Ok, i'm looking over a FI system again and have a question about the position of the injectors.

In this setup the injectors are pointing down into the intake, so not aimed at the valve.

Would this be a problem ?

 

Are you talking about a TBI system?

 

no, an independant throttle body setup

 

How many injectors are there?? if there is ONE per CYLINDER, and i'ts NOT aimed at the intake valve it will run like crap, or barely at all.....

if you have like 1-2 injectors in what's known as a throttle body...air valve , it's a throttle body injection known as TBI for short.....the one per cyl setup is known as DPFI, direct port, FI....meaning just above the intake valve....

 

1 per cylinder.

Are you talking out of your own experience. Ok, I would prefer injection at the valve, but this is not always possible.

 

There used to be this idea that the injectors should spray fuel onto the intake valve, but lately that has been rethought. It turns out it doesn't really matter much where the fuel is sprayed as long as it finds its way into the cylinder at some point.

 

As already stated, it doesn't matter enough to be concerned. As long as the fuel is introduced into the intake port there are no issues with differences in fuel distribution between cylinders. I like them pointed at the valve because it concentrates the detergents in the fuel on the back of the valve where they're needed most.

 

thanks guys

 

It seems slightly unusual, but I don't think it's a problem.

Could we get pics of this setup? I'd like to see how it's arranged.

 

http://i204.photobucket.com/albums/b...9vette/012.jpg

Best I could do is post the link here

 

Surround the link with img and /img in brackets...

Nifty looking stack setup. Where exactly are the injectors?

 

YES, directly from back around '92 or so when putting my own DPFI setup on a Pontiac 455 engine....with central mounted 1000 cfm Tbody up top center...looking like a carb......I went through two differant itterations of that intake manifold.....

and in fact I started with a dual plane mani making the line up of the injector tops impossible with a straight shot fuel rail as per usual for most installs....

second off, a TBI setup, with the large injectors mounted above the throttle plates, they **** down the shoot, and from there conducted to a cylinder as if it was a carb...same effect far as the intake is concerned....other problems remain...but another thread at this time....

SO, not knowing any better I was making my own induction system with a NASA sub contractor, hippy dippy welder working outta his basement near the Md/ Pa border....hell of a joint...VERY impressive...appearance besides, this man knew more about metals and metallurgy than anyone I ever met....bar none....

anyway he did the welding on the intake to match up the tbody up top center, and the pads/machining to do the injectors on the mani.....he had no clue how to AIM them though....

anyway....I had them aimed straight down, vertically, NOT TO DO THAT...the fuel pressures are far greater than any carb or TBI setup...so the fuel spray was diverted all over the intake bottom plane and left it soaking wet....starting was a bitch, and it wouldn't run much at all untill very hot...intake too.....

NOW, same identical setup, I had the injector mounting pads...all 8 of them redrilled to aim at the intake valves....it worked fine...

and the rest was history....freekng car picked up about 40% in fuel economy and pulled like a NASA rocket....

so the individual injectors mose definately need be aimed at the intake valve.....not an issue....look close at any designs....something I did not do, and it cost me 2 weeks time for the efforts....

 

No - the injectors don't need to aim directly at the valves. Mine just spray into the manifold. Here's what some Harley EFI designers had to say -
"We also designed our fuel injector placement so they do not spray directly on the inlet vlaves. Car guys figured that one out a long time ago. " Link

Corvettes original fuel injection didn't aim the injectors at the valves - they were somewhat upstream of the valves. And they wrote songs about it!!

 

{img}http://i204.photobucket.com/albums/b...9vette/011.jpg{/img}

If you look close at the fuel rails, you will see that they are aimed at an angle of 90° to the airstream

 

That manifold is probably made for Mechanical fuel injection. The injectors have a splash plate to direct the fuel down the air stream.

The best DFI 8 stack units that i have seen are made by Kinsler.

 

I have pictures of the underside of the injectors (when installed) and they don't have a splash shield

 

That's a beautiful manifold! I can't see any reason why it wouldn't work... Can you test it out before you buy?

 

No, that just it. I know I guy here called Boschvette had it on his C4 and claims good results, but i didn't get any reply's on my pm.

 

hi
sorry i have been away for work just thought i would let you know that i am back,if you have any questions let me know.
cheers boschvette

 

From what I have seen of the above pix....yeh.. the induction ports are long and very individual, and so with ram affect from length, maybe the exact aim of the DPFI injectors at ~40 psi is not all THAT critical....

totally differant animal than a modified carb manifold/airflow/industion system I was playing with....every DPFI sytem I have seen from a FACTORY BADGE....GM/F. et al....it's aimed toward the intake valves....

for all the world that system would work fine at higher engine RPM's...as did mine....back when I was doing my own custom setup...

so maybe it CAN be done....I still say it's bad practice....