8 cylinder front engine iconic vehicle
  • User avatar
  • User avatar
  • User avatar
  • User avatar
  • User avatar
User avatar
By grepin
#188495
I am changing out the design of my fuel system on a 16V Euro. Getting rid of the two rear regulators and going to a single aftermarket reg. Is there any issue running the reg at the front of the fuel rails as against the rear. Hans I think you said keep it to the rear last we spoke. And yes starting to look at getting those rails installed in the new year.
User avatar
By Crumpler
#188575
Hey Greg, can't help but I'm following ;)

MY 85-86 only has one FPR (and two dampers), so I suspect you would be fine. Hopefully somebody can give you a more definitive answer.
Did you make an injector choice?
User avatar
By worf
#188576
You have a plan to reverse fuel flow through the rails if the regulator is at the front?
User avatar
By hessank
#188624
worf wrote: Wed Dec 14, 2022 9:55 am You have a plan to reverse fuel flow through the rails if the regulator is at the front?
The argument against installing it (FPR) at the front is that the fuel rails would not get enough fuel, as the fuel pressure regulator regulates the pressure in, and what comes out of it is the excess fuel/pressure (to the return line)

From my notes on this, I found these two pictures
You do not have the required permissions to view the files attached to this post.
Last edited by hessank on Wed Dec 14, 2022 12:45 pm, edited 1 time in total.
User avatar
By hessank
#188626
Not sure if my attachments were done correctly.
Sorry if it ends up as a double post

Here are pics of both positions
You do not have the required permissions to view the files attached to this post.
User avatar
By worf
#188638
hessank wrote: Wed Dec 14, 2022 12:38 pm The argument against installing it (FPR) at the front is that the fuel rails would not get enough fuel, as the fuel pressure regulator regulates the pressure in, and what comes out of it is the excess fuel/pressure (to the return line)
Exactly. So, if the regulator is at the front its “output” must be fuel return. Fuel supply must be plumbed to the rear.
User avatar
By grepin
#188712
Done the reg can remain at the rear. I have just gone with the Ford 24lb fat bodied injectors. Basically as the projection into the manifold will be the same as original fit and the possibility of still using the injector hold down brackets with the new fuel rail. The Pintle caps will need trimming or I may replace the cap. Not sure yet. Need them in my hand they are still inbound. I have also gone with the DWR 1000c reg. I was spoilt for choice there and still dont know why I chose it except that Hans recommended it and its compact size to fit down the back under the air box. Hence why I was sort of looking at fitting it up front where its easily adjusted and readable if fitting a gauge. But might cause a fire risk so may not be left in place.
On the other forums Lorenzo has taken the VEMS to a next level with a sequential injection and a waste spark set up that I am keenly following. Crumpler you may want to have a look as well.
User avatar
By hans14914
#188863
In "theory" you can install the regulator in front of the rails. This is a dead-head arrangement. It is not ideal, especially with batch fire injectors.

The biggest problem with a dead-head system is that there is no fuel that passes the rails during the fuel pump priming cycle. You will have hot-start and likely "vapor lock" problems. The rails will not be able to bleed the vapors until the injectors start firing, and you will have to pass all that vapor through the injectors before the fuel will be able to enter the rails.

It can be done with aftermarket EFI by increasing the injector priming pulses to compensate, but its still going to result in a less than elegant start.

If you really need to simplify the design, a series circuit instead of parallel flow will work better than a dead-head system. Parallel will always provide the most consistent fuel pressure to each injector in a batch-fire system. That said, if it's not an option, I would do a series system instead of dead-head.

As suggested by others, its fairly simple to re-route the plumbing so the fuel enters the back of the rails and meets at the regulator in the front. The lines would be a bit longer, but I suspect there is plenty of room to route the return under the manifold. The only advantage I could think of would be access to the adjuster, but you shouldn't have to adjust that after the initial set.
User avatar
By grepin
#188940
Thanks everyone. Appreciate the input. I will definitely run it from the rear. Glad I asked.
Bring A Trailer finds

That manual Cayenne went for $22K :burnout:

The 928 Photo Thread

Task completed - nice new light bulbs in the instr[…]

This is not a surprise. At all. I heard a whi[…]

http://msreg.com/Redezvouz928-SDC2023 Prelimin[…]