Quote:
Originally Posted by oil pan 4
If the gasoline fully vaporizes at 250°F why not heat the air up to around 250°F.
On my old carburetored camaro the carb would be at about 200°F and the air would be around 160°F to 180°F with a stock intake manifold and air filter drawing air from under the hood.
Didn't really see any improvement in fuel economy until I leaned out the cruise mixture.
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He then added a turbocharger to compress the over expanded gasses to gain usable power and achieve 50+ mpg. However, you have to compare that to the base vehicle which could achieve 39 mpg on the freeway. It is less startling when viewed that way.
The 78 Dodge van I worked with had a 360 V8 and a Carter Thermoquad spread bore that would tip the secondaries too early for our use . We replaced it with a Holley spread bore and tuned it so that the secondaries came on only at wide open throttle settings. Then the primaries were leaned past the 18:1 AFR factory settings to about 20:1 AFR. The engine started to run ragged. By using a Briggs & Stratton single throat carb whose intake tube passed over the hot drivers side headers, we introduced a hot gasoline vapor mix underneath the main Holley in a replacement phenolic spacer with passages machined into it. This allowed the primary carb throttle to be closed for the most part and the engine could run nicely at 20:1 AFR. We did not have wide-band O2 sensors available to us back in 1979 so we used the factory procedure of propane addition referenced to a chart. The hot air snorkel intake that was controlled by a bi-metal thermal switch was replaced by a simple cable actuator that ran to the dash. The hot air basically ran all the time. It worked well in most cases except it reduced over all power when the secondaries kicked in and you wanted cold air.
In this configuration, the vehicle could haul a bunch of people and luggage with fuel economy hovering around 19-20 mpg on the flat at 55 mph ( national speed limit in those days). The addition of an Edelbrock Digital Water Injection kit impacting on a hot slug of zinc plugging the EGR crossover passage and providing a bit of hydrogen, allowed us to tune the primaries a bit leaner and our mileage topped out at 21 mpg.
The only thing remarkable about the whole exercise was the fact that this was a 15 seater van full of teenage campers and with luggage packed on top. The 55 mph speed limit and 80 psi truck tires had a lot to do with it, but we like to think the engine mods helped too.
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