hobbsy
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| posted on 28/8/07 at 03:29 PM |
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Removing R1 (5PW) Secondary Butterflies(?)
I hope I'm referring to the correct part - basically the 4 black plastic sliding "chokes" that are operated by vacuum on the
throttle bodies, you see them if you pop your air filter off and look straight down.
Anyway I was talking to a Formula Jedi owner today and he said to remove them completely and block off the two vacuum pipes (currently vented to
atmosphere).
He said they are a restriction and don't open as quickly as they should. Also that they are there to stop the power coming in too quickly for
when the engine is in the bike (throwing you off etc) so not needed or
wanted when the engine is in a car.
Also they don't open quick enough and this is worse when not using the bike airbox as the two vacuum pipes aren't connected.
It looks like a one way modification as the rubber diaphragms look like they are bonded on and will need to be cut off.
Anyone got any views on this? They do appear to present a massive restriction when down but equally getting rid could screw up the fuelling (lean it
out?) and also gas speed (higher for the same volume if going through a smaller diam etc).
Although is this why some people notice a big difference between throttle response in a carb'ed bike to an injected one (do the carb'ed
R1's have these).
Your thoughts gentlemen please.
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ChrisGamlin
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| posted on 28/8/07 at 04:13 PM |
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They aren't secondary butterflies, which only appeared on later R1 engines and are exactly that, a second set of thottle butterflies controlled
by the ECU to help throttle response and from bucking you over the back.
There is a Graves kit that disables those sliders (here) but the
difference in power is very little from what Ive read, maybe 1 or two bhp at most.
I know Paul Rogers (progers) has them fitted to his RGB car though so maybe he can comment first hand.
Chris
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smart51
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| posted on 28/8/07 at 04:59 PM |
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on carbs, you can open up the holes in the bottom of the slides to speed up the opening / closing of the slides. At full throttle they're all
the way open, so there is no restriction, is there?
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progers
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| posted on 28/8/07 at 08:05 PM |
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I have the slide kit fitted as Chris mentions. The way Graves do it is to slide a thin cylinder into the throttle body to hold the slide permenantly
open. As part of the kit they supply a restrictor to fit into the line to the fuel pressure regulator (which ups fuel pressure). This requires you to
get the engine remapped with Power Commander (they supply a base map for power commander to correct things).
The whole purpose of the kit is to increase throttle response, it does not give any real gains in HP. For racing its a slight bonus but for a normal
road/trackday car I would say the gain doesn't really justify the cost.
You can get better (cheaper) gains in power by having a good manifold, good cold air feed into the airbox and making sure your TB's are balanced
properly.
I also have the graves velocity stacks fitted (they increase the length of the trumpet to the TBs on cylinders 2 and 3). This gives a reasonable boost
to the midrange (3 hp or so).
Cheers
Paul
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