FPR location

[bsimon]

I posted this on BC as well...

 

A virtual spaghetti factory of hoses and wires has been created under my bonnet with a few years of upgrades. Now the addition of a dry sump system exacerbates the situation. I want to clean up the engine bay.

 

With the engine out of the chassis, I've already neatened up the wiring and breather lines. The fuel system is the next job.

 

Currently I'm running the pressure line to the front of the fuel rail and have the FPR and return line mounted on the rear. This was the classic method suggested when I first installed the fuel injection. Not very neat, but it works well.

 

What if I mounted the FPR (3 port type) on the chassis with the pressure and return lines attached, then run a single short hose to the fuel rail? The other end of the fuel rail would be capped off.

 

The fuel system would be all 3/8 (-6AN) hard lines through the chassis with a 10 inch run of -6AN Goodridge 910 hose from the FPR to the rail. My fuel pump is a 255lt/hr. rated unit out of a Camaro. I don't think there would be much in the way of pressure fluctuations with this setup. Any thoughts?

 

I see the current CC chassis are doing essentially this by mounting the FPR in the tank or rear axle area and running a single line through the chassis to the fuel rail. Cosworth recommends this setup with their 250 HP Duranail lumps as well.

[slomove]

Bob,

that is what I am running. The fuel flows through the regulator into the rear end of the fuel rail with front and capped.

 

No problems at all, work s fine. Why shouldn't it?

 

Gert

[slomove]

Actually you can see it quite well on this picture. The hose on the front actually goes to a fuel pressure sender, that means is practically capped:

http://home.earthlink.net/~slomove/sitebuildercontent/sitebuilderpictures/withfilterleft.jpg

[bsimon]

Hi Gert,

 

That's what i have in mind, only I was going to make the hose from the FPR to the fuel rail a bit longer.

 

I was talking to a chap that races (drag) a Mitsubishi AWD something or another . He mentioned that most of the racers don't dead end the fuel rail to keep the fuel cooler. There's less heat soak before the engine consumes the go juice. Also, air can get trapped and lean you out on startup.

 

Newer cars are all dead headed to keep the hot fuel in the rail until it's used up. Just the oposite of what the ideal high performance setup would be. It seems the heated fuel creates more vapor in the fuel tank and makes the evaporative emissions systems work overtime to keep those vapors in check.

 

I have a feeling that the issues the rice racer brings up are one of those 10/10ths improvements that keeps them from trailering early at a race.

 

I'm leaning towards retaining the loop system, mostly because I've figured out a simple way to access the front of the fuel rail without a long hose run. I have some mild concerns about heat soak from the elevated temps under the bonnet of a Seven.

 

I got pretty handy with the hard line bender and made a return tube that clamps right to the fuel rail. Now, all the hose connections will come of the aft end of the engine.

 

I'll post some piccys when the engine is back in the chassis.

[slomove]

Thanks for the explanation.

 

On the other hand, even running track days here in the desert at 100+ degrees I never had any heat related trouble. That means, maybe I had but the car did not.

 

From the point of physics it also smells like a motoring legend. At full speed (when the fuel temperature/density argument should count) the fuel is moving in the hose at a pretty good pace. For a 200 hp engine with 30pound injectors I estimate about 3"/sec even in the leg to the last injector. That would not leave much time for heat soaking.

 

But since the heat transfer from the aluminum rail to the fuel is anyway much more efficient than from the hot air to the rail, I suppose the consumed fuel will just cool the rail down to whatever temperature is has.

 

That all may be different, though when idling. But once again, no problem here.

 

Gert

[bsimon]

I've been looking at the engine bay again. I'm back to thinking the neatness of dead heading the fuel rail has more benefits than any other issues. Although the engine bay gets quite toasty, I've never heard of of heat soak in any injected Sevens.

 

This whole exercise in fuel system plumbing has cost me two 25 foot rolls of aluminum tubing. Not expensive, but frustrating. I keep seeing better routing AFTER bending the current route. At least all the fittings are reusable and the cutting, bending, and flaring is kind of fun.

 

Now my recycle bin looks like a spaghetti factory.