This may cause a bit of a hornet's nest, but the Cartech FMU has been insulted since it was included in certain aftermarket turbo kits. The complaints that are usually heard relate to the lack of a rock solid idle fuel pressure. I feel that this is due to the Cartech being a Fuel Pressure Riser, and not a regulator.

From the Cartech FMU install webpage, found here:

http://www.cartech.net/fmu2020instruc.htm

The first paragraph states the following:


General Information
1.) The rising rate regulators fit into the fuel system after the stock regulator, and in series with it. The regulator becomes the last item before the fuel returns to the tank. Do not remove the stock regulator, as it still controls the fuel flow under most manifold vacuum conditions.



It is clearly stated that the Cartech is not meant to regulate fuel pressure in idle conditions or vacuum conditions. There is no good starting point for pressure tuning when the fuel pressure fluctuates.

It is also known that the Chrysler ECU does not rely on fuel pressure being varied with manifold pressure (or vacuum). In order to work properly, the fuel pressure should be kept at a constant (albeit lower) pressure in vacuum.

Since using the stock regulator with larger then stock injectors is ill advised, I feel that the best way to do this would be to add an Aeromotive or SPX fuel pressure regulator between the fuel rail and the Cartech in the fuel return line. Do not reference this to manifold pressure. This will emmulate the stock regulator, holding a fixed PSI in the rail. Once the manifold goes into positive pressure, the Cartech will kick in and do it's job.

The Cartech is a nice piece, being designed by Corky Bell's (of "Maximum Boost" fame) company (Cartech). If used properly, it should provide trouble free fuel pressure rising. I, myself, will be using an Aeromotive with the Cartech.

So, use the Cartech as it is designed, and place blame where blame belongs.


-=B-=

You're wrong. The cartech has provisions to control a set "idle" or "static" fuel pressure. If it didn't, it would not be used in such a function.

Just because it does what it is designed to do badly does not mean that it wasn't supposed to do it. if that were the case, they'd sell it like a Vortech FMU with no base pressure adjustment at all.

Discuss.

That's not what Mike from Cartech said.

Not to be obstinate, but I think that the Cartech should have been marketed in the same way that STAR did with the FMU. Else, don't tell people to remove the stock regulator if stock injectors are being used.

Which brings up another problem I have with fuel pressure tuning on a 420a... the PCM controls the injectors as they would be controlled with a static fuel pressure. While in vacuum, the pressure is pulled below static fuel pressure. Our PCM understands that the idle fuel pressure will be the same as the static fuel pressure, and so forth and so on, but that's another discussion, I think.

-=B-=

95's stock FPR use vacuum to change FP. 96+ with the FPR by the tank static FP all the time.

Well, I was referring to the later fuel system. :P
-=B-=

so would the cartech work alright with a 95?
doug

I like the Cartech's ability to adjust the fuel pessure as I need it. The problem with the Cartech not holding static fuel pressure has to do with the diaphram located inside of it, this controls the fuel pressure and it changes with temp, etc. The one that comes in the cartech unit isn't all that great. When my kit arrived from HRC I took the Cartech unit to a friend of mine and had him "rebuild" with a better diaphram. I have very little problems with the Cartech unit. I only need to adjust the fuel pressure when the tempture changes dramatically. I'll set it at the begining of summer, then when winter finnally gets here to stay, I'll adjust it again. No big deal for me, just a quick adjustment. Yeah, it would be nice I suppose to get the Vortech FMU and just never have to play with again but I think too many people sometimes want a turbo kit without having to ever pop the hood and check on or adjust things. I dont mind having the adjust the Cartech 4 or 5 times a year and its so easy to adjust the fuel pressure to your likeing. Several local guys I know are 2.4 block fully race built and still using a rebuilt Cartech so its really not all that bad.

