Could this work?, 2056 engine combo ?'s |
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Could this work?, 2056 engine combo ?'s |
ottox914 |
Nov 23 2016, 02:07 PM
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#1
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The glory that once was. Group: Members Posts: 1,302 Joined: 15-December 03 From: Mahtomedi, MN Member No.: 1,438 Region Association: Upper MidWest |
So here's my long sad story. The turbo motor dies several yrs ago, due to a missed shift at lots of boost and rpm's. I bought a recently re-built motor from a forum member to replace it, thinking this was faster and easier than re-building the turbo motor. Lost a year to a new job, selling an house, buying a house, moving to a new state, bring my retired dad along and getting him re-set in a new environment. Put the re-built motor in this past summer. It kept blowing up. Pulled it and fixed it all summer. Kept the seller updated as to my problems with the "good" motor. Called the seller this fall, who graciously agreed to refund full purchase price.
So now I again have a motorless 914. Trying to figure out an N/A build that uses most of the parts in my shed to keep $$$ down. I have the pieces in my stash to build the following: 2 good cases to choose from, 2.0 crank and rods, some good iron cylinders to overbore to 96, (would need to buy some KB's to fill them) some heads that Len did that are 40 x 36, (about 75% I/E ratio) that he says will flow about 175 cfm at 50% lift. They have a 50.4cc chamber. So these, with some flat top KB's would yield about 10.5:1 with .040 deck. 2x valve springs, Len is comfortable with this head to 7k rpm if I would need to go there. I have the ITB's and SDS efi to run it all, and as the injectors were sized to support the turbo motor, I expect I have enough headroom to run some E85 "corn" fuel to handle the CR. Should also hold detonation at bay, and engine should run cooler on corn. Not a bad thing for aircooled motors. Kerry hunter exhaust to finish things off. The wild card is the cam. The cam I had in the turbo motor is still good, not damaged by the over rev. Its ground on a 110 center, has a lift of .500, and is a split duration of 276I/284E, with duration at .050 of 240/249. When researching cams for the turbo motor, seems lots of folks say a factory cam N/A is a pretty good starting point for a turbo cam. When I go to the Web Cam page for the 914, what I got is bigger than an 86, the "street" cam, but not as wild as 86a or 494. What think the collective? Will the flow of the head, small-ish intake valve, and big lift of the cam play well as a team? I expect to get alot of "its all in the combo" remarks, but with as much as is known about what I have to build with, and the cam being the big ?, looking for opinions from those more cam-educated than myself on options to use what I got or not. |
Mark Henry |
Nov 26 2016, 12:58 AM
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#2
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that's what I do! Group: Members Posts: 20,065 Joined: 27-December 02 From: Port Hope, Ontario Member No.: 26 Region Association: Canada |
It's a 2mm smaller intake valve, I wouldn't worry about it. T4 heads have lots of flow on the intake.
Your CR is too high, aim for no more than 9.5:1 unless you plan to twin plug it. I'd get the best cam for the combo, performance carb cams have longer duration. It's the long duration (thus overlap) that messes with the MAP sensor. But if you want the longer duration cam it can be done by running TPS only. With the turbo cam you have you might have a good MAP signal, but for NA you have to change it to a 1 bar MAP. Your turbo sensor is a 2 bar MAP, so you would have to buy a new one bar sensor. If you want to run TPS only (or a 1 bar MAP) PM me and I'll tell you how to short circuit the ECU to get into the code and change it to a TPS only (or 1 bar MAP) system. (IMG:style_emoticons/default/bye1.gif) |
ottox914 |
Nov 26 2016, 07:41 AM
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#3
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The glory that once was. Group: Members Posts: 1,302 Joined: 15-December 03 From: Mahtomedi, MN Member No.: 1,438 Region Association: Upper MidWest |
It's a 2mm smaller intake valve, I wouldn't worry about it. T4 heads have lots of flow on the intake. Your CR is too high, aim for no more than 9.5:1 unless you plan to twin plug it. I'd get the best cam for the combo, performance carb cams have longer duration. It's the long duration (thus overlap) that messes with the MAP sensor. But if you want the longer duration cam it can be done by running TPS only. With the turbo cam you have you might have a good MAP signal, but for NA you have to change it to a 1 bar MAP. Your turbo sensor is a 2 bar MAP, so you would have to buy a new one bar sensor. If you want to run TPS only (or a 1 bar MAP) PM me and I'll tell you how to short circuit the ECU to get into the code and change it to a TPS only (or 1 bar MAP) system. (IMG:style_emoticons/default/bye1.gif) Hey Mark, thanks for the insights. I realize the CR is more than the usually accepted 9.5:1 for pump gas, but I was planning to run E85 "corn" fuel to balance out the CR. Some guys I auto x with swear by the stuff for their turbo motors. Check out this calculator for CR and boost. https://www.rbracing-rsr.com/compression.htm i was running 12psi +/- and around 9:1 static CR. That would have given me an effective CR of 15+, which I was managing on 93 pump and a good tune. I did have to pull timing under boost which I'm sure slowed me down. If that motor hadn't been blown up, and I had the chance to run corn, the results could have been staggering. SDS ftw. I've got a 1 bar map sensor in the car already, and have changed the SDS tables to match it. I keep forgetting the pins to mess with, but this time made some notes so I don't forget. Again. I had just upgraded the ECU to include gauge mode 4, and was looking forward to tuning with it when the last engine failed, and I returned it to the seller. So I'm a little excited to get this new motor up and running and tuned. So far as cams- if I'm looking for more TQ and maybe a 6k redline, spinning it to 6500 at an autocross if I need to extend to the next corner, does that change your opinion of re-using the turbo cam? If this results in a more stable MAP, then the TPS tune will be a plan "B" if needed. Looking to build a 2056 that is a fun, reliable, torque machine that isn't afraid to rpm a little now and then, and just enjoy the car rather than getting all crazy like I did with the turbo project. (which is not to say I won't be seduced by boost again sometime in the future...) |
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