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Cam differences with EFI

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  • Cam differences with EFI

    Still stumbling around with these systems whether we allow them to learn or try to set AFR's. I think one problem is bungs are too far from the cylinders for the 02 sensors, but when I try to get a cam recommendation, I am getting a 109 centerline cam. The current is 107, the last was 112 and neither made this sniper happy.

    Is there a key to cams with EFI? The sniper with the holley dizzy is controlling timing, seems like a stock cam is about .450 lift and 220 duration.

    The Howards guys just recommended this 109 centerline cam about .290 duration and .530 lift.

    What is the key element, centerline or lift and duration to make EFI happy?

  • #2

    Re: Cam differences with EFI

    I know very little but it was recommended to me to widen the LSA to improve vacuum at idle to improve idle quality. This was with a Holley HP sequential setup.

    Comment


    • #3

      Re: Cam differences with EFI

      What is interesting to me, is I went back to a 67 350, the intake centerline was 105, exhaust centerline 110. roughtly .450 lift and .260 duration.

      We started with the 112 center line with the edelbrock cam about .500 lift close to 300 duration

      The comp we have now is roughly the same as the edelbrock, with a 107 centerline

      Howards is recommending a .530 lift about .290 duration and a 109 centerline.

      When I go ahead to 1995 when TBI were pretty common, light lift, light duration and 116 centerline, but we knew those motors are pigs.

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      • #4

        Re: Cam differences with EFI

        Exactly what sort of ECU is this? You can go nuts with a fully tunable race ECU; if it's a modified stock one, this will depend on just how adjustable it is.

        If the O2 correction parameters are tunable, it's usually not a huge deal if the O2 sensors are far from the cylinders - close to the exhaust exit, like 12-24", is another story. Too close to the exit and you only get a reading once you have enough gas flow to keep ambient air from circulating back in.

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        • #5

          Re: Cam differences with EFI

          We started with the edelbrock e street and their ecu. I was lost with that one immediately because the TPS constantly corrects itself to zero after you adjust the idle screw. We could not do anything with the e street one. Holley has their fully tunable ECU with their software on a laptop, or let it learn on its own. They also have an EFI distributor that allows you to change timing. We are not racing, not stump pulling, just want to enjoy driving it and make sure no little go cart honda with a loud pipe has a chance at the light.

          Edelbrock originally said they would email us a tune based on our setup. That never happened, they just all say let it learn on its own. Neither of them learn to keep us getting at least average mileage, we might as well have left a double pumper on it. So we are pretty much at the point of having a killer motor but no real results, so the question lies in just pulling this lopey rumble stick out and find something these systems want to work with before having another miserable year with a car that should be nothing but fun.

          Comment


          • #6

            Re: Cam differences with EFI

            injection should need no lope to go by the old lopey cams.

            I used to keep center line and cam vaules in my head like a riddle... injection came along, and wondered why a 1996 vortec 305 was in 3rd place of all gm block history.

            I only narrowed it down to when can it open for the pressured shot of injection.
            the duration gain is at the beginning becuse the pressure forces the air to go with the gas.
            don't need to suck at it.

            that is the gain.
            you don't need lopy, choppy,playing with vacuum.

            find someone who does not go weird with numbers.
            Previously boxer3main
            the death rate and fairy tales cannot kill the nature left behind.

            Comment


            • #7

              Re: Cam differences with EFI

              OK, to back up a little bit:
              Does the car start good?
              Does it idle OK?
              Does it run clean at tip-in / small throttle openings?

              On mine the recommendation was to take the cam that was speced for the motor (regardless of fuel delivery system) and widen the LSA. I tend to run COMP stuff and for the BBF they tend to recommend 110 LSAs. There was a notion that I should open it up to 114 or 116! Upon the advise of a guy that helps me with cam selection I chose to go with 112. It is my understanding that widening the LSA kills torque but given my combination, I am not sure 114 would have been that noticeable.

              So at idle I don't have a lot of vacuum and therefore it tries to search a bit (changing timing and AFR constantly). I found an article on one of Holley's user group sites that had some recommendations on how to "hard code" the target AFR at idle. That seemed to help a little. Also spend a great deal of time and gas driving around with the laptop watching AFR in normal driving conditions. In an attempt to get gas mileage we kept leaning it out until lean surge and then bumped it back up a touch.

