[Allch Chcar]

The overlap on most cars is not an issue as they operate at very lower RPM. What you are talking about is something that happens to Racing cams at low RPM, they will literally pull fuel out of the cylinders and therefore have no power. The only minor details is dealing with a small econo engine that has one cam that is for a more mid RPM peak. They don't have a turbocharger of any sort beyond the cam and so might have a teany bit of overlap and duration(things that affect scavenging of the cylinders).

Most of the old Ford engines had low profile cams and usually would generate peak torque between 2k RPM and 3k RPM and reach peak HP between 4k RPM and 5kRPM but they're usually much bigger displacement Ironblocks than their competitors especially Foreign cars.

I've been looking more and more into taking a "small" displacement Honda or even Toyota engine because they use multi cam systems. If the low cam has a low enough Torque peak it could be used with a turbocharged system and still maintain cruise at low RPM in a much bigger heavier vehicle or just a taller geared car. Honda and Toyota use smaller displacement 4 cylinders than Domestic cars but I'm talking like taking a Honda Civic Hybrid's 1.3L (only because it came with a manual transmission) and putting it into a midsize/sports car. An engine swap is usually beyond the scope of most people but it's one of the best ways to acheive an ends and when you're into ethanol and turbocharging you really have to think small to find something that replaces a bigger engine yet has a smaller displacement. If you go from a 2.0l to 1.6L sure you'll save gas and can usually, gear or cam your way to enough power. But with turbocharging you can get a bigger engine's power from a smaller displacement and pow suddenly a 1.3l or 1.0l starts to look like enough or even too much. If I wanted to drive a Focus or a Civic it'd be much easier because they already have small engines but I want to drive an RX-8 kind of vehicle, it's more aerodynamic than a Focus but it's 3k lbs and light on it's feet. If I put a 1.3L Civic hybrid engine in it I'm crazy but if I turbo charge it I'll be fast enough for my taste and the MPG with Ethanol will at least be better than the Gasoline MPG was with the Rotary.

With the right engine the cam profile doesn't necessarily need to change just the intake/exhaust system and gearing. Anything to do with a FWD gearing usually requires dropping the whole front subframe and pulling the transmission, unless you get lucky enough to have OD accessable like the Geo Metro.

Another way to harness a turbocharger in the exhaust is to use more EGR flow into the intake. EGR is just burn carbon and such and doesn't add heat to the combustion process but just takes up space in the chamber and cools the heat of combustion down. A study I've read suggests the upper limit is 40% EGR recirculation before the engine starts to have problems. If you mix lean Air:Fuel Mixtures with EGR you can still maintain exhaust temperatures but I just haven't delved enough into it to figure out the tuning aspect. How do you even control EGR? Theoretically though this means you can have maximum Volumetric Efficiency at 75% throttle if you're using 33% EGR and the mixture can be leaner than Stoich for a better BSFC. And a better part throttle fuel efficiency since throttling has a major effect on Fuel Economy.

While you're considering this you should know that a turbo charger adds load and works off of a load. A turbo usually doesn't add much air pressure to the intake side at low RPM because it doesn't have enough exhaust pressure to do so. A small turbocharger will build pressure faster but will max out at lower levels than a bigger turbo charger. And individual turboes are designed for different maximum levels of pressure. A factory turbo engine usually has a lower torque peak because the cam can be lower profile because the air pressure is high enough. If you build this, you're going to want a wastegate or boost controller to keep the resistance low enough that the turbo charger doesn't put too much load on the engine or increase the engines power beyond what you need, I'm not incredibly knowledgeable of the specifics at this point but the EGR works into this too in small displacement turbocharged engines by cooling down the combustion during part throttle allowing the turbo charged engine to run leaner mixtures at part throttle or even 3/4 throttle with less overall power as a result therefore more throttle less fuel consumption.