Procharger D1 HO Kit Dyno Chart 4.1 Pulley - Flat power after 6400 RPM

Car is a 2016 GT Auto w/ 3.15 gear.

Mods
Procharger HO Kit with D1SC
Stage 1 intercooler
Standard Proflow Bypass Valve
52# FRPP injectors
JMS BAP (18v)
MBRP 3" street catback

Procharger came with a 4.38" pulley from the beginning (9 psi pulley)
Made 565 whp (if you take off the spike at the end of the curve)

I just added the BAP and the 4.10" Pulley, and verified tune with Lund and took it to the dyno. See chart attached.

The car with the 4.38" Pulley had a max MAF flow of 71 lb/min at 7400 RPM. On the datalogs on the 4.10" it was hitting 84 lb/min of air flow at 7400 rpm. The 4.10" pulley was supposed to max out at 11.8 psi (theory). This all made sense.

When on the dyno, all the pulls had the same air flow as the road datalogs, timing looked good, air fuel looked good, but the power flattens out and drops slightly even about 6400 RPM (138 mph) on the graph. The 160 mph on the graph is 7500 RPM.

So the power peaks at 138 mph (6400 RPM). MAF is 71 lb/min.

MAF readings keep climbing from 138 mph (6400 RPM to reach a MAX MAF of 84 lbs/min at 7500 RPM (160 mph), but the power is the same. So the car is ingesting more air, and more fuel, but the car makes NO more power. I don't understand. The datalog looks perfect in every value.

I haven't seen any power curves like this with a Centrifugal blower. The boost starts at 4 psi and ramps up to right about 12 psi (when I let off the gas).

Anybody seen this before.

Brian

I

Check your plug gaps, looks like spark blowout to me. it also could be knock, but i'd re gap the plugs honestly.

Most of the time, wherever people say to gap your plugs at, dont listen and go tighter. most dont have a clue about metallurgy and just go off of what everyone says on a forum. heating and cooling causes expansion and contraction, whatever you gaped your plugs at 1000 miles ago will open up significantly.

Knock is perfect. Still 2 to 3 negative knock retard everywhere and good timing. Air fuel is the same as well. So no signs of spark blowout.

Toothless said:

Knock is perfect. Still 2 to 3 negative knock retard everywhere and good timing. Air fuel is the same as well. So no signs of spark blowout.

Click to expand...

If it was on a sniffer, it would be hard to see the a/f move from blowout, you'd need a wide band in each bank to see it good honestly. I'd still check the plugs, it could also be belt slip but if your maf frequency is still climbing its making more boost.

It could be just one cyl having blowout and it will do that.

I had that problem also. Switched out the stock intake manifold for a boss intake manifold and it climbs all the way up to 8k now.

I was Datalogging the run with the nGauge using the stock wide band sensors. One on each bank. The scan rate is very fast. We didn't even have the sniffer hooked up. It won't hurt to check. But what I don't get is the 18% increase in MAF flow from 6400 to 7500 rpm and the same power. Spark issues should show up in reduced MAF signal I would think.

arieso94z28 said:

I had that problem also. Switched out the stock intake manifold for a boss intake manifold and it climbs all the way up to 8k now.

Click to expand...

Do you have any graphs before the manifold swap. I was wanting to try the gt350 manifold but everyone said with boost you don't need it.

arieso94z28 said:

I had that problem also. Switched out the stock intake manifold for a boss intake manifold and it climbs all the way up to 8k now.

Click to expand...

Its possible it could be the IMRC, which was most likely your problem. But if you look at the two dips that are quite common of these cars with the IMRC still on lower in his graph they are working properly.

It seems you still have cats in your exhaust system. If so, I'm guessing that backpressure may simply be reaching levels that don't allow more power to be made. The blower can be cramming more air into the motor, but if backpressure rises in response to that enough, the increased pumping losses could be offsetting the extra power made.

v8440 said:

It seems you still have cats in your exhaust system. If so, I'm guessing that backpressure may simply be reaching levels that don't allow more power to be made. The blower can be cramming more air into the motor, but if backpressure rises in response to that enough, the increased pumping losses could be offsetting the extra power made.

Click to expand...

I do. That's a pretty good hypothesis. However I think many others are running stock exhaust manifolds and cats and haven't had these issues at this low of a power. I think that Process made 900 whp on D1 and E85 through stock cats. He had other supporting Mods, but stock cats.

I see your point. I dunno, then. If nobody figures it out very soon, it might be worth running a snake camera down a header to make sure your cats aren't partially melted. That will clog things up in a hurry.

I think it's your cats also, same thing happened on my ls3 with 2.3 TVS. Pulley down made great power down low & mid rang but it was like it hit a wall after 5400 rpms. Checked the cats right bank collapsed & mushroomed causing back pressure. Deleted the cats & picked up around 25 rwhp/tq down low & 50 up top while losing 2lbs of boost.

I didn't read everything but could it be belt slip?

No boost goes up with rpm. I have a great up close video of the boost gauge, but it's 8 MB and I don't know how to post it.

Toothless said:

No boost goes up with rpm. I have a great up close video of the boost gauge, but it's 8 MB and I don't know how to post it.

Click to expand...

Got it, bump