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Guest Message by DevFuse
 

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Dual Hitachi 26/30 vs Weber 32/36 on an EA71


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10 replies to this topic

#1 Dirk

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Posted 26 August 2011 - 06:57 AM

From a performance perspective which do you suppose would be better and why?

#2 Dirk

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Posted 29 August 2011 - 07:18 PM

Bueller? Anyone?

#3 cubastreet

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Posted 31 August 2011 - 03:14 PM

If you work out the area of the chokes, the duallies will have more flow potential, but both will be restricted by the stock manifold and heads so it's going to depend on how much work you've done to the rest of the engine.

single weber will be easier to set up and probably a little more economical but the twincarbs will look cooler.

#4 Dirk

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Posted 31 August 2011 - 05:57 PM

Hey.

Heaps of porting and polishing to heads and manifolds.
Lightend flywheel.
Fully ballanced
Cam grind

Pretty much the works.

I have a dual carb manifold and also a single carb manifold that takes the larger EA81 hitachi.

Flow should not be a problem for either setup.

Like every greedy person I want good top and low end power.

So far as I have read, it would seem that the single weber would give me better low end and the duals would give better top end.

I would like to test this theory with some of you guys who have one or the other.

I would try both myself but I only really have the cash and time to complete one of these setups.

Cheers

Dirk.

#5 cubastreet

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Posted 01 September 2011 - 04:21 PM

I've just got a standard ea81 with 32/36 weber atm.

Real nice low and midrange, no top end but that's most probably due to the manifold and heads.

I think the weber's good for 120hp or so, but the manifold is narrow and has 2 sharp 90 degree bends which is not good.

#6 DR DLEX

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Posted 02 September 2011 - 12:20 AM

the 26/30 for the hitachi refers to the throttle plate size,thus two 26/30's are accually 52/60 total carb bore. compare this to the webber 32/36 and then do the math. hope this helps

#7 Dirk

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Posted 02 September 2011 - 12:47 AM

the 26/30 for the hitachi refers to the throttle plate size,thus two 26/30's are accually 52/60 total carb bore. compare this to the webber 32/36 and then do the math. hope this helps



Not really. spell it out for me.

#8 Dirk

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Posted 02 September 2011 - 12:52 AM

I've just got a standard ea81 with 32/36 weber atm.

Real nice low and midrange, no top end but that's most probably due to the manifold and heads.

I think the weber's good for 120hp or so, but the manifold is narrow and has 2 sharp 90 degree bends which is not good.



Cool. Thanks.

The other apsect is that the long manifold promotes good torque. The dual carbs technically shorten the manifold lengths so I could be sacrificing the low end torque for breathier top end power.

I wonder if the boxer design will get the most out of the dual carbs or if the weber is better suited.

I am crrently running the EA81 28/32 carb of a stock Ea71. It feels well matched at the moment. Certainly no benefit to a larger carb without the further mods.

#9 Dirk

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Posted 02 September 2011 - 01:10 AM

Not really. spell it out for me.



Sorry man. Was having a little moment when I wrote that.

I get wnat you are saying but unless I get my heads flow tested I won't know if I can make the most of the duals. Hence the dilema.

#10 cubastreet

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Posted 02 September 2011 - 01:15 AM

two 26/30's are accually 52/60 total carb bore


Not true, as increases are exponential

area = pi x r squared

so for the hitachis (26/30)
3.14 x 13 x 13 = 530 square millimetres for the primary choke
3.14 x 15 x 15 = 706 for the secondary

= 1236 per carb / 2472 for both.

a 52/60 carb would be
3.14 x 26 x 26 = 2123
3.14 x 30 x 30 = 2826

which would make total area 4949 square millimetres

32/36 is 804 + 1017 = 1821

#11 DR DLEX

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Posted 04 September 2011 - 01:46 PM

o-kay let me slow this down abit.

1. On a non turbo intake fuel/air system, the cylinder volume creates the vacuum in the intake thus sucking the fuel/air mix at the carb(s).The smaller the carb., the less availible mix=longer time to fill the cylinder=less acceration(i.e.resrictor plates in NASCAR).The larger the carb.( or # of carbs.) more volume of fuel/air=quicker acceleration(i.e.drag racing,six-pack hemi's,etc..)
2.Torqe is made by the the ratio -fuel/air to comrpession.The more fuel/air mix available, and the higher the mix is compressed,the bigger the bang thus more torque.

Now with that being said;the dual hitachi would be the choice,,,,BUT

,,,,hitachi's are hiachi's and chasing problems one is often a headache and two=weeks of nightmares.Having run duals on stock EA-71s for over 100,000
miles i've been there.

I would suggest that you try each set-up and see which one fits for you




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