9th injector on the L-Jet, for enrichment NOS,SC
10-15-2006, 01:04 AM
#2
Sure, that's the "old style" way of getting fuel enrichment under boost. Koenig Specials used that method with their Albrex s/c setups when they built their customer engines. And I think Corky Bell's book talks about that too.
I recently got rid of the 9th injector setup on my motor rebuild, and used 42 pounders instead, all optimized with a SharkTuner. Not to say the old way was bad, but I didn't trust that all cylinders were getting proper fuel under boost when you consider airflow characterics inside the intake, too many variables.
Those 9th injectors are typically located somewhere after the throttle body, and dump extra fuel into the intake flow when its triggered. You only hope its getting divided equally to each cylinder, and don't run into detonation. (makes for a squeeky clean intake though...)
I recently got rid of the 9th injector setup on my motor rebuild, and used 42 pounders instead, all optimized with a SharkTuner. Not to say the old way was bad, but I didn't trust that all cylinders were getting proper fuel under boost when you consider airflow characterics inside the intake, too many variables.
Those 9th injectors are typically located somewhere after the throttle body, and dump extra fuel into the intake flow when its triggered. You only hope its getting divided equally to each cylinder, and don't run into detonation. (makes for a squeeky clean intake though...)
10-15-2006, 01:25 AM
#4
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If you do try to use the cold start injector, I reckon you should move it to the front of the plenum, ala CIS. I wouldn't think the drilled head passages flow equally.
10-15-2006, 03:30 AM
#5
Burning Brakes
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As Bill says, a very old-school (read: highly likely to get you the express train to frag-town) way of doing business.
As Ken mentions, the cold start does not equally enrich all cylinders. By a long shot.
It is slightly more likely to get an even distribution mounting the "5th injector" (or 9th as we're calling them here) in the plenum. It's much akin to that half-assed POS known as throttle body injection. The plenum is certainley better than the stock location, but it really can't deliver fuel evenly enough.
The best thing is to (appropriately) calculate your fuel needs via calculation of fuel desired including your desired air/fuel ratio on boost. (It varies by engine setup, but somewhere in the 12:1 ratio is a good ballpark.) Then you can either up injector, or solve via management.
At 6PSI, you really don't need a whole lot more injector, but you should either rescale your fuel pressure or pulsewidths to accomodate the new needs of the engine while on boost.
Dyno and WBO2.
Or,drive around with a management scheme that has a learning algorithm - which it appears the Sharktuner does (but it seems to be for LH only).
Greg
As Ken mentions, the cold start does not equally enrich all cylinders. By a long shot.
It is slightly more likely to get an even distribution mounting the "5th injector" (or 9th as we're calling them here) in the plenum. It's much akin to that half-assed POS known as throttle body injection. The plenum is certainley better than the stock location, but it really can't deliver fuel evenly enough.
The best thing is to (appropriately) calculate your fuel needs via calculation of fuel desired including your desired air/fuel ratio on boost. (It varies by engine setup, but somewhere in the 12:1 ratio is a good ballpark.) Then you can either up injector, or solve via management.
At 6PSI, you really don't need a whole lot more injector, but you should either rescale your fuel pressure or pulsewidths to accomodate the new needs of the engine while on boost.
Dyno and WBO2.
Or,drive around with a management scheme that has a learning algorithm - which it appears the Sharktuner does (but it seems to be for LH only).
Greg
10-15-2006, 09:47 AM
#6
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On the L Jet the 9th injector (used for cold start fuel enrichment) is plumed into a Y pipe. Each side of the pipe enters the head from the back. Each head is drilled to deliver the fuel right above the intake valve. It reminds me if the old AIR injection system for GM air pump emissions.
Seeing how their's no fuel regulator I guess the front cylinders could run leaner than the rear, but I bet it would be marginal.
I don't think activating the 9th injector could soley support a 100hp shot or 10# of boost.
The reason why I ask is I'm currently using 24lbs injectors with 6# boost. Fuel pressure max from the FMU is 90 psi. I want to go to 9 # of boost. Activating the 9th injector hopefully would keep me in the 12:1 ratio.
If I install 30# injectors, not sure if the L Jet would keep the idle quality. Has anyone tried bigger injectors in the L Jet?
Seeing how their's no fuel regulator I guess the front cylinders could run leaner than the rear, but I bet it would be marginal.
I don't think activating the 9th injector could soley support a 100hp shot or 10# of boost.
The reason why I ask is I'm currently using 24lbs injectors with 6# boost. Fuel pressure max from the FMU is 90 psi. I want to go to 9 # of boost. Activating the 9th injector hopefully would keep me in the 12:1 ratio.
If I install 30# injectors, not sure if the L Jet would keep the idle quality. Has anyone tried bigger injectors in the L Jet?
