My Goal of 30mpg and 300hp

This will be my thread of open discussion for ideas and my plans for achieving 30mpg at freeway cruise and 300hp.

 

Goals:

The fuel economy is more important than power. The car has plenty stock for what we want, but more power is fun and smiles per mile are important too.

 

Quiet

 

I want this car to be silent as stock

 

Basically this:

 

Reliable

 

This car is a daily driver, nothing i will perform will hurt reliability in any way if i can help it.

 

 

 

-----------------------------------------------------------------------------------

Plan of attack

 

 

Engine

 

257 Shortblock,

WPC treated:

- King rod and main bearings

- Stock pistons

B25 Heads with polished ports

Legacy Outback cams

Stainless steel valves

VF52

STi oil pump

 

Bolt on performance

 

Catted divorced downpipe ( Havent decided on brand)

grimmspeed ceramic coated up pipe

stock exhaust ( to keep noise down)

Stock air box with perrin inlet

Phenolic spacers ( height to be decided)

K&N drop in filter with OE snorkel

LOTS OF HEAT MANAGEMENT

• PTP Lava Turbo Blanket
  
• Perrin Turbo heat shield
  
• Thermal products Heat tape ( intercooler tanks)
  
• Thermal products fuel hose sleeving
  
• Ceramic coat downpipe (DIY)
  
• Thermal products Lava Ti Exhaust wrap over flange and downpipe
  
• Paint intercooler with black thermal coat ( brand undecided)
  
• Radiator cooling pannel
  

 

Valve body modification

Flat panel underside of body with rear diffuser

Light weight wheels and tires ( undecided)

 

 

*** will edit more later

 

 

 

Please discuss you ideas and thoughts. I would love experience and ideas, all are appreciated!

You not gonna get close to 30mpg @ ANY Horsepower unless you put a really short F/R axle ratio in there. That would be cost inhibitive if not impossible to procure. be lucky to get 25mpg @ 300HP IF you stay out of boost and hyper milage drive it. If you do achieve both goals, call time life books so they can do a spread on your car.

Oh im going to try thats for sure lol

 

and im not saying average 30mpg, thats just not possible, but cruise control set while coasting 30mpg. Per say long freeway road trip. Im expecting 22-24 average hypermile driving. 15 driving like a hooligan.

Ive had 27mpg purely on highway miles on my stock wagon before.

 

If you wan't to get anything over 25 my advice apart from the obvious "stay out of boost" is don't put anything on the roof!

Yeah ill take the roof cross bars off when doing extended freeway trips, back on for roof basket off roady stuff

as well per covertrussians thread he was able to achieve 30.3 MPG average during a road trip. Thats more than what im asking for. if i could get a combined 25 id be more than pleased.

 

http://legacygt.com/forums/showthread.php/tuning-fuel-economy-230552.html?t=230552&highlight=FUEL+MILEAGE

You could get a mileage tune and a power tune.

True, im all for that. It would be really trick to switch maps when put into sport mode ;]

I drove one time 155 miles on the highway and achived 30 mpg, but that was being out of boost and drafting simi's most of the way. It was a goal to see if the car can do it, and the car is at stage 1.

 

It's going to be tough to get these cars to do consistant 30 mpg on the highway. You'll definitly will need to tune down the turbo and sacrifice power. You will not be able to do it with 300whp, unless you convert it into a hybrid.

Ain't gonna happen unless Hilary gets elected and Trump is VP.

lmao and yes i know ill have sacrificed power but with all intentions aiming at fuel economy and see how much power i can pull out of it in the process

300whp and mid to upper 20's are possible, I'd say 25-27mpg. My wagon will get 26+ on some drives. But a lot of things have to be right. When I gas up in Ludlow VT drive 23 miles on rt103 to rt91, the speed for most of that 55mph. When I check the dash for mpg it will normally be high 20's may be 30mpg.

 

Even on the highway at 65-68mph it will still get 26+ on the dash. If the ski mountain opens for skiing next weekend, I'll be able to check the numbers. I do that drive every winter weekend.

 

I normally can't drive that slow for that long on that trip. I can do those speeds on the 32 mile, DD to work, sometimes slower (not in any hurry to get there). The dash will read high 25's to low 26mpg. But if I take the backroads home, the car is to much fun to keep it out of boost.

