Fuel Injection - Pump and Surge Tank

Below is a link on Youtube that really explains quite well how Fuel Injection works. Its a shame the engine being used as an example is so filthy but you still get a very good idea on just how EFI (Electronic Fuel Injection) works. The guy himself is a real hard case. You can even hear him having a good old scratch part way through the video..... no I don't wanna know what he was scratching...... and if you can make it through the 9 minutes or so to the very end, you will be treated to an awesome laugh. Kinda funny and scary at the same time but a good explanation all the same.

http://www.youtube.com/watch?v=i00j6lJgRLs

This next link shows how a carburetor works. Its for an aircraft but works the same on a car. Sorry about the singing intro but it is a very good explanation.

http://www.youtube.com/watch?v=9BYm0HnLGRU

Now because I am using the Lexus V8 which is of course fuel injected, I am going to need something a little more elaborate when it comes to the fuel tank and the fuel pump. This is because if I had a carburetored engine, a carb doesn't need a lot of fuel pressure, just enough to get fuel from the tank to the carburetor which has its own little reserve tanks of fuel up at the engine (the float chamber). The engine then basically sucks the fuel in that it needs. Another point to note is that if your fuel tank is nearing empty and you go round a sharp corner and the pump sucks a big gulp of air, it doesn't matter as the carb still has its own small supply of fuel it can use while it waits for the pump to send more fuel along.

With an EFI engine though the fuel is sent straight to the injectors and they need a constant supply of high pressure fuel. This means you need a high pressure pump and it also means you can't ever have the pump sucking air. If it did you would get a big gulp of air at the injectors and no petrol would go into the engine so the engine would cut out. To avoid this in EFI cars they have a surge tank which ensures the fuel pump always has a supply of fuel around its intake tube, even when you are going round corners.

So for me with my build it means I can still use an old style 1934 Ford tank but I will need to put a hi pressure pump into it and I'll have to install a surge tank for it to sit in.

To achieve this I have today been in and bought a fuel tank from a turbo charged Toyota Celica GT4. The pump in this tank will deliver enough fuel volume to the engine. Also the tank will have a surge tank in the bottom of it. I'll just need to cut these components out and install them into a tank that suits the 34 Chassis both in terms of install and perhaps not quite so ugly as this one.

Anyway, here's the tank I purchased today.




There are three circular plates on top of the tank. The top one is the breather pipe that allows the tank to breath as the pressure changes inside the tank depending on the temperature. Obviously on a hot day the fuel and air in the tank expands and that needs to go somewhere, hence a breather.

The second plate to the right is the fuel level sender unit. This is basically a float on an arm that operates an electronic rheostat that varies the signal (amount of current) being sent to the fuel gauge you read on your dashboard. As the arm goes up, more current goes to your gauge and the needle goes up to full. As the tank drains the float drops down and more resistance is applied in the rheostat so less current is sent to your fuel gauge and the needle on the gauge drops closer to empty. We'll look at the float inside the tank in a picture below.

Lastly the big plate has the pump under it and the pipe that carries the fuel from the pump to the engine is coming out of it on the right. The other pipe to the left is the return pipe, this returns fuel that was unused by the injectors. This allows the fuel circuit to run a constant pressure regardless of how much the injectors are or aren't using. Any surplus fuel comes back to the tank to be picked up by the pump once again.

Lets have a look inside.



This is the pump (laying on its side). The pump itself is the cylinder to the left in the photo. It sucks fuel through the nylon "sock" that is at the top left of the picture (the squarish white thing). You can see the fuel pipe coming out of the pump and going up through the mounting plate we looked at from the outside in the last picture.

Also you can see the return pipe coming back into the tank. It has an open end with a "hockey stick" bend at the end.


Last but not least here is a view inside the tank looking into the surge tank. That's the white plastic bin. In effect this is always full of fuel and ensures the pump doesn't suck air even when going round corners or braking heavily, so the injectors have a constant supply of fuel.

Also to the right of the surge tank in this pic you can just make out a black cylinder lying on its side in the fuel. This is the float for the fuel level sender and it moves up and down and in turn raises and lowers the arm attached to it. This then operates the rheostat I mentioned earlier to vary the current that goes to the fuel gauge. The rheostat is inside the cream coloured plastic box to the top right of the photo.

So there you have it the reason I needed an EFI tank and pump and the basics of fuel injection explained.

I think I'll go and have a cup of tea and a lie down now.

