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GasGunR
05-02-2008, 04:25 PM
I'd like to see a test performed to determine if a front cross over on the fuel rails is helpful or needed in order to prevent fuel starvation of the number 1 cylinder.

Test 1. Flow match 8 injectors, preferably some of the bigger guys like Blue Giants or Purple SRT-4s.

Test 2. Flow test a complete set, (pair) of stock rails and the injectors from test one with the stock fuel rail inlet and rear cross over.

Test 3. Flow test a complete set, (pair) of aftermarket rails and the injectors from test 1 with a rear center feed fuel line.

Test 4. Flow test a complete set, (pair) of aftermarket injectors from test 1 with a rear center feed fuel line and front cross over line.

Preferably the test would run for several minutes in order to add accuracy to the test quantities.

Thanks,

Don

roswald0511
05-07-2008, 11:41 AM
Damn good idea

JonW
05-07-2008, 12:05 PM
Due to the pressure of the fuel system, you need the injectors mounted into the rails and then either attached to the manifold or inserted into a test stand that can be secured. The easiest way I can see for you to do this is to have an intake manifold off of the vehicle and have it positioned above a set of 8 graduated cylinders. You will also need to use a pump with a regulator so you can dial it up to 59 psi. You will then need a set of injector drivers to run all 8 injectors simultaneously.

mhigham
05-08-2008, 03:06 PM
Testing flow you can just wire the injectors for power and run 100% duty cycle. Not the best for the injectors, get a donor set.

We run mineral spirits for tests like that.

Mike

GasGunR
05-12-2008, 04:36 PM
I think this is worth fabbing a test stand designed to hold the rails over graduated cylinders.

There has been enough unproven conjecture about the number 1 injector being short on fuel. This test will prove or dispell that theory.

GasGunR
05-20-2008, 08:25 PM
Update... Billet Technology has graciously offered their fuel rail pressure test fixture for modification to do this test.

It would be nice if Jason or Matt would post up here and let us know if this test might be on the list.

Also folks, hopefully the rest of you guys have been thinking of things that need to be tested during this MOFO. Please give it some thought and post your rideas up in this forum for discussion. Jason / Matt, if you'd rather have them posted elsewhere let us know where.

Thanks!

Don

Super T
05-20-2008, 08:40 PM
Silly idea... Stuff pipes/tubes/whatever into the injector ports of the rails... copper, plastic, steel, glass, whatever, as long as they seal. In said tubes, install tees with pressure transducers. At the ends of the tubes, cap them and drill small holes to choke the flow down to something resembling what the injectors might take at 100% duty cycle on a big horse engine. It would be a pretty friggin small hole. But then all you have to do is measure the pressure in each tube to determine whether the flow is unequal (pressure differentials are what make fluid flow... well that plus gravity, but we know that one will be constant on all 8 tubes... at least I hope it will...).

Pressure transducers are a lot cheaper and more readily available than any flow measuring device... I don't even know where to get a flow measuring device that can measure the low quantities we're talking about here. Plus this would save us having to buy injectors.

Thoughts? If nothing else, go this route w/ pressure transducers and then stick injectors at the ends of the tubes... that way you have the most accurate flow rates possible but you still have the ease of measurement. The tubes can be turned on a lathe or whatever needs done to make them nearly identical and reduce the possible introduced error.

Cam
05-20-2008, 08:45 PM
Thoughts??................yup, take a look at your plugs...........whatta ya think of that :)

Blown7
05-20-2008, 08:55 PM
Well you have to remember also only 2 injectors are firing on opposite banks in sequence and the PCM will modify the timing of the injector pulsewidth to not create standing pressure waves in the fuelrail.

So my question is how can you duplicate the test to match the PCM injector pulsewidths and internal timing???


Jeff

GasGunR
05-20-2008, 09:00 PM
Frankly I think it sucks. Doesn't tell you if its an injector, a fuel rail pressure problem or an intake head combination that moves more air to one cylinder.
Thoughts??................yup, take a look at your plugs...........whatta ya think of that :)

GasGunR
05-20-2008, 09:10 PM
WHy do all that when all you need is a set of injectors, which I'm sure we can come up with... I'll loan a set of Blue Giants if necessary.

