Hi, has anyone ever connected the two coolant pipes that go throught the throttle body together? I hear it can lower intake temps.Or is this just a myth?

Mit

 

I'm sure it does lower temps, by an absolute minute amount, and then means that your idle control spring in the bottom of the valve no longer has its own adjustment facility for cold starts and has to be completely controlled from the ECU instead.

 

Not worth the hastle then,cheers.

Mit

 

Wrong.

I chose to base my mods on facts gained from what I have done - I have done this on mine and have measured the effect before and after using charge temp (not intake) gauge. The difference is substantial enough to warrant the 10 minutes it takes circa 2C less in normal driving. The biggest difference is in a closed throttle situation where the air is flowing more slower through the throttle body (such as idle or when decelerating into corners) - This was around 20C less with the coolant re-route and you can stay stationary with the car and it will hardly rise (even with a TMIC)

With the coolant feed there, you are heating a big glob of air that is ingested into the engine in one big det causing gulp when you reapply the throttle.

 

Interesting. I'm always one for facts and will happily admit I've not tested out this mod myself, although I do know a lot of Imprezas are plagued with cold start problems. Whereabouts have you been measuring your charge temps and how have you isolated the coolant feed effect from the other significant heat sources (IMHO much more capable of effecting in-cylinder temperatures than a water feed through the throttle body)?

Although I don't doubt that it does make a small difference - every little helps - I don't believe that the effect of this pipe is significant in the overall heat management of the engine bay. A better intercooler, a front mount, manifold spacers and header tank insulators, wrapping the exhaust system to past the cat etc etc. These are all much more effective than worrying about the TB, again IMHO.

Let's say the worst happens and the coolant flow through the bottom of the TB heats it to the same temp as the coolant. Look at the overall inlet tract - a filter that may/may not be drawing in warmed engine bay air, an inlet pipe sandwiched between manifold and heads, a turbo which is basically a vey hot air pump, intercooler and pipework which can pick up as much heat as they get rid of once you're slow or at standstill, an inlet manifold directly attached with no insulation to a hot pair of heads and sitting a few inches over the block, a header tank directly attached with no insulation to manifold runners 3 and 4...

I just can't see how the TB coolant bypass will make that much genuine difference and if it does, what is the downside of that? I would very much like to look into this issue and if you have some data I'd really like to chew it over. If it works, I'll do it too, if the difference is negligeable I'll leave it.

 

You are entitled to your opinion but mine is based on actual facts on measuring the temperature of the air in the throttle body immediately before it enters the engine bay (ie after Turbo, IC and all other heat sources).

Worthwhile mod in my opinion and one that is present on most highly modified subaru's that I know of.

 

I'm not disputing what you've found at all :-) goodness knows I've done enough testing of my own that turns received forum wisdom and pub talk on its head. But I do wonder if your frankly amazing 20C charge temp drop on a closed throttle is due to a 'bubble' of hot air being heated up at the TB when it's got nowhere else to go and airflow is not going to reverse back into the IC pipework. Although this 'bubble' might get say 20C hotter than if you didn't have the coolant flowing through, once you open the throttle and that little hot bubble of air goes into the plenum and gets dispersed to four cylinders, will it make that much of a difference?

I'd be very interested to see the charge temp measured actually within the plenum, and then see whether the extra heat you've seen at the TB actually comes out 20C colder in the manifold where it counts, or if it is just diluted. I understand the problem - I've never been happy with my charge temp sensor in the FMIC pipework just before the TB joint as I know it's telling me what charge temps are like upstream of the manifold but not within it, which is more important.

 

I have no idea how effective this mod is but i have done it on mine and haven't had any problems with the car ref cold starting Bob Rawle did it on his old newage STi about 3 years ago which now belongs to a friend of mine and he's had no problems as well, as they say every little bit helps

 

To save me looking up the procedure.. iirc it's just a question of connecting hose in and hose out of TB.

However, is there enough length for them to reach each other without having to extend and what about bunging off the TB inlets..?

I'm all for gaining every muckle..

 

I saw this kit for sale on ebay in the states,selling for $25 for a piece of pipe and a clamp! Easy way to make cash i spose.

 

OK well I'm convinced. I stand corrected and will give it a go once my engine's rebuilt, eventually! If it simply a throttle body 'de-icer' then it should be OK as we get into spring.

 

I went one stage further with it, I now have a small plastic tank in the boot with coolant, it flows with boost and waterspray working. More of a cooling effect for the manifold - I dont really need it now though with water injection but as they say "every little helps".

 

I bypassed mine when I last had the IC off, I used an old piece of pipe from a manual choke conversion kit...

It will certianly have no effect with an electronically controlled ISCV on the idle control, it's there for throttle icing, which we are unlikely to get after the air has been heated through the turbo!

Simon

 

Simon,

did you bung the TB after the bypass..? If so, was it something like a piece of hose with a correct size bolt in it..?

 

Don't know about Simon but that's exactly what i did