# 3-Bar or 4-Bar FPR? Need a straight answer from someone who knows!!!



## Mspeedy3 (Jun 20, 2009)

Hey-

So I found that my problems are from a shot OEM FPR (lean/rich codes from not regulating properly), and needs to be replaced.

Its a 2001 AWW 5-speed, APR loaded chip, K&N, DV etc. but stock turbo/injectors/fuel pump etc... mostly just bolt-ons

On the 93 tune in my area, it runs about 16-18psi

Basically, *Can I rip out the OEM 3-bar regulator (Bosch), and drop in a 4-Bar (Bosch)?*

If not, anyone recommend anything else as a better alternative to the OEM 3-Bar?

Im asking becasue the stock 3bar is about $200 up here, and if I was going to order from ECS, the 4bar is a bit cheaper... so just wondering if I can do a straight-up swap, even if it doesnt help in the performance department.

Thanks:biggrinsanta:


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## groggory (Apr 21, 2003)

It will fit, but just buy the 3bar. Do what your tune calls for.


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## Mspeedy3 (Jun 20, 2009)

Perfect - Thanks!!


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## Cryser (Sep 9, 2009)

with a 4bar your going to be running very rich at WOT and you'll end up lossing a bunch of MPG for basically nothing. If you are really up to it you can get an adjustable FPR and a FPR gauge from ecs or 034 motorsports and toss those in and just adjust it to 3 bar.

But yes if you want a straight drop and go solution just get another 3 bar and call it a day 4 bar is too much for the stock turbo


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## VWJetta27 (Jan 30, 2009)

groggory said:


> *Do what your tune calls for.*


dont run a 4bar fpr unless it is needed... example revo stg 2 calls for a 4bar fpr because it is specific to the tune


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## boost_addict (Dec 4, 2009)

use what your tune requires, it will not run right if you fpr does not match what your tune requires


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## Zneith (Jan 4, 2010)

^ what everyone else has said. The only time i heard of using a 4 bar was a ko4 and the *tune called for it.* That seems to be the most important. If it doesnt call for it, simply dont use it.


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## chaveezy (Jan 31, 2010)

Just pick up a stock replacement FPR from autozone or napa auto parts, they're like $50! 

But yes, you will want to run the one specific to your tune. The guy I got my GTI from had a 4BAR installed on a Mika Fuel Tune w/ 630cc injectors and it was running like crap until I figured out it was a 3BAR tune, switched it out with a $50 FPR from Autozone, problem solved!


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## theswoleguy (Jan 25, 2006)

3 bar or 4 bar its only 15% more fuel and the car will adapt any fuel out that is needed. your fuel trims are probably off as is anyway, get whatever you want and adjust it if you need to via vagcom its not that difficult.

i ran 4bar for many years, hell ive not seen a 3 bar in 4+ years. my software also didnt require it nor was my software made for E85 (requires 30% more fuel) all have ran just fine. 

your car will not blow up and really wont have any issues once you check/adjust your fuel trims.


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## VWJetta27 (Jan 30, 2009)

theswoleguy said:


> 3 bar or 4 bar its only 15% more fuel and the car will adapt any fuel out that is needed. your fuel trims are probably off as is anyway, get whatever you want and adjust it if you need to via vagcom its not that difficult.
> 
> i ran 4bar for many years, hell ive not seen a 3 bar in 4+ years. my software also didnt require it nor was my software made for E85 (requires 30% more fuel) all have ran just fine.
> 
> your car will not blow up and really wont have any issues once you check/adjust your fuel trims.


so in a round about way he is saying its pointless, cuz you'll just dump more fuel.. and if your fuel tables have to adapt to much you can run into problems...and plus why waste the gas..


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## theswoleguy (Jan 25, 2006)

actually you wont waste any gas at all bc its only 15% more fuel, which your ecu will adapt out so you wont waste it, the factory ecu can adapt ±25% so you are fine either way. i got better fuel mileage running at 4bar bc the fuel is under more pressure...


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## T-Boy (Jul 16, 2003)

theswoleguy said:


> actually you wont waste any gas at all bc its only 15% more fuel, which your ecu will adapt out so you wont waste it, the factory ecu can adapt ±25% so you are fine either way. i got better fuel mileage running at 4bar bc the fuel is under more pressure...


This means better atomization....or a round about way :laugh:


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## VWJetta27 (Jan 30, 2009)

theswoleguy said:


> actually you wont waste any gas at all bc its only 15% more fuel, which your ecu will adapt out so you wont waste it, the factory ecu can adapt ±25% so you are fine either way. i got better fuel mileage running at 4bar bc the fuel is under more pressure...


true but if he's tuned which he is, along with every time you remove the battery or reset the ecu in anyway possible your gonna lose all of your short term fuel trim tables..putting you right back to the long term fuel terms programmed from manufacturer or in his case the the tune your running. which means the vehicle will have to go through and "relearn" why its being supplied more fuel than necessary and adjust as needed so you will regardless at some point be wasting more fuel.

if the tune says 3bar on stock injectors or what not why would you run a 4bar...that is definitely not a 3bar as specified? there is no point..will your ecm adpadt yes but under any conditions where short term fuel tables are ignored you will more than likely dump more fuel than needed which again is pointless. if you really wanna test this out get an adjustbale FPR and play around with it.

would you run a 3bar on a 4bar tune? no! so why do the opposite?


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## VWJetta27 (Jan 30, 2009)

T-Boy said:


> This means better atomization....or a round about way :laugh:


not at all actually. since the shot of fuel between a 4bar and 3bar(4bar is about 15psi more) is shot on the back of the intake valve you will find that atomization stays pretty close in ratio of fuel supplied with pressure between a 3bar and 4bar.

if 4bar's were really that much better wouldnt a lot more people be running them? although most stock and stg1&2 tunes only call for 3bar fpr's you dont see a lot of people running a 4bar on it..


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## T-Boy (Jul 16, 2003)

VWJetta27 said:


> not at all actually. since the shot of fuel regardless of pressure(4bar is about 15psi more) is shot on the back of the intake valve you will find that atomization stays pretty close in ratio of fuel supplied with pressure between a 3bar and 4bar.
> 
> if 4bar's were really that much better wouldnt a lot more people be running them? although most stock and stg1&2 tunes only call for 3bar fpr's you dont see a lot of people running a 4bar on it..


The atomization is a cloud of fuel, regardless of where it's shot, the atomization is finer. 
Reason why most tuners stay with 3bar fpr is because it comes with the car....if the car came with a 4bar more tuners would tune for it. 
Bottom line, if the car is tuned for a 3 bar, stick with it....


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## VWJetta27 (Jan 30, 2009)

T-Boy said:


> if the car came with a 4bar more tuners would tune for it.
> Bottom line, if the car is tuned for a 3 bar, stick with it....


exactly

and i corrected my post that t-boy quoted, not regardless of pressure because with substantial changes you will see a difference, but between a 3bar and 4bar the atomization will barely increase.


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## All_Euro (Jul 20, 2008)

I found that with my Stage 2 file, the stock injectors were running duty cycles in the mid 90's. Unitronic didn't want to customize a file for bigger injectors so I chose to go with an adjustable FPR from 034 motorsport. 

The FPR is set at 4 bar and duty cycles along with fuel trims are right where they should be. Car is running better than ever and I have room to tweak up or down should I need it :thumbup:


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