Fuel system set up for boost, is this right?? Pic
 

This is going to be for a blower box blow thru pro charged set up.I have done a few systems on fuel injection engines, but none for a carb, so if I come off ignorant, please bare with me.. From my understanding I will need to add a return line to the system, correct?? Next is I need a boost reference FPR that will have to be able to be set higher then the boost level, correct?? I plan to use a electric inline bosch FP that is good for the HP were are shooting for 6xx, as I have one that is not being used, see no need to run a huge A1000 pump.. Going to use a #8 feed, #6 return.. This is the way I plan to do the set up.. WILL THIS SUFFICE... Thanks guys


John jr

This is just a quick sketch up..

Check out this link sir....it may give you a little better understanding. :drink:

http://www.holley.com/data/TechServi...ech%20Info.pdf

Thanks for that link, based on it, I should be good to go, but did not see anything in there as far as carb'd-boost ref FPR's.. :D

John jr

If I remember correctly (and someone please correct anything I am wrong about), it's the carbs that are boost referenced....not the FPR. Blower carbs have special power valves in them (I think), and the vacuum lines just go to a port in the manifold. I dont think you absolutely NEED a special FPR for your setup. You just need to make sure you have plenty of VOLUME sir. :drink:

Hmmm.. Never heard of that.. I just did a skim over on some blower tuning on a few diff sites, it did not mention this about the carb itself being boost ref, just that being in a box( pressurize, will require solid floats so they will not collapse under boost.. WTH is one of the blower guys when we need them... LOL Ot atleast carbed guys.. Fuel injection seems so much easier some time hahaha


John jr

The reason you want to run a boost referenced regulator, is because of the fact it is a "Blow Thru" setup. In a roots style setup, the carb has atmospheric pressure above it. But, with a "blow thru" setup like a procharger, you will have more psi on top of the carb. As boost goes up, you need to increase the fuel psi, to keep the needle and seats/floats from closing and shutting down fuel supply while under boost, due to the added psi on top of the bowl vents.

I believe the general rule of thumb is 1 psi of fuel psi increase, for every 1 psi of boost. So if you are say at 7psi at idle, and setup to run 7psi wot, you want 14psi at wot on your gauge. Keep in mind, I am no expert on any of this, and some may be able to give you some better info you can take to the bank! :drink:

I would also run a regulator with a bypass.

Contact Nickerson Performance for carb set-up on the blow thru box application.

Yes, return line to tank and boost referenced fuel pressure regulator are needed. You will probably set for 7lbs fuel pressure at idle, then add 1 lb. of fuel pressure for each pound of boost- controlled through your pressure line between box and regulator. Just need to be sure your fuel pump will provide the additional lbs. of fuel pressure under boost.

this is absolutly correct,u need to increase the fuel pressure pound for pound.

Ok that has cleared up some things. I am aware of the fuel pressure per boost PSI because of the blow through/box app. I just wanted to know if that sketch i whipped up would work.. Thanks for all the input...


John jr

unless you are blocking the pv's off I would run boost reference power valves as well as a boost reference fp regulator. it takes a little time but this set up can be tuned to idle around the dock as well as run wide open. make sure you have enough pump to supply enough base fuel psi and 1 pound of fuel per 1 pound of boost. I have a lot of experience with the blow through stuff on both cars and boats and it does and will work if set up properly.

Thank you.. The carb will most def be done by somebody who is FAMILIAR doing these style carbs.. The pump shouldn't be a problem( big bosch pump) My main concern was with the way I had the pic drawn up.. Just wanted to be sure it will work this way before we start gather parts and all.. I still run a vacuum line into the blower box/ intake manifold, not to the carb itself, or can it be done any one of them ways..


John jr

Well...I guess I was sorta right (my setup was for a traditional blower)...lol. :rolleyes:

I always ran c and s specialties carbs. I made 1249 rwhp with an 8.2 deck height sbf with a 106 mm turbo with one of their carbs the car was occasionally street driven and ran 5.0's in the eighth on 325 radials. all of his was done with no intercooler. the way that you have drawn the fuel system will work but are you running the procharger carb box or a hat on the carb? how much boost do you plan on making?
this may help you in making sure that you have enough pump.

First, you'll need to calculate how much pressure you need. You'll need to know a few things first: 1) Max boost you plan on running, and 2) Regulator type. Why does the regulator type matter? Because if you are using a dead-head style regulator, you must have an additional pressure differential across the regulating orifice to be able to control fuel pressure. Generally, this will need to be 10-15 psi. If you’re running a bypass or return style regulator, you will not need this extra pressure, because the regulating orifice is on the return side of the system. There will also be losses in the system from fuel lines and fittings, as well as acceleration losses. You’ll need more pressure at the pump to account for these losses. You can generally assume these losses to be around 5 psi. If there are a lot of bends in the system, your losses may be more. With these things in mind, let’s calculate how much pressure we need.




