Manifold-referenced: IFR = flat
Un-referenced: IFR = sloped.
Manifold-referenced: IFR = flat
Un-referenced: IFR = sloped.
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
Yeah, that is pretty weird, I too saw that and wondered why/how it was like that.
On 97 Vette air tube from fuel pressure regulator connects to the air bridge between MAF and throttle body. What is it referencing?
97 Vette 6spd, CamMotion Titan2 LS1 cam, TSP 5.3 StageII heads, Vararam intake, Z06 manifold, ARH headers/cats, Z06 catback, Monster Stage2 clutch, 04 Z06 pcv, new style knock sensor(late98 to 04).
Using FlashScan V1 with NGK-AFX Wide band
Which side of the throttle body (is it on the manifold side, i.e. after the throttle blade)...?Originally Posted by voda1
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.
Last edited by joecar; October 2nd, 2012 at 04:35 AM.
Barometric pressure.
~Greg
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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.
Greg, that explains about the IFR, thanks
Oh ok, that makes more sense. thanks guys! also explains where the tube goes as well
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.
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