Two simples questions :
1) if I have a rising rate Fpr do I also need an FMU?
2) If we go turbo do we absolutely need an afpr AND a FMU ?
an FMU IS a rising rate FPR
i prefer aeromotive adjustable fpr's (stay away from FMU's) and run an SAFC
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where is the problem with FMU??
First off you need a FMU to increase fuel pressure under boost. A FPR raises fuel pressure at idle and under WOT on a n/a car. If you are boosted and running bigger injectors, you need a adjustble FPR to lower fuel pressure at idle to have a smoother idle and not run so rich at idle. Problems with a FMU, you can not do a prefect tune, unless running a SAFC as well. Stand a lones tune better.
FU Tuning
Spotabee Racing wrote:an FMU IS a rising rate FPR
i prefer aeromotive adjustable fpr's (stay away from FMU's) and run an SAFC
Does an adjustable fpr is a FMU ? because I think that adjustable Fpr don't care about boost right?? If so what are their utilities.
Summary :
FMU are used to increase fuel pressure in the fuel rail as the boost increase .
So in fact it's a kind of rising rate fpr.
Safc is for fine tuning since it is for fuel curves adjustment I think ?
You only need a fpr if you get larger injcetors. But if you have the safc I believe you can take out fuel at lower rpm's and you wont need a fpr.
You could also get a sfmu which does both.
I dont see how you could tune just with a safc. It dosent adjust fuel in realtion to the boost only the rpm's. So if you get a boost spike your engine wont add any more fuel, and go boom. Mabye im wrong, but I think the safc and fmu are a team and work best together
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Does an adjustable fpr is a FMU ? because I think that adjustable Fpr don't care about boost right?? If so what are their utilities.
adj. fuel pressure regulator is to replace your STOCK fpr on your car....it does the same purpose as the stock its just you can adj. the pressure. Just as John Higgins said..if you have bigger injectors installed, the purpose of a adj. fpr is to bring your base fuel pressure down to compensate for the bigger injectors. if your running 19 lb injectors at 55 PSI at idle (63-65PSI WOT) and decide to put 30lbs injectors in..you can turn your adj. fpr down to maybe 35 PSI (43-45 PSI at WOT) to compensate for the bigger inj.
a adj. fpr does not care about boost..it actually does have a 1:1 ratio however...so it will prob go up in PSI per PSI of boost. but like i said..its only a 1:1 ratio.
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FMU are used to increase fuel pressure in the fuel rail as the boost increase .
correct..unlike the adj. FPR its more along the lines of 4:1 to maybe 14:1 ..depending on your application.
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So in fact it's a kind of rising rate fpr.
rising rate FPR and FMU are the same thing...some people call it FMU some callem RRFPR.
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Safc is for fine tuning since it is for fuel curves adjustment I think ?
SAFC are great electronic tools that trick the ECU into letting more fuel out..I learned on other posts that usually a SAFC cant handle the fuel demand alone...SAFC's and FMUs work good together..FMUs get you in the ball park and SAFC;s fine tune your fuel curve.
hope that helps...
that's fine in fact we can say that afpr best suit the n/a applications because in n/a we always have the same "boost" or should I say "pressure" .
So If we're planning to go turbocharged it's better to keep the Oem Fpr and buy a Fmu to have the appropriate pressure in the rail and then fine tuning this with the safc since we don't want too much pressure at idle and so on...
So in this way of thoughts afpr is not useful in forced induction applications right ?
i just don't like the way FMU's work honestly. i believe in a better degree of tuning.
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So in this way of thoughts afpr is not useful in forced induction applications right ?
is very usefull if you dont have a safc and you do have larger injectors. There are several different ways to set up your fuel system on a custom turbo. Each have there advantages and drawbacks. Just have to figure out whats best for your engine.
correct, and like i said above, i prefer an aeromotive fpr and an safc (or e-manage if you want to spend the money, it's an excellent system).
I was a retard, and now I'm permanently banned.
Spotabee Racing wrote:correct, and like i said above, i prefer an aeromotive fpr and an safc (or e-manage if you want to spend the money, it's an excellent system).
but your aeromotive fpr is in fact an adjustable fpr with a ratio of 1:1 no??
If so.. it means that your safc can do the same job as a Fmu? and "tell" to your afpr when to increase pressure ? but a normal fpr wouldn't be able to do the same job as your afpr? since you can adjust what you want with your safc?
no, the safc does not have boost detection. however, you tune the safc on a dyno and give more fuel accordingly when you are making boost and not making boost.
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alright but what is telling your afpr to increase pressure since a afpr can't detect boost?
an AFPR is getting a vacuum signal from your intake manifold. for example...my stock ecotec FPR sits at 55 PSI at -25 vacuum...when i WOT around almost zero level (atmospheric) its at 65 PSI...now thats a N/A engine.