You and I know that it would take a huge pressure differential differnce to significantly affect flow as the flow will only change at the square root of the pressure change, but it would be easier to convey to those not interested in learning pump laws by just using graduated containers wouldn't it? No reason for fancy flow measuring devices.

I think the test as laid out above with all 8 injectors fllowing 100% duty cycle at the same time will speak volumes, (pun intended). A simple test, no reason to get complicated unless - the test shows there is a shortage of flow to cylinder #1 and we want to see what the actual limits are. I doubt that will happen, but who knows unless we do the test?


Silly idea... Stuff pipes/tubes/whatever into the injector ports of the rails... copper, plastic, steel, glass, whatever, as long as they seal. In said tubes, install tees with pressure transducers. At the ends of the tubes, cap them and drill small holes to choke the flow down to something resembling what the injectors might take at 100% duty cycle on a big horse engine. It would be a pretty friggin small hole. But then all you have to do is measure the pressure in each tube to determine whether the flow is unequal (pressure differentials are what make fluid flow... well that plus gravity, but we know that one will be constant on all 8 tubes... at least I hope it will...).

Pressure transducers are a lot cheaper and more readily available than any flow measuring device... I don't even know where to get a flow measuring device that can measure the low quantities we're talking about here. Plus this would save us having to buy injectors.

Thoughts? If nothing else, go this route w/ pressure transducers and then stick injectors at the ends of the tubes... that way you have the most accurate flow rates possible but you still have the ease of measurement. The tubes can be turned on a lathe or whatever needs done to make them nearly identical and reduce the possible introduced error.

Super T
05-20-2008, 09:14 PM
Well you have to remember also only 2 injectors are firing on opposite banks in sequence and the PCM will modify the timing of the injector pulsewidth to not create standing pressure waves in the fuelrail.

So my question is how can you duplicate the test to match the PCM injector pulsewidths and internal timing???


Jeff


I don't believe the car controls the injector timing as a function of anything, only the pulse width (aka duration). And that's more or less fixed at WOT for a given tune. True you only fire 2 at at time on the car... but the hardware to duplicate that in a test would cost mucho dinero. The injectors are open/close, they don't modulate, so you can't use a controlled voltage to simulate 1/4 flow in all injectors (same as full flow in one).

I think if a certain cylinder has trouble keeping up, running all 8 @ 100% would exaggerate the problem and make it more pronounced, at least verifying that there is indeed a problem. If you wanted to, you could take the required flow rate for, say, 600 horsepower, and find injectors that flow 1/4 of that. Since the object of the test is the rail setup, not the injectors, this might be a viable alternative.

GasGunR
05-20-2008, 09:29 PM
Or you could just put power to one, two or three injectors perside at a time... engineers always complicating things;)

Super T
05-20-2008, 09:47 PM
Or you could just put power to one, two or three injectors perside at a time... engineers always complicating things;)

Yes you could. But I believe that all four flowing more closely simulates real life conditions. At, say, 6000 RPM, each injector is firing once every other revolution, so 3000 times per minute, or 50 times per second. Since it would be cost prohibitive (unless someone has ideas on actually controlling the injectors a la PCM) to get "real" flow that would have the rapid fluctuations of an in-service system, I would say that, at 50 times a second staggered across four injectors on a rail, constant flow through them would be the closest approximation. I dunno, maybe not. The effect of the pulsing pressure would depend on the velocity of the fuel in the rail.

There's a though... at the back of rail 1 (drivers side), the rail is carrying four injectors worth of flow, while at the front, it's only carrying one cylinder worth. That means the average velocity at the back of the rail would be four times that at the front. Granted, even that should be a very low velocity since the rails should act basically as fuel plenums. But maybe they don't...

Hemi31
06-10-2008, 06:20 AM
Well,we saw some proof while tuning my car but nothing that would be believed here.The fuel trims from the right and left bank were uneven with the stock rails in place and after the new rails and crossovers went on they evened up.Now I know thats not a pressure and flow test like you guys want but it is another piece of evidence that a balance tube makes a difference.At least on a modded motor.

Midnightsun300c
07-04-2008, 09:48 PM
I'd like to see a test performed to determine if a front cross over on the fuel rails is helpful or needed in order to prevent fuel starvation of the number 1 cylinder.

