legacycentral bbs

Now I love boost as much as the next guy but here's my dilemma: The scooby wagon is the wife's car and she uses it for some light commuter duty. She wouldn't know performance if it rose up and smacked her in the forhead and would rather save the gas than mash the gas ...

So I wonder what fuel savings could be had if a fellow put a MBC on the legacy and dialed the boost DOWN to a max of (arbitrary number time) say: 4psi instead of the stock max (around 9 I think). most of the commute she has is just lazy highway cruising so I reckon the reduction in power wouldn't kill the car too bad. Heck I can get to there and back in a 54hp metro so losing a few ponies seems reasonable to me... and THEN if I wanted to drive the car for the day I could dial the boost back up...

anyway that's my loopy ramblings for now. let me know what you folks think. I'm not awfully familiar with boosted cars yet but this sounds like it could work. and I'm pretty sure I'd want a boost gauge for this process but that's okay because I want one anyway

i have one of those.

its called my foot.

sorry couldnt resist.

considered this too but for the winter months to minimize wheelspin on ice.

greg donovan wrote:i have one of those.

its called my foot.

sorry couldnt resist.

considered this too but for the winter months to minimize wheelspin on ice.

hahah yeah yeah smartass

I know what you mean with the foot However, The Wife uses cruise control and I think on the 110km/h highway is probably humming along a just below where the car wants to make boost. and then every time there's a hill or a stiff breeze it'll pop out of overdrive and run up into boost when it really doesn't need much power, it just needs to get the revs up a little to compete with gravity or what have you... once again I welcome all input as I'm just brainstorming with you fine folks here plus it's slow as hell here at work tonight! heh!

What lb rate is the stock wastegate spring set at? This will be your minimum boost pressure.

JasonGrahn wrote:What lb rate is the stock wastegate spring set at? This will be your minimum boost pressure.

okay. how about changing wastegates then? or am I way off base here?

Connect your turbo compressor boost control outlet directly to the wastegate and you will have 6 lbs of pressure, as that is the pressure our wastegate will open at.

When you want your 9 lbs back, reconnect the lines back to the boost control solenoid.

No MBC needed.

Not-as-good-of-an-idea-alternative: Get regular gas instead of premium. Your computer will limit the boost to wastegate boost automatically. Although this doesn't always work properly... its better to just connect the compressor directly to the wastegate for minimum boost.

free5ty1e wrote:Connect your turbo compressor boost control outlet directly to the wastegate and you will have 6 lbs of pressure, as that is the pressure our wastegate will open at.

When you want your 9 lbs back, reconnect the lines back to the boost control solenoid.

No MBC needed.

Not-as-good-of-an-idea-alternative: Get regular gas instead of premium. Your computer will limit the boost to wastegate boost automatically. Although this doesn't always work properly... its better to just connect the compressor directly to the wastegate for minimum boost.

whoa! that's a very interesting idea! has anyone ever tried that? and/or anyone wanna guess if it'll save any fuel or not? I've also wondered about running lower octane gas as well. good to know how that works! thanks!

Wouldn't that also cause it to pull timing and deliver worse mpg?

I think the octane idea is not so good, I was just offering it as an alternative since it does result in the lowering of the boost.

Bypassing the boost controller's a much better idea.

Yep, wastegate boost will be about 6 psi.

The suggestion by Chris to hook the compressor outlet line to the wastegate will work good as long as you're stock.

For those guys with mods, mainly TBE, we've seen that just hooking it up that way can cause pretty severe boost creep. Especially on after market turbos like the 16G. In those circumstances you definitely want to use a MBC and just open it all the way up.

Some boost is better than no boost for mileage. I have no boost and get 21 with average to careful driving.

Steve

legacy92ej22t wrote:Yep, wastegate boost will be about 6 psi.

The suggestion by Chris to hook the compressor outlet line to the wastegate will work good as long as you're stock.

For those guys with mods, mainly TBE, we've seen that just hooking it up that way can cause pretty severe boost creep. Especially on after market turbos like the 16G. In those circumstances you definitely want to use a MBC and just open it all the way up.

Our wagon is 100% stock right now so do you reckon there wouldn't be any boost creep ? I may just have to try this theory out after I get ahold of a boost gauge so I can tell if anything funny is going on

Should be no boost creep for you, Fishy. Boost gauge is a good idea, but shorting the compressor and wastegate hoses to bypass the boost controller will definately result in 6psi of boost.

It will also probably spool up a little slower, as the wastegate will begin to partially open near 6psi - this is called wastegate creep. Bad for performance, but you don't care in this case.

The boost controller can promote faster spoolup by not letting any pressure get to the wastegate until the desired boost level, so it stays completely closed and forces all the air to spin the turbo.

Boost creep is an impossibility with your setup. Don't worry about that.

Okay,
I'm ready to admit I don't know what I'm doing I'm also still waiting to get ahold of the repair manual for the car so I'm a bit lost under the hood at this point... However since gas prices went up AGAIN I'm ready to try this low-boost "mod".
Does anyone have a description or picture of what to do with which hoses to achive this straight-to-wastegate hookup? As always any help would be greatly appreciated. with supreme gas being $1.056/L every bit helps!

For those keeping track I believe that's about $3.46USD/gal

Locate the boost control solenoid. It's mounted on the passenger side strut tower, under the pressure exchange solenoid. See the picture at the top of this page:

http://www.graphics.cornell.edu/~v/chrysler_map/

There are two hoses attached to the side of the solenoid, going towards the turbo. Pull both of them off the solenoid and join them with some kind of hose coupler. I think ideally you'd use an elbow with a 3/16" barb on one side and a 1/4" barb on the other.

vrg3 wrote:Locate the boost control solenoid. It's mounted on the passenger side strut tower, under the pressure exchange solenoid. See the picture at the top of this page:

http://www.graphics.cornell.edu/~v/chrysler_map/

There are two hoses attached to the side of the solenoid, going towards the turbo. Pull both of them off the solenoid and join them with some kind of hose coupler. I think ideally you'd use an elbow with a 3/16" barb on one side and a 1/4" barb on the other.

thanks a bunch! I'll try this out and let everyone know the results (if any).