EA81 SPFI MAF details

[tweety]

My EA81 engine is 1992. In Oz the EA81 came out in our Brumby (Brat) from about 1980 to 1994 in carbie version only.  From 1988 onwards eA81's had the larger valves but only 1mm larger.  The larger valve model here had black valve covers as opposed to the early versions that had the blue covers.  The EA82 came out around 1988 in other models till 1995 I think and only in carbie form. No solid lifters here.

[ivans imports]

wow here soilid lifters stoped in 84 then all large valves after that mine is very first year ea81 is ealy 81 i think the soilid lfter cam likes the tbi better than the hydro one

[jono]

Yeah, the only hydro liftered EA81's we got here were imported as used engines from Japan. After one lifter died on me for a moment, I tried to order new hydro from Subaru dealer, told no listing, did not come out in Oz so no listing, not available. Sorry

[tweety]

My MAF is shipped from rockauto together with a new coolant temperature sender. also purchased another one- a used one.

Edited September 12, 2013 by tweety

[tweety]

My friend Greg attended today armed with two multi meters and some sound knowledge. We hooked up one meter to the injector and the second to the MAF and went for several rides.

 

We found that the MAF will only read 3.4 volts maximum. This is when the engine is revving out towards maximum revs in first and second on the auto trans which it will do happily. Should the MAF run to 5 volts when revved?

 

In top gear of the VW auto the trike will only go to 65mph max. There is a huge dead spot with the throttle.

 

The coolant temp sensor measures ok at 600ohms hot.  The injector, recently cleaned, appears to run very well.

 

At this point Greg's opinion is that all is running as it should with the SPFI system except the low voltage on the MAF.

 

Because this system was not available in Oz there are question marks on a few other things though-

 

1/  The camshaft is believed to be original.  This engine has done around 250,000 mls but was reconditioned about 50,000 mls ago with hone, new rings etc.  If the cam wasnt touched there could and most likely is a lot of wear on the lobes that could contribute to the poor power output. Lower lobes due to wear would reduce the valve opening thereby having a negative effect on the performance.

 

2/  We have different fuel specs here.  I run 95RON unleaded.  91 makes the engine perform worse and a 98 is available but it makes the engine run more course.  Greg mentioned that if I was to get another engine rebuilt that fuel differences between here and US fuels might mean that it could be wrong to seek the 9.5:1 compression ratio the original SPFI engine had. Some opinions on this please.

 

3/ We have eliminated fuel feed as an issue. The pump has 3 bar - 42psi.

 

4/ Disconnecting the MAF made no difference to the performance except it did indicate it was running a bit richer.

 

I will start another thread asking for voltage readings on SPFI engines. Cant seem to find them anywhere.

 

Regards Tony

[tweety]

ok, here is Greg's post today on Ausubaru forom. hope this can shed some light to your guys and we can get some opinions

 

 

***************

It was a nice ride, thank you Tony for putting on the
great weather.

 

Tweety is lacking grunt, sort of like when you go up a hill
in top gear, you reach a point where no matter how much further you press the
accelerator, it makes no difference.

Why??

Some readings.

At idle the MAF is at about 0.7v, duty cycle 6%.

When accelerating hard through 1st/2nd, till the auto
upshifts @4500rpm (guessed), the MAF slowly climbs to 3.4v and the duty cycle
slowly climbs to 46%. The rate of increase is in sync with the RPM increase.

 

In top gear, past the kickdown point, at full throttle
the MAF is 2.7v and the duty cycle is 36%, thats where they stay, on a constant
incline. As the accelerator is released, the MAF and duty stay very close to
2.7/36, until the butterfly starts to reduce the required air and Tweety slows,
the MAF/duty drop in sync with the rpm. The motor has no signs of pinging, when
like this.

 

Disconnecting the MAF, increases the duty cycle by about
2%, through the whole rev range, Tweety still runs fine without it, just a bit
richer. This had no effect on full throttle performance in top gear.

 

The temp sensor measured approx where it should be.

 

From the limited information available, it seems the MAF
voltage is lower than what it should be.

 

Is it the MAF, or is it the motor is worn and cannot get
the higher air flow ??

 

Tony equiped with a duty cycle meter and a new MAF will
answer some more questions, soon.

 

[tweety]

Can we have anyone with some guru powers of knowledge to answer the above questions?  please?

[ivans imports]

Is it a hydro cam or a soilid cam engine ? soilid cam 80-83 hydro cam 84-89 ea81s you could take the valve covers off and check the lift height of valves with dial indacator make shure the lift is all the same on all valves. The mass air flow try making the inlet of senser a bitt smaller were it sizes down a plastic ring or cone it could be that the ea81 cant move enuff air to make it get into range a smaller inlet to mass will speed up the air putting ecu back into range

[tweety]

very interesting. thanks. will bare that in mind.