Loud popping at about 4.5k rpm's

[Mustangs_Suck]

Alrighty, It's summer time now so it's hot and humid here..

When I punch it now, at about 4-4.5k rpm's the car gets EXTREMELY slower as if it's being held back by something, followed by loud popping from the exhaust.

It was on a more winter tune before, do y'all just think I'm dumping too much fuel in now that it's warmer and it's running too rich, or are there other factors that may be causing this?

It's a T25 turbo btw, so yes I know it dies out earlier on, but this seems to be extreme.

Thanks.

[Nissan_240sx]

what are your a/f ratios when your at 4 - 4.5k?

[C-Kwik]

If you haven't already, try slowly getting to those RPM's (without getting any boost). If it revs all the way to redline okay with a light load, it's likely your spark blowing out. This sounds like it could be the case as a big misfire would cause a dramatic loss of power (feels like a rev-limiter) and the popping is likely the unburnt fuel igniting when it exits the exhaust pipe. When I had my KAT andwas running a divorced wastegate set-up I had this issue and was blowing flames out of the dump-pipe.

A simple solution is to close the spark gap (more if you're already running a smaller gap). A better solution is to upgrade your ignition system to deliver a more powerful spark over the factory gap setting.

[Mustangs_Suck]

what are your a/f ratios when your at 4 - 4.5k?

It was tuned to be a steady 12.5:1 so I'm assuming in that area.

[Mustangs_Suck]

If you haven't already, try slowly getting to those RPM's (without getting any boost). If it revs all the way to redline okay with a light load, it's likely your spark blowing out. This sounds like it could be the case as a big misfire would cause a dramatic loss of power (feels like a rev-limiter) and the popping is likely the unburnt fuel igniting when it exits the exhaust pipe. When I had my KAT andwas running a divorced wastegate set-up I had this issue and was blowing flames out of the dump-pipe.

A simple solution is to close the spark gap (more if you're already running a smaller gap). A better solution is to upgrade your ignition system to deliver a more powerful spark over the factory gap setting.

That's most likely it, the plugs are about a year old or so and have been put through quite a few tuning sessions, so they are probably fouled to ****.

.032 I think is what I set them at, you're saying make that gap smaller?

[GEO]

12.5:1 AFR is alittle dangerous on a turbo car to begin with, I always tell people to run aliitle lower so the extra gas cools the chambers. Popping is usually more gas then spark, maybe your timing is messed up within that range.

[Mustangs_Suck]

12.5:1 AFR is alittle dangerous on a turbo car to begin with, I always tell people to run aliitle lower so the extra gas cools the chambers. Popping is usually more gas then spark, maybe your timing is messed up within that range.

hmm maybe another tuning session is in order, or getting my hands on a wideband and d!ck' with it myself.

When I first got the car I drove it with a 14.5:1 AFR (unbeknownst to me) for like a year. The people who tuned it said they didn't know how the hell it didn't explode so they set it down to 12.5:1 when they dyno'd it a few times.

Either way, i'll lean it out a bit and clean the plugs and see what happens.

[nissanfanatic]

Replace the sparkplugs with new ones. A year is a little long to run a single set.

[C-Kwik]

Depends on the type of plug. Platinum and iridium will last long even under fairly heavy boost.

As for gapping down the plugs more, I'd avoid overly closing the gap. You might try a good platinum or iridium plug as they have thinner center electrodes which will reduce the quenching effect and reduce the need for more spark energy or a smaller gap. Be careful not to reduce the gap on these plugs with a gapping tool as it may press the exotic metal into the tool and the button of metal may come off rendering the benefits of the plug useless.

Lastly, fouled plugs typically occur in very rich environments. If you're able to idle and drive the car regularly, chances are, the self cleaning properties that occur in combustion have kept the plugs relatively clean.