AEM FIC vs Xede; IAT and CLT timing control? - Miata Turbo Forum - Boost cars, acquire cats.

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Old 02-15-2009, 12:18 PM   #1
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Default AEM FIC vs Xede; IAT and CLT timing control?

I am trying to decide which piggyback to use on my '99 project. I have used full standalone before and don't want to do that with this car for various reasons. I'll put the big question at the front, rather than forcing everyone to read all my ramblings.

The turbo goonrus I talk with off line strongly suggest that being able to pull timing based on intake air temp and coolant temp is a near-necessity. From what I've been able to find, neither the Xede nor the AEM F/IC includes the capability to do this.

>>>Obviously, the stock ECU does it, but has anybody characterized it? How much under what conditions?

For those who care about the details of what I'm planning, here they are:
My plan is a WRX turbo on an Absurdflow-like manifold with no more than 12 psi. I already have most of the parts for a 2.5-in exhaust from the turbine discharge back, and that should be enough. I'll keep the stock MAF in the car. Unfortunately, 425cc RX-8 injectors seem like they may end up just a little on the small side, so I'm looking for some purple top 550s.

I like the AEM FIC because I have friends who work there, and I'd rather put some money in their pockets than a lot more money in Corky's. I also have an AEM UEGO setup, so that part is plug n play.

Checked out the AEM manual and downloaded the software. Even if it's not as sophisticated as the EMS software, it looks like it should be able to do what I need.

I like the AEM in principle because it is directly controlling the injectors, rather than lying to the ECU about load all the time and then having to correct other changes (timing) the ECU might make all over the map as a result.

It looks to me like the Xede may not be able to handle what I plan to need my engine management to do, based on the injectors and MAF increase. From its manual:

"The XEDE does have limitations. An interceptor unit cannot:
Increase rev limits
Adjust commanded idle speed
Easily increase speed limits
Easily change gear shift points
Facilitate injector changes greater than 30%"

425cc/min needs to turn down the pulsewidth by 43.5% in off-boost conditions, and my 550cc/min will need 56.3% reduction. On that basis, looks like this is not an option.

>>>Anyone have direct experience with the Xede doing a good job controlling 550s on a non-Mazdaspeed Miata?

The manual specifically cautions that if you're relying on the stock ECU to believe your filthy lies about lower MAF readings, it may also add timing or something else you don't want it to do. So you would have to tune 100 percent of the timing map, not just the in-boost portions.

Couldn't find anything in the Xede tuning guide about timing being modified in context of IAT or CLT. It looks so far like both systems rely on the stock ECU's adjustments for IAT and CLT. Has anyone gotten into the Xede far enough to know whether that's true?

It does kinda make sense that you could rely on a factory turbo car to have appropriate factors maintaining safe tuning when it gets hot, but it's less obvious that a naturally aspirated factory ECU would do the right thing when boost is involved. Hence my original main question at the top.
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