Author Topic: Injector information.. 3.5L engines  (Read 2303 times)

Shovel

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Injector information.. 3.5L engines
« on: June 26, 2017, 01:04:58 PM »
I was researching injectors because I have to take mine out and was considering oversizing them a little to make a future E85 conversion easier

I know ethanol has become a controversial topic and like religion and politics I'm not going to engage in debate.   This won't be my first E85 conversion or my last.  End of that conversation.  This topic is not about that, it's about injectors only.

So here is what I have been able to find out so far.    Note that there are dozens of interchange numbers for fuel injectors so I just picked one for which I could find a single numbering convention.     I don't have any idea what specifically the nozzle pattern refers to. 

Montero (not Sport) 3.5/3.8 applications:

1994-1996 have EV1 style injectors MP4041 rated 27.5lb/hr 285cc/min nozzle pattern "2"

1997 has EV1 style injectors MP1048 rated 32.3lb/hr 330cc/min nozzle pattern "2"

1998-2000 has Denso style MP4187  rated 25.5lb/hr 260cc/min nozzle pattern "2"

2001-2002 has Denso style MP4197  rated 27lb/hr 272cc/min nozzle pattern "2"

2003-2006 has Denso style MP4204 rated 18.5lb/hr 190cc/min nozzle pattern "2"

Montero Sport 3.5:

All 3.5 Denso style MP4187  rated 25.5lb/hr 260cc/min nozzle pattern "2"

Galant & Endeavor 3.8

Denso style MP4199 rated 26.5lb/hr 270cc/min nozzle pattern "2"

Diamante 3.5 - this one is interesting..

Denso style MP4182 rated 31lb/hr 316cc/min nozzle pattern "3"


The Diamante engine isn't really rated much higher horsepower,  but that's a massively larger injector flow capacity and what's with the different nozzle spray pattern?   




Justice

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Re: Injector information.. 3.5L engines
« Reply #1 on: June 29, 2017, 10:08:20 PM »
Interesting indeed...

TOASTY

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Re: Injector information.. 3.5L engines
« Reply #2 on: July 05, 2017, 10:17:52 AM »
That Diamante is likely the VR-X engine and it is the very last of the 3.5 DOHCs by Mitsubishi Stateside. They have more horsepower and torque.

Shovel

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Re: Injector information.. 3.5L engines
« Reply #3 on: July 05, 2017, 10:58:23 AM »
The part I find a little confusing is 31lb injectors,   six of those @ 47psi is sufficient for ~330-350 horsepower at 80-90% duty cycle.

The X engine is only rated around 210hp last I checked..

 


haolepinoy

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Re: Injector information.. 3.5L engines
« Reply #4 on: July 26, 2017, 09:00:53 AM »
Shovel (or anybody really), could you try to explain why the later Gen3s have such a different flow rate than the earlier engines? I do not understand how to read this, but some part of my brain wonders how it's possible to square having a larger displacement (3.8L) and terrible gas mileage with such a piddly flow rate.

1994-1996 have EV1 style injectors MP4041 rated 27.5lb/hr 285cc/min nozzle pattern "2"

1997 has EV1 style injectors MP1048 rated 32.3lb/hr 330cc/min nozzle pattern "2"

1998-2000 has Denso style MP4187  rated 25.5lb/hr 260cc/min nozzle pattern "2"

2001-2002 has Denso style MP4197  rated 27lb/hr 272cc/min nozzle pattern "2"

2003-2006 has Denso style MP4204 [/b]rated 18.5lb/hr 190cc/min nozzle pattern "2"[/b]
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Shovel

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Re: Injector information.. 3.5L engines
« Reply #5 on: July 26, 2017, 09:32:39 AM »
Shovel (or anybody really), could you try to explain why the later Gen3s have such a different flow rate than the earlier engines? I do not understand how to read this, but some part of my brain wonders how it's possible to square having a larger displacement (3.8L) and terrible gas mileage with such a piddly flow rate.


I'm more curious about this from the reverse perspective,  why do the older ones have such great flow rates compared to their output.

