Could the in tank pump be the real problem?

N

nig3

Member
Seems to me that the in tank pump supplys the flow or volume of fuel to the cam driven pump and then the CDFP is responsible for raising the pressure for the direct injection, right???
If this is true then why do i keep hearing that its the CDFP that needs to be replaced to eliminate the fuel delivery problems that everyone is experiencing?? wouldnt it make more sense to upgrade the in tank pump rather than the CDFP to increase fuel flow/ volume to the CDFP?? Makes perfect sense to me.
there is one guy on here ( the only one ) that has actually replaced the intank pump rather than the CDFP and he claims that his sputtering problem has completely dissapeard unlike the few people that have replaced the CDFP instead.
For instance on my wrx i hit a brick wall at around 230whp until i upgraded my intank pump to the walbro 255lph then i was able to hit 275whp with my VF34 turbo. It would make perfect sense that replacing the intank pump would do you more justice than replacing the CDFP. the CDFP is basically there to step up fuel pressure only for the direct injection and has nothing to do with flow or volume. Just somthing to think about, what do you guys think????
 
try it, nobody thinks it will help.
if more and more people say it solves the problem, then it may be a worthwhile mod.

I really have no idea on the subject, but itd be worth a try.
 
the reason i even brought this issue up is because fuel pressure and fuel volume are to completely different things, and the intank FP would be responsable for the volume and the CDFP is only responsible for fuel pressure, and with out enough fuel going to the CDFP you wont have enough fuel supply for the CDFP to to its job correctly, definatly worth looking into if you ask me. anyone else have any input on this matter? just curious
 
nig3 said:
the reason i even brought this issue up is because fuel pressure and fuel volume are to completely different things, and the intank FP would be responsable for the volume and the CDFP is only responsible for fuel pressure, and with out enough fuel going to the CDFP you wont have enough fuel supply for the CDFP to to its job correctly, definatly worth looking into if you ask me. anyone else have any input on this matter? just curious
Click to expand...


Thats not necessarily true. For 2 pumps in series, the last pump HAS to be able to pump enough volume to keep up with the engine demand at the proper pressure. The volume needed by the engine MUST be fulfilled by the CDFP or it will starve. The intank pump MUST flow enough volume to keep the CDFP feed at its flowrate. So the intank pump must flow the same or more than the CDFP or the pressure will never reach its target.

The intank pump is solely there to feed the CDFP.
 
Jays07MS3 said:
Thats not necessarily true. For 2 pumps in series, the last pump HAS to be able to pump enough volume to keep up with the engine demand at the proper pressure. The volume needed by the engine MUST be fulfilled by the CDFP or it will starve. The intank pump MUST flow enough volume to keep the CDFP feed at its flowrate. So the intank pump must flow the same or more than the CDFP or the pressure will never reach its target.

The intank pump is solely there to feed the CDFP.
Click to expand...

Your right sir!! but what if the wussy stocker in tank pump isnt feeding the CDFP enough to do its job correctly on modded MS3's thats what im talking about.
 
Just because the cam driven pump is pushing 1300 PSI at the fuel rail doesn't mean that a large volume of fuel is going into the engine!!!!!! A SMALL VOLUME of fuel is injected at a HIGH PRESSURE. A HIGH VOLUME of fuel to pushed to the engine at a LOWER PRESSURE. You guys are a bunch of jokers. Can you not comprehend a word of what Laloosh and Driver311 are saying?
 
3.slow said:
Just because the cam driven pump is pushing 1300 PSI at the fuel rail doesn't mean that a large volume of fuel is going into the engine!!!!!! A SMALL VOLUME of fuel is injected at a HIGH PRESSURE. A HIGH VOLUME of fuel to pushed to the engine at a LOWER PRESSURE. You guys are a bunch of jokers. Can you not comprehend a word of what Laloosh and Driver311 are saying?
Click to expand...

Im sorry but just because laloosh and driver 311 were the first two people to asume that they needed a new cdfp from a few data logs doesnt mean that they know what they are talking about!!! its to my understanding that they still had some issues even after the PG pump install. and then they change there story saying it solved there problems. there is also a guy on here that swears that by changing to a copper plug and running a smaller gap he got the same results as the pg pump??? and then another guy replaced his in tank pump for the walbro 255lph and that fixxed his sputtering issues as well. so you see, what laloosh and driver 311 have said is not written in stone yet, its still too early to tell what the real cause of this issue is. we still need to have an open mind and not rush out buy everything that laloosh and driver 311 have told us to buy. sorry, just being realistic. (crazy)
 
heres the quote from ate baller the one guy with the bigger in tank pump---->>> " increasing the pressure at the inlet (which is exactly what upgrading the in-tank pump will do), the cdfp's output will increase as well, like a booster. For me (the only one currently with an upgraded in-tank fuel pump), this has eliminated my fuel cut thus far. 2,000 miles strong with no ill-effects, and no fuel cut, even in subfreezing temperatures. Fuel cut disappeared after removing the atp bck, the day after installing the itfp. The problem with the Walbro is that it doesn't fit right, but there is one that does. It's being installed and tested on a vehicle this weekend, and there will be some data backing up everything I've said in the following week. The other pump also flows 265lph, so it's a little stronger than the Walbro too, and it should also be about $15 cheaper if it's the one I think it is.

