3500 plenum and wet nitrous

[3400-95-Modified]

Bottom line is best bet with EITHER of the two intakes 3400 or 3500, the best route to take is DPI. the 3400 plenum is no better, its gonna short change cylinders 1 and 2, of fuel and nitrous, and over power 5 and 6, which is the big flaw of that intake to begin with. Unfortunately with these motors thats the natural issue with them since the air is fed from one side of the motor rather than the top like a carb intake. I will be using my 3100 large port again, but If I feel that its not running the way I like I will be upgrading to a 3500 upper and plenum spacers and then doing DPI to make sure its all even. Thats the only way to make the most power with a nitrous system and be consistent.

yeah I'll have to buy 6 nozzles and bend some lines and all that jazz. You still only need two solenoids for fuel and nitrous, but it would look UBER hot when done.

[IsaacHayes]

The equinox plenum looks like the 3500 one, but has the TB neck attach from the top center of the plenum. So it does the same thing, only better with it opening from the top of the plenum in the center. That would be fun to run if it would clear our hoods. And great for nitrous.

[ForcedFirebird]

But I dont understand how it would flow better to all the ports if air has to back-track and fight again incoming air to get to the 5 & 6 ports?!?!

The air is more evenly distributed. If there was no "tube" in there, the first two ports would have more access to air than the furthest cylinders. Makeing the air have to "back track" to the fron two ports makes the distance to travel more similar. Much like when you look at a set of equal length headers. The primary with the shortest distance to go to the collector has extra bends in it.

[IsaacHayes]

Yeah it's hard to picture. But I'm sure they made it that way for a reason....

[G-U-NOT]

But I dont understand how it would flow better to all the ports if air has to back-track and fight again incoming air to get to the 5 & 6 ports?!?!

[Superdave]

Just use a small cutoff wheel on a die grinder and cut out that piece.. shouldn't be too hard... or inject the nitrous from the brake booster port or something.. lol

[IsaacHayes]

No that is the first plenum he had on the motor when he got it that was busted up, so he chopped it up more.

The extended neck is part of what makes the 3500 plenum good. The 3400/3100 style didn't open up in the center. The idea is it gives better flow to all ports, instead of just the ones right at the start.

[G-U-NOT]

Did you cut that plenum in half???
Thats not the 1 you're sending to me is it? LOL
I noticed that the neck goes about 1/2 way back and passing the first 2 ports...
would it be possible to cut that half circle off to open up the neck as soon as it enters the larger area so that the incoming air doesnt have to back-track in order to get into those first 2 ports?!?!?!

[merlot566jka]

look

I don't recall what the inside of the 3500 plenum looks like. Since there is no hole at the opposite end of the plenum from the throttle body, the nitrous flow would primarily be propelled by the force it was injected with toward the cylinders farthest from it, since there will be no air rushing in behind or with it when it's injected from the closed end of the intake, the air rushing in through the throttle body will reduce its effectiveness at covering the distance. If it can be done centrally that would probably work a lot better.

I doubt there would be much of a problem at the TB end because air will always be rushing in at that point to reduce any potential for it to puddle. I believe the real problem is just trying to flow the mix upstream against the momentum of the airflow inward. I was thinking about looking into small enough nozzles to place one on each runner of the lower intake plenum for my water injection, distribution doesn't get any better than that unless it flows in with the fuel through the injector.

I'm scared of nitrous, it's worse than starter fluid and it doesn't give you any power. It will blow you a new "one" if you mess up using it though.

[ForcedFirebird]

I wouldn't chance it. I was turbocharging back before it was as popular as it is now and before tuning stock ECMs was as popular and practical as it is now back in 94. One way I dealt with the challenges was to add an extra injector at the back of the intake instead of at the throttle body end and I noticed it didn't seem to help the fueling problem according to the feel of acceleration until it was moved to the entrance end of the intake and I suspected it was pooling at the end of the manifold as a result of the air rushing in and preventing the injected fuel from sufficiently reaching the forward ports .

Although he's not boosted, the flow dynamics in some ways are the same, nitrous distribution under load will have to travel upstream against incoming airflow and intake scavenging. I feel very strongly about the unlikelyhood that even without having to face a 90 degree turn it will provide better flow into the 5&6 port since air going to all pistons must pass cylinders 5&6 before they reach any others and not visa-versa.

Since the vacuum effect will be working on the throttle body end where air rushes in, I believe you will be more likely to pool at the opposite end 1&2 when those valves are closed and air rushing in to feed 4,5,& 6 will make it difficult for the nitrous to easily move upstream to reach the distant ports since the air flow coming into the the TB will move quickest to alleviate vacuum that develops closest to it. In spite of the inlet angles the air travel is still moving with the direction of flow and branching off which could possibly have been thought of during design.

I could be wrong, but my experience with the injector is experience enough for me to avoid that approach.

I also thought in that direction when I mentioned moving the injector. Wouldn't the same effect you mentioned be on the 4,5,6 cyls be the same since the middle of the plenum has a tube extending beyond the center of the plenum? This means the charge would have to make a 180* turn to go from the TB to cyl 5 or 6 (more so 5).

Seems as though a dry shot might be the best unless that tube in the center of the plenum could be cut out for better distribtion of fuel?

I dont think it will be a problem since he's not boosting it to cause a positive pressure for the air to push it against itself. Will be a vacuum/draw towards the valves if anything.

I wouldn't chance it. I was turbocharging back before it was as popular as it is now and before tuning stock ECMs was as popular and practical as it is now back in 94. One way I dealt with the challenges was to add an extra injector at the back of the intake instead of at the throttle body end and I noticed it didn't seem to help the fueling problem according to the feel of acceleration until it was moved to the entrance end of the intake and I suspected it was pooling at the end of the manifold as a result of the air rushing in and preventing the injected fuel from sufficiently reaching the forward ports .

Although he's not boosted, the flow dynamics in some ways are the same, nitrous distribution under load will have to travel upstream against incoming airflow and intake scavenging. I feel very strongly about the unlikelyhood that even without having to face a 90 degree turn it will provide better flow into the 5&6 port since air going to all pistons must pass cylinders 5&6 before they reach any others and not visa-versa.

Since the vacuum effect will be working on the throttle body end where air rushes in, I believe you will be more likely to pool at the opposite end 1&2 when those valves are closed and air rushing in to feed 4,5,& 6 will make it difficult for the nitrous to easily move upstream to reach the distant ports since the air flow coming into the the TB will move quickest to alleviate vacuum that develops closest to it. In spite of the inlet angles the air travel is still moving with the direction of flow and branching off which could possibly have been thought of during design.

I could be wrong, but my experience with the injector is experience enough for me to avoid that approach.

[1988GTU]

I dont think it will be a problem since he's not boosting it to cause a positive pressure for the air to push it against itself. Will be a vacuum/draw towards the valves if anything.

[IsaacHayes]

But then with the rush of air coming out of the neck that might still hinder it going to the 5 and 6 ports.

What about 1" or so intake spacer between the LIM and UIM with nozzles in that? TreeZ24 had a setup like that but sold it before he used it someone else is using it I don't know who though. Looked really sick and would be direct port.

[1988GTU]

I think the PS will be hitting the nozzle then. Unless you tap the underside of the plenum at that end.