Fuel pressure regulator placement
Discussion
A friend of mine has a rally car (Datsun 1600), and has recently fitted a fuel injected engine (Vipec).
The fuel system was professionally done (hard lines, proper fittings etc), but the installer mounted the FPR in the return line at the tank, rather than at the fuel rail.
As I have taken on tuning duties for the car, my first question is are there significant downsides to the mounting position (apart from the return line seeing full rail pressure) ?
As I see it, the pressure at the injectors will vary with the return flow, decreasing as the consumption goes up
, but until I get a pressure sensor fitted at the rail and do some monitoring, I don't know it it will be significant or not.
Also, he has a cheap adjustable reg that I don't like the look of : will it be better to junk it and just get a good quality fixed reg, and re-map to suit?
I am a novice at mapping, but have a good theoretical understanding, some very experienced tuners for help and advice, and unlimited dyno time. However, I want to get the basic fuel system right first.
The engine was tuned in its previous owner's car : my work to date was simply to adjust the fuel pressure without changing the map, to get the AFR in the (safe) ballpark, and the mixtures (and power) are pretty good. However, we will be doing some work over the next couple of months, and I want the basic fuel system right before I start changing things.
I had to wind the fuel pressure up to 60 psi (4 bar) to get the AFR around 13:1; is 4 bar a reasonable fuel pressure if I go to a fixed regulator?
Engine is 2.2l 4 cyl naturally aspirated, with 50mm ITBs.
ps I would like to go variable speed pump drive one day, but not just yet : as it is a forest rally car, the alternator has to drive a lot of lights, so current draw is not an issue, and with only 200-250 hp, the fuel pump is not huge anyway.
The fuel system was professionally done (hard lines, proper fittings etc), but the installer mounted the FPR in the return line at the tank, rather than at the fuel rail.
As I have taken on tuning duties for the car, my first question is are there significant downsides to the mounting position (apart from the return line seeing full rail pressure) ?
As I see it, the pressure at the injectors will vary with the return flow, decreasing as the consumption goes up
, but until I get a pressure sensor fitted at the rail and do some monitoring, I don't know it it will be significant or not.Also, he has a cheap adjustable reg that I don't like the look of : will it be better to junk it and just get a good quality fixed reg, and re-map to suit?
I am a novice at mapping, but have a good theoretical understanding, some very experienced tuners for help and advice, and unlimited dyno time. However, I want to get the basic fuel system right first.
The engine was tuned in its previous owner's car : my work to date was simply to adjust the fuel pressure without changing the map, to get the AFR in the (safe) ballpark, and the mixtures (and power) are pretty good. However, we will be doing some work over the next couple of months, and I want the basic fuel system right before I start changing things.
I had to wind the fuel pressure up to 60 psi (4 bar) to get the AFR around 13:1; is 4 bar a reasonable fuel pressure if I go to a fixed regulator?
Engine is 2.2l 4 cyl naturally aspirated, with 50mm ITBs.
ps I would like to go variable speed pump drive one day, but not just yet : as it is a forest rally car, the alternator has to drive a lot of lights, so current draw is not an issue, and with only 200-250 hp, the fuel pump is not huge anyway.
I would use a good quality regulator and I would mount it in the normal location after the rails and close to the engine.
It can work where it is now, but it would depend on overall fuel flow required, size of lines, pump ability etc.
If you want to leave it at the rear, you probably would be best just running a static high base pressure like the 60-70psi you've already tried. Don't use the vac reference.
But best just to do it right.
It can work where it is now, but it would depend on overall fuel flow required, size of lines, pump ability etc.
If you want to leave it at the rear, you probably would be best just running a static high base pressure like the 60-70psi you've already tried. Don't use the vac reference.
But best just to do it right.
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