f recommended injector size

[f85gtron]

I would like to know the recommended injector size to go with when replacing...  i also was wondering if any of you have had yours professionally cleaned and matched?  If you have, who did you use?
Ron

[TopNotch]

I haven't used them, but I hear they are the best: Fuel Injector Connection. And they are local, so you can take your injectors to them instead of relying on a shipper.

[Fierofool]

After having several 3.4 installs done with injectors of my choice, (302 Mustang 19# and the stock Rochester 17#) and having a rich burn problem with both, I went to FIC when I had my engine done.  I explained to them about the Fiero ECM and Multec or disk type injectors being rumored to be incompatible.  John was aware of this since he used to race Fieros when his father owned a Pontiac dealership.

He recommended a pintle injector that is used in the BMW V8's and has so far been without problems.  A scan done by Radar showed that there was a slight lean burn, but it hasn't caused any problems in 10,000 miles.  I would highly recommend them for cleaning, rebuilding, flow matching, buying a rebuilt set or a new set. 

I believe he had also told me that he can modify injectors for the flow that's needed for the engine.  Just because they're rated at 17# doesn't mean they are locked in to that flow. 

If you're running a stock 2.8 then 15# injectors are recommended.  17# for a modified 2.8 and stock 3.4 and possibly 19# for a modified 3.4.  If you're running the Fiero ECM, stay with pintle injectors. 

[Raydar]

He recommended a pintle injector that is used in the BMW V8's and has so far been without problems.  A scan done by Radar showed that there was a slight lean burn, but it hasn't caused any problems in 10,000 miles. 

Since you mentioned me specifically, I feel the need to chime in.
A "slight lean burn" is not entirely accurate. It is a lean burn that the ECM is attempting to correct for, and is all the way to its limit and is still not able to add enough fuel for a proper mixture.

Those injectors may be 17 lbs., but apparently not at the stock Fiero fuel pressure.
Based upon the scans that I've done, they don't appear to flow any more than the stock injectors, at the stock fuel pressure. They may (don't know for sure) have other characteristics that allow them to work properly at higher pressures, where the stockers possibly wouldn't. Since BMW calls them "17s" I have to ASSume that's the case.

[f85gtron]

Ok, thanks.   So, with a stock motor, stick around 13-15#?  Other than port matching and rockers, i don't plan on any major mods. I'll try to send off my existing stock injectors and see if they're good enough to rebuild and match.
Ron

Edited to scratch the 13# injector.....

[Fierofool]

I didn't understand how the ECM program worked with injectors, so that's why I thought it was just a slight lean burn.  Not being able to keep the injectors open long enough.  The BMW injectors were rated at 16.66 lb/hr, at the same stock pressure as the Fiero.  This is generally tagged as 17 lb./hr. 

Injectors which are left open to the air for any length of time can suffer oxidation on the valve seating surfaces, very quickly.  I found this to be the case when I sent the set that was working very well in my old 2.8 that was replaced with the 3.4 and BMW injectors.  They had been in a box on the shelf for about a month and as the fuel (ethanol added) evaporated, parts began to rust.  It was suggested that a small amount of kerosene be added to the top and bottom ports, then placed inside a baggie to keep them lubricated and moisture from attacking them.  Probably even a light amount of machine oil will work since the cleaning service will dissolve it.

[f85gtron]

I checked out that web site.  I'll call them tomorrow. They have new injectors on sale.  I wonder if it would be better to clean the old ones, or to buy the new ones?  They also have injectors for 3.8's on sale. What would happen if i ran those?  Would my 2.8 run too rich, or would the ecm compensate?
Ron

[Fierofool]

I believe they have a table on their site for determining injector size based on a couple of plug-in parameters.  Injectors for a 3.8 would probably be a little too much for a 2.8 with stock pressure regulator.  In my case, I could have gone with an adjustable pressure regulator and maybe remedied my problem, but that wasn't the path I chose.  I wanted to keep things looking stock and not have to deal with trying to make adjustments to correct problems.   

Their house brand Blue Demon injectors seem to be able to be built to fit the needs of your specific application. 

BTW, the injectors I have in the 3.4 are Bosch injectors.  If you're going into a 2.8, they would be overkill. 

[Raydar]

I didn't understand how the ECM program worked with injectors, so that's why I thought it was just a slight lean burn.  Not being able to keep the injectors open long enough.  The BMW injectors were rated at 16.66 lb/hr, at the same stock pressure as the Fiero.  This is generally tagged as 17 lb./hr. 

To clarify... The injectors are probably capable of supplying plenty of fuel. There is a "lean-to-rich window' in the ECM, that allows it to compensate for a measured rich or lean condition (according to the O2 sensor.)
The problem is, the ECM is up against the top of its "window" and cannot add any more fuel. The two best ways to add few would be to have a larger injector at the same pressure, or more pressure behind the same injector.
My "band aid" fix is to "open that window" farther, to allow the ECM to add more fuel. And that's all it is, is a band aid.
There are other methods that will work better, but they take more time. I *almost* had it right with my built up 3.4, but I ended up selling the car. As it was, I drove it with the 19# injectors and the "wider window" for several years, until I had the time and the inclination to start fiddling with the tune, again. (My problem was exactly the opposite. The 19s were giving it too much gas.)

The 3800 injectors are (IIRC) also at least 19#. Maybe larger.

[Fierofool]

I found the calculator tool on their website.  You put in the Crankshaft HP and number of cylinders and it will tell you what the injector size is.  The injectors actually flow slightly less than what they're rated at.  It's like the displacement numbers for engines.  They're actually a little smaller than the 3800 or 3.4 or 2.8.  They just round up to an even number. 

[aerodonamic]

I have done two installions of the BMW injectors, one on my 3.4, bored 20.00 over and one bored  30.00 over and setting fuel pessure at 48lbs.This is stock setting. I did not have an adjustable fuel regualtor as it was no longer necessary. I had been using the adj. type set at 55 to 58 lbs. with the 2.8 injectors. I have run these apx. 50.000 miles with no pobrlems. Not sure about Gharleys install. I purchased both sets from                         injector connection. You will find John both helpful and very knowlegable . Hope this helps you in picking the correct injector for the job!!!aerodon.

[f85gtron]

Thanks. 

[Fierofool]

The service manual for both 2.8 and 3.4 says the fuel pressure should be 43.5 at key on, engine not running.  It may require more with a bored engine. 

[f85gtron]

Not to talk this subject to death, but......
I'm only planning on converting to 1.6 full roller rockers and porting/port matching. So, my question is;  are 17# injectors necessary, or will blueprinting oem injectors due?
Ron

[Fierofool]

You're starting with 140 crank horsepower in the 2.8.  Add the horsepower generated by the rocker conversion and the port matching to get your gross crank horsepower.  Then use the calculator chart on the FIC website.  There are two parameters already entered.  Those are valid for the Fiero.  By doing that, you can avoid an adjustable fuel pressure regulator. 

Since the 3.4 engine is rated at 160 crank horsepower and uses 17# injectors at 43.5 psi, I would think you'll be OK with the 17's.  You might be close to the 160 mark with your mods to the 2.8.  I'm estimating 10 hp on the roller rockers and 10-15 on the port matching.