I think it a good question in its own right as it applies to stock vehicles. I wonder if we need to first consider what vehicles experienced the problem? Build date, model, engine, etc. If this was a problem on stock vehicles has Chrysler found it and fixed it already? We may get varying results with different build dates?

Also, does the test need to be performed with G force applied to truly test the crossover feed? Could the pressure and delivery be OK under "normal" or bench test conditions but could the length of plumbing combined with the G force during maximum acceleration starve that most distant cylinder?

JonzMgnm
07-04-2008, 09:51 PM
Also, does the test need to be performed with G force applied to truly test the crossover feed? Could the pressure and delivery be OK under "normal" or bench test conditions but could the length of plumbing combined with the G force during maximum acceleration starve that most distant cylinder?

At approximately 58 psi, I don't think it matters much in regards to G forces.

Midnightsun300c
07-05-2008, 03:34 AM
At approximately 58 psi, I don't think it matters much in regards to G forces.
You know, that was my initial thought as we would only be taking a couple psi but if you're on the edge it could make the difference. As in, if 54 psi is just enough to supply the right amount of fuel at the current jet size and pulse duration, if you back that off by a couple psi, just for a second before the regulator can do its job, you could have a problem. Especially when you consider the pump is way back under the back seat, at least on my C. That's a long way and a lot of twists for fuel to get pushed when the acceleration is pushing it back as well. Heck, I don't even know how many "G's" I can pull at launch. I would guess close to one? Someone using a high stall converter and DRs may be getting two? I'm more asking than anything, is it something to consider? I'm thinking it might be if the No. 1 cylinder is just getting enough as it is, and I think we are considering this is indeed the case if we are considering that the routing of the fuel from the back or mid rail would make a difference to begin with.

GasGunR
07-16-2008, 09:49 PM
a couple pounds of pressure doesn't mean much... the flow changes at the square root of the pressure change.

RobAGD
07-16-2008, 10:31 PM
Well on my set up now, I see a 6 psi drop at WOT

5.7 Hell fire, Street/Strip Heads, AEM, Cats, Zoomers, AH

Ford 39#'s

W/ BT Rails, and even rear and front cross overs.

Just an little fyi

-R

Johnparts
07-16-2008, 10:41 PM
Well Guys I just worked out a new set-up on our big cube blower motor with a boost referenced fuel pressure regulator and a return completely bypassing the stock fuel system and as soon as I get the car put back together (waiting on the blower) I'll show you all my pressure findings But at idle I should have 45 lbs under no vacuum I have 60 lbs and under 5 psi simulated boost I have 70 lbs with a desired boost of 8 psi I hope to have 80 lbs with BT rails and a front crossover. Should support 15 psi and 1000 hp no problem. With flow rates on the pump of 255 gph (gallons per hour)she should keep from ever getting lean on any cylinder

Redfox0099
07-16-2008, 10:43 PM
How are you reading the pressure drop Rob?

RobAGD
07-17-2008, 12:12 PM
Nate - I have a Autometer Cobalt 0-100 psi Fuel pressure guage in the car, it sit right at 59/60 psi all the time except at WOT.

If you look into my fuelish thinking thread you will see that adding that to the system was one of my small headaches but well worth it in the long run.

-R

Redfox0099
07-17-2008, 04:21 PM
I will add this as I do not know if it is important but maybe it is.

I have the upgraded Digital Controller for my Water/Methanol kit and from it I can tune the spray of the W/M.

Not only that though it also shows Injector duty cycle and Injector Pulse Width in milliseconds so I don't know if it would be helpful but maybe having one of these there would give information that might be useful???


http://i7.photobucket.com/albums/y284/redfox0099/Magnum/Water-Methanol/VCS3G_sm.jpg

Midnightsun300c
07-18-2008, 01:08 AM
Well on my set up now, I see a 6 psi drop at WOT

5.7 Hell fire, Street/Strip Heads, AEM, Cats, Zoomers, AH

Ford 39#'s

W/ BT Rails, and even rear and front cross overs.

Just an little fyi

-R
Outstanding information! That is more that I would have guessed, but it was a wild a$$ guess based on some simple conversions. Does the regulator eventually bump the pressure back to 59 psi after a second or two? How many Gs would you guess you're pulling? Have you noticed more of a pressure drop out of the hole when the Gs would be the most, or is it more to do with fuel flow than Gs?

