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hovercraft with ej18


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25 replies to this topic

#1 ivans imports

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Posted 05 June 2012 - 10:00 AM

Have a customer that has a hovercraft has a ea81 engine we put in a ej18 to up the power but was a bitt heavyer so he was having trubble getting the back end up. So the problem to solve is how do we take 50 lbs of of a ej 1.8 any ideas? have thought of trimming off edges and ears brackets and drilling holes in bell housing lighter crank pully mabee even titaium bolts lighter timing components.He has even whent from wood prop to carbon fiber prop but still have to lighten engine give me some ideas boys

#2 Frank B

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Posted 05 June 2012 - 10:44 AM

Is there still a flywheel on the engine? Have it turned down to reduce weight. Trim the protruding ends of any bolts and studs. Maybe even use a smaller gauge wire for some things. The alternator and starter are heavy, maybe look at replacing those with smaller ones???? But I don't think that's possible.
Do you have any pictures of this machine?

Edited by Frank B, 05 June 2012 - 10:49 AM.


#3 Gloyale

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Posted 05 June 2012 - 10:47 AM

Have a customer that has a hovercraft has a ea81 engine we put in a ej18 to up the power but was a bitt heavyer so he was having trubble getting the back end up. So the problem to solve is how do we take 50 lbs of of a ej 1.8 any ideas? have thought of trimming off edges and ears brackets and drilling holes in bell housing lighter crank pully mabee even titaium bolts lighter timing components.He has even whent from wood prop to carbon fiber prop but still have to lighten engine give me some ideas boys


50 lbs is almost 20% of the engine weight.

Doubt you'll get that much.

#4 1 Lucky Texan

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Posted 05 June 2012 - 11:33 AM

should be able to trim a LOT from a flywheel as I imagine there's a lot of flywheel 'effect' from any attached prop.

but yeh, 50lbs is a lot.

maybe higher octane fuel and more compression? smaller radiator? motorcycle battery?

#5 johnceggleston

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Posted 05 June 2012 - 12:55 PM

or move the drivers seat farther forward to move the center of gravity.

does an ej18 really weigh 50 lbs more than an ea81?

#6 Fairtax4me

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Posted 05 June 2012 - 01:04 PM

How about put a 2.2 on it with a bigger fan and make use of the extra power? A 2.2 should weigh a bit less anyway since there is less material around the cylinders right? (larger bore)

Otherwise lightened crank pulley. Aluminum alternator brackets instead of iron. there could be some weight savings from single bearing idlers. Reground cams will shave a small amount off and offer better power to boot. Dunno if the SOHC motors ever came with composite cam sprockets but I would think they would weigh less than the steel ones.

#7 fishy

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Posted 05 June 2012 - 06:13 PM

Any Monty Python fans here? Perhaps the hovercraft is full of eels :) :drunk:

#8 ccrinc

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Posted 06 June 2012 - 08:59 AM

There's no way in hell you're going to get an EJ18 anywhere close to the weight of an EA81. Hell, just the crank is twice the weight of the EA81! You're really looking at about a 100 lb. difference between them. That's a lot of weight for a difference of about 30hp.

They may be similar in physical size and displacement, but the similarities end there. Either the location of the engine is going to have to change, or something else is in order to balance it out.

#9 ivans imports

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Posted 06 June 2012 - 09:57 AM

this type of problem solving is hard thiss is good to get other peoples ideas. There is a flywheel so we could start there it dosent need to be the same wheight as a ea81 because it makes more power. But it needs to be lighter the engine cant be moved and more hp whould not help as prop is setup for max 120 hp. It uses two engines a small rotax for lift and a ej1.8 for thrust. 50 lbs is alot to remove but i think it could be done. The benifits to having the ej in place of the ea have to be wheighed the ej makes more hp and tourque and has efi witch gives it relability but the ea is lighter but carbed.Thanks for the ideas will keep you guys posted on the end results.

#10 1 Lucky Texan

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Posted 06 June 2012 - 10:04 AM

this type of problem solving is hard thiss is good to get other peoples ideas. There is a flywheel so we could start there it dosent need to be the same wheight as a ea81 because it makes more power. But it needs to be lighter the engine cant be moved and more hp whould not help as prop is setup for max 120 hp. It uses two engines a small rotax for lift and a ej1.8 for thrust. 50 lbs is alot to remove but i think it could be done. The benifits to having the ej in place of the ea have to be wheighed the ej makes more hp and tourque and has efi witch gives it relability but the ea is lighter but carbed.Thanks for the ideas will keep you guys posted on the end results.



you might 'carefully' experiment with altering the thrust angle so it lifts the rear and pitches the nose down a little. And maybe find a way to boost the Rotax's output.