 

Over all I average 23-24mpg on the DD. I look for reasons not to take the highway home after work.

 

IMO your trying to do mpg with the wrong platform.

 

I know everyone is different, I just enjoy driving my car, I don't worry about the mpg that much. Yea I think about it a lot, but 21psi of boost is so awesome.

Getting 30mpg is actually not that hard on stockish LGT's. They are very aerodynamic and even though the 5 speed is revving way too high at 70mph, I still get 29-31mpg going 70mph on round trip drives when it's warm out.

 

Redoing the tune is what helped me the most, specifically increasing AVCS 10* from 0* at highway speeds, running 45* cruise timing on base map, and Setting WGDC tables not to be in boost below 30% TPS.

 

I know everyone is different, I just enjoy driving my car, I don't worry about the mpg that much. Yea I think about it a lot, but 21psi of boost is so awesome.

 

I enjoy driving my car too, but when I'm on the highway I'm trying to get my family from point A to point B safely and without speeding tickets. It's fun for me to see what my new mods/tune can get me gas mileage wise. Same reason people shoot for 300whp or any other xyzWHP numbers.

I got ~28.5 mpg on a 55 mile drive (100% freeway) @ 70 mph with my wife and baby in the car three weeks ago. Outside temp was around 70F, and almost no wind.

The car is stage 2.

 

I did hit 30 mpg once with my stage 2.5 obxt. Average speed was more like 55 mph though. (that was only that one time though ).

A week after I got the car, I drove it from Schenectady to Rochester, then to Toronto, and back (pretty much I-90 the whole way). On the way back I managed to average 29mpg, stock tune going around 70mph.

 

The hardest thing is keeping it out of boost due to a combination of both the VF40 being a tiny turbo that spools like yesterday, and self-control. The car would probably be easier to drive efficiently with a larger turbo, actually. I was catching it making a few PSI going up hills, watching the instant MPG readout (didn't have my AP yet) and lifting when it would start to spool up/tank the fuel economy. Just letting the cruise control do its thing often resulted in unnecessary boost and the accompanying hit to fuel economy.

 

Assuming I get it back together tomorrow, I'll be driving it to Montreal on friday, and might try out the Cobb Economy tune. Shouldn't be too hard to get high 20's knocking on 30mpg heading up the northway.

 

Or I could take my GF's Honda Fit Sport, and achieve 39mpg while desperately wishing for another 60hp to not die in highway traffic.

My suggestions would be Equal length header. Get the header/up/turbo hotside and downpipe ceramic coated. get a grimmspeed TMIC. maddad or nameless catted downpipe. A blouch 18gxt-r, tomioka racing billet 18g(i have this one) or similarly sized as the trans sucks a lot of power.

I get 25mpg with my setup but i have 6spd gearing on my side.

Get the cylinder bores WPC treated if you can afford it. Your basically trying to make the engine as efficient as possible.

Slightly off topic but I watched a video yesterday of a guy who achieved around 40mpg while cruising at 55mph with his 2015 wrx! Unbelievable. At 70-75mph, he consistently achieves 33mpg. And he is not trying to hypermile or anything. Just use the cruise control. He is stock btw.

I average 26+ over a year of driving, winter/summer gas, 100/28 temp, ~half hour commute on highway/city 60/40 split. 30 wouldn't be hard.

 

As has been said, get elh, a specb 6 speed, forged/light wheels and keep her maintenance up and i'm sure you'd be fine. Oh and tune for economy on the low end and power up top. Easy peasy.

 

Oh, and learn to drive. Alot of good mpg is how you drive. Could also block the lower grill and make a full bellypan. Maybe even a mild front dam too.

 

And i'd forget all the engine stuff until your engine granades. Not necessary for 30mpg, maybe for a goal of 36+. And tmic coating is waste. Raw aluminum is best, mostly for forward motion. And get a catless oem up. Metal heatshields are better than moat coating and wrap, keeps wind and water off pipe and insulates with airgap FTW.