Redfox0099
07-18-2008, 04:38 AM
RobAGD if you see 6 PSI drop on the "upgraded" setup I wonder what your drop in pressure was on the stock rails?

Hemi31
07-18-2008, 06:15 AM
RobAGD if you see 6 PSI drop on the "upgraded" setup I wonder what your drop in pressure was on the stock rails?Probably would have been the same.The upgraded rails and lines won't effect overall pressure but will effect where the the pressure is.
The only way to effect the rail pressure is a new fuel line and possibly a new pump.Even with a Boost-A-Pump I still have massive pressure drop trying to squeeze it through that 5/16 line.

Redfox0099
07-18-2008, 06:59 AM
So for a boosted application the fuel rail upgrade is advised....but for the rest of us is it just eyecandy?

Hemi31
07-18-2008, 08:02 AM
I like the fuel rail upgrade because I feel it balances out the pressure to all the injectors Nathan......there is constant pressure to all.I think anyone running larger than stock injectors should do it IMO.But the boosted guys with cams,heads and 8psi or over need to log pulse width and then consider pump and line upgrades if need be.

Johnparts
07-18-2008, 08:16 AM
yeah the stock 5/16th line wont feed a hungry baby let alone a boosted stroker. Call Aeromotive and ask to talk to a tech engineer they will lay it all out for you. I went with a -8 line on our new system and if I had to go over 7000 rpm I would have gone to -10 line. But with a 60 lb fuel system you want to maintain that 60 lb throughout the rpm range and as rpm increases demand does as well. Imagine it like this at 6400 RPM your injectors fire 51200 times a minute feeding 53 cubic inches per cylinder (a geo metro 3 cylinder) that takes fuel.

Redfox0099
07-18-2008, 08:23 AM
Can we replace the stock fuel line with a bigger one from the tank up to the front....somewhat easily and not horribly costly?

lafrad
07-18-2008, 08:51 AM
A returnless fuel system like we have in the LX/Jeep/Mopar world today relies on a fuel pressure regulator in the fuel tank. It is a fixed regulator with no control to change fuel pressures.

The properties of fluid flowing through tubing, with restrictions like "injectors" limiting fuel flow *guarentee* that the fuel pressure at the fuel injectors WILL BE LESS than the fuel pressure at the outlet of the regulator. This is due to the fact that fuel flowing THROUGH a tube encounters resistance... which is generally influenced by the size & length of the tubing. The more fuel flow you demand, the more the pressure drops. In Rob's case, 6 PSI does NOT seem like a huge problem. In Hemi31's case, the pressure drop is so significant that the injectors can no longer efficiently inject fuel into the boosted pressure of the manifold.

The PCM has tables within that estimate the fuel pressure drop of the system, and adjust injector pulsewidths accordingly. The R/T and SRT have slightly different calculations, for which I have not followed up to figure out "why".

Also availble in the tuning, is the ability to adjust the fuel injector timing. The systems available to the LX computers sequentially fire the injectors, with each injector timed to the cylinder it is injecting fuel for. There is 720 degrees of control, so it is possible to adjust the timing of the injector to be anywhere within the 4-stroke engine's cycle. The CMR software available can only adjust the "base" injector timing... each injector has specific "offsets" from that "base" timing that are not available to be changed in the CMR.

keep in mind, that, by definition, an injector "injecting" at 80% duty cycle is open 80% of the time. This means, that @ 80% duty cycle, out of 8 injectors, AT LEAST 6 injectors are open at any point in time, and at certian points, 7 will be open. And with a firing order like our hemi's have, its very probable that 4 injectors per bank will be open for significant amounts of time.

If you have a system where there is restriction in the fuel rails, Injectors that are "closer" to the source of the fuel will "bleed off" pressure from the fuel that is going to the next injector in the system. If you are running close to the limits of the capacity of the fuel system, that pressure gradient in the fuel rails could be significant.

lafrad
07-18-2008, 08:53 AM
Can we replace the stock fuel line with a bigger one from the tank up to the front....yes somewhat easily and not horribly costly? only if there is a group by for pre-bent pre-fitted hardline

So, get on that, would ya?

lafrad
07-18-2008, 08:56 AM
I like the fuel rail upgrade because I feel it balances out the pressure to all the injectors Nathan......there is constant pressure to all.I think anyone running larger than stock injectors should do it IMO.But the boosted guys with cams,heads and 8psi or over need to log pulse width and then consider pump and line upgrades if need be.

