Tarmac Rallying Perpetual Thread

[sav man]

I return my fuel to the main tank and havn't had any pressure problems

[Duncan]

what are your main and lift pumps? If you think about it, when you return fuel to the tank you have 2 pumps in serial...the lower flow one must determine the overall flow.

[navdan]

Duncan, thanks for clarifying that in the earlier post. I knew I must have been missing something and this is exactly the info I'm looking for BEFORE I hook everything up.

That said, our intank would be 255lts/hr and the main pump 300lts/hr, not a huge difference and theoretically so long as the intank is not being a lazy bitch it should supply enough to keep up with the main. Our pissy little 2.0 doesn't drink a great deal at any time so shouldn't have too much of a drama.

Oh, and here's our quickest run from Saturday, my third competitive rally stage and quick enough for third place until the engine said enough.

[sav man]

what are your main and lift pumps? If you think about it, when you return fuel to the tank you have 2 pumps in serial...the lower flow one must determine the overall flow.

GTR lift pump and 044 pressure pump

[DJRIFT]

A few points regarding fuel systems.

Fuel coolers are factory fitted to almost all late model turbo diesel cars due to the high fuel pressure/ friction heating. They are definatly a good option on a race car.

I have seen a few examples where people can notice a drop in power after driving for a while and then apon closer inspectin the surge tank is very hot to touch.

Duncan. Most fuel pumps are rated at a set pressure and voltage. If the lift pump is un regulated it should be able to flow more volume than if it was regulated so a lower volume pump should keep up to the pressure pump. That is the theory I have worked off. I only ever use standard skyline pumps to lift to a single 044. They seem to do the trick.

Once again if the lift pump is able to flow a similar volume to the pressure pump than returning the fuel rail to the tank rather than the swirl pot won't be such a big drama. This is why Ben and I did his tank that way. When the hot fuel is returned it goes into a big heat sink. ( fuel tank ) rather than the swirl pot. He's done 2 Targas with no fuel heating or surging issues. I'm not saying this is how it should be do just that we do it this way and have had no ill effects. If it was a single lift pump goin to 2 pressure pumps in high hp applications than the return has to go to the swirl pot but for 300kw or under rally cars doesn't seem to be a problem.

Re engines leaning out. The best method period is individual exhaust gas temp sensors. They are a bit of a pain and fairly expensive but they also make tuning easier. I've only ever had anything to do with the racepac version which is around 800$ for a 4 cylinder. If its tied into a racepac dash it will warn you of one cylinder is out of range compared to the others. Far better than fuel pressure unless that is set up with rpm parameters.

[poolheaters]

So the fuel system return and surge return tee back into the main tank? How big is the surge tank? This would definitely keep the fuel cooler, as long as the surge tank doesn't run dry..

[DJRIFT]

Mine and bens are similar size around the 1.5 - 2l mark. No point having a massive swirl pot for the fuel to slosh around in.

And yes plumbing wise that's how we have done it. I mean you are free to consult your own expert but we both run 300kw cars with Bosch pumps and oem lift pumps and they seem to work.

Also don't forget to wire the pumps in via a decent supply feed and relay. I also highly recommend wiring the supply via a re-setable circuit braker somewhere in arms reach of the driver. All circuit cars I do have these and as far as Tarmac rally cars if you happen to have an issue there isn't always a fuse handy.

Just going off my personal experience

[Darkside]

^^^ Some great info there.

Are you guys running E85? Am looking to run single lift to surge tank to dual 044 to feed the chook cooker. Plan was to do the standard plumb the return line into the surge tank to ensure it stays full, but preferenec would be to avoid fuel warming issues.

[sav man]

If your running twin pressure pumps you will suck the surge tank dry. You would be best to put a cooler in the return line to the surge tank.

Another good option that a lot of cars are taking up down here, is a low level light for the surge tank. It's good protection against a lift pump failure.

[navdan]

One thing that has kept me awake at night the last few nights has been flow rates of two different pumps.

My plan is to us a 255lph in tank pump (lift) to service the swirl pot and a 300lph external from pot to engine so my query is, do I run these off the same trigger wire from the ECU so they effectively run the same voltage at the same time or do I wire the lift to have a constant voltage and only trigger the external from the ECU?

I'm guessing the pumps will flow different rates at the same voltage which leaves the issue of the external draining the swirl at a greater rate than the lift can supply it.

So many variables to think of before setting this up!

[2pee]

I think taking worst case, not a safe option - and against the general requirements, assuming Cams sanction.

Post # 5405 pretty well explains why running the pressure pump against the reg and line restriction with a lesser capacity lift won't be an issue. At the 12hr a few years back, before they went all GT, did find a significant increase in fuel temp even dumping back into a 100 litre tank, fuel pump probably over-specced.

All the kool kid categories run cable (if not direct) drive fuel pumps nowadays!

[DJRIFT]

Dan you use the original fuel pump feed to trigger a relay for each pump. This way both pumps behave like they should. They will prime with the key and also turn off with the engine. Wiring them direct ( not switched via the ecu) is vey dangerous under crash situation.

[navdan]

Dan you use the original fuel pump feed to trigger a relay for each pump. This way both pumps behave like they should. They will prime with the key and also turn off with the engine. Wiring them direct ( not switched via the ecu) is vey dangerous under crash situation.

Thanks Damo, exactly what I was wondering

[blackrex]

Dan, Whilst the lift pump will only be supplying 255lp/h, and the main taking 300lp/h, there should not be an issue, as long as your engine doesn't need the full 300lp/h supply, as any left over from the injection system comes back to the surge tank and maintains it's level, essentially the main pump is resupplying the surge tank with 300lp/h minus the fuel taken by the engine.

Definitely do not wire the pumps directly!

[Duncan]

Stu was one of the few survivors of a plane crash in Burma yesterday... I don't know of anyone who has spoken to him directly but the news report says both he and his girlfriend Anna are OK.

http://www.abc.net.a...e-crash/4443714

Hopefully they are both well and going to be heading home safely soon.

[paulR32gtr]

Wow - great to hear they are both ok.

[sav man]

I thought Helen was Bensons mrs? anyway good to hear he's ok, not everyday you walk away from a plane crash

[Darkside]

Happy new year all. Hope everyone had a good break. So what do we have planned for 2013??

At my end I am hoping to have this chook cooker hiding to nothing built by mid year in time to shake it down and if all goes well be at THC. Long road though as the chassis work has just started.

What is everyone else planning to get up to?

[sav man]

I've entered the little RB20 in Targa Tas again this year. I should have the engine back in it within the next couple of weeks. Hopfully then I should be able to do some decent testing for the first time in 3 years.

I'm heading down to Wrest Point in a couple of weeks to crew for the car Damo is navigating in.

[DJRIFT]

Yea Ive got a ride in a gt3 rs for wrest point.

Then next to Ben if he wants me ;p