turbo truck better mpg ?
 

2004 gmc 4.3 v6 5 speed, can a turbo give me better mpg ? would like boost from just off idle to 3000 rpm max, 6 or 8 psi would be good.

how about a rear mount with a stand alone oil sys. lots of room under bed pass side,could pick up air thru bed floor in front conner and still have room for slide in camper

looking for easy and cheap, I can fab,weld all hardware.

TIA Charlie

turbos generate boost depending on load. the more load you have, the more fuel you will use so i dont think a turbo will give you more fuel economy.

ive been thinking of turboing my 99 silverado 4.3. theres plenty of room under the hood. why a rear turbo system? its going to cost more to build a rear mounted turbo system than it would by installing it under the hood. an under the hood install would give you those very low rpm boost numbers. a rear mounted setup will generate a lot of lag.



a supercharger will most likely be a better option if you want more mpg as a supercharger is not load based. also a better option if your looking for off idle boost. unfortunetly there is no supercharger option for our 4.3 v6 engines.

Rear mounted because there is room for it under the truck. it would run cooler and less underhood temps.

A stand alone oil sys could be set on a timmer to circulate oil after shutdown. Have its own supply of clean syn oil and a cooler setup, maybe a 3 qt tank ? I am thinking 1 pump and a tank set lower than the turbo, I think a pu has the room under it (mines 8 foot bed.

If you had a problem a long way from home you could un bolt it.

I dont think there is turbo lag in a rear mount, I remember harleys with a turbo in the saddle bags !

So what size turbo to get boost at 1000 rpm ?

yes there is more turbo lag with a rear mount. the farther away from the header the more lag. turbos function from exhaust flow. the closer the turbo is to the header the hotter the exhaust is. the hotter the exhaust temperature, the faster the exhaust flows. faster exhaust flow spins up the turbo quicker. as far as reliability a rear mount has more potential to fail as it has more components and it usually hangs low. a rear mount will cost you more. a good oil scavenge pump can cost 250.00 or more. if your not using the engine oil to feed the turbo you will need another oil supply pump that creates high pressure. this type of pump is even more expensive than the scavenge pump.

as far as under hood temps, there are plenty of products to minimize this. coatings, heat wrap, heat shields, etc.

the size turbo you would need to make boost at 1000 rpm would be so small it would choke your exhaust at mid -high rpm. also it will over rev at these rpms causing heat which will destroy it prematurely.

anyway! just some advice. your going to do what your going to do. post plenty of pics and good luck. i maybe doing this shortly on my truck as well.

When I say rear mount I really mean just past the y pipe, more like a mid mount, lots of room under the bed.
My truck is a 5 speed and never sees over 3000 rpm. wife has an 08 v6 auto and that truck does spin up to 5000 rpm.

Also just got an ultragauge, lots of fun trying to "hypermile"

Well, under the hood setup could use syclone manifolds.

IF you were going from a 350 to a turbo 4.3 you could see better mpg.
You should mount the turbo close to the engine as possible and wrap the exhaust to keep the heat for best response.
When you start building boost the fuel use has to increase also, like to 12.5 parts air to 1 part fuel or even more fuel yet so I really doubt you will get better milage.
What a good turbo system will do is give you greater power and if your like me you will use that power so improved mpg is not likely, but more fun is quite likely LOL

a well thought out turbocharging system raises fuel economy. it raises the overall efficiency of the engine so it uses less fuel to do the same work. throwing a random junk turbo on the tailpipe probably wont help much (it might sound cool) but getting the right one, and mounting it as close to the exhaust ports as possible sure will. get one of the turbo books and read up. i have a 99 s10 with a 2.2 and a t3 that is getting much better mileage than before.

And if you stay outta of the boost, which for a new boost junkie is hard, so realisticly NO, you wont get any better MPG.

