Something odd happened on the way home

I was cruising on the highway doing 55 when I came up to someone going way below the speed limit. I was feeling good and decided to push the car some and downshifted to 3rd to get ready to pass. Now my clutch is on the edge of slipping, so I always make sure it's fully engaged before giving throttle. I rev matched to get me into gear ~3500 or so, make sure my foot is off the clutch, and floor it only to find the power cut and a HUGE and I mean HUGE cloud of black smoke poured out the back. I let off the throttle and upshifted back into 5th and the car acted like nothing happened. Power is back, clear road behind me, no weird noises. Later down the road I try to recreate the event doing exactly what I did before, 3rd, 3500, full clutch, full gas, and the power was there like it normally is. I'm thinking it was either my wastegate sticking or the n75 valve leaking by. Anyone have any other ideas?

Sent from my SM-G950U using Tapatalk

probably sticky wastegate.
any mods? even a stock or firaly stock AHU/ ALH wont smoke very much at all when a boot pipe comes apart.
a HUGE and i mean HUGE cloud of black smoke means you some how lost boost and overfueled at the same time. Do you have VCDS? i would just check the health of your injection and what the QA is set at. i would also start making logs and try and do this again. might be a fueling issue or leaking nozzle. I have a similar issue but it is about 1,000 x worse than yours and i can do it every time. down shift and hit it after a briefe high down rev and i can shoot flames and sparks of soot out my pipe! its called too much fuel lol.
Your not too far from me. if you don't have VCDS i could help you out!

+1 Black smoke usually is from too much fuel or not enough air, which could happen if the turbo wasn't dumping enough air into the system, which could happen if your waste gate wasn't closing....
Have you inspected those vacuum hoses recently? mine were pretty ugly before I replaced them a few months back.

Does your car have a tune or upgraded nozzles?

Car is tuned. Malone stage 2 with Bosio 1016 nozzles with about 5k miles on them. QA set at 4.2 and timing is dead center. I replaced all the vacuum lines including the one in the ECU about 10k miles ago. Exhaust is new with a catless downpipe. I replaced the injection pump after I had the problem with high injector deviation, and it's been perfect since.

I'm thinking since I couldn't get it to do it again that my wastegate is on its way out

Sent from my SM-G950U using Tapatalk

My guess: matting the pedal under those conditions gave you compressor stall: more heat (energy) flooded the turbo than the turbo could turn into kinetic energy at the speed it was rotating at and the blades stalled... resulting in too much fuel to air and a ton of black smoke. It cleared itself eventually, the turbo started to spin, and off you went.

Compressor stall is not unheard of with extra fueling and big nozzles and it tends to happen when one stamps on it aggressively with the turbo at fairly low speeds. I had an ALH once that was in the same boat... when I floored it to pass someone going really slow in front of me. Very low power, big cloud of black smoke, engine cough cough cough. 15 seconds later excessive fueling resolved, turbo spun up, and normal function returned.

I agree. Too much fuel and not enough time for the turbo to catch up. I’ve had this happen as well.

This happened a few times to me, but only when the car was cold. I also lost power, until the extra fuel cleared itself out. Bigger nozzles and tune... I think this used to be referred to as “warp field collapse”?

Now, I just avoid getting on it, until it’s warmed up a bit. Issue solved.

-Todd
__________________

ToddA1 said:

This happened a few times to me, but only when the car was cold. I also lost power, until the extra fuel cleared itself out. Bigger nozzles and tune... I think this used to be referred to as “warp field collapse”?

Now, I just avoid getting on it, until it’s warmed up a bit. Issue solved.

-Todd
__________________

Click to expand...

Oh that's what warp field collapse refers to? I thought it was another term for limp mode.

Thanks for the insight everyone. It hasn't happened since. The car was only running for about 5 minutes or so. That very well could've been why.

Sent from my SM-G950U using Tapatalk

ToddA1 said:

“warp field collapse”

Click to expand...

10/10
i remember those days and those threads.
in a nutshell, your building up fuel and when it goes bang it essentially forces the turbo to spool up but then it reverses and basically causes the turbo to spin backwards or "surge" this causes issues and basically bad things over time.
its more complicated than this but eh, good enough for a quick post.


just fix your clutch. SBC stage 2 endurance is probably one of the best daily driver clutches you can get for the price.