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75% throttle engine/turbo governs?

I was curious if there is a built in limiter on how much boost can run on the 91 vr4.

Everything is stock except:
16g big turbo
titanium valve springs
hks cams 272
balance shaft elimination
Turbo back 3" exhaust
Stock ecu, sent off for refurbishing just to be safe
Complete engine restore: barrings, rings, etc...


I have not increased boost past 7psi but for some reason its almost like the ecu thinks there is too much going on and it stops fuel to the injectors as to keep the engine safe. But this all started after turbo upgrade. OEM 16g out of talon or eclipse i forget...
It pulls great, but I haven't been able to fully unleash her.

Is this common?


Will a boost gauge, controller and turbo timer have any resolution?
 

Jesus_Negros

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Jan 7, 2012
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2,344
Location
USA
So you dont have a mbc?
And still on stock BCS?

7psi aint sh*t on a 16g hard to imagine what that ight feel like lol
 

Terry Posten

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Dec 16, 2003
Messages
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Location
Davenport, Iowa USA
Very common. You are reaching "fuel cut".

However, stock boost is around 11psi. The ECU shuts down around 14 psi but larger turbos can cause cut sooner if everything is flowing good.

How are you seeing only 7 psi before you get cut? Hopefully you have a good manual PSI gauge and not using the dash indicator.

To explain a bit of what is happening. The ECU is givin a reading from the MAS so the ECU can determine how much fuel to inject to keep the mix proper (taking into account RPM, throttle position, etc...). The ECU has a pre-programmed "map" that it uses to reference and when you pull too much air through the MAS (bigger turbo) that it goes over the "map" the ECU protects the motor by killing the spark.

That is it in a nut shell.
 

I was told stock was 7 with the 14b, and assumed it would change...

Okay so 11psi, how do I go about extending the limits?

Chip? 190 fuel pump?


Thank you for the explanation btw, it makes complete sense now
 

Terry Posten

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Location
Davenport, Iowa USA
Quoting Lennydrvs:
I was told stock was 7 with the 14b, and assumed it would change...

Okay so 11psi, how do I go about extending the limits?

Chip? 190 fuel pump?


Thank you for the explanation btw, it makes complete sense now



Those questions can take hours to explain your options. It all comes down to money and how adjustable you want your setup to be.

If you want, call me tomorrow night after 8pm CST and I will go over your options. PM me if you want my phone number and want to chat.
 

jepherz

Staff member
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Aug 8, 2004
Messages
7,877
Location
KC, Missouri
You'll need a chip bare minimum to get around the fuel cut. Any other solution to fuel cut with the factory ecu is a short cut and not a good solution.
 

beaner

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Joined
Jun 22, 2005
Messages
1,562
Location
b'ham, mi
If you are getting fuel cut at 7psi on a 14b, something is wrong with your car. Throwing aftermarket parts and chips at it will fix nothing.

Fuel cut is kinda scary when it happens and you nearly put your forehead into the steering wheel. Maybe you're mistaking fuel cut for way low boost. Does the car just stop pulling but continues to rev? I think you need to describe your problem better.

I would do this. Then this. Then this.

Try it out and report back.
 

Terry Posten

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Location
Davenport, Iowa USA
He has a 16g with 272 cams.

He is flowing quite a bit more air than a stock setup.
 

Terry Posten

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Dec 16, 2003
Messages
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Location
Davenport, Iowa USA
He does not know what psi he is at because of bad advise from the previous owner.

He is still using the stock LED lights to gauge things by.

So, let's keep things simple, and light hearted.

We'll get things running good.
 

gramkrakr89

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Jan 25, 2010
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Bunker Hill, WV
Things like this just need some time for figuring all out, especially when PO's were vague (or sometimes clueless). Shouldn't be too big of a deal.
 

beaner

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b'ham, mi
>He is still using the stock LED lights to gauge things by.
Ah. That changes everything. He definitely needs a boost gauge to figure out what the boost is really at. Even still, around stock psi it should be totally fine. So maybe boost creep, but I still think a boost leak test will reveal the culprit.

