I was considering trying some thing out on my l92/403 c5Z. Right now I am running the l76 intake and making very nice numbers (560/500)on pump gas and 13:1 SCR, 8.9:1 DCR. I am wanting to try the new vic JR for L92 heads, to try to reach my goal of 600RWHP N/A.

the basic idea I have, is injecting fuel from the injectors right under a 90MM FBW throttle body (facing straight up), bolted directly on top of the carbed intake via a machined spacer where the injectors will be mounted at an angle facing downward to the floor of the intake. this will be similar to a true carbed setup where air and fuel are intrduced at the beginning of the runners, and not fuel near the intake port on the head.

I think this setup would be a little less efficient as far as MPG goes, but I also think it may have some nice HP gains up top--better fuel atomization?

thought/ideas? has this been tried before? would it be worth the time and effort involved with designing this? I saw something a little similar in a magazine with a LSX style 871 blower with the injectors mounted on top.

Thanks for any info

 

i have heard that some engines really like the injectors to be miles from the intake at upper rpms. however i have heard other engine, making the same power, that it makes NO diffrence on! lol

Chris.

 

Theory is that since the intake is engineered to have fuel flowing through it, that this idea may help with top end power. I have heard that people that ditch thefuel injection for a carb, running the same intake see 25+hp. But I haven't seen any proof.

 

I have heard that the high up the intake runner you move the injector. The more HP you can make, but you will give up idle quality.
Bob

 

I was figuring on that happening as well, but I imagine with some tuning time, alot of that should be lined out. I was hoping for some more feedback about somone who has done this before....so either not many have tried or its a really stupid *** idea

I have the 1st version adapter plate made up to where the TB bolts to the plate, and the plate bolts to the top of the intake, and the injectors in the factory position. I will try this first and see what the dyno results are.

I'm in the process of designing a 2nd version adapter plate, that is thicker with injector holes bored in the sides. I am just trying to decide if i should do 4 injectors on 2 sides, or 2 injectors on all 4 sides (using fuel rails), and im also tossing around trying a flexible line coming from a fuel distribution block that way I can put the injectors anywhere I want--like a circular pattern around the perimeter of the intake opening or at the beginning of the intake runner.

 

Why don't you weld bungs higher up in the runners to run the injectors? Seems like your setup with the injectors at the TB base would be nightmare to accurately flow.

 

I considered that also, but there where a couple things that would make that a little more difficult to do. it would be hard to have a fuel rail supply the injectors since the top of the runners on a carb intake go in a somewhat circular pattern. If I can figure out a good way to use flexible lines to supply fuel to each injector off of a distribution manifold, then that will be an option also.

The main thing I was wanting to try to experiment with is getting the injector out of the runner all togeher, and have the fuel delivery resemble what a carb does and see if there is any HP increase. At higher RPM's/WOT, there will/should be a cloud of fuel in the plenum of the intake waiting for the next intake valve to open to charge the cyllinder. This is where I think the performance gain may be compared to an injector in the runner.

 

i heard the performance gaisn come from the fuel having more time even distribute in the air. this gives you a better air/fuel mix and thus more power.

the higher the injector presure the better also as this mists the fuel better and should with distriution in the air. i think there has been work on injector design to help this.

F1 engiens actually have the injectors at the entrence to the air horns.i have seen Vids on youtube of them on the dyno and you can see this cloud effect you talk of.

be nice to have 3 sets of injectors. the ones close to the ports for low rpm/low speeds. a middle set for higher engine speeds and say 75% throttle plus. then finally move to the third set as far from the ports as you can for WOT and the upper RPM band.

having said all that i have heard engines that make NO MORE POWER by having the injectors mounted further from the ports!!!!!!!!

Chris.

 

I have seen the videos you are talking about. If you look up cosworth or Renault dyno on YouTube, it's pretty awesome looking.

Allthis may be a waste of time, but I enjoy messing with things. I can never just be happy with how it runs currently. Regardless of injector placement, I amfefinately going to mount the tb directly on top of the intake to get around using a 90+ degree elbow.

 

I think for the money and time involved in something like this, it probably isn't worth it, especially on a pump gas street car. It's basically a Throttle Body Injection system used on some older GM EFI engines, like the 4.3L V6 S-10/Sonoma engines. The fastest All Motor LSX racers seem to stick with injector placement in each runner, and they're turning over 9500 RPM. They have, however, found power in a 4500 series throttle bodies rather than a single throttle body facing forward.

As for the blowers, they introduce fuel on top of the roots blowers to cool the rotors. Roots blowers are the most adiabatically inefficient means of supercharging (compared to twin screws/centrifugals/turbos) at higher pressures. A lot of the fuel never reaches the chambers and is used to cool the rotors instead.

 

I really wont have a whole lot of money in this, just some time. I figure if it gives me 20 HP's for about 50 bucks and and some hours with something to think about, it may be worth it. if it doesnt do anything for me, then it was something to try.

I have seen the gains with people going with the 4500 series TB, and it makes sense. It just sucks because i am limited to the 90 MM flybywire TB on the vette because it controls a lot more than just the throttle--TCS, active handling, etc...that i dont want to mess with on a street car.

I can see why you would want to inject fuel on top of a roots type blower especially, from what i understand it also creates a better "seal" between the rotors and helps create more boost alont with cooling them down. I just mentioned the injectors on top of the blower because it struck up the idea to try it on a NA setup and a starting point for a design for the fuel delivery to the injectors.

 

while your at it why not go for a ITB setup??? you could find 8 TBS on say a honda that are about 50mm each. then, as long as youi have the room, you can mount th injectors as far from the ports as you want! this is what i saw done on a BMW. the end of the TBs was sticking out the hood! lol

Chris.

 

You're in luck. Im just finishing my version 3, and it will use this idea. It should be pretty awesome! heres what i have so far: