[CorvairRon]

So I finally got the ignition system working and using a timing light looks like my timing
is within range.
I am using Tunner studio MS lite to program the speeduino.
The intake system is custom-built with 4 injectors with a Jeep throttle body. I have configured the throttle body
in the software but I am not sure the stepper idle control works correctly, I will be testing more once I get the engine running better.

The engine starts but soon as it gets a little warm it starts to backfire. If I just touch the throttle the engine misses and dies.I have been adding fuel with the AFR target table but still not getting rid of the backfire. I have looked high and low for some tuner studio settings that might help but I am in uncharted area I guess. I have been told the Corvair engine likes more fuel so my base line fuel ratio is 13.0 in hopes that I could get rid of the backfires, it does not .
I have also played with the Acceleration Enrichment and that did not seem to help. Maybe the backfire is not fuel-related but the timing seems to be within range. Any Ideas on the cure for the backfire / Throttle response?

[Rednaxs60]

A newbe myself even after 6 year into my project. Trigger angle should be spot on, in other words, you hold be able to dial the trigger angle, #1 TDC. Do this by setting the fixed timing setting to "0" degrees. Set the cranking timing to "0" as well. Disconnect the fuel pump, and fuel injectors as well. The calculated trigger angle is to get the eking timing in the ball park, to be dialled in with a timing light. Once the trigger angle is set, set the cranking degrees to "10". with the fixed timing of "0" degrees still set. Crank the engine, should show up as "10" degrees on the engine timing scale.

Backfiring, is it in the exhaust, or up through the air intake? What is the MAP reading when the engine backfires. I f the backfire is in the exhaust, too much fuel. What do the plugs look like?

I am a PSIG convert. You cannot do an initial tune using AFR readings. Fuel calibration is by calibrating the VE (fuel) table to achieve the lowest MAP reading possible with the best ignition timing. Let the engine temperature come to normal operating temp, then calibrate the idle VE (fuel) and spark tables to get the lowest MAP reading possible. You may find that once you give the engine what it wants , fuel and timing wise at the expected idle RPM, that it differs from what the OEM specs require. The AFR may be in the 13.0 range at idle.

Disable the O2 sensor during initial engine tuning. It will not help with the initial tune. Use the indicated AFR reading as a guide to assist you in calibrating the VE table cell values. This is not to say that you are tuning to the AFR table, it's to look at whether the engine is in a lean or rich fuel condition.

During the initial engine tune, pick an engine RPM, speed and transmission gear. Calibrate the VE table until you have the lowest MAP reading for this combination. Note the AFR reading for possible input into the AFR table. Repeat this for different engine load and RPM settings.

There are AFR ranges that are recommended for various engine load/RPM ranges. These are on-line. Have a look, use as a guide.

Engine timing is next. Once the VE table is calibrated, calibrate the spark table. Be careful and move in small increments. The closer the MAP reading is to atmospheric pressure, the less engine timing required. The further away from atmospheric pressure - a low MAP reading, the more ignition timing is required. Balancing act between fuel, spark to get the best engine operation, lowest MAP reading , and good fuel economy.

Disable Acceleration Enrichment (AE) during initial engine tuning. This is an advanced engine tuning function to be calibrated after initial engine tuning.

The engine will let you know what it wants fuel and spark wise. The engine fuel requirement is what it needs, not what is thought to be needed. Disable all non-essential parameters.

This is a lot of information, but it seems you are going down the same rabbit hole I did at the start. The main tuning requirement once the engine is started, at normal operating temperature, is to calibrate the VE and spark tables to achieve the required engine idle speed with the lowest MAP reading possible. I mentioned that you may find the AFR reading to be in the 13.0 range.

With the engine idle settings done, next cold engine start you can look into calibrating the ASE and WUE settings to get a good initial engine start. When you do calibrate the ASE and WUE tables, make sure the amount of added fuel does not drive you out of the garage or work space. @PSIG mentioned to me that calibrating the ASE and WUE tables will be easier once the idle settings are dialled in.

