FieroZ34

iTrader: (1)

First off, this is not a LS1. It's not even a V8. But it is a GM, and I've seen recently how much some of you know about the ITB setup, and would really like the input. In addition, the same theories here can be applied to the LS1, but with its aftermarket they don't really need to be. Anyways, here we go.

I've been playing with the 3.4 DOHC V6 for a while now. My newest engine will be swapped into the black car in my sig, a really nice 88GT. The engine's mods are as followed. Brand new GM crate engine, 9.25:1 compression. Fully ported, polished, and reshaped heads (~330cfm at .5 lift int, ~240cfm exh). 48g lifters, about 50% lighter than stock. Stock cams, exhaust retarded about 12*, intake advanced 4* (These will be custom tuned on the dyno). Exhaust will eventually be a custom set of equal length headers. The intake will be a set of ITBs I bought about a year ago. They have 48mm blades, and mount the injectors right after the blades.

The first problem is getting them on my engine. First, the ITBs are round, and my intake ports are square. Second, and more importantly, the port spacing on the head is wider than the bore spacing on the ITBs. Third, the intake side head surfaces are very close to each other, so I don't have much room to play with. And lastly, I can't cross them because they "overlap." Here is a pic from the engine that is currently in my other Fiero:



So here is the plan. I think about this everyday, and despite putting my engineering type mind at it 24/7, I cannot get a good solution. The angle spread from one head's intake surface to the other's is 90*, so that makes thing's a bit easier. My plan so far is to run a 90* bend from each port, so that the ITBs would sit theoretically almost level with the valve cover angle. So not straight up, but tilted to the approximate spread angle of the cylinders (A 60* V6, but these would be 90* with respect to each other because of the intake angle). Then I could turn each of the outer ports runner in, which will make it so that they match the closer bore spacing of the ITBs. The problem here is that the middle cylinder on each bank will have a slightly shorter runner than the 4 outer slugs. Furthermore, I'm not sure how the additional turning of the intake runner will affect tuning/power differences (These runners will be wet as fuel is injected in the ITB, above these). If anyone can think of anything else, I'm ALL EARS. I thought about crossing them, but that will be a lot of fabrication because they not only would hit each other as it is, but I'd still have to tweak the outer runners in.

Here are the ITBs. Notice the flanges on the left, you can see the spacing/shape issues there.


Standing them vertically is also an option, but quite simply, I don't even know how I'd get the runners to match the spacing, and change shape in so little space. Plus, they'd be really cramped here.



As far as the actual tuning goes, a stock GM EFI is pretty much out of the equation. I havn't really thought about this yet, as there are a lot of solutions, though I have worked with MegaSquirts before and I like them, plus they'd do everything I need them to. I need a plugin/referenced wideband O2, MAP-based speed density, the ability to control GM DIS, and real-time tuning. The MS2 does all of this, and can replace my factory ECU (I want it to do this). Again, if there are any other ideas, I'm all ears. I'm throwing this out to try and get more ideas of how I could make this a reality. So please look beyond the fact that it isn't an LS1, and throw some ideas out!

Adrenaline_Z

My god, are you ever in for a task!

I think one item that you'll need is some sort of valley pan to cover the
lifter area. That's the easy part. Make a template and cut a piece of aluminum to size with some RTV gasketing.

What does the stock intake manifold look like? Can you hack away at the
mating end to match the head ports and then make a smooth transition to
the ITB's? Of course I don't mean using a common plenum, I mean the mating
flange of the intake.

Cross section and length is going to be critical to ensure equal charge to
each cylinder. Post up a pic of the intake and that might spark some ideas.

FieroZ34

iTrader: (1)

Thanks for the reply, and yes, I most certainly am!

What was the lifter galley is already covered stock, you can see that piece in the pic above (Woot for DOHC engines!)

Below is the stock lower intake. I could chop off the runners and such, but then I have essentially just flanges. And I already have some laser cut flanges, so that doesn't do me too much good. I thought about finding a way to adapt the ITBs to the top of the LIM, like the stock upper intake does, but there are a few problems. First, the ports are REALLY close together, like 1/8". Second, they're still square. And third, my ITBs are set up in two sets of 3 bores. Lastly, if I did get it to work, I'd be collecting a lot of runner length and adding to the height of the intake. The offset of the runners below isn't a problem, on the 96 intakes, they are all in a row, not offset to each other, so I coudl swap to the 96 intakes if need be.