Since pretty much every internal combustion engine used in production cars shares the same basic layout (there's a filter, a intake tract, there's a throttle valve of some sort,  more intake tract,  a valve, a cylindrical combustion chamber,  another valve, and some tubing with baffles in it on the way out to the atmosphere)  every engine pretty much ends up extracting about the same amount of power from the same amount of fuel.     

There are variations but we're talking coarse numbers here for this particular conversation. 

When somebody is building an engine or upgrading an engine they have to be able to estimate injector size before they get started,  you wouldn't want to build a 5 liter V8 with only enough injector to supply 50 horsepower worth of fuel.     There are numerous injector flow calculators available for this and for the most part you can just type in a number of injectors,  a fuel pressure,  an expected amount of maximum horsepower and how much duty cycle you wish to use up (generally 80%-90% at peak horsepower is considered good)

On any of these calculators entering 6 injectors, 47psi, 200 horsepower and 90% duty cycle gives us about a 18lb/hr injector.   At 80% duty cycle that's still a 20lb/hr injector.

But if we look at the 3.5L engines they all have much, much more injector than that.    The 1997 32.3lb/hr injectors are capable of flowing enough fuel for 360+ horsepower at 90% duty cycle.     So at peak output for that engine they're only running like 60% maybe? 

The 18.5lb/hr we see for 215 horsepower in a 3.8L Montero is a lot closer to the expected 90% duty cycle injector size that would be normal in any unmodified vehicle.     A smaller injector running closer to its maximum is going to allow finer control of fuel metering (0-90% is higher resolution than 0-60%) and almost certainly provide a finer spray pattern/atomization due to nozzle size being appropriate to the normal peak flow rate. 

So the question really isn't why does the 3.8 have injectors which are too small - they're the right size for the engine's horsepower.    Why does the 3.5 have such oversized injectors?

A possible answer to that might be that historically fuel quality was worse - particularly outside of developed and stable nations - so the engineers traded some efficiency for versatility.    An oversized injector can simply be held open for a longer duty cycle when a clogged fuel filter causes a drop in fuel pressure, for example - that option isn't as readily available when a smaller injector doesn't have much reserve duty % available.    But that's just speculation.   

haolepinoy

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Re: Injector information.. 3.5L engines
« Reply #6 on: July 26, 2017, 02:05:53 PM »
Thank you. That was a great explanation. Appears I was looking at it backwards then.

Would you humor another question since we're on the subject: you brought up "duty cycle" and I don't understand what that exactly means. Could you explain it?
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Shovel

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Re: Injector information.. 3.5L engines
« Reply #7 on: July 26, 2017, 02:56:35 PM »
Duty cycle is just a term used in machinery that references how much of a device's total time is available for doing work. 

100% duty cycle means always on.    An injector running at 100% duty cycle would just open one time and whatever fuel flows during that time would come out and not any more.   In a computer controlled gasoline engine the injectors pulse on,  and the computer determines how long to make those pulses.    If there are 1000 pulses per second and the window for fuel injecting is 1/10th of a second then leaving the injector open for 100 milliseconds would be 100% duty cycle.   Opening the injector 10 times for 9 milliseconds would be 90% duty cycle.   Opening the injector 10 times for 5 milliseconds would be 50% duty cycle, etc.    So you don't want to size your injectors for 100% duty cycle because that doesn't leave you any room for times you'd need more fuel,  like for example when you drive below sea level,  or put additives in your fuel or your oxygen sensors begin to age and misreport,  fuel pressure regulator begins to fail maintaining full pressure, etc.    Those conditions would then cause the engine to run lean at WOT. 

The other side of that is if your injectors are sized much too large and you have to run a shorter duty cycle,  even at wide open throttle the injectors are only open 60% of the time then your fuel metering "steps" are only really between like 5% and 60% , which creates a bit of the same problem where you run out of trim for super high elevations and additionally a big injector that's only open 5% of the time is going to do less spraying and more dribbling of fuel.    A bit like if you have a garden hose and just flick the valve open for 1/2 second, is water going to spray out the end of the hose or trickle?     

Through decades of development most manufacturers wind up sizing their injectors to operate as close as comfortable to 100% duty cycle at 100% power demand.   Why not right?   The engine's not going to randomly make 120% of the power it's supposed to make.     A 90% duty cycle turns out to be about right for modern engines.   

