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1G So I swapped to a big garret t28

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Dethh117

Proven Member
56
13
Aug 3, 2022
Tennessee
The car was running 18 psi previous to charging the turbo. Was on stock small 16g. I swapped over to the big garret t28 from extreme psi. Now running the same boost and everything. The car wants to stutter and hesitate when hitting boost in 3-5 gear. I suspect a lean condition? Boost guage ( auto meter 30-20) shows 18 psi. With no issue holding it just a hesitation. I know timing and afr can effect this. Adjusting the throttle body adjustment screw seems to make an impact on the situation. What are my options? Thank you in advance.
 
So your mod list says 550cc injectors but no engine management system.

So you need to turn down the boost because the ecu is seeing too much air flow compared to your old turbo and thinks its a stock fuel system, so the ecu is cutting fuel to prevent what it considers catastrophic engine damage

So you need to get an engine managment system like ecm link and then get a tune, or turn down the boost to 14psi
 
I just don’t get how the old turbo could turn 18 psi fine. Lol but I’m not the smartest about turbo setups either
Different turbochargers move different amounts of air at different boost levels. A 16G at 18 psi does not move the same amount of air as a T28 at 18 psi, so it will demand a different amount of fuel for that airflow change. For something as significant as a new turbocharger, a retune is required.
 
A small 16g and t28 are almost the same turbo. You can turn the boost down to test the fuel cut theory but I suspect something simple like a boost leak or ignition breakup.
He said he was on the "stock small 16g" so my assumption is that he didnt realize the 1g has a 14b turbo stock, or he replaced the 16g because it went bad and wasnt really pushing much volume as it should have because it was damaged

I mean im not sure why you would put a t28 on a first gen, you would have to change the intercooler piping orientation. So yeah im assuming alot, he hasnt even confirmed what kind of car he has or the other modifications
 
A small 16g and t28 are almost the same turbo. You can turn the boost down to test the fuel cut theory but I suspect something simple like a boost leak or ignition breakup.
See! From all the research I did. A lot of people have ran it without swapping ecu. Making mechanical adjustments and such

He said he was on the "stock small 16g" so my assumption is that he didnt realize the 1g has a 14b turbo stock, or he replaced the 16g because it went bad and wasnt really pushing much volume as it should have because it was damaged

I mean im not sure why you would put a t28 on a first gen, you would have to change the intercooler piping orientation. So yeah im assuming alot, he hasnt even confirmed what kind of car he has or the other modifications
I am a welder by trade so changing orientation took me an hour. Wasn’t hard to do. And yes I thought a 14b was a 16g but I guess I was wrong about that. My apologies.

Just to clear it up. It’s running a big garret t28 now. I have done any and all maintance from oil to 7es plugs. Timing belt. Freshly rebuilt head. Plugs wires. It’s all been touched
 
I am a welder by trade so changing orientation took me an hour. Wasn’t hard to do. And yes I thought a 14b was a 16g but I guess I was wrong about that. My apologies.
No worries, I guess right though

Your old 14b probably wasnt pushing as much air flow as it should have been when it was new

Change the boost to run 14psi and your should still feel like the car is much faster even at a lower boost

Or yes you could just run the vacuum source directly to the wastegate to run 12psi or whatever minimum is on that actuator
 
No worries, I guess right though

Your old 14b probably wasnt pushing as much air flow as it should have been when it was new

Change the boost to run 14psi and your should still feel like the car is much faster even at a lower boost

Or yes you could just run the vacuum source directly to the wastegate to run 12psi or whatever minimum is on that actuator
Got it. It was over boost. Tan strait off of actuator and had no issues
 
Just some food for thought. Any time you change the air flow you need to adjust the fuel especially with something as big as a turbo upgrade. A proper a/f ratio is gonna make the car run better and last longer with an optimal burn. Might want to install a wide band and something to manage the fuel with for future upgrades.
-Daniel
 
What fuel pump? Is it rewired? Stock untuned 1G ecus aren’t as finicky as 2G ecus are. I’ve run 20lbs on an untuned 1G with a 14b, and about the same on an eBay 16G stock ecu. So you shouldn’t be running into ECU issues, makes me think stock fuel pump or etc. Gotta be something like that.
 
Tomorrow I am going to dig into the electrical. What am I looking for on fuel pump? And it’s weird I ran lots of boost on the stock 14b but it is too much air that is causing the issue. Up to 14 psi I am fine. Anything over I start to break up on boost. However I’ve been tracking down a tach issue. Everything pertaining to it is new. The funny thing is when boost hits the tach glops. Which is a direct indication of a later year ecu being put in. I am hoping to god I have a dsm link inside. So tomorrow I will investigate the ecu. As well as the fuel pump.

Tomorrow I am going to dig into the electrical. What am I looking for on fuel pump? And it’s weird I ran lots of boost on the stock 14b but it is too much air that is causing the issue. Up to 14 psi I am fine. Anything over I start to break up on boost. However I’ve been tracking down a tach issue. Everything pertaining to it is new. The funny thing is when boost hits the tach glops. Which is a direct indication of a later year ecu being put in. I am hoping to god I have a dsm link inside. So tomorrow I will investigate the ecu. As well as the fuel pump.
Also. Plugs are gapped at .22.
 
