Using standard ra28 fuel line as tank return from 1G rail.

[thomasbl]

I am in the process of bending up new lines for the ra28. I decided to go to 8mm lines to suit the 1G. I was going to bend 2 new lines, a feed and a return to the surge tank up front. I was hoping to use one of the standard lines as a return to tank from fuel rail so im not putting hot fuel back into the surge tank.

Issue is that its an 8mm return from rail, i think its 6mm for the standard lines. Any thoughts on how to get around this easily?

[Norbie]

Should be able to pick up a brass adapter fitting for 8mm -> 6mm at any hose/hydraulics shop.

[thomasbl]

Ah, ok. Ill see if i can find an 8mm to 6mm inline barb style fitting. Thanks for the tip.

[Pube]

I got new barb fittings to fit my 1G fuel rail. I got a union to screw into the rail with an AN fitting on the other end. Then an AN barb fitting to screw onto the union. Best bet is to check speed shops rather than places like pirtek as I have found them to be totally useless!

[o_man_ra23]

Wow, Ive found Pirtek and Enzed to be the greatest when doing anything with hoses. Maybe its a QLD thing?? They also seem to be about 1/10th of the price for an identical part (same quality) compared with any auto store I have seen.

How is the return connected to the rail?? If its a banjo fitting, just get a banjo with a 6mm barb fitting, piece of cake then. Otherwise, you get an 8mm barb with male thread, and a 6mm barb with female thread (always have the flow go from male to female when possible), bit of PTFE tape, couple of hoses and clamps, and bob's ya aunty, $3 solution (parts easily available at Pirtek/Enzed etc)

Cheers, Owen

[Hash_ra23]

hey mate

you should check out a post Rod made in TA-022's members ride thread:

http://www.toymods.net/forums/showth...ine#post439591

[TA-022]

LOL i love my build getting slutted around

i used those pirtek compression fittings on the return lines.

for some reason they leaked out the thread tape on the feed lines so i p*ssed em off in favour of double flaring.

but on the return they havent leaked yet .. must be a pressure thing.

were about $2-3 each. oh and pay cash for less

[o_man_ra23]

So long as you pick your pumps right and the lift pump outflows the pressure pump, no problems.

I guess I wont be having this problem, as my surge tank will be inside the main tank, thereby cooling the returned fuel and there wont be a problem with my lift pump not outflowing the pressure pump.

So depending on how you pick your pumps as to how valid Rod's post is. You should always have the lift pump outflow the main pump anyway, because (surge tanks aside) if your lift pump doesnt outflow the main pump, then the main pump will cavitate and destroy itself very quickly. Look at the VL setup, the lift pump there outflows the pressure pump, there is no surge tank, the engine never starves (even turbo models), and the pressure pump never cavitates. It would be poor engineering to size the lift pump to suit the motor, and recirculate hot fuel so you can run however big a pressure pump you want. You are much better off sizing the pressure pump to suit the motor, and then size the lift pump to suit the pressure pump, which will then allow your surge tank to perform the job it was originally designed for... prevent fuel starvation when your on a long corner and the fuel in the main tank moves away from the lift point.

But hey, what would I know??

Cheers, Owen

[thomasbl]

Thanks guys, lots of good input. TA-022's thread build was a good read, regardless of how relevant it was, thanks for the link.

The fitting on the rail is a bit of a tricky one. At first glance, there seems to be pulsation dampner/ pressure reg units on each end, the fitting closest to the firewall has a fixed steel line which bends back under the manifold and has a banjo on the end. the front of engine fitting has a push on efi line, on an 8mm barb fitting. It appears that this return barb is also moulded into the pressure reg unit. It seems this may count out screwing in a different fitting to the rail.

As for pumps, im using a GSL-392 walbro high pressure and a pierburg lift pump.

[o_man_ra23]

What are your pump's flow rates at full pressure.

Cheers, Owen

[thomasbl]

This is the walbro high pressure pump. Ill hunt around and find the Pierburg specs.

Found em..

Its part no. 27-21443.

6.3-8.1psi.
100litres per hour @12v.

[TA-022]

rail mounts are banjos .... the regs screw off and the metal lines can the be removed.

you could then take that to pirtek and they'll remake the end you need or remake the whole line.

I can see merit in the warm fuel arguement .... and in the return to surge arguement.

I only went with return to surge as this is what I've come to see on alot of surge tank setups, plus the power loss from warm fuel wouldnt be that large i think (i have nothing to back this up though - its just uniformed opinion). Basically it's what I was used to so I set it up that way.

[o_man_ra23]

Hairy nuts... but its not a performance drop I am concerned about... warm fuel requires less pressure and spark to ignite, so pinging, detonation, knock and religeous pistons are the turndown for me for warm fuel. I would rather have a knock sensor that never gets used, than rely on it to retard the timing and hopefully save my engine. Warm fuel has the same effect as running fuel with a lower octane rating... more stored energy in it, but less stable.

Cheers, Owen

[thomasbl]

I too didn't think it would make a huge difference. I decided to do it properly the first time though. As i making new lines anyway, its not too much hassle to route the warm fuel back to the tank. Ill check those fittings TA-022. Thanks for the tip.

[JustenGT8]

Anyone ever measured the temp of their fuel? thought not, not an issue for 99.9% of us.

Anyone thought about what the fuel does when it leaves the injector? Apart from the amount that vapourises in the intake flow the rest is directed at the back of the valve (on most of our engines anyways).....why? to heat it up and get better vapourisation. The benefits of this effect far outweigh any issue from the tiny tiny tiny miniscule temp increase warmer fuel adds to the intake charge.