              WITH ALL THIS SAID - i probably only got 1 - 2 MPG improvement over my carb set up!

              Sorry, I realize this isn't any help to you other than maybe making you feel like you aren't alone with the fuel injection upgrade joy.

              Hope you figure it out.

              Comment


              • #8

                Re: Cam differences with EFI

                injection should need no lope to go by the old lopey cams.

                I used to keep center line and cam vaules in my head like a riddle... injection came along, and wondered why a 1996 vortec 305 was in 3rd place of all gm block history.

                I only narrowed it down to when can it open for the pressured shot of injection.
                the duration gain is at the beginning becuse the pressure forces the air to go with the gas.
                don't need to suck at it.

                that is the gain.
                you don't need lopy, choppy,playing with vacuum.

                find someone who does not go weird with numbers.
                The lopey cam is simply the tune you hear when you are driving since we dont have a great radio in the car. That is kind of where I am at, is do you need to give that all up when you do this injection? Do you need to build these cars like a 96 motor that made 180 horsepower to keep a TBI happy? I mean, we clearly had a lean pop with the first carburetor before we started messing with the secondary springs, but terrible mileage has to tell you its just too much gas. When I got that Howards recommendation, it pretty much put the cam in the same ballpark, other than highest lift we would ever have had in this car, tiny bit less duration, so how much would it actually change.

                Comment


                • #9

                  Re: Cam differences with EFI

                  OK, to back up a little bit:
                  Does the car start good?
                  Does it idle OK?
                  Does it run clean at tip-in / small throttle openings?

                  On mine the recommendation was to take the cam that was speced for the motor (regardless of fuel delivery system) and widen the LSA. I tend to run COMP stuff and for the BBF they tend to recommend 110 LSAs. There was a notion that I should open it up to 114 or 116! Upon the advise of a guy that helps me with cam selection I chose to go with 112. It is my understanding that widening the LSA kills torque but given my combination, I am not sure 114 would have been that noticeable.

                  So at idle I don't have a lot of vacuum and therefore it tries to search a bit (changing timing and AFR constantly). I found an article on one of Holley's user group sites that had some recommendations on how to "hard code" the target AFR at idle. That seemed to help a little. Also spend a great deal of time and gas driving around with the laptop watching AFR in normal driving conditions. In an attempt to get gas mileage we kept leaning it out until lean surge and then bumped it back up a touch.

                  WITH ALL THIS SAID - i probably only got 1 - 2 MPG improvement over my carb set up!

                  Sorry, I realize this isn't any help to you other than maybe making you feel like you aren't alone with the fuel injection upgrade joy.

                  Hope you figure it out.
                  Starts fine. Idles ok, usually, first start up over this winter it would not idle at all. When I get to the tip in, that is where I think there is a lag and it just stays progressively "sluggish". I guess the term that comes into my mind is this should have the ability to light up the tires at any point, where it takes a brake torque to do that. Does that make sense? That is what the old school thinking in my head tells me when a tune is right. Yeah, that takes me to the point of what is holding it back again, but the 4200 stall seemed to fix all the troubles the Edelbrock was having, but like I said, you cant read anything in the edelbrock setup to find out where fuel tables were.

                  The edelbrock started at 112, but after rounding off the lobes on that one, we did not want to go back to that stick, so the comp was close, the big difference was the 107 centerline instead of the 112. Is this something moving the cam would adjust to get the cam centerline to move by advancing it?

                  Comment


                  • #10

                    Re: Cam differences with EFI

                    WOW - 4200 stall on the street - something tells me this is more than just a hot street car motor!

                    Anyway, if your issue is the stab - I mean you are putting along someone gets frisky and you punch it - it bogs/hesitates/runs sluggish - then maybe you need to play with some of the optional enrichment tables. On the Holley HP system there are 6 tables to adjust richness that are not a part of the "auto learn" feature. The auto learn only deals with the base fuel table which is predominately aimed at "normal" driving behavior.

                    Comment

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