Popping In Boost??

[cbh148]

So my ca18 has had this little popping issue that comes and goes when in boost. Well, I recently upgraded my turbo manifold to the CXRacing one, and now it's popping like crazy in boost.

Spark plug gap = 1.1mm
ECU is code free (code 55)
T28 at 10psi

I checked the o2 sensor feedback from ECU mode 2, and my red LED stays constant while my green LED blinks. I'm guessing this is a lean condition, according to this page in the FSM (which isn't exactly clear).

[cbh148]

Haha already fixed the popping problem. I think.

Still unsure about the signals given by the ECU regarding what the o2 sensor is telling it.

[float_6969]

What was it?

[cbh148]

found out my friend "borrowed" my car while I was gone to college, and he took the liberty of changing my plugs to try to fix the minor popping it had before (and in turn, created MAJOR popping lol).

he put in NGK v power 5's (can't remember the exact number) and they were gapped up kinda high at roughly 1.3mm

I bought some new NGK bcp6es and gapped them tight at .8mm and didn't experience any popping afterwards

not sure if the o2 sensor feedback is something I should be concerned about. I know my Nismo adjustable FPR has a little tiny vacuum leak to it, even though it's brand new.

[float_6969]

Popping under boost is usually ignition related. If gapping the plugs down fixes it, you're nearing the limit of the coil packs.

You can also get popping in boost if you're lean too, but plug gap wouldn't have any effect on it.

As for the O2 feedback, that can be confusing. Was the engine running? If it was running, was it at idle and warmed up all the way? It's been a while since I was on a stock ECU, but IIRC, mine had a bad habit of falling out of closed loop during idle after I took the cat out. I think because it's not a heated O2 sensor, it would cool off too much and stop working.

[cbh148]

Yes, the engine was running. I sat there and stared at the LED's and watched the engine cross over from open-loop to closed-loop. Then I took it on a drive and observed that, even at constant speed or accelerating, the signal was the same most all of the time. And I'm guessing that that DOES mean it's lean??? Still not crystal clear on that, and it's strange how the FSM wasn't explicit about it, but process of elimination leads me to believe that that's the signal for a lean condition.

I'm surprised it's saying it's lean. Just the other day, I managed to put 13.00 gallons of 93 octane in my 240. I made it up to right around 320 miles on that tank, which yields a ballpark figure of 24.5 MPG, which included just a little rain drifting, and a LOT of interstate driving (and the occasional "BOV @ the ladies on campus" lol). Does ~24.5 MPG sound lean? I genuinely don't know.

[CaDet s13]

i dont even get 200 miles on a full tank. i think somewhere around 150 but im pretty sure i know why i just havnt gotten around to taking care of it yet.

[boost_boy]

If you are not getting at least 200 miles per tank, then you do have a problem. My S13 does over 220 miles a full tank, but does run have 1000cc injectors and a bunch of other go-fast goodies. But CBH, if you are getting anything over 23MPG, you are doing something right. As for the popping noise, it could be a couple of things including the type of fuel you use, the condition of your spark plugs, dirty valves, etc. The list is long, but try one thing at a time and make sure you start with the spark plugs first.

[float_6969]

Yea, less than 200 on a tank is messed up. I get better than that and I'm on E85.

[CaDet s13]

Im assuming its that bad because of my bigger injectors and possibly a crap ecu chip. But im going to start with my fuel pump and fpr since i already have new ones just havnt had the time to put them in. I also think my tune needs to get redone but im still in the market for the essential pieces to properly do it. I would love to get my hands on some kind of standalone.

[mdb4879]

I was only getting like 10mpg in mine. But I also had a 4.47 final drive and all I did with it for the most part was let it warm up, floor it for a while, cool it off, then shut it down Occasionally I did drive it normally with a slightly heavy foot and I got like 25mpg in it. Again, though, advantages of a 2300lbs car.

[s13drifter88]

Driving interstate every day with a SR 5th gear and J30 diff (and staying out of boost) I got... ... nevermind, you guys would hate me.
#takethatprius

[mdb4879]

Idk if this is still an issue, but I just thought of it a couple days ago. First, I remember you saying you run leaded race fuel at drift events. I know you said with other guys it doesn't seem to hurt, but there was speculation that it could hurt your O2 sensor. If that's the case maybe it isn't reading right and that's why your ecu diagnostic looks weird?

Also, just to rule out a lean condition, couldn't you crank up your fuel pressure a bit and seeing if the problem disappears? I'm not much of one to try to fix problems like that, but it wouldn't hurt to try just to troubleshoot.

[float_6969]

You never mentioned leaded fuels. It doesn't take long to damage an O2 sensor on leaded.

[boost_boy]

Leaded fuel? Why? You're not running enough of anything that would require the use of leaded fuel. The only thing that is going to happen is your oxygen getting whacked and you r pocket getting emptier. It is totally unnecessary to run leaded fuels unless your car is tuned so extreme, that it warrants it to buffer detonation. I hope this not true

[cbh148]

say what you want, but everyone around here with long lasting drift engines runs leaded race gas during events. never had an o2 sensor go bad after years of doing this. not a single one. and it's safer for more boost.

your arguments might hold some value if everyone's engines s*** out on them, but that couldn't be further from the truth. at least 5 people running 16 lbs on stock SR's with t25/28's, all using leaded race gas for events, and no problemos mi amigos.

[boost_boy]

What's good for the goose is not always good for the gander, but it's all good man. I mean, it's your engine and you have every right to do with it whatever you darn well please. Boost away mi amigo

[mdb4879]

Sorry if I threw you under the bus there Casey.

I don't think they're saying it will hurt the motor. As a matter of fact just the opposite. As was said, it helps to buffer detonation. Only the sensor is harmed, which I don't think is entirely critical to our motors' operation. They mostly run off a base map, the TPS, and the MAF. Idk what all the O2 sensor would do as far as running the motor except maybe trim fuel by a hair, more particularly on first startup after an ECU reset. It is a narrow band, so I doubt it does much since mostly it just sees "lean" and "rich" relative to stoich. I don't think it knows how rich you are in boost (which should be very).

What I think may happen is the O2 sensor could be damaged and it's reading rich and telling the ecu to trim back some fuel to compensate (if the O2 sensor even makes that much of a difference, as I said before). But since it isn't actually rich it's causing a lean condition (although I think you'd have a miss at idle before you'd notice anything in boost).

All this is really just my own speculation. I have no fact to back it up.

[float_6969]

He just nailed it. This is what I was trying to say. I don't remember the specifics of the CA ECU well enough to know if it has short term and long term fuel trims. If it has long term fuel trims, this WILL effect your AFR's EVERYWHERE the engine runs, as it's a percentage change that is applied (either positive or negative) to the final injector pulse-width.

[cbh148]

I never interpreted what they were saying as meaning that the engines would surely be hurt by running race gas, because like I said, that couldn't be farther from the truth since the high-octane fuel is, by nature, more resistant to pre-det.

It's just that the facts still stand; everyone here runs leaded race gas for these drift event, and no issues at all. The o2 sensor still cycles X amount of times during Y amount of time, like how the FSM reads that it should.