Originally posted by 1991 560 SEC
I belive you can put a bigger Throttle Body,with in reason with no other mods. The engine management system should adjust to the higher volume of air. Just as it compensates For different altitudes.
Would it be better with different cam, exhaust, and injectors? Yes, but by itself it will probably give a 15 hp increase.
It`s done all the time.
Is it done all the time on the M103 engine? The fuel system may compensate for any increase in intake air flow, but I seriously doubt 15hp is possible. The cam profile would remain the same, and therefore intake valve timing would still be a limiting factor.
Also, without opening up the exhaust to allow for the increase in air flow, you'll see little or no gain.
This method works for "strangulated" engines that have purposely limited from the factory by reducing air intake flow.
The cheapest way to make more HP in a 300E is to sell it and buy a 400E. The price difference in the used market is less than even the cheapest HP modifications. Also, your modified car will suffer terrible re-sale, and add to your cost of horse-power.
When I was racing, we saw guys all the time working on intake air flow, ignoring the rest of the path. This only works on a few engines. To get a nice running street engine with more power, you'll need to keep everything in harmony.
If the 300E is too slow for you, then prop a "for sale" on 'er, and start shopping for a V-8. If you have money to burn, keep the 300, and start modifying...