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ok just wondering. How do the turbo guys deal with the fuel problems. I read alot of posts by the jr guys but i have not read any about people with the revhard or drag kits. is there something very different about the fuel needs of turbo vs. super that you cant learn from the turbo kits. Just Wondering. laters
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94gsr, Drag3 and yellow paint goin on in april
Wow...great article Jim! Even though this is the second time you wrote it...DOH! WEBTV.. http://www.hostboard.com/ubb/wink.gif
Sigh... http://www.hostboard.com/ubb/redface.gif Anybody wanna buy a B&M Commandflo?
http://albums.photopoint.com/j/View?...436&Sequence=0
http://albums.photopoint.com/j/View?...435&Sequence=0
I should've waited a while longer before I bought the thing but since Lundgren and others are having problems adjusting it. I'll wait until Nitro has something else to say. If not, then I may opt to return back to Summit (good thing they have a 30-day no hassle return guarantee). Anybody have it working yet....comments???
[This message has been edited by zip (edited January 15, 2000).]
I've measured more like 50psi with vaccuum which is 7psi higher than stock and 60psi with the vaccuum line disconnected, again 7psi over stock. The point is the same 1:1 rise ratio is maintained but at elevated pressure. The ECU compensates for the higher flow rate when in closed loop operation. Apparently it has enough latitude.
The 5:1 fuel to boost rise ratio stops at around 4.5psi of boost or at around 85psi of fuel. This appears to be enough at 6psi. In this case the rise is a bit too fast until 4.5psi where it levels off. I'd say the mixture moves progressively to the rich side of optimum until 4.5psi of boost is reached, above that the mixture leans out somewhat as boost increases, but not too much. With the 3.8 inch pulley there's 5% more air, but no more fuel. In this case it's leaner, definitely too lean with some cars. Maybe just barely adequate with others. It's on the edge. JR is relying on the limits of the fuel pump the supply as part of the fuel management system.
I agree, larger injectors and a riser with a lower ratio are in order combined with lower idle and boost fuel pressures. If the pressure is kept below 70psi, the GSS317 pump has adequate capacity for the boost levels we're talking about.
Now thats what I'm talking about!
That post was great JRCivic and confirms my theory of the B&M conspiracy.
BTW- Where do I get a guage to mount on the filter??
[This message has been edited by Turismo (edited January 15, 2000).]
okay now this may be a very stupid question for all you goru's.. But since I didn't install the fuel pump and had no idea there was a differnce between a high output one and reg .. How in the world could I tell which one I have by looking at it?? Does that mean I have to rip out my back seat and unscrew that metal disc in the middle to take it out and look?? BTW .. excellent excellent post JRCIVIC.. it is really cool to know we have you expertice on hand. How about ummm "intake 101"?? There is much debate over short tube or aem. Whatcha think?? http://web.camaross.com/bb/eek.gif
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1998 Super Sonic Blue Gs-r
Jrsc w/ fuel pump upgrade
boost & air/fuel guage
Modified CAI
Ground Controls w/ agx's
Neuspeed front strut bar
Power slots
To reiterate what Jim stated, the fuel pump you should have when boosting higher than stock boost is either the GSS317 or the GSS342 (preferred) stamped on the body of the fuel pump.
As for the intake, here's what TOO had to say:
__________________________________________
Air Induction: A properly designed induction tube with air cleaner should
be used. I don't favor tubes that are of small consistent diameters, as the
column of air in the tube is to slow to properly react to a supercharged
engine's needs. Although, a cold air box is needed, the short large diameter
induction tubes are the correct route to go. They are also somewhat less
expensive. Do not, under any circumstances, use one that tapers smaller as
it approaches the throttle body. I don't care what anyone says, throttle
bodies like slow moving air to draw from, and to do them right, the tube
should actually grow larger as it nears the throttle body.
___________________________________________
I hope that helps.
[This message has been edited by zip (edited January 15, 2000).]
For those who aren't sure of what pump they have mounted in their tank... do this test.
BOTTOM OUT THE JR FMU:
Loosen the 1/2" jam nut on the FMU and using a 3/16" hex key, turn the adjustment screw ALL of the way in. This will close the fuel return line and the pump will stop delivering fuel when it reaches its maximum flow rate. The GSS-317 (Low press) stops at about 85psi. The GSS-342 (high press) stops at about 115-120psi.
Now, don't forget to return the adjustment screw back to your original baseline settings. (60 psi is a good start... it is the factory setting)
The fuel pressure gauge, as zip showed in the picture above, mounts directly on top of the fuel filter. It can be bought from just about anywhere, and it is CHEAP... $35 to 60 depending on where you go. It comes with everything you need to install.
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'93 Civic Si H/B with B18C1, JRSC @ 8psi
Best 1320: 12.88 at 110 mph
The B&M filter mount gauge is $29.95 from Summit, part number BMM-46054...now if I could just find a 610mm belt part number...
