EA81 supercharger revamp by Tweety

Subydoug · Post by **Subydoug** » Wed May 22, 2013 11:14 pm

Pretty sure the main difference with the 4 plug system is it uses ignition mapping. No weights in the dizzy, just a timing wheel. As far as the fuel management goes, better MAF and maybe a few others......variable pot TPS instead of the 3 position TPS....few extra goodies plugged into the manifold.....que Steptoe?

Regards

Doug

YouTube · Post by **El_Freddo** » Thu May 23, 2013 12:16 am

I got onto this thread some how the other night - ausmini SC build page 5. Why page five? Sprintex supercharger - sounds good and it looks a lot smaller than the SC12 or 14 - would probably look neater in the long run - thought you'd like to know about it even if you don't want it.

Another two thoughts (yes it hurt!):

1) Will you be intercooling with the SC and EFI - as this would be a worth while option in my book

2) and if the dip stick is such an issue on the SC12 can't you plug it or swap that plate for one from an SC14 that doesn't have a dip stick?

That's about it from me for now...

Cheers

Bennie

Tweety · Post by **Tweety** » Thu May 23, 2013 10:42 am

I have been thinking also Bennie. I think the SC12 will be more than adequate. Also a visit to the garage and some pondering for 30 minutes made me realise that the mounting set up on the sC12 is ok, no need to mount the SC sideways. Sideways mount will pose other issues and achieve little. The blow through setup will eliminate the carbie so more room- wont look so cluttered.

The sprintex charger is very compact, used in mini's and also Harley's. Australian built (WA). Around $1700 bare. Cant beat the cheapness of the SC12's though and it does the job, likely will last much longer with only air passing through it and last long time also with currently only 5500 rpm. If I install a slightly smaller pulley to achieve 8psi I'd be more than happy. But the EFI may well raise the power output to a satisfactory level compared to the carbie and 5psi, especially off boost for cruise. Why be radical and change things that are working? I ask myself.

First step taken- buying and engine stand. The beauty of this project is it will all be done off the trike and set up over time without rushing. Painted up- yellow block, dont know about the heads.

But all this electronic stuff if foreign. In time it will make sense.

Tweety · Post by **Tweety** » Sat May 25, 2013 2:35 pm

Thanks to Dean I am now the proud owner of a spare ea81 albeit in need of a full reco. And the full SPFI system with dizzy and ECU, manifold etc.

Now that I see the system all sitting in front of me I can see the SC wont install where it is currently mounted, it would need to be thought out more. So the best recipe here is IMO to reco the engine fully (oversize pistons/big valves and anything others recommend considering it will be supercharged to a max of 7-8 psi) then install the SPFI, install it in Tweety and run it in. then add the SC later and recalibrate the dizzy like I did with my last dizzy.

Wont be starting the reco till the end of the year.

YouTube · Post by **El_Freddo** » Sun May 26, 2013 9:58 am

Nice one mate, I'm a little jealous about the SPFI kit! Easiest way to convert an EA81 to EFI!

Also good to see the plan coming together! I can't wait for the end of the year for you...

Cheers

steptoe · Post by **steptoe** » Sun May 26, 2013 11:33 am

I have forgot what was wrong with Tweety in the last place - just his thirst? And you are going to all this extra expense/effort/dare-I say-grief to achieve better economy ?

Tweety · Post by **Tweety** » Mon Jun 03, 2013 6:04 pm

Jonno, at 57yo things change. I like to think ahead. The current engine is running ok but has, since boosting had some blow by issues fixed with a catch can. It consumes a little oil. It never achieves better than 14 l/100kms even with a light foot. We will one day ride him around Australia when retired pulling our van. In retirement you want as economical set up as possible. Current donk is ok but I want a 100% perfect engine. When it is finished I wont ever renew an engine- it will see me out.

So the plan is set.

I am close to getting my alloy trike frame welded up. that will keep tweety on the road. At the same time a fuel return tube will be installed in the alloy tank.

Then tweety, (when Bennie is free) will find his way to Bennie's garage where he can sit on him if he cant sleep. lol. We will isntall the SPFI and get the engine running well.

In the meantime the spare engine will be worked on. The block will be recoed fully as will the heads and that 16/56 cam.

Then the new engine will be installed in Tweety with the SPFI system.

Finally the SC12 will be installed in a blow through system with clutch.

90% of tweety's use is cruising. Hoping to get nice economy with the SPFI set up with the option of more power when I want it.

Today I get the urge to start on the project. The spare engien kindly donated by Dean had its heads removed. Head for cylinders 1 and 3 had almost loose head bolts- all of them. Then I discovered that number 2 combustion chamber has had water in it with rusty valves and a water hark to the half way up the piston face. Water was also in the oil. I took off the oil pump and found that a rubber (as hard as plastic) 'O' ring (pictured) was damaged. I reckon it might have been like this since new. Wonder if oil flow suffered?

I'm as excited as I was when Tweety first started up with the Supercharger and it lifted the front wheel haha.

purp · Post by **purp** » Mon Jun 03, 2013 8:02 pm

He he, I knew when you said you wouldn't start til the end of the year that there would be an update much sooner.

