FAST 36# injector data for 98 corvette return fuel system?

[myws6formula]

I know these injector data threads pop up fairly often looking for injector data when using the 3800 sc injectors / FAST injector but I can't find anything for these on a return system.

If I could take a peak at the sc3800 file it would likely have what I need but that doesn't seem possible since EFILIVE does not support the OS.

Anyway does anyone have the data when used on a 97-98 corvette?

[macca33]

I copied the data from the Corvette ASA tune on TuneFileDepot. Dunno if that helps your application though.

cheers

[myws6formula]

I will have to check for sure but I had been told the 98 asa tune had incorrect injector data. they changed the flow but nothing else

[krisr]

I did the same as Macca when I put FAST 868 injectors into my Monaro and just nabbed them from the ASA tune. In my instance I found they changed more than just flow data when I used the parameters after my upgrade from 28lb/hr injectors. The injector pulse width adjustment was slightly different and I *think* the minimum IPW was slightly different too.

[maudyZ28]

the tune in the thread here is what i used

http://forum.efilive.com/showthread.php?20205-corvette-ASA-2000-tune-strange-spark-v-high

the data is the same as Mr prick posts later on anyway. there may have been a problem with the 98 ASA tune but it apperas the flow data on this 2000 tune are ok. As Krisr says there are more than flow data tables that are different

[myws6formula]

but since the 98 uses a return rail the flow changes and so would everything else.. I cant be the only one using these with a return rail can I?

[joecar]

Which year/model/vehicle do you have...?

1997 Corvette had a MAP-reference return fuel rail (FPR at the rail).

1998+ Corvette had a un-referenced returnless fuel rail (FPR at tank).


Are you sure your fuel rail is the return type...?
Do you see a reference hose connecting the FPR to manifold vacuum...?

[joecar]

If you do have a return rail then do this:

from the tune file mentioned above you copy all the injector tables;

then in B4001: copy the zero MANVAC cell to all other cells (flatline);
then in B3701: copy the zero MANVAC row to all other rows;


important: measure rail pressure, if it is not 58 psi then fix the cause.

[myws6formula]

13954

this is a swap motor.. (back when I did the swap I had to order the fuel rail and had to use a 98 corvette vin to get it since it was back ordered by gm).

using a 411 pcm with a 02 f-body OS but currently has the 98 injector tables in it.

Thanks I will have to sit down this weekend and set this up so I can install the injectors

[myws6formula]

I'M not sure im understanding correctly. if I flat line the flow rate with manifold vacuum it will be off.


I say this because if i look up a stock corvette tune the injector flow still has a slope.

[joecar]

Manifold-referenced: IFR = flat

Un-referenced: IFR = sloped.

[myws6formula]

if thats whats needed I will do that but whats got me is the way both the 97-98 corvette tunes have a slope stock. yet the 5.3 truck is flat like you are saying

[joecar]

Yeah, that is pretty weird, I too saw that and wondered why/how it was like that.

[voda1]

On 97 Vette air tube from fuel pressure regulator connects to the air bridge between MAF and throttle body. What is it referencing?

[joecar]

On 97 Vette air tube from fuel pressure regulator connects to the air bridge between MAF and throttle body. What is it referencing?Which side of the throttle body (is it on the manifold side, i.e. after the throttle blade)...?

That is what referencing is.

With manifold referencing, the air hose is the the MAP reference, it adds MAP to the pressure side of the the FPR so that the regulated pressure is base pressure plus MAP (i.e. FP+MAP), this is the pressure on the top of an injector;

the pressure on the bottom of an injector is manifold pressure (MAP);

so the pressure difference across an injector is constant (FP+MAP - MAP = FP) regardless of manifold pressure, so the IFR table is flat.


Edit: my comprehension skills just improved a little (coffee)...

voda1 said the reference is between the MAF and TB, i.e. it sees barometric pressure (thanks Greg)...

ignore what I said above this edit, the 1997 Y-car FPR appears to not be MAP-referenced.

[eficalibrator]

On 97 Vette air tube from fuel pressure regulator connects to the air bridge between MAF and throttle body. What is it referencing?

Barometric pressure. ;)

[joecar]

I reread what voda1 said... the "air bridge between MAF and TB"... so what Greg said makes more sense, and explains the IFR being sloped in the 1997 Corvette tune.

[joecar]

Greg, that explains about the IFR, thanks :cheers:

[myws6formula]

Oh ok, that makes more sense. thanks guys! also explains where the tube goes as well

[joecar]

The GM Service Manual says this for 1997 and 1998 Y-car:



The fuel pressure regulator is a diaphragm operated relief valve with fuel pump pressure on one side and regulator spring pressure on the other side. The fuel pressure regulator is vented to atmosphere. A software bias is used to compensate injector on-time because the regulator is not referenced to manifold vacuum. The injector pulse width varies with the signal from the MAP sensor.
...

[myws6formula]

oh sure rub my nose in it LOL honestly though I never looked I just figured like every other GM or car that I have ran into with a vacuum port on the regulator it went to manifold vacuum.

If nothing else it should help anyone who searches in the future

[joecar]

lol, not your nose, but my nose...


I figured just like you...

I would see the hose (and it disappeared under the "Corvette" cover) and I assumed it was the manifold-reference...

but at the same time I was puzzled by the IFR table, and for some reason it never occurred to me to check the Service Manual until today :doh:



I corrected this thread (post #1): Calculating-Injector-Flow-rate (http://forum.efilive.com/showthread.php?4821-Calculating-Injector-Flow-rate)