Dual stage boost question

[serenity88]

I'm toying with the idea of installing a dual stage boost control in my wagon, What I really want to do is (this is were it get's a little sticky) set the lower boost rating at next to nothing (at which they will in fact create better gas milage than a standard 2.5), And then set the upper rating to around .9 bar.
With my limited knowledge of turbo's I can already see a couple of hurdles.

So my questions are:
A: Is this a good idea???
B: does anyone see any pit falls or barriers?

I'm sure it may reqiure some serious tinkering, but at the moment I can't really see the down side! In would in effect be the ability to turn the turbo's on and off (so to speak) and should contribute to some serious gain in economy. My fathers got a 2.5 diamante and it rock and rolls in it's own right, So I like this idea ( at the moment anyhow)

Look forward to some replies on this.

[Paul Beazer]

And how would you plan to do this?

[stuartturbo]

I did fit an apexi unit with OFF setting A and B
for the same reason but it gets left set a 0.8bar and never changed
best bet is drive off boost and low throttle loads etc stay lower speeds no labouring engine( 3rd @ 3000rpm may be better than using 5th) or ask
/lol BRAD"highestmpgever"C /lol/lol/lol/lol

[mpau009]

I dont think your idea will work in the way you intend. I had a four setting boost controller a while back, with settings ranging from .6 to .95 bar. Which was ideal for when i didnt want to be running 14 psi on the way to work in the mornings, and (hopefully) making the engine last a little longer.

But when i switched boost controllers, i was actually without any boost control for a few weeks, including a road trip to rotorua. You wont see that much improvement in fuel use, because you dont spend that much time at those boost levels, so 99% of the time your fuel consumption will be the same. Certainly no better when cruising on longer trips or the motorway.

You can still get 7 or 8 psi just from the wastegate spring, but the car feels very slow, and it takes a lot longer to build.

The best way to improve your closed loop AFR's would be to alter them with something along the lines of a wideband sensor, or full or piggyback ecu like my MAP2, neither of which are cheap enough to get your money back in petrol. Try a search for a few posts on Air Fuel Ratios, and see what discussion there has been about closed loop AFRs, versus under boost.

But in my opinion having a couple of boost settings is a good idea, just because you can still have the power when you want it, without constantly hammering your engine.

[bradc]

yeah leave the boost as it is and learn how to not floor the throttle everywhere!

[djb160]

yeah leave the boost as it is and learn how to not floor the throttle everywhere!

C'mon Brad, you can't go telling people things that just aren't humanly posible. :D

[serenity88]

This is exactly, what I was after. It seem's that there is a bit of experience out there!

I am going to go with a dual boost control set up. i guess I'll have to leave it fact + more boost at the flick of a switch! and I might have to invest some coin into shares in an oil company.

Although I'm not thouroughly convinced as of yet. i realise that it wouldn't be an easy rabbit to pull, but at very low boost levels turbos (in theory) do actually increase economy over a standard motor of the same size.

It would reqiure two completely independant series of settings with the ability two switch between. There's no point just turning the boost down or off without making all the tuning adjustments to suit. Cause you'd still in effect be running the engine at the fact settings with no boost to speak of.

This is why I said it get's sticky!

[orionn2o]

So you want a mappable ECU then...

In which case you're looking at 500 or 900 ish quid depending on whether you want a MAP1 or MAP2 (Map2 obviously being better cos it has a larger table + possible extra features??)

So IF you managed to save £5.00 a week in fuel it'll only take 2 years to pay off!

[Subaru ETA]

errr you cant actually turn boost off......
anyway my mate had a eboost in his legnum..ran .9bar and std settings. he paid $1000 for it so he could do this but said it was a waste of money because lets face it, when you nail it you want to go fast! if you dont want to go fast and save gas, dont nail it everywheere! so he jsut left it on high boost all the time

[orionn2o]

Thats exactly what I do too..

I can set my boost to low, high or turn the controller off and let it run on standard settings.

And It either sits on medium high/high (high is a little less drivable on small roads)

[MPBVr4]

(high is a little less drivable on small roads)

For interest. What is "high" set at?:inquisiti

[orionn2o]

0.9 to 0.95

I can only run that with the cat out though because the boost isn't steady with the extra back pressure.

It just tends to splutter and stuff when you come off the gas etc around town. Of course it is also well fast though!

[serenity88]

Well actually I am talking about lowering the standard settings, I reckon I could open the waste gates real early if I change the spring resistance in the waste gate actuator!, install a pre actuator solenoid set for the upper limit. I really feel thats the easy part!

The problem would be in the difference to the tuning, obviously running around with 1 pound ( or whatever the lowest acheivable is) of boost is going to be a big difference to say 14 and may reqiure some sort of limited ecu overide, perhaps achievable with a piggy back. I'm pretty sure that the standard ecu settings would more than likely interperate 1 pound of boost as some kind of a problem and do something stupid. Not to mention if it didn't it would run too rich and wot not.

Spending big bucks on an management systems is probably a waste of time, unless ugrading the turbos to suit and if your looking for more power! I'm trying to go the other way.

