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Airbox Mod
Topic Started: Oct 1 2009, 09:37 PM (2,611 Views)
darkember
50+Member
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Has anybody tried the airbox modification for the Gen 1 Z range. Generation 1 are 2003-2006.

If done, has it made any changes to performance & more to the point will it affect the fuel system. More air will invariably lead to a leaner mix, will the fuel system need to be remapped.

Link to the mod:

http://www.riderforums.com/showthread.php?t=51422

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andy-750
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heard of this before and apparently makes little difference , best thing to get power is a can , airfilter n power commander which i have seen dyno readout for these mods on a 750 at 119 bhp up from 102 at back wheel z.750.
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DynoDude
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Hi

I have carried out this mod before on customers bikes and it does make an improvement.
I will dig out the dyno graph readouts so that you can see the difference for yourself.
I think the drawback with these engines and others like it is the fact that they are using fuel injection instead of carbs. I would like to fit a set of 41mm Keihin FCR's to one, then there would be a significant difference in power especially accelaration.
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Kawasakifreak
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Hey Dynodude,
Interested in your suggestion about carbs giving bigger improvements - any ideas why ?
Monster jet sizes perhaps ?
Kawasakifreak
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DynoDude
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Hi Kawasakifreak

Im glad you asked that question. Keihin FCR carbureters are in my opinion the best way of getting air and fuel into a naturally aspirated engine.
With fuel injection what you simply have is a tube (throttle body) with a flap in it that opens and closes (butterfly). When you open it air flows in and that is matched with fuel via the injector at the required amount for optimum fuelling.
Thats just putting very simply for now.
The slide in a FCR carbureter is also known as a vacuum plate. When this plate is lifted the vacuum that resides behind it literally forces a large column of air to enter the engine like a frieght train there is no restriction in the form of a butterfly valve air just keeps on rushing in. More air = more power!
I will post a dyno graph of two bikes with identical spec engines one fitted with fuel injection the other with Kiehin FCR carbureter the difference between the two curves is quite amazing. :022
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andy-750
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can the same effect be had by injection systems tho , just wondering coz race bikes and cars all use injection which i presume is because they can meter the airflow and fuel flow and so can mix it to the engines requirements and so get more power or is it an expense thing ?
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DynoDude
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Theres a couple of reasons why racebikes use fuel injection one of those is forced air induction via an air scoop in the fairing and the other is that a much larger bore throttle body can be used. As opposed to a carbureter where space becomes an issue.
The bigger bore of the throttle body allows more airflow at higher rpm's thus more top end power.That's one of the reasons why modern sports bikes rev quite high these days to take advantage of this.
One other reason why modern sportsbikes use fuel injection is the emmission control systems for less pollution.
The Z1000 is a perfect candidate for FCR's as it doesnt use forced air or even rev that high.I believe that the fuel injection is fitted merely as a way to get round the emmissions thing.
When a Power commander is fitted and mapped most of the emmissions control goes out the window anyway. :599
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DynoDude
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Here are the Dyno curves red line is fuel injection, blue line is FCR.
The throttle body was 45mm dia hence the top end power.
Whats the point of having that if you havnt got the midrange punch!
The "fun" part! :zrx z.750. Posted Image
Posted Image
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Kawasakifreak
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That's quite a difference Dynodude - especially the torque reading.
How useable are FCR carbs for part-throttle riding eg: town riding ?
Some performance carbs (eg: down drafts) can suffer from hunting & surging on part-throttle.
kawasakifreak
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DynoDude
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If they are set up properly then theres absolutley no problems at all low down.
Although sometimes carb icing can be an issue but Im sure that could be sorted out.
Remember those old slabside gixxer 750's from the 80's? They had Mikuni flatslides fitted as standard. I set one up a couple of weeks ago and that was absolutely perfectly behaved at low revs.
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Kawasakifreak
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Interesting Dynodude,
Flat-slide carbs appear simpler to service than down-drafts.
Can you recommend where I might find out more about both - any good tech guides/books that you would recommend pls ?
Kawasakifreak
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DynoDude
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Yes mate I think I'll have something somewhere for you to read.
I have mainly learned things via hands on experience with these devices as books will only get you so far. :444
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