I have been a turbo lover for years, I have been fortunate to drive a number of them. The 930 Porsche, Pontiac Sunfire turbo, Sprint turbo GT, and the one I owned for years was a Volvo 240 turbo. Dig up stuff online about Smokey Yunich and his Hot Air Engine.
Smokey in 1978 took a low pressure turbo (1 to 4 pounds of boost) and ran it through a 4 cylinder, the 2.5 litre Iron Duke GM four. The air was pre heated before the turbo and after the turbo, through water and exhaust heat exchangers. The car was feed through a conventional carburator and the intake charge was at a temperature of 460 degrees before it entered the engine. The engine produced 200 plus horse power and gave 50 mpg.
The engine was carburated and was said to be terribly cold blooded until the intake charge was hot enough, but this was back in the late 70's early 80's. Now with fuel injection and onboard computers I think it should be much more manageable to run such a "On the Edge" engine.
A basic turbo does a number of beneficial things. It gives the engine back pressure so the fuel charge isnt blown out of engine. It lightly reduces mechanical vacuum pumping due to pressurization of the intake. It also heats the incoming air temp to around 175 degrees, improving vaporization, this is why people add intercoolers for performance and to reduce detonation.
My turbo Volvo was 3000 pounds, had the aerodynamics of a refridgerator, and gave me 24 to 26 average mpg commuting in San Francisco. Mine had the 2.1 four, the non turbo got the 2.3 litre four. Now just in a performance related spectrum, I could keep up with a V8 Mustang and a 300Z, I would say side by side performance if we were on a track.
Now lets take all this fire and speed and put it in a 750 four or 1 litre, maybe a max of a 1.3 litre four. I envision 55 to 70 mpg with all the power of todays 2 litre engines and meeting all the smog requirments.
I think the future will involve turbo's in every aspect of engine developement. When I get my next car I definetly want to put together a turbo package for it. Engineering efficiency into what was considered a performance only application of technology.
VW came up with a setup I thought was interesting. It used something like a 1.4L motor with a super charger for low end and turbo for high. IIRC it put out well over 200hp and I think FE was around 40mpg.
Saab has been adding low-pressure turbos for years. I have a the 2.3L LPT engine, 185hp in a ~3700lb wagon. EPA rating is 21/30. I usually average 25mpg in suburban driving, and 40mpg very carefully on the highway.
I believe my wife's car (ladybug Maxx on my garage) has the same tranny as well - and even with her driving style we get easily over 30, can get 38-39 highway. We got 38+ MPG across Nebraska at an average of 85 MPH some time back - ALL highway miles, and let me tell you with the tank full to the top of the fuel neck with over 17 gallons in it, it's just awesome to get over 650 miles on a tank.
The Maxx comes with a 3.9L SS option but I can tell you that her V6 has zero problem on the hills, and this is an automatic car.
Looking to trade for an early 1988 Honda CRX HF (Pillar mounted seat belts)
I think GM intentionally sabotaged the 4 cyl so that people wanted the V6. this thing has a 4.39:1 diff and tall gears in 2nd 3rd and 4th the final drive ratio in this is 3.91 so it's a huge jump from 1:1 and with a little more power that jump probably won't matter.
From what I was told, which makes sense, is that a small turbo which hits full boost at 2500-3000k will give you better mileage, cause of the air forced into the motor with the turbocharger. It was explained to me, but can't remeber it exactly. I don't want to say something that isn't ture
But what I've noticed, since I have a turbo on my car. Is that a lot of things cancel out the effecientcy of the turbo to not even having one.
Extra weight: of the turbo, intercooler, charge pipes, etc.
Premium gas: I don't use it cause I don't even rev my car up enough to actually build booost.
Sythentic oil: is better, cause it has a higher boiling, which makes it less susceptable to coking the the turbos center cartridge. I don't run synthetic though....
not really having the ability to do EOC'ing. which get me to another thing. having the leave the car running for a minute or so before tuning off the engine. synthetic oil and water cooling the turbo help this, but at what cost.
though water cooling could eliminate the need to "turbo time" the turbo before you shut off the car and still allow you to EOC. plus a synthetic is more costly, but it supposedly gives your better mileage anyway.
Plus the cost to put in a turbo and tune it is probably somewhere in the range of 6 months( actually way more then that) gas, at least. then troubleshooting it and tuning it.
sorry, I'm rambling. I've been into mileage for awhile now and site is really motiving me,
I agree on all your points. I must add I don't EOC due to the power steering basically making it impossible to turn. I have two or three turbos to choose from: T25 off of a dsm, an IHI from a Tbird, or a T3 off of a Chrysler. I am leaning toward the Tbird turbo due to the availibility of T3 flanged manifolds and the small size of the turbine housing. on the 8 valve 2.3l Tbird it is at full boost by 2000 rpm so I figure on my 16 valve 2.2l it should spool in similar time.
wow, I wrote that post bad, I'll go back and clean it up.
but a t3 is way bigger then a 14b or IHI. I have an IHI on my civic and that things tiny. I don't what rpm it hits full boost, cause I've yet to fully tune and diagnose all my problems with hitting full boost.