Head Swap Done...yae!!!

[tec280zx]

Okay, so far i've got timing back to where i originally had it (slightly advanced), the inline resistor and a full tank of 91 octane. Thats the highest rating we can get in cali. These few things were enough to stop the pinging, i might even try advancing a little more. Later on this month i will buy a adjustable fpr and replace my fuel pump. It's starting go out.

 

[DAW]

As long as you're replacing the fuel pump, consider getting one of the high pressure Bosch or Walpro(?) pumps and run it with a rising rate fpr instead of adjustable. After the pump and fpr, you should have your engine noticeably more powerful than it was stock. If you're seeking more power, then turn you attention to a tuned, better flowing exhaust system. If you go with headers (there are no good OEM cast manifolds for round port heads, there are a few for square port), I recommend wrapping with heat insulating wrap as it improves performance and quiets the header. I'd also recommend some long secondary pipes before they merge, and the rest of the system as 2.25", not 2.5". Unless you've got welding/fabrication experience, you would want a good muffler shop to do the exhaust and have them weld on a flange for the O2 sensor. It can go farther back from the engine than stock, but substitute a 3-wire, heated, sensor. Put the header on yourself, then dolly it, flat tow, (or open header) to the muffler shop. At this point it makes no sense to put in a cam, etc., unless the exhaust is done. DAW

[tec280zx]

What are the advantages of a rising fpr versus an adjustable one? As far as exhuast i have a free flowing muffler and 2.25 piping up to the cat. I still need a header, piping from header to cat, and a new cat, my old one is clogged up. Unfortunatly no one will modify the piping between the header and cat for emission purposes.

Right now a new cam is financially out of reach so that works out anyways.

[DAW]

A rising rate fpr matches pressure to engine speed so that at high air flow through the engine, high fuel flow is provided. An AFM does this electronically, a rising rate fpr, mechanically. Adjustable fpr sets a fixed pressure which is usually higher than stock and thereby enrichens the mixture, but it is not matched to engine speed/demands for more fuel.

 

I got the same thing from exhaust shops, although when you think about it rationally, how could adding a better tuned free-flowing engine-to-cat system which is more heat-preserving with wrap than the stock system, lead to any significant increase in emissions? They've got to go the CYA route though. I ended up buying a wire feed welder, teaching myself to weld a bit with it, then using a pile of auto-store pipes & elbows to configure a system. It was time consuming but gratifying, and the welder is one of the best purchases I've made! DAW

[Lockjaw]

A rising rate FPR is one that raises fuel pressure in relation to boost pressure by some multiple. ( say 4:1 which means every pound of boost over O adds 4 extra psi of fuel pressure versus the stock FPR adding one) . An adjustable one, like the one I described from JWT, maintains the same function as a stock FPR, it is just that you can set your fuel pressure where ever you want.

 

Usually the spec for fuel pressure on a Datsun is so many psi at O vaccuum. We will use 36 psi, since that is what mine is set at. So when the vaccuum line to the vaccuum port is not connected to the FPR, I have 36 psi of fuel pressure in the fuel rail. When I connect the vaccuum line, since my car pulls 19 inches of vaccuum at idle, it pulls the fuel pressure down to 26 to 28 psi. As my car comes up on boost, every psi of boost pressure I add over O adds one pound of extra fuel pressure. So 10 pounds of boost would give me 46 pounds of fuel pressure. See?

 

On your car, you could install an adjustable FPR, bypass the factory one on the fuel rail, and richen or lean out your mixture by setting your fuel pressure higher or lower than 36 psi, which is referred to as your static fuel pressure. Check a manual to make sure, I do not know what static is on an NA engine. The higher the fuel pressure, the more fuel that gets squirted in by the injector. Injectors are rated at a specific fuel pressure BTW.

 

If you need a good pump, Cartech has a peirberg which is 200 LPH pump, and it come encased in rubber and fits well in the factory bracket. You will need to get a fitting for it at the parts store so you can slip on the fuel line. I think it comes with a banjo fitting.

 

You don't need a rising rate of gain pressure regulator unless you are turbocharged, and you have to have a very stout pump to use one because any kind of decent boost will seng your fuel pressure to 90 psi or better. I had one on my turbo 240, and had to do a lot of playing with it to keep it from overfueling in 4th and 5th gear since I could get full boost on an engine that was essentially lugged down. Talk about fouling out some plugs.

 

You may also want to pull your plugs in a few days and see what they look like. They should be kind of a tan color, if they are black you are to rich, and if the are real light, you are to lean.

 

Sounds like you are making some progress. Pinging sucks.

[yo2001]

I'm N/A and using just a adjustable FPR. It's set at 3 bar at idle. right on 50psi with 0 vacuum. works good with 274 cam.

[DAW]

Rising rate fpr can be used on na or turbo engines and they are calibrated for the specific application. From "How to Build & Modify Intake & Exhaust Systems" by Ben Watson: The "Rising Rate" fuel pressure regulator uses increasing manifold pressure to increase the fuel pressure. Unlike most stock fuel pressure regulators which raise the fuel pressure in a single step the rising rate regulator increases the fuel pressure at the same rate that the manifold pressure increases. Thus, the pressure differential between the air in the nanifold and the fuel is a constant.

 

BTW, a maniflod pressure changing from -12 to -2 is an increasing manifold pressure. DAW