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brian_s30z

PRP trigger, Haltech Ecu, Base timing?

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Hello All,

I've tried searching but couldn't find the answer and on a forum (not related to ignition timing) I've tried asking, but still don't quite understand.

So I have a PRP trigger kit (Cam and Crank) on an Haltech Elite 2500 that I question how they both work together. If I were to go to the car and shine timing light to pulley, without hooking up my laptop to haltech, it would read 12~btdc. If I go into haltech and set ignition lock enabled (it's greyed out at 10degrees so enabling it locks at 10) and I aim timing light it matches at 10 degrees btdc which per my understanding and asking tuner is fine.

Per FSM base ignition timing is 20BTDC on a OEM CAS and ECU. So when does that figure not matter anymore? Is it because I have a standalone ECU and they are in Synch? 

Now onto the PRP trigger and other trigger kits, they have slots for adjustability but what are they for? OEM you would adjust CAS here to get you the desired ignition timing. I've seen Trigger kits where the bolt would be at the edge of each slot where mine is centered..

Thanks in advance. 

prp.JPG

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45 minutes ago, brian_s30z said:

Per FSM base ignition timing is 20BTDC on a OEM CAS and ECU. So when does that figure not matter anymore? Is it because I have a standalone ECU and they are in Synch?

What that means is, at idle, the engine should be running 20° of advance.

Your engine appears to be running 12° at idle, which presuming the synch is correct**, would be a bit retarded. Literally. Makes it sluggish and makes the idle exhaust temp a little hot, wasting fuel, blahdie blah.

**which it appears to be based on your observation of what everything says when it is locked up.

If the ECU is idling the engine at 12°, then that number should be easily found in the idle table/settings in the software, and you could change it to 15 or 20 and should see the result immediately.

 

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Look up adjusting tdc offset on the Haltech, you must get this correct before anything with trigger kits. You want to confirm 20 at light and on ECU when timing is locked.

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Generally speaking setting base timing can be done at whatever reference you have for timing marks, although you may not want to use TDC as a reference, especially if you have a missing tooth for TDC, accuracy can be worse at TDC if that is the case.

The reason why there’s adjustment present in the cam sensor is to prevent sensor triggers from overlapping. With no missing teeth if you have overlap with any of the crank teeth the ECU will lose sync. With a missing tooth you want to avoid overlap with the tooth after the missing tooth, that’s the reset for the ignition sync so it is important to not have the cam overlap.

At idle you can and should crank the timing to at least 20 degrees. Don’t set timing to MBT. It’s a balance between adding more timing to make the engine more responsive getting off idle/improving idle fuel consumption and leaving enough timing margin that you can ensure the ECU can adjust idle faster than the AAC valve can respond. 

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On 10/15/2020 at 8:40 PM, GTSBoy said:

What that means is, at idle, the engine should be running 20° of advance.

Your engine appears to be running 12° at idle, which presuming the synch is correct**, would be a bit retarded. Literally. Makes it sluggish and makes the idle exhaust temp a little hot, wasting fuel, blahdie blah.

**which it appears to be based on your observation of what everything says when it is locked up.

If the ECU is idling the engine at 12°, then that number should be easily found in the idle table/settings in the software, and you could change it to 15 or 20 and should see the result immediately.

 

Thank you sir. Would it be sluggish at all rev range? So to change it's within the software now since i no longer have CAS? Tuner verified it matched, but never checked at idle. "As long if it matches then you're ok" ...CAr is definitely sluggish.

 

On 10/15/2020 at 9:22 PM, BK said:

Look up adjusting tdc offset on the Haltech, you must get this correct before anything with trigger kits. You want to confirm 20 at light and on ECU when timing is locked.

They do match when timing is locked, but without it being locked I am at 12 degrees. I have seen a few haltech videos on how to set TDC, but still not comfortable doing it myself so I'm calling a shop and have them help over the phone while with software and car. 

 

16 hours ago, joshuaho96 said:

Generally speaking setting base timing can be done at whatever reference you have for timing marks, although you may not want to use TDC as a reference, especially if you have a missing tooth for TDC, accuracy can be worse at TDC if that is the case.

The reason why there’s adjustment present in the cam sensor is to prevent sensor triggers from overlapping. With no missing teeth if you have overlap with any of the crank teeth the ECU will lose sync. With a missing tooth you want to avoid overlap with the tooth after the missing tooth, that’s the reset for the ignition sync so it is important to not have the cam overlap.

At idle you can and should crank the timing to at least 20 degrees. Don’t set timing to MBT. It’s a balance between adding more timing to make the engine more responsive getting off idle/improving idle fuel consumption and leaving enough timing margin that you can ensure the ECU can adjust idle faster than the AAC valve can respond. 

Thank you for this information. What is "MBT"?

 

So to be sure. All Rb26 at idle should be 15-20Degrees no matter what ECU one is running, correct?

 

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Don't worry about idling at 12 making it feel sluggish, as soon as you touch the throttle you are on the main timing map.

 

 

Seems like a bit of confusion here, the cam trigger is just for the ecu to know what stroke the engine is on, its the crank trigger that is used for engine position.

 

 

Mbt is that timing value that creates the most engine torque. No one ever sets the car to idle at Mbt so not sure why it was mentioned.

 

 

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6 hours ago, brian_s30z said:

Thank you for this information. What is "MBT"?

 

So to be sure. All Rb26 at idle should be 15-20Degrees no matter what ECU one is running, correct?

