Why Did Mitsu Restrict The Air Passage In The OEM

[Starfighterpilot]

A couple of weeks ago I had the OEM air filter cannister out of the Old Girl with lid and air filter off. For the first time in 22 years I REALLY started looking at the configuration of the cannister were the inlet air volute is tack welded to the side of the cannister.

 

I think to myself, "That volute should have a much bigger outlet hole where it's mated to the shell of the cannister." So I stick my hand in the cannister shell air inlet hole. Low and behold I discovered that the hole is only about 1/4 to 1/3 of the size of the volute were it mates to the cannister shell.

 

The more I think about this, the more it seems to me that MITSU intentionally designed into the OEM air intake system an Air Restrictor Plate to limit the performance of the Starquest G54B turbo engine.

 

It seems to me that if the cannister shell was opened up to match the volute size, a LOT more air could be drawn into the turbo (cuz the volute outlet opening is at least 3 times as large), and there would be less air turbulence.

 

I realize that there would still be a restriction of flow cuz of the size of the air inlet hole in the air inlet plate mounted on the wheel well and the size of the jumper hose to volute. But still, I think that the outside COOL air capacity available to the turbo would be significantly increased.

 

Has anyone ever cut this cannister metal out to match the configuration of the inside of the volute? If so, did you notice a difference in the Starquest's performance?

 

Or, why did MITSU design the air cannister air inlet plumbing this way with a built in restrictor plate?

 

The Air flow capacity of the OEM intercooler?

 

Or is the hole sized for maximum boost CFM capacity of the 12A turbo (and/or the Air Flow Sensor? I know I'm pulling at straws on this one).

 

I believe that the OEM fuel injectors have enough reserve capacity and the '88/'89 fuel maps could handle the increased air flow resulting from opening up the hole.

 

Confused. What am I missing here.

 

Or like I stated above, did Mitsu INTENTIONALLY limit the performance of the OEM stock Starquests by doing this?

 

For What It's Worth.

 

KEN

Edited August 7, 2010 by Starfighterpilot

[trackone]

Maybe for Admission standards or protocols they have to follow who knows.

 

But it is a very good question?

[SOTTY]

did Mitsu INTENTIONALLY limit the performance of the OEM stock Starquests by doing this?

 

For What It's Worth.

 

KEN

I looked in depth at this very same item in the past and i'm sure what you say above was indeed the case.

[StarquestRescue]

This may well have been the case. Another factor is the limitation of the stock mas. The accordion pipe, baffle, and air can all work together to limit how quick the turbo can spool. This kept the airflow signal more consistent and probably helped with emissions, drivablity and fuel mileage.

 

I always wondered why they put such big injectors on the cars especially the older ones. This was before the days of airflow based fuel cuts and the manufactures typically set the turbo cars up to drowned the engine with fuel if they were over boosted accidental or intentionally.

[AutoBodyGod]

Noise restriction

[Starfighterpilot]

Has anyone ever cut this restriction out to match the inlet volute?

 

Did you notice a difference in performance?

 

The reason I ask is I don't remember ever seeing it mentioned in SQC or any of the other Starquest websites over the years.

 

The only mod to the cannister I ever saw was cutting a big hole or a lot of smaller holes in the front side of it to let in more HOT engine house air.

 

For What It's Worth.

 

KEN

Edited August 7, 2010 by Starfighterpilot

[lionbull]

Seems to me Mitsu built these motors restricted through and through. The exhaust piping is the same size as a stock honda 1.6 liter. Restrictive intake with no plenum and 2 injectors. A log manifold that bakes the exhaust valves on a normal day so it does not excavate heat well enough. That manifold takes extremely long to cool off too, especially if you're using pump gas. Edited August 7, 2010 by lionbull

[Couth'nize]

They do it so you can get 360k miles out of the engine?

 

I think it may have something to do with the Karmen Vortex sensor. The airflow has to be just right to create the vortex effect to generate the best signal as it can be through out the power range.

[Starfighterpilot]

They do it so you can get 360k miles out of the engine?

 

I think it may have something to do with the Karmen Vortex sensor. The airflow has to be just right to create the vortex effect to generate the best signal as it can be through out the power range.

 

You may be entirely right!!

 

However, that raises the question of: If large holes are cut in the air cannister allowing a lot more HOT engine house air into the cannister, does that also screw up the Karmen Vortex sensor?

 

If so, you better start plugging those holes guys.

 

For What It's Worth.

