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Old 04-30-2022, 09:32 PM   #32 (permalink)
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Originally Posted by Gasguzzler View Post
Same problem with a turbo, turbo ing an engine is always less reliable and the cost of the parts and need for premium fuel would make the savings from potential mpg gains less significant.

"Always less reliable?" Isn't that a bit of an absolute? I only saw reliability issues when people slap a turbo to a car without building the car to handle it. i.e. no real plan: no remapping fuel curves (or going to aftermarket FI computer that can detect and properly handle boost), no wideband O2 sensor tied into FI system, no ensuring fuel system can deliver the fuel (as opposite to be on its last legs), and so on. And they they decide to do burnouts, go lean, throw rod or grenade transmission, and it is the turbo's fault, not them being idiots.

Just because you are going to turbo an engine does not mean it can only be used to do 10s quarter miles or faster. A lot of factory turbo cars are built with relatively small turbos so they are useful on the low end, as in passing someone or getting up to 45mph at a brisk acceleration. At highway speeds the turbo is not doing much unless you are climbing mountains, when it may also help the engine see sea level air pressure.

With that said, I know of at least one 2.3L car doing 500HP which did not have any issues besides normal maintenance for more than 10 years now. The fact the owner does not drive it as if he has to drop the clutch between traffic lights may be a factor. Still, I thought this thread was all about economy, so methanol injection, forged crank and rods, and dropping the CR to 8.5:1 really do not belong here.

If turbos did not help with fuel economy they would not be used in 18 wheelers.

Originally Posted by cRiPpLe_rOoStEr View Post
When it comes to turbocharging a port-injection engine, it's also worth remind they may need a richer AFR to prevent knock, even when an intercooler is also used.

In the 80s the recipe to deal with boost was to add 30% more fuel. In more modern times, a wideband O2 attached to a FI system that is smarter than the average politician can do a lot. Add support for knock sensing (you could copy the old APC system if you want to be lazy, but nowadays you can do much better) and ensure your FI system can adjust ignition timing and boost on the fly, and you may have a good starting point.

FYI, I do not remember the last time I saw a factory turbo car without intercooler. I have seen people build their own forced induction, specially supercharged ones, without it but then again some think that intercooling and wideband O2 sensors are witchcraft, and the only approved fuel system is a carburator.

Originally Posted by Isaac Zachary View Post
A forced induction engine will usually need to have a lower compression ratio that will also lower its fuel efficiency, not to mention when you hit the throttle it will need to enrich. Or you need to buy premium, or all of the above.

Most cars using turbo for economy have compression ratio around 11:1 nowadays. They usually are set to handle under 10psi of boost, but more modern fuel systems can push the envelope.

Originally Posted by 19bonestock88 View Post
It seems that nobody is suggesting the fairly obvious choice here. What OP need to put in his S-10 is another GM 2.2, the Ecotec. The first generation L61 is a simple engine to hook up and run and I can speak from experience that they’re pretty efficient. They also happen to love boost if the ~140hp/145lb/ft in stock trim is insufficient, and there are factory parts that can accomplish that from a junkyard, cheap. I’d wager that 30-35mpg wound be very doable with modest gearing and maybe some aero that were done at the same time as the swap

I too agree that would be the smartest thing to do: modern engine with modern FI system.
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