Im pretty sure a FPR will still raise fuel pressure apon reaching pass zero level (boost PSI ++) its just gonna only raise it 1:1which is hardly enough fuel to compensate for the forced air... so if i had a turbocharger at 5 PSI wastegate...the FPR will prob be kicking 70 PSI of fuel (55 idle + 10 for 0 level = 65 ...5 PSI + 1:1 = 5 PSI + 65 = 70).
a normal FPR and adj. FPR are the same thing in mechanicle instance's....its just you can manualy adjust the set PSI for idle for your fuel to start at...like the above example it was 55 PSI.
Lets start over...
What is an FPR?
An FPR, or Fuel Pressure Regulator, is a device that regulates the fuel pressure going to the injectors. This changes with the amount of vacuum from full vacuum (low pressure in the rail) to zero vacuum (higher pressure in the rail). An adjustable FPR allows you to adjust the amount of fuel pressure at idle via a set screw usually on the top of the FPR.
What is an FPR Used For?
When you buy bigger injectors, you need to take some of the fuel at idle out, otherwise there will be too much fuel going into your engine when you are not in boost. This is needed to maintain a consistant idle.
What is an FMU?
An FMU compliments an FPR in a turbocharged or supercharged motor. An FPR only adjusts fuel up to 0psi and maintains a certain pressure. The FMU will take over where the FPR stops and increase fuel in relation to boost. FMU's usually come in either an adjustable version, or a fixed rate version, usually with discs to adjust the pressure.
What is an FMU Used For?
You use an FMU in a boost environment to increase fuel in relation to boost. For example, if you have a 6:1 FMU, the FMU will increase the PSI in the fuel rail 6psi for each 1 psi of boost. So if you have the FPR set at 50 PSI at WOT, running 10 PSI of boost, and a 6:1 FMU, your fuel pressure will effectively be 110 PSI in the rail. This is why fixed rate 12:1 FMU's are bad, they will increase the pressure so much that either the pump will cut out, or the fuel injectors will clip. Always buy an adjustable FMU.
What is the problem with FMU's
The problem with FMU's, and why they shouldn't be used alone, is that they deliver the same amount of fuel at 3000 RPM's as they do at 6500 RPM's. Engines need differering amounts of fuel at different power levels, based on a dyno graph.
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I understand this but my question was rather how comes that somes use Fmu (at least 4:1) and others use a afrp (1:1)
1:1 seems to be far from enough no?? if not those with 4:1 and even more must be a lot too rich ? got my line of thoughts?
You need BOTH. An AFPR will not adjust for boost, an AFPR is ONLY to adjust the pressure at idle. Those who only use an AFPR are not doing it correctly. You could use an AFPR + SAFC, , but not an AFPR alone, thats asking for a blown motor or a car that runs like trash...
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yes but if afpr doesn't take care of the boost and safc doesn't take care too who cares ?
pressure must be increased in the fuel rail for each psi of boost and according to what I read an afpr is 1:1 ratio so it's probably not enough... that is what I can't understand
I'm sorry for having troubles understanding but it's because some tell me a thing and another one tells me the oposite ...
Shifted you told me that we need a Fmu but why did you told me that we can use : Afpr + Safc ??
as far as I know (not very far
) Safc don't detect boost so ... kinda confusing .. :S
just want to know how some only use a S-afc and a Afpr without a Fmu which seems to be essential
Because the SAFC adjust based on RPM. If you know you have X HP at Y rpm, you can figure out if you are lean/rich at that RPM and add or remove fuel. The amount of fuel you need has nothing to do with boost, and everything to do with horsepower.
So if you know you are running lean at 3100 RPM, you can add fuel with the SAFC to compensate, if you are rich at 5200, you can take some out.
Thats how people do it. I prefer to use all 3, so I can set my base pressure, use the FMU to increase pressure in relation to boost, and from there and a dyno trip, I can use the SAFC to fine tune the fuel at particular RPMs.
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becuase it works for them...and possibly there not boost and have helly bolt on mods where they need the extra fuel. For us boosted people we could use i guess a Adj. FPR with only a SAFC...if your useing huge injectors maybe and spend many of Dyno hours tuning it per 200-500 RPM incremeints.
For boosted cars...FMUs help out alot with a SAFC. Most people run them hand and hand. Some dont use a SAFC...like me atm, i only have a cartech FMU with 30lb injectors and a adj. FPR with a intank walbro on 5 PSI of boost and run 11.8:1 A/F and around redline i start to lean out to about 12.8:1...but i plan on getting a SAFC when i get intercooled and 2.5 exhaust to help out that slight leaning out at the top end of my RPM range.
and can't you use your s-afc instead of the afpr ... I mean tuning the S-afc to have the appropriate fuel you need at idle ?
