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Author: Subject: GSXR Throttle Bodies
AntonUK

posted on 24/8/18 at 08:40 AM Reply With Quote
GSXR Throttle Bodies

Hi All,
Ever since fitting the GSXR 750 throttle bodies I have had issues with high idle. With the adjustment screw fully out the engine idle its up over 2k.

The tuner backed the timing/fuel back to bring it down in the ECU, but its always bugged me and would like to resolve it properly without spending a fortune on some Jenveys.

Anyone else had the issue and successfully resolved it?





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snapper

posted on 24/8/18 at 09:06 AM Reply With Quote
Sounds like either idle fuel or idle air control is not correct in the map
The ecu mapping for idle is more complicated than air screws as the ecu canít measure what your doing with the screws.
If you use the screws to change idle the ecu is compensating.
I think you need it mapped again, still cheaper than swapping to another type of throttle body





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SPYDER

posted on 24/8/18 at 11:38 AM Reply With Quote
I would first be checking for accurate butterfly balance and/or sticking throttle or fast running mechanism.
There are, probably, two sets of vacuum take-off pipes. What are these connected to?
One set presumably goes to the ECU (maybe not) but are the others blanked off?

Do you know what your manifold pressure reading is at idle?
What ECU is it?
Do you know if you are running Alpha-N or speed density algorithm?
Is it running "closed loop" at idle? Like snapper says, it might just end up chasing its tail.

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BaileyPerformance

posted on 24/8/18 at 01:49 PM Reply With Quote
This can be an issue with all ITBs, but bike are often worse as they are normally modified to respace for ports. Any changes to the linkages car end up with balance and idle issues.

As a general rule (assuming the throttle balance is close) i set the throttle stop on the high side and use ignition timing to bring idle down. It is common to end up with 2-3deg at idle. The advantage is the ECU can add timing in relation to coolant temp which enables the engine to start and run from cold without any throttle. So cold idle could be as high as 18deg, hot idle as low as 2deg.

We can help with setting this up and mapping.

Cheers Dale

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BaileyPerformance

posted on 24/8/18 at 01:51 PM Reply With Quote
...just to add, idle valves are not required, perfect cold start and hot idle can be achieved without.
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cliftyhanger

posted on 24/8/18 at 04:26 PM Reply With Quote
As above, balance is key (I use a morgan carbtune, absolutely brilliant and so easy to use)
The other issue I had with GSXR bodies is I needed to add a very light return sring on the 3rd body. Not sure why as everything seemed to be OK, but it struggled to fully return enough without when in situ. A bodge maybe, but it works.

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SPYDER

posted on 24/8/18 at 06:48 PM Reply With Quote
I fitted an extra return spring too, between 2 and 3. In addition I also fitted a larger cable quadrant which I offset to give a "rising rate" progression. Red dot shows approx position of spindle. The change of angle of the cable is allowed for by the little rose joint.
In addition the respaced bodies are bolted to a length of ally angle (underneath) to prevent them from moving about on the rubbers.



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motorcycle_mayhem

posted on 25/8/18 at 12:23 PM Reply With Quote
Quick sanity check - is the fast idle screw 'out' below the main idle. On these TB's with the Suzuki ECU the two screws have relationship with each other. Given that you no longer will have that relationship, if the fast idle screw is bearing against the main idle screw, it'll hold the main butterflies open.
Too obvious to overlook, but wood and trees and all that.

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Pigsy

posted on 25/8/18 at 04:57 PM Reply With Quote
Hi. I have the same problem. Im currently working on the GSXR itb's by using a 4 inlet/outlet manifold.You will need 4 tubes inserted between the throttles and head on the engine side. I have used the suzuki injector holes. the actual solenoid valve of the idle control simply opens and closes at the appropriate time to let air into the itb's. There are outlet holes on it, one takes the pipes from the manifold end outlet while the other just draws in air, preferably filtered. the solenoid opens and air simply bypasses the throttle flaps, which I assume should me closed at idle.

https://rennlist.com/forums/944-turbo-and-turbo-s-forum/1065448-new-itb-intake.html#&gid=1&pid=5
This image is two outlets to 4 inlets. Mine has 1 outlet to a skall log type manifolds which goes to all 4 inlets. I will try to upload a picture.

https://www.enginetuner.com/wp-content/uploads/2015/01/multi-point-injection-with-plenum.png?61cde2&61cde2
This simply explainsthe principle of where to site thing pre, and post a single throttle flap.

You may well have your answer already.I would like to do mine Monday afternoon. If it works I will let you know.
Alan

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Pigsy

posted on 25/8/18 at 04:59 PM Reply With Quote
,which I assume should BE closed at idle.
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