Rance sold me 30# injectors. Eli at Accel seems convinced based on simluation tests, and calculations he did on my ECM while it was there that these injectors are 24#. I think this is an issue that I need to get clarity on. Any opinions about how this could effect tuning and drivability etc. How big an issue would this be in relation to the problems I have been experiencing? I am kind of suspecting I will find a few more issues such as this as I continue to investigate things further. I don;t intend to give up on this. I will prevail here. This is the only car project I have ever done in over 40 years of car building that has been bumpy, so to speak.
Sam

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Do you know who made the injectors?
Do they have some kind of part number on them?

I will check on that. I should have a receipt filed away. I seem to remember that the injectors are made by Bosch, and packaged in Accel boxes, but it has been at leat two years since I took them out of the box. It's pretty cold out in the garage right now, but I will don my long johns and venture out there tonight after work. Eli thought there could be a problem with the fuel pressure that was causing the low fuel flow. The gauge measures the correct pressure, but the gauge could be reading wrong. Everything is kind of on the table, and needs to be checked out.

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That would suck if you had 24#. Might be enough, but could be maxing out a a low-ish RPM/load. I assume you have checked duty cycle? If that is not too high (above 85%), then you're fine. You should be able to datalog duty cycle.

Lou

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Home of Slant6-powered fun machines since 1988

If the computer thinks it has 30# injectors and they're 24# injectors you'd be running alot leaner than the computer thinks it is..................

This would explain to some degree the rich tables and the backing out of the advance........

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

When I asked Eli how the program used the number for the injector size in it's calculations he simply wrote back and said if the config file still has 30# in it, change it to 24#. No explanation. I kind of felt like the stories kids used to tell about being in parochial school. This was typical of the kind of "explanations" I have been getting all along. I will kind of start from scratch here, and check everything out in the fuel system, including the fuel pressure gauge. Lou, do you know if the Mega Squirt uses the injector size in it's math? Do you recall how it uses it? I cannot remember specifying that in the config file. Maybe that was a part of the req-fuel calculations? I cannot remember.
Sam

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Yes, Req_Fuel parameter is based on # of injectors, size of injectors, # of squirts, if you want the banks to alternate pulse or simultaneous pulse and a few other parameters.

I don't recall the exact formula but it is in the megamanual.

I'm not sure if Accel DFI uses a pulse width based table or a VE based table for fuel. If it's pulse width based, the size of the injectors doesn't matter. If it is VE based, the system will have some sort of base pulse width (in Megsaquirt, it's Req_Fuel) determined by the injector size, engine size, and number of injectors - possibly some other traits like the fuel type, too. Setting the injector size too high will make for too short a pulse width, so you would have to set the VE table numbers too high to compensate.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

So whatever the cause of the apparent low flow, whether injector size, or fuel pressure, the Mega Squirt would have been fouled up as well. I feel like I am begining to get somewhere. There had to be some reason this car never ran as well as I anticipated when putting it together. It ran, but never the way I expected, nor as EFI like. It never seemed to have the maners I expected, or the power. It is still too cold out there to work. It is in the teens this morning. But it is not too cold to start gathering informtion, and material. I plan to re-rout the fuel line, place the regulator on the output side of the fuel rail, and re-route the inner cooler tubes this Spring.

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Accel uses a VE table fuel map. Right from the start, Eli was telling me I was giving the engine too much fuel, based on what he was seeing in the VE tables. At least this is something to work on now. Does anyone know how reliable these little liquid filled fuel pressure gauges are? If this is wrong, then I am off base from the git-go. Does anyone out there have a formulation for how much horseposer 6 24# injectors should support? This engine should be capable of around 300 HP if everything gets worked out. Maybe 24's are big enough if the calibration is done correctly. Maybe I should have the injectors flowed to see what they actually are. If they are 30's then the fuel pressure is the supected culprit.

In one of my books, and I think it is Maximim Boost, they recommend putting a temporary fuel pressure gauge up on the windshield so you can see it while tuning, and driving. But now I am wondering how you know if you can trust them. I would like opinions here about the best way to calibrate the pressure regulator. It is vacuum referenced.
Sam

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Well first things first. You meantioned moving the regulator to the output side of the fuel rail. If this is not already like this how in the world is the fuel injectors getting a regulated pressure. This makes no sense but maybe I am just thinking about it all wrong & am missunderstanding the meaning of your statment. But if the reg is before the rail & then the rail goes to return line then you have a problem. Maybe you dont have a return fuel line system & that is the reason.


