Why is a Stage 1 tune better than stock?

[Zinnober]

I have a 2019 GT86 automatic, which I drive mostly in manual mode via the pedal shifters. The only thing I've changed so far is to put on some better tires and (Firehawk INDY 500) and install the OFT Stage 1 tune -- ZA1JS00D (MY2019 US 6AT); v4.03

I did experience a noticeable improvement in how the car pulls throughout the torque dip and people have reported the same in this forum. Also the throttle feels better, more linear (earlier it seemed it was already at full throttle pressed 40% down, and the last 60% did nothing).

Now, I wonder: Why doesn't Toyota/Subaru just tune the car like this from stock? They probably put a lot more time, money, and effort into that engine than the guy who created these OFT files.

1. Are there some drawbacks with the OFT tune, like emissions, gas mileage, reliability?

2. Where can I find a summary of the differences between the v4 tune, v2, and stock? Between the manual and the automatic tune? Do I need to go through all the tables in RomRaider or is there some changelog?

[Sur]

All cars can be tuned by manufacturers instead of aftermarket, but simply put, they produce the vehicle for the general time and cost factored into the production of the vehicle. If they took the time to dial in all the vehicles on their production line Beyond the stock output, it would cost more and then they would have to sell it for more to the consumer. Tuning a vehicle can push the motor and it’s components beyond the manufactures suggested values, therefore causing mechanical failure to said components. So they produce the vehicle in their ideal safe values for the region they are selling them. That’s my understanding of it all.

1. Mileage, yes, you are running more rich so you are burning more fuel. So you will have less mpg. Emissions shouldn’t be an issue until you add things like headers and exhaust. And a tune can solve that if you get a CEL. And reliability is always a possibility when tuning.

2. I think you would have to look at rom raider for this information. You could post your log files in the tuning section of the forum and ask for some help there. But generally I would think loading up rom raider and comparing would be the best way to go since the tunes are specific to your vehicle ID.

[NLSP]

Originally Posted by Zinnober

Now, I wonder: Why doesn't Toyota/Subaru just tune the car like this from stock? They probably put a lot more time, money, and effort into that engine than the guy who created these OFT files.

It's a car sold worldwide, so they have to consider that not all fuel quality around the world is the same, so it makes sense for them to prioritize flexibility and reliability over power...and probably take into consideration the not-so-smart people that fill this car with the cheapest/lowest octane fuel.

[steve99]

Tunes are better as almost all wont conply with emmissions standards


The tuner can jist optimise tune for power and torque regardless of emmissions


Main difderences are fueling , the stock tune runs quite rich over 5000 this costs power but does help with cat converter life as it keeps cat temps down


Low to mod range cam vvt angle changes optimise power and torque likely at expence of complying with emmissions standards also fueling changes


Ignitipn timing is often optimised for local fuel or generally top quality fuel as mpst people that run tunes will run quality fuel where manufacturer needs to carer for people who run low quality fuel

[JohnH]

also, the stock tune will pull timing due to knock in large chunks, in large areas whereas good tunes will only pull what it needs.

or so I understand?

[Zinnober]

Thanks for all the great answers!

One thing that wasn't mentioned is the rattle around 3500rpm that I started noticing. It is a bit annoying and I can see why the stock tune would sacrifice some power to avoid that rattling.

I read an UEL header should get rid of it, and would be the logical next step for me anyways?

[ayau]

In short, OEM tunes are very difficult as you have 20 different goals you're trying to achieve. This is why you need proper university training to get a job at the OEM level.

Aftermarket tuning is just optimizing for power with a limited set of variables to account for.

This video explains aftermarket tuning vs OEM level tuning:

[CSG Mike]

I would say an aftermarket tune that only optimizes for power is rather poor, but often times, that's all a customer wants to pay for!

[churchx]

No-no-no, some customers want to pay for aftermarket tune, that does pops & bangs. It's more important, then anything else

[Ohio Enthusiast]

Originally Posted by CSG Mike

I would say an aftermarket tune that only optimizes for power is rather poor, but often times, that's all a customer wants to pay for!

Perhaps not just power, but an aftermarket tuner is certainly less constrained than an OEM with regard to emissions, fuel economy, reliability and having the tune work well on a wide tolerance of cars, fuels and conditions. It's kinda like asking why a restaurant meal is typically better that catering.
But yeah, customers typically want power and don't really care about anything else, until their engine blows up...