And for the money spent on such a project, you should just put it to a gas fund anyway. Or buy a metro.

boost does not raise fuel economy. it essentially raises the engine displacement by stuffing more air into the engine than the engine can hold. also, boosted engines no longer run at 14.7:1 afr. under boost the afr can be 11.5-12.0:1 afr which right there it will be using more fuel. the more you put your foot in it, the more fuel you will use. you also have to factor in that low grade 87 octane can no longer be used so fuel cost will rise. the engine has to use 93 octane from now on.

there are ways around turbo lag on a rear mount. if its just economy youre looking for and not performance you can reduce you exhaust size to 1 7/8 or so from your collectors and 2" after the Y. this will cut top end flow alot so if you wish to maintain performance youll need a pair of large external dump waste gates(70mm+) installed prior to the reduction in exhaust size.

if you really want to squeeze a few extra mpg out of your truck try looking into areo mods like:

http://ecomodder.com/forum/showthrea...ead-11611.html

Boosted cars correctly tuned and built can raise fuel economy actually. Its been proven.

It does NOT raise the displacement, nor does it STUFF more air in there. Are you serious, its physicaly impossible.

There are plently of newer cars tuned to run boost at 87 octane. All in your tune. And making 250+ HP on 2.0L's.

lol. proven? where? i want to see where a turbo will raise fuel economy...poor tune, professional tune, base tune makes no difference. more engine load= more boost= more fuel. simple as that. the only way the engine will not use a lot of fuel is during cruising speeds where there is very little engine load. this is going on a truck engine where he wants the boost to come in at low rpm. the engine is going to see boost most of the time so there is not going to be any fuel savings here.

yes. boosting an engine acts the same way as increasing the displacement.
example: a 2000cc engine running naturally aspirated can only suck in 80-90% of its displacement (also known as volumentric efficiency). when an engine is boosted, more air is being pushed into the cylinder (psi) instead of being sucked in the cylinder(in.hg or vacuum) causing the cylinder to fill with a larger air volume than the cylinder itself. volumetric efficiency can go well over 100% under boost. in this case the 2000cc engine under boost is acting like its a 2200cc or 2400cc or 2800cc engine. this all depends on how much boost. this is the whole point of boost but you say its not possible? its simple physics. air is compressable.

newer cars are different. they can get away with it because most newer cars are now direct injection with low boost. most newer factory boosted cars are grossly de-tuned for reliability. auto manufacturers spend millions of dollars in dyno tuning time to make there tunes safe and reliable. running 87 octane on conventional boosted engine is a good way to go boom!!!!!!! ive been in the business for decades and ive never seen a turbo'd engine running 87 octane while being tuned. it maybe possible but your not going to be able to run any reasonable amount of boost pressure especially on a n/a engine converted to boost as the compression ratio is too high.

^ I was like "what?" for a second, then I remembered what site I was on and I "lol'd".

17psi running 87 octane is not really low, on any engine. And your tune has everything to do with MPG and power, I suggest reading some actuall race and tunning shops for true info, not just internet forums. You may learn something.

But Ill digress and leave this forum, I see its not for my kind.

Ive seen people run 8psi up to 16psi on normally n/a engine with high compression, again if you understand how to tune your engine correctly you can do alot.

sleepy is right... turbos increase fuel economy. just not when in boost. thats why all long haul trucks are turbo'd... if you dont believe me than you have alot to learn about engine efficiency...

yes you can SAFELY run 87 octane in a completely stock: mazda 323GT 1.6T, doge colt 1.6T, mercury capri 1.6T, vw1.8t and 2.0T, plymouth caravell 2.2T, chevy sprint turbo 1.0T, 4g63 eclipse/talon/laser 2.0T, mitsu starion/conquest 2.4T.

im running a 9:1 n/a motor on 91 octane making an estimated 275-300whp on 14psi and i still get around 30 combined city/freeway with moderate/spirited driving.

it all comes down to efficiency. a turbocharger, done right, uses the wasted output of the engine (heat) to create a source of "free" power. ask any race engine builder...higher cylinder pressures are more efficient, and on the most basic level, thats what you get from a turbocharged engine. an n/a engine cant achieve the cylinder fill, scavenge, combustion pressure/temps, or fast burn times of a boosted engine. and at the very least, there is much less surface area in the cylinder of a small engine to absorb heat compared to a larger n/a engine of equal output
also, if 2 engines of the same size and hp are compared, one boosted, and one na, the turbo engine will always get much better efficiency, just because of the mild cam and lower rpm needed. a 400 horse 350 is easy to build either way, but the turbo engine will idle at 650 with 19"vac, cruise like a cadyy, and get 22+mpg on the highway...the cammed up thumper will idle at 950 with barely enough vac to run the booster, and get 10mpg, probably pulling the secondaries open down the interstate :)