I have meantioned this before. Your injectors are to small. Even if they flow #30 as you have been told they are to small. If they are #30 they are on the very edge of being able to supply the right fuel & that would be with all other things being in line as it should be. I would go with a set of #44 injectors for that setup ( and thats if I didnt expect to run it at higher power than 350hp). The thing about buying new injectors is its going to cost about the same wether getting #44 or #60. In that case I would go ahead and get the #60 ( which are available at good pricing & in stock at most places because of the Buick GN's) #60 run good for the Buick guys & idle quality is not effected in any way. This will also leave you room to grow in the future. But you also see many Buick guys selling used injectors ( A lot of #50 around) At the right price & a person that you could trust this would be OK. If buying new get the 60's. Your setup should make more than 300hp if it was working right.


The calculations for a 300hp 6cyl for injectors comes to a #32 injector with the proper fuel system that can give one pound of pressure rise for one pound of boost. In other words at 15lb of boost you should be running 60lb of fuel pressure when at the 15lb of boost & 45 at idle with no vacume line attacted.


Most fuel gauges are pretty good about being accurate. That being said it is good to compair it against a know good gauge for referance. BUT. I have seen many bad gauges & if its been knocked around (droped or hit, or is a cheap gauge) the possiblity of it reading off are good.



Jess

The return line is from the back side of the regulator. The fuel rail is open to the fuel system only on the inlet side. There is no outlet side. The gauge is on the end which would normally be the outlet side. IN theory, everything from the regulator on is at regulated pressure, and the regulator bleeds off excess back to the surge tank. If the surge tank gets full, then the excess there goes back to the fuel tank in the back. I didn;t make this up. It is designed by guys who build off road suvs and jeeps and such, and add a surge tank so they still pick up fuel even when the truck is pointing nearly straight up, down or sideways.

Jess,. would you share your recommended fuel pressure setting, and be very specific about whether the vacuum line is hooked up, and how much pressure i should see when the vacuum line is unhooked, and how much I should see when it is hooked up.

Is everyone in agreement with the injector size mentioned by Jess. I remember Rance saying that 6 injectors @30# would sustain 450 HP. I don;t know where he got that.
Sam

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http://www.vintagewatercooleds.com/tech ... s/hpfp.gif

Does your fuel system layout look basically like this? If not what exactly is different?

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Nitrous cars are like old men on Viagra. Once the bottle is empty they are useless.
FJD

Tom, I can, and will make it just like that, if you recommend it. But I think I would need to buy a different regulator. I don't want to change it if what I currently have is fine. Eli seemed to think that it should be OK. The fuel rail is a dead end. The in let to the fuel rail tee's off of the fuel regulator. My regulator has three openings, and is between the fuel rail and the pump. . One of the openings is the inlet, one is the return and the other is the outlet to the fuel rail. Of course there is the vacuum line also.



I hope I did not make that explanation too complicated. I got this fuel regulator from Rance, and was a little confused by it myself, but he recommended the plumbing I now have. I am learning here that little things can have unexpected consequences, and then end up biting you in the rear.

As I said, everything is on the table for scrutiny and possible alteration at this point. I was doing what was recommended by experts all along the way, and am learning that opinions vary, and how different configurations work will vary depending upon the total package. So comments and recommendations are really welcome now. What thoughts are there out there on this pressure regulator, return line arrangment issue. I will go to the other EFI websites and look around for opinions as well.
Sam

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Sam, the system you described is basically what the newer Mopars have been using. The regulator is mounted in or near the fuel tank, and the fuel rail and most of the fuel line is at operating pressure. Your system should work just fine, so long as everything else is tuned for it.

I would think the 60# injectors might be a tad overkill, and would favor the 50#ers myself. The only issue is can you get a clean idle with that large of an injector with your controller. If you can, then there would be no reason not to use them. It takes a minimum pulsewidth to activate the injector, and if the 60#ers can be throttled down to your idle needs, then you're OK.

Mike

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Recognized by US Federal Courts as a Fuel Economy Expert!