Stock SR fpr (rrfpr?)

[freakyjason]

I've been searching around a lot (yes, i have gone over the sr faq as well) and have not found an answer to my seemingly simple question: Is the stock sr20det fuel pressure regulator a rising rate fuel pressure regulator? I'm planning on doing a build (GT2871r, MSD 72lb injectors, JGY fuel rail, walbro pump, JWT tune, JWT s3 cams and other supporting mods) and am wondering if i should run a rising rate fuel pressure regulator or if i could just get away with a nismo or megan? Thanks!

[Hijacker]

It has two settings pretty much. One for on vacuum and one for off vacuum. Not a rising rate model.

[Emperor_Tha]

quick question what is a rising rate?Is it fuel pressure = rpmxboost presure (just guessing)3k rpm @ 0 psi= 36 fuel psi3k rpm @ 5 psi= 50psi( just guessing)

[wzntha]

.

[freakyjason]

quick question what is a rising rate?Is it fuel pressure = rpmxboost presure (just guessing)3k rpm @ 0 psi= 36 fuel psi3k rpm @ 5 psi= 50psi( just guessing)

Actually, its a 1:1 ratio fuel pressure increase to amount of boost.

isn't a rising rate fpr used when you install a turbo in a car that was originally NA? i thought i read that somewhere...but i believe the difference is that it increases exponentially, instead of linearly.

Yeah, see that's what i kinda thought. However, looking at a few build threads on this forum, i've seen a couple people using rrfpr on their sr20det's. Codyace told me that it's pretty much a necessity and i've ridden in his car. It runs AMAZING! But i've also seen a few sr builds on here with comparable parts lists to codyace's and they use either NISMO, Megan or some other non rrfpr. i dont know personaly how their cars run though. I emailed this same question to JWT a few days ago since they are going to be doing my tune. No response yet though.
Modified by freakyjason at 12:10 PM 10/9/2008

[freakyjason]

Does anyone have any input as to which type i should run for my build though? Can i get away with using a non rising rate in other words?

[freakyjason]

It has two settings pretty much. One for on vacuum and one for off vacuum. Not a rising rate model.

Hmm. I have some conflicting info here. I emailed JWT a while ago as they will be doing my tune and they just responded today. They said:

"The fuel pressure will need to stay at the same as stock base which is 43.5 psi at idle with vacuum reference off. The OEM regulator is a 1 to 1 type and it needs to stay this way as a 1 to 1 type. This means that for each additional PSI boost pressure, the regulator would add 1 more psi of fuel pressure. So for 21 psi of boost, the fuel pressure better be at about 64.5 psi (43.5 psi + 21 psi)."

So at this point, my question as to which type of fpr to get has been answered (since JWT will be doing my tune), but i'm not so sure who to believe about the stock fpr

[the converted]

You do NOT need a rising rate, they are bandaids for Hondas

[freakyjason]

You do NOT need a rising rate, they are bandaids for Hondas

I do strongly agree with that. However, JWT is saying to get one for their tune and i have personally experienced one working well with their tune. I guess im going to email them back and explain to them that there is a difference in information between what they told me and what the general consensus on here is.

[the converted]

JWT is saying to get one for their tune .

No they are not. a linear rate (stock) will raise 1 psi for every 1 psi change in manifold pressure. A rising rate will do 1 psi around atmostperheic pressure but as you get into boost will start adding more and more (3 psi increase going from 5 to 6 psi of manifold pressure ect)

I don't know the exact rate correlations for a rising rate but numbers are for example. As long as your fuel pump isn't out running your stock regulator you won't have any issues keeping it.

[freakyjason]

No they are not. a linear rate (stock) will raise 1 psi for every 1 psi change in manifold pressure. A rising rate will do 1 psi around atmostperheic pressure but as you get into boost will start adding more and more (3 psi increase going from 5 to 6 psi of manifold pressure ect)

Yep, just received an email from JWT confirming this. Turns out we had different definitions for rising rate fuel pressure regulators.

As long as your fuel pump isn't out running your stock regulator you won't have any issues keeping it.

It is. Im running a bit rich at idle at the moment and have heard that the stock fpr has a hard time holding back a walboro fuel pump. I'll probably get a NISMO in that case. Thanks for the help!
Modified by freakyjason at 4:31 PM 10/16/2008