Ok, noob corner. Bear with me.

How do you evaluate an existing tune for safety? Suppose you have a car with some basic mods and a custom PFC tune of unknown quality. Or you have a car with a tune of known quality but you change something that could affect it, like swapping an intercooler, or intake, or one of the exhaust pipes. Would you need different approaches in those two scenarios?

I know some will argue to just go get a retune, but I'm just curious about the fundamentals. If you have some basic gauges and maybe a datalogit, what would you need to do to evaluate a car's existing tune for safety? Can you do this without knowing all of the things you'd need to know to tune the car in the first place?

For instance, I'm thinking you could log some pulls for boost and AF, and if the numbers are good, maybe you're good? At least in the second situation, where you just changed the intake/exhaust flow? Or not?

 

Af is a good indicator, and understanding the timing map. Also important to monitor fuel pressure and understand where you are in relation to the limits of your system. Things go wrong at the limit.

 

Check EGTs and see if they're around the ballpark of what's considered acceptable..... at idle, steady state cruise and also peak values after WOT redline pulls. EGTs show more of a trend of what's going on, vs AFR which is more of a data point at that specific second. Best to check/log both IMO.

 

The thorough way?

Desktop analysis first. That means you pull up the map and look at what's in there and see how it compares to generally understood acceptable values. Look for something that's obviously screwed up, like red flags. Try to figure out the basic strategy that was used with the tune. Do a comparison between the preloaded Apexi map and whatever changes were made. See if you can justify each change (example: injector lag settings changed, on account of aftermarket injectors)

Then do an experimental check with wideband preferably on road. In the PFC tuning group I have a document which describes a series of tests to evaluate starting, idling, cruising, WOT, tip in, etc. and how tos for what parameters should be checked, how to make charts, that kind of thing.

Then you go to the dyno. I've also documented the basic procedures and guidelines for this.

 

I just thought, if you're not sure about a tune and you test it doing a wot run (street or dyno), isn't this risky? you could blow a motor, no?

 

Yes.

That is why I have a bunch of procedures which are more cautious and thorough than "Put car in 3rd gear. Drop the hammer. Look at the wideband and Cross your fingers."

 

Although I am running a haltech, how do I get in this group, and access your documentation?

 

As far as timing goes Racing Beat has a timing chart on their website that is a good reference.
Rotary Tech Tips: Ignition Timing

They say this:
"when turbocharging or supercharging a 2-rotor engine capable of 300+ horsepower, we recommend both leading and Trailing timing to be set at 10 to 12 degrees total advance at 6,000 rpm, regardless of the porting configuration.

 

I think it's really important to understand the context of that Racing Beat document. It's really meant for carburetors running on circuit racing. In those cases you need to set the basic timing at idle according to the value recommended in the chart for the application. Then the distributor changes timing based on engine speed (centrifugal weights) and load (lower load --> more timing , measured by engine manifold vacuum).



For older fuel injected rotaries (1984-1991) there is a base timing and the computer sets the final advance based on measured airflow. So in many cases it's not even a good idea to mess with the base timing, but you could if you wanted to.

I would mostly ignore that Racing Beat document if you have an FD. The base timing can't be adjusted because the crank angle sensor is fixed to the pulley like a modern car. Their point about 10-12 degrees at 6000rpm WOT on a boosted engine is only about half true. I wouldn't set the leading and trailing the same in that condition; that's considered very aggressive. Typically 12-15 degrees separation between leading and trailing is the conservative approach.

we have people with all sorts of different ECUs, even though Power FC is the majority. Once you understand how they work, overall tuning is the same idea, with some variations according to how the software works.

PM sent.