Project EVO MR - Engine Bolt Ons Part 2

By Cheston Chiu

In the last edition of Project EVO MR, we were at Cobb Tuning SoCal in the middle of bolting on a bunch of parts.  As you may recall, we are wanting to give our EVO a nice boost but don't want to get too much beyond the basic bolt ons because we don't want to stress our SST transmission too much.  We want to be able to daily drive our car with occasional track use without problems.

So far we are working on getting the AEM intake, ARC intercooler, Cosworth intake pipes, AMS downpipe, MXP exhaust and the Cobb boost control solenoid with Access port all fired up before some tuning to make it all work.  How much power are we gonna make?  Let's take a look and see. 

With the downpipe and O2 housing removed, the OEM turbo is now exposed.  Since we don't want to make horsepower more than the low mid 300 whp range the stock turbo will do just fine.  You can see how the stock turbo has a flange that separates the wastegate discharge from the turbine discharge.  This typically helps with spool and gives a little more power than having the flows mix right away.


Check out this comparison between the AMS Widemouth downpipe and factory pieces.  Although it's not super obvious in the picture, the AMS part has an entrance nearly twice as large as stock with a much straighter flow path into the downpipe.  The part probably flows twice the volume as stock.  A flex pipe keeps stress from the engine rocking on its mounts from breaking the pipe.


The AMS widemouth comes with an extra bung for another O2 sensor in case you wanted to run an AFR meter or put your A/F sensor high in the system for tuning.  The O2 sensor housing part of the downpipe is investment cast stainless which allows for more freedom in design than if it was fabricated from pipe section.  This allows for the best possible flow path from the turbo discharge.  The part has nice thick flanges which ensure a long leak free life.


In our case, Danny just used the AMS supplied plug to block off the extra sensor port..


The AMS downpipe installed.  It's a big, huge and straight shot to the MXP exhaust.  As you can see, the extra O2 sensor port is in a good place for access while tuning.


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Dusty Duster
Dusty Dusterlink
Tuesday, June 18, 2013 4:04 AM
"On a car that uses a aass airflow meter it is important to recirculate the compressor bypass air. Simply dumping it can cause the engine to stall or stumble as dumping metered air overboard will make the engine run way too rich."

This is true if your MAF sensor is located immediately after the airbox, which is where most OEMs place it. However, if you relocate the MAF sensor to immediately before the throttle body instead, you can still utilize an ambient-venting blow-off valve, since the air is not metered until right before it enters the engine. Obviously the ECU needs to be re-tuned for this.
Tuesday, June 18, 2013 5:56 AM
Instead of having the big belmouth, the earlier Evos and DSMs have the wastegate flow path divided from the main exhaust further down into the elbow coming off of the turbo.

Dividing the flows is beneficial but the bellmouth has more area. I wonder which is better? The bell mouth could be for performance or it could just be cost cutting.
Mike Kojima
Mike Kojimalink
Tuesday, June 18, 2013 8:08 AM
Sampling air close to the TB causes swirling turbulence that can throw the MAF off.
Dusty Duster
Dusty Dusterlink
Tuesday, June 18, 2013 9:24 AM
Yeah, you have to have a good 12-16" of straight pipe between the MAF sensor and the TB.
Dusty Duster
Dusty Dusterlink
Tuesday, June 18, 2013 9:26 AM
It's mainly done on high-boost, large-displacement V8s with centrifugal blowers. Most of those guys could care less about driveability.
Tuesday, June 18, 2013 10:32 AM
What are the PIAA units in front of the transmission (you can see them on page 4).
Tuesday, June 18, 2013 10:32 AM
(EDIT): I meant the radiator...
Tuesday, June 18, 2013 11:27 AM
Protodad: The PIAA units are my sport horns. PIAA 85110 (115db) 400HZ + 500HZ Sports Horn.. the OE Mitsu horn on the Evo is pretty laughable... I did a direct OE replacement and just center mounted the two horns.
Thursday, June 27, 2013 6:40 PM
About how much racing fuel would you recommend mixing with 91? Something like a ratio of 8 to 1?
Tuesday, July 02, 2013 12:59 PM
Wait, one of the captions said the tuner eliminated the speed limiter and raised the rev limit...then in your interview, Mitch says the speed limiter is set at 315 and the engine doesn't make more power so he doesn't change the rev limit? Which is it? =)
Saturday, February 20, 2016 3:33 PM
When does that trans and stock ecu get thrown in the dumpster? For a evo9 setup and an infinity of course!
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