I would remove the smaller cold air inlet and test. I thought you would have picked up more than .3 psi. From the two sources that port the Roush 2650. They claim the blower picks up 1.5 psi boost with the stock 87mm tb and stock 3.0 pulley. I will be able to confirm in the next 2-3 weeks. Max boost Roush 2650 stock sized balancer, 4.5 inch cold air 103mm TB ported, 2.5 pulley Roush 2650.Not sure how many of you were on the edges of your seats waiting for this, but here it is.
The Roush system adds a pressure sensor after the throttle body but before the SC rotors. At WOT, this pressure should be very close to atmospheric and the mass flow into the rotors is directly proportional to this absolute pressure. I'm able to log this pressure, also known as SIP or Supercharger Inlet Pressure. Atmospheric pressure minus SIP represents the total loss in pressure through the airbox, air filter, inlet tube, and throttle body.
I upgraded from the stock Edelbrock GT350/Bullitt/Mach1 87 mm throttle body to an Edelbrock 103 mm. I bored/ported the SC inlet out from the stock 90 mm to 103 mm to match the TB ID. Tuning it was somewhat of a challenge, but tuning TB curves is a bit of a specialty of mine and I got it down to a gnat's ass, but that's another topic all together.
So, it turns out that my orifice and CFD models were a bit optimistic and the gains weren't as much as I had estimated and hoped for. The SIP pressure data was a bit "noisy" so I applied exponential curve-fits to estimate the differences. It turns out that the 87 mm TB curves for 3 gears were all very close (orange and green are on top of each other), and the 103 mm curves were also very close. Unfortunately, it seems I only picked up about 0.3 psi at 7100 rpm, which equates to an increase of about 2.2% density and thus power. This might get me 15-20 hp. It probably wasn't worth the effort and expense for that meager return.
The gains are probably greater at higher [mustang] rpm levels and higher boosts as well. I still have to wonder where all the losses are coming from. With atomospheric pressure being 14.7 psia, I'm still losing 1.3 psi through the inlet tract and it's not coming from the TB. I pulled the airbox lid and it made next to no difference. That pretty much just leaves the plastic duct and the air filter. Thoughts anyone?
With your info. It seems the restrictions must be in the snout and blower case beyond the 90mm inlet. This is not what I expected.
I agree it looks wide open. CNC porting does remove a significant amount of material.The blower case is wide open after the tb bottleneck.
Just got the headers back on the car about 8,000 miles into the new (POS) engine and since I don't have an updated tune for it yet, I put the tune that was on the car back and damn, does it run like the dickens.. It's fantastically loud and I missed that.
I'm just referring to the stock AFR gauge in the dash cluster. It tracks with learned stoichiometry, so around 14/1 on gasoline and 10/1 on E85.
I only watch the gauge when switching fuels or after a KAM reset. Once I got comfortable that it was working at intended, I don't bother checking when filling up on the same fuel even though it does re-start ethanol learning.
I don't. My research seems to indicate anything over about 50% is really diminishing returns as far as knock suppression goes, especially if you're running as much GDI blend as possible.
So far my experience on a couple of Mustangs has been that a DW400 on a BAP would support 15 psi boost on E85. On my Roush truck, I've only run the stock pulley/12 psi and the stock F150 pump (probably same as mustang) on a BAP actually keeps up very well, to my surprise. The Mustangs are using 55 lb injectors and the truck is using the Roush supplied 47's, but I've put some effort into maximizing GDI blend in all of them so that takes some load off the port injectors.
