Underhood temp. vs fuel pressure ???

[warren]

Question???

It's been in the 90's here and I noticed that as the intake air temp went up so did the fuel pressure.
In city traffic my intake temp with my CAI installed was 150+ deg's.
The fuel pressure went up at the same time to 50-55 psi.
on my ScanGauge.

Why does it do that and is this a bad for the engine etc.?

Warren

[Fast4Door]

Marauders have what is called an electronic returnless fuel system. The system does to main things:

1) It attempts to maintain a constant pressure drop across the injectors (relative to manifold pressure), usually 39 psi.

2) It jacks up rail pressure if fuel rail temperature gets high enough to cause the fuel to boil (vaporize) in the rail. The higher pressure stops the boiling, which is good. Injectors are supposed to inject liquid fuel, not vapor.

When underhood temps are very high, you can expect the rail pressure to increase.

The system is used to adress other fuel handling issues as well, but I don't think I have the time to discuss them tonight...

HTH

[Marauderjack]

Warren,

Fast4Door is dead on......My Autometer gauge reads 30 PSI while temps are low but will jump to 40+ PSI when under hood temps go above a certain temp though I don't know what that temp is. Autometer gauges read about 9-10 PSI low at idle but are right on the money off idle.....Same as my DiabloSport tuner!!:beer:

My ScanGauge won't read FP and the Diablo does at the same port!!??:argue:

How did you get yours to read FP??:confused:

Marauderjack:help:

[SergntMac]

My ScanGauge won't read FP and the Diablo does at the same port!!??:argue:

How did you get yours to read FP??:confused:

Marauderjack:help: Yes, I'd like to know this too. My ScanGauge doesn't report FP. What's up?

[MitchB]

Question???

It's been in the 90's here and I noticed that as the intake air temp went up so did the fuel pressure.
In city traffic my intake temp with my CAI installed was 150+ deg's.
The fuel pressure went up at the same time to 50-55 psi.
on my ScanGauge.

Why does it do that and is this a bad for the engine etc.?

Warren

This is right in the ECM calibration and what you see is supposed to occur. A 39 psi drop across the injectors is maintained for IATs up to 130. At 160, it ramps to 55 and at 170 IAT, pressure levels off at 62 psi.

Mitch