I just remembered why you'd want an external:

http://images.cardomain.com/member_i...79_62_full.jpg



I think Eric Bazan was using the RX dual intank on his t-trim setup.

Oneflyn - Just emailed RX today and got the usual 5 minute reply. Racetronix has been great to me, so I will definitely admit I'm biased. If Jack at RX doens't know what he's doing, he's a great poser.

J: At this stage of the game its worth some investigation and an email .

Ryan

 

For a very cool look at the impact of voltage on pump performance, checkout this graph of the Supra's pump output at 9, 12, 14, 16, and 18 volts: http://www.stealth316.com/images/suprapumptest.gif

What kind of life span a pump running 18 volts has I couldn't say, but it deffinitely gives creedance to the Boost-a-pump systems, and Racetronix's set up which addresses voltage levels. Cool stuff.

 

did his charcoal canister blow up?

 

good info to keep on hand. Thanks! Are these rwhp numbers through a T56 or a 4L60E? I know that's splitting hairs, but I'm shooting for close to those for my 383 build up and am just curious (hp losses at these levels add up quickly).

I've read the web site a while ago and just checked it out again... looks like there's more info available, although no listing or info regarding the double-pump set up. An install review, instructions, and FAQ might be time well spent in releiving some of those questions. (I know I have a few ready to go )

- cost of the double pump for f-bodies?
- serial or parrallel design?
- additional fuel line nessesary?
- is a high volume/pressure regulator nessesary? or will a stock LT1 suffice?
- is one pump mounted extrernally? if not, is it possible to do so (like the T-REX pump some blower guys use for higher pressures)
- is modification to the stock tank nessesary?
- is it available with a stock or larger baffelled tank?

 

The DP system was never meant to be a common production item but rather a custom item for dealer in-house project cars only. This is why we do not promote or support it on our web page. We build them when we have the spare time as they are very labor intensive to manufacture.

Numbers are RWHP with auto trans using factory lines.
Parallel design
A quality adjustable regulator (CAS recommended) is highly recommended but then how many people making 700RWHP use a factory regulator?
No modifications required.
Plumbing and wiring is fully PnP.
We do not sell fuel tanks but CAS does.

 

Please email us about you injector questions as this subject is outside the scope of this thread.

Back to emails...

 

i understand you dont make the dualpump setup commonly. but another question about it.
Can the dual pump setup be made to work with AN lines? im swapping to a 4 barrel style intake and factory fuel lines wont cut it. And what american shops carry the Racetronix brands? would we be able to order a dualpump setup through them IF that is what i decide on? Cost if i remember is comparable to the average external pump if i remember some quotes from months back.


thanks for any answers.

 

Thanks, I will look into that setup (DP). The only thing that scares me some is how long it might take to get it done since they are individual/custom order stuff.

What about running two external pumps in series? From my understanding that would increase the pressure not volume, correct? Makes sense to me. Parallel would increase volume (desired).

Jason

 

I have a weldon pump and filters and I have a voltage controller so the pump isn't that loud on the street but a flip of the switch its on full voltage and its ready to race.

I don't have the cash flow to do things 2 or 3 times so I went overkill the first time and if I decide to add a blower or turbo my fuel system is done.

 

Series pumps would help increase / maintain volume at higher fuel pressures. Parallel pumps are what you want to increase volume. A Walbro GSL392 can maintain very high fuel pressure without sever degradation in performance. We sell kits for external applications as well.

 

Depends....

Some systems are "vacuum compensated".... some systems are not. I do not agree that a stock system requires 58psi to operate.

The stock GM 3bar system does idle at 43.5psi DIFFERENTIAL pressure... remember, differential is fuel rail pressure minus intake runner pressure (and since minus a minus = a plus , differential pressure = rail + intake). That's why the vacuum compensation connection is on the regulator, and that's why the regulator is designed to hold 43.5psi DIFFERENTIAL pressure. A stock system will not idle at 43.5psi rail pressure... the rail pressure is reduced in propportion to intake vacuum to compensate. Since intake vacuum is in the range of MINUS 8 to MINUS 10psi, the rail pressure should only be operating in the range of 34-36psi at idle. 35.5psi (rail) - -8psi (intake) = 43.5psi differential.

Then when intake vacuum disapperas.... e.g. WOT.... the rail pressure returns to 43.5psi. 43.5 - 0 = 43.5psi differential. At no time does the stock 3bar system require the pump to produce 58psi.

It is entirely possible to tune the system without vacuum compensation, and my system is set up that way, running at a constant 58psi.... no vacuum compensation.

 

Ahhh... now I got it. So you're saying that the system isn't really 43.5 psi differential... it's actually 43.5 rail pressure at WOT, and only a 30psi (2 bar) differential over runner pressure?

