VG30E Intake almost ready to Howl!
11-30-2008, 09:16 AM
#1
, but i think the pathfinder intake with port work would be better for the maxima vg30e. but that's just me.
11-30-2008, 10:15 AM
#3
Senior Member
Join Date: Dec 2004
Location: EU Scandinavia
Posts: 4,323
12-01-2008, 07:45 AM
#4
Had to trim the gasket after I bolted the collector to the lower manifold. Wish I could get a good picture down to the intake valve it's a perfect fit all the way thru now ...didn't get crazy with just cleaned it up and port matched!
12-29-2008, 10:21 PM
#7
So wait, did you port match your lower intake to the cylinder heads? Because if you missed that it almost makes this pointless. No sense in port matching only half the intake air path. The step between the lower intake and the cylinder head is the most important part. Nice job on the part you have shown pictures of, though!
12-29-2008, 10:45 PM
#8
Junior Member
Join Date: Oct 2002
Posts: 87
Hey, lookie what pics I pulled up from the dead!
(let's see if I can get these pics working...)
Granted, my 200k+ motor sure looks a little more "tired" than that awfully nice, clean fresh rebuild of yours.
(let's see if I can get these pics working...)
Granted, my 200k+ motor sure looks a little more "tired" than that awfully nice, clean fresh rebuild of yours.
Last edited by jakeru; 12-29-2008 at 10:50 PM.
12-31-2008, 01:47 PM
#11
Junior Member
Join Date: Oct 2002
Posts: 87
Thanks! I can't remeber if those pics were before, or after I cleaned it up a bit.
Anyway, I remember being a bit surprised that the *factory* ports didn't enlarge the downstream piece diameter after the transition more than they did. Air transitioning suddenly from a smaller diameter to a larger diameter is generally far better than having the transision be from larger diameter to smaller diameter (due to the nature of how air flows differently around the same obstructions depending on what direction it is traveling), or same diameter but where the edges don't line up (as seemed to be the case on the stock VG port match in this area.)
Usually good modern design practice I have seen on other modern auto manifold designs, is they slightly oversize the diameter of the downstream portion of the port interface to ensure there is no "overhanging lip" facing the direction looking upstream into the airflow (which is particular bad for free airflow, and is what I found on some spots of the VG intake manifold design here.)
As to why they can't make them match up perfectly, it is because there is very limited production tolerances of factory cast shapes due to the casting process, they might be able to position the "port surfaces" only to the nearest ~1mm or so. The way they could get more precision than ~1mm involves too much cost (IE: by hand with a die grinder at the factory before hand assembly, or perhaps nowadays by port shaping with an automated CNC mill rig), those techniques are far too expensive for mass-produced passenger cars (but may be found on the most exotic ones, IE: ferarris, or perhaps the higher end porsches, etc).
As to whether the port matching helped performance... I didn't gather any objective hard numbers (a la before and after dyno, etc) but I do recall thinking that subjectively (a la *butt dyno*
) that the port matching might have made the motor feel slightly more strong and "freed up" in only the higher RPMs. I'd say it is plausible that the port matching here helped increase power and torque as much as ~2-3% in the higher RPMs of the (otherwise mostly stock, except for 2.5" mandrel bent exhaust) VG motor.
Anyway, I remember being a bit surprised that the *factory* ports didn't enlarge the downstream piece diameter after the transition more than they did. Air transitioning suddenly from a smaller diameter to a larger diameter is generally far better than having the transision be from larger diameter to smaller diameter (due to the nature of how air flows differently around the same obstructions depending on what direction it is traveling), or same diameter but where the edges don't line up (as seemed to be the case on the stock VG port match in this area.)
Usually good modern design practice I have seen on other modern auto manifold designs, is they slightly oversize the diameter of the downstream portion of the port interface to ensure there is no "overhanging lip" facing the direction looking upstream into the airflow (which is particular bad for free airflow, and is what I found on some spots of the VG intake manifold design here.)
As to why they can't make them match up perfectly, it is because there is very limited production tolerances of factory cast shapes due to the casting process, they might be able to position the "port surfaces" only to the nearest ~1mm or so. The way they could get more precision than ~1mm involves too much cost (IE: by hand with a die grinder at the factory before hand assembly, or perhaps nowadays by port shaping with an automated CNC mill rig), those techniques are far too expensive for mass-produced passenger cars (but may be found on the most exotic ones, IE: ferarris, or perhaps the higher end porsches, etc).
As to whether the port matching helped performance... I didn't gather any objective hard numbers (a la before and after dyno, etc) but I do recall thinking that subjectively (a la *butt dyno*
) that the port matching might have made the motor feel slightly more strong and "freed up" in only the higher RPMs. I'd say it is plausible that the port matching here helped increase power and torque as much as ~2-3% in the higher RPMs of the (otherwise mostly stock, except for 2.5" mandrel bent exhaust) VG motor.
Last edited by jakeru; 12-31-2008 at 02:04 PM.
12-31-2008, 04:25 PM
#12
Well you can port match you plenum intake runner entrance. Place a rag or towel down in the port with a little bit of bearing grease and break out the die grinder or Dremel. Use a vacuum to suck up the big pieces and the grease with catch the smaller pieces.
As far as how the port contours from a larger area to a smaller area, That's what's called a venturi. The smooth entrance promotes smoother air flow into the port as it accelerates into the head intake port and then (slams into) the combustion chamber. Only time you want air to go from smaller to bigger is when you going supersonic and the air needs to be slowed due to prevent a compressor stall cause by the sonic shock wave. The port matching is more obvious @ lower rpm due the increase of the airflow velocity resulting in more torque. My little 326,000 mile D21 Hardbody got the works in port matching and man along with the cam and headers that 4 cylinder feels very peppy and more like a 6 cylinder. Anyhow every little bit helps and I'll make sure they perfectly matched on any engine I'm modifiying.
As far as how the port contours from a larger area to a smaller area, That's what's called a venturi. The smooth entrance promotes smoother air flow into the port as it accelerates into the head intake port and then (slams into) the combustion chamber. Only time you want air to go from smaller to bigger is when you going supersonic and the air needs to be slowed due to prevent a compressor stall cause by the sonic shock wave. The port matching is more obvious @ lower rpm due the increase of the airflow velocity resulting in more torque. My little 326,000 mile D21 Hardbody got the works in port matching and man along with the cam and headers that 4 cylinder feels very peppy and more like a 6 cylinder. Anyhow every little bit helps and I'll make sure they perfectly matched on any engine I'm modifiying.
01-02-2009, 02:11 PM
#14
Taking my Maxima to the Max!
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So, who actually has a pathfinder/Xterra intake on their VG Max and has pics to show? Does porting and port matching the VG Max intake do enough to bring it close to a Pathy intake? Reason I ask is because I have to replace my Injectors soon and want to know what I should do to maximize my airflow.
01-02-2009, 02:16 PM
#15
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Join Date: Jan 2007
Location: NJ
Posts: 475
So, who actually has a pathfinder/Xterra intake on their VG Max and has pics to show? Does porting and port matching the VG Max intake do enough to bring it close to a Pathy intake? Reason I ask is because I have to replace my Injectors soon and want to know what I should do to maximize my airflow.
01-02-2009, 02:28 PM
#16
01-02-2009, 03:16 PM
#17
Taking my Maxima to the Max!
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Join Date: Dec 2003
Location: Alachua, FL 32615
Posts: 1,096
01-02-2009, 04:36 PM
#18
http://forums.maxima.org/3rd-generat...ic-here-6.html
Scroll down a few posts on that page..
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