Welcome to the North American Subaru Impreza Owners Club Monday December 11, 2017
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Go Back   NASIOC > NASIOC Technical > Normally Aspirated Powertrain

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads. 
Reply
 
Thread Tools Display Modes
Old 11-29-2000, 10:21 AM   #1
Diz
Scooby Specialist
 
Member#: 874
Join Date: Feb 2000
Chapter/Region: RMIC
Location: Colorado Mountains
Vehicle:
2004 STi
16 Shelby GT350

Question Bell RRFPR (model 20005) - too much fuel?

Here's the story -

I am using a Bell rising rate fpr with my turbo. I think I am getting a bit too much fuel, but I am not sure. Here are the symptoms - I have nice, smooth acceleration up to about ~3500 RPMs. At that point, the car lurches, slows and then resumes normally. This only happens when I am depressing the accelerator ~20-30%. Hence, this happens quite a bit during normal driving and is very annoying.

My hypothesis is that the FPR is dumping too much fuel when it sees a near atmospheric pressure in the manifold. After the boost comes on strong, everything is fine. Also, if I REALLY get on it or go REALLY light, this does not happen.

Has anyone had any experience with this? Can you confirm or deny my suspicions? Thanks in advance.

-Paul (aka Diz, aka Bodhi)
* Registered users of the site do not see these ads.
Diz is offline   Reply With Quote
Sponsored Links
* Registered users of the site do not see these ads.
Old 11-29-2000, 11:24 AM   #2
jdchmiel
Scooby Newbie
 
Member#: 926
Join Date: Feb 2000
Chapter/Region: South East
Location: Raleigh, NC, USA
Post

do you have a boost gauge?
if so:
-what pressure does it happen at?
if not get one
do you have an a/f gauge
if so:
-what does it read before, during, and after

do you have a GOOD EGT gauge?
if so:
-temps before, during, after
if not strongly suggest you get one, and a good one that has a fast response time..

not familiar with the rising rate regulator, but it must have an atmoshperic pressure reference somewhere.. is it getting the same atmoshperic presure as the ecu?? ie no long hoses or ties into the intake tract anywhere??
jdchmiel is offline   Reply With Quote
Old 11-29-2000, 02:27 PM   #3
Diz
Scooby Specialist
 
Member#: 874
Join Date: Feb 2000
Chapter/Region: RMIC
Location: Colorado Mountains
Vehicle:
2004 STi
16 Shelby GT350

Talking

Thanks guys. I'm going to go adjust the FPR soon. I do have a boost gauge, but the EGT and rich/lean have yet to be installed.

-Paul
Diz is offline   Reply With Quote
Old 11-29-2000, 10:30 PM   #4
ImprezaRS dot com
over boosted again
Moderator
 
Member#: 1458
Join Date: May 2000
Chapter/Region: RMIC
Location: Colorado Springs CO USA
Vehicle:
2017 WRX Limited
2015 Forester XT, Tribeca

Lightbulb

I have a Bell 20007 RRFPR and have never experienced this problem with my MY00 turbo. So, the next thing to follow means I don't know what I'm talking about.

I wonder if you are having detonation and then excessive retard - especially since your water injection doesn't activate till 5 psi boost. Maybe you are too lean because at 3,500rpm and partial throttle without much or any boost, the RRFPR shouldn't be dumping in any extra fuel like you are thinking. As you know, the RRFPR raises fuel pressure a certain amount per each psi of boost, like a max of 5 psi fuel pressure rise per 1 psi boost when set for max. So, no boost = no fuel pressure rise.

If this helps, my model 20007 is good for 7 psi fuel pressure per lb of boost, up to 85 psi max fuel pressure, but I am not anywhere near the max setting - max set screw is two turns out from max. I have the baseline pressure screw set for 6 turns in from loose.

Also, be very careful without knowing EGT's - when my car is running good, I still find EGT's can get hotter than they should when I am pushing the car over 100 mph full throttle. With EGT probe in the turbo up-pipe I cannot use anyone else to help tune the EGT's except JC (since that is where all their EGT probes go, vs in the header inches off cylinder #3). They said keep EGT at 1200 - 1300 for that location, based on their experience with cars that have A/F meters and fuel ratios just right. Max allowed is 1400 John sez, and I hit 1475 today at 5,700 rpm top gear. I shoulda looked at it sooner and let off.

The problem I have is the need for ignition timing retard, to get better top end power and get EGT's down at high speeds. When I add fuel with the RRFPR or AFC to get the EGT's at high speed just right, the car drives poorly and too rich around the city, and bogs down at 5,500 rpm and above.

I will be happy once I get a fuel pressure gauge and A/F meter to fine tune the car too. But an APEXi ITC or MSD boost controlled timing master might be the first thing I do...

Larry www.ImprezaRS.com
ImprezaRS dot com is offline   Reply With Quote
Old 11-30-2000, 01:17 AM   #5
rao
Scooby Specialist
 
Member#: 52
Join Date: Jun 1999
Location: Naperville, IL
Vehicle:
2005 Legacy GT
98 BMW 540i LS2/T56

Post

It could be that you have the FPR set to add fuel with too little boost. If the problem occurs at 20-30% throttle, you should not have too much boost. I would try having the pressure rise come on later.
rao is offline   Reply With Quote
Old 11-30-2000, 07:03 AM   #6
Diz
Scooby Specialist
 
Member#: 874
Join Date: Feb 2000
Chapter/Region: RMIC
Location: Colorado Mountains
Vehicle:
2004 STi
16 Shelby GT350

Talking

Larry -

Thanks for the info. However, it is not entirely accurate. The 20005 can be configured to begin raising fuel pressure when it sees atmospheric ( 0 on the boost guage ) in the manifold. That is controlled by the "big screw" on the top of the unit. Hence, it appears that my FPR was raising fuel pressure too soon.

Also, I am pretty sure I wasn't getting detonation. I backed off the amount I was raising fuel pressure and then did a run. Everything was happy. I then attempted to enrichen the mixture a bit with the AFC. When my car hit the RPM range in question under boost and my heavy left foot, accelleration dropped off quickly. After leaning the mixture a bit (~5%) in the afformentioned range, the car pulled much better. Take it easy and I hope your car is running well. Try to stay out of the 100mph range. Instead of referring to you as "Dr. Larry Ganz", we will have to start calling you "inmate Larry Ganz". (during visiting hours, of course)

Thanks for your input, everyone.
Diz is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Can too much fuel kill your IAMs? Fongers Engine Management & Tuning 8 01-26-2009 03:24 AM
Can a misfire be caused by too much fuel being pumped through the injectors? WRXfoME Newbies & FAQs 11 10-17-2007 10:44 AM
Too Much Fuel? spoolinsuby Factory 2.0L Turbo Powertrain (EJ Series Factory 2.0L Turbo) 6 04-17-2005 02:19 PM
Won't start....too much fuel and i dont' know why Andursun0013 Normally Aspirated with bolt-on Forced Induction Powertrain 9 01-05-2004 02:01 AM
Too much fuel pressure at idle? I have the fix.........finally ARG Technical Forum Archive 12 08-15-2000 01:12 AM

All times are GMT -4. The time now is 08:23 PM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2017 Axivo Inc.
Copyright ©1999 - 2017, North American Subaru Impreza Owners Club, Inc.