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Guest Message by DevFuse

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EA81 engine

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5 replies to this topic

#1 xMcCl3llandx



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Posted 06 April 2014 - 11:12 AM

how can i get more power without tearing down the engine?

#2 bratman2


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Posted 08 April 2014 - 08:49 AM

Weber would be number 1. Two inch exhaust from Y pipe back with a Magnaflow muffler or similar. Also change your thermostat out for a 180 degree, lower if you don't need the heater much. Coolant runs through the intake and heats the air charge. Probably gets you into the high 70's!!!

#3 tweety


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Posted 28 April 2014 - 06:05 AM

You could supercharge it.  All parts are bolt on with some welding here and there.  There are pro's and cons.


Two types of SC.  Blow thru and suck thru.  Blow through means air only passes through the supercharger, the common manner that supercharged cars exit the assembly line.  Suck through is an easier method with air and gas passing through the SC.  Hence with suck thru the sequence is carbie, SC then manifold  whereas flow thru is SC, carbie then manifold.  Subsequently the latter needs its carbie to be sealed to stop air escaping.


Manifolds before and after the SC need to be made.  Lets stick to suck thru...a method I've tried on my EA81 powered trike.


The good-  an increase of around 33% in power output for 74hp to over 100.  Torque increase up by around 30%. No lag like with turboes- power is from idle.  (tune graphs are of the first tune....it had 3 dyno tunes in total but you'll get the picture)


The bad- economy.  Expect a drop of around 15-20% after a proper tune.


You need to ensure your engine is in top condition.  I geared my supercharger to make 4psi and achieved the above figures on a stock engine (dyno graphs below) and 8psi is ok to but any more and other issues come into the mix because of the stresses involved.  Blow by increases.  A catch can is a must in most cases.  I tried water injection to improve economy but with 4psi it was a waste of money.


So what is needed?  A dellorto or weber carbie was easiest to use for my project but it ends up wide.  The carbie should be angled a little towards the SC.  A supercharger.  The most common used is the Toyota units either SC12 or SC14 of the 1980's, the 14 just being longer with more output.  This unit comes with a 5 riubbed pulley so you need to attach another one on your crank pulley. A third pulley needs to be adjustable to allow the belt to be really tight. The belt needs to be lined up correctly.  The original SC pulley has a clutch as OE. However on a suck thru set up this is not possible. Hence that clutch needs to be secured so it doesnt turn.


The custom housing  between the SC and EA81 manifold has to have a blow off valve.  This expensive piece is necessary for backfires, to stop the force going thru the SC and causing damage. It proved its worth.


A bonnet bulge might be needed. 


Mandatory is to not have air leaks.  Dyno tune is a must.  It is difficult to get the right jets to suit all rev ranges.











Edited by tweety, 28 April 2014 - 06:12 AM.

#4 tweety


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Posted 28 April 2014 - 06:09 AM




#5 xMcCl3llandx



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Posted 03 May 2014 - 10:50 AM

do the EA71 heads have a smaller combustion chamber than the EA81 heads?

Edited by xMcCl3llandx, 03 May 2014 - 10:58 AM.

#6 jono


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Posted 10 May 2016 - 04:27 AM

very good question



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