Ported Intake Manifold

[99LeCouch]

So I received a ported intake manifold today, and am expecting mixed results when it gets installed in late October. I've heard anecdotal reports from other folks who drive cars with the 3800 Series II engine in my LeSabre that they've picked up 1 mpg both city and highway from just this mod. I'll see.

In general, I heard porting things did increase power, and so increases fuel efficiency since the engine isn't working as hard to get air in. I do a lot of highway driving, and will be putting a lot of highway miles on my car later this fall. Therefore closed-throttle operation is not as important for me as highway efficiency, and my fingers are crossed this helps boost part-throttle efficiency.

[Bicycle Bob]

When there's less resistance in the manifold, you just use more at the throttle plate when cruising. This mod can only help with the throttle wide open and the injectors still on lean.

[nemesis]

You'll see more power up top 4krpm+ and less torque at the bottom 4krpm- you might lose gas mileage. I would think smaller duration cam and intake with longer runner would gain more torque bellow 3k rpm and that should net better mpg, but you never know, I am going from going fast to getting better gas mileage which is total opposite to say the least.

[99LeCouch]

We'll see. I have it, might as well install it. Worst case I take it off in a year and trade it for somebody's stock manifold.

[99LeCouch]

Originally Posted by nemesis

You'll see more power up top 4krpm+ and less torque at the bottom 4krpm- you might lose gas mileage.

Well, I finally got around to installing the ported and polished manifold. The car pulls like a motherf'er everywhere in the rev range. I'm having to learn to drive it all over again since it got very, very, very responsive to my right foot. The SG helps a lot learning to keep my foot reeeeeeaaaaalllllllly still.

I have gains everywhere in the powerband since the computer is letting the car stay in TCC lockup on hills it previously would have unlocked on. Instead of kicking up to 2000 RPM and 8 mpg (steep hill @ 30 mph) it's staying at 1100 RPM and 14 mpg for that hill. So it may well do better in the city now. I can hope...

Highway I haven't been able to tell yet since my fuel trims were reset and have not been relearned yet. It does go awfully nicely, though!

[micondie]

Your stock intake must have been very restrictive. I think this shows that different motors have different responses to mods and we should all look carefully at what the factory has given us to work with and direct our mods towards eliminating or reducing the shortcomings of our particular motors and not just do the "Mod du jour"

[jkp1187]

Originally Posted by micondie

Your stock intake must have been very restrictive. I think this shows that different motors have different responses to mods and we should all look carefully at what the factory has given us to work with and direct our mods towards eliminating or reducing the shortcomings of our particular motors and not just do the "Mod du jour"

@99LeCouch: Have you removed your factory air box and taken a look at it? If it's like the one in my 3800 Impala, it is restrictive. The intake area is small and circular, and there's a ridiculous little duct that funnels the air toward the air filter. I removed that duct and used a jigsaw to cut open a larger intake port -- like this:

2001 Impala How To

[aerohead]

I ran across an article in HOT ROD Magazine's Feb. 2008 edition entitled "THE MANIFOLD MAN."
Some intake manifolds were ported,evaluated on a Superflow Technologies Group flow bench,then installed on a 410 cubic inch Chevy small-block and run on a SuperFlow 901 dyno at Westech Performance Group.
The best results came from an Edelbrock Super Victor manifold,here's what's interesting:
Between 3,600 rpm and 4,800 rpm,the engine alternately gained or lost horsepower.
At 5,000 rpm a positive horsepower trend was finally established with a 2-HP gain.
At 6,800 rpm the engine developed its maximum 615-Bhp compared with 602-Bhp for the un-ported engine,a 2.16% power increase.
The engine was operated with an open velocity-stack on the intake and open headers( vented to outside the test cell) for the exhaust.

[99LeCouch]

jkp, yes, I've gutted the airbox on my LeSabre. That didn't make much of a difference back when I did it. It does now!

aerohead, my car has a lot more low-end grunt now. I'm using less throttle to get the car moving, and keep it moving. Also, the engine is knocking a lot less, which is letting me have access to the power it has. It was knocking before since the cylinders were getting slightly different amounts of air with the same amount of fuel for each because of the poorly-cast OEM intake manifold. Evening that out is giving me a mixture more consistent across all the cylinders. Thus, less knock.

The car is slowly learning its fuel trims after throwing a CEL for an emissions problem caused by me reversing two emissions hoses on a solenoid. Hopefully I'll have better fuel economy data to report after another few weeks.

[nemesis]

Wasn't expecting that, and thats why I am here for, I'll be waiting for more results.