 

MBT is maximum brake torque timing. It's the value that maximizes engine efficiency for that operating point, assuming you don't get limited by knock first.

A stock RB26 should idle warm around base timing with no accessories and nothing else going on. It will jump to more or less timing to control the idle.

5 hours ago, Ben C34 said:

Don't worry about idling at 12 making it feel sluggish, as soon as you touch the throttle you are on the main timing map.

Seems like a bit of confusion here, the cam trigger is just for the ecu to know what stroke the engine is on, its the crank trigger that is used for engine position.

Mbt is that timing value that creates the most engine torque. No one ever sets the car to idle at Mbt so not sure why it was mentioned.

The more timing you can dial in at idle the less air you need, the less air you need the more control authority the throttle has. The AAC valve is basically a controlled vacuum leak. You want to reduce it as much as possible so that the engine responds more to your pedal. There are limits to this though because idle requires the ECU to constantly adjust timing/airflow/fuel to keep it stabilized. If you add too much base timing and pull out too much air the ECU won't be able to compensate for sudden drops in engine RPM and the likelihood of a stall rises.

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1 hour ago, joshuaho96 said:

MBT is maximum brake torque timing. It's the value that maximizes engine efficiency for that operating point, assuming you don't get limited by knock first.

A stock RB26 should idle warm around base timing with no accessories and nothing else going on. It will jump to more or less timing to control the idle.

The more timing you can dial in at idle the less air you need, the less air you need the more control authority the throttle has. The AAC valve is basically a controlled vacuum leak. You want to reduce it as much as possible so that the engine responds more to your pedal. There are limits to this though because idle requires the ECU to constantly adjust timing/airflow/fuel to keep it stabilized. If you add too much base timing and pull out too much air the ECU won't be able to compensate for sudden drops in engine RPM and the likelihood of a stall rises.

Regardless of aac the engine will always respond to throttle the same, not sure what you are on about here. No way will you notice a difference.

 

 

 

I said when you touch the throttle you are onto the main timing map, doesn't matter if the air is all coming throigh the butterflies or some sneaking in via aac, the air is going into the engine and the spark is determined by main timing map...

Idling at 12 is fine, so long as timing gun shows what ecu thinks all is good and nothing needs changing.  No one gives a shit about rbb26 idle fuel economy.

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9 minutes ago, Ben C34 said:

Regardless of aac the engine will always respond to throttle the same, not sure what you are on about here. No way will you notice a difference.

 

 

 

I said when you touch the throttle you are onto the main timing map, doesn't matter if the air is all coming throigh the butterflies or some sneaking in via aac, the air is going into the engine and the spark is determined by main timing map...

Idling at 12 is fine, so long as timing gun shows what ecu thinks all is good and nothing needs changing.  No one gives a shit about rbb26 idle fuel economy.

You should try it for yourself, the difference in linearity and throttle response is noticeable. If you need 5 g/sec AAC bypass air to idle and you crack open the throttle, the difference is very noticeable compared to if you were to get it down to 1.5 g/sec. I've had subtle vacuum leaks happen before and the engine won't respond nearly as much to the throttle until it's fixed even though timing/fueling was all in a good state and the tune was speed density. 

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Why would the engine respond more "idling with less air and more timing" vs "idling with more air and less timing" ?

I think it's because vacuum is higher with "more timing and less air"?

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On 10/28/2020 at 2:43 AM, joz said:

Why would the engine respond more "idling with less air and more timing" vs "idling with more air and less timing" ?

I think it's because vacuum is higher with "more timing and less air"?

It's a matter of proportion. "vacuum is higher" as an explanation suggests that the tail wags the dog. If you need less air to idle, then when you crack open the throttle the air provided by the throttle has a larger proportion compared to the AAC bypass air.

Suppose you need 1.5g/s to idle with 30 degrees of timing at idle, but 6g/s to idle with 10 degrees. If you crack open the throttle to get 20g/s of airflow then the engine will suddenly receive 13.3x more air in the first case, but only 3.3x more air in the second case. The difference in engine response to 3.3x more air is quite sluggish compared to 13.3x more air. Important thing to remember is that you need, need to have enough reserve torque to control idle speed.

Adaptronic has published a video talking about this issue, which maps with what I've experienced with my tuning experiments: 

 

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Thanks for sharing. Yes I understand that.

But I think what we want to know is what is the use of this "throttle response" that you speak of?

Whether you starve the engine and idle at 20 deg or with more air idle at 10 deg, when you drive off normally they are both going to have the same amount of air and timing.

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Pretty much. No one is driving from idle to WOT

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1 hour ago, joz said:

Thanks for sharing. Yes I understand that.

But I think what we want to know is what is the use of this "throttle response" that you speak of?

Whether you starve the engine and idle at 20 deg or with more air idle at 10 deg, when you drive off normally they are both going to have the same amount of air and timing.

The point is the transient response. There is a transition period between idle air + timing and the new mass flow rate + timing. Lower airflow at idle makes the engine tend to respond more in both directions. Additional loads like AC compressors can cause the engine to stall, adding more air will tend to make the engine want to race up. More air means transients are smoothed out more.

I'm not saying that we should all go out and change base timing to 30+ degrees on our engines, base timing for idle is often set where it is to ensure that the engine won't stall. What's important is understanding the trade-offs between setting advanced/retarded base timing and whether the assumptions the OEM uses to set base timing are still true for your setup.

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