I traded my 2002 Honda S2000 for my new EVO. I know I have heard this mentioned in some other threads but I have never heard an explanation. I mean I know S2000's are all top end but that car would pull all the way to redline. I have owned every Japanese Supercar sold in the US and all that were turbo's always had great top end but once the EVO hits about 5000 RPM's it seems to level off. I even bought a manual boost controller and set it to 19psi and it still feels like I'm making no progress past 5K RPM's. Is the turbo running out of air or is the exhaust restricting the vehicle so it feels that way, I mean what's the deal?

 

Something must be wrong with your car, because mine pulls to redline, even in 5th.

 

I feel a little lag after 6K RPM why

 

its because the japanese designers know there are a buncha idiots in the us that dont know how to treat their cars so your air fuel curve looks like this "\" instead of this "--" basically the car runs super rich after like 3500 rpms, a simple ecu remap will solve your problem nicely, a downpipe and exhaust if you have some extra cash will make your car pull so hard you wont recognize it, i reccomend either www.vishnutuning.com to setup a good piggyback for you, this is the answer to your problem, i drove one with the ecu and exhaust, not even downpipe, and it pulled harder between 6000-7500rpms than it did at 5000 which is where you probably feel your best power currently... good luck
P.S. make sure its a 3"downpipe and 3"exhaust ;-)

 

Also...what octane fuel are you putting in the car? There is a noticeable difference in the way people have been describing the acceleration of East coast vs West Coast Evos......and it has a lot to do with the fact that we can easily get 93 and 94 octane fuels here on the EC.

SC~

 

Boost falls off at higher RPM's also.

 

Yah, I've noticed the same thing, my EVO seems to fall off in power where I would expect it to excel.. Anyway, here's my observations, which go really closely with everyone else..

A/F mixture is FAT (REALLY Rich above 4800 RPM) boost drops off suddenly due to a bypass solenoid at around 5000 RPM also.. my car seems to have 19psi and drops off sharply to 16.5 over 5000 the combination of rich mixture, and dropped off boost, will hurt top end performance.

Now, my 19psi is a little higher than others are seeing with a stock car.. I'm not certain if its the location where I'm measuring the boost signal, compared to others, or whatnot.. but I've been told that stock boost is 18.5 or so..

 

Do not forget that this turbo is not made for the topend. Th car is arally car, not a drag car.
In a case of a stock Evo, everything matters - stock exhaust is restrictive, stock airbox is restrictive, ECU runs rich ( need a HKS -AFR). Put a full exhaust, HKS intake, and a air/fuel controller, and you will se ethe difference.
What other Jap cars are you comparing it to?
Teh EVo is comparable only to a WRX and Eclips ein stock form. The Z, Supra,a nd RX7 pull more power with only 7-9 psi. They cannot be a measure for you.

About running rich - ALL factory ECUs are detuned. We cannot expect mistubsihi to tune the Evo to a perfect 11.5 AFR on 93 gas in NYC, and tehn the customer drive sin in CA with 91 octane and 100 degrees outside at full boost.

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Also running flat in the higher RPMs has to do with the twin scroll turbo as it is more restrictive to airflow, however it excels in lower RPMs. With a normal turbo you would notice a considerable difference in the top end, but you would lose a good amount on the bottom end.

The turbo is only one of several things in this case though that appears to make the top end feel flat. The important thing here though, is that the acceleration G's are not diping down as the RPMs rise, but remaining constant as the car is accelerating. This characteristic will make the car feel slower then it really is, causing the car to be decivingly faster then it feels.