H23 Plenum question...again

[Yossarian]

So i swapped the H23 plenum and TB onto my A6 today, couple things i was hoping to clear up..(I havent gotten a prelude Haynes yet) The FIV underneath the TB has two coolant lines leading to it. One pointing to the front of the car and one pointing to the passenger side. Which is the inlet and which is the return?

I just hooked it up willy-nilly and it seems to be working OK, save i havent readjusted my idle yet because one of the vacuum lines from (i have no idea what it is, really. On the right side of the intake right around the butterfly valves. but it doesnt see to connect to the butterfly valves...i could be wrong.) well, the line isnt long enought to connect, so my idle bounces from the massive vacuum leak.

Oh, and butt-dyno says to the new plenum. it doesnt seem like its got a lot more horsepower or anything, but its got a better curve i think. Pulls harder in lower RPMs and stays strong a lot higher.

Next: A4 header and Ebay CAI.

Ninja Edit: I should say, i have the coolant line from the thermostat hooked up to the nipple on the passenger side, pointing at the radiator. and the return is the one pointing at the passenger fender. Is this backwards? does anyone know? Bueller??

[lo-specials]

So i swapped the H23 plenum and TB onto my A6 today, couple things i was hoping to clear up..(I havent gotten a prelude Haynes yet) The FIV underneath the TB has two coolant lines leading to it. One pointing to the front of the car and one pointing to the passenger side. Which is the inlet and which is the return?

You don't have to connect them, just use one coolant line to bypass it.

This is how:

There is a color code in the letters...red means you just totally disconnect those, blue you connect together somehow, and white is just a guide so you know where you are in the engine bay. Oh yeah, do this mod when your car has been sitting for a while, that way you don't spill hot coolant on yourself. You'll need needlenose pliers to remove the clamps and to pull some of the hoses off, and some coolant in case you spill too much.

I took the intake piping off so it would be easier to work with. Disconnect points A and B. The hose that came from A will connect to point C, and the hose that came from B, you just put aside. some hoses are easier to connect that others, so switch them around as you like just as long as you get point C to connect with point D.

Does the metal pipe at E look familiar? there's a coolant line that runs through there so i just moved it under the intake pipe. F is the main coolant line that runs back to the radiator. D is located just above F, near the block. The next picture illustrates that the best:

Once you get C to connect D using any combination of hoses, then you're pretty much finished. This is what the final layout should look like:

for your reference, the stock flow goes from A to B to E to D. Points A and B are input and output from the throttle body. we simply bypass those by adding the point C and connecting it to E. I have no clue how this mod adds power, but i know it does. I felt a slight gain after doing this, plus my gas mileage is slightly better. my engine temp gauge sits between 1/8-1/4 depending if it's cold or hot outside. normally it would of been at 1/4-1/2. so my guess is that the engine runs slightly cooler, thus adding more power. hell it works.

[owequitit]

The coolant lines and vacuum lines should be covered in my DIY.

Glad you like it so far.

I don't think it was good for an earth shattering amount of power either, but yes, it did significantly extend the useable powerband.

Also, it depends on what cam you have.

[deevergote]

My friend bypassed all the coolant lines and has no trouble. Not that it's a good idea, but it's something

[Yossarian]

Bypassed the FIV and plate warmer. My idle is bouncing again, but erratically.... It will idle at 1500. Then drop to 900ish. Then itll bounce from 1000-1500, then itll even out at about 800. Its driving me nuts, i dont have any loose vacuum lines and its impossible to set my idle properly with it going crazy. Bleh, ill look at it tomorrow.

[93twodoorLX]

deevergote is refering to me, I have NO coolant lines going to my intake manifold at all. i will put the IACV coolant passage back on in the winter time but for now its off and i have zero problems. my car drives perfect. right now i dont even have a FITV. i took it off and made a plate. i did it all in the name of cooler intake temps and it does seem diff. to me. but at for your idle bouncing around, you probably need to adjust the srcrew on the TB. I had the same exact problem a while back before i did the f22a6 manifold swap with h22 plenum. all i had to do was adjust it down and the bouncing went away i think im proof though that it is possible to have no coolant hose heating the intake manifold sensors or valves for the thing to work. i'll take pics someday if anyone at all is interested

p.s. and yes it is a good idea no matter what deev says LOL j/k we'll see how winter time treats it

-sean

[Yossarian]

deevergote is refering to me, I have NO coolant lines going to my intake manifold at all. i will put the IACV coolant passage back on in the winter time but for now its off and i have zero problems. my car drives perfect. right now i dont even have a FITV. i took it off and made a plate. i did it all in the name of cooler intake temps and it does seem diff. to me. but at for your idle bouncing around, you probably need to adjust the srcrew on the TB. I had the same exact problem a while back before i did the f22a6 manifold swap with h22 plenum. all i had to do was adjust it down and the bouncing went away i think im proof though that it is possible to have no coolant hose heating the intake manifold sensors or valves for the thing to work. i'll take pics someday if anyone at all is interested

p.s. and yes it is a good idea no matter what deev says LOL j/k we'll see how winter time treats it

-sean

Hell, that makes perfect sense to me...why heat the intake more than it already is? .... i did stash the hose for the FIV/Throttle warmer though...it gets cold up here, lol.

I'll adjust my idle tomorrow and see if that helps, hopefully thats just a goofy trait from having the idle screw misadjusted.

[owequitit]

It might make a small difference just off idle, due to intake air charge heat soak, but I am pretty sure it isn't significant at speed, because the air is moving fast enough that it doesn't really heat up too much.

The FIV and the coolant in the TB is primarily to keep the metal warm enough so that ice doesn't form on cold or humid days. It is nothing like carb icing though.

Also, a phenolic IM gasket would help.

That way the IM doesn't absorb as much heat from the head.

I bet you could see a 10-20* IAT drop from removing the TB coolant, and an phenolic IM gasket.

That would probably be worth something.

[93twodoorLX]

It might make a small difference just off idle, due to intake air charge heat soak, but I am pretty sure it isn't significant at speed, because the air is moving fast enough that it doesn't really heat up too much.

The FIV and the coolant in the TB is primarily to keep the metal warm enough so that ice doesn't form on cold or humid days. It is nothing like carb icing though.

Also, a phenolic IM gasket would help.

That way the IM doesn't absorb as much heat from the head.

I bet you could see a 10-20* IAT drop from removing the TB coolant, and an phenolic IM gasket.

That would probably be worth something.

well i do have the TB coolant bypassed and a phenolic manifold gasket and honestly it is noticable. not like WOW i need to shout this from the rooftops but a nice little improvement of conservative stock. i like it

-sean

[Yossarian]

Ahhh, i missed a vacuum line when i was hooking everything back up...Bleh. now i have a nice steady 800ish rpm idle. On a similar note, what would it take for the IM to outflow the head?

[owequitit]

well i do have the TB coolant bypassed and a phenolic manifold gasket and honestly it is noticable. not like WOW i need to shout this from the rooftops but a nice little improvement of conservative stock. i like it

-sean

Ah. Didn't see that you had the gasket too.

I didn't notice much difference on the with the bypass, but with the bypass and the gasket, the manifold stays noticably cooler.