Regulators, Fuel Plumbing, and Forced Induction - Jody?
 

In my car I have a 434 SBC / twin turbo setup and am mapping out my fuel plumbing. I want to locate the bypass regulator back at the tank, to avoid circulating and heating of fuel by sending (most of) it up to the hot engine compartment / fuel rails and then returning it back to the tank (as has been discussed here extensively, in the past).

My question is, should I run a second regulator (see attached) after the fuel rails (which would be a boost referenced regulator) and then return any fuel bypassed from that second regulator, to the tank, also? The amount of fuel returned from the engine bay in this scenario would be relatively small.

OR, should I just simply bypass back at the tank, and "deadhead" the rails, with NO return to tank from the engine bay at all, and forget about using a boost-referenced regulator after the rails?

Why wouldn't you just boost reference the one regulator? There shouldn't be a need to return fuel other than from the first regulator… because all else is going to be rail pressure which is what you're after..

But I've never done a twin turbo motor - so hopeful someone that has steps in.

Rob ---


Here's Aeromotive power planner for EFI - Forced induction with various HP levels



http://aeromotiveinc.com/wp-content/...werPlanner.pdf

I was thinking that it would not be possible / practical to accurately boost reference the regulator back by the tank?

Thanks GW the Aeromotive guides are sending all the fuel up to the rails....no bypass back at the tank....

It's a closed loop system so I don't know why that would make a difference -- vacuum is vacuum as long as you don't have leaks -- and then a drop in that vacuum is a drop… so I don't see any issue with the small distance.

A guy could run a SS hard line back to the regulator if he wanted to and then just use a short piece of tube between it and the "source" or a piece of -3 SS braided for the flex section.

The regulator doesn't care about anything except that the "excess" goes somewhere…. and it doesn't care about anything except that it's "set" to allow "X" pressure on the pressure side…anything in excess of that goes out the bypass side (back to the tank)... It's a dumb piece of equipment. LOL


You can make that a long trip or you can keep it short and sweet. Most prefer to keep it short and sweet - and as you've pointed out - keep the fuel away from the heat source.


Personally -- I see more mistakes on the tank plumbing than anything else - with guys returning the fuel and aerating the tank --- or not having a sump for the pick up point. Or running too small supply side plumbing.

Sorry -- just went back to the page with the link -- and for the life of me - all I want to do is come down there and :buttkick: :bitchslap:

Go back and look at the system --- they're just showing you parts -- and there is a return to the tank from the regulator in every section.

Have you been checked for cataracts? :lol:

GW, I know how regulators work - this ain't my first rodeo...my point was, that in every example case that they show, Aeromotive is not bypassing and returning back by the tank - They are doing so w/the regulator located after the fuel rails, up in the engine compartment, which would be returning (heated) fuel back to the tank which we know can cause problems etc.

My main question is really if I can avoid having to run any return, after the rails (ie, just regulate/bypass and return back by the tank, and "deadhead" the rails) and just forego the idea of boost-referencing the regulated fuel pressure. It would certainly simplify things. (diagram below)

I have not been able to get a clear idea on whether or not boost referencing would actually matter, in my case. My max boost will be 12PSI with 96lb/hr injectors. It seems that boost referencing matters more on engines running tons of boost, but, this is only anecdotal observation, on my part.

The fuel pump I have is one of the new Holley (two bosch-type pumps in one case) and the plan is to have the BS3 ECM turn on the second pump based on RPM. The primary pump will have the Aeromotive PWM speed controller on it so that it is not running at max output when I'm just cruising around, etc.

Cataracts? no, but I am basically blind in one eye, so, there ya go :)

I inquired w/Aeromotive Tech Support re the same issue w/A1000 (although I'm not running boost) and I was told that their documentation says it needs to be at the fuel rail but at the tank will work as well, they just don't advertise that fact. They also said in my case I did not need to connect the vac reference. In my mind, if there was some specific/ironclad reason not to return at the tank it would be stated in bold red letters. Not sure if that helps - I will be bypassing at the tank and I'm sure if its a problem it will manifest itself relatively quickly. -Bob

When answering a question -- I respond to EVERYONE that may be reading not just the question. It's just my style.

Understanding how something works - helps more than just saying "do this - don't do that".

No worries GW

A boost referenced regulator after the rails along with one at the rear of the tank would serve no purpose.

First off, say your base fuel pressure at the rear regulator was 43psi but it's not boost referenced.

Even if your regulator after the rails is boost referenced it could never achieve anything higher than the base fuel pressure of the first regulator as the first regulator bypasses everything above 43psi.

Now you could boost reference a rear mount regulator but it cannot compensate for any pressure drop across the lines. (so you need much larger lines and fittings than you would normally use for close to zero pressure drop in order to see a true 1-1 reference at the rails).