« Last Edit: July 26, 2017, 03:01:20 PM by Shovel »

haolepinoy

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Re: Injector information.. 3.5L engines
« Reply #8 on: July 26, 2017, 07:25:36 PM »
Thanks Mr. Shovel. I'm slowly learning here...not sure what my brain's duty cycle is but I'm sure there's probably a clogged filter or two up there that makes things work a little slower than they used to.
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kalieracer

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Re: Injector information.. 3.5L engines
« Reply #9 on: February 06, 2018, 10:23:00 AM »
I think some of these numbers are wrong.. I seem to recall the injectors that came off 96 being like 205 or 210cc. The 330 is way to high of flow for 97. Keep in mind TT 3000gt came with 360 from the factory. Injectors base flow is measured at 43.x psi for ratings. At 47 PSI the injector will flow more.

Shovel (or anybody really), could you try to explain why the later Gen3s have such a different flow rate than the earlier engines? I do not understand how to read this, but some part of my brain wonders how it's possible to square having a larger displacement (3.8L) and terrible gas mileage with such a piddly flow rate.


I'm more curious about this from the reverse perspective,  why do the older ones have such great flow rates compared to their output.

Since pretty much every internal combustion engine used in production cars shares the same basic layout (there's a filter, a intake tract, there's a throttle valve of some sort,  more intake tract,  a valve, a cylindrical combustion chamber,  another valve, and some tubing with baffles in it on the way out to the atmosphere)  every engine pretty much ends up extracting about the same amount of power from the same amount of fuel.     

There are variations but we're talking coarse numbers here for this particular conversation. 

When somebody is building an engine or upgrading an engine they have to be able to estimate injector size before they get started,  you wouldn't want to build a 5 liter V8 with only enough injector to supply 50 horsepower worth of fuel.     There are numerous injector flow calculators available for this and for the most part you can just type in a number of injectors,  a fuel pressure,  an expected amount of maximum horsepower and how much duty cycle you wish to use up (generally 80%-90% at peak horsepower is considered good)

On any of these calculators entering 6 injectors, 47psi, 200 horsepower and 90% duty cycle gives us about a 18lb/hr injector.   At 80% duty cycle that's still a 20lb/hr injector.

But if we look at the 3.5L engines they all have much, much more injector than that.    The 1997 32.3lb/hr injectors are capable of flowing enough fuel for 360+ horsepower at 90% duty cycle.     So at peak output for that engine they're only running like 60% maybe? 

The 18.5lb/hr we see for 215 horsepower in a 3.8L Montero is a lot closer to the expected 90% duty cycle injector size that would be normal in any unmodified vehicle.     A smaller injector running closer to its maximum is going to allow finer control of fuel metering (0-90% is higher resolution than 0-60%) and almost certainly provide a finer spray pattern/atomization due to nozzle size being appropriate to the normal peak flow rate. 

So the question really isn't why does the 3.8 have injectors which are too small - they're the right size for the engine's horsepower.    Why does the 3.5 have such oversized injectors?

A possible answer to that might be that historically fuel quality was worse - particularly outside of developed and stable nations - so the engineers traded some efficiency for versatility.    An oversized injector can simply be held open for a longer duty cycle when a clogged fuel filter causes a drop in fuel pressure, for example - that option isn't as readily available when a smaller injector doesn't have much reserve duty % available.    But that's just speculation.

Shovel

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Re: Injector information.. 3.5L engines
« Reply #10 on: February 06, 2018, 11:10:06 AM »
I think some of these numbers are wrong.. I seem to recall the injectors that came off 96 being like 205 or 210cc. The 330 is way to high of flow for 97. Keep in mind TT 3000gt came with 360 from the factory. Injectors base flow is measured at 43.x psi for ratings. At 47 PSI the injector will flow more.


I just went off what the part numbers said.   

http://www.injectorwarehouse.com/bostech-fuel-injector-for-a-multi-port-fuel-injection-system-part-mp1048.html




ChargerX3

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Re: Injector information.. 3.5L engines
« Reply #11 on: February 06, 2018, 01:28:04 PM »
You planning to tune for the injector size and latency, or size them x% larger for the extra fuel requirements?