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powerc tune - are these results safe/ok ?

paulr33

By paulr33,
in Engines & Forced Induction

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Sydneykid Grand Master

Sydneykid

Posted
Posted

My 20 cents worth....

Once the boost is stable it is relatively easy to predict the fuel requirements using the throttle angle sensor and the engine rpm as reference points, even road speed and boost pressure can be referenced. This is how we tune a Skyline with a Motec (no AFM's). Note that it is a more labourious task than tuning off the AFM, and you do tend to build in a bit of conservatism.

There comes a point where the AFM's are maxed out so early that boost is not yet stable, that is when you need to reach for larger AFM's. On RB25's for example you can get to the stage where the standard AFM is showing 5.1 volts at 4,000 rpm, then its time for an upgrade to a Z32 or Q45 AFM. But there is no real reason to upgrade when you get to 5.1 volts at 6,500 rpm, the remaining rpm to rev limit are very predictable via the other inputs.

We have changed a number of RB25 AFM's as soon as they get to 5.1 volts, but they never pick up any horsepower when the 5.1 volts is reached high in the rpm range. I note that MD did a similar test recently for Z/HPI, and found exactly the same.

This is my experiences, others may have different experiences:cheers:

GunMetalR33 Mentor

GunMetalR33

Posted
Posted
You should be on TV with talent like that - you're talking out of your arse.

There is no way in hell anyone could do what you propose. It is impossible to control how much fuel is required for the air that is being ingested without accurately measuring it - if you exceed the voltage ceiling for the AFM's, the tuner has no control over anything at and past that point.

As load increase, air ingestion does, so what happens if you tune like you propose and the guy is driving up a steep hill in 5th gear? There is no way in hell the fuel system could put enough fuel (especially in this case with injectors so close to their limit).

Infact, the Power FC is usually set to dump fuel when it detects the AFM voltage ceiling; just as it does when it detects what it believes to be knock (>= 60).

Mario.

[edit:  spelling]

Mate take it easy :D

If you read what I said then you would have noticed that I mentioned that this would only work on a standard turbo setup meaning that 14 psi would be the maxium boost being run. I dont know about your car but my AFM maxes out at about 14 psi so your only guessing a couple of load points at most. I am not tring to imply that this is the best solution, only that it was a way around tuning the standard turbo setup when your AFM "occasionally" Maxes out...

  • 2 weeks later...
Lithium Grand Master

Lithium

Posted
Posted

What happens if the owner doesn't understand this and decides to change to a higher flowing air filter? A really cold day? Maybe a change in boost level? Whats the point in even having a AFM if you're going to do this kind of tuning?

GunMetalR33 Mentor

GunMetalR33

Posted
Posted

I think getting a Z32 AFM is obviously the best solution but if you cant afford one at the time then this might be a good tempory fix... Or you could just run less boost and not max out your standard AFM :D

I have my car tuned in this way becuase I run about 14psi and only have a rb25det AFM and I dont have any issues, keeping in mind that I dont change anything setup wise without a dyno run (as Lithium pointed out)...

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