If the engine/pilot can't move, could the fuel and/or any on board battery be moved forward? (battery would be best as it is a static load)

#11 ivans imports

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Posted 06 June 2012 - 10:23 AM

Heres the real problem its not mine so every mod has to be aproved by owner he has spent lots of time and money trying to cut wheight and reposition wheight my job is as the engine builder to get the engine to the exact wheight specifyed. I'm not working on the machine just the engine witch makes it difacult to solve.Its up to me to reduce the engine wheight not craft wheight. Is a bitt frustrating but i like the chalenge keep up the good ideas.

#12 1 Lucky Texan

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Posted 06 June 2012 - 11:23 AM

Heres the real problem its not mine so every mod has to be aproved by owner he has spent lots of time and money trying to cut wheight and reposition wheight my job is as the engine builder to get the engine to the exact wheight specifyed. I'm not working on the machine just the engine witch makes it difacult to solve.Its up to me to reduce the engine wheight not craft wheight. Is a bitt frustrating but i like the chalenge keep up the good ideas.


do any of the newer plastic intake manifolds move over?

any titanium exhaust parts available?

#13 Fairtax4me

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Posted 06 June 2012 - 12:51 PM

I believe all of the new manifolds are shorter because of the TGVs, and bolt pattern is different, but if an adapter could be made from aluminum or thin stainless that may help shave a few lbs. Just don't know how the newer intakes would work with the old 1.8 idle control valve setup.
If done carefully I think you could shave the aluminum manifold down, then polish it for a nice finished look. Might mean sacrificing a manifold or two to find the limits though.

I'm sure there are a few places on the block and heads that could be shaved down. valve covers have those big ridges and 16valve cast on the outside, those could go. Not a huge difference but if you find lots of little ways like that, they all add up in the end.

Lightweight flywheel should be a must. The stockers are 23lb? Maybe more, I know I've seen 12lb versions. That's 20% of the way to your goal right there.
Act offers a 9.6lb flywheel for certain engines, not sure how interchangeable they are but you ca do some digging about those. Seem to be only around $250 as well.

Carillo makes lightweight rods for Wrx and STi blocks, maybe could save a few ounces there, but would cost $800. If you can get a set that fits a 1.8? :-p

Edited by Fairtax4me, 06 June 2012 - 01:00 PM.


#14 1 Lucky Texan

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Posted 06 June 2012 - 01:15 PM

not much but, maybe run without the TB cover and bolts.

find a tiny alt. there's just not much load for a regular one. over-drive it if you have to with a smaller pulley. give him a spare in case it doesn't last long.

Edited by 1 Lucky Texan, 06 June 2012 - 01:24 PM.


#15 ivans imports

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Posted 07 June 2012 - 09:24 AM

A justy alt might be lighter and have shaved the intakes before have had to do alot to try and cut wheight on the mud dragster to make it less front heavy. Cut off all the extra ears brackets ect whent to header instead of cast. Opps not the buggy where working on. The other option is to get more out of the ea81 was just below the hp spec needed thought that mabee tbi on it could bring up the hp i have it on my 81 brat engine works well and makes good power but have no idea what hp its actualy making any one know 81 ea81 with loyale TBI makes ? hp there are no specs for thiss setup

#16 ccrinc

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Posted 07 June 2012 - 09:39 AM

You can increase EA81 HP by using 1600 (EA71) pistons and decking the head 30/1000ths. This will give approx. a 10-15hp increase. We've done it many times for aircraft, hovercraft and mudboats. No other mods necessary, although switching a Weber carb also (allegedly) will add power.

Oh, and you can also do the SPFI intake as well. Not sure on the HP increase, but if you need to go from carb to fuel injected, this would do it.

