Angle of the Dangle - Injector Aiming

[ItsA68]

I am looking at the available IR setups out there, and all the alternatives. I like the kinsler, but it really seems that their injector bungs are aimed completely wrong on the SBC manifolds. Theirs are mounted on the outside of the runner, and they appear to be aimed against the other wall. Isn't it always best to aim the injector directly at the back of the intake valve? It would seem the only way to properly aim the injector would be to mount in between the runners in the valley area. TWM seems to think that this is important, and it makes sense. I think you could also do a decent job if they were mounted right down at the bottom of the runner near the head, on the outside edge, just like the single plane converted carb manifolds are done. I'm sure Kinsler knows what they're doing, but I'm really confused by their design. What gives?

I've been reading about the challenges of using and living with the IR setups, so I wouldn't want an additional problem if the injectors are not aimed properly. I figure one of these setups is easily worth 30ft/lbs throughout the entire torque curve up to 7 grand.

[Fuelie Fan]

I'd tend to agree for the most part. But, if you think about it, DIRECTLY at the other side might not be so bad, as the fuel might just bounce back into the airstream. Imagine washing your car: You're not dumb enough to point the hose directly at the body, becuase you know you're gonna get soaked. But, as you change the angle, gradually less is reflected. In the port, you WANT the fuel off the surface of the runner. You really want to avoid just coating the walls of the port. Would I do it that way? Probably not.

If you can get the spray to the valve, the OE trend is usually to run a very narrow (they're called "pencil") spray pattern injector. The problem with these are, if your aim is off, then you will hit the port at a shallow angle and have horrible mixing. OR, if your injector timing is off, you'll be firing a highly concentrated (not easy to evaporate) spray right into the combustion chamber, basically getting no pre-mixing at all. So, most aftermarket guys prefer medium spray cone angles of around 20-30 degrees and pointed "in the general direction" of the valve. This way, their aim doesn't have to be exact and they get pretty good mixing regardless of valve timing because the cone doesn't impact the wall for a pretty long time, allowing some mixing with the air charge to occur first. And, when it does hit the wall, it doesn't have to far before it reaches the hot valve. Without the R&D necessary to perfect the aiming, that's what I would do, and it sounds like that's what TWM did. If you plan running at 7000+ rpm, you might want to read the other post I made concering Larry's setup and consider moving your injectors further upstream in the port.

[tireman]

I had the same worries but with some small injectors on an old-style manifold (the barrells are farther apart). I was able to mount them on the inside and spraying directly down the port. The spray pattern is aimed directly at the back of the valve down the port.

[ItsA68]

wow! that looks like a cool setup. The fuel rail looks trick. Most are plain ole aluminum extrusions. Did you do the conversion yourself? What are the hose connections on the outside of the throttles? Are those the connections for your MAP? I guess you tune the runner length with the ram tubes right? Those runners are really short. I like the one piece design. Kinsler is now selling a 3 peice setup, which is great if you have raised ports, or a tall deck, etc...but for plain ole 23° heads and a stock type block, its a pain because of the lack of crossover for the water outlet.

~~fred

[OHCbird]

OEMs put the injector at that angle (as in the LS1s) for emissions; it's designed to work in conjunction with the port swirl. I was real worried about my injectors being at 25 degrees, but I've been guided by higher authority that it's not that critical on our applications (mainly street).

Hell- the NMRA guys point some of them backwards (about 20 degrees) to get better fuel atomization. Of course, we're talking about 2000hp cars flowing some serious air.

[tireman]

Those connectors on the outside are for the idle air control. I have some connectors in the inside that are for the MAP circuit. They are Legris type connectors using nylon lines.

The fuel rails were made from MSD injection parts. The runners are short, but then you add as much trumpet as you want or can fit up top for tuning. One thing I liked about this manifold is how close the throttle plates are to the valve. The closer, the better, for throttle response.

[ItsA68]

I heard that you are best to have two different taps in the runners for Idle air, and for MAP, its hard the see the ones on the inside.....Do you really need idle air control? It just bypasses air past the throttle plates to maintain a steady idle speed right? It doesn't seem like it would be completely necessary. I DO want to have AC, so I guess it would be good to have a way to kick up the idle speed when the AC is running. How important is idle air control to have a consistant idle speed? Do each of the runners have an individual air bleed so you can balance all 8 of them. (I have a VW with two IDFs, and a unisyn, so this is no new trick)

Thanks,

~~fred

[tireman]

For my IAC circuit, I have a manifold with a line running to each port under the throttle plates. I do not have a way to adjust the relative amount of air running to each port, but I hope that it will be good enough.

As for the necessity of the IAC, I don't really have enough experience to say. I know I wanted it for the AC and also because my motor needs to idle as low as possible so it will shut off (lots of compression).

[BBPanel]

Do you have a measurement of the distance between stacks (bank-to-bank)? I've got a BBC hilborn manifold that I wanted to put the inj on the inside like you did but I don't think there is enough room. The BBC stacks curve inward which may the reason there is not enough room and it will also make it difficult to drill. Thanks. -Bob

[tireman]

On my manifold the throttle bores are 6 3/4" apart center to center.

[BBPanel]

Thanks for that info - I went to the MSD website and cannot find anything about the inj/fuel rails you are running - do you know if they have info on their website about them or am I just looking in the wrong place. Thanks. -Bob


Ahh wait a minute - are the tops p/n 2115 noted in their catalog?

[tireman]

P/N 2115 is what I used....

[Firehawkslp]

For my IAC circuit, I have a manifold with a line running to each port under the throttle plates. I do not have a way to adjust the relative amount of air running to each port, but I hope that it will be good enough.

As for the necessity of the IAC, I don't really have enough experience to say. I know I wanted it for the AC and also because my motor needs to idle as low as possible so it will shut off (lots of compression).

Tireman : I always thought that run on after shutoff wasn't a problem with E.F.I. because when the ignition is turned off, the injectors close. So no fuel no cumbustion.

[tireman]

Firehawkslp,

I hope you are right. I don't have my system installed yet (still making the air-box and stuck in France until November). Right now with the carb, I have to hit the AC to get it to shut off without dieseling. With sequential EFI and the IAC motor, I figure I have the best chance of getting out of that without having to reduce compression. I ain't givin' up power without a fight!