 

Sent from my XT1028

Getting 30mpg is actually not that hard on stockish LGT's. They are very aerodynamic and even though the 5 speed is revving way too high at 70mph, I still get 29-31mpg going 70mph on round trip drives when it's warm out.

 

Redoing the tune is what helped me the most, specifically increasing AVCS 10* from 0* at highway speeds, running 45* cruise timing on base map, and Setting WGDC tables not to be in boost below 30% TPS.

 

and i plan some aero like this :

 

http://forums.pelicanparts.com/uploads11/DSCN33641189086643.jpg

 

http://www.ziptied.com/Coppermine/albums/userpics/10252/07~1.jpg

 

1/8th inch alu is cheap and i think it would be a fun little project to make this thing slippery as hell.

 

 

 

 

 

I enjoy driving my car too, but when I'm on the highway I'm trying to get my family from point A to point B safely and without speeding tickets. It's fun for me to see what my new mods/tune can get me gas mileage wise. Same reason people shoot for 300whp or any other xyzWHP numbers.

 

 

Exactly. i want to tune the 30% throttle possition to be out of boost to help reach this goal.

 

having a slight bump in compression with the 257/b25 should help.

 

 

My suggestions would be Equal length header. Get the header/up/turbo hotside and downpipe ceramic coated. get a grimmspeed TMIC. maddad or nameless catted downpipe. A blouch 18gxt-r, tomioka racing billet 18g(i have this one) or similarly sized as the trans sucks a lot of power.

I get 25mpg with my setup but i have 6spd gearing on my side.

Get the cylinder bores WPC treated if you can afford it. Your basically trying to make the engine as efficient as possible.

 

I have plans to do the crank cams and bearings in wpc, i may do the cylinder walls as well, being that i know the walls have a special coating ill do some more research on that.

 

only downside of running all that stuff, is noise. i want to keep this thing ultra quiet where i can be dead silent at cruise. are you running and aftermarket or stock downpipe back and if so how loud is it compared to stock?

 

Slightly off topic but I watched a video yesterday of a guy who achieved around 40mpg while cruising at 55mph with his 2015 wrx! Unbelievable. At 70-75mph, he consistently achieves 33mpg. And he is not trying to hypermile or anything. Just use the cruise control. He is stock btw.

 

whole different monster. the new FA motors are direct injected with equal length manifolds and the turbo right up front, they are the pinnacle of variable timing and fueling adjustments in the market. they are going to get really crazy numbers for what they are. we are working with basically old technology.

 

I average 26+ over a year of driving, winter/summer gas, 100/28 temp, ~half hour commute on highway/city 60/40 split. 30 wouldn't be hard.

 

As has been said, get elh, a specb 6 speed, forged/light wheels and keep her maintenance up and i'm sure you'd be fine. Oh and tune for economy on the low end and power up top. Easy peasy.

 

Oh, and learn to drive. Alot of good mpg is how you drive.

 

Sent from my XT1028

 

right. i would like to go 6 speed but being that this is the wifeys rocket, she wants the auto. she has no problem with driving manuals, but this is her cozy car. so auto will stay.

 

and ive already been able to, on the first monitored tank get a mixed 21 mpg with a 100mph pull in the mix lol

 

 

 

 

also.

 

russian:

 

is it plausible to run a seperate fuel map/boost map when in sport mode with OE ecu?

 

i know with an aftermarket ecu you could but not too sure about the factory one.

 

or could i say if you could have a switch to change the fuel map on the fly

 

 

Thank you for all of your input and help!

My car is quiet. I Have the factory cat back on mine. WHile parked you hear the camary motor over mine. lol at wot you can hear it spool (fmic and my bypass letting off. that's it.

The equal length header allows you to balance the cylinders and it will be quieter and run smoother.

The cylinder bores don't have a coating they have crosshatching. WPC has a process that makes the piston rings slide in the bores easier.

IDk what you have for a year. But you may want to swap to top feeds and change the craptastic fpr.

I run 6.5mm kstech phenolic spacers. No idea if they help.

also, i'd NOT do any thermal coatings within the engine. for a DD that see's less than 100 mile one direction commute, you'd see MPG drop rather than rise. Heat is good to ~200C, then sure, shedding so you don't destroy metal is good.

