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when to get bigger injectors?

T

Teal4Banger

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Jul 30, 2007
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Location
Iowa
So how do I know if I need to go larger with my injectors? I'm currently under the assumption that I will start running lean and throw a code. Is this right?

Also,

Does anyone know where I could get a ported head with a 3-angle valve job for a pre-98 zetec? I've been looking to have my worked, however the only couple of shops around that can do it don't use a flowbench so I'm hesitant as to how good the results will be.

Thanks.
 
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You can just buy a head off jegs.com or somewhere that sells the for racing head. I'm not sure if itll fit but you might want to look into that it comes ported and polished with valve job.
 
the FRPP head should fit without any problems onto ANY zetec. comes ported with larger valves and valve springs.
 
I've considered getting the FRPP head however a couple of issues come to mind:

1) The earlier zetec has hydrolic lifters
2) The FRPP head may need to have some holes plugged (I was told this awhile back, not sure by who)
3) The later head models also have a different mounting for the alternator (I believe), although I'm not sure if that matters

The head itself should fit, yes, although I'm wondering how much customizing I'd have to do.
 
i know a guy that has some 24lb injectors on the focus site i could hook you up with. i think they were somewhre between 75-100shipped. brand new and only used for flow benchmarks. :shrug:
 
Not to hi jack...but I got some 24's from a taurus. I'm using my 19's out of my svt, so i have no use of the 24's. PM me for more info/discussion...
 
This is all great, guys.. but you're failing to answer his question.

He didn't say he WANTED to buy some.. he said he wanted to know IF he needed any and how to know.

The best way to find out is to find out is to take your injectors, and figure out max flow with them. work with 85% duty cycles to be safe. Once you know that, you can figure out how much fuel you can POSSIBLY use. In order to USE that much fuel, you'll need air. Find out how many counts your MAF is getting (or how many CFMs its measuring, etc) and calculate how much fuel its using to maintain your desired (programmed?? stock??) AFR and see if you are coming close to your max for your injectors.

Of course, you could just find a way to measure duty cycle and fuel output WHILE under WOT and see if you are approaching the limits of the rating, but I've never done that.
 
This will help:
ButtonPuncher said:
I've seen the question of "How big do my injectors need to be for XXX horsepower?" With more and more Contique Zetecers going FI, here's some good info.

(injectors size*number of injectors)/0.55=Crank Horsepower

19# Injectors=(19*4)/0.55=138HP
24# Injectors=(24*4)/0.55=175HP
30# Injectors=(30*4)/0.55=218HP
42# Injectors=(42*4)/0.55=305HP
50# Injectors=(50*4)/0.55=363HP
60# Injectors=(60*4)/0.55=436HP
61# Injectors=(61*4)/0.55=444HP
71# Injectors=(71*4)/0.55=516HP

Please keep in mind that these numbers are all for crank horsepower and that you never want to run an injector wide open. With a 90% duty cycle you would get the following...

19# Injectors=((19*4)/0.55)0.90=124HP
24# Injectors=((24*4)/0.55)0.90=157HP
30# Injectors=((30*4)/0.55)0.90=196HP
42# Injectors=((42*4)/0.55)0.90=275HP
50# Injectors=((50*4)/0.55)0.90=327HP
60# Injectors=((60*4)/0.55)0.90=393HP
61# Injectors=((61*4)/0.55)0.90=399HP
71# Injectors=((71*4)/0.55)0.90=465HP

Again, these numbers are all for crank horsepower. You would loose an additional 10-15% of your horsepower with a manual and 15-20% with an ATX.

You also want high impedance injectors that have Bosch (EV1) style connectors.

CFM carries them in sets of four and have very good prices. McNews Automotive also carries the Ford Racing injectos in sets of four.

I hope this helps.

Later,
Ben
Click to expand...
 
So assuming I don't replace my injectors initially, what symptoms would i notice if the load becomes more than they can handle?
 
Once you do a full intake, exhaust, UDP, and tune you will be at the limit of your stock injectors. Zetecs are rated at 125crank stock, after the aformentioned bolt ons you will be near the limit of stock injectors from what I understand.

If I upgrade my injectors I would go with 30#, from my understanding going over is no problems (correct if I'm wrong).
 
going over (to an extent) isn't a problem IF you can tune the car.

85% of a 19lb injector is obviously a lot less fuel than 85% of a 30# set. swap 30's in there and do NOTHING more and you are going to be running really rich. You need to tune it to run with different injectors.
 
Ahh, I was thinking injectors went by amount of flow, not load %. Good to know.
 
Exactly. Also, if you monitor your fuel trim via OBD-2, you will see how lean that you are running.

Teal4Banger said:
Any thoughts on what I'd see as far as symptoms of maxed out injectors?
Click to expand...

Instead of monkeying around with larger injectors, I'd just throw an adjustable fuel pressure regulator on. That way you can bump the pressure up for each mod that you add. ('til a point that is) Over 65psi and your injectors will start dripping at idle.

It is a 15 minute job and is a HUGE improvement over the stock FPR. I'd also recommend a Walbro fuel pump to keep the pressure up. Especially if you have over 100k.

You would want a Aeromotive 13102. You can get one at Summit.

striker2 said:
the FRPP head should fit without any problems onto ANY zetec. comes ported with larger valves and valve springs.
Click to expand...

The only issue that I know of is that the timing belt idler/tensioner is different on a pre-98 Zetec head. I still need to get off my butt and verify what is needed to drop a FRPP head on a pre-98. I have both just collecting dust in my garage. :troutslap:

HTH,
BP
 
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Thanks for the info guys, that's what I was looking for. So I now I need to decide whether to go the fuel pressure regulator rout or the injector route. What are the benefits/drawbacks of each? Right now I'm thinking it would just be easier to get larger injectors and a new tune (ala x-cal tune).

Also, anyone else have any experiences with an FRPP head and a pre-98 zetec? Would the larger valves be a negative since I'm going N/A? I read on some exhaust site that too large of valves can have a negative impact - don't recall the argument though.

Thanks again
 
The nice thing about a FPR is that you can adjust your "fuel map" with a screwdriver. You don't need to pay someone $100 each time that you need an updated tune.

The FRPP head would be a MASSIVE improvement. The CNC's ports and larger valves will just let the engine breath better. It will only make things better. Just check out the dyno comparison thread.

Just the FRPP head is worth 18HP. When you add on cams and cam gears, you are into the 40-50HP range.

I currently have a FRPP head in my possession. I just need to find out what the differences are in the timing belt setup.

BP
 
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