To thermowax, or not...
 

So now that my car is down due to another busted turbo, I'm pondering the use of the thermowax. I still have the one I took off my throttle body, and was wondering if I should reinstall it. Keep in mind that I do have a standalone ECU.

Here's the real question: Does the BAC valve have what it takes to keep the idle up when the engine is cold? Right now, I have the idle speeds set to 2000 rpm when the coolant temp is 60F, and it's a linear drop to 1000 rpm at 185F. The engine idles, when warm, at 1000 rpm with the BAC valve completely shut. But when cold, the BAC stays wide open and the car barely idles at 750. Should it be idling the car up more than that, or is my decision to remove the thermowax a bad one.

I just thought with the standalone that the BAC could do the job of the thermowax, but I'm not so convinced now. Any inputs? :scratch:

Something isn't set up right if it's idling at 750 RPM cold, yet 1000 RPM warm. With a stock ECU, the 3k RPM cold start idle is a product of the thermowax opening the throttle plates a bit more, and the BAC and AWS valve dumping extra air in.

Let me rephrase that :)

I don't have the thermowax on the throttle body, but I still have it. I was pondering putting it back on if the BAC can't keep the idle up when the engine's cold (and having to be soaked with fuel to keep it running.)

If you have it all intact, put it back on. I did and it works WONDERS for me. I have a standalone (haltech E6k) and I can never quite get the BAC functioning like I need it to. My case is pretty weird though as the BAC doesn't kick in until 10-15 seconds after startup. I don't know why, problem with my computer I suppose... The thermowax really helps me with this now that the cold weather is here. I can even unplug my BAC, and the car will start and idle perfectly without it. As it warms up, the idle will drop. I'd say it'll start cold at 1400RPM, and when fully warm idles at 1000RPM.

Now i gotta go make a gasket for it, then plumb the coolant hoses to the TB... son of a bitch.

That's good news though.

BTW, if you're having issues with your standalone not turning on the BAC, this may be of some help. On the megasquirt, there's a few different settings for idle control, and one of them is "closed loop" idle control. There are other settings, such as PWM warmup, which is stupid because all it does is keep the BAC at a certain percentage at whatever temperature, regardless of engine speed. It doesn't adjust it based on load. "closed loop" keeps it at a certain RPM based on coolant temp. On top of that, there's a setting for it under cranking duty. If you have an adjustment for the idle control valve to open the BAC during cranking, try fiddling with it to see if that makes it operate for those 15 seconds.

Not saying it's going to work though. Thermowax seems like the way to go :)

The thing with mine is that I have it working OK, but for some reason if REFUSES to kick in until after the engine is running 10-15 seconds. It does work because when I turn on all my lights and the heater for example, the idle will drop a little then come back up real quick. Plus if I unplug it the idle will stay a bit low. Maybe it's just an old BAC and "sticks" until the engine has shaken a bit and got it moving again. Hell if I know I suppose I can try another one.

PS
What are your BAC settings with your megasquirt? I can never quite get the opening and minimum positions. I have no idea what the stock one does. I only figured out the stock PWM

Here's some screen shots.

I assume things will change once I get the thermowax back on :nod:

your setup is more advanced than my primitive E6k. My settings are simple:
target idle rpm: what I want the car to idle at
cold idle up rpm: when the engine is cold (setting below), the car will add this RPM on top of the target idle rpm
start rpm: an extra rpm added for 20 seconds right after the car starts
cold temp limit: temp value for a cold engine (below this number is "cold", above is "hot")
cold min position: when the engine is "cold", the valve holds open this much
hot min position: same as above, but when "hot"
cold opening position: how much the valve opens when cold during cranking
hot opening position: same as above, but when hot

that's all I have. It's a tricky guessing game, especially when cold because I have a small window to do it all in. I don't really need it when cold, but I want it when hot. For example I want it to bump the idle a bit after I start it up on a warm day for those first few seconds. Can't seem to get that consistently...

