I recently went through a BIG buildup and one of the things that I got was a blueprinted TBI from Turbo City. THe problem that I am having is the injectors (stock 305) do not have a wide enough spray pattern. They hit the blade then run down. This is causing the car to suck a lot of air and not enough fuel. Then the computer trys to overcompensate by dumping A$$ loads of fuel in and it doesn't run right. Now I want to say that I have the injector pod spacer already on teh TBI. I have also had 350 injectors on it that I got aftermarket. The same problem occours. Anyone else have this problem? If so, How did you fix it? I am a little baffeled as the car now has tripple the power of stock and is slower because of little stupid stuff like this.any comments welcome as I have no idea how to fix it. THanks guys

Eric

 

No one here has had this problem or knows where to get the stuff to fix it?

 

Try inreasing the height of the injectors from the throttle body, maybe you can work with 2 injector spacers and with a fuel pressure bump get the spray radius to be larger so it'll hit the walls.

 

Why do you think having the fuel spray hit the throttle venturi walls is a good idea?

The airflow goes to zero at the walls, so you promote fuel dripping into the manifold by coating the throttle venturi walls.

--- 9/8/02 edit ----
I'll answer my own question.

You DON'T want to injector to spray fuel the walls of the throttle venturi because the airflow velocity goes to zero (it's a boundary layer thing).... and the fluid would then tend to stick to the walls from surface tension. BUT, that would only be true for WOT. At all other times, i.e. part throttle, the airflow is almost entirely through two crescent-shaped openings of each throttle blade, so the injector targeted to somewhere in the middle of the throttle blades (by the factory) is a comprosmise between optimum operation at WOT, and optimum operation at part throttle. Well, as optimum as one can be with a TBI system that injects above the throttle blades...

Raising the injector pods to redirect the fuel spray to the walls, as if often done by TBI owners, probably helps more at part throttle, but it doesn't appear to be optimal for WOT use. btw that's all based on theory, not on practice. I have yet to see anyone test the theory in a meaningful back-to-back test..... FWIW.

--- end edit -----


As far as EROCK's problem, I suggest you try using the stock TBI to see if you still have the same problem(s). The stock TBI will be small (volume flow-wise) at high rpms, but it's not likely to have the other problems you are having.

I think you also said that you tried two sets of injectors and they both did the same thing. That sounds like lack of fuel pressure, which could mean a fuel filter clog, or a faulty FPR, or a bad fuel pump, or some combination of these.

 

as far as this whole fuel thing goes, the spray cone should hit just above teh throttle blades. Theres a sticky dedicated to this topic at the top of the tbi board, have a look. Screw the spacers. Use thick and thin washers inbetween the pod and the tb. The bolts will hold the washers in. By using washers, you can fine tune the hight of the pod to get the spray cone off the throttle blades and on the walls just above them. My stock one did the same thing and it made allt he rear plugs dirty. More likely its inadiquate fuel delevery, though. What do your blms look like, if theyre off the hook then your computer isnt coming nowhere near close engough to feeding the engine. If this is the case, you should check the fuel system and burn a prom for your new motor. Oh, if you dont have winaldl or some other equivelent program, now is the time to get it.

 

I know that the fuel pressure is correct and the filter is new and been changed twice since all this happened. It has done this ever since the re-build. My injectors come up off the TBI pretty good. Unfortunatly putting on the original TBI is not an option because you have to send it for a core charge. I am sure that the computer is confused also since the motor has been re-built. I had a cam custom cut for the car and had the heads flowed with a bigger throttlebody and much bigger fuel and I have NOT changed the stock chip. (too expensive right now) The engine builder is the one who noticed the injectors not spraying correctly. It just sucks sooo much air it sounds like a jet air liner taking off. We did a vaccuum test and it is not a vaccuum leak. That is when we noticed the injectors are hitting hte blades right in hte center with fuel.

Eric

 

lol... theres a great thread at the top of this board dedicated tot he topic of fuel dist. in a wet injection system, go read it if you havnt yet.

 

Yeah. I saw it. I realy could not see how it could help me though. I would have to stick my injectors 3ft. out of the hood to get it to spray just above the butterflies. The cone is only like a cenemeter wide! Bought new (stock) injectors lthis morning. Changed them on my half hour lunch aned they do the SAME THING.