The "Constant pressure for all" is the most significant part of this. if you can make the "restriction" int he fuel rails essentially zero, that means all cyls will be equally fueled, with little chance that "as you go lean, #1 & 2 go REALLY lean".

Funny part about all of this: is that an oxygen sensor reads an entire "bank" of cyls. So the computer has no idea that the front cyls are leaning out and the back are fattening up... and its happy to run the engine like that until it grenades.

Redfox0099
07-18-2008, 08:56 AM
Um...me?

How about i look at it this weekend.

lafrad
07-18-2008, 08:58 AM
RobAGD if you see 6 PSI drop on the "upgraded" setup I wonder what your drop in pressure was on the stock rails?

I bet he still saw "6psi drop" with stock rails. The major restriction in our fuel systems is the fuel line and fittings between the tank and each metal tube on each bank.

lafrad
07-18-2008, 09:01 AM
Um...me?

How about i look at it this weekend.

yea you! ;-)

I'm just jokin.

Any shop with good tube bending skillz can get you a 3/8 or 7/16 line bent and installed on your car with "not too significant" effort. Problem is getting the 7/16 line properly attached to the factory slip-fitting on the fuel tank (do they sell those things in a form that can attach to hard line?)
On the front, you might as well use a flair fitting to the upgraded fuel rails... that is the least restrictive that you can get.

InferAl
07-18-2008, 09:06 AM
Well on my set up now, I see a 6 psi drop at WOT

5.7 Hell fire, Street/Strip Heads, AEM, Cats, Zoomers, AH

Ford 39#'s

W/ BT Rails, and even rear and front cross overs.

Just an little fyi

-R


I bet he still saw "6psi drop" with stock rails. The major restriction in our fuel systems is the fuel line and fittings between the tank and each metal tube on each bank.

He sees the drop even with hte new setup

lafrad
07-18-2008, 09:09 AM
He sees the drop even with hte new setup

Right,
I'm suggesting that I would expect there to be the SAME pressure drop at the front of the driver-side rail, with or without upgraded rails.

InferAl
07-18-2008, 09:19 AM
I was under the car the other day looking where a -8 line could be run right to the fuel tank, I think it is a 3/8 quick connect fitting on the pump. The line seems to run up from the pass side over the tank, don't know if the tank would have to be dropped or pop up the pump from the back seat and run it down

Hemi31
07-18-2008, 09:22 AM
Right,
I'm suggesting that I would expect there to be the SAME pressure drop at the front of the driver-side rail, with or without upgraded rails.my point is that drop on 1 and 2 cylinder would be much less with the crossover in the front.

Johnparts
07-18-2008, 09:26 AM
The drop is caused by the stock lines not the rails, that and the demand from the pump and regulator assembly it's like sucking though a straw the little straw you get in a cocktail compared to the giant straw you get with a big gulp. This all has been figured out on other cars guys it simple physics and fluid dynamics the stock feed in the tank is 5/16 so even if you open it up after that point you still have the 5/16th restriction even if the line is 1/2 inch

Johnparts
07-18-2008, 09:31 AM
Let me break it to you like this. I built a 1965 Mustang a few years ago with a modern fuel injection system. When the car came to me the motor and trans were in the car running but running poorly. The stock pick-up was in the tank with an external pump pulling through the 5/16 pick-up in the tank. The only upgrade I made to the fuel system besides bigger fuel lines was a 3/8th pick-up in the tank and I increased fuel flow by 30% and the car began running better and became more tunable.

lafrad
07-18-2008, 09:37 AM
The drop is caused by the stock lines not the rails, that and the demand from the pump and regulator assembly it's like sucking though a straw the little straw you get in a cocktail compared to the giant straw you get with a big gulp. This all has been figured out on other cars guys it simple physics and fluid dynamics the stock feed in the tank is 5/16 so even if you open it up after that point you still have the 5/16th restriction even if the line is 1/2 inch

Any restrictions BEFORE the fuel pressure regulator only come into play here if your pump cannot properly supply the pressure needed to keep the Pressure regulator happy.

Also, pressure drop is based on line size AND diameter (well, area).

