az240z Posted February 26, 2011 Share Posted February 26, 2011 I am rebuilding a 1978 280z and have a question concerning engine managemnet. the engine was rebuilt and bored .020 over. Some one said that I would have to go with Megasquirt or some other engine managment system as the stock ECU won't recognize the engine. Is this true?? Quote Link to comment Share on other sites More sharing options...
rayaapp2 Posted February 26, 2011 Share Posted February 26, 2011 No. This is not the case. If the electronic control system is in good shape you will be fine. Corroded connectors or bad sensors can cause problems, but an overbore is not an issue. Quote Link to comment Share on other sites More sharing options...
z-ya Posted February 26, 2011 Share Posted February 26, 2011 (edited) I am rebuilding a 1978 280z and have a question concerning engine managemnet. the engine was rebuilt and bored .020 over. Some one said that I would have to go with Megasquirt or some other engine managment system as the stock ECU won't recognize the engine. Is this true?? If the only change from stock you did was bore it 0.020 over, then the stock EFI will work fine. Edited February 26, 2011 by z-ya Quote Link to comment Share on other sites More sharing options...
az240z Posted March 1, 2011 Author Share Posted March 1, 2011 (edited) That's not the only thing, I installed flat top pistons and a maxima head. Edited March 1, 2011 by az240z Quote Link to comment Share on other sites More sharing options...
Administrators RTz Posted March 1, 2011 Administrators Share Posted March 1, 2011 The stock EFI can handle that combination pretty well (if you stick with a stock cam)... but that compression ratio is just asking for trouble on pump gas. Quote Link to comment Share on other sites More sharing options...
Leon Posted March 2, 2011 Share Posted March 2, 2011 (edited) ... but that compression ratio is just asking for trouble on pump gas. Especially with the stock cam. This is a situation where we need as much info as possible to make any judgment. If it's an overbore with everything else stock then the stock ECU handles it just fine. If you have an MN47 with flat-tops and a 290 degree cam then you really want a standalone ECU. Edited March 2, 2011 by Leon Quote Link to comment Share on other sites More sharing options...
az240z Posted March 2, 2011 Author Share Posted March 2, 2011 everything else is stock Quote Link to comment Share on other sites More sharing options...
Leon Posted March 2, 2011 Share Posted March 2, 2011 So everything is stock, except the MN47 head and flat-tops? Good luck running pump gas with that setup, as your compression is definitely over 10:1 and probably getting close to 11:1. Since you are running a stock cam, you will definitely detonate unless you swap out to a longer duration cam that can bleed off cylinder pressure at low speeds. IMO, it's worthless to go with flat-tops and an MN47 without doing anything else. You'll see minimal gains and you'll have to run race gas. So your choice is to either run race gas and hope that the stock ECU handles this combo (which it probably will given that your cam is stock) or swap out cams to get more performance out of it and maybe run pump gas. However, the latter will require custom fuel management. Or, you can always go with the easier and more economic choice, forget the MN47 and put on a P79/P90 head. You'd have a late-ZX engine which will run on pump gas and the stock ECU. Quote Link to comment Share on other sites More sharing options...
z-ya Posted March 3, 2011 Share Posted March 3, 2011 That's not the only thing, I installed flat top pistons and a maxima head. Oh, that's all . Well, that's enough to make the stock EFI have issues. Quote Link to comment Share on other sites More sharing options...
az240z Posted March 3, 2011 Author Share Posted March 3, 2011 next question would be what if I went with SU's. As to the cr I thought i would ba around 9.5 to 10. Guess my calcs were off. Guess I should start looking for another head!! Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted March 4, 2011 Share Posted March 4, 2011 (edited) Isn't the mn47 a high quench head when used with flattops? If so, it's possible the mechanical combination will work but, as someone else said, a cam change is a good idea and it's possible that the factory timing curve will be too intense making a good working egr system mandatory for highway cruising. Edited March 4, 2011 by HowlerMonkey Quote Link to comment Share on other sites More sharing options...
z-ya Posted March 4, 2011 Share Posted March 4, 2011 next question would be what if I went with SU's. As to the cr I thought i would ba around 9.5 to 10. Guess my calcs were off. Guess I should start looking for another head!! I think you will be OK running 93 octane and a conservative ignition advance. Whether you go with a programmable EFI or SUs, it doesn't matter. What matters is that you spend some time on the dyno tuning. Personally, I'd rather tune from my laptop than play with carburetor jets and SM needles. And as others have mentioned, you might as well upgrade the cam to get the most of the increased CR. 1 Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted March 4, 2011 Share Posted March 4, 2011 You could run it on e85 but would need some ecu changes to go with the bigger injectors. Quote Link to comment Share on other sites More sharing options...
az240z Posted March 6, 2011 Author Share Posted March 6, 2011 Guess I'm going to change the head as 93 octane isn't available here in Phoenix. Race gas is too expensive and mega squirt is too complicated for me. The other choice is to find another engine to install. Quote Link to comment Share on other sites More sharing options...
