DIY: Tb coolant bypass mod the easy way

[bigborian]

Hey all i wasn't able to post this in the Engine section i guess cause i'm a newbie haha.

Anyways i just finished doing this mod I did this mod a long time ago back when i drove an LS1 Camaro and figured i could do the same thing to my k20 civic.

First here is the picture of the 2 coolant lines that go to the throttle body they are under the intake pipe so you will have to remove that to get to it. (borrowed from the DIY: Tb coolant bypass thread)



Things you need to buy:

1/4 inch to 1/4 inch Universal coupler (you can get at Home Depot in the plumbing/piping section) Looks like this except without the 3/8" barbed side it looks like the long 1/4" side on both sides of the coupler. (picture borrowed from home depot website)



Some small hose clamps (the ones for small tubing, they sell them at home depot as well)

Some rubber caps I think they were called screw head caps, or screwdriver caps (also bought at home depot i got the green ones they are about 1/4" in diameter from the looks of it) *edit* They are called Screw protectors

(by request I updated this to make a step by step version for easy reading, pics/video will be uploaded soon stay tuned)


1.) Remove Intake pipe from Throttle body. You do this by taking a screw driver and loosening the hose clamp attached to the intake pipe on the throttle body, and on the filter box then just slide it right off. (loosen the red circled ones and unclip the yellow circled MAF sensor clip)


2.) Now notice the two lines in the picture above at the bottom of your throttle body, those are your coolant lines to the throttle body. The bottom one is coolant into the throttle body and the top one is the coolant return line to the main engine coolant line.


3.) Take some pliers and squeeze the stock hose clamps and slide them down the coolant lines so they are not clamping down the hose. (In this picture the guy had a screw on hose clamp but they will both look like the bottom hose clamp. They are the kind that you squeeze the two ends together and they loosen up kind of like a hair clamp for girls)


4.) Remove the bottom coolant line by pulling it off of the TB line. (this takes a little bit of force since the lines are so snugly secured onto the TB so don't be afraid to pull hard on it ^^) the bottom coolant line will leak coolant when you take it off so after u take it off direct the hose upward allowing gravity to hold down the coolant in the line and not get it all over your engine. (Also put a rag or something into your air intake pipe so that you don't get coolant in it but if you do just take a rag and clean out the coolant in your intake pipe you don't want that getting sucked into your engine)


5.) Take the top coolant line off that's connected to the TB. (Same warning as the bottom line it's hard to pull off so put some muscle into it, but try not to Yank it, it will slide off)


6.) Now that you have both coolant lines off Take the 1/4"-1/4" coupler and put one end through one of the coolant lines then put your new hose clamps on both lines. (I guess you could use the stock hose clamps too but I just like the feel of the hose clamps that you screw in they just feel more secure to me)


7.) Now put the other 1/4" coupler end into the other coolant line, now you have a coolant circuit!


8.) Move the hose clamps to where u can feel the coupler inside the coolant lines and place them over that area and tighten down. (Make sure it's nice a snug)


9.) Now take your screw protector caps and put them over the TB lines that you took the Coolant lines off of just to plug them up


10.) All done! Clean up and start her up and take it out for a test.

Thank you to Galaxygrey13 for letting me take pics of his car and letting me do this on his car since mine is in the shop.

(I've also left the original post just incase i missed anything)

You basically just take both lines out (careful once u take one of them out it will start leaking coolant out of it, so keep your air intake pipe clear of it or just shove a rag into the intake pipe like i did) The lower line is the coolant into the throttle body line and the upper line is the coolant return line back to the main coolant line to engine. I would suggest take the bottom one out first so you dont have to work with coolant spilling out on you while you take the other line out I made the mistake of taking out the top one first now my hands smell like coolant. Take the bottom line out and point the end up and coolant won't fall out of the tube.

Slide the hose clamps on each tube, but don't tighten down on them, this is just so you don't have to try to put them on once the coupler is in. Then take the coupler and shove it into both coolant tubes making a circuit and allowing the coolant to recirculate back to the engine.

Then move the hose clamps over where you feel the coupler inside the tubes, preferably close to the open end of each tube, and clamp it down nice and tight (this line is under pressure due to coolant running through it so make sure it's tight but not too tight)

Then you take the (screwdriver caps/ screw head caps) rubber caps and slide it over the open metal throttle body lines that you took the coolant lines off of. (mine fit perfectly, they were nice and snug only problem was that they were a neon green color which doesn't match but it's hidden anyways so no big deal)

Then that's it! I DID notice that the throttle body runs much cooler. Before this mod, after i drove around, i touch my throttle body it's hot to the touch about as hot as the intake manifold sometimes hotter. After I did this mod I went for a drive for about 30 mins and i pop the hood and touch the throttle body and it's nice and cool about room temp maybe a little cooler than that.

