LNF Tuning - Boost Control & one random question on Cam tables

[carcar123]

LNF Boost control:

So I realize (or am learning) that LNF is more torque based...e.g. the ECU is doing what it can within some constraints to make a given torque based on input. I assume the ECU as it's trying to reach the requested TQ increases WGDC to try and get more boost (to get more airflow).

What limits boost?
- WGDC: If you limit the WGDC to say 95%, I assume when the ECU won't go beyond that as it tries to reach a target TQ, correct?
- Pressure Limit:
-- If the ECU is trying to get more airflow and it hits the "Pressure Limit", does it back off of WGDC?
-- Does it cut fuel or anything?
-- All other things being equal, if you take a tune and just lower the Pressure Limit, would the tune behave fairly well, only limiting boost, or will there be some big abrupt cut?
-- Is the proper way to tune this to limit the requested TQ so that you're not requesting more than would max out your boost?

Side question: Is it bad to allow WGDC to go up to 100%...is that bad for the solenoid? What should the max be?


Cam Tables: (see example below)

What does the top row mean? E.g. in the last column it's "120". 120 what? What does "Load %" mean and how do you go "120%"?


Intake Cam Angle - warm - stock.PNG

[gtstorey]

https://forum.hptuners.com/showthrea...357-LNF-Guides

https://forum.hptuners.com/showthrea...f-my-Write-Ups)

https://forum.hptuners.com/showthrea...l=1#post496771

[carcar123]

Thanks GT--good stuff. I have looked through some guides (LNF Bible, etc) before, but I'm still not quite sure the answers to the above. Will keep digging and looking as some of the links you gave I haven't read unless someone knows off the top of their head.

[gtstorey]

3rd link answers several of your questions directly.

Pressure Limit doesn't do anything other than cut requested airflow.

Although this is a "torque" based ECM. What you are really controlling is desired airflow. Your foot is asking for a "desired torque" and the ECM is translating that into an increase in airflow and spark changes.

I've never seen a good description of what the load headings are using for "units".

You are asking for a headache to try to understand this a to linear a fashion.

[gtstorey]

more required reading
https://forum.hptuners.com/showthrea...hlight=starter

[carcar123]

Thanks much. I?ll read through that 3rd link.

Yes I?m getting that picture that with the LNF it?s just not real simple?a lot of things interacting.

[gtstorey]

Usually the answer for any question on the LNF is "it depends".

[sbarisic]

As a general tuning answer, if you go to 95% wastegate duty cycle and you can't keep the boost pressure desired. It means your turbocharger is too small. Either too much backpressure, or the wastegate actuator is too weak. Fitting a harder spring in there just fixes the symptoms and there's a high chance you're going to blow the turbo.

The most you can do is as much free flowing exhaust after the turbo as you can, tightening the wastegate actuator rod (danger territory!!!!) or fitting a harder spring in the wastegate/fitting a different wastegate (also danger territory).