From the tests that Rob Logan did (and published to the LML). If you are really seeing 1.5" of MAP in addition when RAM is on, then you are right on the ragged edge of the stock injectors leaking fuel all over the tops of your cylinders.  :)... (actually, it's not that bad, but yes, they will leak).

 

Rob found that just north of 1.5" of MAP on RAM would cause the stock (non turbo-railed) injectors to leak fuel.  I think it was Mike Mahar that has made some sets of rails to solve this problem and at well south of what you'd have to pay for the rails from TCM.

 

I'm gonna wait and see what I end up with for RAM on mine, but will most likely look for a solution to the leaking injector problem.

 

Search the LML for Robs original posts and pictures, he made many tests primarily around improving RAM performance for "stock" racing, and found the injector leaking problem.

Alan,

 

Interesting.  My engine manual calls for a fuel pressure (delivered to the throttle body) of between 12 and 45 psi.  During normal operation the pressure is at 26-28 psi.  Assuming constant fuel delivery and that Bernoulli was correct, the flow and pressure should overcome minor back pressure in the induction system.  Results may vary.

 

Anyhow, see

 

 

Part number 2090137 for air rails.  They do not cost what TCM would charge.  I have a pair of such rails for "4-cylinder engines" and they are nicely made.  I cannot use them because they needed more room than my tight cowling would allow.  Also, I still needed a plenum to distribute the air to each rail or a second inlet (Mark has 2 pitot tubes next to one another).

 

With efficient ram air delivery to the induction system, the orientation of the bleed hole and the resultant cooling plenum air flow around the injector body can have an effect on the capability of the fuel to come out of that hole.  I don't know (or remember) the orientation of injectors on engines other than my Lyc 320, but the general rule for installing injectors bodies is to have the bleed hole facing the sky within a torque range.  Other orientations (facing the earth) may allow fuel to leave and stain the area around an injector on any engine not painted blue. 

 

Stopping a big engine with long injector lines on a hot day might allow the rising engine heat to boil off fuel in those injector lines.  The expansion might just force some fuel out of the bleed holes instead of the injector nozzles (depending on their orientation).  Bummer. Shrouded injectors may not eliminate the event but they can contain the cooking fuel so as not to stain a pretty engine. 

 

Of course, if fuel was being wasted (exiting the bleed holes) in cruise flight Rob would have seen quite a change in the gph rate and/or performance.  Perhaps he remembers the difference.  Rob?

 

Results may vary.