Engine Brake Tuning

[Lee350znb]

I'm currently using a plug-and-play ECU in my 350Z and have been exploring ways to tune the engine brake. While researching, I haven't come across much information regarding alternatives to fuel cut for this purpose. I'm curious if using ignition retard could be a viable option. Am I on the right track with this approach? Furthermore, I'm seeking guidance on the proper way to achieve the desired engine brake tuning. Cheers

[essb00]

You can set the high vacuum regions of your ignition table to retard, but it is not enough by itself to significantly reduce torque for effective engine braking if fuel not cut.

'Overrun Fuel Cut' settings also include the ignition retard. Check the PCLink help file for further information.

[Lee350znb]

5 hours ago, essb00 said:

You can set the high vacuum regions of your ignition table to retard, but it is not enough by itself to significantly reduce torque for effective engine braking if fuel not cut.

'Overrun Fuel Cut' settings also include the ignition retard. Check the PCLink help file for further information.

Thanks for your reply; I really appreciate it. I'm just curious if there's any way to make the engine brake adjustable on board. It appears that the overrun deactivation table is locked and cannot be modified directly. Additionally, I've noticed that many NA racing cars produce pops and bangs sounds while braking. People have been discussing whether this is harmful to the car. Is there any connection between ignition retard and engine braking in this context?

[Adamw]

Can you clarify what you are trying to achieve?  When we talk about engine braking control in a race car or motorcycle it is usually to prevent wheel slip during downshifts, that doesnt sound like what you are querying here? 

[Lee350znb]

2 hours ago, Adamw said:

Can you clarify what you are trying to achieve?  When we talk about engine braking control in a race car or motorcycle it is usually to prevent wheel slip during downshifts, that doesnt sound like what you are querying here? 

So basically, my goal is to achieve maximum engine braking with improved throttle response. However, I've noticed that after installing the Link ECU, the throttle response has become noticeably slower, particularly after braking. Currently, I'm utilizing overrun fuel cut for engine braking, and I suspect that it might be the cause of this issue.

I'm wondering if there are alternative methods to achieve engine braking without compromising throttle response. Additionally, I'm curious if it's possible to adjust the level of engine braking. My intention is to avoid wheel slip during braking, as I'm currently experiencing more rear lockup.

[Adamw]

Fuel cut is done for fuel economy and emissions reasons, not for engine braking.  The largest factors are generally throttle opening and valve timing, for maximum braking effect you effectively want maximum pumping losses.  If you are not cutting fuel then you can also vary braking effect with spark timing. 

Over-run fuel cut should not have a significant impact on throttle response when tuned correctly, all OEM's for the last 30years have used it.   

 

[Lee350znb]

14 hours ago, Adamw said:

Fuel cut is done for fuel economy and emissions reasons, not for engine braking.  The largest factors are generally throttle opening and valve timing, for maximum braking effect you effectively want maximum pumping losses.  If you are not cutting fuel then you can also vary braking effect with spark timing. 

Over-run fuel cut should not have a significant impact on throttle response when tuned correctly, all OEM's for the last 30years have used it.   

 

Thanks, man. That makes more sense. For the throttle opening, should I modify the throttle target table? And for the ignition timing, can I use the anti-lag function to achieve it instead of modifying the ignition table? Also, I'm a bit confused about what the VVT numbers represent at the moment.

[Lee350znb]

16 hours ago, Adamw said:

Fuel cut is done for fuel economy and emissions reasons, not for engine braking.  The largest factors are generally throttle opening and valve timing, for maximum braking effect you effectively want maximum pumping losses.  If you are not cutting fuel then you can also vary braking effect with spark timing. 

Over-run fuel cut should not have a significant impact on throttle response when tuned correctly, all OEM's for the last 30years have used it.   

Also, is there any way to improve throttle response?

[Vaughan]

7 hours ago, Lee350znb said:

Also, is there any way to improve throttle response?

Throttle response is a combination of E-Throttle PID tuning and fuel tuning, the E-Throttle PID tuning controls how fast and accurately the throttle blade moves and the fuel tuning controls how fast the ECU adds extra fuel in to account for the extra air that has suddenly been introduced.

In terms of E-Throttle tuning a good way to test response is to put a big step change in the target table and take a log while going back and forth over the step change while the engine is running and then look at the delay between the E-Throttle Target value changing and the TPS (Main) value changing.

Fueling transients can be hard to check using the wideband as it is a very sudden change so get the throttle tuned first and then do the fueling by feel after that.

 

Note your E-Throttle Max and Min DC clamps limit how much power can be applied to the E-Throttle motor.

[Adamw]

11 hours ago, Lee350znb said:

I'm a bit confused about what the VVT numbers represent at the moment.

Degrees of advance from the home position.  

[Lee350znb]

3 hours ago, Vaughan said:

Throttle response is a combination of E-Throttle PID tuning and fuel tuning, the E-Throttle PID tuning controls how fast and accurately the throttle blade moves and the fuel tuning controls how fast the ECU adds extra fuel in to account for the extra air that has suddenly been introduced.

In terms of E-Throttle tuning a good way to test response is to put a big step change in the target table and take a log while going back and forth over the step change while the engine is running and then look at the delay between the E-Throttle Target value changing and the TPS (Main) value changing.

Fueling transients can be hard to check using the wideband as it is a very sudden change so get the throttle tuned first and then do the fueling by feel after that.

 

Note your E-Throttle Max and Min DC clamps limit how much power can be applied to the E-Throttle motor.

Thanks man, appreciate it.

My E-Throttle setup seems like is locked tho. Does it means I have to connect to the ecu to access changes or I can't modify it at all?

[Vaughan]

Change E-Throttle Mode from 'ON' to 'ON - Setup' to change values, you can still alter the target table without changing the mode though

[Lee350znb]

1 hour ago, Adamw said:

Degrees of advance from the home position.  

Cheers

[Lee350znb]

22 minutes ago, Vaughan said:

Change E-Throttle Mode from 'ON' to 'ON - Setup' to change values, you can still alter the target table without changing the mode though

Cheers man

[Timboj]

@Adamw I've found the throttle response on my 350 to be a little lackluster as well. I took a look at a recent log and to my untrained eyes, the target vs TPS main generally looks pretty good. I picked a section that had some variance in the delta. Would you say this would benefit from any further PID tuning or about as close as it will get (and make any real difference):

[Adamw]

Your throttle tracking looks ok to me but your target looks pretty tame, that could possibly make it feel pretty lazy.  For example at the time mark -3:12 in your pic above we cant see the actual APS as it is off the screen, but the axis goes to 23% so we can say you have more than 23% pedal commanded, but your TPS target is only 12.5%.  

[Hodgdon Extreme]

@Timboj

Adam makes a great point. Try a 1:1 E-throttle target table like the OP posted above - where 10% APS = 10% TPS, 50% APS = 50% TPS, and so on....

I'd recommend switching to a simple 2D target table until you really feel like going off into the weeds dialing in the exact throttle feel you are after.

[Timboj]

Yeah fair point. I had kept it much lower initially to give some finer tuning with the pedal at lower speed/throttle, but 1:1 is probably a much better place to start and then work back.

[Timboj]

Obvious answer helped, thanks guys. Should've started there. Low throttle is way too toey so I'll scale it back a touch but not as much as it was previously.