 

KEN

[Shelby]

it a simple thing to built an air inlet cover to keep hot air from the air filter houseing,,but while driveing there is not that much hot air,, air is continously flowing into the area so hot air never has a chance to get in,,

 

you must be the only quest owner to not have open'd up the air inlet,, thats one of the first mods to do , i cut off the entire restrictor when i first saw it

[StarquestRescue]

http://sqperformance.forumcity.com/viewtopic.php?t=108

[Indiana]

It was still all about how the air flows through the sensor. Ours aren't photoelectric, they are ultrasonic.

 

http://www.rpw.com.a...cchk=1&Itemid=3

 

I don't want to jack your thread or anything but if there is anything you might gain from seeing more about how the MAF works and a diagram of it and since I still don't believe there is an "over run" possible on this ECU (maybe others) I put up a page for that

 

http://www.b2600turbo.com/ECI%20System.htm

Edited August 7, 2010 by Indiana

[Technology]

Did we travel back in time to 1995 or something?

[Indiana]

Ahhh, you didn't read what RPW said in that link I posted did ya?

 

Many have a 1G MAF crammed down into a K&N cone filter and many claim to have a MAF code and a crappy idle. So what the air can did with the OEM filter doesn't seem to be duplicated with a cone filter and no air can so they have a oval shaped K&N for those newer MAF sensors and I would think that K&N might have a filter shaped like our stock filter but with an end in it that might also solve idle issues and MAF "error" codes (that may have just came from some time the car died anyway).

 

That isn't going back to the title though that the air can was a restriction. I think it was another of those things that were adequate at the time for the stock setup to be reliable. There is always room for improvement over a stock setup, especially in an 80s car.

[StarquestRescue]

Ahhh, you didn't read what RPW said in that link I posted did ya?

 

Many have a 1G MAF crammed down into a K&N cone filter and many claim to have a MAF code and a crappy idle. So what the air can did with the OEM filter doesn't seem to be duplicated with a cone filter and no air can so they have a oval shaped K&N for those newer MAF sensors and I would think that K&N might have a filter shaped like our stock filter but with an end in it that might also solve idle issues and MAF "error" codes (that may have just came from some time the car died anyway).

 

That isn't going back to the title though that the air can was a restriction. I think it was another of those things that were adequate at the time for the stock setup to be reliable. There is always room for improvement over a stock setup, especially in an 80s car.

I read the link. Did you read mine?

 

I agree it is point less to have the discussion in some one else's thread with a misleading title for where the thread is headed.

[Indiana]

That wasn't intended for you and yes I read your link and there you have that oval ended MAF just like RPW is talking about that I posted in reference to and how that would have related to a stock air can and whether it is part of a restriction, which I don't think it is, or isn't when its purpose goes back to something to hold an air filter and the can design has the air all turn to the bottom of the can in the middle surrounding the MAF inlet then it enters from all sides at the same time into the honeycomb to be straightened out. You have attempted to solve the air straightening problem since you don't have the parts and can't use them and the people with stock air cans dump those and end up with a cone filter and go right in to what you tried to get away from. I think this all IS in regards to what the title is. He asked if it mattered and imo no it doesn't as that's not what the main purpose of the air can is and I showed a diagram of it.

[Starfighterpilot]

Indiana and StarquestRescue, great posts. I stayed up to 3:30 AM reading 'em. I think they filled in my gaps of knowledge on how the complete EFI's system truely works.

 

After reading all of the above posts & links I have come to the conclusion (maybe incorrectly) that cutting out this air cannister restrictor completely will have no effect on the ability of the honeycomb to create laminar air flow downstream of the honeycomb nor will it effect the ability of the ultrasonic Karmen Vortex sensor to produce the correct vortexes and correctly sense the true air flow volumn as a result, at any OEM boost level or air volumn. Am I right or wrong?

 

Based upon what Shelby stated above about making this air cannister mod as the first mod that he does, I am assuming that this will work with no problems cuz he continues to do it. DUH!!! It never occured to me to lok at this until a couple of weeks ago.

 

But, and this is off the wall, because of another comment posted in a link above, engine idle may be effected. If the Starquest idles smoothly and correctly before this mod, will it idle the same way after the mod? I think that the idle will not be effected because if it does not effect laminar flow downstream of the honeycomb & thru Karmen Vortex sensor at high boost air volumns, it should not effect the laminar low air flow at idle air flow volumn.

 

I'm just trying to cover all the bases.

 

But then again, I might be totally FOS in my understanding of this stuff?

 

Sounds to me like this is a interesting chassis dyno experiment. To see, with nothing else changed on the engine except going from an unmodified to a modified reamed out air cannister, what effect, if any, it has on the engine out put numbers and where in the RPM range the changes occur.

 

Hey you guys in GA want to have a dyno meet?

 

I'm just trying to cover all the bases.

 

For What It's Worth.

 

KEN

Edited August 8, 2010 by Starfighterpilot