P = (base fuel pressure) + (boost pressure) + (line losses) + (10-15 psi if running a dead head regulator)




So, for a blowthrough engine with a bypass regulator making 20 psi boost and a base fuel pressure of 7 psi we have:




P = 7psi + 20psi + 5psi = 32 psi





If we ran a dead-head regulator, we would need 10-15 psi more than that to have adjustability at the regulator. So if we run a bypass regulator, we’ll need 32 psi and if we run a dead-head regulator, we’ll need at least 42 psi. Now lets figure out how much fuel flow we’ll need.

How much fuel we need will be dictated by how much Horsepower we plan on making. In our case, lets say we are shooting for an even 1000 Hp. This number needs to be the Hp at the crank. At this point, I need to introduce some IC engine fundamentals. Every engine has what is called a BSFC, or Brake Specific Fuel Consumption. This number is the amount of fuel it takes, in pounds, to support 1 Hp for 1 Hour. The units for this number is (lbs/hr)/Hp. For a naturally aspirated engine, the BSFC will be around .45-.55 (lbs/hr)/Hp. For a turbocharged engine it will be around .55-.6 (lbs/hr)/Hp. A supercharged engine will be around .6-.65 (lbs/hr)/Hp because of the added Hp it takes to spin the supercharger.

To determine how much flow we need, we simply take our target Horsepower and multiply it by the corresponding BSFC. I generally use the high end of the scale just to get a conservative estimate. So, for our 1000 Hp turbocharged engine we have:




Fuel required = (target Hp) * (BSFC)

Fuel required = 1000 Hp * .6 (lbs/hr)/Hp = 600 lbs/hr



Note: Many fuel injection pumps use lbs/hr as a measure of flow. If you want to know the flow in gal/hr, simply divide the lbs/hr figure by 6, since gasoline weighs about 6 lbs/gal.

At this point, we need a pump that flows 600 lbs/hr (or 100 gal/hr) at 32 psi with a return style regulator or a minimum of 42 psi with a dead-head regulator. Now we need to start looking at fuel pump performance curves to see what they flow at specific pressures. For example, If you look at the flow curve for the Aeromotive A1000 pump below, we can see that at 32 psi the pump flows ~600 lbs/hr at +12V. This pump would work on a system with a bypass regulator. However, at 42 psi, the pump only flows ~550 lbs/hr, which is not quite enough at +12V for a dead-head setup. The pump will work for either system at +13.5V, but you would need to be sure the pump was running at 13.5 volts at WOT, which may not be possible if you’re running a lot of electrical accessories, like electric fans, electric water pump, fuel pumps, etc. It’s best to err on the side of caution with fuel systems, so if you were to run a dead-head regulator, a larger pump would be in order.

Your sketch should work fine. I would lose the red and yellow fuel lines though. not uscg approved. :party-smiley-004:

Thank you, still app your input... :coolcowboy:

:D yah I kinda thought it might be a issue with them too..

THANK YOU..

As in bypass regulator you are referring to a return( fuel return line out of the reg)??? excellent info.. The fuel pump used will be a bosch pump, will flow ruffly 75gph.. Boost will be 12-14 psi.. The fuel line routing it self will be a pretty strait shot, with the only fittings going into the reg, then out then into the box, then Y into each side of the carb...

John jr

75 gph ????? Thats gotta be a typo. :eek:

Is that not enough??? I am using this same pump on my vehicle, it makes well into the 5xx whp range?? Does a crab'd set up need that much more pump over a fuel injected set up???


John jr

not sure about the bosch pump, I run the aeromotive A1000 pump, their regulator that is boost referenced for that pump, #10 line from tank, thru fram H/P filter, regulator, #6 lines to box, #8 return as speced by aeromotive, my carb is a 950 from prosystems, the regulator increases fuel pressure 1lb for each psi of boost...vacume line to carb box

I still run a vacuum line into the blower box/ intake manifold, not to the carb itself, or can it be done any one of them ways..

The vacuum line MJSTcome from the Box. The box willl generally have approx 3 more lbs boost than the intake.

Ok so now does it being a carb require more fuel flow then a injector set up??

John jr

not really but thats not enough pump. I would run an a 1000 if it was mine. starve it for fuel and it wont last very long lol.

Hmmmm, intersting... Guess I will have to look into a bigger pump.. Like I said these pumps are good for 700 hp. At least that is what it says per the site..

Thanks :coolcowboy:

John jr

fixx
 

you will also need rear notched floats and rear jet extensions,,under boost the fuel will be pushed to the rear rear float bowl,when this happens the rear jets will get air instead of fuel,the jet extensions keep the jets in the bowl of fuel..

you will need a minimum of 150 gph fuel pump to keep everything wet in the fuel system for a pro charged application, aeromotive a1000 or a sx performance 18201 will put out plenty of fuel for your needs..i would also use a -10 to supply from the fuel tank to the pump then to the regulator then step down from their..

