Snowman Posted December 16, 2004 Share Posted December 16, 2004 Yes, I did a search and found a thread that mentioned this but did not provide any real answers. So, here's my quandry: I just converted to SPFI in my wagon, and since it was so successful, I've been talking with Jerry (bratsrus1) about an SPFI conversion on his ea81-powered hatchbrat. The question that remains in my mind is on compression. The engine that I did my conversion on was an ea82 that already had the SPFI shortblock with 9.5:1 compression. The ea81 has 8.7:1 or 9:1 or something like that which I really can't remember. Regardless of the number, it's lower than this fuel system was designed for. Now, I would think that it would still run fine, but that the performance might be reduced. I was also thinking that this could be mitigated slightly by running more timing advance, which would be allowable with the lower compression (less potential for detonation). All of this is purely hypothetical at this point though. Is the lower compression going to create any problems? Link to comment Share on other sites More sharing options...
archemitis Posted December 16, 2004 Share Posted December 16, 2004 its efi, the maf will see how much air is goin in, and it will adjust the mixture. miles fox has ran the spfi, on a carbureted block, with the lower compression. i think his words were dog turd on wheels... a bit slower with the lower compression. but its gotta be better than a carb no matter how you cut it =]. Link to comment Share on other sites More sharing options...
Snowman Posted December 17, 2004 Author Share Posted December 17, 2004 That's the response that I was looking for. The only thing that I still wonder about is the ignition timing advance map, but I suppose it wouldn't be affected that much, and more timing advance could be run to help compensate. Link to comment Share on other sites More sharing options...
bratsrus1 Posted December 17, 2004 Share Posted December 17, 2004 Hey Snowman This is Jerry, i am installing this set up on a stock EA81 now. But what you don't know is that i am building a new EA81 with EA71 pistons and cutting the heads down and having the cam rework. This new engine will have the compression that this injection needs. The stock engine is to get all the bugs work out of it. Thanks Jerry Link to comment Share on other sites More sharing options...
Snowman Posted December 17, 2004 Author Share Posted December 17, 2004 That's gonna be freakin' awesome!! Link to comment Share on other sites More sharing options...
Caboobaroo Posted December 17, 2004 Share Posted December 17, 2004 yeah Kelly and if you need some EA71 pistons, then I got a set back home I can pull next time I'm there... Link to comment Share on other sites More sharing options...
archemitis Posted December 17, 2004 Share Posted December 17, 2004 i swear my old 2x wagon with the spfi engine(it was a newly rebuilt junkyard score) was as fast as an xt6, i dont know why, but if you floored it in second gear, after being hooked up, it would spin the tires. compression = power Link to comment Share on other sites More sharing options...
spanky_pete Posted December 17, 2004 Share Posted December 17, 2004 Sounds like an interesting project, but when putting the spfi setup on an ea81 would you have to us an ea82 ecu? I would think there would be some quirky issues doing that. Link to comment Share on other sites More sharing options...
MorganM Posted December 17, 2004 Share Posted December 17, 2004 Sounds like an interesting project, but when putting the spfi setup on an ea81 would you have to us an ea82 ecu? I would think there would be some quirky issues doing that. For sure unless you wanna build your own ECU :-p Everything the ECU controls you are swaping onto the EA81.... what quirky issues? Link to comment Share on other sites More sharing options...
spanky_pete Posted December 17, 2004 Share Posted December 17, 2004 For sure unless you wanna build your own ECU :-p Everything the ECU controls you are swaping onto the EA81.... what quirky issues? Since the ecu is designed for an engine that is similar but not built quite the same, I was just thinking you might encounter some issues with tuning it. Can a stock ea81 handle the amount of fuel the spfi would deliver without bottlenecking somewhere? Link to comment Share on other sites More sharing options...
northguy Posted December 17, 2004 Share Posted December 17, 2004 Since the ecu is designed for an engine that is similar but not built quite the same, I was just thinking you might encounter some issues with tuning it. Can a stock ea81 handle the amount of fuel the spfi would deliver without bottlenecking somewhere? Isn't this the exact issue that has been discussed in this thread so far? Link to comment Share on other sites More sharing options...
spanky_pete Posted December 17, 2004 Share Posted December 17, 2004 Isn't this the exact issue that has been discussed in this thread so far? That's what I was getting at, if there was an aftermarket ecu possibility you could change the fuel map and fix some of the problems. Link to comment Share on other sites More sharing options...
MorganM Posted December 17, 2004 Share Posted December 17, 2004 its efi, the maf will see how much air is goin in, and it will adjust the mixture. miles fox has ran the spfi, on a carbureted block, with the lower compression. It adjusts as needed.... to a point. The minor difference here does not breach that point. Link to comment Share on other sites More sharing options...
archemitis Posted December 17, 2004 Share Posted December 17, 2004 That's what I was getting at, if there was an aftermarket ecu possibility you could change the fuel map and fix some of the problems. there wont be problems, its efi! electronic fuel injection. it adjusts itself, sure you can find aftermarket computers, but this will work great. i know a guy runing mitsubishi fuel injection on his 72 vw bug engine. thats a computer meant for 190 hp stock, runing a 75 hp motor. mass air flow sensor, thats all it needs. you cant think of it like carburetion. if you put an ea82 carb on an ea81 it would work, but it would run fat, unless you changed the jetting, but efi does that automaticaly. Link to comment Share on other sites More sharing options...
Snowman Posted December 17, 2004 Author Share Posted December 17, 2004 I too now fully agree that there shouldn't be any quirky issues with running this setup. The lower compression will result in less power, but that's it. As long as the engine isn't too big for the fuel system to handle, it should be able to adjust accordingly to any differences in need via the the oxygen sensor and the learned memory which is designed to compensate for the MAF and the injector getting old. Link to comment Share on other sites More sharing options...
spanky_pete Posted December 17, 2004 Share Posted December 17, 2004 there wont be problems, its efi! electronic fuel injection. it adjusts itself, sure you can find aftermarket computers, but this will work great. i know a guy runing mitsubishi fuel injection on his 72 vw bug engine. thats a computer meant for 190 hp stock, runing a 75 hp motor. mass air flow sensor, thats all it needs. you cant think of it like carburetion. if you put an ea82 carb on an ea81 it would work, but it would run fat, unless you changed the jetting, but efi does that automaticaly. Ok sweet, thanks for setting me straight. Link to comment Share on other sites More sharing options...
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