Tomorrow I am going to dig into the electrical. What am I looking for on fuel pump? And it’s weird I ran lots of boost on the stock 14b but it is too much air that is causing the issue. Up to 14 psi I am fine. Anything over I start to break up on boost. However I’ve been tracking down a tach issue. Everything pertaining to it is new. The funny thing is when boost hits the tach glops. Which is a direct indication of a later year ecu being put in. I am hoping to god I have a dsm link inside. So tomorrow I will investigate the ecu. As well as the fuel pump.
Boost doesn't equal mass air flow. As already stated 18psi on a 14b is not the same as 18psi on a 16g or t28. It is about the MASS of air not the pressure. Without knowing what yiur previous air/fuel ratios were its difficult to make an apples to apples comparison. There is more to this equation than you are considering. You have almost certainly changed the operating conditions beyond what the stock ecu and fuel system can handle. For what its worth on the fuel pump a bigger fuel pump does not change air fuel ratio. It does nothing. It merely keeps up under high flow demands where a stock pump doesn't. You likely are pushing the limits now on fuel pump demand, airflow and possibly injector limits.
 
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For whatvits worth on the fuel pump a bigger fuel pump does not change air fuel ratio. It does nothing. It merely keeps up under high flow demands where a stock pump doesn't.


Not sure what you’re trying to say here. But with the stock 1g fuel pump even rewired anything above 16lbs has a direct effect on AFRs because it can’t keep up.

Changing the fuel pump out to a higher flow unit(rewire it too just for safety) will allow the ecu to properly command the stock AFR and Timing numbers. If he’s on a stock fuel pump it could definitely be causing some lean stutter up top due to increased CFM or Lbs/min from the bigger turbo.

Again, personal experience with that. Anyone that HAS a stock 1G ecu and fuel pump combo, throw on a wideband and turn the boost up past 16 and watch your AFRs and let us know what it does. It won’t hit fuel cut, and with the 14b (and how rich the stock 1g maps are) it’ll start leaning out but not enough to make it stutter.

Now do the same thing with a T28 or a 16G. Different story. Anything above 14lbs sends AFRs into “too lean for such aggressive timing” areas and will stutter and pop like crazy.

Not guaranteeing it’s the fuel pump, but on a stock 1g when you’re pushing anything above stock boost levels, fuel pumps 100% will change AFRs. Again, not heresay. Personal experience.
 
Not sure what you’re trying to say here. But with the stock 1g fuel pump even rewired anything above 16lbs has a direct effect on AFRs because it can’t keep up.

Changing the fuel pump out to a higher flow unit(rewire it too just for safety) will allow the ecu to properly command the stock AFR and Timing numbers. If he’s on a stock fuel pump it could definitely be causing some lean stutter up top due to increased CFM or Lbs/min from the bigger turbo.

Again, personal experience with that. Anyone that HAS a stock 1G ecu and fuel pump combo, throw on a wideband and turn the boost up past 16 and watch your AFRs and let us know what it does. It won’t hit fuel cut, and with the 14b (and how rich the stock 1g maps are) it’ll start leaning out but not enough to make it stutter.

Now do the same thing with a T28 or a 16G. Different story. Anything above 14lbs sends AFRs into “too lean for such aggressive timing” areas and will stutter and pop like crazy.

Not guaranteeing it’s the fuel pump, but on a stock 1g when you’re pushing anything above stock boost levels, fuel pumps 100% will change AFRs. Again, not heresay. Personal experience.
I was trying to convey(poorly) that after all these years people do not understand the difference between larger fuel pumps and larger injectors. I think you hit it spot on. OP has likely run out of pump among other things.
The point I was trying to make is people add fuel pumps thinking it changes air fuel ratio and it doesn't UNLESS the pump wasn't keeping up. Hope that makes sense for the OP.
 
I said the same things in post #2 LOL

The ecu is too stupid to actively calibrate a new air fuel ratio. Its stuck in a programming equation where all of the components are factory, and the only thing it can actively see and calibrate is the incoming air flow. The front oxygen sensor is a narrow band and barely counts as a heat reading

So the only thing your stock ecu sees is that the new turbo is sucking way more air than the fuel system is calculated to accept and says danger, and cuts fuel to prevent damage

You have to reprogram the ecu to see a new power equation, with new fuel and airflow variables

The only way to edit the ecu is to get an ecm link ecu, or trick it with a piggy back air fuel controller like an safc

Once you start playing with fuel and air settings you have to start making sure you calculated those changes correctly, by monitoring air fuel ratio with an aftermarket wideband air fuel gauge.

My personal opinion is too much fuel has killed more of these motors than too much boost ever had. Your start plopping bigger injectors in these cars and flooding the crank case with fuel and spin a crank bearing and the next thing you hear is rod knock.
 
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So, I pulled the ECU. I have an EPROM and from my humble understanding those never came in 1st gens. Especially 90 Eclipses. So I see where somebody had to change wires and I do in fact have the tach bounce in boost. Here is the guts. And a few other pictures

I could use some help to make light of.

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The piece you first pulled out kinda resembles what are in my 2g cars and is for the keyless entry remote. I can’t be sure though as I’m not a 1g guy but it looks similar and in the same spot as my 99’s.
-Daniel
 
Mine don’t connect with “pins” as much as it’s more of a thin piece of metal that makes contact with the chip. Do you have an alarm and keyless entry? Again hopefully a 1g guy can chime in I’m just speculating at this point as it looks similar and is close to the same location.
-Daniel
 
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