C&S specialties makes a aerosol carb that would work the best for your application..They rock!:drink:

if you decide to use your existing carburetor its best to run a annular type booster,this booster idolises the fuel better under boost,a standard booster will have a chitty throttle response..you will also have to modify the metering blocks were the pv's are,they can only flow so much fuel and the two little holes going to the jets will need to be opened accordingly to the jet size used..First jet the engine fat then lein it out,if your lein on the first run and trust me you will hurt the engine...

Ok thanks.. Like I said the carb is going to be set up by somebody who has done MANY of these, so I am not going to question their ability to do a good carb.. I still am in?? about the size of the fuel pump, line size that you guys are saying needs to be used to achieve/feed 6xx hp.. But am not going to ?? it.. Just seems weird that I am using this pump on a vehicle on STOCK fuel lines 3/8 on 12psi, making well into the 6xx crank HP range, yet need a bigger pump then that to do it on a carbed set up.. Again I am not bringing a argument up, as I did ask the question, truly app the input and info you guys have posted up.. What am I missing though as far as the big fuel lines and huge pump for such little HP??? Thanks again


John jr

well then just run and see....we'll watch and listen..

Cars and boats are not the same. Cars go wot for 10 seconds. Boats go wot for 10 minutes.

not to mention a fuel injected set up has no float bowls to run dry........

Great point, I actually did think about this after posting back up.. Also do you think the stock merc canister fuel filter will give me enough flow,my dad has them on his big Chris Craft and it flows 30 gal hour at least on that big thing.


John jr

ttt

ttt

Stock canister filter should be fine. IF they are 3/8NPT inlets and outlets. Don't be confused by that, as a 3/8 pipe tread female port, is a little bigger than 1/2" in actual size, might even be closer to 5/8, i forget. I dont see a problem going from a 3/8NPT male to a -8an or -10an fuel line. Try to stay away from 90* fittings, if you have to use a 90, use a full flow style 90.

A buddy of mine has a roots blower setup with twin 750 holleys. He has a 140GPH electric pump, plumbed with a stock merc mechanical pump, then a -8an single line feeding a fuel block, that goes to 3/8 hard lines to each bowl. Stock water seperators. I probably would have went with all -10 to the fuel block, but his works.

We can talk about this all day, but in the end, its better to go big or go home. Overkill on a fuel system is a good thing. Basically, if you want a reliable setup, and only want to do it once, start at the tank pickup, and work your way to the carb, elminating any questionable fittings, orifices, lines, etc, that "might" cause a problem.



You can put a fancy big dollar fuel pump in there, but if the tank pickups or anti-siphon valve are restricing it, you'll have problems. You can upgrade the stock fuel filters, with these, they are cheap money in the grand scheme.

http://www.hardin-marine.com/p-13483...nd-outlet.aspx

I also believe, that you can plumb the bypass line from the regulater, back to the filter head. I would check with some of the other guys on that though.

You haven't told us which Bosch pump you are running. You only said it was a big one. We need more info. A quick Google only turns up the 200lph inline style pump. Give us a model number. Big difference if your pump will make 75gph at 5psi versus what it makes at 30 psi. Model number please.

Your boost reference line (the one you labelled vacuum) must tap into the BOX pressure, not the intake manifold. You've mentioned understanding this, but I'm just reiterating it. It's important.

You set the regulator pressure at 7psi with the reference line disconnected, and then you should be good to go once the line is hooked back up. Most all boost ref regulators are 1:1.

If you run your return line back into your fuel tank, then you don't have to worry about a fuel cooler. If you run your return line back to a tee in front of the fuel pump, then you can get the fuel too hot and vapor lock the pump on hot summer days. Your diagram shows that you are returning fuel all the way back to the tank, which is preferred.

You don't show your filter location.
Generally, you want to run the filter before the pump in order to protect it. You can, however, run it between the pump and regulator. DO NOT PUT A FILTER AFTER THE REGULATOR. The carb inlet screen is the only "filter" that should exist between the regulator and the carb.

Does your system flow enough fuel?
Buy a fuel pressure gauge. Tap the line going to the carb. Keep an eye on it. If the pressure stays where it should all the way to extended WOT, then the answer is yes. As filter gets obstructed, though, there is always the chance that it can drop so keep an eye on it.

MC

I do not run the merc filter...its a water separator more than a filter I think..I run a large fram H/P

a couple good places for boost info is pontiaczone.com forced induction forums.

Yellowbullet.com

theturboforums.com which BTW has a marine section started.

I moderate the pontiaczone.com forced induction forums. Lots of great info and helpful people there its not just pontiac specific we have other makes there too.