10-15-2006, 11:03 AM
#7
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Hi 
On my NOS system....I use what used to be the AAV at front of plenum for my 9th Injector..The 16 valve engine does not need the auxillary air valve (it only increases idle by adding air when engine is cold)
I find it the perfect place BUT...Nitrous runs at 950 psi and it carries the extra fuel with it...if you just added fuel from the fuel rail there I am not sure you would have enough fuel pressure to do what Nitrous does.....i.e. my nos and fuel BLASTS across and enters the normal air/fuel column as it comes up from the throttle body before it enters the 8 spider legs...
I suspect if you did that with fuel only.....you would only get enough extra fuel to the front 4 cylinders...
All the best Brett
PORSCHE 928 S2 AUTO V8 4.7 LTR 1986 IRIS METALLIC BLUE WITH X-PIPES ,RMB ,PROMAX CHIPS, KICKDOWN SWITCH, K&N, WIZARDS OF NOS - NITROUS KIT 150 HP JETTING - 505 BHP / 500 FT LBS TORQUE
PCGB UK 928 FORUM MODERATOR - Email managingdirector@pchealthcare.co.uk
On my NOS system....I use what used to be the AAV at front of plenum for my 9th Injector..The 16 valve engine does not need the auxillary air valve (it only increases idle by adding air when engine is cold)
I find it the perfect place BUT...Nitrous runs at 950 psi and it carries the extra fuel with it...if you just added fuel from the fuel rail there I am not sure you would have enough fuel pressure to do what Nitrous does.....i.e. my nos and fuel BLASTS across and enters the normal air/fuel column as it comes up from the throttle body before it enters the 8 spider legs...
I suspect if you did that with fuel only.....you would only get enough extra fuel to the front 4 cylinders...
All the best Brett
PORSCHE 928 S2 AUTO V8 4.7 LTR 1986 IRIS METALLIC BLUE WITH X-PIPES ,RMB ,PROMAX CHIPS, KICKDOWN SWITCH, K&N, WIZARDS OF NOS - NITROUS KIT 150 HP JETTING - 505 BHP / 500 FT LBS TORQUE
PCGB UK 928 FORUM MODERATOR - Email managingdirector@pchealthcare.co.uk
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10-15-2006, 02:36 PM
#8
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the aux air valve with fuel injector feeds the plennum, so there is no issue of feeding any cylinders any differently, right? anyway, i think the question is , how will the fuel make it to the plennum. its fed by the air valve with a slow "leak" if you will, to increase idle. Is the injector just a shot of air, or does it run continous? my bet, is that its just a quick shot .. if we knew what the flow rates were, maybe we could make another air valve witih a larger solinoid controled air hole
Mk
Mk
10-15-2006, 06:08 PM
#9
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We're getting away from my question. The 9th fuel injector is already: supplied fuel, wired, and plumed in such a way that all eight cylinders will recieve same amount of xtra fuel delivery.
My question is how much more fuel does it deliver? Will it richen up A/F from 13 to 12:1?
My question is how much more fuel does it deliver? Will it richen up A/F from 13 to 12:1?
10-15-2006, 06:53 PM
#10
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I bet if you could wire it up in parallel with the other injectors, you may get 1/8th more full (.15%) certainly would be worth a try, if the injector is the same. however, i would imagine it is not. can you fit that injector with a real injector? i forgot what it looks like. ive tossed a few of those systems away.
I would imagine its some kind of injector that is a fraction of the normal injector flow rates.
MK
I would imagine its some kind of injector that is a fraction of the normal injector flow rates.
MK
Originally Posted by toofast928
We're getting away from my question. The 9th fuel injector is already: supplied fuel, wired, and plumed in such a way that all eight cylinders will recieve same amount of xtra fuel delivery.
My question is how much more fuel does it deliver? Will it richen up A/F from 13 to 12:1?
My question is how much more fuel does it deliver? Will it richen up A/F from 13 to 12:1?
10-15-2006, 08:00 PM
#11
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The 5th injector, or "9th" as we have renamed it here (I don't make this stuff up, really. The enrichen injector has been called the "5th injector" regardless of number of cylinders since the mid 70's. But I digress...)
As MK mentions, the bonus 5/9th injector is not of the same flow or atomization pattern as the other injectors.
Regardless, don't believe me. Build up a set of headers that have 8 WBO2 sensors in them. Put the car on the street or the dyno. Activate that warm up enrichment injector. Look at the resultant a/f datalogs. I *guarantee* you will see that the fuel does NOT feed all 8 cyls evenly through that system.
I'd bet lots on that one - only because I've done that experiment and know the outcome.
Can you get away with it? Hmmm. 9PSI? Maybe IF intercooled. You have a RoW intake and TB, so can I assume you are running a centrifugal? If you are, what kind of intercooling are you using? What are your in/out temps?
If you don't have some sort of intercooler, may I suggest that you get that done first? Loads of free HP. No increase in boost. Also, I would *strongly* advise against more than 6PSI without some sort of charge cooling. Just is a HORRIBLE thing to do to an engine. And the engine will punish you for doing it.
