kyral

I just bought an Sr20det redtop (it uses coilpacks, i didnt think anything pre obd2 used coilpacks but w/e)
I went to change my plugs and noticed that cylinders 1 and 2 use red injectors (Guessing ka24de) and cylinders 3 and 4 were using a light purple injector (stock oem 370cc sr injectors)
Spark plug 1 and 2 had light carbon build up (looked good and healthy) and cylinders 3 and 4 had excessive carbon build up that left everything black on the tip of the plugs

So im thinking maybe the upgraded fuel pump is causing fuel rail pressures to exceed 3 bar. Causing the stock injectors to dump excess fuel, and making the lower flow injectors dump a seemingly more correct ammount of fuel because of the elevated fuel pressure?

Also the car kinda bogs at first if you push the gas to the floor, thats the only time it bogs is if you floor it, once its bogs though it picks up and goes (im wondering if this is caused by the ecu adding fuel thinking the engine is under boost when the turbo hasnt built up any pressure yet)
If you ease the gas on itll rev smoothly.

Any ideas what might cause the bogging

This is what ive gathered from lots of googling anyone know if this is all correct, wrong or have anything to add maybe?

ultimateirving

Some of the 370s come in different colors iirc. The q45 or z32 shared similar injector sizing. Just different colors.
Get a wideband and perhaps replace the plugs. Also the coil packs are notorious for going out.

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Z32 with lq4 swap
Desert Street Scene || Dssevents.com

kyral

I replaced spark plugs, and I believe theres a wideband already installed, not sure though. It has the aem afr gauge kit, i would think that would need to be connected to a wideband. I know the kit comes with a bosch wideband so im sure it has one
This is all new to me

But i know the red injectors have to be flowing less than the purple, the spark plugs told me so lol

I am kind of dumbfounded that the person who had this car previously went through all the trouble to hook up all these aftermarket parts and upgrades to put mismatched fuel injectors on the car

its not a ghetto hackjob, wiring harness is mess swap either. it looks like the guy did his homework who had the car before me

im gonna check to see if theres an aftermarket FPR on the car, if not get one and that should allow me to control the rail pressures
then get a new set of 370cc and go from there

So coil packs can cause alot of gremlins at the end of their life span?

ultimateirving

Ya the coil packs can definitely cause some problems. I had a set that would run and drive the car, but under boost would break up really bad.

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Z32 with lq4 swap
Desert Street Scene || Dssevents.com

jedi03

I have a good set of injectors from my setup, ran great before I pulled then, be glad to help a fellow zilvian! Just pm me and can work out details!

kyral

Checked today and no aftermarket FPR, so im almost positive that the walbro is creating fuel pressures that the oem regulator cant handle, which is why my engine and i assume many others, run rich.

vipergtsr1000hp

Even with a walbro pump, you should not be getting that gas mileage. Considering from the looks of your spark plugs, I recommend changing to a known working set of injectors. The coilpacks might be the issue when you're hitting boost but should not cause bad gas mileage when off boost. Also, your O2 sensor might be bad. Best to get a A/F gauge to check. Check for vacuum leaks, idle issues, etc.

SoundEfx

I think that it might just be the mismatched injectors causing the tune/ecu to act funny when in boost.

I say this because you said that if you ease onto the throttle, everything is fine. If you had a vacuum leak, it would misfire all the time.

The recommendation to change the coilpack and o2 sensor should be followed if you know that they have been on for a while. We are talking about a 25 year old car.

If the car is old enough to drink, ALL of the sensor should be changed....lol

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kyral

Thanks for the response, im gonna start with the injectors and a FPR. since it has the aem AFR gauge kit, which includes a new o2 sensor, installed. (but I will definately keep it in mind if problems continue) I think the injectors and FPR are gonna be the best place to start
thank you for all the reponses