Fuel Rail Supply Line Conversion

Ever seen those trick works racecars out there with braided hose and AN fittings for everything? I'll publish an article later on the intricacies of AN (Army Navy) fittings and the various type of braided hoses in the market later but for now this article will concentrate on the convertion of your fuel supply line from petrol filter to fuel rail.

Pls note that I had a lot of help from Jeff Lucius's excellent web site article on such a conversion for the Mitsubishi GTO (US market Dodge Stealth and Mitsubishi 3000GT). Jeff's web site can be found at http://www.stealth316.com

Picture below on the stock fuel supply line and hose parts required for conversion

Before beginning this project you will need an adapter for the fuel rail end. There are an abundance of adapters in the US market meant for the 4G63's/6G72's fuel rail but :
1. I'm not sure if they'll 100% properly fit on our stock (4G93)fuel rail
2. Most of the US speed shops were not too interested in doing business with me nor the patience to properly respond to my email queries

and most of all
3. These same shops were charging an exhorbitant price for the adapter and shipping. Imagine paying RM350 for one adapter.

With this in mind I had my adapter custom manufactured. The adapter was milled from 6061 aluminium alloy and anodized black. As you know anything custom manufactured is not a one off so I had to order a set of 10 (smallest order quantity). Some of my brudder's have taken a few sets but I do still have a couple left (RM85 per adapter). If you're interested do contact me at my email - llsaw1@yahoo.com.

In addition you will also need the following:
Adapter for fuel filter. If you are using the stock 4G93 fuel filter (same as most other Mitsu models including 6A12, 4G92, 6G72, 4G63, etc.) the thread size and pattern for the filter end is M12 X 1.25. The Mitsu/Proton part number of the filter is MB658689. You can also custom manufacture an adapter yourself if you so wish but there is an excellent option avail cheaply from the market which is the Earl's replacement adapter (Part No: 991945. Straight M12 X 1.25 to -6 AN male). This adapter incorporates an o-ring for better sealing characteristics.

You will also need bout half metre of braided hose. Any hose from the market (Earl's Aeroquip, Goodridge, Icore, XRP, etc.) will do but make sure you use the end fittings meant for said hose from the same manufacture. Per my understanding they are not interchangeable. They might be but you don't wanna take any chances as far as petrol is concerned. I have decided to use with all kinds of fuel out there including methanol. Most people including the Jap speedshops would use synthetic rubber nitrile lined hose such as the Earl's Perform-O-Flex hose but I'm not convinced these hoses will fully withstand our Malaysia petrol in the long term. These hoses are not susceptible to the MTBE agent used on some fuels and have been known to sour and emit smell after a while. Please note that a -6 AN sized hose should be sufficient for our application for up to 350+ horsepower. Please also note that if you go to a -8 AN sized hose, you will require totally different end fittings and adapters.

And of course you will also need a -6 AN 90 degree end fitting (Part No: 6091-06)and also -6 AN 45 degree end fitting (Part No: 6046-06). Pix of hose, end fittings and fuel filter adapter below

You can order the hoses and end fittings from most speedshops in Malaysia such as Pentagon Enterprise, N1 Racing, etc. Alternatively they are also widely avail via mail order from the likes of Demon Tweeks and even eBay. Your preference.

I also ordered some alloy spanners from Earls and Goodridge. These alloy spanners are required if you do not want any unsightly scratches caused during assembly on the end fittings. Picture of the spanners and assembled hose below. Assembly instructions of the various types and makes of hoses are different

Picture of the Earl's adapter screwed on to output end of the fuel filter. Note teflon tape is not needed due to the excellent seal on the Earl's adapter's o-ring.

Picture of fuel line test fitted to adapter on fuel rail end

Picture of the complete assembly test fitted


Installation
1. Disconnect battery
2. Remove air filter and piping assembly for easier access to fuel filter.
3. Remove stock fuel supply line from fuel rail and fuel filter. Do note there will still be some pressure in the fuel rail so do use a rag to soak up the excess petrol coming out once you have removed the line.
4. Remove fuel filter (optional, if you are changing fuel filter. I took this opportunity since this saves on the labour and effort).
5. Install the fuel rail adapter on the fuel rail. Remove the o-ring from the stock fuel supply line and install it to the adapter. Applying some engine oil during this process helps. Carefully push the adapter into the fuel rail, line up the 2 bolt holes and tighten the bolts. Installed pix below

6. Install fuel filter (optional) and adapter
7. Install the new braided fuel line. Pls note that you DO NOT require teflon tape or sealant for AN fittings. I have seen people doing this and honestly it sucks from an engineering standpoint. The threads themselves never seal in AN connectors but the tapered ends (cone) of the fittings does. Plus the sealant could get into your fuel rail and clog up everything. Picture below of completed assembly.

8. Make sure you double check everything is connected and fittings tightened. Reassembled back the air filter and piping assembly.
9. Reconnect battery
10. Start the engine and pray there's no fire (just kidding). Another pix of the completed assembly.

I'll be doing an article of the fuel pressure regulator end conversion later when I'm up to it and when most importantly budget permits.