Edited by ccrinc, 07 June 2012 - 09:41 AM.
addition


#17 ivans imports

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Posted 07 June 2012 - 09:46 AM

why whould you use 1600 pistons as they are very weak and break easly when a ej 2.0 piston go's right in the 1600 piston has two thick rings and fails between the comp rings the ej 2.0 piston has pin rings and better aluminum or at least a ea 82 piston has better ring spacing the 1600 ones are just to weak to be reliable have broke many in stock 1600 cars is the only problem ive seen in the 1600

#18 Frank B

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Posted 07 June 2012 - 12:17 PM

There you go, different pistons, shaved heads, better cam, fuel injection maybe, with the carbon fiber prop and other lightening, that ea81 will perform well. Then sell the ej18 to get some of the cost back.

#19 ccrinc

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Posted 07 June 2012 - 12:49 PM

why whould you use 1600 pistons as they are very weak and break easly when a ej 2.0 piston go's right in the 1600 piston has two thick rings and fails between the comp rings the ej 2.0 piston has pin rings and better aluminum or at least a ea 82 piston has better ring spacing the 1600 ones are just to weak to be reliable have broke many in stock 1600 cars is the only problem ive seen in the 1600


The EA71 pistons are no weaker than the EA81 pistons: however, due to the placement of the wrist pin, you get more thrust.

We have tried this: the EJ20 piston is NOT the same size: it's too small. Plus, you wanna see broken ring landings? Look to the EJ20 pistons! I'm sorry, sir, but this time you simply do not know whereof you speak.

#20 ivans imports

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Posted 08 June 2012 - 10:26 AM

the 2.0 turbo pistons are weaker than ea81 pistons doubt that i have sets of both out will look agian. Sory to tell you but i just put the 2.0 piston in the ea block to confirm and its a exact fitt to tight if anything. I a'm wrong somtimes thats why i check with the actual parts this do's not lie better check your specs agian.

#21 ivans imports

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Posted 14 June 2012 - 10:09 AM

The origanal ea81 looks like the motor you are talking about has been decked and has new pistons not shure if they are 1600 ones or not i put one wrx turbo piston in to see how it fit seems to be ok and the hight is good and the clearance is good tiny bitt loose but no worse than a ej 2.2 the wrx piston is lighter and a less resitance type piston had to press out the wristpin bushing to get pin to fitt but do'se fitt. Anyway thiss engine needs overhall but will reuse the new pistons cause they are still very good will put some 84-87 heads and a ea 82 carb on it should bump it up just a bitt and still be reliabble. We also wheighed the two engines there is a 100 lbs differance between them ej is just to heavy back to the ea 81

#22 doc_z

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Posted 04 July 2012 - 05:04 PM

All the stuff you listed is small, and I think 80# is BIG. Maybe something like alloy heads would contribute.
It sounds like a trim problem, though. Move heavy components forward...including engine, if necessary. Shifting the engine a few inches fwd. might do it alone.


Have a customer that has a hovercraft has a ea81 engine we put in a ej18 to up the power but was a bitt heavyer so he was having trubble getting the back end up. So the problem to solve is how do we take 50 lbs of of a ej 1.8 any ideas? have thought of trimming off edges and ears brackets and drilling holes in bell housing lighter crank pully mabee even titaium bolts lighter timing components.He has even whent from wood prop to carbon fiber prop but still have to lighten engine give me some ideas boys



#23 LPGsuperchargedBrumby

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Posted 05 July 2012 - 07:13 AM

if you are overhauling the engine anyway, and trying to get more power, it might be worth have a talk to Delta Cams about getting the cam ground to up the power in the rev band where you most need it....

i assume that being attached to a prop means that you will be running quite high rpms thru a belt redrive like a number of EA81 equipped light sport aircraft so a cam that is suited to that would help

#24 iceageg

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Posted 05 July 2012 - 09:38 AM

Try replacing every nut, bolt and fastener you can with aluminum ones. They are a bit pricey but you can shave a fair bit of weight from the engine as well as the craft itself (I know you don't have access to it). Lots of suppliers out there.

#25 ivans imports

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Posted 05 July 2012 - 09:56 AM

So i built a ea81 lightend up evry part posibble and had a cam made planed the heads used the 88 gl heads on the 81 soild lifter bottom end ported and polished with a ea82 carb and intake i ran the engine on the ground yesterday with the rad and exhaust from a car to tune it before install runs crazy good super snapy and instant throttle response and a light wheight package i gess about 100-110 hp next step is install and see how it works




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