FMU Question.
 

Well got the Turbo runing fine.
As long as there is gas in the carb bowl she is shreding up her rubbers.
But then the float bowl goes dry and she stalls.

Yeah I know you guys hate FMUs and all that.
But this is a carbed setup so no other option.

Keeping that in mind.
What would be my best FMU the market seems to be flooded with total crap. Its hard to make a call.

Re: FMU Question.
 

best FMU... theres no such thing :P

but i guess the vortech FMU is ok. they have been around for a while, and seem to be the one of choice in premade turbo kit.

Re: FMU Question.
 

Will a FMU even work on a carb setup? Sounds like you need a bigger fuel pump.

Re: FMU Question.
 

i am pretty sure you re jet the carb to add more fuel. a fmu will probably trash the carb since the stock fuel pressure is like 4-6 psi

Re: FMU Question.
 

Not that I claim to be an expert on carb setups, but if I remember correctly, there is no return fuel line. ;)

...don't know how you'd get an FMU to work..

Re: FMU Question.
 

Thanks CRX2fast that was the kind of info I was looking for.

Guys on a carbed setup its obvious your going to need a fuel pump with a higer PSI rating than the boost your runing or the car will ---- out. Every time you hit boost.

My present setup.
A new fuel pump in the tank from an EFI car which makes 65 PSI.
This is connected to my home built FMU which is nothing but a modifed fuel regulator found at the end of fuel rail. Its cut up and setup so that manifold presure is connected to a nipple on top of it. THe spring is replaced with a softer spring. It has a new return line laid back to the tank.
How its suposed to work is under no boost it will supply 5 PSI to the carb. THe rest of the fuel is returned to the tank.
As it sees boost it will press down on the spring releasing more fuel flow from the pump. Towards the carb. The carb uses how much fuel it needs and the excess fuel is returned back to the tank via the fuel return line.
Yes I know it sounds stupid but we do have two fuel return lines. I could have just used the existing fuel return line.
TOday need to strip down the setup and chk if its the fuel pump or my FMU thats acting up. We have another car with the same setup runing fine.
If its my FMU may as well just get something that works out of the box.

We are adding our own ECU which is a wide band sensor runing closed loop to a single injector under the carb. So far Ive only finished the WB o2 circuit. Now just need to add injecotr and ignition circuit. If I can find a knock sensor at the junk yard we will do a circuit for that too. Ignition is allready working. O2 done. So only the injecotr setup left. Yes I know about megasquirt but I want to do our own Getho setup. Copying some other guys design isnt as much fun some how.

So man Ill hit egay and chk for Vortech.

Re: FMU Question.
 

I think you need to post some pics of this setup, sounds cool 8)

Re: FMU Question.
 

Ditto, this sounds very unique and cool....we like that sort of ---- around here :)
:D

Re: FMU Question.
 

listen to TurboEF9. that guy is smart, i think

Re: FMU Question.
 

He seems to have it "worked out", however, I would like to see how well the floats work under that amount of fuel pressure.

Especially with the FMU pushing out between 8 - 12 psi on top of that per psi of boost... will be interesting to see how this works out.

Re: FMU Question.
 

Carbs aren't designed for high pressure. Some tolerate ~15 psi base pressure, but that's about it.

You want to get a 1:1 FMU, several places make them, to allow the fuel pressure to overcome intake manifold pressure as it rises under boost. What are you doing to seal the carb up so it doesn't leak? Did you build a carb box, or seal the shafts, etc? Do you have brass or filled floats?

You can also run a stock mechanical fuel pump with the top drilled out to fit a nipple, and boost referrenced. Worked for Sitar's 680whp with slicks spinning on the dyno rollers junkyard 351W build. He also used an EFI fuel pump and a Hobbs switch to spray a little extra fuel into the carb throat at 4+ psig. www.toohighpsi.com has the writeup.

Got anymore details on your setup? If I don't know it, I can provide an intro to someone who has hands on experience.

Re: FMU Question.
 

Well made some progress. The smoke problem has gone away totally.
The turbo is working really well too. Its poping my waste gate if bliped in Neutral. Something that dosent happen on the first car we did. THere the engine has to be in gear / underload to see any kind of boost.

This got me thinking maybe my hybrid exhaust hosuing is too small. And it would choke top end flow. So did a few 2nd and 3d gear pulls. WIth the Gtech RR hooked up. She is pulling clean to 7500 RPM (Stock is 6500). Stock rubber is 155 now runing 175 and shes shreding even these.

Buttttttt :P

Sometimes she will start jerking like crazy. / Fuel starvation.
Ok so why is the first car working fine and this one not. First doubt the DIY FMU.
So replace all the hoses with see thru tubes.
1. Fuel pump to FMU
2. FMU return line
3. FMU to Carb
4. FMU to Extra dial a jet / adjustable power jet
5. FMU to Carb
6. Carbs orignal return line

Take off the hood and take it for a spin.