Give us more info OP. /ubbthreads/images/graemlins/tongue.gif
 

Terry Posten

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Davenport, Iowa USA
After spending an hour or so on the phone, discussing the pros and cons of the options. He has choose the chip route with a MAS upgrade.

His goals are modest for now to keep the mileage and reliability high so it can stay a daily driver.

He will need to source a:

482 MAS, 1g>3G harness, filter w/adapter, chip and socket job, mbc, and a vac/boost gauge.

He is staying with the stock injectors and pump so his boost will be limited to around 15psi. But it should run very well and be reliable with good gas mileage (as long as he keeps his foot out of it /ubbthreads/images/graemlins/devil.gif).

I can help him out with some of it, and the rest can be sourced here or on fleabay...
 

beaner

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Jun 22, 2005
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b'ham, mi
I guess we'll have to agree to disagree on what the problem is. His car is cutting out at 75% throttle on a tdo5h turbo at actuator/stock psi (assumed), so now he's flashing the ecu and upgrading the mas. I don't get that at all. The only difference with that mas and chip is the ecu can read more airflow. Great. A 16g/14b is not outflowing a 1g mas at stock psi. If the car is getting genuine fuel cut at that low of psi something is wrong. If the car is boosting way high to produce that airflow, something is wrong with his boost control. Maybe the mas/chip would compensate for that, but then he's on stock injectors and pump.

If it's just a boost leak I get your mod title. /ubbthreads/images/graemlins/laugh.gif /ubbthreads/images/graemlins/laugh.gif
 

Terry Posten

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Davenport, Iowa USA
I am not saying that he does not have a leak or two. But even when he checks/fixes leaks and verifies timing, his car still won't run the greatest without improving the MAS and code.

For under $150 he will be able to safely run 15PSI.
 

beaner

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Jun 22, 2005
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Location
b'ham, mi
Quote:
For under $150 he will be able to safely run 15PSI


>implying a stock car can't do that.
>implying the stock mas is overrun at 15psi.

He's trying to run near stock boost on pretty much a stock car with a stock turbo on the stock fuel system. He doesn't even have a boost gauge yet. His car is cutting out at 3/4 throttle. Please tell me why are you convinced spending 150 bucks on an evo9 mas and eprom chip will fix anything. I don't get it. All that changes is the range the sensor can read airflow. The stock sensor is not out of it's range at 15psi.

This thread has turned into backwards modding on a car that needs some simple maintenance.
 

Terry Posten

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Location
Davenport, Iowa USA
Because his car is NOT stock. He is running a larger turbo, a larger set of cams, a larger exhaust, and he has some (not all) piping done.

If he was still using everything stock, then yes, why mess with it. But he is clearly wanting to improve his car and the absolutely best way to do that is the route that has been listed above. With all things considered (money, time, reliability, skill level, etc...).

If you think that all a chip and MAS does is fix the airflow, then you are completely wrong. He does not want to stay at 12 psi. He wants to improve his gas mileage, throttle response, and more.

You have not been part of the phone conversations or the PMs back and forth over the last day or two. Your assuming maintenance has not been discussed.

Stop arguing just to argue. He wants to improve his car, not just put it back to stock.
 

beaner

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Jun 22, 2005
Messages
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Location
b'ham, mi
Quote:
You have not been part of the phone conversations or the PMs back and forth over the last day or two.


Exactly. A noob with 16 posts asks a question on the forum and you take it straight to pm and phone calls.

His few mods are not creating this huge airflow increase you portray. A 16g at 15psi might as well be a 14b at 15psi. He has a freaking stock unwired fuel pump dude. He is not outflowing the stock mas with that. You're changing it for no reason and ignoring the basics.

I'm sure the chip will delete the factory fuel cut feature, all will look great, and the boost will get raised. Have fun.
 
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