Tuning for fuel economy

[suprPHREAK]

OK, so the beauty of a turbocharged car, is that if you stay out of the boost, you can get generally good fuel economy, compared to other FI motors, or even some NA motors of the same power. However, manufacturers of turbo cars engineer it so that there is minimal lag, which means boost builds fast, and therefore so does the power, and the consumption of fuel. For example, the RA makes peak power around 3500rpm, which is where the motor feels most natural to shift.

Now, everyone here likes to tune their car for more power, or better power. This is understandable: its hella fun! But, what if you wanted to do the opposite, and tune for MAX mileage? The thought I have, would be to make a map where essentially the motor is making as little boost as possible, therefore as close to an NA engine as possible. I'm fully aware this would be a huge loss in HP, but that isnt the aim here.

Thoughts on this? I know its the opposite of most people's desire, but a reflash takes 60 seconds, so bringing back the excitement is easy to do. Other than obvious funitude, would there be any mechanical downsides to this?

Thanks to all in advance!

[harrytruman]

I've seen a couple different tuning companies offering to do custom tunes for improved fuel consumption, but I'm not sure right off about whether said tunes actually cause the vehicle to boost as differently as you're wanting. We'll have to see what they say about that.

I'm assuming you want to be able to load the custom fuel-efficiency map during the daily drive and load back to stock or a performance tune for your spirited drives? Hopefully the fuel tune won't be a permanent fix...

[Piper747]

I have found that the MiVEC map in the rom from GST has yielded better mileage. You could try just pasting those maps into your rom and see what you find.

[jkennedy293]

I think the fuel economy maps that are out there, just lean out the mixture more. Cobb Tuning has a fuel economy map that comes with a warning about performance driving with the map.

[billyboy1]

usually when you do a tune, you get a benefit of more mileage as the tune will invariable lean out the air fuel mixture. the stock maps run pretty rich from factory, so as to give a buffer

as to tuning even more for better mileage, have a chat with your tuner and do a custom tune, although if you want really decent fuel economy, these probably aren't the best cars to have bought

[boondoc]

I dunno much about this because i have not used it yet but this might help a little.

http://ralliartperformance.com/categ...1?categoryId=5

[Scott W.]

How about about try doing the shifting yourself? Stay in 6th gear as much as possible and drive like you are in slow motion (especially from a stop). Another thing would to remove as much weight as possible.

I do agree that a tune to get the car leaner would help, but keeping my warranty for the (3) years it's good is important too as repair costs would probably negate any fuel cost savings from an efficiency tune.

[suprPHREAK]

Thanks for the responses! I hve the GST map on there, but it is too soon to tell if it has given better mileage yet or not.

Harrytruman: that is the idea, a map I can switch to when i'm just putting around, and another when i want to have some (lots) of fun.

Scott W: contrary to popular belief, staying in top gear will NOT yeild better mileage. The amount of effort the engine has to put out has a great impact on how much fuel is used. Lugging the engine with foot to the floor would consume more fuel than letting it hit boost in a lower gear. I do tend to shift manually whenever possible, but its really nice to get lazy when driving home in traffic.

Boondoc: thanks for the link! I'm going to look more into that.

I am still wondering about the feasability of perhaps making a map that leaves the wastegate open so it just doesnt make boost. Any tuners (GST, AMS?) out there have comment on this? I understand it is a different way of thinking. A friend of mine had an old turbo supra, that had a boost controller in it. When in one mode, he was getting 350rwhp. In another, a lot less, but could get 600km to a tank. Can similar be done for us/

[GST Motorsports]

Originally Posted by jkennedy293

I think the fuel economy maps that are out there, just lean out the mixture more. Cobb Tuning has a fuel economy map that comes with a warning about performance driving with the map.

You cannot lean out the mixture while the car is in closed loop (idle/cruise/etc) because the ECU is using the front 02 to aim for stoich (14.7:1) all the time. Closed loop operation (non-WOT) is where most mileage gains are seen.

The mileage gains people are seeing are from other forces at play.

Originally Posted by suprPHREAK

I am still wondering about the feasability of perhaps making a map that leaves the wastegate open so it just doesnt make boost. Any tuners (GST, AMS?) out there have comment on this? I understand it is a different way of thinking. A friend of mine had an old turbo supra, that had a boost controller in it. When in one mode, he was getting 350rwhp. In another, a lot less, but could get 600km to a tank. Can similar be done for us/

Yes you could set the boost tables so you would only get wastegate boost at anything under 80%+ TPS. This could help not get in much boost when just driving around normal. You cannot go lower than wastegate boost however.

- Bryan

[shivaswrath]

what sort of mileage are you guys getting with the 6-spd SST tranny??

Considering the downgrade from my Evo VIII and wondering if I'm getting the complete picture. . .

[velocityhead]

I typically get 18-20 around town, but have seen as high as 28 on the highway.

[Ladogaboy]

Originally Posted by shivaswrath

what sort of mileage are you guys getting with the 6-spd SST tranny??

Considering the downgrade from my Evo VIII and wondering if I'm getting the complete picture. . .

It's been ranging 18-22 city and 24-28 highway. I'm sure a number of factors are coming into play.

[suprPHREAK]

the daily commute averages around 10L/100km

[majinfajita]

Originally Posted by suprPHREAK

the daily commute averages around 10L/100km

Same; that's about 23mpg for the non metric folks.
On the highway I can do about 8.3L/100km = 28mpg

[shivaswrath]

WOAH 28mpg!!!

My Commute is 99.99% highway (110 miles a day), and I'm lucky to get 25mpg. . .usually, around 23mpg. . .so 28mpg is sounds great!

Thx for the info, will now have to decide whether to sell VIII privately or trade it in. . .