Lower Boost for MPG?

Ozified · Post by **Ozified** » Fri Aug 25, 2006 4:29 am

Hello All,
Since I am running about $300/mo in gas...

I was wondering if I limit my MBC to about 4-5psi on my 93 SS, will there be significant gains in MPG since I won't be spooling gas as much?

I know driving habits and shifting under 3k rpm really help!!! - I have gotten as high as 24mpg freeway trips, driving 65mph yada yada - boring.

Anyway, by turnign the MBC down, that willl help with temptation - any other comments doing this or other PSI recommendations?

thanks, PK

Post by **Legacy777** » Fri Aug 25, 2006 4:39 am

Just stay off boost and you'll get better mileage

IronMonkeyL255 · Post by **IronMonkeyL255** » Fri Aug 25, 2006 4:49 am

Can you even turn boost down below wastegate boost with a MBC? I don't think so...

free5ty1e · Post by **free5ty1e** » Fri Aug 25, 2006 3:20 pm

You can turn your MBC down all the way, (or bypass the MBC and connect the compressor directly to the wastegate) and you'll get ~6 PSIg. If you want to go any lower, you will have to set up a helper spring on the wastegate to help pull the wastegate open earlier.

As another option you could wire your wastegate arm totally open so that your turbo never spools. This is very useful for turbo break-in sessions, and would eliminate any ability you had to waste gas on boost

rallysam · Post by **rallysam** » Fri Aug 25, 2006 6:27 pm

Yeah, can't go below 6 without wiring wastegate open. Just lift your right foot a little higher - that's pretty much the same thing.

free5ty1e · Post by **free5ty1e** » Fri Aug 25, 2006 6:43 pm

Obviously restraint is the easiest solution to this problem.

Bane · Post by **Bane** » Fri Aug 25, 2006 8:55 pm

i have a dual stage mbc set at 10 and 15psi.

i get better mileage when i'm at 10 then i do at 15. probably about 100km extra a tank

in fact i get better mileage on 10 with the vf34 and intercooler then i did on the vf11 at 13psi

also helps to set cruise control for highway driving and not to pass all the time at WOT

then again, all that said... i'm having a really hard time keeping the switch on 10psi.

i spend about $700-$800 a month on gas.

realfinn · Post by **realfinn** » Fri Aug 25, 2006 11:12 pm

VF34 and an IC at 10-15psi and you pass at WOT????

Subtle · Post by **Subtle** » Fri Aug 25, 2006 11:16 pm

Bane

How many km to the tank--in town and on the highway

Thanks

Bane · Post by **Bane** » Sat Aug 26, 2006 12:43 am

finn:
lol, yes... otherwise driving would be boring

I have been told that i tend to speed occasionally...
but then again i say the wife doesn't drive, so her opinion doesn't count... lol

at 10psi it's got better response and top end then the original turbo at high boost.

at 15psi it pushes your body into the seats during acceleration.

I still need to get bigger injectors and go for a tune at Neetronics to optimize it.

Subtle:
it's almost all highway driving. i put on 5000-6000km a month.

I'd say it's about 80-90% highway and 10-20% city driving.

at 10psi, cruise control set at 120km and not trying to pass at stupid speeds... about 400-425km a tank

at 15psi flooring it at every green light and "extended" periods of "passing", i get about 300-325km a tank

realfinn · Post by **realfinn** » Sat Aug 26, 2006 1:52 am

Bane wrote: I have been told that i tend to speed occasionally...
but then again i say the wife doesn't drive, so her opinion doesn't count... lol

LOL....Your wife and my girlfriend should hang out.

farfrumwork · Post by **farfrumwork** » Wed Aug 30, 2006 10:27 pm

Like others have said - use wastegate boost levels and keep it out of boost as well as you can... And/or drive less

I spend $200-250/mo in gas on the turbo beast. My commute is only 10mi each way though, mixed country/town roads and I get 22mpg on average. I see 25-27 on freeway trips and up/down the mountain (5500ft -> 12000ft and back) - and that is NOT taking it easy (frequent excursions to triple digits, and the passing lane over Berthoud Pass).
This thing is seemingly quite efficient (13psi, Pulley, A/W IC, 3" CES TBE - - the last 3 help with economy and Fun) I can beat up on stock wrx's all day long too!

YMMV - (literally)

Ozified · Post by **Ozified** » Sun Sep 03, 2006 7:28 am

Thanks All.
I have been driving this week not going positive PSI - just keeping it at 0 (zero) or vacuum as much as possible and got 23 mpg, usually I get 19 (but have a lot more fun).

Still, I would like more, but I understand discipline on the long pedal is just as good as limiting boost - same effect - so makes no sense to limit power - just dont use it and keep it available upon request when you really need it.

r/ PK

Richard · Post by **Richard** » Wed Sep 06, 2006 4:45 am

Get a 4-spd 88 VW Fox. $70 a month in gas @ roughly 25 to 35 miles a day. And that's with premium.

Shitbox FTW!!!!!

realfinn · Post by **realfinn** » Wed Sep 06, 2006 4:05 pm

Richard wrote:Get a 4-spd 88 VW Fox. $70 a month in gas @ roughly 25 to 35 miles a day. And that's with premium.
Shitbox FTW!!!!!

And if your location is still correct you are probably running on a mix of ethanol and gasoline. IIRC WI was one of the states requiring a mix (maybe 15%?). States where that isn't a requirement should get better mileage, I would think.

Richard · Post by **Richard** » Thu Sep 07, 2006 5:10 am

Well kinda. The state does not require all gas to be sold as e10 (10% ethanol). But in southeastern Wisconsin (where I live) the EPA mandates its use due to our population density (like most major metropolitan areas). I haven't traveled far enough with it to get real gasoline since its a beater, but I'm sure it would get better mileage if run on sans-corn fuel. I noticed the difference with my other cars. It would probably run a little better too.

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Lower Boost for MPG?

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