Cold Start Issues S6 RX7,

[kenjamin]

A newb here.

During cold start it will start and idle at 2000 rpm and for about 15 sec. the rpm would drop and would die. 

 

Here's the log attached.

 

Could not find any culprit. I even allowed the CAN lambda to be on prior to starting.

 

Thanks

 

Ken 

Cold Start Issue.llgx

[DerekAE86]

Attach your tune file too

[DerekAE86]

It's hard to say without seeing the tune file - but it appears your idle control isn't configured correctly which is resulting in large / erractic TPS movements via the ethrottle that is showing up as a big swing in manifold pressure which is causing the accel fuel settings to dump extra fuel in.

Also your fuel temp is reading at -18deg which probably isnt helping the fuel model formula.

[Adamw]

Idle control is not even working in that log as it is above your RPM lockout most of the time.  Can you give us a log of the RPM "dying", as the lowest it goes in that log is about 1220RPM which is still 200RPM above your target.  And a copy of the tune too.

I would say it is mostly just too lean, but obviously idle control will need to be set up correctly too.  

 

[DerekAE86]

Ah yeah I just saw all the tiny TPS movements and assumed it was ethrottle idle control. But theres nothing on TPS(sub) so it isnt even ethrottle.

Were you touching the pedal constantly?

[kenjamin]

Thank you guys for replying.

 

No Fuel temp are connected. It’s blank.

Yes I was blipping the throttle to prevent it from dying. I’ll log a cold start and not blip the throttle and see what the log will say.

Ken

[DerekAE86]

4 minutes ago, kenjamin said:

No Fuel temp are connected. It’s blank.

The RX7 S6 supplied map has fuel temp configured on AN3. Have you changed the source to none?

If the Idle starts high and then drops/stalls unless you keep touching the throttle it sounds like you don't have enough air going on.

It's possible your start-up idle valve offset is too high to start with, then decaying too quickly to a base value that is now too low to maintain idle. Again - would be much easier to see potential issues if you attached your tune file.

[kenjamin]

I switch some Input around to accommodate my harness ( no longer OEM) but here's the tune file.

 

Everything seems to work but just the idle I'm having trouble with.

Ken

Ken August 28 Cold Start Update.pclx

Heres a cold start Log. Did not touch pedal let the car die.

 

Thanks

Ken

Cold Start Issue Log 1.llgx

[DerekAE86]

I've never messed with a Rotary engine so don't take my value suggestions as gospel but this is what I'm seeing;

Your crank enrich appears to be a bit high (106.4%) so when the engine starts its initially very rich (0.733 Lambda).
Once the post start enrich kicks in it drops down to 28.1% and your Lambda is on target at 0.910~ish.

Looking at this I would be inclinded to reduce your crank enrich to somewhere between its current and the max post start. Maybe 70% and see if it still fires without trouble.

I would then increase the post start and even warmup enrich by an additional 5ish% just so you've got a little extra fuel to play with during the cold start period. Even though it's currently on target, a little more won't hurt and will actually help if your idle starts to struggle due to air or timing problems.

However the main issue with the engine stalling appears to be the idle control. Firstly there is a 10s startup hold time and then a 10s decay.
So idle control isn't doing anything until 20s in - which is when you stall. (More on why later)

It looks like 43.5% base + 12% startup offset is too much air on start up. This coupled with the crank enrich fueling is probably the cause of your 2000+rpm post start condition.

Try dropping the base idle position to 35% for everything less than 60deg and the startup offset to 10%. This should get the initial opening values of the idle valve more in the ballpark. Then drop your startup hold time and startup decay times to maybe 5s each so the actual idle control can start sooner.

Then the final thing which is actually causing the stall; the MAP lockout is currently 50kPa. And you are exceeding this just after your idle control turns on.

So whats currently happening is the idle control is locked out for 20s during start up (10 hold +10 decay) so your RPM is high.
Once idle control turns on it rapidly closes the valve to 35% to bring down the RPM but then your manifold pressure jumps to above 50kPa which casues the idle control to lockout again so it cannot save the resulting stall.

If you increase your MAP lockout to something much higher like 80kPa it won't cause any problems. But this value should be set based on the manifold pressure of your engine when you're actually driving/cruising. It has to be higher than (stable) "idle" but lower than "cruise".

 

Also; the Fuel Temp "error value" is set at -18deg which is why it's showing as -18 in the log. The error value isn't the threshold the temp has to get to before it throws a code, it's what the ECU will assume the temp is if the sensor fails. So usually the error value is set to a assumed fail safe value of what the "typical" temp would be. In the case of fuel I would guess it'd typically be around 35deg.

But with the Fuel Temp source set to none I assume this error value is not being taken into consideration at all anyway.

[koracing]

3 hours ago, DerekAE86 said:

If you increase your MAP lockout to something much higher like 80kPa it won't cause any problems. But this value should be set based on the manifold pressure of your engine when you're actually driving/cruising. It has to be higher than (stable) "idle" but lower than "cruise".

I agree with most of what you said, except this.  Most engines I tune with a single throttle body and plenum can cruise at a much lower manifold absolute pressure than the car idles at -- particularly if there are larger cams and the idle rpm is under 1000rpm.  RPM lockout above target should handle this mostly and just need to get it idling well and set the MAP threshold above the cold and warm idle map values by some margin.

[DerekAE86]

Thats fair. The important thing is just setting the MAP lockout above what you'll ever see during idle.

Honestly for my car I just set it to 150 which is impossible to achieve with a NA engine so it never comes into play and use TPS/RPM lockout only.

[kenjamin]

Thank you guys for replying. I appreciate it. I’ll play around with the idle using everyone input and keep you guys updated.

 

Ken

[kenjamin]

Tried the setting Derek recommended. It worked well. RPM didn’t jump to 2000rpm but rather 1100rpm and stayed there till warm.

 

Thanks a lot, will have to adjust a bit once I get a hold of my tuner.

 

Thanks everyone. Much help

 

 

Ken