2015 Corvette stops accelerating - vid inside

[BuggyMasters]

I originally thought I was having a tranny up shift problem but now I think it?s actually an upper RPM problem that just so happens to be right about the time it should be shifting. Ive only had the car for a month. 2015 Stingray. A&A supercharger, cammed, intake headers, high flow cats etc. up until yesterday the most Ive got on it was a quick stab on the throttle let it hit a shift, then typically right when its about to shift again I will back off. Car is fast and strong. All work was done before I bought it by reputable shop in NC. In fact they just tuned it again a month before I bought it.

Yesterday I decided to put it through its paces from a roll. Downshifted to 2nd hit the 2-3 then at the 3-4 it just kinda stopped accelerating. Acted like it was on a two-step or something and never made the shift. Tried it a few more times and learned that if I paddled it to force the next gear that seemed to work. Its because of this I thought it had a trans issue. Today I did a trans quick relearn and went out to test it and it seems the fact that it will hit the first shift and peters out on the 2nd shift (doesnt matter where the shift starts?the first up shift is good and 2nd peters out) isnt really a trans problem. It acts like it just so happens to have enough fuel to get it through the 1st but by the time it gets to the 2nd it doesnt have it in it. Then I decided to try a 60-130 run and Id just paddle it. Wrong. The car got to about 120 and just wouldn?t do much past that. Like sat near 120 for a few seconds before I backed off.

I did a bunch of logging but aside from the default PIDs most were trans PIDs because up until that run I thought it was a tranny problem. Fuel pressure itself looks as good on the petered out spots as it does on the good spots.

I will have a wideband on it tomorrow. I suspect it?s going to show running rich due to unburned fuel.

Where do I start beyond the wideband? Any particular PIDs I should be looking at? I almost suspect a clogged converter too. I?ll put a scope in it tomorrow and look at that as well.

In this vid, note that once you see it downshift I got it to the floor. If you have good speakers you can hear it acting like a two-step. Ignore the traction control. Does the same thing whether TC on or off.

[GHuggins]

Just from the vid looks like it's running out of fuel or something else going on load related - does lower gear fine then hits a higher gear and starts sputtering. Also - have you checked the plugs - if it was back at the shop for more tuning, something probably wasn't right.

[BuggyMasters]

The heavier the load the more likely a problem as I found out trying to do the 60-130 pull. In lower speed situations, paddling it to force the shift would bring it back to power. But on that 60-130 run I paddled it and it continued to act up. In that vid there if I would have paddled the shift it would have took off as soon as it caught the next gear. It was taken to a different shop than the guys that did the original setup on it. The cam and supercharger etc were done at Mayhem Motorsports a year and a half before the last tune done back in this past October at RPM Motorsports. Both places had it at 700rwhp. I’m not sure if the guy who owned it before me took it there or if the dealership who I bought it from took it there.

[32vape]

Sounds like it's out of fuel. What's the full setup? You'll have to post a log so we can see what's actually going on.

[BuggyMasters]

I did a bunch of logging but not sure if it will have the PIDs that will help as I thought this was a trans problem. In the attached look to the last two sections where I went WOT. You?ll see a several second WOT area where the mph is barely moving around 120 mph. If you guys can tell me which PIDs are appropriate I can add them. I?m getting ready to put the wideband on however we have wet weather right now. Not sure when I can get another pull in.

[BuggyMasters]

As far as the setup it’s got one of the Mayhem cam packages - an MSD Intake - Nick Williams 103 - A&A supercharger on 4in pulley. Runs about 7-ish lbs of boost wide open. Kooks headers and high flow cats stock NPP exhaust. Dual nozzle alky control. ZL1 map sensor. They have a barometer breakout on it as well. But also it falls off boost at the shift and likely why it’s rich. Not sure what’s supposed to happen.

[BuggyMasters]

I got some good logging today with the wideband. When you hear it going flat, it’s actually running very rich. I’m thinking the meth is turned up too much. Still studying the logs. Any PIDs to check for a misfire caused by bad plugs or something? Either the richness is causing it to Peter out or there’s a misfire thing going on causing unburned fuel to show fat on the AFR. The meth is sitting at setting 5 right now. I noticed in part throttle operation right when the 1st stage of meth kicks in it will AFR about 10.1 or so.

Any thoughts?

[BuggyMasters]

Here?s the log. About 16:15:39 you can see a good example of what it?s doing. I got one good run in towards the end but there was no shift in between. Pulled hard up to about 136-ish and I let out.

[GHuggins]

AFR's read oxygen, not fuel - will show lean if misfiring. Don't see a wideband in the log, but from what you're describing it's WAY too rich. You're looking for something around a 12afr to no more than 11...

You need to log wideband, torque pids, trims, injector pulsewidths and so on to what your already logging.

[BuggyMasters]

Wideband is in there it’s just on left side serial AFR. Not in bar graph. It gets down in high single digits when the problem is there but since the boost is falling off I’m sure too much fuel as in the tune expects the boost to be there. Blow off problem? I need to read up on how exactly the BOV works. I can also tell you that I watched the meth indicator and since it sees no boost, it cuts off too.

[BuggyMasters]

Seems to me if just cruising you have high manifold vacuum and that unseats the BOV and no boost gets in. When you step on the gas the vacuum drops and the spring closes off the air path and let’s the boost build. Right? So maybe slid on BOV is sticking? I mean if you had a vacuum leak in line going to BOV then it would always build boost, right? My problem seems it looses boost at the shift.

[BuggyMasters]

I think I’m going to have another look at my BOV. How in the world could this thing be spinning 5500RPM with no boost? The only way I can think of is if there was a boost leak (which I don’t think since it is fine until it shifts) or if the BOV is relieving the boost. This made me think that several weeks ago we put the spring pressure as low as it would go. Don’t remember why but this would make sense if he backing off slightly for the shift and the BOV is slightly hung without adequate spring pressure to close it off. More to follow once I have another look at it tomorrow.

[BuggyMasters]

Well I think I may have it figured out. Today I tightened up everything and went and did a few more pulls. This led to nearly being stranded on the highway as the culprit showed their face. I didn’t take a picture but when I finally got somewhere that I could get the hood up, what I saw was the intake tube completely collapsed. This led to a phone call to A&A with a picture of what the intake setup is SUPPOSED to look like and it doesn’t include a 12” silicone hose. It has maybe a 4” hose that goes into the factory air box. Short enough that it can’t collapse. So now I’m on a quest to get a reinforced 4” hose on a 45 degree that can’t collapse. The supercharger can’t boost air it doesn’t have. More to follow once I get more to post.

[TheMechanic]

BenTune just found a similar issue on TikTock. Collapsed air hoses.

[GHuggins]

Collapsed air pipes will do it. You might want to look into a filter setup too if it sucked the tube shut.

[BuggyMasters]

Confirmed the inlet silicon hose was choking it off. All good now.