zredbaron Posted March 8, 2011 Share Posted March 8, 2011 (edited) Whether you go with a programmable EFI or SUs, it doesn't matter. What matters is that you spend some time on the dyno tuning. Personally, I'd rather tune from my laptop than play with carburetor jets and SM needles. And as others have mentioned, you might as well upgrade the cam to get the most of the increased CR. Great advice on all counts. Going to a dyno should be automatic after every set of changes you make a change to your engine. Keep in mind that changing a cam won't change as much as you think it should unless you port the head to enable the additional flow to take place (or to maximize it, depending on the head or one's perspective). Also, unless you're hell-bent on nostalgia and either want to learn how to fiddle with carbs or are already a carb master, EFI is the only logical choice, especially since you already are running it. It's hard to do one or two upgrades to an engine and stop there. It won't make the additional power/torque you think it should simply because another aspect of the engine becomes the choke point instead of whatever was upgraded. In my opinion, unless you are *very close* to a manufacturer's OEM engine AND have no desire to upgrade anything further, not getting a fully programmable ECU is a disservice to yourself and also to future upgrades. "Good enough" is only good enough if the topic of discussion isn't important to you. In other words, are you trying to build an engine that is well-tuned and balanced, or are you trying to build a powerful one? Better to buy a programmable ECU once and be able to re-tune it on dyno day after any mod you could possibly think of for the engine. ~$150-300 for the dyno tuning is among the cheapest horsepower one can find. If you're intimidated to tune an ECU, you can simply pay the dyno shop to tune the car for you. If they're competent, it's not an issue. Megasquirt is one of the most popular ECUs (good for consulting those who have gone before you), but Electromotive is often overlooked. I'm personally very loyal to Electromotive. If you go to their site and download the .pdf of their operating manuals, you will probably see why, as they are unassuming of experience level and explain everything initially in layman's terms and then get in the weeds and show you how capable their product is. (Megasquirt's documentation may also do the same, I haven't seen it.) Edited March 9, 2011 by zredbaron Quote Link to comment Share on other sites More sharing options...
Gollum Posted March 10, 2011 Share Posted March 10, 2011 I think this has all been well covered, but as much as I think the MN47 combined with flat tops has some killer potential it sounds like it might not be for you. EFI is certainly wonderful, and programmable EFI is a must for anyone wanting to do some hot-rodding, like you're wanting to do. My advice would be to either bite the bullet and go for megasquirt with a hotter cam, or instead sell the head and get a P79/P90 and take the money you'd spend on megasquirt getting the head worked over a little and maybe get some decent carbs for the sucker. And in both those scenarios dyno tuning should be on the to-do list. In short, only use the factory ECU if you're shooting for factory horsepower, in which case you should go with a factory compression combo. Quote Link to comment Share on other sites More sharing options...
az240z Posted March 11, 2011 Author Share Posted March 11, 2011 You guys keep coming up with more options. Originally I wanted an engine with a little more zip, not looking for 300hp, but a more responsive engine. I will give the megasquirt more thought and will look into the electromotive. The car is currently a rolling chassis and I am slowing putting it together. It has a 3.90 rear end, MSA sway bars, energy suspension springs, KYB shocks and a bunch of other stuff. Quote Link to comment Share on other sites More sharing options...
zredbaron Posted March 11, 2011 Share Posted March 11, 2011 (edited) Isn't that what we're supposed to do on HybridZ? Spend your money for you? For "more pep" and without braking the bank too much, the basics like a K&N air filter, bigger throttle body, perhaps a little more cam (not too much), and 3-2-1 headers with a Magnaflow (personal preference, any straight-through should be fine) muffler should provide some extra zip (and a wonderful sound, which gives the illusion of speed) without braking the bank. A stock ECU, although not ideal by any means, I agree should be able to handle the upgrades (ie balance the AFR ratio for the changes). You can always save the programmable ECU and basic port job (with another step up in cam) for a later date if you decide you want a even more pep. Messing with the head, CR, etc is very expensive, and you don't get a return on your investment unless you align every other aspect of the engine as well. FWIW, what sold me on Electromotive initially is it's spark energy and spark duration has a considerable advantage over CD designs; 2 coils are charging while the other is discharging, not to mention capacitors simply can't compare to inductors in terms of amperage (current), which in my opinion is much more important than voltage. I remain loyal for these reasons and also because they keep adding new features and improve their designs every couple of years. Edited March 11, 2011 by zredbaron Quote Link to comment Share on other sites More sharing options...
Leon Posted March 11, 2011 Share Posted March 11, 2011 You'll get much more bang for the buck out of a numerically higher diff ratio, lighter flywheel and bigger exhaust than trying to cobble bits together that will degrade performance unless more thought and money is put in. Quote Link to comment Share on other sites More sharing options...
az240z Posted March 11, 2011 Author Share Posted March 11, 2011 I do have a jet coated header and a new exhaust, all from MSA. Quote Link to comment Share on other sites More sharing options...
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