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Pete_89t2

Difficulty getting a stable idle on a FD RX7 with an Ethrottle, Link G+ Fury

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I'm having difficulty getting my E-throttle equipped FD to achieve a stable idle at about 1K RPMs when warmed up - the idle will hunt wildly above & below that mark by a few hundred RPMs, and sometimes stall with no load on the motor. The car starts up fine, settles into its higher cold idle target, but as the coolant temps start approaching about 80*F and go hotter, the idle starts hunting - which just gets worse as the idle target RPM drops and temp increases.

Oddly enough, the car runs OK when it's under load - if I drive off, AFRs stay reasonably close to the cell targets, though the VE table still needs a bit of tuning.

I attached the car's current tune, hopefully someone can take a look and point me in the right direction on how to fix this? Would have attached a log, but my logs were too large to attach here. Anyway, here's some pertinent background info on the car's setup as I got it from the previous owner: (1) New Mazda 13BREW short block (no compression issues); (2) Single BW S364.5 SXE turbo, 1.0 AR turbine housing; (3) Fuel injectors - Bosch 1000cc EV14 primaries,  Bosch 2200cc EV14 secondaries; (4) Rest of the fuel system is a Fuel Lab pressure regulator, and there's a fuel pressure sensor wired to the Link. Fuel pump is still the stock FD pump driven by new relay/wiring (simple on/off control); (5) DBW throttle is a 90mm GM e-throttle body with a custom fabricated adapter to mate with the intake manifold, which is a Cosmo 13B-RE upper & lower intake manifold.

Thanks!

Baseline Tune 0947-3-15-2020 v002.pclr

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For your logs the easiest option is use something like google drive, onedrive, dropbox or similar, then just put a link to the file in your post.

For the idle I have a few suggestions:

  • The idle ignition table is "back to front". It should have more advance on the right-hand side of zero error (when RPM is lower than target) and less advance to the left of zero. 
  • You've also got quite a bit more advance at idle than is common for a rotary.  Im no rotary expert but the few I've done seems happiest around zero deg at idle.  I think stock FD is -5. 
  • E-throttle target table has zeros in the top row.  The recommended setup is to have most of the throttle opening required for normal idle to come from this table then the idle base position only have a small extra trim for cold start etc.
  • Your firmware is quite old, I suggest you update to the latest as there have been several small idle related fixes of improvements since.

In the attached map I have had a stab at fixing some of these - you will need to do the firmware update yourself.  I havent changed the idle ignition all the way to what I would normally run but I didint want to change too much at once.  You can use the compare function in PC Link to see what I have changed.

The fuel table also needs you to give it a tidy up around the idle area, I havent touched that since there is no data to guide me.  But having a cell with 98% right next to a cell with 46% is unlikely to ever work well.

4VywBOh.png

Idle tweaks.pclr

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Thanks Adam, I'll give these suggestions a go.

Probably a dumb question, but is there a download link somewhere on this site for the current G4+ firmware? Can't seem to find it anywhere.

On the fuel table, I think I misused the VE Mixture "correct fuel table" feature - accepting a bunch of changes to the fuel table prematurely, based on too few samples/bad data. Easy fix there, just go back to my original baseline.

Regarding timing at idle, I've had good results in the past setting the idle region around 12~15* BTDC on similar 13BT / 13BREW builds; that additional advance typically results in a smooth idle and a nice throttle tip-in. Basically it perks up the throttle response a bit as you drive off normally in NA mode. But this is the 1st time I'm trying it with a non-stock TB, which I suspect could be another problem here. The stock mechanical TB has mechanically linked primary & secondary throttle plates; the secondaries don't crack open until the primary opens a bit, and even then there's a double throttle mechanism that which blocks the secondaries until the coolant reaches operating temp. Air delivery with a single 90mm DBW throttle is a very different beast, unknown territory for me.

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The firmware is part of the PC link tuning software download so as long as you have the latest G4+ PC link you then have the latest firmware ready to install to the ECU.

Ill let @Adamw carry on with the rest.

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19 hours ago, Pete_89t2 said:

Regarding timing at idle, I've had good results in the past setting the idle region around 12~15* BTDC on similar 13BT / 13BREW builds; that additional advance typically results in a smooth idle and a nice throttle tip-in. Basically it perks up the throttle response a bit as you drive off normally in NA mode. But this is the 1st time I'm trying it with a non-stock TB, which I suspect could be another problem here. The stock mechanical TB has mechanically linked primary & secondary throttle plates; the secondaries don't crack open until the primary opens a bit, and even then there's a double throttle mechanism that which blocks the secondaries until the coolant reaches operating temp. Air delivery with a single 90mm DBW throttle is a very different beast, unknown territory for me.

I suspect if you have idle timing that high you will have very little authority left to increase torque using idle ignition control (i.e it will already be near peak torque timing).  Try it and see but I think you will need lots of idle ignition authority to get decent idle control with a large slow E-throttle.  

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13 hours ago, Simon said:

The firmware is part of the PC link tuning software download so as long as you have the latest G4+ PC link you then have the latest firmware ready to install to the ECU.

Ill let @Adamw carry on with the rest.