[JEA86]

much better way of doing this mod!

[bigborian]

whatcha guys think? ^^

[AXIS]

need more pics

[bigborian]

Originally Posted by AXIS

need more pics

Hmm alright then I'll try to post a few pics of the coupler going into the tubes and the little green caps on the throttle body lines

[AXIS]

i have a stock intake so i think this is why i'm having trouble with the pics that everyone is using

[bigborian]

Originally Posted by AXIS

i have a stock intake so i think this is why i'm having trouble with the pics that everyone is using

Stock intake is the same deal u have to take it off before u can do this mod the stock one comes with a hose clamp as well u just loosen that with a screw driver and slide it right off then u will see the throttle body the way it looks in the first pic. I thought my directions were descriptive enough but if not i'll take pics of the two lines being connected together with the coupler and the hose clamps on it. I'll also take pics of the little caps that go on the TB line.

[AXIS]

step by step please haha, yeah i'm lost

[oHsevenGG_Si]

Ax,

This method is pretty cake from the looks of it. Very smart actually rather than buying a new hose and routing you just buy the coupler, clamps & caps for the TB end of things. Prolly no more than $7. =] in fact I MAY have the 1/4 coupler laying around =D

[galaxygrey13]

Ill come by your house and you can do this to my car.

[AXIS]

yeah cuz theres something i'm missing i've already bought the 5/16 hose

[oHsevenGG_Si]

Originally Posted by AXIS

yeah cuz theres something i'm missing i've already bought the 5/16 hose

well for your situation.... all you do is remove the two existing coolant hoses that go to and from the TB. and make that one hose connect both ends where those two hoses were. and just cap off the TB.


what this dude is doing is instead of buying a new hose, he's just connecting the two existing hoses and making them as one as if you were to buy one separately.

[Zeuceone]

you can do it without buying anything. just loop he hoses.

[Mjrn.]

Not to be negative or anything, but I thought Cobb had said while tuning our cars that the bypass actually messed a lot with proper maf calibration and didn't seem to provide any benefits to the car. They recommended not doing it at all, and not just for safety reasons. I wanted to do this myself too but after I heard that I had to pass.

Good diy though!

[Zeuceone]

what was the reasoning in that?

this is after the maf so how could it change anything?

[oHsevenGG_Si]

Originally Posted by Mjrn.

Not to be negative or anything, but I thought Cobb had said while tuning our cars that the bypass actually messed a lot with proper maf calibration and didn't seem to provide any benefits to the car. They recommended not doing it at all, and not just for safety reasons. I wanted to do this myself too but after I heard that I had to pass.

Good diy though!

how could coolant going through a passage in the TB mess with MAF calib?
the only negative effect is that if you do the bypass and you live in a cold cold area your throttle plate could get frozen or stuck cause the hot coolant wouldnt be thawing or anything anymore. as least thats what ive read regarding this mod.

[Mjrn.]

let me see if I can find it...yeah I heard about the frozen thing too.

here we go:

Honda Civic Si AccessTUNER Tuning Guides, Worksheets, and Tuning FAQs. - COBB Forums

Cobb: "Removing the coolant lines to the throttle body is proving to be a "significant" modification as far as the ECU is concerned. Removing these coolant lines will likely allow for poorer fuel economy as another side effect. As will setting your fans to turn on at colder coolant temperatures. Combustion chambers are more effective at warmer temperatures and having coolant warm up your throttle body helps increase the intake air temperatures to a more efficient temperature for internal combustion. We are just stating this so you have an understanding that much of what Honda did was done correctly for a performance street vehicle. We are simply trying to do our best to explain what could be going on with your vehicle after a recent mechanical change."

[culasse]

This comment from Cobb only applies in winter. I wouldn`t worry about it in summer.

[bigborian]

Originally Posted by AXIS

step by step please haha, yeah i'm lost

Alright I have an aftermarket intake so i won't be able to show u how to take off a stock one but it should be the same type of deal.

My car's clutch went out yesterday and so it's in the shop atm till Wednesday on Thursday I'll take pictures of how to do the mod step by step. Maybe I'll make like a you tube video of it or something and post it here that might be better. All in all the mod took like 15-20 mins to do the only somewhat hard part was getting the coolant lines off the throttle body cause they are a tight fit everything else was cake.

