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EFI, Boost & Timing |
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farna
Supporter of TheAMCForum Moderator Lost Dealership Project Joined: Jul/08/2007 Location: South Carolina Status: Offline Points: 19689 |
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shootist, you are correct -- crank trigger ignition. When I said an electronic distributor with rotor only has a limited timing range I meant the electronic only part, not considering any mechanical or vacuum adjustment, just by changing when the fire actually occurs on the rotor. For an easy way out see http://195.6ohv.com/IGNITION/index.html. Scroll down to "a better ignition solution" and read from there. He's doing this on a "lowly" 195.6 OHV six, but the same system works for a V-8. Unlimited timing adjustment, and always spot on! The only other thing you need to consider when choosing an EFI system for boost is that you have a boost referenced MAP sensor. A standard MAP won't work, has to "know" you're pressurizing the manifold. The MAP is available with a max pressure rating in several sizes (pressure ratings). Edited by farna - Nov/09/2018 at 6:46am |
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Frank Swygert
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shootist
AMC Addicted Joined: May/24/2012 Location: Triad, NC Status: Offline Points: 1023 |
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Rebel, I have yet to get the car on the dyno at this point but I am guesstimating on the power output being in the 800HP range simply because my build was a redo of the procharged 401 done by Bob Woods for the HotRod article with some minor upgrades I obtained from talking to Bob and his brother. Basically we made tweaks to their build spec that they would have wanted to make for a second revision. Basically this is lighter rods and pistons and a roller cam rather than solid. I am guessing that should be good for at least 10-20HP but who knows. I am pretty certain it is at minimum making the same power or capable of it with a good tune. If my seat-o-pantsometer is accurate I would say it is a touch over 800 at the crank but I will let you know once I get some real numbers next spring.
That article is here. https://www.hotrod.com/articles/ccrp-1301-780-american-horsepower/ You can get my specs from my old thread below. http://theamcforum.com/forum/supercharged-401-build-w-pics_topic81131.html |
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shootist
AMC Addicted Joined: May/24/2012 Location: Triad, NC Status: Offline Points: 1023 |
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Thanks for clarification Farna. I thought that was what you were saying but I wanted to be sure I was understanding what you meant. In my configuration and by your verbiage the MSD pro billet should be considered a distributor-less type system as the firing is controlled by an independent crank trigger in the base of the unit. The only difference in the MSD distributor versus the standard crank trigger is that the initial timing would be set and of course the limitation of rotor to cap alignment (but that still allows a pretty wide range of selection I suppose the pro billet could drift a bit as the gears wear so that is always a potential downside. I really like that megajolt setup and it would be really hard to beat the dead on accuracy you would get from a keyed crank trigger setup like that. The extra flexibility in adjusting the spark map is nice too.
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Rebel Machine
AMC Addicted Joined: Jul/03/2007 Location: Western Il Status: Offline Points: 5121 |
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That's your engine? Sweet! I spotted that article when looking at taking on this project. Thanks for the specs, that'll help shed some light on where we need to go. Another forum member said since it's a boosted engine a flat tappet cam would work just fine. It would be a less expensive route but I prefer a roller. -Steve- |
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Rebel Machine
AMC Addicted Joined: Jul/03/2007 Location: Western Il Status: Offline Points: 5121 |
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Shootist, I noticed the cam specs are different in the Hot Rod article than your forum posted specs. Could you clarify which you actually have? Thanks, -Steve- |
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redrebel
AMC Apprentice Joined: Jan/19/2012 Location: Kenosha wi Status: Offline Points: 208 |
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Currently running 1200 power adder with torqstorm 10.6: comp iron heads on 93 using timing control in fitech but im all in 34 on boost no issues,
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shootist
AMC Addicted Joined: May/24/2012 Location: Triad, NC Status: Offline Points: 1023 |
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Sure Rebel Machine. My cam spec is in my build thread on this forum if you want the details. The only difference between them really is that the cam I am using is a roller cam. Below are the specs from my build thread to clarify my setup. If you compare my cam specs to the HotRod spec you will notice an identical duration @ .050" lift on the HotRod build and mine. However, my max lift is larger and because it is a roller cam it means my valves open and close way faster while also remaining wide open for more of the duration. This results in flowing much more in and out with the same duration to the flat. We also should take into consideration that I also have less rotating resistance due to the rollers. Anyway, what I was trying to say in my last post was that when I asked the builder what he would have done differently he told me roller cam with a little more aggressive lift. So, that is what I did with my build.
Comp Cams Hydraulic Roller Cam (custom grind) 114* LSA duration is 230/236 @ .050" intake/exhaust Adv. duration is 282/288 lift is .544" intake .555" exhaust Comp Hydraulic Roller Lifters redrebel, Wow! That is a high compression ratio for boost. What is your boost pressure?
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Rebel Machine
AMC Addicted Joined: Jul/03/2007 Location: Western Il Status: Offline Points: 5121 |
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Thanks for the clarification. I showed your cam specs to my engine builder and he really likes it. We'll probably use a similar, if not identical grind. -Steve-
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shootist
AMC Addicted Joined: May/24/2012 Location: Triad, NC Status: Offline Points: 1023 |
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I think you will love it once your get it done. If you are going with the flat tappet cam I would recommend using the same grind as the HotRod build but just increase the lift if possible. If you go roller cam I think you would be very pleased with my cam spec as it seems to work really good and I still build plenty of vacuum for power brakes and the EFI loves the smaller exhaust overlap and keeps the MAP and IAC from getting weird on you. The downside is you don't get that really radical cam lope but you gain a lot of other things worth that small sacrifice while still maintaining a good high performance sound. There is also nothing quite like ambushing someone unsuspecting when they think they could take you.
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Rebel Machine
AMC Addicted Joined: Jul/03/2007 Location: Western Il Status: Offline Points: 5121 |
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That's the idea! -Steve-
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