 

What do you have your fuel pressure set at?
BTW, this doesn't sound anything like an injector "spray" problem and more like a tuning issue. You're probably WAY off on AFR's so your BLMs are maxed out OR you've set your timing up all wrong. Do plug cuts, hookup a multimeter to your ecm to read the o2 volts, recheck base timing and set it up the correct way not just loosen bolt and turn retighten!
BTW, that whisling sound is the IAC, it's loud when it's trying to compensate for some problem in your tuning.
What heads are you using, what cam, etc. You're probably running lean if you haven't touched the fuel pressure and are using stock 305 injectors. This is a VERY bad thing. Don't run the motor lean unless you intend to rebuild it with ALL new parts after the piston melts.

 

I know how to set timing properly. don't assume everyone here is stupid. I have checked the air/fuel ratio at all rpm's. The car is not running lean at any point. (of course it is not rich either) 350 injectors actualy SLOWED trhe car down. Stock heads cnc ported to 235 cfm, polished too. The cam has a 565 lift but I realy don't see where this has to do with an injector spray. I have the fpr set much higher than stock with a high flow Holley fuel pump. Like I said...it is NOT running lean. I just want the injectors to spray a wider cone. Anything else I can answer to help? Let me know

Eric

 

Here's a quick diagram of my interprestation of his problem...

Diagram 1

The spray pattern does not cover the whole area of the 2 inch bore, leaving a large gap of air to freely flow by the throttle body and not interact with the fuel at all. Note that with such a narrow spray it basically lets the throttle blades deflect the fuel all to the rear of the engine under part throttle.

Diagram 2

My interpretation of a proper spray pattern, also what the GM techs were taught too. The spray covers the area of the bore thus not allowing the air to pass without interacting with fuel. Under this setup under part throttle the fuel will condense along the walls, but it doesn't really matter since it vaporizes when it comes into contact with the manifold bottom if it makes it that far. Also note that the spray avoids the throttle blades altogether, thus leaving the blades to direct the wet air flow, but since its not forced induction, vacuum works quite evenly to distribute the fuel.

Result, my plugs were close to identical when I changed them a few days ago. A nice tan brown color to all of them, front and back. Power that is only off a TPI engine of similar setup to my car by 2 tenths of a second and a trap mph better than the aforementioned identical TPI setup.

I basically have the spray hitting the walls just above the throttle blades and ensuring the throttle blade does not interfere with the conical spray even at WOT. Thus any air that has to get into the engine has to pass throught the spray. More air goes through the spray, the more fuel will get sent along to the engines, since its vacuum that brings air in, not forced induction it turns out that the throttle blades do not curry favor to the rear of the compartment if this is all setup correctly.

This setup works well for me, fuel economy is great, 28 mpg avg and power is there 89 mph 15.8 1/4 mile.

 

See...now that is what I call help. Great diagram. I see what you are saying. That is what the engine builder said. The spray needs to be just before the blades and the air will come through the spray. But however it does not answer the question...How do I get mine to spray that way. The injectors are not clogged. Would I be an "idiot" (to quote my previous post) in thinking that the computer controlls this (i wouldn't know how) or do I need injectors special ordered to spray wider? If it is computer controlled (again...I wouldn't know why it would) then once I get the new chip (i still have the stock one after the re-build) It will fix it.

Eric

 

By the way...Your number one diagram in your drawings is still a MUCH wider spray than my injectors. Probably almost double.

 

Well take my advise or leave it, I'm telling you right now it's a tuning issue and those 305 injectors are NOT correct for your application especially if you're running the heads and cam you say you are. I have YET to see any difference in drivability when the fuel hits the throttle blades OR when I spaced it to hit just above. Get 350 injectors and decrease fuel pressure. I have a feeling that too much fuel pressure and your stock eprom are the reasons your car is running like crap.
Again, take it or leave it but there has never been a case of injector spray pattern that's effected drivability to such an extream as you say it is. So waste your money on new injectors and telling me that I'm wrong, be my guest, just don't go asking for "help" and then telling somebody that their help is "wrong."

