Bigger injectors and fuel useage.

I have a 1990 mustang gt that is bone stock. Someday I would like to fabric ate a turbo for it. (I like fabricating).
Anyway, I know adding a turbo necessitates increased fuel and a "computer t
une". I cant afford to do everything at once. Which got me thinking.
I have stock injectors. I think they are 19 lbs or something like that. If I were to put 42 lb injectors or whatever on it, with a stock motor, would it use more fuel?
I guess what I am confused about, is whether fuel useage is determined by t he size of the injector or strictly the computer? (i.e. if you have a bigge r injector, but the fuel demand is stock, does the computer only allow the amount of fuel that is needed to be delivered?
I would really like for this thing to have a little more power, but to be h onest, I like the 21 mpg I am getting when I drive to work which is about 2 0 miles one way. I would like to keep the gas mileage good if at all possib le but it seems anything that ads power hurts gas mileage.
Anyway I appreciate the education!
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snipped-for-privacy@yahoo.com wrote in

Both. Injectors will have a flow rate that's measured in liters per minute at a certain fuel-pressure. The injectors are closed until the computer pops them open. Injectors are either open or closed, never half-way. The "open" time is measured in milliseconds and is called "dwell".
The computer will be programmed for a specific "map" that takes into account the amount of fuel the injectors will deliver at the specified pressure, and opens the injectors the correct number of milliseconds depending on the amount of fuel that's supposed to be delivered with each opening of the injectors.
Generally speaking, bigger injectors mean more fuel flow, unless you shorten the dwell time. I think you can only shorten dwell time so much before it gets hard to control the injector precisely, so you'd have a practical limit on injector size.

If it's programmed that way, yes. Programming makes ALL the difference.

I suspect you may spend more on your tuning project than you'd ever save on gas trying to make the new setup fuel efficient and powerful at the same time.
Automakers spend millions trying to do just what you contemplate doing. All those new turbo engines aren't being built because buyers want them, but because the new CAFE regulations essentially bully automakers into building them, while buyers still want their power.
--
Tegger

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On 2014-02-26 8:37 AM, Tegger wrote:

Which is why many high performance motorcycles[1] have dual injectors per cylinder, as fueling needs vary over such a wide range between idle and making close to 200 hp. They can make the throttle control excellent at low loads by only turning on the smaller injectors, and as the load goes up they can use any combination of the two.
[1] Don't know about cars but I wouldn't be surprised if they also do it.
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Not any of the usual road cars I know of. Maybe the supercars do.
--
Tegger

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On Wednesday, February 26, 2014 7:35:07 AM UTC-6, snipped-for-privacy@yahoo.com wrote:

icate a turbo for it. (I like fabricating).

tune". I cant afford to do everything at once. Which got me thinking.

f I were to put 42 lb injectors or whatever on it, with a stock motor, woul d it use more fuel?

the size of the injector or strictly the computer? (i.e. if you have a big ger injector, but the fuel demand is stock, does the computer only allow th e amount of fuel that is needed to be delivered?

honest, I like the 21 mpg I am getting when I drive to work which is about 20 miles one way. I would like to keep the gas mileage good if at all poss ible but it seems anything that ads power hurts gas mileage.

I am not trying to re invent the wheel, but read when adding turbos you mus t increase injector size. I am not sure if this is true or not.
So, if I bought bigger injectors for my stock 5.0, will it run right? Use m ore gas?
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On Wed, 26 Feb 2014 09:13:04 -0800 (PST), snipped-for-privacy@yahoo.com wrote:

I think going to 42 lb injectors would be way too much. I think people used to put 26 lb ones in when the put better heads on them. IAC, it will partly depend on just how much of a pressure boost you use. If you do a mild boost of 6 psi the factory injectors might work. If you go up to 15 psi you'd surely need bigger ones. A really good blower mod could add as much as 50% more power at wide open throttle so you'd need roughly 50% more gas. 19 x 1.5 = 28.5 lb. I'm sure it's not quite that simple buy you get the idea. I think with an unmodified engine you'd be pushing thing a lot at that level.
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snipped-for-privacy@yahoo.com wrote:

