic?

just leave them open.

Mit

ok bud cheers.;)

Thing is, even if the TB is very hot (coolant fully up to temp/hooning/summer, etc.) would the charge of air actually conduct the heat from the TB to any significant degree anyhow - seeing as the, transient, mass of air going past the TB at any point in time is very small?!

What I'm trying to say is, does it have actually have time to conduct significant heat from the TB, as it momentarily passes through it?!....

Just done this on my uk hawkeye, but it was a little diffrent,mine had a hose going into the bottom and then coming out of the top, i'v just linked the pipes.... Hope thats right

I done mine today,but rather than leave the throttle body with no pipes on ,I simply ran the loose pipe on the throttle body back to the other side of the throttle body to tidy things up.:thumb:,never took 15 mins.