24# Injector ??

[ZEN50]

Hey all,
Have this GT40 crate motor that I picked up from Mike last month and it came with 24# injectors with matching mass air meter. Also will be installing Cobra intake, 65mm TB, 1.6 rollers, headers, etc.

Was wondering if this is a worth while upgrade or stay with the stock 19#? Do I need to upgrade the fuel pressure regulator? Will the A9L be happy with the 24# parts? Just curios to see what others think.

Thanks,
Zen

[homer302]

24# would be perfect for your combination I think. Also, I believe what matters is the Mass Air has to be calibrated to the injectors, not the ECU so in your case you should be good to go. Hopefully others will confirm that.

[Fastlane]

Like what Homer302 said, the most important part is the Mass Air Calibrated to the Injectors. I currently have a similar setup, Cobra intake, GT40 heads, 24lb injectors. Stock 89 Mustang cam and CPU and the engine runs fine.
I also have an 89 Mustang, with Edelbrock Heads, E Cam, Cobra intake, 24lb injectors, stock CPU and it also runs fine.
In both cases the Mass Air is calibrated for the 24lb injectors.

[erratic50]

The purpose of a MAF is to measure the density - the mass of the air - at the current atmospheric pressure and temperature. It's done by the rate in which pulling the volume of airflow across the sensor cools the sensor - thus changing the sensors output voltage.

Not to oversimplify there's a proper way and an improper way to setup a performance application and generally we as a group know the difference.


Why upgrade injectors? Simple - 19LB/HR injectors are at 100% duty cycle at stock fuel pressure at 320 HP. So basically any HO is an intake swap away from being past the recommended 80% duty and should use bigger injectors. Yes you can do more stuff and get more power after an intake swap with 19's, etc - not the point. The point is bigger injectors are made for a reason.

Why not just calibrate the MAF? A "Calibrated" MAF is really a bit of a hack. Like when you jack up the fuel pressure on your undersized injectors, etc. From a programming perspective, tuners consider them as actually a screwed up MAF when you boil it down. Many refuse to tune without an un-modded MAF. Why? . It results in some untunable conditions that ultimately rob a lot of power from the combo.

Basically you are telling the computer the car is being ran in a place that requires way less fuel so you can get the computer to reduce the injector pulse width but when it does that it usually also pulls out a bunch of timing. Thus a major reason some nearly stock HO's keep up with or pass other heavily modded cars.

Opinion - do not get a calibrated MAF- it's a bandaid.

IMO what you need to do is get a 70MM MAF and use it with a normal stock (some may call it a 19 lb/hr) calibrated MAF sensor. Get a 1993 Cobra "X3Z" ECU as that computer knows it has a stock MAF calibration and it also knows the injector size is 24lb/HR --- not 19! Autozone and other big box auto parts stores carry remanufactured ones for cheap or the factory parts are out there but more expensive.

This is one readily available parts way to run 24's. Other options include aftermarket computers, custom chips, and mod boards like the Moats Quarterhorse. Tune options combined with tools like Binary Editor work excellent to adjust a stock A9L tune for 24lb injectors, larger displacement due to stroker kits, etc.

The spark maps are slightly more aggressive on the A9L so retuning it for 24lb injectors may be worth the expense in terms of power output vs the cobra computer. Guys that pull their cobra computer and add a tuned A9L initially reported gains in the 30HP and 40 lbs torque range compared to the stock cobra ECU - albeit this was later debated as being a case of insufficient base timing on the motor for the cobra ECU setup to reach full power levels of advance with its less aggressive spark tables.

Expense wise I would go cobra ECU rather than a 'calibrated MAF' initially. You can always tune it with A9L spark maps later. This is simply going to perform better.

[ZephyrEFI]

Interesting thread. I'll join in. I have GT40P heads, Explorer intake, 24 lb injectors, and a calibrated MAF. I do have a manual, but my engine originally came auto, so i'm running an A9P. It runs okay for now, but my plan is to get a cam, probably a TFS1 or similar and then get one of those doo-hickeys you plug into your EEC-IV and can then tune it.

Here's my thought on buying a Cobra computer. Anything that is prefaced with the word "Cobra" is instantly a ripoff. The guy sitting on the part just sees dollar signs. "Cobra brakes", "Cobra rack", "Cobra seats", "Cobra intake", etc. It's criminal how much guys pay for Cobra intakes over Explorer ones. I can't say I've never fallen for the glamour of owning a genyoo-wine Cobra part, but if there's a better way on the computer end of things, I'm going to go with it.

