Bigger injectors and fuel useage.

I have a 1990 mustang gt that is bone stock. Someday I would like to fabricate a turbo for it. (I like fabricating).

Anyway, I know adding a turbo necessitates increased fuel and a "computer tune". 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 the size of the injector or strictly the computer? (i.e. if you have a bigger 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 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 possible but it seems anything that ads power hurts gas mileage.

Anyway I appreciate the education!

wrote in
:

>
> I guess what I am confused about, is whether fuel useage is determined
> by the size of the injector or strictly the computer?


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.


> (i.e. if you
> have a bigger injector, but the fuel demand is stock, does the
> computer only allow the amount of fuel that is needed to be delivered?



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


>
> I would really like for this thing to have a little more power, but to
> be 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 possible but it seems anything that ads power hurts gas
> mileage.
>


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

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

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.

Mark Olson > wrote in news:bn6i3cFqaijU2
@mid.individual.net:

>
> Which is why many high performance motorcycles[1] have dual injectors per
> cylinder,
> [1] Don't know about cars but I wouldn't be surprised if they also do it.
>


Not any of the usual road cars I know of. Maybe the supercars do.


--
Tegger

On Wednesday, February 26, 2014 7:35:07 AM UTC-6, wrote:
> I have a 1990 mustang gt that is bone stock. Someday I would like to fabricate a turbo for it. (I like fabricating).
>
>
>
> Anyway, I know adding a turbo necessitates increased fuel and a "computer tune". 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 the size of the injector or strictly the computer? (i.e. if you have a bigger 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 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 possible but it seems anything that ads power hurts gas mileage.
>
>
>
> Anyway I appreciate the education!

I am not trying to re invent the wheel, but read when adding turbos you must 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 more gas?

wrote:
> I have a 1990 mustang gt that is bone stock. Someday I would like to
> fabricate a turbo for it. (I like fabricating).
>
> Anyway, I know adding a turbo necessitates increased fuel and a
> "computer tune". 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 the size of the injector or strictly the computer?
> (i.e. if you have a bigger 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 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 possible but it seems anything that ads power hurts
> gas mileage.
>
> Anyway I appreciate the education!


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=101

No butchery required, street legal, smog legal, bolt on in a few hours.
AND comes with support and warranty.

Steve W. said




You come across as kind of dick, just thought you might want to know.

On Wed, 26 Feb 2014 09:13:04 -0800 (PST), wrote:

>On Wednesday, February 26, 2014 7:35:07 AM UTC-6, wrote:
>> I have a 1990 mustang gt that is bone stock. Someday I would like to fabricate a turbo for it. (I like fabricating).
>>
>>
>>
>> Anyway, I know adding a turbo necessitates increased fuel and a "computer tune". 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 the size of the injector or strictly the computer? (i.e. if you have a bigger 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 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 possible but it seems anything that ads power hurts gas mileage.
>>
>>
>>
>> Anyway I appreciate the education!
>
>I am not trying to re invent the wheel, but read when adding turbos you must 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 more gas?

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.

On Thu, 27 Feb 2014 01:51:26 +0000 (UTC), "Homer.Simpson"
> wrote:

>Steve W. said
>
>
>
>
>You come across as kind of dick, just thought you might want to know.

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.

Homer.Simpson wrote:
> Steve W. said
>
>
>
>
> You come across as kind of dick, just thought you might want to know.

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.