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rising rate fule perssure regulator


DAT240Z

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Guest bastaad525

I'm assuming this is for a turbo setup.

 

I've been looking at FPR's and RRFPR's for some time now as well.

 

A LOT of interesting info has been proposed to me that suggests that a rising rate regulator is NOT the way too go, that it will be very hard to tune and will most likely run way too rich on boost.

 

The problem is, the usual RRFPR (like the Cartech FMU, for example) is set to start adding fuel as soon as boost comes on. With the stock '81-83 ZXT, you already HAVE more than enough fuel when boost first comes on. When I dynoed my bone stock setup, it runs SUPER rich from onset of boost at about 2500rpm to about 4500rpm. Air/fuel ratio was at 10:1 or so. I've seen several other zxt setups dynoed with the same results.

 

The stock ZXT only starts to run lean above about 5k rpm, this is because the stock airflow meter is maxed out/wide open at wide open throttle, by about this RPM. So after that RPM, the ECU has no way to accurately measure the amount of air getting sucked in. Since the stock ZXT came with a popoff valve that was set to vent any boost over about 9psi, the ECU is only programmed to be able to handle up to 9psi of boost, so after the AFM maxes out, the ECU is going on a preprogrammed 'map', measuring only RPM, head temp and air temp, and 'assuming' no more than 9psi present... heheh like who runs only 9psi :) so it runs lean.

 

So an RRFPR will add too much fuel from 2500 to about 5000rpm... not good. RRFPR's are intended for people who are running a turbo on a motor that wasn't turbocharged originally, like guys who put turbos on honda motors.

 

Anyways, I can tell you this much... you're already taking care of your need for more fuel with the 370's.... adjustable fpr's are for cheap bastards like me who dont want to or can't install bigger injectors, to sort of achieve the same thing... you really only need or want one or the other, you shouldn't need both.

 

installing the 370s will make your car run richer throughout the rev range right off the bat. What you'll need to do after installing them is adjust the spring tension on the AFM flapper, tightening it up (most people adjust the gear clockwise about 18 teeth and get great results) to trick to ECU into thinking less air is flowing. This will lean out your idle, cruising, low and mid rpm mixture (again, up to 4000-5000rpm) to compensate for the richer running injectors... however it will leave the extra fuel at the top which is where you need it.

 

If you still want to get an adjustable FPR, there is a cheap NON rising rate one, this is the one I want to get, it's made by MSD.

 

http://www.overboost.com/obs/product.asp?pid=2628&cat_id=13&cat_name=Fuel%20Pumps%20and%20Regulators&sc_id=55&sc_name=

 

Overboost.com is selling them for about $50-60.

 

You will also want a fuel pressure gauge, me and a couple other guys made one ourself using common parts from Home Depot, cost is about $15.

 

You just need to make a tee out of some brass fittings and use a water pressure gauge, they sell them in the sprinkler/plumbing section. I can send pics of it if you want, PM me if interested.

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Whoa WHoa now this is some new (hopefully good) info to me. I'm putting my turbo motor together right now using 500cc RC's and a JSK custom fuel rail. I was just about to purchase an AEM or Aeromotive adust. FPR. Are you saying that this is redundant? Does the amount of boost I'm running have an bearing on this? I'll be running 15psi street and 21 track with a T4. I rather spend the money elsewhere if I don't need an FPR.

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  • 2 weeks later...
Guest bastaad525

If everything I've been told is correct (it certainly does make a great deal of sense) than a rising rate regulator would be more harmful than helpful on a L28 turbo setup. Those rising rates are more intended for guys who are putting turbos on motors that were previously N/A.

 

However, I'm not saying just a straight up adjustable FPR is useless. A regular, non rising rate, but vacuum/boost referenced adj. FPR can be helpful to let you 'cheat' a little and get some extra fuel flow out of the stock injectors. Not sure how much extra flow you can get out of them, but it's a good alternative to buying a set of bigger injectors if you dont need a LOT more fuel.

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Guest ZmeFly

Bastaad is correct, those RRFP's dump lots of fuel, that is if the injectors are up to the task.

 

These things arent like your stock or most manifold referenced universal type AFPR's like SX or Aeromotive that raise pressure from what you set it at ex. 37#'s up from there at a 1:1 ratio.

 

FMU's or RRFPR's usually go at a higher rate of 5:1 or even more and thats just to much.

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