That fuel business all makes sense, but this doesn't:
Why during tip in does the A/F meter go lean? Figure when the car was N/A (pre Blower) you could floor your car in any gear with the stock fuel pump and not have to worry about lean conditions. So now with the kit,(with stock pump and injectors) during hard tip in, the gauge goes lean, but at that second you are not yet in boost. Why is this? Shouldn't the fuel management be the same at N/A conditions with or without the blower?
The only other thing that has changed is the intake plenum which may flow more air than the stock intake thus causing a lean condition during hard tip in.
Your comments...
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'96 JR6 GSR Sedan
'93 Honda CBR 900RR
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4Sale:New Holley 255 fuel pump kit
#12-906 (Integra/civic)
$200 shipped COD
OK guys, after fighting MrBurns' car, I did a crash course in FUEL !!! Yes zip, this one is for you. Thanks for pestering the s__t outa me to post this.
First of all, we have a few basic given parameters. I will refer only to the 255 lph pump in this post, and I will differentiate the Walbro GSS-317 (Low pressure) and the GSS-342 (high pressure) as "LP" and "HP" respectively.
Now, JR ships the FMU preset from the factory at 60 psi of baseline (vac. off) pressure. This unit adjusts for both vac. AND boost conditions. It raises the fuel pressure in VAC at about 1 psi per in/hg. It raises the fuel pressure in BOOST at 5 psi per pound. Its minimum pressure limit is about 42 psi.
Thus, at idle (800 rpm) the fuel pressure with vac on is about 42-44 psi. If you pull the vac hose off the FMU and put your finger over it, your gauge will read about 60 psi. (I have made an assumption here that your fuel pressure gauge is on your fuel filter... if not, buy one and put it there !!! This is the only place that you will get the numbers that I am referring to here)
Now, for the pulley clarification. The 6 psi (4.0") pulley typically makes between 7 and 8 psi of boost on the typical GSR. The 8 psi pulley (3.8") pulley blows about 9.5 to 10 psi.
The LP pump runs out of pressure at about 85-90 psi.
The HP pump runs out of pressure at about 115 to 120 psi.
To test this in your car, do the following. Loosen the 1/2" jamnut on the FMU and screw the adjustment screw (3/16" hex) ALL the way in. This closes off the return line to the tank, and the pump will push until it can't flow any more. This reading is the max that your pump will flow in any given boost condition in YOUR CAR !!!
Does anyone see a problem yet !?!
Here is the dillema. IF your baseline setting is 60 psi, and you have 7 psi of boost, the FMU wants to keep 95 psi (60 + (5x7)) of fuel pressure in the rail, but the pump can only flow 85 !!! This creates a slow lean condition... as the injectors pull fuel from the rail, the pump will try to keep pushing, but it cannot keep up.
Worse yet, for those of you with the 3.8" pulley, the FMU is ordering about 110 psi, and the pump is done at 85 !!!
The solution is the HP pump. Since it flows 115-120 psi, it CAN AND WILL keep up.
Now, some people want to go with bigger injectors... and this is fine, but you must do the following. (Remember, the bigger the injector gets, the harder it is to control the idle)
for the 3.8" pulley, get 270 to 280 cc injectors. Pull your idle pressure on the FMU to about 52 to 54 psi. If you go with less than this, you will probably get some pinging at throttle tip-in in the midrange. The reason is that you will have NO enrichment from full vac to 0 psi boost.
I have heard about a B&M Command Flo variation that was talked about on the board... it DOES NOT work. Here is why: Fuel pressure is controlled by allowing more or less fuel OUT of the rail and into the fuel return line. Thus, lower rail pressures mean a larger opening in the valve to the return. If the minimum pressure of the FMU is 42 psi, the B&M cannot be adjusted to LESS than this... even though the opening in the B&M is larger, the fuel is being held up just 12 inches away by the opening of the JR FMU. You may get a very small change because of the distance, but it is almost undetectable.
This ratio will help you make adjustments on your own cars in your various climates: when you double fuel pressure, you increase fuel flow by 40%. You can work this out the other way if you have bigger injectors. OE size is 235 cc. If you get 270's, that is 15% more fuel at any given pressure... and thus you could reduce fuel pressure safely by 35%. Unfortunately, the JR FMU does not give us this much adjustment down. I am looking into the Vortech FMU, which adjusts from 25psi up to 150 psi and the ratios are also changeable. The JR is fixed at 5/1 in boost, 1/1 in vac. The Vortech can do from 1/1 up to 5/1 in boost or vac !!! Once I have tested one, I will report back.
Fuel 101 is over. If you have questions, E-mail me or post here. If you need a HP pump, E-mail me and I will get one out to you. I have 24 of them in stock.
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'93 Civic Si H/B with B18C1, JRSC @ 8psi
Best 1320: 12.88 at 110 mph