What is the difference and which is better for a FD? Is a Bypass Regulator the same as a rising rate FPR. Feel free to recommend a different FPR. Thanks for helping me choose.



Aermotive
http://www.rx7store.net/product_p/aeromotive%20fpr.htm

vs

Sard

http://www.rhdjapan.com/jdm-low/SARD...te-Black-55194

 

they are both rising rate. i dont think there is really a difference with them. maybe they are different names for the same thing. I would go with the aeromotive. i really like mine. does the sard have a port for a guage? i know the aero does. a guage is important.

 

Thanks again for the info. What model to you have? What psi setting do you think I should set it to for 400~ whp @ 15 psi w/ 850 x 4 injectors and denso 300 flow rate pump?

 

First see where you're at after the rewire. I would set the fuel pressure to standard to begin with 40 - 42 without the vacuum line connected. Then see how your duty cycles are. If they are getting way to high then gradually turn it up. What ecu are you tuning with?

 

I think mine is the same model. It looks identical to that one. I got mine used and i don't see a model number stamped on it. Have your injectors been professionally cleaned at all?

 

I have a Microtech LT8. I am still learning it so I am not quite sure how to tell the duty cycle. I mainly use a Load screen that sets a number from 0-10 at boost level (at increments of 2 psi up to 20 psi). I also use RMP_wot map, tuneable by percentage, I am not sure if it is duty cycle percentage... The injectors were purchased about 10k miles ago. They were Mazda 850cc OEM. Which model FPR do you use.. is it the Aermotive 6000-A?

 

Covering the terminology -

Rising rate and adjustable are two different aspects of a fuel pressure regulator. "Rising rate" means you can change the rate that the fuel pressure rises versus boost. This is really a trick used when adding a turbo to a non-turbo car for an easy extra fuel method - for each pound of boost, add 2 or 3 or 5 psi of fuel pressure. More fuel pressure means more fuel to go with the boost. While that sounds dandy, they're a bitch to tune right and give sloppy, inconsistent results.

That said, a well designed fuel system on a turbo car will have a 1:1 ratio. Fuel pressure will increase 1 pound for every 1 pound of boost. This is to keep the difference between air pressure in the manifold and fuel pressure in the rail the same. Let's say you ran 20psi of boost, and had 20psi of fuel pressure. Guess what? The fuel wouldn't squirt out - you need to go from high pressure to low pressure to get a "squirt".

Most aftermarket fuel pressure regulators let you adjust a base fuel pressure, typically 35-40 PSI. This is the fuel pressure it runs at atmospheric pressure in the manifold - no boost, no vacuum. The vacuum nipple on the FPR will adjust the pressure up and down with manifold pressure. Being able to set the base rate is important, as a large fuel pump and other factors can change your base rate, making the car too rich or too lean.

The stock FPR is a 1:1 ratio regulator and works well, but it is not adjustable and isn't easy to use with an aftermarket fuel rail. With a large fuel pump, the stock FPR can easily be over-run resulting in higher than normal fuel pressure, which can be fun to try and tune the car around.

For recommendations on FPR's, hit the single turbo section and do some reading. Most people use Aeromotive, from what I recall.

Dale