I know it may seem stupid, but I have this crazy vision of inventing a system to turn turbos on and off (so to speak), one minute cruising down the road in nana's shoping basket getting 14 k's/ltr, flick of a switch and bang your boosting at 14 psi paying for the war in Iraq!

Obviously I'm not the first person to have this vision

[stuartturbo]

what you need is some one with live mapping to note the difference in the injector opening time on a high and low boost setting. I have no car at mo and it will be mapped so differing from std.
You may find they are very similar so you have no benefit running min or max boost as it is done off throttle position and load

[mpau009]

All of these ideas are going to cost money of course, and the V6 STR economy wasnt that great to begin with, certainly i can live with the extra $10-15 a week.

Probably the cheapest mod i could think of, if it would work, would be maybe you could have two ecus? one from the V6 (assuming they have different fuel maps), they could both be wired in, and connected to a switch or something so when your anti boost thing is connected, the VR4 ecu goes off, and the other comes on. Dont know if that would work, and you prbably coudnt switch on the fly, but you could get the ecu cheap enough.

Anyway, it all sounds like a whole lot more work than staying a few hours later at work to pay the fuel difference:afro:

Not to mention the shame of driving a handicapped VR-4 in public:P:smash:

[bradc]

V6 is sohc, it won't drive a VR-4 engine.

It's all to damned difficult imho, the only things you could really do to save petrol would be:

don't use aircon
keep the tyres at a slightly high pressure
keep the windows shut
maybe install an apexi afc, but it is going to take you years to pay it off in petrol savings.

Anything more than that is just a complete waste of time.

[Subaru ETA]

to wind bosst lower than std it going to cosat far to much and i dont think that when you drop below std you will be able to swwtch to say 1 bar..

the str 4wd is not and economical car at all...well the auto aint anyway. my vr4 gets better economy thatn my str did! the cheaper thing to do would be buy a cheap mazda or toyota or something to be a work hack and save the real toys for the weekend

[djb160]

Wouldn't a good induction setup and FMIC help with the mileage in a bang for your buck sort of a way? Anything with a VTEC seem to get awesome mileage from what I've seen.

[serenity88]

Yea 4wd that does it. Had an mu4 chewed the juice all right but it was cheaper to run than the vr4. Actually was thinking about it and it could be done very cheaply with an alternate pressure source set at the fact spring compression point, and a three way selector valve plumbed in.

The theory is that a turbo when not boosting will actually atomise the air and cause all the fuel to be burnt, thats the important part! It can acheive a 15-20% increase in economy over an engine of the same size. That is a significant figure! Worth investigating.

I've got a cylinder charged with nitrogen that Im going to hook up to the boost actuators, bypass them altogether. In effect the wastegates will be wide open. I'm going to take it for a drive this weekend and see what happens. See what the ecu does, as stated the difference may be negligable to the fuel settings.

This whole scheme hinges on the theory that turbo's can also be fuel saving devices

[unclepete]

I'm not technically minded in any way so I'm maybe missing the point here, but I'm quite impressed with the economy of my VR4. Boot it and I'll get 15 mpg, short journeys kill it but I try not to do those in such a car anyhow. If you wish to drive efficiently then I've had 32mpg from driving on a motorway at 80/90 mph. I only occasionally put my foot down though. Still the fastest thing on the road.

I drive a £700 (2 1/2 years ago) Honda Accord 2.2 VTEC for other journeys, surely getting such a car would be cheaper than messing around with your motor for very little benefit?

[serenity88]

One thing we don't have a shortage of down here is cheap cars! our second hand car market is so over stocked that finance companys and dealers are droping like flies!

The whole point of my insane exercise is to see if I can develop an 'on, off'
switch for the turbo's!

It's a kiwi thing, doing crazy stuff that most people would consider to be pointless and useless is on thing I'm really good at. And hey, every once and a while I've been known to pull a rabbit out of the hat!

I't wont be expensive either, I believe (in theory at least) that I can achieve this result for under $500, the as of yet undiscovered results are still to be detirmined.

I do freely admit that it is a hairbrained scheme though /pan .

[djb160]

I drive a £700 (2 1/2 years ago) Honda Accord 2.2 VTEC for other journeys, surely getting such a car would be cheaper than messing around with your motor for very little benefit?

Is that a Euro R? My brother has one and they're really hard to find here. Damn expensive to. Very nice car. Love that VTEC.

[unclepete]

Is that a Euro R? My brother has one and they're really hard to find here. Damn expensive to. Very nice car. Love that VTEC.

Not a Type R but it's the same engine - 2156cc 4-cylinder. I love the Accord Type R but it likes to shred front tyres. The engine is superb though. Mine's 150bhp although feels like much more (keeps up with many things out on the road) and does tons to the gallon. It's also got 192,000 miles on the clock, which is not too shabby.

[Wodjno]

The whole point of my insane exercise is to see if I can develop an 'on, off'
switch for the turbo's!



This item already exists /yes

So don't go wasting your money on developing a New 1 :thinking: