Improved fuel economy?

[94burbk1500]

The PO put dual exhaust on with no crossover using the factory manifolds, no cats, I realize it isn't the best configuration, but it works. I actually did a tune up on the truck 4k miles ago, all filters, plugs, wires, cap rotor, trans filter. Also replaced the fuel pump, egr, pcv, battery, radiator, thermostat, coolant hoses, all vacuum lines, new tires, and switched to full synth oil with 1 qt of lucas stabilizer.

 

[L31MaxExpress]

To be honest I never checked pressures, just IATs. That's surprising to me but I'm not necessarily doubting it. I do wonder if the average Joe would ever even notice any negative effects from that restriction, though. I also wonder how much better any of the aftermarket intakes actually are.

EDIT - Another random thought, I wonder how much of that restriction is in the filter? A dirty filter would definitely reduce flow, and there's also the matter of the K47 filter option which is slightly larger than the standard one.

I stand by my statement that the Volant is the only aftermarket intake worth anything, and even then I'd replace the oiled gauze filter with something dry like an Amsoil Ea. The filter on my K&N FIPK leeched enough oil onto my MAF to trigger a CEL in about a week, fresh out of the box.

I have a Volant that has been on both my brothers Suburban and my Tahoe. The Volant makes a noticeable difference in both the MAP and MAF readings. If you never get the truck over 3,500 rpm you would never notice a difference, IMO.

As for the K&N causing a MAF issue. I wonder if yours was over oiled. I have had K&Ns on numerous vehicles with MAF sensors and have not run into a fouling issue yet. My Express van has had a K&N since 2006 and never had an issue. I ran an Airaid MXP CAI on my 2012 Nissan Titan and in back to back testing it went 2 tenths quicker in the 1/8 mile. My Infiniti M56S uses dual filters and dual MAF sensors. A 2* timing bump and K&N filters made that car go from 378 rwhp and 390 rwtq to 390 rwhp and 410 rwtq. I have had K&Ns in that car for 50K without issue.

 

[L31MaxExpress]

The PO put dual exhaust on with no crossover using the factory manifolds, no cats, I realize it isn't the best configuration, but it works. I actually did a tune up on the truck 4k miles ago, all filters, plugs, wires, cap rotor, trans filter. Also replaced the fuel pump, egr, pcv, battery, radiator, thermostat, coolant hoses, all vacuum lines, new tires, and switched to full synth oil with 1 qt of lucas stabilizer.

Put you a nice set of shorties on it and add an exhaust crossover as close tp the engine and as far from the mufflers as possible. I prefer X-pipes but those are not always easy to package into an exhaust setup. On my M56S that came from the factory with Tri-Y shorties, I ditched the 2 rear cats, the OEM 2.5" Y-pipe, the tiny pipes going into the resonators which only had 1.5" cores, then did away with the OEM mufflers. I went from the 2.5" inlets to the factory non monitored rear cats and fabricated a 2.5" dual system with a X-pipe and Magnaflow race mufflers. While it is not ideal I had to put my X-pipe right in front of the mufflers for space reasons. Gained a very sporty tone and torque everywhere in the powerband. My highway MPG shot up 2-3 mpg at cruising speed. Up from 22-23 mpg to 24-26 mpg. The M56 is only a ~340 CID engine.

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[L31MaxExpress]

Double post

 

[df2x4]

As for the K&N causing a MAF issue. I wonder if yours was over oiled.

Possible, but if it was it came that way from the factory. I cleaned and re-oiled it very carefully after that first incident and never had the issue again, but then again I only ran it another 5k miles or so before replacing the K&N filter with a dry Amsoil Ea.

 

[Christian Steffen]

I know we're mainly talking tbi trucks here, but with the factory intake on my truck and the hd filter, I would usually see a 4-5 kpa drop from 4200 to 4800. I really didn't think that was too bad.

 

[df2x4]

I know we're mainly talking tbi trucks here, but with the factory intake on my truck and the hd filter, I would usually see a 4-5 kpa drop from 4200 to 4800. I really didn't think that was too bad.

That's a lot more like what I would have expected. Now I want to check the one on my Suburban with the K47 filter. I'm thinking that may be a big part of the discrepancy.

But yeah, sorry for the thread derail!

 

[Supercharged111]

On my 1500 I saw pressure drops more in line with what Fast posted, and the drop started at 3000 RPM. Removing the airbox lid staved the drop off until closer to 4000, and removing the filter nearly eliminated the pressure drop. I think at that point I dropped 2 or 3 kpa and that wasn't until 5000. IATs were really high though. The TBI trucks have a sort of choke tube inside the resonator but it slides right out.

 

[df2x4]

Out of curiosity which style air box are/were you guys running when you saw these readings? The Vortec trucks had two styles of box. First design and second, I believe they switched in 1997 with some overlap during that model year. Pictures of each style on the first post of this page, by @east302.

https://www.gmt400.com/threads/air-intake.40309/page-6

As far as I know it's just cosmetic differences between the two, but who knows maybe one flows better than the other. Both of my '97s have the first design.

 

[Supercharged111]

My 1500 has the later design being a 98.