Accel enrichment needed on Budget Miata standalone?

[turbogrill]

Hi,

 

Looking into converting my 1.6 NA Miata to standalone, the theme is simplicity and budget.

 

Would accel enrichment be needed?

 

Otherwise I can reuse the old TPS, some installs require a 1k inline resistor in place. Easy.

There is no such thing as throttle modulation on a stock 1.6 NA, you are either braking or 100% WOT. 

 

Edited December 14, 2021 by turbogrill

[krispykritter]

What standalone are you looking at?

[petawawarace]

1 hour ago, turbogrill said:

Hi,

 

Looking into converting my 1.6 NA Miata to standalone, the theme is simplicity and budget.

 

Would accel enrichment be needed?

 

Otherwise I can reuse the old TPS, some installs require a 1k inline resistor in place. Easy.

There is no such thing as throttle modulation on a stock 1.6 NA, you are either braking or 100% WOT. 

 

Yeah, you'd still want accel enrichment. You'd actually want it more because your going from 0-100%.  If you don't, you'll likely get a lean spike everytime you get on the throttle. May even stumble if you have zero enrichment.

[krispykritter]

There are different ways to do accel enrichment too.  I think the microsquirt can do either tpsDot based or mapDot based if you don't run a TPS sensor.

[turbogrill]

It's either:

SpeedyEFI PnP - $399 for ECU + TPS + IAT (AFM removal)

Microsquirt - ~$350  (custom harness so a little more work)

Megasquirt PnP - $750

 

SpeedyEFI is out of stock at the moment.

 

mapDot enrichment sounds like a good idea. Any reason mapDot would not work as well?

[krispykritter]

Speculation: map is an average reading, as each time a valve opens or closes it sends pressure waves through the intake manifold and into the map sensor, so the ECU takes an average of a number of samples to come to a reading.  No idea what that time interval is.  TPS is a direct measurement with much less noise, so faster reading.  It matters on these transient events as it's based on the instantaneous rate of change of the measurement.  In order to get a rate of change reading, tho, you need multiple samples, so I imagine mapdot needing multiple samples of an average sample is an order of magnitude slower to calculate mapdot than to calculate tpsdot.

 

For our purposes, though, I expect mapDot probably works fine.  I imagine a street driven car would like the faster resolution of the tps measurement, but our cars aren't street cars.

 

I don't know about speedyEFI but we use TPS with our microsquirt (and megasquirt is just a superset of microsquirt).  Is the miata not just a standard 5V sensor?

 

I just double checked - in tunerstudio with microsquirt, there's a slider that allows you to go between 100% Map-based to 100% TPS based accel enrichment.

 

Edited December 14, 2021 by krispykritter

[turbogrill]

1 hour ago, krispykritter said:

Speculation: map is an average reading, as each time a valve opens or closes it sends pressure waves through the intake manifold and into the map sensor, so the ECU takes an average of a number of samples to come to a reading.  No idea what that time interval is.  TPS is a direct measurement with much less noise, so faster reading.  It matters on these transient events as it's based on the instantaneous rate of change of the measurement.  In order to get a rate of change reading, tho, you need multiple samples, so I imagine mapdot needing multiple samples of an average sample is an order of magnitude slower to calculate mapdot than to calculate tpsdot.

 

For our purposes, though, I expect mapDot probably works fine.  I imagine a street driven car would like the faster resolution of the tps measurement, but our cars aren't street cars.

 

I don't know about speedyEFI but we use TPS with our microsquirt (and megasquirt is just a superset of microsquirt).  Is the miata not just a standard 5V sensor?

 

I just double checked - in tunerstudio with microsquirt, there's a slider that allows you to go between 100% Map-based to 100% TPS based accel enrichment.

 

 

The 1.6 TPS is just a switch, not a potentiometer. 

 

I would need this adapter, https://www.flyinmiata.com/default/tps-upgrade.html

And this TPS https://www.ecstuning.com/b-genuine-bmw-parts/throttle-position-switch/13631721456/

 

It's an $150 extra and easy to install. But there might be a few other people that is going to copy what I am doing so I want to keep everything as simple as possible.