[erratic50]

http://m.autozone.com/engine-managem...ntrol-computer

stores in my area show $207.99 + $42 core for a 1993 cobra ECU. Sku 78-4352
OEM #F3ZF-DA, DB, E9ZF-AA

CA legal ones are Sku 78-5595. $158.99 + $42.00 core
O.E.M. #F3ZF-CA

In the past they've accepted any EEC-IV as the "core".

For what it's worth, there's what the cobra part costs. It can be found cheaper if you dig.

A bit of a toss up A9L with tuner vs Cobra really. If tune board fails at they do, not having the cobra would be the regret as the car won't run. Maybe an A9L with a burned eprom chip instead of an insertion board is the best answer as then it's factory reliability with a proper tune and good spark advance curve.

The cobra intakes are different than explorer. The runners are longer because they are designed for 1500-6500 rather than 500-5800 like the Explorer. Tom Moss built a short runner Explorer upper with ported lower. He said It picked up 0.2 in the 1/4 compared to stock explorer but did not best the Cobra intake, only all but tied it. In a race application, the short runner like the Cobra will run better. In a street application most will prefer the Explorer.

personally for now I prefer the Typhoon - damn the looks it pulls past 6500 if you have a bottom end that will support it and it's far less expensive. Edelbrock RPM was definitely ripped off on this but surprisingly dyno pulls show typhoon lowers outperforming and Edelbrock uppers being the better ticket. Combine them or port one or the other I guess.

If I had my ultimate choice I'd take a tubular GT40 with a ported lower as those do the business down below 1500 and outperform most while looking gorgeous doing so. But that is way out there on priority list for me. What I have now runs really strong considering what it is.

[ZEN50]

Wow, a lot info there Erratic50, but sounds like you know your stuff! Will take it all in to consideration.....

Also the crate motor has a B303 Motorsport cam in it. Not sure if that makes a difference?

I am by no means an engine builder, tuner or anything like that. Just trying to put together a nice street combo with what I have.

[erratic50]

Hey thanks - have done a ton of homework over the years on these things. I still feel like I have a ton to learn but enjoy the hobby.

Letter cams like the B cams were all the rage at one time. There are a lot of better cams out there now. I'd hit up comp or Anderson, etc.

That said, just a stock HO cam is a lot more capable than its often given credit for. Especially with 1.7:1 rockers.

Really depends upon how you want it to sound and run like. Bigger cams give bigger power but they aren't as friendly to the street, etc.

[ZEN50]

Yeah what I currently have is an brand new/old GT40 crate motor that was built in the late 90's by Ford. This thing has never been run and has B303 installed along with iron GT40 heads. Going to stay with that combo and the plan was to install the 1.6 rockers & #24 injectors & meter. All these parts came included with motor and was hoping (for now) to not have to purchase other major parts. Already have the Cobra intakes, 65 mm TB that are currently on my tired 86 GT motor.

[FoxChassis]

erratic50: I agree with your assessment on "calibrated" MAF sensors. They are a bandage and in my opinion not the right way to do things. I never liked the idea of trying to "fool" the ECM. Much better idea to tune the ECM according to the mods.

However I disagree that an intake swap alone will max out the 19 lb/hr injectors (@ 39 psi and 80% duty cycle). For that to be, an intake swap by itself would have to be worth over 25 HP on a stock 1987+ H.O. 5.0L engine (50+ on a 1986 H.O. 5.0L engine). Which intake, and just that intake by itself, would do that? I would agree that stacking a bunch of mods beyond just an intake swap alone would necessitate larger injectors.

[erratic50]

I should have qualified - intake swap assuming open exhaust such as 1 5/8" headers and 2 1/2" X pipe and flow masters along with at least a 65MM throttle body and 70 MM MAF and aggressive timing.

Im running an A9L with E6 heads and typhoon with open intake and exhaust. My motor seems to go lean at around 5800 which agreed is high RPM for an 86 long lock. My motor has a very mild speed density friendly cam that was done in the late 80's. It's running with a 155 lbh fuel pump that's maintaining good fuel pressure but it leans out when my timing is set on full tilt and I'm approaching 6250. I cranked up the fuel pressure slightly and reduce timing to compensate but I know from reading the plugs that my old smoker is at her limit maybe past.

The injectors are very high miles but clean and work well even with more fuel pressure. Solving it with more pressure and less timing caused me to conclude 19's are all in with my combo. I have an A/F gauge I've been meaning to install to prove it, but like most guys I know lean with too much timing when I hear it.