bypassing tb coolant line

***BLUEMEANIE*** · 02-25-2005, 09:22 AM

I got into a disscussion with someone last night about silly little diy mods and the topic of bypassing the throttle body coolant line came up ... Other than not warming the tb and I suppose keeping the flow of air cooler, is there any real worthwhile gain from doing this?
Its not something I ever really thought about as an effective mod...

tia.

Pineapple · 02-25-2005, 09:53 AM

Yea its been done but don't know if its worh it at all. Need to measure TB temp before and after the mod to see. Point is the whole manifold is alum and got heat from engine already, a cooler TB won't help much I think. Question is why Toyota run coolant there in the begining? Cool down the ICV cause it runs hot?

***BLUEMEANIE*** · 02-25-2005, 12:04 PM

That was my stance on the topic too...

CrawlingEye · 02-25-2005, 12:32 PM

The TB coolant line actually heats the intake manifold more than it cools it. I have this mod in place with my car, and the car takes a bit longer to actually 'warm up' due to the fact that there's a shorter distance between the radiator and the engine itself.

The best argument I've heard against doing this mod is that it may hurt fuel atomization. The reality to that is, it may hurt it a bit on a cold day at start-up.

As far as gains go? IMO, every bit counts. I've noticed that in the summer I can now put my hand on my CAI (and intake manifold) and it'll still feel cool, where-as before, it would be quite hot by the intake manifold.

I've noticed a bit more pull (I know it's not good, but to test this, drive your car a bit before it really warms up. keep in mind, your tranny won't down-shift, but I'm sure you're noticing a minor increase in performance while it's cold). This is just to replicate the same pull when the car is fully heated up. It works well at that, but it's by no means a godsend of mods.

I'm looking to try a couple of the other 'free' mods, like advancing timing and increasing spark plug gap to see how noticable collectively everything is.
I wouldn't look for huge gains out of any of these, but for the price (nothing), you've got nothing to lose.

For any of the 5S-FE guys looking to do this, on page 4 of my Cardomain site, you can see how I did this. I simply removed the one hose from the TB and just plugged the other right in to where it came from. Some people use a barb and just clamp to that. Either way, it's an easily changable mod, if you don't like it.

For anyone not wanting to read all of the above, the short story is:
Pros: Minorly better pull after car has fully warmed up (and it's free)
Cons: Takes a tiny bit longer for the car to fully warm up on a cold day.

Give it a whirl, see what you think.

Toysrme · 02-25-2005, 02:17 PM

I used a 1/8" thick piece of aircraft plywood (from an r/c kit) and made an upper intake manifold spacer and bypassed my coolant a long time ago.

Car warms up the same distance driving it (1 1/2 - 2 miles) and the manifold is barely warm to the touch after an hour of running.

blownrx7 · 02-26-2005, 12:42 PM

i did this on my rx7, and yea it takes a little longer to cold start

Tofuball · 03-01-2005, 04:52 PM

That line doesnt "warm up" the TB on an RX-7, what it does is cause the thermowax to retract.

The thermowax controlls your cold idle speed.

powderblue91 · 03-10-2005, 10:46 AM

Quote:

Originally Posted by blownrx7

i did this on my rx7, and yea it takes a little longer to cold start

I bet your idle doesnt go below 1500

JetspeedCamry · 03-10-2005, 02:56 PM

Quote:

Originally Posted by CrawlingEye

I simply removed the one hose from the TB and just plugged the other right in to where it came from. Some people use a barb and just clamp to that. Either way, it's an easily changable mod, if you don't like it.

Can you explain this a little better? Im not quite sure what you mean by "plugged the other right where it came from".Your Cardomain pic (on Page 2) doesnt show much at all.
Id like to try this on my 2VZ.

Thanks.

CrawlingEye · 03-10-2005, 04:51 PM

My CD page shows everything that was done. If you look in the back (the thing that isn't blurred, kind of diffcult to see, but you can), you'll see where I clamped the line to.

Pretty much, you have 3 lines coming from your throttle body:
Coolant send, coolant return and your cold-start injector.

If you know your engine, you'll know which is which (check your haynes/chiltons/whatever). The way it's laid out in my car is that the injector's the center, the left and right are coolant lines.

You simply get some rags or paper towels out and put 'em down so you don't make a huge mess, remove the clamps from the TB and just either bar them together and clamp the lines to that or just remove one of them (I removed the front one, since it seemed the easiest to replace) and clamped the rear one to where the front goes. Which is just a bypass for the coolant.

I hope that helps.

88 LE · 03-11-2005, 09:07 AM

The easiest way to do it, is disconnect the 2 coolant lines from the bottom of the throttle body (its actually the IAC).

Then connect the 2 lines together with a brass barbed fitting and hose clamps.

http://www.plumbingsupply.com/barb.html

I would plug the 2 nipples left over on the IAC with vacuum hose caps and hose clamps.

P.S. The hose in the middle is for the IAC. Its not for the cold start injector. Besides the cold start injector is on the intake manifold and has a line running off the fuel rail.

JetspeedCamry · 03-14-2005, 04:09 PM

^Much better thanks.

dna59 · 03-14-2005, 07:37 PM

I too was wondering if this mod had any real worthwhile effects. I guess it won't hurt trying it.

CrawlingEye · 03-14-2005, 07:52 PM

Quote:

Originally Posted by dna59

I too was wondering if this mod had any real worthwhile effects. I guess it won't hurt trying it.

The gains are minimal, but it's a free mod (if you do it the way I did) or cheap mod if you do it 88LE's way. Either way you slice it, you've got nothing to lose and can reverse it at the expense of a little spilled coolant and about 10 minutes.

TcmaBoy · 03-15-2005, 01:54 PM

The reason for running coolant through the intake mainifold is to help with emmisions. The way emmisions tests are done is they take the car on a 15 min drive starting with a cold engine. Most emissions occour in the first few minutes of driving when the engine is cold. The coolant warms the manifold and helps with fuel atomization when the engine is cold reducing the need for warm up fuel enrichment. Kind of the same idea as running an EGR system, only with out diluting the intake charge with exaust gases. blocking off the coolant lines won't hurt, and when the engine is warm will give a slightly cooler intake charge. The only concern is in the winter. If you live in the north where it is cold then I would hook them back up in the winter. If the manifold is too cold then you will have problems with atomization.