Good luck, Hope you have a spare car so the engine failure in the Mustang doesn't leave you stranded.
You have it correct, ANYTHING that adds power costs fuel mileage.
If you want real advise. Leave the Mustang alone and go buy a toy with more power.
First off that is a 1990 engine, which means it is already well worn.
Second you don't just bolt on a turbo. You need to alter much of the engine if you want it to work and be reliable. Which is why there are turbo specific engine parts.
Third, you don't even understand fuel delivery and you want to add a turbo!!! You do your own heart surgery as well??
Here is a simplified version of fuel delivery:
First you have your fuel pump and pressure regulator. They keep the fuel rail at around 40 psi.
Second you have the injectors - nothing more than a solenoid controlled nozzle.
Then you have the ECM - it controls the injector by pulsing it on/off. More on time = more fuel into the engine.
Now the stock system is designed to work together. The ECM knows the flow rate of the stock injectors at the specified pressure.
It uses a simple table in memory to cross reference the O2 readings with the MAF readings and the TPS position to control fuel delivery.
So what will changing the injectors to ones that flow over twice as much fuel do when the ECM is programmed for stock flow? (hint, twice as much fuel and no extra air)
If you want more start researching.
If you want increased power and maybe close to stock mpg (IF you keep your foot off the pedal) you would be much better off to look at something like a bolt on Paxton system
http://www.paxtonauto.com/product.php?id 1
No butchery required, street legal, smog legal, bolt on in a few hours. AND comes with support and warranty.
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Steve W. said
You come across as kind of dick, just thought you might want to know.
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On Thu, 27 Feb 2014 01:51:26 +0000 (UTC), "Homer.Simpson"

I personally think he comes across as someone who really, really, knows what he's talking about. A lot of posters come up with some bad ideas, and, in my opinion, Steve is making an effort to warn them off of those bad ideas before it's too late.
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Homer.Simpson wrote:

If me sounding like a dick means he doesn't do something really stupid and destroys his vehicle then fine.
He admitted he didn't understand how the injectors are controlled BUT thought that installing units that flow twice the amount of fuel would work.
--
Steve W.

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On Wednesday, February 26, 2014 9:35:07 PM UTC+8, snipped-for-privacy@yahoo.com wrote:

honest, I like the 21 mpg I am getting when I drive to work which is about 20 miles one way. I would like to keep the gas mileage good if at all poss ible but it seems anything that ads power hurts gas mileage.

If you put in bigger injectors before the supercharging, you are going to run richer -- for a short while. Most ECUs use a slow average of the exhaust oxygen sensor to tweak the maps . It will keep shortening the injector pulses until it gets back to the correct air-fuel ratio. It is possible that if you double the flow rate of the injectors, your ECU might not be able to shorten the pulses enough and you would waste fuel.
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On 2/26/14, 16:35, snipped-for-privacy@yahoo.com wrote:

Which got me thinking: why the fuck do you want to mess with something that you'd likely to get worse by your tinkering. The fuel system would be the last on my carfuck list due to the potentially costly consequences. And since you have make it clear the money are an obstacle I just have to remind you of the possible unsuccessful and costly outcome that pedro 1492 have explained in another reply.
In fact I would not even fuck with the needle sizes in a carburetor. Get an ECU into the picture and it's just becomes "forgetaboutid".
You do know that carburetor (and injectors by extension) in french means "don't mess with me", right?
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On 3/10/2014 6:16 AM, I hate front wheel drive, send most torque to the rear, please wrote:

Note that most professional racing series are moving towards "control" ECUs to reduce costs - but then a shade tree mechanic knows more than a MotoGP privateer team, eh? ;)
--
T0m $herm@n

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Thinking of just 6psi On Wednesday, February 26, 2014 7:35:07 AM UTC-6, snipped-for-privacy@yahoo.com wrote:

icate a turbo for it. (I like fabricating).

tune". I cant afford to do everything at once. Which got me thinking.

f I were to put 42 lb injectors or whatever on it, with a stock motor, woul d it use more fuel?

the size of the injector or strictly the computer? (i.e. if you have a big ger injector, but the fuel demand is stock, does the computer only allow th e amount of fuel that is needed to be delivered?

honest, I like the 21 mpg I am getting when I drive to work which is about 20 miles one way. I would like to keep the gas mileage good if at all poss ible but it seems anything that ads power hurts gas mileage.

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