Thread: Nascar efi

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It's true that NASCAR will have EFI for the 2012 season Cup Races, keeping carbs for Nationwide and Trucks. In their usual approach the decision makers studied all of the systems out there and decided on a package from McClaren Electronic Systems out of the UK which is said to have a price tag of about $25K per car. The justification for the cost is that McClaren made a "tamperproof" system that is sealed, requiring a NASCAR Code for the electronics to function. While it would seem to be an easy thing to have an EPROM port for a chip that limits the base fuel calibration pulse width, it sounds like NASCAR is going to retain restrictor plates, placing the orifice between the intake and throttle body just like with carbs. Probably OK, but seems to be a bit antiquated with the switch to electronics.

My question would be...Today when they crash the engine stops and the fuel pump stops. They will now be using electric fuel pumps what will shut them down? The driver??? Air bag type sencers??? neither of which I'd trust in a crash. Thought I'm probably all wrong

Far as I know Charlie,it doesn't now.

Charlie,
Today they use foam filled fuel cells with electric pumps, might be Waterman but not sure? They have check valves that close if the engine separates from the chassis - not sure what they use to cut power to the pump, other than a driver toggle switch to light off.
Here's Waterman link that explains their pump system, including a bit on efi systems - http://www.watermanracing.com/Pages/fuelpump25.html

From what I understand they use a cable (similar to a speedometer cable) that drives off of the rearend. This because I have heard a number of times when they say the fuel pump cable broke. Don't know how they keep the car running when it is setting still though.

Originally Posted by Bug

From what I understand they use a cable (similar to a speedometer cable) that drives off of the rearend. This because I have heard a number of times when they say the fuel pump cable broke. Don't know how they keep the car running when it is setting still though.

Yeah, I've read about the cable drives, too, and Waterman's kits for converting cable drives to electric. I got the impression that there might be a mix? I'll ask a buddy that's heavy into NASCAR from the supplier side.

Actually presently the fuel pump is mounted in the fuel filler plate and driven by a long cable off of the back of the oil pump (i.e.dry sump) some off the back of the camshaft,and some off the bell housing/flywheel, not off the differential. I would think Nascar would mandate a mechanical pump although reading that Waterman link about the electrical fuel pump it says they have several safety systems built in,but it didn't really give any details. Either way I don't think Nascar takes any thing safety, lightly. Waterman also makes some of the cable driven pumps currently used.

I know WAY back when we ran an electric fuel pump we had to use an override switch ( button ) till we had oil presure to make a switch to work a relay then it ran on its own if you lost O/P the fuel pump was shut off.

How about an inertia switch that would shut down the pump.

Originally Posted by cffisher

I know WAY back when we ran an electric fuel pump we had to use an override switch ( button ) till we had oil presure to make a switch to work a relay then it ran on its own if you lost O/P the fuel pump was shut off.

Geez, didn't even know they had electricity that long ago, Charlie!!!!! My first ever modified had a hand pump bolted to a tab on the cage that pressurized the tank with air and kept the mechanical pump well supplied..... (Wow, that was a long time ago, huh???)

A guy that I knew years back bought a car (MGB I think) that had quit running and the people could not figure out why. Supposedly they had a shop work on it for a couple of days and they could not figure it out either. Anyway, he bought it and it was 2 1/2 quarts low on oil. As he was trying to figure out what was wrong he went ahead and popped in a couple quarts of oil just because it was low and it fired right up. That was the first time I had ever heard of a fuel pump cutoff switch tied into the oil pressure.

My buddy got back to me with some details - in the carbureted configuration everyone used to run a normal diaphragm style pump mounted in the usual spot and driven by the eccentric on the camshaft. They moved to Waterman pumps in the back of the car a few years ago driven by cable, and the cable drive was generally built into the bell housing and driven off the back of the camshaft (like Hworrell said). The engine fired on start using fuel in the carb bowls - not so easy with injection as you would have to spin the engine for a while to build pressure. The McClaren ECU is based on their design from the IRL where they spin engines at about 2500 rpm with a 5 horse remote starter, which is not the NASCAR way where the car has to start on it's own. This caused a lot of discussion with the tech guys at NASCAR about how the fuel supply would change.

They initially were pushing for cable drive only, but testing earlier this year showed starvation problems down the straights so they moved to electric drive main pumps. Current fuel system guidelines require a "reservoir tank" not more than 100 ci internal to the fuel cell, and the main (pressure) fuel pump is either mounted internal to that tank or takes suction from the bottom of that small tank, which is limited to 10psi internal pressure. Most everyone uses a cable driven pump to scavenge the cell and move the fuel to the make up tank inside the cell. The electric pressure pump is located in the make up tank but can be external. Pump controls are stand alone, not in the ECU. The big thing is this could all change ten more times before Daytona