Red top sr20det break up issue

[Trvpstar]

Hello all, I recently picked up another hatch after all the craze. This is my 3rd 240sx but 1st sr20det. I bought the car just cranking (bone stock) all it needed was an ignitor chip, easy fix. I got carried away and upgraded to a FMIC, 4? exhaust (accidentally got it instead of normal 3?), isr turbo elbow, isr 255 fuel pump. Ever since I upgraded the turbo elbow my car has been wanting to break up at 5k rpm. Just before that it drove fine and boosted well, the car has new plugs. Do I need to upgrade engine management at this point? I?m running stock t25 and stock boost, I?m not looking for more power, should I just throw the stock turbo elbow back on and call it a day?


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[Kingtal0n]

you need a wideband installed 3 to 4 feet downstream of the turbine.

Read the wideband to see why it breaking up.

Likely there is some air leaks. Perform a pressure test to find all leaks.

The maf sensor will not work properly if there is some air leaking.

Another issue is the maf placement, critical to have a very smooth airflow through the maf sensor. You may have disturbed its placement when you change some parts.

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When you say "turbo elbow" if you mean exhaust outlet, that will not hurt performance any as long as it doesn't leak any exhaust gas.
It is very unlikely that this type of part will causing breaking up. Improving exhaust flow is okay for turbo engines.
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Breaking up could be related to fuel loss. You need to read the wideband to see if it is losing fuel. With T-25 turbo the max boost should be is around 10psi with a large intercooler, due to the age of the turbo and other unknown variables this is the best recommendation.
Make sure boost is 10psi or less at the intake manifold and read the wideband to make sure a/f ratio is between 11.2 and 11.8 at wide open throttle. Sometimes the OEM Ecu will give 12.2 or 12.3 for the T-25 turbo at 10psi of boost so this is fine. But not for 12+ psi

If the a/f goes lean the engine will break up, misfire, etc.. and then a piece of piston will break finally if you keep doing it.

You also need to check the engine timing and make sure it is correct or similar damage will occur.
Also, make sure fuel pressure is correct at idle and wide open throttle.
You should put new spark plugs NGK BKR7ES "copper plugs" ($2/each) and gap to .032" to .035" carefully. Put a very small tiny bit of anti-seize lubricant on the threads very far away from the tips of the plugs. Do not get anti seize on the plug tips , just for the threads.
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Since the turbo is OEM I would definitely run the OEM parts on the engine. Each "larger" part you change on intake side is going to reduce performance. The large front mount intercooler for example will reduce engine performance with such a tiny turbo. Intercoolers do NOT add power, they remove heat energy from the air and cause a resistance and volume based head loss from the turbo, which costs power and energy (Efficiency -> economy lost).

For larger turbos the power lost due to intercooling can be made up for by increasing wheel speed of the turbo (and flow rate) but the tiny T-25 cannot produce more wheel speed because it is so very small.

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[Trvpstar]

Gotcha, just called my local shop to see what their input is in it and they think I may be over boosting and not enough fuel to feed it. They recommended I get a boost controller and an AFR gauge to see, but my thought it if I have a 255 pump wouldn?t it be enough to feed it even if it was over boosting?


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[Trvpstar]

Issue fixed, added a boost controller at lowest setting. No more over boosting and break ups


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[Mikester]

Originally Posted by Trvpstar

if I have a 255 pump wouldn?t it be enough to feed it even if it was over boosting?


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No.

The fuel pump does not dictate how much fuel finds its way into the cylinders, it's job is to move x-amount of fuel through the system... The FPR regulates the fuel pressure at the rail, the pump just provides the fuel. How much fuel the injectors are physically releasing, at what interval and for how long is all part of the tuning in the ECU.

A wideband will give you a real-time view of your AFRs. What you would theoretically see during overboost is a lean reading, regardless of what pump you have installed in the tank.