Good luck. Cheers

[CorvairRon]

Wow thanks for all of the info there is a lot here. I will go back to the start and follow your input. I am using TPS on the engine
and the tps table is where the mixture is set, Correct? In the Engine constants, I set the AFR to 14.5 and played around with that number but It did not seem to do much.I will also go back to the Accel/ enrichment settings and turn them off as the exhaust is very black but the backfires are thru the Exhaust so I am guessing I am lean , a bit conflicting. Maybe the biggest thing is the Timing is wacked .. I only say that because I do not really get the response to timing changes I would expect.
10 degree change in the software I only see about 5 on the timing light. Weird.

Thanks Much

Ron

[LPG2CV]

1st off ... please post your tune.

As @rednaxs60 is saying. Stop trying to tune via AFR. You need to give the engine what it wants. This means you need to adjust the VE table to alter fuel. Consider AFR later when tuning.

We will know more when we see your tune.

[Rednaxs60]

Wow thanks for all of the info there is a lot here. I will go back to the start and follow your input. I am using TPS on the engine
and the tps table is where the mixture is set, Correct? In the Engine constants, I set the AFR to 14.5 and played around with that number but It did not seem to do much.I will also go back to the Accel/ enrichment settings and turn them off as the exhaust is very black but the backfires are thru the Exhaust so I am guessing I am lean , a bit conflicting. Maybe the biggest thing is the Timing is wacked .. I only say that because I do not really get the response to timing changes I would expect.
10 degree change in the software I only see about 5 on the timing light. Weird.

Thanks Much

Ron

Ron - good morning. The AFR table can be set to 14.7 for all cell values to start. The O2 sensor is disabled so the AFR table is not being used. As you tune the engine and the VE and spark tables start to be calibrated for correct values, note the AFR reading for a specific road trial test and populate the AFR table with that value. Continue this process for each AFR tablet cell value. You will have to fill in the cells between those that you have readings for, but this will be down the road.

Backfiring through the exhaust, too much fuel, engine is operating in a fuel rich condition. If the fuel condition was lean, there would not be fuel going into the exhaust to combust. Have to reduce the VE (fuel) table cell values.

The more knowledgeable such as @PSIG and @LPG2CV, want an engine tune. I'd get it started and idling well, then start doing engine tunes and data logging from engine start through to road trials. Recommend getting the licence for TS and MLV.

There is not a TPS table per se. The VE (fuel) table engine load axis changes to TPS from MAP, or MAP from TPS. Make sure the VE, spark and AFR tables reflect this. Make sure the engine load axis and RPM axis are the same settings for all three tables. If these are not the same, the ECU will not be able to correctly determine what the engine needs.

Engine timing can be a challenge, there are quite a few parameters that can affect what the timing is at any given time. Do the initial trigger angle timing again. Set fixed timing to "0" degrees and set crank advance angle to "0" degrees. Using the timing light, set the trigger angle to the setting that has the engine pointer indicate #1 TDC. Once this is done, the trigger angle should be set. Next, do not change the fixed angle setting. Change the crank advance angle to "10" degrees and spin the engine. The engine timing indicator should indicate "10" degrees of advanced timing.

Calibrating the VE (fuel) table will probably take more time using TPS for engine load than when using MAP. The spark plugs will be the best indicator of how much fuel is going into the engine. Plugs blackened, reduce the VE table cell values until the plugs come out a light brown colour to start. There's a bit more to reading a spark plug that will be advantageous as the engine tune progresses.

Next time you have the engine started, check the MAP reading. Determine if it is stable, may want to use MAP instead of TPS for engine load, something to consider.

When calibrating the VE (fuel) table cell values remember that the lower the number, it's a percentage of the amount of fuel required at atmospheric pressure and engine full power, the less fuel is injected into the engine. The higher the number, the more fuel is injected into the engine. This is opposite of the AFR readings. A high AFR reading say 15 to 17 AFR the leaner the engine fuelling. The lower the AFR number the richer the engine fuelling.

Set the AFR setting in Engine Constraints to 14.7 and leave it there, do not change. This value is used to calculate the Required Fuel I believe.

Most of what I am mentioning is from the school of hard knocks. I went down the rabbit hole and not to my advantage. Don't want to read that you did as well.

