How does switching to SPFI affect the torque curve on an EA81?

[zyewdall]

Question -- mostly for GD, I guess, but whoever else has experience with this. But, I am considering putting SPFI on my '82 wagon. Engine still runs great, but I'd like the reliability of my '89 wagon as far as cold starting, smooth running etc. Right now it's got the feedback hitachi, which to be honest runs pretty good, but still...

 

Anyway, my question is -- the carbed EA81 feels like it has more low end torque than my EA82 SPFI. The SPFI definetly has more power on the highway -- no question there -- but you can lug the EA81 to 2,000rpm going up a hill and it still has power. The SPFI EA82 just doesn't do well below 2,500rpm or so and just doesn't feel as powerful crawling on dirt roads. Since the '82 is going to be my lifted rig, torque at 2k and below is important. I remember my old '82 wagon had the torquey feel when offroading too.

 

Maybe I'm just thinking this because the EA81 is a lighter car than the EA82? Or do the distributors have different advance curves?

 

Thanks

 

Z

[Phizinza]

Can't answer your question but.

I know exactly what you mean about the EA81 pulling better. But I'm thinking it's more to do with the car. I hear the EA82 car bodies weight a fair bit more. And the EA81 style normally comes in at 1050kg.

I cant see how the SPFI would be timed to run better at higher and not also better at lower though. Doesn't makes sence when they have the ability to program it unlike a carb.

 

There you go, another post by me that sounds like it's helpful and useful but really it just said what you were already thinking....

[daeron]

well, the advance curve of the distributor would be different.... but the EA82 distributor doesnt HAVE an advance curve, it is all done electronically.

 

The distributor for the EA82 is nothing more than a physical spark distributor, the method of setting the base spark timing, and a housing for the Crank Angle Sensor. There IS no advance mechanism underneath that dust plate; just a disc with either 180 or 360 small holes in it, and four large holes; an LED; and a photoelectric sensor. The disc spins with the rotor, and the light signals tell the ECU where the engine is in its rotation.

 

Now, all that being said, I have NO idea what kind of difference may exist between the advance curve on the EA81 dizzys, and the programmed advance used on the EA82 ECU. so, no real help from me, either... sorry :-p

 

I think GD would be considered by most to be the resident expert here, maybe try private messaging him?

[GeneralDisorder]

The advance doesn't have nearly as much to do with it as the cam. The EA82 SPFI is a higher reving engine, and produces fully 16 more peak HP than an EA81. As such it's cam grind isn't as "torquey" as the EA81. It does rev easier and faster than a carbed engine though, so it really doesn't make than much difference. The EA82 SPFI that's in my Brat right now is quite a significant improvement over the EA81 it had. It will make perfectly fine torque if you give it the revs it needs.

 

SPFI on a stock EA81 has comparable torque to the Weber. It doesn't have the "spot" where the secondary opens so it behaves differently. But it's a pretty darn big TB, and you get a LOT of air through it. The sound isn't the same as the Weber, but the power is there just the same. Also much more condusive to snorkel setups as the intake duct is round and requires no adaptors.

 

The SPFI system itself is really flexible actualy. It's sensors give it the ability to adjust for engine flow, and by using MegaSquirt you could actually tune it anyway you wish. Timing and advance curves are all easily modified. Quite a fun challenge actually.

 

GD

[ballitch]

dont you have to strip a wire harness down to do this swap? you should think about this for a second.....if you have to strip a harness down for this swap, wouldnt you want more than 90-100hp at the crank? im thinking in the neighborhood of 110-140 hp at the crank, i.e. an EJ swap. my ej22 is awesome under 2k rpms on the trail. i would suggest you do a comparison on the spfi swap vs. the ej swap. ya the ej swap is harder, and more involved as far as wiring and fitting the ej motor under your hood is concerned. i would just hate to see you spend the time and the money to do the spfi swap when you realize the ej swap isnt that different, harder, but well worth the money and time it takes to do it. but i am biased......

 

 

 

~Josh~

[Phizinza]

I would think SPFI would be a much cheaper option. But the power of an EJ is much better too.