I would expect a 3/8 or 7/16 line from back to front, after the regulator, to help maintain fuel pressure at *the same fuel flow rate*, in a significant way, with the SAME fuel pump.

I still think a regulator at the rails with a return system is the *absolute best* way to go.

HEMI~C~
12-06-2008, 12:16 PM
Updates to the fuelish thinking thread that may help inform on this subject. Bottom line.... I upgraded the entire fuel line to -8 from the fuel pump to the rail....boost referenced external FPR and filter and still saw a significant fp drop at WOT with my combination....with the Boost A pump at max. No doubt the the fuel line/ext fpr helped improve the situation but the pump became the limiting factor. A second pump was needed.

Chris

richierevs
07-29-2009, 09:07 AM
Updates to the fuelish thinking thread that may help inform on this subject. Bottom line.... I upgraded the entire fuel line to -8 from the fuel pump to the rail....boost referenced external FPR and filter and still saw a significant fp drop at WOT with my combination....with the Boost A pump at max. No doubt the the fuel line/ext fpr helped improve the situation but the pump became the limiting factor. A second pump was needed.

ChrisAssuming that the check valve assembly in the tank is either removed or widened and the fuel line from the tank to the firewall is -6 AN or larger, a secondary pump would need to match the flow rate of the primary pump so that the secondary pump doesn't try to siphon past the primary. If the secondary pump begins to make a high pitched whining noise, a flow restricting siphon condition may exist.

IME if pumps aren't matched and the secondary pump has a higher flow rate (say 255 lph), the BAP will need to remain on the primary to maintain consistent flow rate to the secondary.

It's certainly possible to install another BAP for the secondary pump so long as the voltage feed to both BAPs is the same and the pumps have similar flow rates.

Another alternative is to drop the tank and install a 255 lph (@ 12 volts) pump to alleviate flow restrictions. The BAP can still remain in place but will need to be recalibrated to the higher flow rate.

GasGunR
07-30-2009, 08:41 PM
I guarantee this doens't happen.

If the front cylinders are lean because of fuel flow on these cars, so are the rear.

The biggest pressure drop in the system is the injectors... they have a 58 psi drop across them, therefore the rails are self balancing. I have thousands and thousands of hours of hydronic balancing experience and I've said this over and over, but no one wants to listen. You can red bean me, flame me, say what ever you like, but it won't change the facts.

Now I'll say it again, IF the front cylinders are lean, its because there is more airflow to those cylinders. IF the whole motor is lean, its because of the fuel pump(s) lines and the inability of the system to maintain 58 lbs to the rails, or the injectors are too small.

If the motor is lean, upgrade the fuel system by all means, but forget the idea that there is a fuel balancing problem from one end of the rail to the other. It isn't happening.



The "Constant pressure for all" is the most significant part of this. if you can make the "restriction" int he fuel rails essentially zero, that means all cyls will be equally fueled, with little chance that "as you go lean, #1 & 2 go REALLY lean".

Funny part about all of this: is that an oxygen sensor reads an entire "bank" of cyls. So the computer has no idea that the front cyls are leaning out and the back are fattening up... and its happy to run the engine like that until it grenades.

Hemi31
07-30-2009, 08:49 PM
Don remember the test Jaak did when he said he saw a miniscule pressure drop on the drivers rail?

GasGunR
07-31-2009, 08:24 AM
Vaguely.

I'll say this. The only way to test this on the car would be to build a test manifold so that you could use the same guage to test both ends of one fuel rail with the same guage, under the same operating conditions. But you better bring a pretty fancy guage to the game or you will be measuring pressure differentials lower than the guage's tolerances. Iin other words the guage could have a larger reading error than the real pressure differential from one end of the rail to the other.

There is a reason its usually cylinders 1 & 3 that usually pop, but its not likely fuel. Airflow maybe, some other tolerance in manufacturing like water jackets perhaps, but it isn't a difference of fuel delivery between cylinders 1, 3, 5, & 7. If there is a piston failing on the left side because it is lean from lack of fuel, it would just as likely be 7 as 1. That's all I'm saying.

Has anyone ever flow benched a set of heads with the intake manifold attached? Differences of airflow at the low pressures involved are much more likely than fuel flow in a particular bank.