Keep posting. Good luck. Cheers

[CorvairRon]

How do I post my tune? Screen shots? I do not see an attach file option. Setting the Timing to zero seems to have helped.
Aslo been taking fuel out and with the AFR settings but now read I should be doing it with Ve table , Back to the car
Great help

Ron

[FiatDuino]

Attaching files

[Rednaxs60]

Newbe again. O2 sensor and AFR table. Enabling the O2 sensor and having an active AFR table during initial engine tuning is not advantageous. The O2 sensor reading during initial engine tuning is an indication of engine fuelling, rich or lean. You can use this reading to assist in calibrating the VE and spark tables similar to using the MAP indication.

You add/remove fuel using the VE table not the AFR table. The AFR table is calibrated after you have calibrated the VE and spark tables. The AFR table cell values are based on the engine operation at the various when the VE and spark tables values. Repetitious, but it is a rabbit hole that should not be used.

For example, if you are operating the engine on the highway at 3000 RPM and a TPS (in your case) of 25%, and the engine is operating well, but the AFR reading is indicating a rich fuel condition, you can change the VE table cell value to reduce the rich fuel condition, repeat as required until the AFR reading is in the range you would expect and the engine operation is quite good. Advance/retard the engine timing for this engine load/RPM setting as well to get the best engine performance and fuel economy as well.

Using the AFR reading in this manner is similar to reading the spark plugs or any other engine parameter. Fuel and ignition timing can affect how an engine parameter responds.

You advance the engine timing to lean out the air-fuel mixture, but primarily to accommodate the fuel burn rate. You retard ignition timing to richen the air-fuel mixture.

Fuel burn rate is similar to a fuel injector in that there is an initial fuel burn that brings the air-fuel mixture to full burn rate, takes time to get to full combustibility, then the fuel is combusted until the peak combustion pulse (PCP) is when the piston is between 10 to 20 degrees ATDC for optimal engine performance (power) and fuel economy.

Too much advance and the PCP is before the optimal ATDC point, and there is a loss of engine power. The PCP hits the piston too soon and there is not enough push from the PCP to drive the piston all the way to the bottom of the cylinder. Too little advance (timing retarded) and the PCP can be after the optimal ATDC point, and there is not enough time to fully combust the air-fuel mixture resulting in a loss of power, and fuel economy, exhaust valve opens. Blackened, soot covered plugs are an indication of this.

It's a back and forth issue until you get the best balance between VE and ignition timing for optimal engine performance and fuel economy. At this time as well as before, note the AFR reading and update the AFR table cell value to match keeping the O2 sensor disabled such that the AFR table does not influence the engine tune.

When the VE and spark tables are calibrated well or as well as you are going to do, and you have changed the AFR table cell values to match the engine tune, you can enable the O2 sensor so that the AFR table now influences the engine tune. When calibrating the AFR table you may have to interpolate between cells as it is not possible to hit every cell in the tables with a trial. I think this is where the table smoothing function comes into play, haven't got this far.

I am still learning how to read a data log, but the forum "experts" will give good feedback from your engine tunes and data logs.

Good luck.

[Rednaxs60]

Another thought on ignition timing. Have you disabled the Cold Advance feature, set all cells to "0". It has been mentioned that this is a feature that should not be used until your engine tune is well tuned.

[CorvairRon]

Update I got the car running Thank you . I have been tuning the car so far with the VE settings. I also have been
playing with the timing quite a bit. I can get the car to idle pretty well but it is a bit high. I think it has to do with the
idle control stepper. I guessed at the number of steps as I could not find any reliable info on the number of steps the motor uses. I have read anywhere from 80 to 200 step for full motion. Somewhere I read that it could have 280 steps.
so that is where it is set now. I plan on lowering the number to see if I get better control and lower Idle.

I did get the tuning file attached so If you have any more thoughts, I am open to all ideas. Keep in mind the tune I started
with only got the engine to start but I don't think it was anywhere close to right yet. The VE and the time sheets only went to 25 % full throttle kind of weird. SO very much a work in progress.
Much of the timing info I am using comes from the stock car manual. Fuel settings are a complete guess. Idle settings seem close but the rest are only ruff settings.

Fun side note I stripped the ring gear. The only option at that point was to pull the engine. Instead, I choose to tig weld
new teeth onto the ring gear. Now it turns over even better.

Ron