The turbo is, like the Gear Vendor overdrive, another Swedish invention.

A mechanic friend mentioned that a turbo is 'free' hp. Does anyone know what a turbo set up does for your mpg? hp?

 

From my limited understanding, (have had a few turbo cars, but never really delved into them much), the turbo is sorta free horsepower. The downside is that you have to lower the engine compression (losing power and mileage), and richen up the fuel mixture, since the turbo atomizes it differently. Both hurt performance and fuel mileage.
However, that being said, the turbo then turns around and gives that extra free horsepower back to the engine, making up for those differences. So, in theory, a well set up turbo can balance itself out so you never even know its there until you step on the gas.
Not sure if you'd gain any fuel mileage, but there's a free horsepower boost sitting around your engine bay for when you need it.


Someone else may have more info, as always. =P

 

The power is refered to as "Free", since it doesn't consume power to drive the turbo, unlike a supercharger's parasitic drag that requires power to turn it.
The power can go way up, depending on boost level achieved. As the boost goes up, so does power, but at the cost of MPG and engine durability. Proper tuning throughout the RPM and boost range is critical, or it could kill the engine in a hurry.
A well tuned, lower boost setup (say 5-7 PSI) driven in a conservative manner, can last for a long time, and yield decend MPG. All while having the extra kick in the pants, as needed.

 

in my op. a very good reasonable overlook of turbos with the proper cautions pointed out, it has been shown , that properly sized, and REASONABLE boost level,,s can provide very good mileage. well written and well said in my eye,s makes you want to install one don,t it. paul.

 

Actually, yes. I have considered adding a small turbo, in blow-thru configuration, to my stock carbed 300. The carter 1bbl can easily be boost-prepped, as ford did it on the early 2.3L turbo. The stock log exhaust manifold would also make for easy work to fab into a turbo.
I may pursue this idea further once I get the drivetrain swap finished.

 

there always seems to be controversy , or pro,s and con,s if you will, about the difference between blow through versus draw through. any thoughts, exp, anything you care to teach me or share. i,m looking to learn anything i can in this area thanks up front if you make time. paul

 

Blow thru requires boost prepping the carb, as well as a blowoff valve to prevent compressor surge. There's nothing but air flowing thru the turbo, so less chance of air/fuel seperation or fuel pooling. A rising rate fuel pressure regulator is also a good idea, so as the boost goes up, so does the fuel pressure. 5-6 PSI fuel pressure is fine for idle/no boost, but when the boost starts climbing to near the same as fuel pressure, the fuel is less prone to flow into the carb.
Intercoolers can be used much easier, since it's just pure air. Of course, turbo lag would be increased, but intake air temp would be lower.

Draw thru doesn't need a blowoff valve, since it would restrict the flow of from entering the turbo, but the high vacuum *can* lead to premature turbo oil seal failure. The rising rate FPR is also not needed, as the carb never sees anything higher than atmospheric PSI. The aforementioned fuel seperation and/or pooling can occur, as well as having a combustable mixture inside the compressor side of the turbo, which is quite close to a heat source. Intercoolers are not a good idea either.

I've never played with a boosted carb, but I have done some research into the subject. In my mind, blow thru is the way to go. I do have hopes of building a blow thru system on one of my rotary powered cars, and have given some thought to doing it on my 300 powered truck.

Paul.

 

very strait hardcore facts to the point. informative for me. will be watching any future posts by you on the subject. a turbo is just simply one thing i have never run. deeply interested in the applications. thanks

paul

 

One vehicle to look at is the Subaru GL of the late 80s- Wagons were offered in both turbo and n/a versions, there wasn't a whole lot of boost either, only 6psi. They dropped the compression, and also changed the final drive gearing from 3.9 to 3.7 with a pretty tall OD in the automatics. The n/a engine only made 95-105hp, while the turbo engine made 115-120hp, not much gain at all. Plenty of lag, it would struggle for a bit then kick in and give a bit of a shove, but on the highway you are in boost all the time. The n/a car would get 30-32mpg on the highway, while the turbo car got low 20s, a 10mpg penalty for another 15hp.
Personally, I think turbos are great on diesels, there it will actually increase the fuel mileage quite a bit, but on gas engines they are just too much trouble.

 

Factory gas turbos are pretty well sorted out these days. But sorting one out yourself is a difficult process. See the 4 year turbo 300 thread in the Supercharger/turbo forums, and another more recent thread there.

 

The real issue with adding a turbo to any engine, is getting the right size and exhaust/compressor blade pitch, then getting the fuel trim and timing curve set correctly.
If you have too small of a turbo, it will never give the output you would expect. Too big, and lag is a huge factor, followed by scattered engine parts.......
Get it all right, and the results can be fantastic. It's getting everything right that's the real challenge, without wasting a lot of money by learning the hard way.......

 

Just goes to show how NOT setting one up right really messes things up. On the flip side, I had an '87 Toyota Supra. 3.0L straight six. The non-turbo made 200hp and 190tq. The turbo model made 230hp and 245tq and only put out 6lbs of boost stock. Both models got 18 city, 23 highway.

Setting a turbo up on a 300 would be a lot of fun, and from what I hear, they do really well. Just gotta have the deep pockets, or someone who's already got a lot of know how.

 

A few years back I was playing around with a 300-6 twin turbo, but then most of my stuff got stolen and I lost interest.
The T03 used on Chrysler four cylinders in the late 80s is the perfect size for running twins, but if you're going to do it run EFI and an aftermarket controller. I have dealt with carbed turbo cars, including Maserati Biturbos, and they are not fun to deal with. Constant tuning, and even at their peak they are pretty inefficient. Intercooler, properly tuned EFI, and correctly sized turbos are the way to go.