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I was wondering if anyone has capped only one of the two lines to the TB and if it is detrimental at all. I just got rid of my rats nest and am doing a custom solenoid rack, so if I can lessen the lines down there it would be nice. Right now I'm using the upper TB to Engine hose as a coolant temp sensor line, so I don't want to cap this one. I would like to cap the line between the water pump housing and the lower TB. Has anyone done this? All the write-ups and searches I could find referred to capping the upper TB to Engine line, haven't been able to find anything on the lower one or ONLY capping the lower one. Pictures of what I'm referring to are included. Thanks in advance.
By far the easiest/best way to do this is to take that line going from the back of the engine and connect it to the nipple on the water pump housing. You can't just dead-end a coolant circuit, you'll get a lot of trapped air in there.
I've had my car like this for some time, works perfectly fine and the sender for the gauge is still happy (I have my gauge setup just like you do).
You will have to deal with the thermowax on the throttle body, there's a number of threads about it. If you don't you'll have a permanent 1500 RPM idle.
By far the easiest/best way to do this is to take that line going from the back of the engine and connect it to the nipple on the water pump housing. You can't just dead-end a coolant circuit, you'll get a lot of trapped air in there.
I've had my car like this for some time, works perfectly fine and the sender for the gauge is still happy (I have my gauge setup just like you do).
You will have to deal with the thermowax on the throttle body, there's a number of threads about it. If you don't you'll have a permanent 1500 RPM idle.
Dale
Ah I get you, so just completely blocking the TB off then, didn't realize I could just route between the water housing and the engine. Any idea how that does in the cold? I live in a pretty cold place, usually below freezing but not often under 0 F, and I know those coolant lines were meant to help with cold starts.
And yeah lol, I got the gauge setup from one of your old posts!
I can't directly speak for how the TB does in very cold weather, it's never gets that cold here. But from what I understand it's not that big of a deal. Also I imagine if it's sub-zero temps you're probably not taking the FD for a drive
That said, you can do this so it's totally reversible down the road if you do need to reverse things for whatever reason.
Also the rat's nest is in parts, you can remove the parts the solenoids attach to and leave the fuel and coolant lines in place. The rat's nest is made of many parts held together with screws.
I can't directly speak for how the TB does in very cold weather, it's never gets that cold here. But from what I understand it's not that big of a deal. Also I imagine if it's sub-zero temps you're probably not taking the FD for a drive
That said, you can do this so it's totally reversible down the road if you do need to reverse things for whatever reason.
Also the rat's nest is in parts, you can remove the parts the solenoids attach to and leave the fuel and coolant lines in place. The rat's nest is made of many parts held together with screws.
Dale
Fair enough. I knew about the rats nest being in many parts thing, but I wanted to use as little of it as possible. Right now I'm only using the fuel lines piece. I'll probably take your advice and run directly from the water housing to the engine. Thanks!
I removed the thermowax valve and capped those coolant lines around 2009, and it's been working OK. I used a short length of coolant hose, and a bolt that fit snugly inside, and the original clamps to hold the hose onto the bolt. In hindsight it would probably have been good to run a line like Dale said, the nipple you labeled as 'Goes to bottom of TB' had some crusty gunk in it (probably from air pockets as Dale described).
My RX7 has summer tires so I try to avoid driving it much when it's cold, but the engine runs fine at 30-40 degF. The stock idle air valve can add enough air to keep a stock engine idling between 800-1800 RPM at just about any temperature, assuming the throttle stop and bypass screw are adjusted to let the engine idle around 700-800 RPM when warm. I'm using an aftermarket ECU, I wouldn't expect the stock ECU to run very well at all if you disable the thermowax valve.
I agree with DaleClark, just loop the line from the WP to the rear iron. That nipple can be a small pain to reach with the engine in the car, but doable.
Mine has been like that for years with no issues.
Originally Posted by Zezxy
...I know those coolant lines were meant to help with cold start...
I think it was to “accelerate” warm up for emissions, but doesn’t do anything for cold start itself. If it’s cold outside it will just run richer a bit longer.
I agree with DaleClark, just loop the line from the WP to the rear iron. That nipple can be a small pain to reach with the engine in the car, but doable.
Mine has been like that for years with no issues.
I think it was to “accelerate” warm up for emissions, but doesn’t do anything for cold start itself. If it’s cold outside it will just run richer a bit longer.
Hmmm.... So will the car still idle higher while warming up from a cold start? Or will it idle at whatever the normal idle is set to?
Well, it’s been a long time but I don’t recall any change in how it started. It just no longer shot up to 3k or whatever, but instead idles at a somewhat normal level. I think mine goes to something like 8 or 900 rpm and a little lumpy, but smooths out as it warms. But I get your question, and that is with a PFC.
The thermowax valve is basically a variable throttle stop that gives the engine a few percent more throttle when coolant is cold. It's like carburetor or early fuel injection technology, you're unlikely to find it on many other cars designed in the 1990s. I suspect it was kept on the car because someone on the design team had lots of experience with thermowax valves and didn't trust the ECU to always manage the idle air control solenoid properly. I'm not sure the exact RPM change you should expect, but my guess is it will add 300-500 RPM worth of airflow when the engine is cold.
Stock, the car will start at 3000 RPM for 10-15 seconds stone cold in the morning, then drop down to 1500 RPM. As the car warms, that 1500 RPM will come down to ~800 rpm, typical warm idle.
The throttle body has coolant running through it for 2 purposes - to warm the rod in the thermowax to set the cold idle and also to keep the throttle body warm. In freezing temps you can have the throttle body freeze or ice up, the coolant helps prevent that.
If you bypass the coolant in the throttle body that thermo wax will still be there. You have to either totally remove it or disable it so it doesn't hold the TB open. I saw a guy recently who had major weird problems with an aftermarket ECU - turns out the thermowax was still active and he had the TPS calibrated with the thermowax sticking the TB slightly open, causing major idle problems.
04-11-21, 11:40 AM
