4.0 bar fuel press regulator

Don't they use the SMT-6 boxes in Greece?

Joe

A couple of other points on the 4 bar reg.

It does improve the fuel atomisation (which gives the improved throttle response), but as Begbie says the spray pattern on the injectors can get unpredictable, so the higher the fuel reg the less boost you can safely run paradoxically.

The OE fuel pump probably cannot fuel 1.4 bar with a 3.8 bar reg on any coupe, you will get pressure drops in the rail which is pretty dangerous. You must use an uprated fuel pump no matter what IMHO

Injectors do not always fuel linearly at different pressures and duty levels, so if the ECU knows they fuel less at some point then it might have a compensatation in the map. When you increase the pressure you are also moving these compensation points all over the shop because the compensation is different due to it being at a different pressure - same goes for messing about with the boost (as that also directly affects the fuel pressure - the pressure is regulated by a feed to the boost), which is why you end up with lean spots and over rich spots after upping the boost. I would say that this is a lot of the reason why people get different fuelling results with the GTech chips.

The ECU will compensate to a certain extent when you fit a different regulator, but there is a limit to its adaptability.

Finally, I would echo Rog's sage advice - if you mess with the fuelling or boost in any way (including some of the fairly simple mods) then you should always get your fuelling checked out.

i do run a walbro 255 fuel pump.
you could see my mods in the beginning of the post.
gt 28rs
pace fmic
2,7 decat
walbro 255
str.induction pipe
bonalume dump valve
gtec ii

and a prv from cosmo,not fitted yet.
ebv contrilling boost.
what should i do with all this mods?????
use the prv?
what boost?
use the 4.0 regulator?
??????
?????
??????

your opinions from all of you mates,much acceptable.
thank you all guys...

fit the PRV at your desired boost level, then get the car on an RR for a fuelling check.

if you have ANY lean spots then you need to look at some kind of mapping.

mapping will find out if your mechanical setup needs uprating further, or if you have adequate fuel supply throughout the rev range.

I run an identical setup to you Chris also with a gtec ii.

I haven’t had chance to get down a RR to get my fuelling checked, so I have been running at 1.2 bar for about 3 months it seems fine no signs of pinking but i will continue to run low boost until I get it checked.

IMO you dont need a higher fuel pressure reg if you have a walbro 255 fitted there will be plenty of fuel at the rail, the uprated reg would only be needed if you were still running the standard fuel pump.

I think some peeps are getting a tad confused.

Yes, the ECU dictates how long the injectors stay open (the duty cycle) so a higher rated FPR wont affect this but....

The ECU is not the only thing that determines how much fuel is injected into the engine; fuel pressure also factors into this equation. The higher the fuel pressure, the more fuel is injected. The Fuel Pressure Regulator regulates the fuel pressure. The ECU does not control the FPR; it is controlled by your engine vacuum/boost. At idle when engine vacuum is high, it opens the valve lowering fuel pressure. At higher RPM's when boost is high the valve closes increasing fuel pressure.

So, fitting a 4 bar regulator instead of the standard 3bar will in theory allow a higher pressure reach the injectors and hence pump more fuel into the engine. This is not a good thing if you dont need more fuel.

As long as the regulating pressure is below that produced by the pump then the size of pump is irrelevant.

All IMO of course.

ok just for example lets say an injector squirts for a duration of 0.5 seconds (just for example) then closes.

with more fuel pressure it will still inject for 0.5 seconds, so the increase in fuel from increased rail pressure will be only small, argueably enough to cause engine problems.

the ECU has no control over mechanical parts, except the ones that it is monitoring through a sensor, i.e throttle position sensor.

paul at PTS advises uprating FPR's, saying it will enable better mapping with increased fuel pressure, but that isnt any good if the pump cant flow enough fuel to keep the rail pressurised wnough when at high RPM for long periods.

interesting discussion this.

Yep, agree with all that Rog.

flea - off topic, what mods you running to get 360bhp and what boost?

yeah flea,tell us your mods-boost
dan20vt,i do the same,run the car on ebv and 1 bar until i get it checked on a rolling road.
rog20vt you have been realy helpfull mate...

Also another thing with running a 4.0bar FPR and 1.2bar of boost, means you are putting the 255 pump near to lockout on fuel. These pumps are not good for high fuel pressures, running a combined 5.2 fuel pressure means the fuel pump is only going to be flowing a certain amount and wont be anywhere near the 255l

thanks begbie.....




would the 4.0 bar fpr work better with the coupe 20vt oe fuel pump?
or just the same?

Unless you have the high pressure version of the 255lph pump which I think almost no-one has....

I would never use a 4 bar FPR with the OE pump, it isn't built for it. Unless you want to run 0.8 bar boost then it would probably be ok

so johns,whats your suggestion for the above mods?
should i or shouldnt i use the 4.0 bar fpr?????

Hi,

I and my friend are using adjustable FPR together with Walbro 255HP pump. I run with 3.8 bar and my friend with 4 bar fuel pressure, neither of us have had any problems what so ever with that combination. Okay OE injectors are pretty much in limit above 340 bhp, A/F was, according to wide band lamda, around 13-13.5.
Also with boost of 1.6 bar I have never seen the fuel pressure under 5 bar, also in high rev's. The fuel flow is no issue with 255HP pump and high boost.

- Jari -

thanks jari,
SO many different opinions though.....
anyone else?

If you are just sticking a plug and play chip, then I would only fit an uprated regulator, IF you have an uprated fuel pump AND access to a wide band lambda to check the fuelling.
Even then ,it should only be fitted if you have documented fuelling problems.
Still this is very crude, and you will increase fuelling slightly across the whole rev range, at idle, part load etc etc , so is not ideal.

An uprated FPR can be used, of course with a custom ECU, mappable UCU, to wring a tiny bit more out of the injectors, but its hard to know how used OE injectors will respond, and again you will be increasing the fuelling at other parts of the Maps that say a piggyback ECU doesnt deal with ,say the Unichip for example, doesnt compensate the idle map.
When I spoke to Paul, he suggested, that at most you might get an extra 5% out of the injectors, really I think this is the most appropraite time to fit uprated regualtors.


The trouble is , a lot of peepes read these threads, and end up bunging on uprated regulators, in inappropraite situations ,just because 'everyone else has done it', and then never get things checked professionally ,and then wonder why their engine either breaks or loses power later on

Joe

thanks joe,thats very informing.....