44 replies to this topic

[Nev]

What power are you making?   Have you ever checked the swirl pot temp?   Gaz

Yep, the fuel rail gets to about 60 degrees C (almost too hot to hold firmly) and the swirl pot maybe a bit less. The swirlpot is in direct line of incoming air from the LHS ear, which might marginally cool it.

 

Thankfully I've never had any fuelling pressure/flow issues at all, regardless of which map I use. Even flat out for 20 to 30 secs at 550 HP it has been fine. I run an unknown fuel rail pressure (after CS quietly crushed my FPR to compensate for a big mistake with the injector CC they insisted on using), but it's probably somewhere around 3.5 to 4.0 Bar.

 

Looking at dyno data I have, my current injectors just reach 79% duty at their peak. They are 875 CC/Min, so from that I calculate my max fuel consumption is 2.8 Litres/min (or 168 Litres/Hour!!).  This figure doesn't take into account my "unknown" increase of fuel rail pressure, which would in effect raise this consumption somewhat.

Edited by Nev, 31 July 2017 - 12:04 PM.

[Spitfire Engineering]

Too hot to touch!  

I think it's fair to say this setup has only worked (and then marginally as you are getting pretty close to vaporisation) without any issues is down to the huge amount of fuel you are using (i.e not returning/circulating) and luck.

 

So rail 4 bar plus 1.5 boost to get to 550+? about 5.5bar or 80psi

 

You would not expect to have any starvation issues while running over 24 amps worth of pumps supplying enough fuel for over 1300bhp if used individually, in combination it is more complicated and depends mainly if the swirl pot is vented to the tank or not. if it isn't then you probably have enough fuel for 1000bhp, if it is then it is just the 044 output that matters so about 840 bhp, high but not a problem if it was the only pump but in your case this leaves the Walbro to circulate fuel at tank pressure, probably in excess of 300lt/hr 

As the fuel from the walbro goes through the filter, onto the swirl pot and back to the tank the maximum capacity is probably 3L? maybe 4l with a big swirl pot, this means the fuel will circulate about 100 times an hour, each time collecting 14A worth of heating from the Walbro. I would normally say also from the engine but in your case the temp is now so high the heat transfer runs the other way!

Not too surprising you can hardly touch the rail/pipes.

 

At maximum power this circulation reduces by about half (you will use 160lt/hr) but still way too much and not a good idea.

Worth pointing out that the Walbro's are so inefficient that the Bosch 044 uses less power at 80psi (11a vs 13A) and shifts about 80% more fuel (840/475 lt/hr).

Assuming your swirl pot is ventilated you could easily have used an OE pump, still too powerful for this job but much, much better than the Walbro.

 

For other installations on here the same philosophy applies, you don't want a high power pump that you don't need, it has no advantages but many disadvantages.

 

 

[Nev]

Much of what you speculate is probably correct, but it's all been working without the slightest issue for some 7 years now. It's not an ideal setup, but it works and was easy to implement, was cheap(ish) and safe.

 

I put the Sytec (perhaps Walboro) pump in the OEM canister originally, as that was all I could find on the market at the time (remember I was pioneering 8 years ago). Further into the project (due to engine spec creep) I was concerned that it might not deliver enough fuel, so I installed the 044 pump in addition to ensure there wasn't a lean running issue. It's not perfect, but it doesn't need to be, it just need to be reliable and functional - which it is thankfully.

 

BTW, my fuel rail gets hotter than the swirl pot, I think the bulk of the re-circulated fuel in the tank is a fair bit lower temp than the both the fuel rail and the swirl pot.

 

I made my posting as I thought it might help someone in the future.

 

 

Edited by Nev, 03 August 2017 - 02:11 PM.

[Doctor Ed]

Im in a similar boat, and I'll be interested to see how the temps go. I've got an external 2L pot with an 044 in it feeding 5bar in a deadhead fashion to the rail through a -6 line and a corvette filter reg with -6 return to the pot. The oem intank pump I've left as is, and is now basically a low pressure lift pump to the external pot. The pot is hooked up with a -6 feed and a return back to the main tank so will probably run at only a little above atm pressure. The oem pump is going to be singing along! I might see if I can implement some fuel pump speed control, both of those running flat out all the time is a lot of overkill (although the surge resistance is a big bonus). Ps, pumps in my system only need to deliver ~460hp of fuel at 5bar. The 044 is just such a universal pump, there so many fittings etc available for it, plus it's a known quantity in terms of output and reliability (and noise). It's hard to overlook as a main pressure pump even if over spec'd most of the time.

[Spitfire Engineering]

Much of what you speculate is probably correct, but it's all been working without the slightest issue for some 7 years now. It's not an ideal setup, but it works and was easy to implement, was cheap(ish) and safe.

 

I put the Sytec (perhaps Walboro) pump in the OEM canister originally, as that was all I could find on the market at the time (remember I was pioneering 8 years ago). Further into the project (due to engine spec creep) I was concerned that it might not deliver enough fuel, so I installed the 044 pump in addition to ensure there wasn't a lean running issue. It's not perfect, but it doesn't need to be, it just need to be reliable and functional - which it is thankfully.

 

BTW, my fuel rail gets hotter than the swirl pot, I think the bulk of the re-circulated fuel in the tank is a fair bit lower temp than the both the fuel rail and the swirl pot.

 

I made my posting as I thought it might help someone in the future.

 

 

 

I realise the timeline involved did not have the options available now, it was good info and it is always worth a discussion as it tends to be specific which often covers more that just generalisations.

Choosing a Walbro today would probably be the worst option, it's the most inefficient pump we have ever tested and the 255 is too powerful for most on here who are around 280-340 at 5 bar including boost. The 044 would be ludicrous  

 

The probable reason the rail is even hotter is because the 044 is adding further heat between the swirl pot and the rail.