No boost. Fuel is returning thru FMU return line and carb return line.
As boost climbs fuel in the return line starts to slow down. At 14 PSI the FMU fuel return line is totally dry.
Cant see any of the carb tubes.

What info do you need. The only thing Ive not mentioned above is that I have something called Adjustable powerjet / dial a jet hooked up. THe FMU out is has a T one goes to this extra jet the other to the carb. THe adjustable jet is setup so that no boost = no flow. As boost croses 4psi and starts to climb it flows a little.
How did we achive this. Just close and then back off a fraction.

We havent done anything to seal the carbs. THe shafts have inbuilt rubber seals from the company. I couldnt belive it either but the thing works fine. With no leaks what so ever.
So fine in fact. That we have been out racing cars with much larger engine capacites and many fancy toys like fancy cams, ecus, and others toys that cost more than our car.
Ive allready posted pics from our first install. Anyway they are here.
http://www.eindiancompanies.com/turbo/
And of the Drag race http://www.eindiancompanies.com/drag/
See esteem vs Baleno

Pics of my own setup Ill post in a day or two.

Everywhere I see the refrence to you need a 1:1 FMU what is this.
Is this diffirent from a Vortech type setup. If so can you provide some more info.
Or on how it works so I can build one or buy one.

Re: FMU Question.
 

1:1 FMU is equivalent to a factory fuel injected car's stock fuel pressure regulator. I know you can get them out of Summit's catalog.

Normal FMUs work to raise pressure by blocking fuel return to the tank. With a low pressure carby setup, that might not work so hot because the stock pump can only push out so much. At low boost I can see a possibility of the bowl being overfilled and the fuel return being dry, and at high boost I can see where the stock pump totally can't keep up and it runs out of fuel. Just a mental picture and maybe not anything you have going on.

Check toohighpsi.com and see how Sitar modified the stock 351W truck fuel pump, I really think doing that to your fuel system is what you need to do, then fiddle with jetting until you're running perfectly.

155/175 tires? What car is this, anyway? I get the feeling it's not the domestic V8 muscle I'm used to seeing with a blow through carb.

Re: FMU Question.
 

As allready mentioned at the start of this post we are using a EFI fuel pump that was puting out 65 PSI when we installed it.

Most of the replies seem to be by passing this aspect.

Also I still havent understood what a 1:1 FMU is. Is it something that boosts the fuel flow by 1:1 i.e. for every increase in boost it would boost fuel presure by 1 psi

Anyway I think we are close to dialing it in we still have one hitch but maybe a one way valve will fix it.

Latest test results.
Presure before FMU 30 PSI (THe pump we tested at 65psi has gone down to 30 psi).
Presure at FMU exit with no boost 4 psi. Therefore Carb inlet 4 psi
Boost taken up to 10 PSI at 10 PSI boost. Fuel presure being output by FMU is 9 PSI. This means the engine is at redline. ANd flowing fuel and there is still 9 PSI at the inlet.
Which means we can take the boost up to 16 PSI and we would still have 3 PSI at the carb inlet.
Both return lines are kept seprate. i.e. return line from FMU and Return line from the carb.
I have one doubt though. The FMU exit hole is 1.8mm dia. My carb jet dia is say 3mm should I leave it as it is.
What would the effect of changing the FMU exit hole be. i.e. Im thinking of making the exit size larger i.e. match it to my jet size. i.e. 3mm so will the pressure go up or down. Im afraid it will go down.

The problem is when the car starts moving i.e. no boost just starting to move it starts jerking like fuel starvation.
Two problems could be causeing this
1. The line to the FMU is seeing a vacum and pulling shut the FMU killing flow.
2. WHen I turn the Ign on. I can hear the fuel pump whine then there is a click from under the dash and the fuel pump goes off. On the other car the fuel pump never goes off. (We asume the fuel pump starts up again when the engine is runing). But by then its playing catch up. What we did was remove the stock fuel pump and put in the MPFI pump in the same position in the tank. ANd hooked up using the same wires.
Pics of the setup have allready been posted. On another thread.

Re: FMU Question.
 

I just thought Id post an update on this.

We solved the problem. What was hapening was when accelrating the line to the FMU would see a strong suction this would pull shut the FMU and stop flow to the carb. What I did was install a one way valve on the FMU signal line. So the FMU would flow its 4 PSI when not under boost and not see vacum but when under boost it would see pressure and allow flow.
Another thing we did was connect the power supply line of the fuel pump direct so now if it the ign is switched on the pump is runing it never cuts out.

THe car is runing fine now.
We took it for a spin and have even sampled 16 PSI boost with no problems.

Im still keen to save up some money and buy a Vortech FMU some day. And am keeping a look out on egay. Just not sure about this 1:1 business and what FMU I should get.