Boiling Fuel Solution New Mk2 Improved Version

[Martin]

I've previously had overheating fuel problems on my 75s. I had the local trades guild cast a cooler out of aluminium but it only worked at speed, not where I needed it in traffic.  I have a laser temperature gun and started recording temperatures at the top of the tank the bottom of the tank and the fuel rail. Fuel rail temperatures were roughly twice the tank temperature. So I concluded the problem was in the fuel rail, one of the engineers at the guild came up with a plan to cast a new fuel rail with a built in cooler. I was going to go down that path until I came up with another far simpler plan.

Pre cooler temp.  Ambient     Top of tank    Bottom of tank     Fuel rail

                          27C            39C              44C                     79C

                          28C            40C              45C                     90C

                          29C            44C              47C                     86C

I recorded seven times but these were the highest readings on the fuel rail.

Cooler fitted.       Ambient      Top of tank   Bottom of tank      Fuel rail

                          24C             31C             31C                      26C

                          29C             30C             34C                      26C
           
                          26C             30C              33C                     26C
 
The above was recorded this morning at different times and has me stumped a bit as the rail is now cooler than the tank and the tank temperature has dropped by 10C. I will continue testing, but it looks like the new cooler is working and as the boiling point of fuel is 100C there is a very good margin. The prototype can be improved on and cost me $8.00 Au.

Regards Martin.

[blackie1]

"a plan to cast a new fuel rail with a built in cooler. I was going to go down that path until I came up with another far simpler plan. "

???
so what was the far simpler plan?

[Martin]

At the moment I'm just running the prototype. The whole set up is really simple piece of aluminium sheet with holes drilled to match the fuel rail and the mounting holes. I glued double sided reflective fire resistant foam onto the back of the aluminium. I then removed the fuel rail and injectors, and separated them. I placed the aluminium heat shield on the rail and clipped the injectors back on. A small amount of insulation has to be removed to allow the clips to be fitted. The whole assembly is then pushed back on with the aid of a bit of silicone grease around the "O" rings. A small bend has to be placed in the heat shield just above the injectors. No mounting screws are needed and everything is quite firm. The MK 2 version will have smaller mounting holes in the aluminium be shaped a bit more on the trailing edge and possibly be painted black. I'm still scratching my head on how effective it has been. The temperatures aren't high enough to test it fully that will have to wait, however I did give it a bit of stick and it still didn't make any difference.
Regards Martin.

Heat Shield Fuel Rail 1.png (45.53 kB . 768x576 - viewed 589 times)
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[The Mighty Gryphon]

Have you taken any readings of the cylinder head surface temperature under the rail?   I would suspect the bulk of the heat gain is from the radiator air flow on the return line plumbing, tank bottom and fuel pressure regulator.  The rail should be out in relatively unheated airflow and not the source of most of the heat gain, especially on a K75S.

I suspect there is something amiss in your data set for rail temperature.

[Martin]

Gryph I did eight readings before fitting the shield, and four after all similar. I just posted the ones that were the same ambient temperatures. Just as a precaution I'll fit a new battery to the gun. I'm going to the guild this morning and will get a couple of engineers opinions on what's going on. And I'll take cylinder head temperatures, can you supply temperature reading for your rail and tank and head. I'm trying to get readings from bikes fitted with a fuel cooler.
Regards Martin.

[The Mighty Gryphon]

I can get some readings, but it might take a few days.  The bike with the cooler is in the back of the garage and I've pretty much been doing all my riding on the K75S.

[MEZ]

Just stumbled across this thread looking for another topic. Interesting indeed as I fitted a Mocal 7-row cooler beneath the radiator as a matter of fact for the intended hotter visited countries on my hit list. I think after seeing the temp figures shown on here i'll be doing some thermal wrapping on some of the lines also. Might have to be getting me a temp gun too, good posting gents....

[Martin]

I am hoping to get more readings as temperatures rise in QLD. Apparently they have had a bit of a heat wave. But I'm currently tin topping and freezing occasionally for the last couple of weeks in Tassie. Since fitting the shield I have talked to a heat engineer. And he stated it is far better to stop an object from heating up in the first place than to try and cool it up after it has heated up. With that theory in hand I have tried to insulate the fuel pressure regulator with insulated reflective tape and have covered most of the fuel lines with foam sleeving. I will do the one line that I haven't done on my return. I will then do the ultimate test and try running a test on a 35C day and stop go city traffic. This is what caused the previous problem of vaporising.
Regards Martin.



   

[Martin]

Just an update on the heat shield, there is now no sign of fuel vaporising in the rail. I have done a few hot day runs in 35C+ temperatures in traffic with no problems highest temperature recorded in the rail 50C. I have managed to do a couple of comparisons with another K75s his rail was running at 75C mine was 40C. Another comparison with a K100RS was his 70C mine was 40C. I have since added foam insulation intended for 1/2 copper water pipe onto my FPR fuel lines. The lines on my FPR have been upgraded from the local unbranded Supercheap EFI hose which kept on collapsing on hot days. I'm now running Stealth submersible line on the FPR, and as required I will eventually change all my lines to this.
Regards Martin.

[Martin]

I've running the Mk1 version for 2 years and never had a return of stalling in traffic on hot days problem. The Mk1 version did all that I had hoped for and then some, as well as stopping the stalling in traffic on hot days it also greatly reduced the tank temperature. However there were access problems for tuning, so hence the MK2 version. The Mk1 version was made out of .6mm aluminium the Mk2 version was 1.5mm. The Mk2 version was made in two pieces to allow access for tuning and was a lot tighter fit around the rail injector cups.

I'm hoping that the thicker aluminium and tighter fit of the shield and the insulation will hopefully reduce the rail temperature even a little more. The two part design will allow for more easy changes in height, thickness and allow a paint to unpainted version of the top part of the shield to be compared. Comparisons between my bikes tank and rail temperatures to mates bikes have shown a large reduction. In a week a few of us are undertaking a four day ride and I'll try and take comparative readings. Initial readings at this stage are looking comparable between the MK1 and Mk2 but I wont really know until we hit summer.
Regards Martin.

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