Bigger injectors now what...

[bimma360]

My Dinan boosted at 11-12psi on 25lb injectors and a stock pump.

[FLG]

I made it to 14psi with stock pump and 50lb injectors.

You could also run a 255 in tank on an early model. Slight cutting of the line on the sender is required (too long otherwise) then I bypassed my stock pump.

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[einstein57]

I feel like stock pumps on larger injectors meant to run at 3.5bar, 3.5bar u said right, are running at full load just to keep up with the larger injector fuel needs. It may only be SLIGHTLY larger but it's not what the stock injectors were. Hence possibly making the pumps work harder... My coworker explained it to me in a more scientific way. But he was saying something like at idle the pumps at full volume trying to keep up with the tune. Idk

To me it seems like if your going beyond stock injectors it may be time for pumps that can flow better than stock also. Just kinda makes sense to me....idk

If a fuel pump was barely able to maintain idle then the car would not be able to accelerate at all even on a stock tune. Whether your running 14lb stock injectors or 100lb injectors your still flowing the exact same amount at idle. It just squirts the same amount of fuel in a shorter period of time. I believe the stock fuel pump is something like 180 liters per hour which breaks down to about 50cc per second. If your engine consumed that much you'd need to have a gas tank the size of hot tub. Here is a breakdown of fuel consumption based on horsepower. http://en.wikipedia.org/wiki/Brake_s...el_consumption. Also work is change in pressure, not volume. So if you were to run a 4bar FPR then you would be making your pump work harder.

In case your wondering i'm running 80lb injectors on my 300k+ miles original pump. Had no problem with 42lb injectors with e85 at 14psi.

I was referring to the ppl trying to tell me how a stock ecu with bigger injectors is useless. Ppl nitpicking at my build style rather than answering my question.

In reality we all help each other get our builds done. That's why forums can sometimes be insightful.

I'm going to search other builds, but NO ONE has explained the 2 fuel pump system or anything. Which pump would a higher flow walbro 255 go??

I have a pump going (warm starts just crank and crank sometimes unless I gas it) and would rather not buy a oem pump and a higher flow rated down the road when I turbo in a few months.


Where would the high flow pump go?
In the tank? Outside of the tank above filter? Or both. At this point I might just fuck with both of me.

If you have an early model then you don't use walbro 255. You would get a Bosch 044 (300lph). Not cheap and not usually needed unless your going over 20psi of boost. Tre now makes a 225lph version of like the bosch unit called the TRE-200. Not sure if its any good. If your external pump make a lot of noise when your tank is empty chances are your lift pump is dead.

[delatlanta1281]

Who's doing your head work? Please don't say you are..... and if you are, and we are on the subject of what you are planning, those +1 valves are useless. Stick to the regular FP and let someone teach you how to build a motor.
Guys like Jlevie have forgotten more than most of us will ever learn.

[ROLLingKING]

Ooookay. now i have a better understanding of whats going on back there. Jlevie, dnguyen1963, BergerNJ and deutschmon thank u much for your input. I now know which direction to go in. Feels good needing one less part to go turbo.

[kamotors]

Nobody is trying to teach you how to build a car!
They all gave out legitimate answers. Regardless of your injector size, some pumps have failed at low psi and some at high.

Mine failed at aroind 8psi with 42#, kamotors is still going on oem 15psi+ with 42#'s.

I never had 42lbers.

I'm going at 20-23psi on 60lb injectors on stock pump with NO issues:)

[jlevie]

As stated above, cars with the 55L tank have a low pressure high volume pump in the tank to supply fuel to the external high pressure pump. Cars with the 63L tank have a single in-tank high pressure pump. If the pump(s) are in good operating condition (not 20'ish years old and worn) you probably won't have flow problems below about 14psi of boost.

One thing to consider. While you could install a higher capacity pump in anticipation of FI in the future, until then too large of pump could overwhelm the FPR as the car sits now.

To me it seems like if the flow rate is increased but not the flow through the injectors, then the flow through them should be upped. A FPR would help but I still think that would then be putting the stock lower flow rated pump through more stress.

I'm not exactly sure what you mean there. The flow into the engine is determined by the rail pressure, injector flow rate, and injector firing pulse width. As long as none of those dependancies get too far off the DME will make larger injectors look like the stock injectors with respect to the fuel delivered to the engine and the resultant AFR.

The other thing to keep in mind is that the high pressure pump is always working at full capacity with excess fuel being returned to the tank via the FPR. So the stress on the pump doesn't materially change with a change in flow rate of the injectors. You only need a higher capacity pump if flow into the engine gets high enough that the pump can no longer maintain proper rail pressure.

[dnguyen1963]

To me it seems like if the flow rate is increased but not the flow through the injectors, then the flow through them should be upped. A FPR would help but I still think that would then be putting the stock lower flow rated pump through more stress.

Idk a lot of Nissan, ae86 drifters, and my buddy with nitrous in his Lexus all suggested now that I've started f'ing with injectors and a chip I should up the pump before I mega squirt and boost. Especially since they've heard my car not want to start when it's time to leave a meet. (fuel pump issue)


Which fuel pump?! Does one do most of the pumping and then the other just does what?
Can anyone explain the 2 pumps instead of trying to talk me out of doing my own experimenting. If I can understand the system more I'd understand why upgrading would be a waste more than u just trying to tell me ppl have had stock shit last up to whatever. Sometimes upgrading the part is cheaper than stock....and may yield more enjoyable benifits

In tank is the low pressure pump. Its main purpose to to feed the high pressure (outside) pump. You can call Tre Performance and ask for their recommendation as to which pump you should use. As with any pump, there will be good and bad reviews. Personally, Tre pump has been reliable for me and it is way cheaper than stock.