Thanks Simon, I ended up figuring that out for myself just by dabbling with the firmware update menus in PCLink. I updated my FW to the most recent version that my copy of PCLink had on file - there were 2 FW versions in the firmware directory, so I updated to the one with the highest revision # and latest file date.

On the FW topic, how frequently do you guys release FW updates? I don't have my version # handy, but since it came with my copy of PCLink that I downloaded in November 2019, it can't be any newer than that - have any FW updates been released since then?

5 hours ago, Adamw said:

I suspect if you have idle timing that high you will have very little authority left to increase torque using idle ignition control (i.e it will already be near peak torque timing).  Try it and see but I think you will need lots of idle ignition authority to get decent idle control with a large slow E-throttle.  

You nailed it Adam, the timing & idle tweaks you provided pretty much solved my idle problems! I applied all of the tweaks you provided as-is and reverted the fuel table back to my original base map to correct those bad cells and did some testing. Starting up from cold (ambient temps ~50*F), it fired up easily, and idled almost spot vs. ECTs on to the base idle target table as it warmed up. Once at operating temp (ECTs > 176*F), the idle speed overshot the target slightly by about 50~100 RPMs with a very small hint of hunting around its attempted idle target. Much more stable than before though.

First thing I think I should try to refine it further is to just reduce the base idle position table values from the current 1.0% down to perhaps 0.5% in the cells 176F and higher. That should get me closer to the target idle when warmed up, and if the current PIDs are good enough enough, result in less hunting around the idle target.

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17 hours ago, Pete_89t2 said:

On the FW topic, how frequently do you guys release FW updates? I don't have my version # handy, but since it came with my copy of PCLink that I downloaded in November 2019, it can't be any newer than that - have any FW updates been released since then?

November should be the latest.  You can see the release dates on this page:  https://www.linkecu.com/software-support/pc-link-downloads/pc-link-legacy-software/

 

17 hours ago, Pete_89t2 said:

First thing I think I should try to refine it further is to just reduce the base idle position table values from the current 1.0% down to perhaps 0.5% in the cells 176F and higher. That should get me closer to the target idle when warmed up, and if the current PIDs are good enough enough, result in less hunting around the idle target.

Attach another log and I will make some suggestions.  The "50-100RPM overshoot" is probably just because there is currently an 80RPM deadband set on the idle speed control.  That means it is not going to attempt to adjust throttle if the idle is within 80RPM of target.  

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On 3/18/2020 at 3:16 AM, Adamw said:

November should be the latest.  You can see the release dates on this page:  https://www.linkecu.com/software-support/pc-link-downloads/pc-link-legacy-software/

 

Attach another log and I will make some suggestions.  The "50-100RPM overshoot" is probably just because there is currently an 80RPM deadband set on the idle speed control.  That means it is not going to attempt to adjust throttle if the idle is within 80RPM of target.  

Ok, thanks! I reduced the deadband to 25RPM and reduced the idle base position to 0.7% (from 1.0) for ECTs above 194*F and did some testing/logging today. I don't think the ECTs made it much past 190*F on this drive, so it's possible the idle base position tweaks didn't come into play. Attached is the current PCL file, and here's a link to my Google Drive where you should be able to get the log file: https://drive.google.com/drive/folders/14YW4Yrme85dJZxLmVlBplBXHdVE6ezdI?usp=sharing

There's about 23 minutes worth of data there, from cold start through warm-up cycle, and driving around town with several stops idling at traffic lights

Baseline Tune - with Link Updates v005.pclr

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Its not looking too bad but I just noticed a stuff up which means we might have to have another go at it.  Your "fan 2" is on all the time which would mean the fan step would have been acting all of the time.  I suspect if we fix this it will throw the idle base position out again and the E-throttle target will probably need a tweak too.  So, can you set the FAN 2 temp to something like 150deg C so it never activates.  In the idle settings change the fan step to something like 0.3%.  Do another log of a cold start, idling until warm.

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6 hours ago, Adamw said:

Its not looking too bad but I just noticed a stuff up which means we might have to have another go at it.  Your "fan 2" is on all the time which would mean the fan step would have been acting all of the time.  I suspect if we fix this it will throw the idle base position out again and the E-throttle target will probably need a tweak too.  So, can you set the FAN 2 temp to something like 150deg C so it never activates.  In the idle settings change the fan step to something like 0.3%.  Do another log of a cold start, idling until warm.

I didn't even consider "fan 2" because that fan is not actually being controlled by the ECU - another one of the previous owner's wiring faux pas I have to fix when I rewire the car. He actually had the 2nd FD fan wired to come on constantly as soon as the ignition switches on, and the main FD fan is controlled as "fan 1" by the link. So for now, while temps are still cool here, I disconnected the 2nd FD fan (so the car can actually reach operating temps), and have been relying on the main fan, controlled by the "fan 1" settings.

Anyway, I see what you're referring to - I went ahead and changed "fan 2" to come on at 212*F, and changed the "fan step" in the idle settings from 3.0 to 0.5. Idle is behaving reasonable well with those settings. Attached is the current tune file and a log from cold start, warm up & some driving and idling around town thru a few fan cycles. About 13 minutes worth.

Log 2020-03-21 10;32;44 am.llg Baseline Tune - with Link Updates v006.pclr

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