 

Remember, some people like more standard equipment. And theres nothing wrong with that.

[zyewdall]

Well, eventually, it's getting a turbodiesel swap, which is going to have way more low end torque than any EA series engine, and possibly than the EJ22 even.

 

But the question is how much do I fool around with the stock engine before I get around to the big swap. I sort of like fiddling with engines, and I've never put fuel injection on anything before. But if a good EJ22 fell into my lap, I'm not saying I wouldn't stick it in there.

 

Or, I could keep myself amused by putting a megasquirt system on my old mazda pickup truck instead.

 

Too many toys, and not enough time

[daeron]

But the question is how much do I fool around with the stock engine before I get around to the big swap.

 

Answer: SPFI swap, and in the future sell the engine complete with wiring and ECU once you get your "mega-swap" done.

[stickedy]

Could it be possible that the differences in the torque between EA81 and EA82 are a result of a slightly different transmission tuning? Perhaps the EA81 is more tuned for acceleration but the EA82 is for speed.

[mikeshoup]

Perhaps the EA81 is more tuned for acceleration but the EA82 is for speed.

Not the case at all. Quite the opposite perhaps, especially with the 83+ 4spd D/R.

[zyewdall]

Answer: SPFI swap, and in the future sell the engine complete with wiring and ECU once you get your "mega-swap" done.

 

Good point. Selling a used EA81 when I take it out -- maybe $100 if its in great shape. One that's SPFI already -- a bit more...

 

As far as trannies go, it's a '82 wagon, but the engine is an '83, and it's going to be getting a 5 speed dual range from an EA82 soon (the lower range in that should balance out the larger tires I'm putting on there, maybe)

 

I liked the explanation about the cams. Makes sense. I know that valve timing and duration can have a big effect -- the non VTEC honda engines have pitiful torque at 2krpms, but the VTEC ones are decent torque, and they can rev. Not sure what I think of a computer controlling the valves though.....

[daeron]

I liked the explanation about the cams. Makes sense. I know that valve timing and duration can have a big effect -- the non VTEC honda engines have pitiful torque at 2krpms, but the VTEC ones are decent torque, and they can rev. Not sure what I think of a computer controlling the valves though.....

 

Exactly! Now, the question is, has anyone ever had a custom ea-81 cam ground that more closely matched the characteristics of the EA-82? I think that someone could probably teach themselves SO MUCH about cam tuning in general playing with these engines, IF they had the ability to conjure camshafts up at will.... Unfortunately, that takes the kind of money not frequently found in Old Subaru Town...

[zyewdall]

Exactly! Now, the question is, has anyone ever had a custom ea-81 cam ground that more closely matched the characteristics of the EA-82? I think that someone could probably teach themselves SO MUCH about cam tuning in general playing with these engines, IF they had the ability to conjure camshafts up at will.... Unfortunately, that takes the kind of money not frequently found in Old Subaru Town...

 

Yeah... The people who do custom cams do V8's...... which are actually cheaper anyway, because more people do them. Performance parts for odd 4 clyinder engines are expensive. I was going to add a Mallory electronic distributor to my old 4 cylinder mazda truck -- $800 For your average V8 engine, only $300. Guess I'll keep the points and condenser.

[TahoeFerrari]

I think the idea about getting an EA81 cam reground to more closely resemble the performanc of the EA82 cams is on the right track. Even without doing that, I would expect that you'd get more power and torque with the spfi setup, but probably at a higher rpm than the carb'd EA81 - because (unless you've got something like a megasquirt) the ECU thinks you have an EA82 engine in there and is programmed to the performance curves of the EA82 cams.

 

I don't understand what the problem is about needing the torque way down low unless you are already crawling in low range 1st gear. Otherwise gear down and run higher rpm's. If you're already in low range 1st my only questions would be is what size tires you have and exactly what cliff are you trying to scale? My experience is that the low range gearing allows some pretty slow speeds with reasonably high rpms.

 

I've got all the spfi parts (I think) and am going to try and put it in my '82 hatch ("Blue Eye Cyclops") one of these days which I only use off road these days - although I admit I'm not doing any rock crawling with it.