Hemi31
07-31-2009, 08:41 AM
most pooped motors will be 1,3,5,7 Don.....not just 1.
now what I wanted to mention in regards to jaaks test was he saw a minor drop on the drivers side rail....tiny even...which would have been fine,but he realized his pressure transducers maxed out at 46psi......now in my mind if they maxed out at 46 psi and he still saw a drop on the drivers side rail that would be a problem considering we have a 59psi system and even at WOT we see over 50psi at the rail.

Posted via LXFMobile

RobAGD
07-31-2009, 02:09 PM
http://www.lxforums.com/board/showpost.php?p=1853406&postcount=103

here is my graph this is after cross over addition. stock supply line.

http://www.robagd.com/cars/robs/graphs/Cecil-Pass1-SSI4.png

-R

GasGunR
07-31-2009, 03:05 PM
If its the whole bank that is lean, what does the PCM do in response to it? At part throttle wouldn't it pull timing / throttle, limp if if couldn't make the A/F ratio? If its the whole bank, the O2 sensor will see it and the PCM should be doing something to correct it. At WOT isn't the car tuned this way so the injectors have increased their pulse width to keep the A/F ratio correct?

Back to my point, this is NOT what LaFrad said in the post that I quoted above, he stated that there would be a difference in the front cylinders in each back as compared to the rears... that isn't happening, I guarantee it. If one cylinder is short on a rail they are all short.




most pooped motors will be 1,3,5,7 Don.....not just 1.
now what I wanted to mention in regards to jaaks test was he saw a minor drop on the drivers side rail....tiny even...which would have been fine,but he realized his pressure transducers maxed out at 46psi......now in my mind if they maxed out at 46 psi and he still saw a drop on the drivers side rail that would be a problem considering we have a 59psi system and even at WOT we see over 50psi at the rail.

Posted via LXFMobile

GasGunR
07-31-2009, 03:14 PM
From your other thread, you lose 6 psi everytime you go full throttle... that's about a 5% decrease in flow if everything stayed the same... if the car is tuned this way for WOT, won't it just increase the pulse width to compensate and keep the A/F ration correct?


Your chart below confuses me, doesn't it say that as the fuel pressure goes down the mixture gets fatter?


http://www.lxforums.com/board/showpost.php?p=1853406&postcount=103

here is my graph this is after cross over addition. stock supply line.

http://www.robagd.com/cars/robs/graphs/Cecil-Pass1-SSI4.png

-R

RobAGD
07-31-2009, 04:01 PM
Yep, because that is what the commanded AF is for those rpm levels.

The stock system had a known pressure loss and that is accounted for in the factory tunes.

In my instance though, I am only making about 400-415 rwhp and I have not done this test on a 100% stock car, or actually had someone log rail pressure on a highly modded stroker set up.

-R

351Freak
08-02-2009, 09:52 PM
What is very interesting is that at no point was the pressure near the 60 psi that is supposed to be "normal" for these cars...

and...

the fact that the rail pressure dropped at WOT with a crossover in place...

???

Since I know for a fact that the stock pump is more than capable at these flow/pressure rates...it is only logical to come to the conclusion that the pressure drop is coming from the friction loss in the lines themselves...

Which is exactly what we were seeing when I did the flow tests and then the resulting upgrade to the -6 line from the back to the front...

What would be nice to see now would be the same datalog done to a car that has the upgraded fuel lines...

good info...

Beans to Rob...

RobAGD
08-03-2009, 06:14 PM
Thanks Freak, helping HemiC with his fuel system opened my eyes to a lot of things with these cars. I was well on my way to doing the before getting elbow deep into the fuel tanks.

I could test this fairly quickly if I had the -6 line with the ends on it. figure an hour to install and then a few wot passes.

I tapped into my Autometer Fuel pressure setup for logging to my SSI-4 that is also logging my AFR. I am still getting a really crappy tach sig in my setup though...

Did you see a pressure loss at all with the -6 line ?

-R

Lajus007
08-08-2009, 08:56 PM
my turn to play...got all the lines and fittings together...the hat and the pumps have been here for over 2 weeks now....ready to get slapped on..well not so literally but you know what i mean....this should be fun!

RobAGD
08-08-2009, 09:04 PM
If you got the 3 pump hat, never run the gas below 1/4 tank you will kill the pumps w/o the basket.

-R