What is your current a/f ratio on boost? This is a critical piece of data that I would really need to see. Just WBO2 and data log a quick dyno run 1000-6200 rpms will do. Main thing is a/f, but if you can get them to throw an electronic fuel pressure guage output and log it at the same time that would be ideal. Oh yeah, and IAT and EGT would be useful too. As well as your horsepower goal for this project. Crank or WHP, either will do.
If you want the car to be driveable off boost with larger injectors you can either run MegaSquirt (or whatever management you want) or you can run a signal interceptor/modifier that runs when the boost is off.
Properly sizing injectors is a matter of math. It is not a frackin' black art, anyone who tells you otherwise either does not understand EFI, or is a hustler. Don't get me wrong, like cams or suspension setup, everybody has their area of expertise, but it is established science.
Plug in the variables and come out with an injector that is close enough in size to be tuned by your EFI.
Greg
As MK mentions, the bonus 5/9th injector is not of the same flow or atomization pattern as the other injectors.
Regardless, don't believe me. Build up a set of headers that have 8 WBO2 sensors in them. Put the car on the street or the dyno. Activate that warm up enrichment injector. Look at the resultant a/f datalogs. I *guarantee* you will see that the fuel does NOT feed all 8 cyls evenly through that system.
I'd bet lots on that one - only because I've done that experiment and know the outcome.
Can you get away with it? Hmmm. 9PSI? Maybe IF intercooled. You have a RoW intake and TB, so can I assume you are running a centrifugal? If you are, what kind of intercooling are you using? What are your in/out temps?
If you don't have some sort of intercooler, may I suggest that you get that done first? Loads of free HP. No increase in boost. Also, I would *strongly* advise against more than 6PSI without some sort of charge cooling. Just is a HORRIBLE thing to do to an engine. And the engine will punish you for doing it.
What is your current a/f ratio on boost? This is a critical piece of data that I would really need to see. Just WBO2 and data log a quick dyno run 1000-6200 rpms will do. Main thing is a/f, but if you can get them to throw an electronic fuel pressure guage output and log it at the same time that would be ideal. Oh yeah, and IAT and EGT would be useful too. As well as your horsepower goal for this project. Crank or WHP, either will do.
If you want the car to be driveable off boost with larger injectors you can either run MegaSquirt (or whatever management you want) or you can run a signal interceptor/modifier that runs when the boost is off.
Properly sizing injectors is a matter of math. It is not a frackin' black art, anyone who tells you otherwise either does not understand EFI, or is a hustler. Don't get me wrong, like cams or suspension setup, everybody has their area of expertise, but it is established science.
Plug in the variables and come out with an injector that is close enough in size to be tuned by your EFI.
Greg
10-15-2006, 08:49 PM
#12
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Thanks guys. Non-intercooled right now. That's the winter project.
I'm planning on a dyno run in two weeks. Your right Greg, need to find out where the A/F ratio is exactly.
I'm planning on a dyno run in two weeks. Your right Greg, need to find out where the A/F ratio is exactly.
10-15-2006, 11:18 PM
#13
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If it were me, I would focus on the intercooler first.
Really simply put, an intercooler is good for 15-30%+ more power. At the same boost. With less stress on the engine. Low money (~$600 parts) and high return on investment. Other than a bit o cash and some extra plumbing, there are no downsides. Only positives.
One can get away without intercooling at very low boost levels with something very adiabatically efficient like a centrifugal or a twin-screw. Personally though, I will not boost a car to any level without some form of charge cooler, but that's just me.
Do make sure that since you apparently still have cats, that they don't try to do your a/f ratio by sticking a WBO2 probe in the end of the tailpipe. After the cats treat the exhaust, the O2 levels change, making that data absolute garbage. Either have another bung welded in pre-cat, or you can get a WBO2 that will replace the factory sensor and ouput like a narrowband to the L-jet.
(I run the Innovate unit unit on my sometime L, sometimes Megasquirted 84)
Greg
Really simply put, an intercooler is good for 15-30%+ more power. At the same boost. With less stress on the engine. Low money (~$600 parts) and high return on investment. Other than a bit o cash and some extra plumbing, there are no downsides. Only positives.
One can get away without intercooling at very low boost levels with something very adiabatically efficient like a centrifugal or a twin-screw. Personally though, I will not boost a car to any level without some form of charge cooler, but that's just me.
Do make sure that since you apparently still have cats, that they don't try to do your a/f ratio by sticking a WBO2 probe in the end of the tailpipe. After the cats treat the exhaust, the O2 levels change, making that data absolute garbage. Either have another bung welded in pre-cat, or you can get a WBO2 that will replace the factory sensor and ouput like a narrowband to the L-jet.
(I run the Innovate unit unit on my sometime L, sometimes Megasquirted 84)
Greg