Tweety · Post by **Tweety** » Mon Jun 03, 2013 8:31 pm

Yeh purp. got the ea81 bug. Got it fully after the SC was installed. The power difference still excites me. 30% extra is a lot for 5psi and a lot for a 550 kgms machine. And its simplicity is amazing

steptoe · Post by **steptoe** » Tue Jun 04, 2013 8:38 am

end of the [financial] year

Tweety · Post by **Tweety** » Tue Jun 04, 2013 5:51 pm

The cleaning has begun. The oil pump came up well. Those rocker covers need some chrome. Does anyone know if the bolt washers (odd shape like a cone) are available new?

Subydoug · Post by **Subydoug** » Tue Jun 04, 2013 7:39 pm

Yep, you can get them in a complete ea81 gasket kit, which I highly recommend you spend some money on

.

Regards

Doug

Tweety · Post by **Tweety** » Wed Jun 05, 2013 11:46 am

oh, they are in the kit. great. Tony

Tweety · Post by **Tweety** » Wed Jun 05, 2013 5:57 pm

RE: spare ea81 engine, Today I took off the sump and oil filler degreased and now painted. Engine is now on the engine stand...so much easier.

Re: the 1982 ea81 heads. I assume they are the smaller valve type. The heads on my Tweety engine are black covers assuming larger valves. Question: When I reso the older heads if I can replace the small valves with larger ones would that bring them up to the later specs? eg is there any other difference to the later heads? If the intake tube is larger on the head (or in other ways superior) then I might be better off, at the last minute before install, to take off the heads on Tweety, get THEM recoed and onto the new bored out engine????

I've read a lot on renewing the ea81. As I'm going to SPFI and the SPFI USA engine had 9:1 CR but standard is 8.7:1 I am considering oversize ea71 pistons rather than the head shave. What do you guys think. It seems so much easier.

Lots of questions...so little brain cells.

steptoe · Post by **steptoe** » Wed Jun 05, 2013 7:28 pm

Tony - gonna have to label you Action Man, you don't muck about. Can you show us pics of the heads of both Tweety and the new ones you have, zero in on intake bulb plug sid and any webbing in casting, graph lines look in casting? Think the valve difference is about 1mm

Subydoug · Post by **Subydoug** » Wed Jun 05, 2013 7:58 pm

Valve difference is tiny. My current wagon heads (1982) are small valves and the newer engine I got from RSR555 has the larger ones. Off the top of my head its somewhere from 1-2mm larger diameter. Yes, you could oversize the valves inside your older heads, you would need to get two new valve seats turned up, then put in and ground for you. Pretty big operation for very little gain to be had (my opinion, ea81 heads don't breath very well at all, so any help it can get is good help), especially if your going to push some boost down its throat.

Hmmm, your asking questions that are going to deliver very personalized opinions Tweety....one guy might think this....one guy might think that.

My opinion on the compression ratio would be to have it around standard carby 8.7-1 range.

Has that SPFI unit got two fuel injectors in its throttle body, or just one? it conserned that when you start running boost, it may run out of juice. At 8 psi boost your probably going to be needing around 60% more fuel.....Donno, something someone with spfi experience is going to have to answer.

Regards

Doug

Tweety · Post by **Tweety** » Wed Jun 05, 2013 8:27 pm

Jonno the first pic is of the "greasy" older head with writing continuing across the bridge to the right hand side.

The one below is of the "clean" head on tweety with no writing on the bridge.

Doug. Thanks. I also believe that 1-2mm wont make much difference with valve diameter. I was wondering if the throat intake in the ehad prior to the valve is larger or smaller....I assume its the same eg the valve diameter is the sole difference in both heads. Maybe the only other difference is that the larger valve heads have hardened seats????? If thats the case I'll reco the older heads for convenience.

I dont know if the SPFI system has one or two injectors. I assume one. Havent touched it since purchase. I read somewhere that the system would struggle with boost. I have read the specs on the standard SPFI ea81 and they say 90hp. If thats the case it will be only 10hp less than Tweety's current draw through SC'd set up which dynoed showed 100hp at the fly and 82 at the wheels (is an auto) compared to 59hp and 74hp NA. I wouldnt have a problem keeping a future SC12 at 5psi if the SPFI could handle the extra fuel for that boost level. If it cant I'll need to figure out how I could deliver more fuel. it just might not be worth the installation of the SC12 at the end of the day but remains an option.

Tweety · Post by **Tweety** » Wed Jun 05, 2013 10:07 pm

Re boost onto SPFI

http://www.ultimatesubaru.org/forum/top ... any-boost/

Also re: compression options

Taken from a post by GeneralDisorder on the USMB..

EA81 carb pistons are 8.7:1
EA82 carb pistons are 9.0:1
EA82 SPFI/MPFI pistons are 9.5:1

And yes they all swap between engines, even the EA-71.

Some FYI, EA-82 Turbo piston give a 7.7:1 ratio.

steptoe · Post by **steptoe** » Thu Jun 06, 2013 7:43 am

Hmm. OK , thought I could tell the difference between old and new heads with the valve difference ....comment from a head specialist of many years, to me, was that the EA81 had big enough valves as it was.

Tony, u are chasing torque not max horsepower surely ?

Subydoug · Post by **Subydoug** » Thu Jun 06, 2013 9:11 am

Yeah I looked into what the different pistons did to the CR when I was rebuilding my new motor. Decided shaving the head was the best idea, just so I can run standard pistons. Your call mate on the piston choice.

Regards

Doug