coolant bypass the throttle body??

[randomwalk101]

I know a few of you guys have done this. I live in Texas so freezing is never a problem. THe last time I attempted to do a coolant bypass was when I first bought the car in 1995 (GSR w/out JRSC installed). The idle fluctuated like crazy so I swapped it back. I bypass by connecting the two coolant hoses that go through the throttle body with a straight pipe...I'm not sure that is the way it supposed to be done..I have no idea what the hell I was doing...and that is my question...can you bypass coolant to the throttle body without some crazy idling problem? How do you PROPERLY do a by-pass?

[88 SC CRX Si]

All your doing is bypassing the two small coolant lines (inlet/outlet) that goto the EVAC. I just used a "barb" from the hardware store, to hook booth hoses togather to make one.

I did not have any problems with my idle tho. Might try reseting your's, if you try it again.

-Ryan-

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"Noth'in like Induction..."

88' CRX Si - JRSC @ 6psi
Endyn/Bosch FP, CarTech FMU, B&M CommandFlo
AutoMeter - Phantom FP, A/F, Boost gauges & pods, B&M FP Set
Eibach Pro-Control Bars, ARP Head Stud Kit, AEM Pads

[Mochanic]

If you are talking about the EICV (Electronic Idle Control Valve, or sometimes call an EACV for electronic air control valve) (not an EAVC) Then this is not correct!!!

You only bypass the inlet and outlets of the throttlebody! Bypassing the EICV will definately cause an idle problem! The only reason you bypass the TB is so that you are not heating up the incoming air charge! (for emissions and de-iceing).

Randy

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If your gonna do it, Do it right! Damn It!

[This message has been edited by Mochanic (edited May 24, 2001).]

[TrustGs-R]

agreed with mochanic...

coolant that goes to warm the TB is bypassed....so it's feeding coolant straight into what i know as mister IACV. Idle air control valve.

i've never heard of idle problems from the TB bypass before.

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96 gsr hitting 12s
90 hybrid hatch hitting 14s

[5 Liter Eater]

I tried bypassing several different ways, the last and most logical was to bypass the TB by going from the head to the IACV and back. This still gave me a fluctuating idle. There is a thermovalve in the throttle body which apparently causes this. Someone told me that they opened up the water inlet of the TB and tightened this thermovalve and the problem went away but I was done screwing with it for such a miniscule mod.

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Bill Winters
Houston, TX
'94 bone stock GSR w/ home made CAI

"I will gladly pay you Tuesday for a supercharger today."

[Mochanic]

The thermo valve you are refering to is called the fast idle valve which simply raises the idle when the engine is cold.
You did have a good point!
You would have to remove the end cover of the fast idle valve and completely close this off by screwing in the valve so that the fake vacuum leak that is created by this valve can no longer work!

Randy


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If your gonna do it, Do it right! Damn It!
"Nothing feels as good as being Blown!"

[This message has been edited by Mochanic (edited May 24, 2001).]

[rjaffey]

Why would shutting off the coolant flow through the IACV (Intake Air Control Valve, EICV, EACV, why do they keep changing the name?) cause idle "problems" in warm climate? The coolant flow through there is only to preheat the air which it supplies to the engine and prevent it from icing. The signal from the ECT (Engine Coolant Temperature sensor), is what the ECU uses to determine what the target idle speed should be. With that value the ECU monitors RPM and increases or decreases the amount of air flowing through the IACV as necessary.

Some other random thoughts: The Fast Idle Thermo Valve works along with the IACV. The former supplies additional air which allows the IACV to operate over a narrower range than it would otherwise have to were it the only route for the extra air needed for fast idle. It already has to regulate idle air flow to account for accessory load. I can see how having a cold Fast Idle Thermo Valve might cause the IACV to close all the way, thereby taking control away from the ECU and allowing the RPM to change due to varying accessory load. Has anyone observed this? It makes closing the Fast Idle Thermo Valve, or at least closing it down somewhat, sound like it might be a good idea.

If you want to keep as much heat as possible from transferring from the coolant to everything downstream of the TB you have to stop coolant from flowing through both the Fast Idle Thermo Valve and the IACV.

As the weather is warming up, I'm going to try this mod. It seems likely that a hot throttle body contributes to the rising intake temps over time due to heat transfer from the intake air by the intake casting, blower, and intake manifold while cruising and idling. Those should be times when all of the downstream components get some cooling effect from the constant flow of unheated air, but the readings I took indicate that this isn't happening.

If it looks like a good idea, I'm going to implement as a shutoff valve in the coolant line. This way I can easily open or close it as necessary, obviously open in the Winter, etc.

[This message has been edited by rjaffey (edited May 24, 2001).]

[88 SC CRX Si]

I got it mixed-up, it's the EACV or IAC. Like everybody said, all it does is pre-heat the the TB.

My bad, for causing all the confusion..... AGAIN.

-Ryan-

[Mochanic]

"Why would shutting off the coolant flow through the IACV (Intake Air Control Valve, EICV, EACV, why do they keep changing the name?) cause idle "problems" in warm climate? The coolant flow through there is only to preheat the air which it supplies to the engine and prevent it from icing."

First of all you have a fast idle valve on the bottom of the throttle body and an EICV which is right behind the TB on the intake manifold. These are not the same thing which some people don't realize.
When doing the bypass you DO NOT bypass the EICV only the fast idle valve on the TB! The coolant flow through the fast idle valve is what we are trying to eliminate, because this is what heats the air flowing through the TB to keep the TB from icing, not the coolant flowing through the EICV.
A shutoff valve in the coolant line is a good idea for those of you in the colder climates, but remimber you only want to shut off the coolant to the fast idle valve, so this would require you to add a "T" before the coolant reaches the fast idle valve then on the branch going to the fast idle valve you would install a shutoff valve and another after the fast idle valve into another "T" so that you only isolate the fast idle valve itself! (With only one "T" you would allow coolant to backup up into the outging side of the fast idle valve and therefore defeat the purpose of the mod).

Randy

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If your gonna do it, Do it right! Damn It!
"Nothing feels as good as being Blown!"

[rjaffey]

Once again, I've got to ask WHY is there coolant flowing through the IACV-EACV-EICV?

The only reasons I can see it is that it prevents the IACV from icing and preheats the air that flows through it. A side effect is that heat also passes from the coolant into the side of the throttle body and the inlet casting just past it.

The coolant passing through the Fast Idle Thermo Valve serves three functions that I can see:

1) It operates the temperature dependant air bypass valve to provide more air when the coolant is cold so the IACV isn't forced to open beyond the range where it operates effectively to provide fast idle when the engine's cold.

2) It warms the throttle body from the bottom thereby warming the air that passes through it.

and

3) By warming the throttle body it also prevents icing.

The coolant passing through both of these components does heat the throttle body and therefore the intake air. More at idle and cruise than at WOT. How much? I'll post the numbers when I have them.

Anyhow, I see absolutely no reason why one shouldn't shut the coolant off to both of them if one is going to do it at all. Complicating the system with tee fittings seems totally unecessary and counterproductive. As for using two valves for total isolation, how much coolant is really going to back up through these components if the there's only one valve shutting off the flow from one end?

Am I overlooking something?

[This message has been edited by rjaffey (edited May 24, 2001).]