Hey..turbo project questions

[c2xejk]

When you run a FMU and larger injectors, you generally turn the base pressure down. The FMU then brings the pressure up when you are in boost. So when you are not in boost, you theoretically stock amount of fuel being delivered.

How high the fuel pressure goes depends on several factors. How much boost, FMU ratio, fuel pump capability, etc. As for the pressure effects on spray pattern, depends on the injector. A 2.2L turbo engine runs at 55psi base pressure and 12+ psi... Or 67psi fuel pressure, stock...

[NA2ndgen]

yeah ... learned a little more ... thanks ed

[c2xejk]

There are some injectors (Ford TBI??) that don't respond well to high fuel pressure... Seems to me somebody tested a Ford TBI injector and over 45 psi, fuel flow went down. I think that had to do with how that particular injector works. That has not proven to be true at for our injectors or the Ford 5L multi-port injectors (atleast the aftermarket ones like Stein currently runs...)

[Urban_S]

Sorry the fmu is new to me. Wouldent you need to drop the base pressure in the stock fpr? Or are you removing it?

[c2xejk]

The FPR (or AFPR) controlls the "base" fuel pressure. ie. the fuel pressure relative to atmospheric. So at 1 psi of vacuum, the fuel pressure would be base pressure - 1 psi. So if you set the base at 35psi, then it would be 34psi. At 1 psi of boost, the fuel pressure (FP) would be 36psi.

The FMU is strictly relative to boost. So 0 boost, it is trying to move FP to 0 psi. At 1psi vacuum, it is tring to move the FP to 0 psi. When you get into the boost, is when things get interesting. If you have say a 10:1 FMU and you have 1psi of boost, then the FMU is trying to regulate FP to 10psi...

Now since 10 psi < 36psi, the FP will be 36psi. To figure out when the meet, you can solve the following equation:

35 + x = 10* x
or x = 35/9 aka 3.9psi.

An quick examination of the equation tells you that if you lower the base pressure, the onset boost level is lower... There are limits to how low you can go and get a good spray pattern... There can also be limits on how low you can turn down the base pressure because of the fuel pump... (there are ways to deal with that problem too...)

Anyway, the FMU and FPR/AFPR are both part of a large system that must be tuned... On Stein I also run cold start injectors... The cold starts plug the low and high psi holes in the fueling...

Once I slow the fuel pump, I may be able to turn the base pressure down and eliminate the low psi cold start...

[Urban_S]

So basicly to get a decent set up I should get a fmu and afpr(so I can lower the base psi. I am tempted to get out a SAFCII and a afpr. So what ratio would you suggest for a stock pump, 450cc injectors. 10psi from a bullseye 50-1 trim?

[mwinkle353]

universal adjustable fuel pressure regulator
adjustable rising rate fuel pressure regulator
larger injectors
SAFC (or alike)

that's basically all you'll need to get your fuel system where you need it, if you don't use a stand alone ecu.

The ratio won't be dependant on your pump. It's dependant on your injectors and boost goals.

50-1 trim? Never heard of that turbo before. Unless you meant a T04E 50 trim Stage I? And if you're going with a bullseye turbo, you're wasting your money. You can get the same quality of turbo for much less. You just have to shop around and know what you're looking at.

[Urban_S]

I was kicking around the idea of pulling it off my eclipse. I will most likely use my evo 3 16g that is sitting on my desk. I am not wanting much more power just some boost. So even with s arrfpr I would still need a safc? In the past I have just used a fpr and safc. So stand alone like(mega squirt)? Thats overkill for what I really need.
Shopping list:
Manifold
OBX FMU
OBX afpr
safc

[mwinkle353]

well, let me tell it to you like this. There are two guys running the "Chrysler Prototype" 3.0L turbo setups in their cars. Neither one is using a SAFC unit on the setup. They're just using larger injectors, adjustable base fuel pressure regulator, and an adjustable rising rate of gain fuel pressure regulator. The one, he's been driving the car like that for the past few years now. Many thousands of miles with no problems, besides on ocaisional transmission thrashing.

Oh, and by the way, that OBX FMU is not a very good choice. I highly recommend using what all the other 3.0L turbo guys have been using. The BEGi units. They have an adjustable rate of gain, plus an adjustable onset of pressure. This way, you don't get the lean condition between the 1-4 psi boost pressures. And it will also prevent being overly rich in the upper boosts as well.

[Urban_S]

Ok I see the fmu is to hit it in the ball park and the safc is for the fine tune. When tuning are you guys using wideband, narrowband, egt, palm loging. I am gessing that megasquirt has a logger as well. Sorry if I seem dumb, its just a kinda new world from me(ie not v8 n/a power or factory turbo)

[mwinkle353]

The only way to tune is on a dyno using a wideband O2 setup. An EGT is a good gauge to have as well. It can better tweak your ignition if your Air/fuel seems to be on spot.

[Urban_S]

I wish they had something like dsmlink for these cars. With that and my aem wideband it was sweet. Dyno tuning is not the only way but just the best way.

[mwinkle353]

Quote:

Originally Posted by Urban_S I wish they had something like dsmlink for these cars. With that and my aem wideband it was sweet. Dyno tuning is not the only way but just the best way.

Yet you knew what I meant.

[NA2ndgen]

Wink would you post your car domain page? I would love to see what you are up to these days. Bet it's great.

[Urban_S]

I have not updated my cardomain page since I bought the car.