Body - Choice between Steel or Fibreglass

I had to go to Nelson for work this week so I took the chance while I was staying over night to go and see Steve at a place known as Rusty Acres on Tuesday evening. Its just 5 minutes out of town at a settlement called Hope and is quite well known to those in Hot Rod circles. Steve has collected up all these cars and a lot of oil company memorabilia. I guess it is all quite valuable stuff but only if you want it and only once restored. You can't help wondering how many if any of the cars will ever see the road again.

Well worth the look anyway and I was keen to see the Tudor he has been advertising on Trademe for a while.



You can see the tudor I have come to see at the front right of this next picture.


He definitely had some cool stuff there, including this old original stockcar. All of it is going to have to be sold apparently as he and his wife have separated and the property is being sold.



Anyway this is what I went to see, its an original 1930's steel Tudor body. Quite cool when you see an old car like this. The guys that built this will most likely be long dead yet the car lives on.... well sort of lives on. It was every bit as bad as I thought it would be. Not exactly what you'd call a good find. Its about as rough as they get before you bulldoze them into the ground.













As you can see its a bit rough round the edges..... actually its a bit rough in between as well..... no its probably worse that that.... it's fair to say it's farked! In this case I'm gonna have to say no I'm sorry.

I am still not going to right off the idea of steel but fibreglass is still really at the top of the list. There are several reasons why I'm not too keen on steel, namely, you need space to bring something like this back from the dead as it will require a lot of panel beating, welding and grinding. This brings me to the next major stumbling block. I am not a skilled panel beater or welder, so you have to pay someone. A body like this would cost about $30k to restore. On top of that, even when its finished its a steel car and I'd have to question.... do you ever really get rid of the rust? I suspect not.

On the other hand with fibreglass, you order it, they ship it, you bolt it on and you drive it. Okay not quite that simple but damn near.

Never say never though as steel is far more desirable from a resale value point of view and if a decent body turned up, perhaps it would be foolish to say no.

Aircon - More Wiring

The wiring saga continues. The upside is I am learning heaps....but its fair to say I am coming across a few obstacles. One such obstacle was the Fuse and Relay board that has a few plugs going into it. Unfortunately it is not clear from an external inspection as to where the wires go or what relationship they have to the various fuses and relays. So there is only one thing for it. Take a look inside one.....



This is a spare fuse board and relay panel that I got from an identical car (Thanks Garry once again). You can see here I have pruned all the wires back so I can see what I am doing. I will now pull it apart to see what goes on inside.



You can see here what the internals are like. Holy shit!

Nah its not that bad. In essence each of the silver strips you see weaving around on these boards is like a wire. It carries current from one area to another and is separated from all the other silver strips. Kind of a network of circuits taking current from fuses to relays and plugs. The three centre boards you see here are double sided and yes they do all come from inside that one panel! On some of these boards you might see a tab sticking up (remember you can double click on the pictures to make them bigger). These tabs go through one or more of the other boards to connect with components on different levels.

It takes a bit of tracing but it is quite logical if you take your time.


You can see here I have marked one of the circuits in red. Its kinda like those kids games where you have to find your way out of a maze. The difference being this one is three dimensional with multiple layers.


It is quite rewarding to be able to extract more and more circuits that won't be needed and now that I can see where things are going I can determine if they are important to what I am doing or not. Piece of cake really.

WHAT IS A RELAY
It just occurred to me that there might be a few reading this Blog that don't know what a relay does. In essence it is a small box that acts kind of like a switch. You see many of the switches in your car like wipers, headlights, horn, heater etc just aren't designed to carry the amount of power needed to make these components work. They would just burn out. So to get around this, the switch you turn on for these components doesn't actually carry much current at all. It is just enough to activate an electromagnet inside the relay which simply pulls a bridge across in the main power feed to the Headlights for example. That way all your headlight switch has done is provide enough current to activate the electromagnet, which then bridges the circuit for your headlights so that they can draw the power they need straight from the battery.

Take a look at this video on Youtube. It explains it really well.

http://www.youtube.com/watch?v=wz4X5umfNkQ&feature=related

ENGINE WIRING
Phil sent me a pic during the week to show me where he is up to with the engine wiring. It is looking great I have to say. He does a very neat job, using trailer flex (as this has 7 or so wires all wrapped together). Phil is running the wires with good length on them and mounting all the components on a temporary board to keep it all together until I fit it permanently in the car. Unfortunately I left the picture at work so I can't post it here today, but I will send it home and get it on the blog soon so you can see what it all looks like.