Quote:
Originally Posted by Benfica7
What do you have done to the engine for 300/250? just curious...
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The Ecotec motor was available in the Atom for a limited time. Jay Leno bought the first, I have #94, and the car switched to the Honda Type R motor somewhere around #120. This motor was available from the factory in several power levels.
Brammo Motorsports (the factory that produced the car) hasn't disclosed all the details, but this is how it goes as best I understand it.
Along with the 300 level being crank and not wheel hp, a number of Atom owners have also felt that the factory was a little optimistic when stating this number (due to what many owners have seen when they've dyno'd). In general, parts that contribute to what this level motor offers: tubular ram's-horn equal-length header (that's port-matched pretty well), very short exhaust system, no cat, low-restriction muffler, all ceramic-coated. Dual-pass aftercooler option with high coolant capacity (radiator for aftercooler is in front of car, engine is in rear so lines hold a good amount), SPA fan dedicated to aftercooler with a second fan dedicated to radiator. Radiators are separated by 18" and not stacked. Motor and trans are solidly-mounted - there is no rubber in the mounts. ECU programming started out as GM Stage 3 and was optimized by GM specifically for this car and likely doesn't care one bit about mileage or emissions (amazing what you can do when that's the case), injectors and SC pulley sized to match, injectors are one foot from fuel pump & tank. There is a tiny alternator, and no a/c compressor or power steering pump to add to parasitic losses. Air intake is cold ram-air, no baffles or other sound control, force fed by the wind between driver and passenger's heads with a path into the tb & sc that's only about a foot long with a large K&N filter.
Since purchase, I've switched to a SmoothFlow modular pulley set up that's a hair smaller than the stock pulley, and fabricated a full 3" exhaust (compared to the stock 2.5") that's also Jet-Hot coated. I doubt that these two modifications have done all that much, but hey - every bit helps. A number of owners have had outstanding results going to water/meth injection next to run a bit more boost and this is probably in my future as well, mainly because it will greatly reduce temps & heat soak on the track. Owners that are certifiable have swapped the Eaton for a Harrop or gone to a turbo set up.
Photos of most of this stuff is available in the gallery on my website if anyone is interested in a close look at the layout and how everything is packaged.
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