[bigborian]

Originally Posted by Mjrn.

let me see if I can find it...yeah I heard about the frozen thing too.

here we go:

Honda Civic Si AccessTUNER Tuning Guides, Worksheets, and Tuning FAQs. - COBB Forums

Cobb: "Removing the coolant lines to the throttle body is proving to be a "significant" modification as far as the ECU is concerned. Removing these coolant lines will likely allow for poorer fuel economy as another side effect. As will setting your fans to turn on at colder coolant temperatures. Combustion chambers are more effective at warmer temperatures and having coolant warm up your throttle body helps increase the intake air temperatures to a more efficient temperature for internal combustion. We are just stating this so you have an understanding that much of what Honda did was done correctly for a performance street vehicle. We are simply trying to do our best to explain what could be going on with your vehicle after a recent mechanical change."

Ah ok i see what Cobb is talking about now, He's talking about when the car receives cold air which is much more dense than warm air your cars computer has to adjust for that change therefore allowing more fuel to enter your engine as it tries to maintain an A/F ratio that is optimum levels for your car e.g. not too rich not too lean. That's one way that this mod is creating power, more air or more dense air tells your computer to inject more fuel creating a bigger combustion thus creating more power. In somewhat cold temperatures this 'can' lead to a decrease of fuel economy due to more fuel being injected into the engine but i highly doubt it would drastically make a difference in fuel economy if even at all. Cars have to be designed to account for differences of temperatures because cars are sold all over the world where temperatures differ even just in North America places up near Canada can get very well below 0 with the windchill I've lived in places where it was -80 with windchill and i've also lived in places where temperatures got over 100 degrees quite regularly. With such a drastic change in weather conditions if cars were not able to adjust for this then cars would not be able to be sold in certain parts of North America or their computers would have to be tuned very differently and if we were to ever move our cars from a place where it was warm to a place where it was cold we would have to get our computers readjusted every time.

However he is right about our engines needing to be at an optimum temperature for combustion to happen but, our engines already do this on their own. Engine will get hot no matter how cold the intake air coming in is. An engine is designed for this to happen that's why even when we run Nitrous Oxide (which is VERY cold) through our engines it can still account for that cold and get to an optimum temperature for combustion.

I also do agree that much of what Honda did for our cars as a performance vehicle was correct stock. We have a pretty decently made car as far as performance is concerned. However because the Honda civic is a mass produced consumer product they have to satisfy as many of their customers as possible, along with making sure it's Legal for street use in America. Therefore Honda cannot cater to only one type of consumer and one region of America because that would be bad business. To maximize profits there must be aspects of the car that appeal to the Sport compact Racing consumer, as well as the average joe daily driver consumer. They have to run throttle body coolant through the throttle body because if they did not people in Cold climate areas (Chicago, Minnesota, Detroit, New York, almost all of Canada) would not be able to drive this car safely (throttle bodies might get frozen at WOT that could be very dangerous) therefore eliminating a large portion of it's business. So you can rest at ease that in a place like San Diego where temperatures are nice year round you won't have to worry about this happening.

If it still worries you I've thought of a way to make it so that u can turn it on and off through a 4 way pipe coupling and 2 extra coolant hoses. Basically you take the bottom hose and top hose and do the same thing that i did except you use a 4 way coupling with a turn valve that goes from straight through (1 end to the other, same as just a 1/4"-1/4") to all 4 ways open. That way you can bypass the tb coolant in the summer and then have it go through the TB in the winter just by turning the valve. If you want since u live in San Diego i can do it for you.

I guess using 91 octane gas instead of 87 would help with ease worries you might have about losing fuel economy.

I'm not sure what the reasoning behind warmer temperatures making your internal combustion better is, because every air induction mod that we do for cars aims at lowering the temperature of incoming air into the engine. That's why CAI's work and Intercoolers/Aftercoolers work and we have IMG's and TB Spacers and Gaskets those are serving the same purpose. They are aimed at trying to make the incoming air into the engine colder. The intake manifold gaskets and Tb spacer + gaskets are actually a good combo in conjunction with this TB coolant Bypass because then the entire intake pathway until it hits the engine will drop in temperature which makes for more power.

However thank you for the information it's always good to have all the facts before anyone decides this is what they want, because it's all up to the individual if they want this mod or not.


Here is a site that did the TB coolant bypass on a Integra LS motor and the guy dyno'd and found 10 ft/lbs of torque after car was at operating temps

Free Mods for your Honda Prelude, Gain Horsepower for Free, 97-01 Prelude, cheap horsepower

There's a little blurb about weird idles at the bottom but I didn't notice anything different about my idle. Just make sure there are no leaks and nothing is left just open cap everything off.

Actually maybe when Galaxy comes to my place to do this mod we'll take pics or record video of me doing it on his car and post it up in here. Stay tuned ^^