That really depends on how big the turbo is and when is going to run out of its breath! The one that I have on my car (Forced Performance Big T28 can hold 21 psi all the way to the red line (8k RPMs). 16G turbos that are available here in the US are still smaller than those one the latest EVOs and are capable of at least 21 psi all the way up there as well!

You might be onto the something here. I have never seen the twin scroll turbo so far, but if it is capable to flow well with lower flow, that has to take something off on the high end side.

Fedja

 

quick question for all the 1G/2G 4G63 owners...how is boost controlled from the vehicle stock?...ECU?...

 

No ECU control since ECU doesn't know what boost we are running. ECU only guesses what boost is present at a time. There is an interference regarding the boost level between the 3k and 4k RPMs, where boost control solenoid flickers and slows down the boost increase.

Otherwise, boost control on the DSMs is purely mechanical. Size of the restrictors that are in the boost control lines, preload on the waste gate actuator and size of the bleed hose affects those things.

My guess is that EVO is using the same way to control the boost. Unless there is a positive pressure sensor somewhere, which would give a chance to the ECU to do something about it. Otherwise, only RPM related interference will be possible!

Fedja

 

IT seemsto that boost is being controlled by the ecu. That probably happened when the epa tests were not passing, therefore MItsu decides to lower boost and therefore lower emmisions. AT 16lbs full 271 hp is made, so I wonder if a full 19lbs would be available with a simple ecu swap- that would probably put as at close to 290 or more hp. just an idea!

 

thanks for the thorough answer MrAWD...I didn't think that older 4G63 were controlled by the ECU...do you remember from your stock days if the boost pressure dropped @ redline?...or was it consistent..

 

Well, there is a difference between the 1G and 2G cars, mainly due to the different turbo that was used. 1G cars (equipped with TDO5 14B) where able to hold the full boost (I think 11 psi or something) all the way to the redline.

2G cars came with a freaking T25, which was way too small and it couldn't keep up with the engine needs at higher RPMs. Stock boost was at 14.7 psi, but most of the cars in the stock trim didn't get more then 13 ever. That would be up to the 5,500 RPMs where boost would start dropping down to about 8 psi at the redline.

There is also another phenomenon that was mentioned to me by the friend of mine just recently. The thing is that at the higher loads, pressure that turbo is creating is also higher and that seem to have an effect on the waste gate actuator, which slowly starts to open up and drops the boost as well.

Another problem was also due to the increased pressure on to the flapper valve (one which stops exhaust gasses to go to the waste gate opening), valve would start to opening as well, which caused less pressure on the turbine and lover boost as well.


Fedja

 

hehe...thanks again...I had a feeling you were going to mention the 2G's "T too small"....

 

So in your opinion will just a CAI increase the high RPM boost without having to touch anything else?

 

First, I am assuming that CAI goes for the Custom Air Intake. Then, if my assumptions are correct about that being very restrictive, than opening that one up will unleash lots of power. Of course, so far was using a fuel cut as a defense mechanism once you go over the amount of air they specified to be too much for the stock engine parts. So far things like AFC (or its flavors), DSM Link, TMO Chip, or any other aftermarket Engine Management System, would solve this one.

The thing is that we can just guestimate what will work and what not. Once we actually get to see the car and look underneath its skirt, things are gona get much more interesting!!

Also, this is kind of true for any turbo charged car (with exception of those that use the MAP instead of the MAS). Opening the flow for the air on both side of the engine (intake and exhaust sides) will be very beneficial! From the size of that turbo, opened system should be able to make around 350 HP at 20-22 PSI without much of a sweat! How much of protection against that has in its sleeve is left to be seen!!!

Fedja

 

what i dont understand is that since 19psi is pretty damn high, why does the Evo only have 271hp with such a great amount of boost?

 

271 HP happens to be at 6500 RPMs where EVO has about 16 psi of boost!


Fedja

 

Probably because it's tuned for the U.S. That can include emissions and fuel specs found here versus Japan or Europe. So they may not have as agressive of ignition timing, valve timing and duration, a more restrictive intake, more restrictive exhaust (i.e. more cats), different air/fuel maps in the ECU, etc. All of this would help contribute to "lower power" than the older Evos.

 

first off....the stock setting on the 2g eclipse or talon is not 14...it is around 11-12. Also the EVO'S BOOST IS NOT GONNA BE CONTROLLED BY THE ECU! I know this almost for a fact. If you look in the manual that came out for the techs....the pdf file we have on here also. It shows how boost is controlled, just look poeple. It is purely mechanical just like said before.

 

i hope you're correct favre95...

 

Hmm, I would check those two pictures (that are from the official service manual, btw) before getting that excusive

Really!! Maybe almost is not good enough here! Unless you have a special version of the training book, would you tell us where did you find that information about the EVO? Page number? Whatever.


Fedja