Fuel Pressure regulator / Damper

horsman_f3 · horsman_f3's Garage

What is the difference between a fuel pressure regulator and a fuel damper? How many of each are used?

sausagehacker · sausagehacker's Garage

FPR maintains pressure in the rail at a certain spec.
Fuel Pressure Regulator - General Information and Replacement

The damper keeps that pressure from changing with every little pulse from the fuel pump. Think like a surge protector. Both work in unison to maintain an even pressure for the injectors.

The intake vacuum is supplied to both, and the changing pressure (which is tied to RPMs) changes the spec of each one as the needs for the fuel pressure change across the RPM range.

The 944 has one FPR and one damper.

veleno · 08-19-2014, 05:14 AM

^
what he said

horsman_f3 · horsman_f3's Garage

Thank you for the info!!

Lapponia · 08-20-2014, 06:23 AM

Hi folks! What other cars uses a damper together with a regulator? Been looking at You Tube about regulator issues but never a damper. Wouldn´t it be possible to get rid of the damper and run well without it. Just wondering.
Lapponia

Slam · 08-20-2014, 08:55 PM

Valid question. I believe it's there to even out drops or pulses in pressure that occur when the injectors open. I would think that rapid rhythmic pulsing of the fuel pressure would be an issue, but I don't really know. On one hand, Porsche does tend to answer nobody's question, but on the other the Germans seem to do everything for a reason.

Lapponia · 08-21-2014, 04:39 AM

Thanks Slam. I will dig into this a little deeper.

Jfrahm · 08-21-2014, 12:32 PM

I think the damper was removed in the 16v cars that ran much higher fuel pressure, perhaps with a faster recovery time in the system and no need for a damper. I think these cars also fire injectors in pairs which would reduce the need for a damper.

Offhand I would not bother engineering a way to delete it and just replace the hose and if need be, the damper.

speedysprocket · 08-22-2014, 06:08 AM

944S still has a dampener. 968 does not. I ran a 968 fuel rail on my S engine for a while. Didn't fit perfect, but worked, and noticed no difference.
For what it's worth, apparently the 968 was the first car with true sequential fuel injection, rather than firing all the injectors at once like the previous 944 engines...

Lapponia · 08-22-2014, 07:35 AM

I think I understand a little bit more now. All four injectors in my 944 NA fires at the same time but in pairs. This makes a pressure drop over each injector during the fireing period and there is also a pressure drop over the regulator by that reason. The damper takes care of that and makes fuel pressure more even during the fireing cycles. So, if my regulator is going out after 30 years, the damper is also on its way. Both should be replaced at the same time like the clutch slave and master cylinder I guess and they are not cheap.

Jfrahm · 08-22-2014, 07:50 AM

The regulator is used on other cars as well as the 944 and can be bought more cheaply via the Bosch part number rather than the Porsche one. The damper might last a while longer. I suppose fuel quality is the big factor, here in the states we messed around with some fuel blends that were pretty hard on seals.

0 280 160 227 I think is the part number, matches an old Saab 9000 as well.

Lapponia · 08-22-2014, 09:14 AM

Thank you Jfrahm, I will check this out. I´m sure there is a scrap yard around here that keeps SAAB (sweden) parts that will fit but new parts are better of course. I will also check internet for the part number as you suggested. Thanks again.

sausagehacker · sausagehacker's Garage

If you need a damper, I have one in working condition from a 85.5 944. $10 and it's yours.

Lapponia · 08-22-2014, 09:43 AM

Very kind offer sausagehacker, thank you. But I think I can find the item in a closer range or buy new ones.

cockerpunk · 08-22-2014, 09:58 AM

Quote:

Originally Posted by Lapponia

I think I understand a little bit more now. All four injectors in my 944 NA fires at the same time but in pairs. This makes a pressure drop over each injector during the fireing period and there is also a pressure drop over the regulator by that reason. The damper takes care of that and makes fuel pressure more even during the fireing cycles. So, if my regulator is going out after 30 years, the damper is also on its way. Both should be replaced at the same time like the clutch slave and master cylinder I guess and they are not cheap.

any centrifugal pump also has pressure waves that need to be dampened out.

fortunately work on the fuel rail is really quite easy on the 944.