Fuel System - Part 3 - Deep Breathing

Next up on my job list was installing the air intake and air filter.

I purchased the stainless steel air intake pipe from AK; another bit of engine bay bling! This includes a couple of spigots to connect to the crankcase breathers so that any oil-contaminated air from the engine is recirculated back into the air intake.  It also has a hole underneath into which the Intake Air Temperature (IAT) sensor is installed; this is one of the sensors monitored by the Canems ECU.

Shiny intake pipe!

I ordered a standard GM IAT sensor from Billy's Speedshop via eBay.  I needed to clean up the hole in the inlet pipe slightly with a hole drill to get the sensor to fit.  This will be held in place with some polyurethane sealant.

Intake Air Temperature Sensor...

...installed into air intake pipe.

For the air filter, I went with a K&N RD-1450 unit.  This was basically the largest diameter but shortest height unit I could find with a 4-inch inlet flange diameter to match up with the AK air intake pipe (the short height is important as there is not a lot of room to fit the filter in between the intake pipe and the radiator). As well as providing increased airflow, the K&N units are washable and will last pretty much forever.

K&N Air Filter with oiled cotton filter element

The air filter was a simple slip-fit over the end of the air intake pipe and was secured in place with the supplied jubilee clip.

To attach the air intake pipe to the throttle body on the engine required a 102mm ID silicon Straight Coupling Hose (from Merlin Motorsport) and a couple of suitably sized jubilee clips.  These were torqued up to 6Nm as per the Samco recommendations and then checked again after at least 30mins to allow for any relaxation of the silicon pipe.

Filter and intake pipe installed - I even made sure the logo was level...

For the connections to the crankcase breaker pipes on the rocker covers, I used some 200 Series -8 braided steel line from Merlin Motorsports and some neat -8 hose finishers (which incorporate a jubilee clip) from Torques UK.  

Offside breather hose completed

The nearside hose was a bit more of a faff as the outlet breather pipe on the rocker cover faces towards the rear of the car.  This needed the breather pipe to turn 180 degrees; unfortunately the bending radius of -8 braided hose is rather large so an alternative solution was needed.

I used a couple of -8 straight female fittings and a -8 180-degree adaptor from Torques UK to come up with a suitable arrangement.  Unfortunately I couldn't quite finish off the install as I managed to misplace the final -8 hose finisher somewhere; no doubt it will surface once I've ordered a replacement...

My solution to redirect the breather pipe through 180-degrees

Somewhere in the garage, there is a stray hose finisher...

Fuel System - Part 2 - Regulating the Service

With the engine in, I could start connecting up the fuel lines in the engine bay and routing them down to join up with the supply and return hardlines.

As I'm running fuel injection I needed a fuel pressure regulator to supply a constant 58psi to the injectors.  I bought an Aeromotive A1000 High Flow regulator with -6 inlet ports to match my supply line from Summit Racing.  This is a 3-port regulator and so is installed into the fuel supply line ahead of the fuel rail; there is then one port that supplies pressurised fuel to the fuel rail and the bottom port returns excess fuel back to the tank.

Aeromotive A1000 Fuel Regulator...shiny...

The regulator ports needed some -6AN to ORB-6 adaptors fitting to allow connections to the braided fuel lines to be made.  I removed the brass plug on the front and installed a fuel pressure gauge into the port using some PTFE tape to help with the sealing.

The regulator comes with a mount suitable for fixing to a flat bulkhead.  However, I decided to fit mine as close to the engine as possible and mount it onto the tubular chassis bracing.  This meant I needed to make up my own bracket.  I designed a bracket in CAD and printed out a "flat sheet metal" template which I stuck to some 2mm sheet steel and used to cut, drill and bend bracket into shape.

Paper template used to cut blank from 2mm steel sheet

Using a 25mm diameter aluminium bar as a former for the curved section

The final 90-degree bend formed

2No. M5 Rivnets fixed into bracing tube...

...and mount fixed in place with 2No. M5 button head screws

I could then make up the fuel line between the regulator and the fuel rail; this was a short hose with a 90-degree -6AN fitting at the regulator end and a straight -6AN fitting to connect to the fuel rail connector.  The fuel rail connector I bought was a 90-degree item, with the usual 3/8" GM push-fit connector to the fuel rail and a -6AN female fitting on the other end.

-6AN Fuel Rail connector purchased from Torques UK...

...is a simple push-fit onto the fuel rail

Completed fuel line from the regulator to the fuel rail

I made up two oversize lengths of braided line; one with a 45-degree -6AN fitting for the line which will come up from the supply hardline and one with a 90-degree fitting from the bottom of the regulator which will then run across the engine bay and down to the return hardline.  I will finalise these connections once I know exactly how I am going to route the braided lines down to the hardline fixed to the chassis rails.

Fuel regulator and lines - sorted!

Fuel System - Part 1 - Hard Lines

The common approach when it comes to running the fuel lines for the AK builds is to use -6 or -8AN stainless steel braided hose from the tank, along the inner chassis rail to the engine and, in the case of fuel injected engines, similarly run a return line down the opposite chassis rail and back to the tank.  The fuel pump and filter are typically fitted on the supply pipe run and also fixed onto the inner chassis rail.

Although the AK fuel tank for a fuel injection set-up has a small sump to prevent fuel starvation under hard driving, a conversation with an AK owner at Stoneleigh a couple of years ago about his experience of fuel starvation, convinced me that I was going to go belt and braces on this and install a surge tank in my fuel system.

A surge tank is a small volume tank fed by a low-pressure fuel pump from the fuel tank; any excess fuel is fed back into the fuel tank.  The engine is then fed via a high-pressure pump from the surge tank.  This means that even if the fuel pick-up in the tank is uncovered, there is sufficient fuel reserve in the surge tank to provide an uninterrupted fuel supply to the engine.  An added advantage is that since the fuel between the surge tank and the fuel tank is constantly being recirculated this keeps the fuel supply to the engine cooler which is a big advantage, especially with the increasing ethanol content in fuels.

The surge tank will need to be installed in the boot of the Cobra and it made sense to me to also install the fuel pumps and filters in the boot rather than fixing them under the car.  Since I would need to run the fuel pipes from the fuel tank up into the boot and then back out again I decided to use run hardlines for the fuel supply and return lines along the chassis rails.  

I went with Goodridge HL836 lightweight aluminium hardline which I purchased from Merlin Motorsports.  This is made from Hycot aluminium; a precision-drawn aluminium tube with a black polyamide coating.

-6 Size Aluminium Hardline

Hardline Fittings 

I used my plywood brakeline template/ guide to help bend the tube to the correct profile.  The hardline diameter is 10mm which worked fine in a mini pipebender.  I made the pipes slightly longer than I thought I would need; these will be trimmed back when I know exactly where I will want to create the transitions to the braided fuel lines.

Hardlines bent to shape

These were then fixed into place on the chassis rails using some of my bespoke mounting blocks; the fixings on the offside chassis rail also being used to hold the rear brake pipe in place.

Supply and return lines fixed in place

Supply line will connect to a braided line at this point 

At the rear, two braided lines will run up into the boot

Everything seemed to fit into place quite nicely and I was very pleased with the final result.

You may spot from the pictures that this blog post is a little outdated given that the engine and gearbox are now in place but for some reason, I just never got around to writing up this instalment.  In hindsight, I was bloody lucky that the locations I chose for the brake/fuel line mounts didn't clash with the transmission as there was no prior consideration of this in my planning!! (Although I did crush the nearside fuel line when installing the gearbox which required the purchase of some additional hardline and a re-bending exercise - luckily I had kept the piece of plywood with all the bend guidelines on!)