If you are worried about the rails heating up the fuel you could "T" the regulator off the feed line just before the rails.

Really though, I see no problem with just running it in the conventional manner with the regulator right after the rails or on the rails. Millions of oem vehicles made this way and I've built countless 1000+hp turbo cars like this with zero issues.

If your fuel is overheating with this configuration you likely will not fix it by regulator placement. It will still come down to too much re-circulation which you can fix by running a speed controller (as I see you have planned) on a single pump or not running multiple pumps at the same time continuously. (turn on second pump in a dual or triple pump system with a hobbs switch).

This is the "voice of experience" that I was looking for. I agree/suspect that the amount of recirculation allowed to occur in the system, is the major factor in whether or not excessive heating of fuel occurs. Thanks!

Jody did have a killer setup on the his Malibu. He compared his setup to something similar to a corvette. I believe the fuel pressure regulator was located near the fuel tank, too. I'll to a search to see if I can find the post.

Ok... here is my real world experience with this on supercharged FE's running A1000 pumps and their large body carb regulator, and on EFI small blocks running A1000 pumps and their large body EFI regulator.

With the the fuel pressure regulator at the rear of the vehicle you will develop a pulsing in the fuel pressure that will affect drivability. Think of throwing a pebble in a pond, the ripples get bigger as they travel. Unique Performance was very fond of putting their fuel pressure regulators in the rear of the vehicles and on the EFI vehicles you can watch the rail mounted gauge jump 20-30 psi while idling... try fighting that while tuning. On the carbureted blown FE's with the regulator mounted in the back we were fighting lean tip ins on hard accel.... we were getting just enough of a delay with the vacuum signal running from the engine to the rear of the vehicle and the boosted fuel pressure going from the rear of the vehicle up to the carb that we were seeing a delay in fuel pressure. Regulator moved up to the engine bay... problem solved. When I replumb the fuel systems on these vehicles I thermo-sleeve all of the lines because they do run up the tranny tunnel where they get alot of exhaust heat. On

I do recommend the use of their duty cycle controller to slow down the A1000 fuel pump operation for regular driving.

I always plumb my rails so that the regulator is after the engine.. In my head I would rather have full fuel flow available to the injectors rather than "regulated" fuel (I know it's all regulated ) to lessen any changes of starvation. I also plumb them parallel instead of series where the last injector would have a higher chance of starving.
http://i696.photobucket.com/albums/v...psd7f99045.jpg

I've never had the fuel pressure vary even one psi at idle with a rear-mounted regulator. 20-25 psi is insane, and I would think there's something else going on. That's with my fuel pressure gauges coming directly off the rails.

If it were one car I would say, sure there could be something else factoring in but it is every single vehicle they plumbed that way. I'll look back and see if I've got video of an earlier car showing the fuel press gauge jumping... I haven't bothered documenting it for a while since it's every one of these cars. Regulator in the rear of the vehicle dumping right back to the tank.

Pic of the current vehicle I'm replumbing before....
http://i696.photobucket.com/albums/v...ps065d6baa.jpg

And after... pre filter moved into the tank... Post filter after the pump.
http://i696.photobucket.com/albums/v...psb88efc74.jpg

New fuel lines run rear to front. Yes.. I know the undercarriage on this one is rough... it's had a lot of hands on it before it got here.
http://i696.photobucket.com/albums/v...ps45438c53.jpg

Regulator relocated to the engine bay.
http://i696.photobucket.com/albums/v...psac04a877.jpg

The 70 Chevelle listed in the sig below as a feature vehicle was plumbed with a Ricks tank with the intank A1000 drop in unit with the built in pre-filter. It was powered through an Aeromotive Duty cycle controlller. Post filter right outside the tank. Regulator hidden up on the firewall behind the engine It put down 820rwhp with boost. -8 supply and return line.

http://i696.photobucket.com/albums/v...ps813ab9cf.jpg
http://i696.photobucket.com/albums/v...psac81e980.jpg
http://i696.photobucket.com/albums/v...ps482ea124.jpg

I'm not arguing with you, I'm sure if that's what you saw, that's what you saw. But I worked at a shop where dozens of vehicles were plumbed that way, from 400 rwhp to 800+ rwhp, and none had anything but dead steady pressure always (other than boost referenced deals under boost, which of course increased).

No worries... I don't take anything negatively... I've been around long enough to know that in every situation there are always variables that may not be accounted for. It could be that particular mix of hardware that UP was using that had issues when put together (wouldn't be the first time), and perhaps the shop you were at had spec'd out a particular mix of hardware that worked well together and didn't have those same issues.

I just want to share what I've experienced in case anyone else runs into the same issues so they won't spend days beating their head into a wall trying to figure it out. Personally I wouldn't put the regulator at the back with the hardware I'm using... what I do works for me so I stick with it.