Evo boost Taper
 

Curious as to why Mitsubishi saw fit to engineer the rapid boost taper post 5.5K rpm into the Evo in the first place. Any insight would be appreciated.

Roger

05 Evo VIII
Planning to start with Vishnu Xflash or Works P2

I WAS JUST about to post the exact same question... bump for ya...


also, is a boost gauge and MBC to eliminate this taper ok for the very first mods? or should you start with turboback exhaust first? im looking to do my first mod (after boost gauge) and read somewhere that MBC is not good to do as a first mod...

i dont know for sure, but i would imagine it was to take some load off the engine at high RPM as a safety measure and so that the engine doesnt blow...

I could understand if it was considered necessary for engine longevity but there seems to be plenty of evidence that modified Evo's without the taper are reliable and I believe Mitsubishi Motors in the UK now extend their warranty to the FQ derivatives which run higher than stock boost (not sure if they still taper or not).

It is a safety precaution. This along with the pig-rich fuel settings gives Mitsubishi a chance to warranty the powertrain up to 100K.

It is a much more nessicary safety precaution than the stupid pig-rich fuel... and it's hard to get rid of it 100% it always tapers a pound or two or more depending on the gear even with an MBC

Yeah, it's a definitely to try to save the longevity of the engine. ~20PSI is A LOT of boost, especially for a "stock" car, so as the RPM goes up (increasing stress on the reciprocating parts), they let the boost taper to ease the stress. On N/A cars with aftermarket turbo kits, you will be lucky if you can keep the engine together at 12PSI without heavily upgraded internals. Removing the boost taper will improve your power, but will definitely have an impact on engine life. But, hey, it's not like you bought the car because you want something that will last until you are old and don't need a car anymore... you bought it to have some fun, so go for it :thumbup:

I think as a stock car, the Evo has the highest boost I've ever seen. I don't know of any others under 75K that have higher boost.