[BergerNJ]

so....the first pump just pulls the fuel from the tank, its a low pressure pump....The second pump, the out of tank pump, is high pressure, and pressurizes the system. If memory serves correct.....

Also, I think I read a long time ago, from quick browsing, that some guys eliminate the 2 pump system when they upgrade.....not for nothing but a simple search would yield results...

Jlevie posted a quick and simple response, but just from memory alone I can tell you he has written some very in depth fuel related posts......so go search for it brotha

[ROLLingKING]

A chip for larger injectors isn't really going to significantly increase flow through the injectors. It might bump the A/F ratio slightly, but the tune for the larger injectors is mostly to account for the higher flow rate of the injectors.

To me it seems like if the flow rate is increased but not the flow through the injectors, then the flow through them should be upped. A FPR would help but I still think that would then be putting the stock lower flow rated pump through more stress.

Idk a lot of Nissan, ae86 drifters, and my buddy with nitrous in his Lexus all suggested now that I've started f'ing with injectors and a chip I should up the pump before I mega squirt and boost. Especially since they've heard my car not want to start when it's time to leave a meet. (fuel pump issue)


Which fuel pump?! Does one do most of the pumping and then the other just does what?
Can anyone explain the 2 pumps instead of trying to talk me out of doing my own experimenting. If I can understand the system more I'd understand why upgrading would be a waste more than u just trying to tell me ppl have had stock shit last up to whatever. Sometimes upgrading the part is cheaper than stock....and may yield more enjoyable benifits

[ROLLingKING]

Nobody is trying to teach you how to build a car!
They all gave out legitimate answers. Regardless of your injector size, some pumps have failed at low psi and some at high.

Mine failed at aroind 8psi with 42#, kamotors is still going on oem 15psi+ with 42#'s.

I was referring to the ppl trying to tell me how a stock ecu with bigger injectors is useless. Ppl nitpicking at my build style rather than answering my question.

In reality we all help each other get our builds done. That's why forums can sometimes be insightful.

I'm going to search other builds, but NO ONE has explained the 2 fuel pump system or anything. Which pump would a higher flow walbro 255 go??

I have a pump going (warm starts just crank and crank sometimes unless I gas it) and would rather not buy a oem pump and a higher flow rated down the road when I turbo in a few months.


Where would the high flow pump go?
In the tank? Outside of the tank above filter? Or both. At this point I might just fuck with both of me.

[ak-]

Nobody is trying to teach you how to build a car!
They all gave out legitimate answers. Regardless of your injector size, some pumps have failed at low psi and some at high.

Mine failed at aroind 8psi with 42#, kamotors is still going on oem 15psi+ with 42#'s.

[ROLLingKING]

A chip for larger injectors isn't really going to significantly increase flow through the injectors. It might bump the A/F ratio slightly, but the tune for the larger injectors is mostly to account for the higher flow rate of the injectors. Meaning that the DME doesn't have to "learn" a lower pulse width.

On a street car you don't want the AFR to go much below 13.5:1, if that low, to avoid carbon fouling the plugs and coking up the cylinders. And there is really not much gain to be had unless work has been done to the head to increase mass flow thorough the engine or FI is employed to increase mass flow.

A well built, fully stock engine & DME with a good exhaust, can make 160-165rwhp on a DynoJet. That might mean as much as 184-190hp at the crank. in my experience that is more than a chip and/or bigger injectors will produce. My guess is that a properly tuned MS on the same engine would yield a bit more.

Thanks man. I am in the works of getting a stripped head shipped to me so I can work on it in the house and increase that flow. I already have the high rev valve springs that vac sells and have my mind made up on their m20 performance valve kit. +1mm ftw!!

I have a 173 ecu here also but im still saving up for a pnp megasquirt to have put in. A buddy gave me his STI turbo after he went big turbo so I want to learn to tune a bit na and then I'll eventually be turbo.

I guess long story short, have people here had good results using the OEM fuel pumps all the way through a little head work, injectors, and turbo?

Please don't try and teach me how to build my car. This fuel pump specific. Thanks to those who have offered insight!

[jlevie]

I don't have a stock ecu. Otherwise why put in any injectors if the computer is telling them to do the same shit.

A chip for larger injectors isn't really going to significantly increase flow through the injectors. It might bump the A/F ratio slightly, but the tune for the larger injectors is mostly to account for the higher flow rate of the injectors. Meaning that the DME doesn't have to "learn" a lower pulse width.

On a street car you don't want the AFR to go much below 13.5:1, if that low, to avoid carbon fouling the plugs and coking up the cylinders. And there is really not much gain to be had unless work has been done to the head to increase mass flow thorough the engine or FI is employed to increase mass flow.

A well built, fully stock engine & DME with a good exhaust, can make 160-165rwhp on a DynoJet. That might mean as much as 184-190hp at the crank. in my experience that is more than a chip and/or bigger injectors will produce. My guess is that a properly tuned MS on the same engine would yield a bit more.

[bmwguy325is]

Im guessing you have an early car?