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Nother question about the stock V8 Magnum intake #2419493
12/16/17 03:43 PM
12/16/17 03:43 PM
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I remember years ago seeing articles about mods to make on them, wacking off some of the runner under the belly pan i believe was one. What would that mod do for HP and/or TQ. Can anyone share their personal efforts and results. Also if you can share a link that would guide me to some published data on mods to this manifold I would love to see it. Thank.
Ken

Re: Nother question about the stock V8 Magnum intake [Re: StrokerPost] #2419540
12/16/17 05:57 PM
12/16/17 05:57 PM
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Lopping off runner length translates pretty directly into a increase in HP and decrease in TQ on these things.

Another thing that was common was to box off some of the plenum area to increase throttle response but I never thought throttle response was lacking on a properly running magnum. It will not give more TQ even though it will feel like it did. It can reduce HP as the throttle body shifts more towards flowing in pulses instead of having that nice big plenum to buffer the pulses and allow the TB to flow steadily.

I think you would be far better served trying to deal with the heat being transfered to the air. Even when its 20* below zero by the time the air is going through the port it is easily over 100* and on hot days it gets a lot closer to the coolant temp. I would love to try ceramic coating the plate and manifold. Also removing the entire factory thermostat, threading some pipe fittings in to the manifold flange and running a remote mounted thermostat, there is a ton of heat conducted to the intake air through that hot coolant running just on the opposite side of the plenum. Also tons of hot oil splashing off the cam and lifters is splattering all over the steel pan on the bottom exasperating the issue from that side also.

I have personally seen just a little benifit in IAT from removing all the webbing in the AC/ALT bracket as well as spacing a second steel pan about 1/2 inch lower than the factory one useing some of the valve cover bolts with the extra stud sticking up.

The only way the eddy air gap is even remotley close in TQ is because it solves some of the heat soak issues not because of superior flow.


I am not causing global warming, I am just trying to hold off a impending Ice Age!



Re: Nother question about the stock V8 Magnum intake [Re: StrokerPost] #2419574
12/16/17 07:22 PM
12/16/17 07:22 PM
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If you measure along the centerline of the curving runner there is about 15.5 inches in the manifold and another 2.5 in the port for a total of 18 inches.

This total length resonates around 3800 rpm.

If you take into account the tapering area of the ports this gives maximum “inertia filling” also around 3800 rpm.

Chrysler engineers did their homework
putting both VE improving effects
at about the same 3800 rpm,
and this is right for a
5.2L V8 engine
....about midway between peak torque and peak horsepower
in the 1992 original 5.2/318 Magnum.

Of course it is not ideal for a 360 or 408,
Just as the combustion chamber is a little small too,
and the “bandaid” dished piston crown is slightly less efficient than the 5.2 flat top.

Re: Nother question about the stock V8 Magnum intake [Re: StrokerPost] #2419586
12/16/17 08:00 PM
12/16/17 08:00 PM
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I think a 360 with a flat top would be perfect for the chamber size if not for NOX concerns.


I am not causing global warming, I am just trying to hold off a impending Ice Age!



Re: Nother question about the stock V8 Magnum intake [Re: StrokerPost] #2419768
12/17/17 11:17 AM
12/17/17 11:17 AM
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Would it be throwing good money after bad
to retrofit a Magnum 5.9 V8
with flat top pistons set at very tight quench clearance
and eight Holley brand 30 lb/hr fourteen hole fuel injectors
then begin running it on
100% E85
and gradually custom mix fuel blends of
E70, E50, E40, etc
To find out what AKI octane rating
the worst cylinder pings at?

Re: Nother question about the stock V8 Magnum intake [Re: 360view] #2420175
12/18/17 02:08 AM
12/18/17 02:08 AM
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Nother curiousity, in these 2 photos you see the earlier intakes, pre 98 I believe, and 98 and up. The early ones had the tall divider, the later ones had no divider. Does anyone know what was behind the first version and then why it was changed?

20171217_215009-594x432.pngScreenshot_20171217-214653-1165x753.jpg
Re: Nother question about the stock V8 Magnum intake [Re: StrokerPost] #2420227
12/18/17 09:08 AM
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You are getting into “nerdy tech territory”.

A possible simple answer:

The 1992-1995 model years did not have as efficient 3 way catalytic converters, and had to rely on EGR above 60% load to keep NOx pollution low enough to pass the drive cycle test. To get all 8 cylinders a mostly equal share of the EGR it required two EGR outlet nozzles below the two throttle bores, and a deep center divider. When better performing 3 way catalytic converters became available in 1996 EGR was done away with. Old manifolds in stock, and old casting molds used until late in 1997. 1998 saw revised manifolds that did not have the complicated to cast EGR passages.

A more complicated answer:

Chrysler engineers long ago kinda pioneered the idea that long runner intake manifolds used “3rd reflextion pulses” to improve typical driving rpm range torque, although this technique slightly reduces high rpm peak horsepower. The Magnum V8 manifold extends the runners out to 18 inches with only gentle curves, but had to have a center divider to block some cylinders sonic pulses from interfering with neighboring cylinders at lower rpms. Also a “huge” plenum volume is used surrounding the runner inlets to strengthen some pulses and dampen others. A bad side effect of a huge plenum is that throttle responsiveness slows.

Re: Nother question about the stock V8 Magnum intake [Re: StrokerPost] #2420521
12/18/17 07:02 PM
12/18/17 07:02 PM
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I put a 5.9 in my jeep and I can't stand that intake. The plenum plate deal sucks, it looks stupid, seems like it takes up a bunch of room. Maybe it's all in my head. I think I'd be more into the magnum swaps if you could still buy the efi m1, or something like it to get rid of the keg and plenum plate.

Re: Nother question about the stock V8 Magnum intake [Re: JAMESDART] #2420742
12/19/17 01:14 AM
12/19/17 01:14 AM
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Originally Posted By JAMESDART
I put a 5.9 in my jeep and I can't stand that intake. The plenum plate deal sucks, it looks stupid, seems like it takes up a bunch of room. Maybe it's all in my head. I think I'd be more into the magnum swaps if you could still buy the efi m1, or something like it to get rid of the keg and plenum plate.

This might be the intake for you then, especially if you've made other mods to your engine.

Screenshot_20171218-211109.png






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