 

[krispykritter]

33 minutes ago, turbogrill said:

 

The 1.6 TPS is just a switch, not a potentiometer. 

 

I would need this adapter, https://www.flyinmiata.com/default/tps-upgrade.html

And this TPS https://www.ecstuning.com/b-genuine-bmw-parts/throttle-position-switch/13631721456/

 

It's an $150 extra and easy to install. But there might be a few other people that is going to copy what I am doing so I want to keep everything as simple as possible.

 

 

That's very strange.  In that case, I think I'd start with using mapDot and see if it provided acceptable performance before adding any extra parts/expense.  Also, this link https://www.msextra.com/forums/viewtopic.php?f=4&t=47697 from Matt Cramer says lots of miata owners run without TPS (I assume for the very reason you're asking about).  He does make the point that it's NICE to have for flood clearing and for tuning purposes - IE you can see how much throttle you had applied so helps you figure out what the rest of the log SHOULD be doing.

 

I've found accel tuning to be particularly difficult to get right on the contour.  It's not BAD per se, just not nearly as crisp as I'd like when idling and then stabbing the throttle.

 

Then again - how often do we go from idle to the floor at the track?

 

Edit: Misunderstood your 'no throttle modulation' to mean foot action rather than sensor behavior.

 

Edit edit: The internets say that the only difference between the 1.6L and 1.8L throttle bodies is the TPS is a potentiometer type on the 1.8L.  Why not just source a used 1.8L TB and use that?

Edited December 14, 2021 by krispykritter

[turbogrill]

5 hours ago, krispykritter said:

 

That's very strange.  In that case, I think I'd start with using mapDot and see if it provided acceptable performance before adding any extra parts/expense.  Also, this link https://www.msextra.com/forums/viewtopic.php?f=4&t=47697 from Matt Cramer says lots of miata owners run without TPS (I assume for the very reason you're asking about).  He does make the point that it's NICE to have for flood clearing and for tuning purposes - IE you can see how much throttle you had applied so helps you figure out what the rest of the log SHOULD be doing.

 

I've found accel tuning to be particularly difficult to get right on the contour.  It's not BAD per se, just not nearly as crisp as I'd like when idling and then stabbing the throttle.

 

Then again - how often do we go from idle to the floor at the track?

 

Edit: Misunderstood your 'no throttle modulation' to mean foot action rather than sensor behavior.

 

Edit edit: The internets say that the only difference between the 1.6L and 1.8L throttle bodies is the TPS is a potentiometer type on the 1.8L.  Why not just source a used 1.8L TB and use that?

 

Using a 1.8 seems much smarter, not sure why that is not the recommendation.

 

On a second thought, the TPS is good to have for logging purposes. Its good to have so I can call out people that lift in the fast turns.

 

[turbogrill]

I went a head and ordered the arduino based SpeedyEFI PnP.

 

Downside is that there is no CAN output so if you have a CAN based dash you wont be able to use that! But it has a serial port so you can use something like old tablet and BT dongle. (Essentially running Tunerstudio or Shadowdash as your dash).

 

However I might see if I can fit a CANBed (Arduino with MCP drivers) into the casing, the CANBed would just poll data  from one of the extra serial ports and transmit that over the real canbus. 

Edited December 15, 2021 by turbogrill

[mhr650]

Rotaries are similar to the early Miata with a partial TPS instead of a full rotary sensor. I machined an adapter to use a conventional TPS sensor, like you noted it is good for logging and tuning if nothing else.

 

It did end up biting me in very unusual circumstances though…racing at the 24hr one year with a cracked header the heat killed the TPS among other things. The rotary by its nature needs very little acc enrichment so the car continued to run and drive fine. The problem is the sensor failed at wide open throttle, so every pit stop when we went to restart the engine the Megasquirt saw 100% throttle during cranking, went into flood clear mode and shut off all fuel. If I had hooked up the laptop, I may have figured this out and solved the problem by just unplugging the sensor, but in the heat of battle I just sprayed brake cleaner down the intake until the car started and sent the drivers on their way.