Monday, March 9, 2009

Power Plans, and MPG

At this point our STI is pretty nicely set up in the handling department, what with the upgraded wheels and tires, Cusco coilovers, and Whiteline sway bars. And the car is looking pretty good, too. But the horsepower is still pretty close to stock -- the only power modification we've done is a Cobb AccessPort.

Part of the reason I haven't bolted a bunch of power-increasing parts on the car has to do with the engine failures we've witnessed among our customer base. (See my notes and pics below regarding that subject.) I confess I'm not very excited to think about having to pull the block out of the car to replace the pistons. Even if the likelihood of a failure is low, the expense (in both money and time) is pretty high.

Another contributing factor is that our service business has been growing and it's been a little hard to schedule work on our own car when we're full up with paying work. (That's not a bad problem to have!) The final factor is that like many of us considering the economic downturn, I'm a little leery of spending cash that I might need if the economic climate continues to worsen.

That said, I didn't buy this car to keep in bone-stock. The reason for having is to showcase what we sell and provide some first-hand insights about the parts and how they work. So here is our plan for power production on the car:

This should give a healthy amount of power (figure around 350 awhp on our Dynojet dyno) but still leave the car relatively civilized for daily-driver duties.

On a completely different note, I've been noticing that the STI's miles per gallon is still improving. I noticed this looking at me from the dash the other day...


Jacob said...

OMG how are you getting that mileage?? I've been reading this blog for a while, and thanks for it, I plan on picking up the new STI as soon as I can afford it, and this has been very helpful. If I lived anywhere near Virginia I would use you guys for mechanical work too. I do plan on purchasing from your web store though.

kts262 said...

Any tips on how to achieve 32.1 MPG?

My best has been 26.4 for a long trip, and as bad as 5.1mpg during a autocross driving school.

Mach V Dan said...

Okay, hyper-miling in your AWD Subaru. Here's my best tips:

- Put a couple of extra pounds of air in your tires.
- Short shift to keep revs low, but use a lot of throttle. Open throttle body is more efficient, since it reduces airflow restriction. You have to stay out of boost, though, because the car will richen the fuel mixture up once boost comes on.
- And perhaps the biggest one of all: Drafting. Even being as much as 100 feet behind a large vehicle can reduce your air drag a lot -- worth an 11% increase in mileage, according to Mythbusters! But...that's too close for safety, so I have to suggest you NOT drive that close.

Mach V Dan said...

I got to thinking about that MPG figure. I have new fuel injectors in the car. They're larger. That means smaller injector duty cycle. If the onboard computer is using IDC to calculate its mileage...that could explain the high number.

I'm going to have to look into this more.


kts262 said...

Very delayed comment but it does appear that gas mileage for the car is calculated by injector duty cycles. A friend with larger fuel injectors also noticed that the computer was reporting improved MPG after his larger injector install + tune when in reality his mileage was about the same or had dropped.