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Discussion Starter · #1 ·
I figure this is a better way to document individual questions we all have with the honda swap.

I have a question about the fuel system and how to handle that in the lotus chassis.

From what I have read the OE chassis for the K series (RSX, TSX etc) are "headless" fuel systems. Here is an excerpt from a honda-tuning article to explain more.

The K series has a "headless" fuel system, meaning the regulator and return line are actually in the tank. There is no fuel return from under the hood. This gives Honda the advantage of building the pump, regulator, return and fuel level sensor all in one unit. It also helps reduce evaporative emissions.

Vargas tells us the down side to this type of system is it becomes very difficult to build extra fuel pressure. It used to be that adding a fuel pressure regulator would build enough additional pressure from the stock pump to make forced induction or big nitrous applications relatively simple. The way the K series' fuel is supplied makes building adequate pressure much more difficult.

Unfortunately, there is no simple workaround for this problem. The stock fuel pump is capable of about 55 lbs of pressure, adequate for a low-horsepower (40 hp or so) nitrous system or very low-pressure turbo or supercharger. Any higher and the system will run very lean-`a dangerous condition that could result in a blown engine.

For higher horsepower applications, a return line will have to be run, meaning the single-piece fuel pump/regulator/return/level sender assembly in the tank will have to be separated into individual components. This is an expensive and time-consuming process that would make a bolt-in kit a more difficult proposition. Of course, that hasn't kept HKS, GReddy and Jackson Racing from continuing to develop kits. Racing applications that need more than just a few pounds of boost are still in the future.

Read more: Honda Civic Si, CRV & Acura RSX New K-Series Engines - Honda Tuning Magazine


The thing that got this whole question rolling was the innovative fuel plate that's now available:

CorSport: Lotus - 2005+ Lotus Elise/Exige - 50902

I'm assuming that the Lotus fuel system is also headless? This plate is only required if you need more fuel pressure/flow and want to run an external fuel pump, correct?

If we can sort this out I'd like to make a parts list of items required if you're running a lower-hp NA swap, or a higher hp forced induction swap:

NA / Low HP Required Parts

Fuel Rail?
Lines?
Fittings?
Injectors: OEM K20/K24, RDX (P/N16450-RWC-A01)

Forced Induction / High HP Required Parts

Fuel Rail?
Lines?
Fittings?
External Pump?
Pressure Regulator?

Let's pool resources here and help piece this together. I'll edit this post as we learn more.
 

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Discussion Starter · #3 ·
By the way they dont make that fuel plate, also you dont need it
THIS is what I'm talking about.

You need to be clear. All of the responses are broken sentences with no clear answers.

What do you mean they don't make the fuel plate? I remember seeing aztec using one in his thread somewhere.. WHY is he using it?

WHY don't we need it, because the lotus fuel system is also headless?
 

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Just by replacing the OEM Toyota Denso fuel pump with a Walbro 255-l/hr pump should support at least 500-HP (if not more)! How much HP are you looking to make? All you will have to do is make a custom, in-tank, 2-wire, harness for the fuel pump and replace the supporting cap with a Lotus Cup 260 (or aftermarket) part...
 

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Just replace the pump with an aem 340lph. I have a -6an radium fitting that goes on the tank in place of the oem fitting, run a line to the rail, regulator on the other end, and the return line to to lower part of the filler neck. Thats what a few of us have done. No need for that plate.
 

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re: Fuel system

All good advice, above.

As a reference, read the manual/catalog at Kinsler Fuel Injection . It is a bible for fuel system design. It explains the compromises of in-tank regulators, etc.

The best design is the proper-sized pump in the tank -6 or -8 line to the fuel rail, regulator on the other side and the same return line back. Regulator should be very close to the fuel rail and vacuum-referenced.

Kinsler has all the pump sizing info in a nice chart. Rule of thumb Walboro to 450hp, Bosch -044 to 650, and Weldon for everything else. :)

Anton
 

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Discussion Starter · #7 ·
All good advice, above.

As a reference, read the manual/catalog at Kinsler Fuel Injection . It is a bible for fuel system design. It explains the compromises of in-tank regulators, etc.

The best design is the proper-sized pump in the tank -6 or -8 line to the fuel rail, regulator on the other side and the same return line back. Regulator should be very close to the fuel rail and vacuum-referenced.

Kinsler has all the pump sizing info in a nice chart. Rule of thumb Walboro to 450hp, Bosch -044 to 650, and Weldon for everything else. :)

Anton
Anton

Aren't these modifications required only for forced induction? What if your just running the K-series NA? I'm only looking to make 240hp or so on a K24.

I still need to understand if the stock lotus config is headless, as it is in the kseries hondas.. I've never heard many people dealing with this issue for the NA swaps. Only the forced induction guys, so I have to assume it is..
 

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use -6 line unless you're going for over 500hp (actually more). You will need a fuel pressure regulator, lines, dont necessarily need a new fuel rail (you can keep the stock dead head system, run the fuel return from the regulator), or you can use an aftermarket rail with a standard pass style setup.

Basically,
straight swap:
stock injectors, stock fuel pump, -6 line and FPR

High HP:
just up the injectors and the pump.
 
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