Okay so I'm going to turbo my 420 and I'm pretty much planning out all my parts to make this as painless as possible. However, I stumbled onto a question or two.
-When I go turbo, I'll need to buy an FMU (since I don't plan on tuning it, only 8psi stock). I read that it's pretty much a secondary FPR, if so, why can't I just buy an aftermarket FPR and set the fuel pressure myself and call it a day?
Numero 2
-Fuel cut defender. Is this necessary? Isn't that what missing link is for?
#109504, "RE: FMU vs FPR" In response to Reply # 0
Because the FMU you are speaking of is a rising rate regulator. It compensates for positive manifold pressure by dramatically increasing the rail pressure.
An adjustable FPR such as an aeromotive unit is not a rising rate and will not work in the application you are intending.
#109505, "RE: FMU vs FPR" In response to Reply # 1 Sep-19-12 10:57 AM by xcasbonx
An adjustable FPR such as an aeromotive unit is not a rising rate and will not work in the application you are intending.
Technically any AFPR that you put on a boosted car should be a rise rate reg. Most aeromotive units are rise rate but only a 1:1 rate. You need a 12:1 rise rate to run stock injectors and I wouldnt even try to run 8psi on them.
That is the crappiest fuel system you can use, spend a little bit more money on a SFMU and slightly larger injectors. This will give you much lower fuel pressures and an overall better fuel system.
#109508, "RE: FMU vs FPR" In response to Reply # 4
Originally posted by Rtistyk Thanks guys that clears it up big time. Would it be better to run a set of 450cc's and go to maybe a 10:1 FMU? Oh and I don't think anyone saw the FCD question. Are any of you running FCD, and is it necessary?
You need a FCD or equivalent if you have a 96+, though I've seen it on 95s too (not sure why).
Honestly I hate my SFMU/440 setup. I just don't want to put the dime down for portfueler...
2gnt: '99 RS-T, killed by a toyota, pending rebuild... Daily: Volt Daily #2: '99 EVG ebike- STOLEN by PEDRO
#109509, "RE: FMU vs FPR" In response to Reply # 5
Be honest with yourself, are you really only going for an 8 psi setup? Eventually your gonna get use to 8psi and want more. Annie up and get the 1:1 rising rate and your wallet will thank you down the road.
#109511, "RE: FMU vs FPR" In response to Reply # 7 Sep-20-12 09:09 PM by Rtistyk
I'm going to build a 2.4 using the early Chrysler non srt bottom end. That's going to be the slow build, I have almost all the valve train built and assembled just need to find a nice short block.
However, I need to go turbo, I live in a very hilly area and going up hills with no torque really sucks to be honest lol. I have all the N/T mods you can possible do, except a built motor. I'm just looking to boost it for now, it's really only a DD right now, not a week-end warrior, YET!
@JoshDSM can you link me the afpr that your buddy has? Though I don't feel it will be safe to run on a 10PSI stock block without a tune, I'll probably stick with 6 or 8.
@ez, fun fact, this car actually used to be boosted and had a portfueler along with an 8 injector setup. Was making good power but shot a rod through the block after only so much abuse. The guy then swapped in a stock 420a and sold it to me.
This car still has the Wally 255 in it and it wines like a mother f! It's about time I compensate with injectors and boost.
e: and just to clarify, I'll need FCD even if I get Missing Link?
#109512, "RE: FMU vs FPR" In response to Reply # 8
Originally posted by Rtistyk e: and just to clarify, I'll need FCD even if I get Missing Link?
No, remember these both serve to prevent the ECU from seeing too high a voltage. This is just based on what I remember, b/c I never used either of them - instead I use an E-manage which intercepts the voltage and clamps it below the threshold that causes stuttering.
2gnt: '99 RS-T, killed by a toyota, pending rebuild... Daily: Volt Daily #2: '99 EVG ebike- STOLEN by PEDRO
#109513, "RE: FMU vs FPR" In response to Reply # 9
You WILL have to run some type of rise rate regulator even with larger injectors. Running 450s and a 1:1 AFPR is not going to cut it. If you run larger injectors you will either have to turn down the base pressure or use some type of fuel controller to compensate for them.
I had good luck running a SFMU along with some 310cc injectors. Also upgraded to 440s and ran up with 18psi once the motor was built
