Boost Controller with Tune

[SydCrazi]

Howdy all,

 

I've received different responses from different people, so thought I'd ask the question here:

 

You get your car tuned. You have an electronic boost controller installed. Now obviously going more boost than tuned is bad. But say you use that controller to lower boost. It's all about afr ratio I'm led to believe. So if you lower boost with controller, is fuel just pumping in as per tune, or does it all symmetrically lower via ecu correction or whatever? Thus the lower boost setting would be more fuel efficient as less fuel required.

[Puffwagon]

It depends. With all the mods that people do, your question is too broad to be answered without highlighting all the variables, and ain't nobody got time for that.

 

If you want to run lower boost to save fuel, with a properly tuned car, you just push the accelerator less.

 

We will need more info about the specific vehicle in question. If you are just asking to learn more info then that is a different kettle of fish.

[SydCrazi]

Well the mods are not important. If you have modified your car a lot or a little, the foundational principles remain the same as per my question.. For arguments sake, high flow cat, intercooler, injectors etc.. But the foundational question remains? (I've had two tunes on my xcal, one high one low boost, I could get twice the distance on low boost tune, even if I tried hard to not use much throttle on high boost... So.. This brings me to my original question) 

[Puffwagon]

5 minutes ago, SydCrazi said:

Well the mods are not important.

 

Yes they are mate. Some folks don't use a stock pcm. Different ecu's work differently and while a stock pcm will do most of what you said, you couldn't assume that you'd be ok to do that to an aftermarket ecu that has only been tuned for one boost level.

 

Reading between the lines, I can tell you that if you are seeing economy differences between tunes with the same driving style then there is an issue with one of the tunes. You should return nearly identical economy on both tunes until you get into it then the high boost tune will use more.

 

There is a chance that the high boost tune has wack cam timing to make it go a bit better at the cost of economy. You'll have to have a look at the tunes and compare them.

[SydCrazi]

OK I'm willing to learn. I had it in mind it didn't matter as foundationally the rules are constant.. Stock ecu, xcal x4, mods as I listed, then all I wanted to know was if I turned boost down from the tuned boost, would the computer know, and compensate, or if you want to run 7psi as opposed to 12psi you'd need a different tune on your xcal for the lower boost... Or just lower it with a controller.. I do know mathematically you'll use less fuel if you have less kW.. So lower boost = less kW which = less fuel.. But I don't know if just turning it down if everything else just works.. 

[Puffwagon]

23 minutes ago, SydCrazi said:

But I don't know if just turning it down if everything else just works.. 

 

In short, yes mostly. The car might not be optimally tuned if you turn the boost down but it's safe to do so. It's going the other way that can cause issues that might hurt your motor.

 

You might get error codes/engine light if you disconnect the cars boost controller and run a bleed valve/ebc as it might be in a constant underboost condition. There other variables in play here and different methods of tuning with the factory boost controller. If it was tuned with an ebc initially then this more than likely won't happen.

 

Think about this though...if the tune is using more fuel just cruising around or at low boost etc then it will still use the same amount of fuel if you lower the max boost via a controller as this will have no bearing on the actual tune itself.

[SydCrazi]

OK I think I get it. Lowering boost does f#ck all, as it is tuned for 12psi, so turning it down via an aftermarket electronic boost controller won't do anything but lower boost, but fuel would still be pumping in as if it was tuned for 12psi and you turned it down to 7psi the level of the wastegate actuator spring setting.. So nothing happens except less power, no improved economy, you run rich.. So what's the point of a boost controller then, no good for xcal 4s, need some computer to go with it that changes fuel maps as you change boost? 

[Puffwagon]

14 minutes ago, SydCrazi said:

fuel would still be pumping in as if it was tuned for 12psi and you turned it down to 7psi

That's incorrect.

 

The stock pcm will run less fuel if you turn the boost down and more if you turn it up.

[Puffwagon]

Lemme rephrase that.

 

Changing the set point on an aftermarket boost controller does nothing to the tune. Simply put, the pcm changes the fuelling according the the engine vacuum/pressure and other variables.

 

2 hours ago, SydCrazi said:

what's the point of a boost controller then

 

There is no point having an aftermarket boost controller on a factory turbo falcon in 99.99% of cases.

[SydCrazi]

Thanks @Puffwagon