 

the PISTON skirts have a coating form the factory, for friction i believe.

 

and with the auto, i'd drop the expectation of MPG a bit. maybe if it was a new CVT, but not the old auto.

 

I'd also remove all roof ornaments unless you're gonna use them that day. that's just letting solid MPG numbers go out the window so the car can look cool.

 

I also wouldn't do over 50% of what you say you're gonna do for MPG and power. most of it is a waste, even more so for a DD with only 300 hp. but whatevs.

WPC is not a coating it is a special type of shot peening.

Seems like you're spending an awful lot of money attempting to get 30mpg when nearly stock motors and cars can do it.

 

One thing nobody has mentioned is tires and alignment. I was easily pulling 29-31 mpg until I bought a new set of tires for it. That immediately dropped the mileage 2 mpg and I've never been able to get it back no matter what I do with it. I won't be getting another set of these tires...

 

I'd focus more on what you can do aerodynamically and reducing losses within the driveline and less on the engine.

 

You want efficiency and are really planning on overhauling the motor? Put higher compression pistons in it. Off boost efficiency should be improved. Or just put an EJ20Y in it and call it a day.

 

There is no way, no how that you're going to get 300 horsepower and 30 mpg at concurrently. The same engine may be able to do both however, and what you need to do to get mileage is to reduce the horsepower required to move the car or keep it moving. That should also help make that 300 horsepower more fun when you decide to use it.

My car is quiet. I Have the factory cat back on mine. WHile parked you hear the camary motor over mine. lol at wot you can hear it spool (fmic and my bypass letting off. that's it.

The equal length header allows you to balance the cylinders and it will be quieter and run smoother.

The cylinder bores don't have a coating they have crosshatching. WPC has a process that makes the piston rings slide in the bores easier.

IDk what you have for a year. But you may want to swap to top feeds and change the craptastic fpr.

I run 6.5mm kstech phenolic spacers. No idea if they help.

 

I would love to swap to EL but craptastic CA smog would really frown on that

 

swapping my stock DP in for the bellmouth is not a big deal to me. header swap i dont want to do.

 

and i know about the cross hatching but i remember them being coated and that was why you dont want to hone subaru cylinders. maybe im remembering wrong or got wrong info..

 

and yeah ive got side feeds. blehhh lol

 

 

 

Seems like you're spending an awful lot of money attempting to get 30mpg when nearly stock motors and cars can do it.

 

One thing nobody has mentioned is tires and alignment. I was easily pulling 29-31 mpg until I bought a new set of tires for it. That immediately dropped the mileage 2 mpg and I've never been able to get it back no matter what I do with it. I won't be getting another set of these tires...

 

I'd focus more on what you can do aerodynamically and reducing losses within the driveline and less on the engine.

 

You want efficiency and are really planning on overhauling the motor? Put higher compression pistons in it. Off boost efficiency should be improved. Or just put an EJ20Y in it and call it a day.

 

There is no way, no how that you're going to get 300 horsepower and 30 mpg at concurrently. The same engine may be able to do both however, and what you need to do to get mileage is to reduce the horsepower required to move the car or keep it moving. That should also help make that 300 horsepower more fun when you decide to use it.

 

 

the motor needs to be built anyways. i want to maximize efficiency while i build it.

 

and no i know there is no way to make 300 hp and 30 mpg at the same time.

 

 

i just want a motor that can do both when i ask it.

 

per say higher lift/duration cams would increase hp but hurt mpg.

 

im looking for all the mods i can do that will benefit both.

I would love to swap to EL but craptastic CA smog would really frown on that

 

Why would california care if you were ELH?

 

And more confused that you'll somehow be able to go with an aftermarket DP but NOT ELH? headers and/or up are WAY more "hidden" than a DP.

 

Could also just go JDM twinscroll and it'll all look stock... you'll even get your bellmouth DP and be able to use it as is if you get a version 9 JDM STI DP.

 

Topfeed conversion (and deletes even) would be equally simple and easy to "hide".

 

 

Not alot of this makes sense. Do you really want input or do you just want to do what you said you wanted to do in your first post?

 

 

And forget all the engine mods, you don't need any of that for 300hp. 300hp is reliable and completely doable on a stock engine.