Wow. And I thought my MegaSquirt was primitive, having to build it yourself and all, and only spending $400 for the whole thing, wiring included :)

https://www.rx7club.com/attachment.p...7&d=1322879427

where's your duty vs temp table? it seems like this one

https://www.rx7club.com/attachment.p...4&d=1322879427

would be for cranking only? Also what's your timing during warmup?

There is no duty vs. temp table if it's set up for "closed loop" idle control. It's rpm vs. temp, so the BAC is constantly changing its position to maintain that specific rpm. The trouble is, during cold starts I don't think the BAC valve can bypass enough air to keep the RPMs up.

That second one is for cranking only. It opens the BAC that much only during cranking, but closed loop idle control takes over shortly afterwards.

I actually didn't know (or remember) there was an adjustment for timing advance during warmup. I'll have to look in to tuning that some more. I think I may have done something with it a while back, but completely forgot about it. Here's what it's at currently.

Yes it can. During my many times of experimenting, I had it bump the idle in sub freezing weather (no thermowax). Not fun sitting outside with the laptop when it was that cold though! :)

How high could you get it?

Maybe my throttle stop screw setting is wrong. It was already messed with when I first got the engine. I adjusted it until the throttle plates were completely closed, then started the engine and fully warmed it up. I then noted at what throttle position the car held a steady 1000 rpm idle, and turned the engine off. I then adjusted the stop screw to that position, and re-calibrated the TPS. Things were better, but cold starts still caused it to struggle. Even with the BAC fully open it'd struggle to maintain an idle. That's why I'm thinking that with the thermowax installed, the throttle plates can be open a little more on cold starts and the BAC valve can supplement the idle as necessary.

I just can't see why it won't idle up cold, even with the bac fully open. :dunno:

What I did, when playing with the settings, was remove the BAC from the manifold and look at it. I could see the plunger moving in and out depending on what numbers I changed. You will see it opens quite a bit. Since my E6k is different than your megasquirt, I can't say for sure what you should do. If I set mine to 100% open, my idle shoots up past well past 2000. If you think about it, 100% open BAC is similar to completely taking it off and leaving that hole open on the manifold. That's QUITE a large vacuum leak.

I looked at your frequency and it does seem off. The stock valve operates at 244Hz. You are using a 3 multiplier on 30.5Hz. You are only about 1/3 the frequency. Real easy, change the multiplier to 8. It's exactly 244Hz. You should hear a faint humming from the valve.

I'll be damned. I went on Aaron Cake's writeup and it said to set the valve frequency at 78, which would explain why I have it at 3*30.5 (I set it at 2.55, but the tuning software changed it to the nearest whole number) . I'll change that once I get the car running again. I just disassembled my turbo to find out that this time, the damage is worse than I thought. It damaged the backplate, thrust bearing, and the thrust collars. Time for more money :(

Hey that's OK... my pulsation damper started leaking today... it has less than 2000 miles on it. I just splurged on summitracing and bought a bunch of fittings and hoses. Might as well replace everything...

POS pulsation dampers. There has to be some sort of aftermarket solution for those damn things. (aside from the banjo fitting fix)

I'm putting some metric to AN adapters (on the rail), and then some AN hose fittings. bought some stainless braided line. Why not? :)
I run an aeromotive FPR. Aftermarket regulators have the pulsation damper built in so I am OK.

I was pretty pissed too this morning... it was cold but I've really been getting the tune right. Started up in a split second, 40 degrees no problem. Smelled fuel. Not just from running rich, it was definitely in the engine bay. I started looking and couldn't see. Finally I touched the back of the secondary fuel rail and there it was. Shut the car off and essentially called it a day. :(

PS
my rails are J-spec for some reason. regulator is on the primary rail, and damper is on the secondary. Also means the fuel flows "backwards".

I kind of skipped through the thread....

You don't need the thermowax with a standalone and the BAC. The 'Squirt will be happy to run the BAC for the cold high idle. This is generally how I set them up.

Regarding BAC frequency, I've always run them around 100Hz and never had an issue.

100Hz will work too, a little noisier than stock. Typical BAC valves run 100 to 300Hz.

I'm going to ultimately ditch the BAC and run a GM idle motor using this:
http://www.risingrpm.com/products/pr...rx7_turbo2.asp