 

I hate to say this, but the spray pattern DOES matter. I've talked to the GM techs on this. The atomization of the fuel is very dependent on whether the air passes through the spray or not.

If the spray hits the throttle blades, there is more tendancy for the spray to condense and pool. We don't have to guess, Erock's going through it already.

In that arrangement, fuel has a harder time atomizing and more than likely large amounts of air are flowing though without interacting with the fuel. I find it hard to believe that you can have the fuel hit the throttle blades, condense and pool and not suffer drivability and economy issues.

As for my advice, I'd do everything possible to increase the diameter of the spray. Have you increased the fuel pressure?
Is the spray diameter even large enough for the stock throttle body? the stock diameter was 1.693 inch. The spray with 305 injectors is should be more than 1.693.. even so it should be with a 1/4 inch spacer large enough for 2 inches.

Fuel pressure and height can dictate the spray pattern. The ecm only meters the fuel, that is to say operates how many times it fires the injectors. It cannot dictate how the spray patter is.

I have some questions though, is it despite its small diameter a perfect conical spray?

Try bumping up the fuel pressure, see if that helps. The only other idea I have is that the injectors are not designed well with the proper o-rings and spacing to form a wide spray.

 

Hell, go do both. Go get some 65 pph injectors and space them properly using washers or tbi spacers. Those 305 injectors are nowhere enar adiquate. I had trouble with them and i have a lame 200 HP 350. Aftert hat, see where you stand. Like everyone else says, youll want to burn a prom for that engine to get it all to work properly

 

Thanks slade 1 for backing me up. It DOES matter. Pretty bad when the moderator has to yell and put ya down all the time. Oh well. Anyways back to the problem... I had 350 injectors and they slowed the car down too. Plus fuel literaly dripped off of them no matter what I did. I used every rubber and o-ring properly and just to be sure I had the engine builder re-do it. We tried adjusting the FPR (thank goodness for ultimate TBI mods!) adjusting literaly everything and both sets that I bought (two different kinds) all just dripped fuel. WAY too rich. The lines have been checked from the pump (ok) to the filter (2 new ones) to the lines (ok) to the tbi (ok) to the FPR (ok). Just realy confusing. That is why I am wondering how to get them to spray good. A realy good cone. I am still baffeled.

Eric

 

If the injector dripped they probably had slight cavatation, thats assuming your o rings were right. And I agree with JPrevost, your problem if simply tuning, thats it, nothing more nothing less. Also I agree that it doesn't really matter were your spray hits, be it on the walls are not. Think about a carb, there is no cone spray, and they Idle fine. yours doesn't because the ECM is limited to the amount of fuel compensation it can do, you've probably crossed its threshold, so now it has trouble maintaining a good idle. Now I say all this because I have actually tried sticking my fingers under both injectors while at idle, causing them to drip, and not spray. The motor stumbles at first, then recovers to a smooth Idle.

 

And about making the spray cone larger, I just put another injector spacer on. I run 15 psi at the injectors. So if raising your injectors, and fuel press. doesn't help, the injectors must be junk.

 

Oh I am sure that they are junk. The only problem is that I am not sure which ones to get. Like I said, I had 350 injectios before so I am scared to spend $200.00 again. You cannot return them once they have been installed. Are the ones from turbo city any good? I have tried other 350 injectors too and my et never changed but maybe a thousandth or two. They run the same as the 305 ones do.

So if my problem is tuning like everyone says what else is there to tune? The timing is set where it is best, fuel is correct, plugs are new, wires are new, fuel filter is new...what else is there? Just PROM right?

Eric

 

Exactly, you need to tune, the computer takes areading from the O2, then makes a correction to the base pulse width of the injectors. If the gains and biases are off, then the engine can start to cycle or run poorly. I would strongly suggest spending your money on tuning eqiupment, rather than new injectors. You should be able to get set up nicely for under $300. Check out the prom board, it has lots of posts on what you will need. A few years ago before I knew how to tune I had a bad bog at 4000rpm, I convinced my self than it was something physically wrong. So I replaced about $300 worth of parts, and it still ran just as bad. The problem was tuning.