Deadhead Fuel Setup

[Andy_S]

Anybody run this setup? I'm building a fuel system currently and strongly considering a deadhead setup. For those that are unfamiliar, its basically where the fpr is located before the fuel rail. There is only one line feeding the rail. Here is some crudely made diagrams.

Traditional:


Deadhead:


Research indicated some potential pros and cons, although there is conflicting information out there.

Pros:
Fuel isn't heating up passing through the hot rail multiple times
Shorter distance for fuel to circulate
Less fittings and line required
Cleaner

Cons: (potential)
Rail needs to prime and displace air on start up
Vapor lock on hot start
Starve injectors further from feed
Requires 3 port FPR (most aftermarket are though)


Discuss

 

[Terry Posten]

I think your title says it all.

But seriously, why?

Your (pros) list says shorter fuel line. By how much, maybe a foot? And tells of less fittings. No it is not, there are the exact same amount. Not counting the fittings at the tank or filter, there are still 4. You also talk about heat, the fuel cycling back to the tank, mixing with the large resevoir really should not be an issue. In the "deadhead" setup you propose, the fuel that is pumped into the rail can't leave any other way than through the injectors, that to me would keep the fuel in the rail longer heating it up more than the extra fuel being pushed out and cooled by the lines and tank.

Your "cons" list says it all. Start-up issues and higher possibility of leaning out half your engine?

Unless your planning more than 500whp, leave it alone, upgrade the pump and install a good AFPR and call I good.

 

[Andy_S]

My cons list is potential, not concrete. That's kind of what I'm wondering. Also you say shorter by one foot, but whats stopping someone from mounting the fpr right near the sending unit.

Have you run this setup before and experienced negative effects?

 

[IncorpoRatedX]

you'd have to run a vac/boost line all the way back to the FPR....

 

[Andy_S]

Yes. Not much different than routing a boost gauge setup I would imagine.

 

[Terry Posten]

No its not. The further away you mount a vac/boost device the slower it responds. Same goes for the pressure in the fuel line. You do not want to starve the cylinders of fuel even for a second.

That is why they say to install the boost controller as close to the turbine as possible and make the vac/boost line to the waste gate as direct as possible.

And if you install the AFPR back at the tank, good luck purging your fuel system of air and keeping bubbles out.

But it is your car, you do what you want.

 

[jepherz]

Pretty much a "returnless" fuel system on any newer factory car. I believe some of them use a more advanced system, possibly with PWM on the pump.

However, what you're saying about the FPR in the rear of the car is correct. There shouldn't be any need to run a full return line. I'm not sure some of the potential cons can be eliminated using the typical parts you would find on any modified tuner car though. Unless you plan to use some electronics, and the ECU you're using is in tune with the ACTUAL pressure at every instant (so it could adjust the injector duty cycle) I'm not sure you can avoid some of the potential problems.

It is interesting though. Makes me think about a system more controlled by software (which I'm sure some of the newer ones are). Essentially with the correct adjustment in the ECU, there's not even any need to adjust fuel pressure. This would also equate to the ideal atomization pressure I'm assuming for better performance and max efficiency in a wider range.

 

[jepherz]

Actually, I take my last paragraph back. After thinking about it some more, the adjustment of the fuel pressure is to keep the pressure at the nozzle constant, so it's necessary for the most part.

Looks like most returnless systems today do use electronics. A fuel pump controller, a pressure sensor at the rail, and the ability to PWM the fuel pumps. So, unless you have a way to make up for these items, I'd say you're in for a world of hurt.

 

Return-less systems use either electronic or mechanical fuel pressure regulation. By this I mean that electronic ones use a fuel rail pressure sensor and PWM the pump, mechanical ones have a physical pressure limiter in the pump. Compensation for increased fuel demand based on engine operating conditions is handled by increasing PW for the injectors exclusively on the mechanical and in conjunction with PWM the pump on the electronic.

(The above is based on factory GM and Ford training. Other manufacturers may differ.)

 

[CutlassJim]

It's already been said but a lot of newer cars come setup like this but I notice a lot of high performance crowds, LS1 F-bodies come to mind, change it and go to a "regular" FPR at the end of the rail design. I think it would work great on a low hp daily but not in a high hp application where you run a little closer to the limit on a lot of factors.