Guess that would make a standard pressure pump good for ~12psi boost, and fine for LS1 applications. I'll need to check the Helms manual section on LT1 fuel systems again...

Thanks!

 

What did you do to accomplish this?
disconnecting the vacume line to the stock LT1 regulator wouldn't be enough to run 58psi if there is only a 2 bar differential... that'd leave you at 43.5psi rail all the time.

Do you have an aftermarket regulator set up? (I imagine you'd have to). If so... what have you done to the tuning to accomodate the loss of a vacume signal? If this is a drag-only car with WOT-only considerations I guess it'd be easy... but without that I imagine you're either on an aftermarket fuel system (FAST?), or spent a lot of time tuning the PCM.

Could you share a bit on tuning a car this way? Do you rely on speed density or MAF? What adjustments to the fuel delivery do you make to accomodate the different pressure differiental the injectors sense?

 

I don't know what you're missing here but the setup is simple… If you pull the vacuum line from the FPR you'll get a line pressure of about 43.5psi (really it's usually someplace between 40 and 45psi). Reconnect the vacuum line and it's going to be whatever is in the manifold added to that base pressure.

I don't know that I've ever had a vacuum gauge on my LT1 at idle, but I'm betting that it would be someplace around 15 in of mercury which is about 7psi, so if you put a gauge on the fuel rail at idle you'd measure about 36psi, but that is still the baseline pressure (~43psi) across the fuel injector.

WRT to the non vacuum referenced setup, on an NA engine it's really not all that different to tune then with a vacuum referenced FPR, you just have to add fuel faster as the manifold pressure goes up (vacuum drops). Real world, if you're just converting from referenced to non what you end up doing is decreasing the fuel delivery at part throttle. Boosted this can become a problem since as your intake manifold pressure goes up you'll see a much smaller pressure differential across the injectors and your fuel delivery will drop dramatically.

Most likely he's just running an adjustable fpr without a vacuum line connected…

 

As Mark pointed out... it is a TRUE 43.5psi (3 bar) DIFFERENTAIL fuel pressure on the stock LT1 system. Remember what DIFFERENTIAL pressure is.... the fuel enters the injector from the rail. It exits the injector into the head runner, which is very "roughly" at manifold pressure. If the rail is at 43.5psi, and the intake manifold pressure is at atmospheric pressure at WOT, then the difference it 43.5 - 0.0 = 43.5

What you may be having a problem with is the fact that using the label "psi" is incomplete, except when specifically speaking of DIFFERENTIL preassure. There are two different reference points for pressure..... PSIA = pounds per square inch absolute..... PSIG = pounds per square inch gauge. One is reference to an absolute vacuum, the other is referenced to standard atmospheric pressure. When you read the pressure gauge on the fuel rail, it is in PSIG. When you read the manifold absolute pressure (MAP) it is in PSIA (or the equivalent metric units).

At idle, a stock LT1 cam will produce a MAP of about 9.5-10"Hg. Since one "atmosphere" is (roughly) 30.0"Hg, and one "atmosphere" is also about 14.7psia, you can see that at idle the intake manifold pressure is about 5psia, or about -(minus) 10psig. Same pressure, different reference points.

At WOT, the MAP should be very close to "one atmosphere".... or at WOT your intake manifold pressure should be 14.7psia, or 0psig.... same pressure, different reference points.

To calculate DIFFERENTIAL pressure across the injector orifice, you need to have the rail pressure and the intake manifold pressure in the same units.....

And to complicate things even further.... the fuel rail pressure, read in "PSIG" is the correct reference system, because the pump is pulling out of a tank that is already at atmospheric pressure.

My fuel system:

-Bosch 205LPH intank pump, in stock support, converted to -AN fittings (runs full time)
-Sump on rear of stock tank, with internal screen filter
-10AN suction line from sump to external pump
-Bosch 205LPH external pump (runs only when nitrous system is armed)
-6AN flow lines from each pump, to an NOS -6AN "Y" fitting.
-SX billet filter
-6AN line to rear of fuel rails
-NOS -6AN "Y" fitting
-6AN line to the back of each fuel rail.
-6AN fitting welded to diagonal crossover line on front of fuel rails
-6AN return line to Weldon AFPR mounted under the cowl
-6AN return line to stock fuel tank connection.
-1/8" NPT boss on fuel rail for fuel pressure sensor

There is no vacuum compensation line run to the Weldon AFPR.

The engine management system is a MoTeC M48Pro with MoTeC IEX 8-channel ignition driver and 8 LS1 coils. Fuel control is speed-density, open loop. Fuel and timing maps developed on engine dyno, then verified on chassis dyno with engine in car. Lack of vacuum compensation simply means the maps, which are a function of RPM and MAP, need to provide enough fuel at each MAP level without the need for vacuum compensation.

The basic setup was done by Second Street Speed, not by me.... I know my limits .