Oh, and the cdfp upgrade hasn't solved the fuel cut problems either. Anyone who's tried to tune with one has still gotten fuel cut. I'm not saying I wouldn't have the same problems if I tried to tune my car, but don't think the upgraded cdfp is a cure-all.
ATE BALLER is offline Report Post Reply With Quote

^^^^^in case anyone hasnt noticed yet ^^^^^^^
 
A side note, Driver311 has inquired with me about the itfp as well. I believe he's getting on the list for the tool once Whooosh's testing is complete. The cdfp is essentially an amplifier. If it recieves less than 61psi of supply, it does not opperate correctly. If it recieves more, it obviously pushes more.
 
I want the intank pump for sure. Ive wanted one since I bought the car. I plan on alot higher whp levels than the average member though. BIG PLANS, BIG BIG PLANS. LOL
 
What about someting like the KB boost a pump. I heard tons about this during my SVT days when i was adding my KB supercharger.

http://www.kennebell.net/accessories/boostapump/boostapump.htm

How it Works - While dyno and street testing, our On Board Data Logger told us that fuel flow was less at night when the lights, stereo etc. were on. The voltage to the pump was varying between 12 and 13.5 volts and fuel was being reduced up to 15%. Further testing in our Fuel Flow Lab indicated that by elevating the voltage to the pump we could safely increase fuel capacity by as much as 50%. The Kenne Bell BOOST-A-PUMP™ does just that - and it automatically maintains the pre-set voltage or % increase with as little as 10 volts at the battery.
Click to expand...


In conjunction with our chips, we developed the Boost-A-Pump to safely increase the work of the
stock pump to deliver up to 50% more fuel. Note how the pressure begins to drop off at higher
RPM in FIG 1. as well as voltage delivery to the pump (these are directly related to flow). Look
at FIG 2. to see the effect of fuel delivery with the Boost-A-Pump. Note how 100% Duty Cycle is
never reached. Beautiful! The pump works much less and outputs much more fuel.
Click to expand...
 
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I have a scavenge pump that pushes 2 gallons per minute and can stand 300 degrees fahrenheit. It was $250. How much is the kenne bell stuff.
 
Haltech said:
They pre-maturely burn out the pumps by running them above their duty cycle. Its a bandaid for a solution when they pump should just be replaced.
Click to expand...

Thats actualy a myth. KB has tons of data showing how there boost a pump never runs stock the system even close to there duty cycle. See the link after the jump for great info.


http://www.kennebell.net/techinfo/general-info/BAPtheory_kens.pdf




MYTH: “THAT EXTRA VOLTAGE WILL HURT YOUR PUMP” we developed the Boost-A-Pump to safely increase the work of the
stock pump to deliver up to 50% more fuel. Note how the pressure begins to drop off at higher
RPM in FIG 1. as well as voltage delivery to the pump (these are directly related to flow). Look
at FIG 2. to see the effect of fuel delivery with the Boost-A-Pump. Note how 100% Duty Cycle is
never reached. Beautiful! The pump works much less and outputs much more fuel. MYTH: “THAT EXTRA VOLTAGE WILL HURT YOUR PUMP”
FACT: The installation of our Boost-A-Pump will actually increase pump life by reducing its
workload. BTW: the Boost-A-Pump only increases the voltage when required under boost
conditions. It is a passive system otherwise.
Click to expand...
 
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this is a good question that many in the other forum are working on

to be honest, until someone has a FP gauge BEFORE THE CAM PUMP
and monitors fuel pressure and possible fuel pressure drop at WOT....

nobody can say for sure what the deal is

the speed6 group and I have sent an OEM in tank pump to Kinsler fuel injection for flow testing

if you want to know that facts come over and see us sometime
 
whooosh said:
this is a good question that many in the other forum are working on

to be honest, until someone has a FP gauge BEFORE THE CAM PUMP
and monitors fuel pressure and possible fuel pressure drop at WOT....

nobody can say for sure what the deal is

the speed6 group and I have sent an OEM in tank pump to Kinsler fuel injection for flow testing

if you want to know that facts come over and see us sometime
Click to expand...

oh im there (lurk)
 
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