Where to place injector bungs on Tunnel Ram manifold

[CDMBill]

This has been discussed in another thread, but I thought I'd start a thread specific to this topic. So, is there na ideal location for injector bungs on a tunnel ram. I understand that there may be a benefit to having them higher up on the runner, but there may be driveability issues.

Any one have comparative experience to share?

[dieselgeek]

My own limited experience with injector placement says, on the street driven car, go with a low-in-the-runner placement and aim for the back of the intake valve if you can.

A best of both worlds approach would be an injector up high, just below the common plenum, and another way down low. Stage the injectors up high for power at WOT, then use the down-low injectors for all other operating loads/RPMs.

I only have testing experience on ONE engine (Engine Masters) to back this up, but what we observed seems to jive with what all the current sport motorcycles are doing: 1 up high, 1 down low, for each cylinder. In the tunnel ram, I guesstimate you would not see the same benefits of the high mounted injector because it's located so close to common plenum area. And what I know about high injectors mounted close to the plenum chamber is that, in an aggressively-cammed N/A engine, all kinds of weird shit can happen - thanks to pressure waves and "whatever weird stuff happens in there" - I think in your case it's best to keep them in the bottom 50% of the runner if possible.

The high mounted injectors in our EMC engine were worth just a few percent average power across the entire curve also. In EMC it was worth the effort, but on a street engine I'd keep them lower so you can avoid lean running outside of the powerband. We killed an engine while learning this stuff.

[TC]

Interesting enough, some guys will mount the secondary injectors above the throttle blades. Search Shower Injection.......

[BKBridges]

EFI, my reason for being...
What DG said... Injector placement for race only vehicles gets pretty imperical based on the actual intake tract configuration, average RPM target, Injector size and atomization performance, and etc... On a big motor, high RPM usage (road racing) set-up, the injectors are usually big, and until lately had less than stellar atomization. Droplet entrainment into the runner air flow helps atomization through turbulence. A few diameters is usually the "rule of thumb" for a starting point to assure entrainment, but that varies depending on the "straight shot" into the head, manifold config, etc. At low RPMs, the entrainment is not as good and may lead to dropwise runner condensation on a less than stellar manifold design. Ive got a few cross ram intakes from Motec that have the injectors mounted in various locations based on intended application. They vary from 6.5" away from the port to 3" away from the port. they were all purchased orig by an outfit setting up a Lemans motor for chryco, so Im assuming the variations were part of the tuning program. They finally settled on the approx 3" away from the port location. The injectors were placed under the manifold due to the "straight shot" into the port available there. If youve got a Mill and a tig welder, you can pepper the manifold with bungs and have a go on the dyno!
Bruce

[dieselgeek]

Outstanding post!!! we are lucky to have BKB here. I sure hope he's not doing EMC this year :-)

[BKBridges]

DG Thanks!
I did work on an EMC motor with IMM in Indio last year. Unfortuneatly we started the EFI conversion late, tried to tune the motor on the hottest weekend on the year (in Indio, 118degF) and finally gave up on the crating day due to a connector issue with the FAST system...Brian's motors do rock though! the motor made good numbers wioth the Holley 1000 but it was an illegal config for a carb per the rules. Im pretty sure we would have been handed our Ass by the GenIII hemi even if everything went our way. I sure wouldnt mind helping out on another EMC attempt though! We would have benefitted from some time to try various injector placement locations as well as TB/adaptor configs due to reversion issues, but the weather was the real killer.
BKB

[Bob Holmes]

Great post BK, and thanks for the pictures.

I really wanted to try a couple additional placements last year, but we just ran out of time. I would still like to try a mid runner placement, just for comparison purposes. It was basically a pure science project, though, because it wouldn't have been legal to run the injector there in competition.

[Bob Holmes]

Bill, does anyone make an IR for your combination?

[Beagle]

BK's pictures just made me slobber a little. Clean up on aisle 3. That makes me want to stop typing and get out in the garage. Thanks for that!

[dieselgeek]

BK's pictures just made me slobber a little. Clean up on aisle 3. That makes me want to stop typing and get out in the garage. Thanks for that!

x2

so much for the belief that EFI intakes & TBs are always ugly!

[BKBridges]

x2

so much for the belief that EFI intakes & TBs are always ugly!

Oh Yeah...
( except for this...)
Actually its the TBs and air inlet/filter for a stroked 5 liter prowler's tunnel ram. Looks better there.
Im running out of cool stuff...
Bruce

[TheSilverBuick]

haha, nice.

[CDMBill]

Kinsler makes a very nice IR setup for my heads (tfs a460) but not cheap. The injectors are mounted inboard. I've seen the set up on a big inch SBF trophy truck motor and it looks cool and made 815 up on a 440 that will run WOT for hours in the dirt, amazing.

[CDMBill]

I spent some time talking to Wilson Manifolds today and they have their own theory on the location of the injectors so I'll end up with them about two inches up from manifold flange. They claim to have a CNC program for my manifold/head combination which was based on some trial and error as was suggested above by BKB.

Had to make a decision as I'm running out of time. It may not fall out of tree but it'll be pretty.

[JeffMcKC]

Its very close to where mine are Bill