I really tried to use that fpr. It was driving me nuts, I literally had to adjust the static every time I started the car. It made a nice paper weight and went for a few bucks on ebay. Mabye thier is a faulty part or something causing premature wear on the diaphram. :shrug

Its my belief that the diaphram is flawed, at least for what we use it for. When I start the car up in the morning, especially on COLD mornings FP is about 5psi or so higher then it normally is, if I go down the road about 5mins or so and check it again, its where it should be. No big deal for me, and having it rebuilt was cheaper then buying the Vortch so as long is it still works....hey why change it?

I've heard that before Bill, and perhaps much of the blame should be HRC's for using this FPR in a place it shouldn't.

However, from my experiences with his FPR, not ONLY did it operate eratically during idle operation, it was also disfunctional during boost. After I initially set the fuel ratio to where I needed it at the initial outset of tuning, so many years ago, after making various alterations to the fuel system, I needed to reset it to another fuel ratio. Suffice it to say, I couldn't adjust it any longer.

I agree with the aforementioned post in regard to the diaphram. As I discovered long ago through using the Voretech SFMU, the big difference is in the diaphrams! Cartech's diaphram is a cheap poopy rubber one, and Vortech's is some sort of advanced rubber/synthetic one. For some reason, Cartech's diaphram loses its pliability whereas the Vortech's retains its ability to change shape, per your setting.

yep, its all about the diaphrams. Change it out and your good to go.

HRC always claims that the problems with cartech FPR's are related to faulty use by the user. I took most of my time installing the fuel system, almost as much as the rest of the kit. I went over it time and time again as per the instructions. As a result, I have had very little problems with it and have had to adjust it just a few times. I do have plans to upgrade to the Vortech when the diaphram goes bad, but in the meantime - I'm content.

either way.. i haven't had to touch the vortech unit since i initially tuned the car back in april. since then it's gotten very hot (100's) and now it's very cold (20's) fuel trims have barely changed and th fp is dead on still. so i dunno, i never really messed w/ the cartech unit, but regardless anything that's had this many problems (even if they are user related) needs some revising as far as it's application. assuming that it's not just a faulty design.

I installed a vortech diaphragm, and my own shim in the Cartech billet FPR, and it at least worked better under boost. Still fluctuated a little though. :thumbsdown

Mark me down as a HRC kit Cartech basher, it cost me and countless others a couple pistons at best.

Originally posted by thedawg
Mark me down as a HRC kit Cartech basher, it cost me and countless others a couple pistons at best.

word to that dan....ive had issues first hand, so thats enough for me to hate it

its a reg that doesnt regulate....aka, peice of shit. nuff said.



_________
96 talon esi-t
san clemente, ca

DarkOne> Screw you guys, i'm going home.
chrysler kid> and fyi i have never HAD to shave.
DR1665> I'm sure your Talon and my Talon are all there needs to be, since we're the only two Talons that really matter around here

Originally posted by sarahdr1665
...some girls like the "nerdy" guys

Actually the Cartech is a great item...




















To use as a SHOTPUT:


or, alternately to POOP ON:

^^^^lmao


*that* ladies and gentlemen is EXACTLY what the cartech was designed for



_________
96 talon esi-t
san clemente, ca

DarkOne> Screw you guys, i'm going home.
chrysler kid> and fyi i have never HAD to shave.
DR1665> I'm sure your Talon and my Talon are all there needs to be, since we're the only two Talons that really matter around here

Originally posted by sarahdr1665
...some girls like the "nerdy" guys

Originally posted by thedawg
Actually the Cartech is a great item... To use as a SHOTPUT: or, alternately to POOP ON:

^^LOL


-------jezreel
hrc stage 1, sfmu, ml, prokits, egt, boost gauge, apexi tt, costum dp, dynotune fp gauge. gst muff, turbo spoiler

nothing like driving with the windows down and the music low: i love hearing the turbo spool, swwwhhhttt!!!!
thanks for www.kaptainmyke.com for the sig hosting :thumbsup

Cartech is crap buy a Chill Factory regulator:P
:cheers :cheers