Rebuilding LQ1 for Dummies: Intake/Emmissions!

[Mach10]

And so-on....


1) Has anyone split a 91-93 intake in half to port and polish the runners (and have it TIG'd back together afterwards)? I can do lower intake on my own (but it's pretty close to where it needs to be)... I've never seen the inside of that upper... Does anyone have a cross-section handy? If it's never been done, I'd be willing to buy a junkie and chop it open myself to have a look... But if someone has pics, I can have some edumacated guesses made. If anyone has the intake just lying around and wants to sell it CHEAP for the greater good of our hobby... Shoot me a PM. I would be more than happy to explore this option (with flow-bench data) complete with pics and instructions. I'd also very seriously looking into tossing a larger throttle plate in if I'm already going this far. Actually, it'd be cool if I could figure out a way to turn this thing into a 2-peice intake by making a gasket for it, and dropping some long bolts through it to keep it together.... Maybe welding on a few bossess... Gee-willikers, batman! That would make it easy to test-and-tune... I'd have to get both surfaces planed level, though... But still... Worth thinking about, no?

The only disadvantage I can see is that there will be a welding seam running over the top of the intake that would have to get cleaned up, or else the imposition of some new bolts that would look a little out of place... And then there'd be that vertical slash near the throat of the throttle-body... I'm sure I can get it to seal, it just won't be as purty.

2) In terms of driveability, since this is no longer destined to be a daily-driven car, (and doesn't have to pass emmissions) what advantages would I have from removing the EGR on this motor? Besides the simplification of the EFI path (which is more or less enough as it is), do I have to worry about excessive combustion temperatures at cruise? I don't expect a horsepower gain at all... Ah hell, lemme rephrase: I'm not looking for a driveability GAIN... What I want to know is that do I lose any driveability by removing and sealing up the EGR setup.

[donk_316]

Rearding your EGR. If your chip is burnt to disable the EGR then no bad effects will be had from ripping it out.

[Mach10]

That sounds like a license to rape my environment just a bit more

[SappySE107]

I used to have pictures somewhere of the manifold cut long ways, and the plenum area cut off. Gotta find them. Michael from FFP cut his plenum and ported it, shortened the runners, and welded it back together. I believe some low end was lost but thats about all I remember on it now. The runners start off larger inside the plenum, like a tunnel ram setup. However, the transition from plenum to runner sucks. 96 manifolds are better in this respect.

I still want to make a custom plenum but i have no money to be doing new projects right now. Flowbench isn't setup for DOHC heads yet either so that will be first before doing any testing with the intake manifolds.

I have had my EGR off for years. No problems at all. The combustion temps will be hotter at cruise but I couldn't tell you a difference driving it or watching the computer do its thing. Im not a fan of the EGR.

[SappySE107]

http://60degreev6.com/filestore/Sappy/plenumcut.jpg

http://60degreev6.com/filestore/Sappy/plenumcut2.jpg

http://60degreev6.com/filestore/Sappy/plenum/dohcrunnercut.jpg

http://60degreev6.com/filestore/Sappy/plenum/

Aren't you in luck, i found them:P I still have the runner one but rebelgt has the other one so I can't measure anything on it for you. Hopefully this will help you decide what to do.

[Mach10]

Well... From the side-crosssection it looks like the only real big restriction in this intake is that transition from the plenum to the runner. The problem as I see is is that I made some assumptions about the internal construction. I don't weld all that well, so ideally I'd want as few cuts as possible.

In terms of clearance, I don't think there's a lot of room to bowl out that transition in the middle.

I have a few questions that the pictures don't really answer:
1) Is the plenum a single continuous plane under the runners? If not, how is the space divided?
2) does the width of the runners stay pretty static until widening to meet the lower intake?
3) What does the transition from the throttle bore to the plenum look like (just describe it )


A concern I have is that the pinch-point there looks as though it might be accellerating the air-charge towards the runner. I say this because although it's short, it is VERY wide (across the whole width of the intake). In short, the problem that pops up during head porting: Air velocity vs. resistance vs. flow capacity. Just because something flows 1200CFM doesn't mean that the cylinders will be able to pull that much. I know the whole point of a long runner is to jack up the air velocity so that when the piston is slowing down on it's intake stroke, the moving air still piles into the cylinder out of sheer momentum.

From what I'm seeing, it looks like there may not in fact be a whole lot TO be done on that intake, short of running a flap-wheel (I have a flex extension for a dremel that will go most of the way into it) and smoothing out the sides slightly. With your permission, I'll forward these images to my hotrodder...