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Discussion Starter · #1 ·
After a bit of tech info here.

Anyone know how the secondary butterflies are controlled? Is it a servo with a varying voltage, a pulsed signal? stepper motor?

Looking to put a set of thou TBs on a project of mine and would really like to get the secondaries working to help boost torque.

Cheers all.
 

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Discussion Starter · #3 ·
So its based purely on throttle position and not RPM related?

Any idea on behaviour of the stepper motor? (voltage incriments etc...)

Cheers!
 

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What I meant is that the ECU uses the STPS in conjuction with the known step size of the stepper motor to put the valve in the position it wants it. This position itself is determined by the ECU based on RPM and TP (maybe gear position too, who knows).
 

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The motor makes more power, faster, without them.

They are sold as "constant inlet velocity" blah blah blah

In reality......they are just mufflers for the inlet noise.
 

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Discussion Starter · #6 ·
The motor makes more power, faster, without them.

They are sold as "constant inlet velocity" blah blah blah

In reality......they are just mufflers for the inlet noise.
While this may be somewhat true of the GSXR1000, perhaps its not of others?

Take the GSXR600, (no really, take it lol). Its running 38mm ITBs, now those are WAY huge for a 600, the thing gonna have about as much torque as a plant, hence the need for the secondary butterflies, to act as CV slides and help boost torque from the motor. Aparently it also allows the use of a much larger capacity airbox without it adversly affectly the low-rpm behaviour.

Now, while I agree that this may be a marketing ploy, there are others doing a similar thing (tho with different methods)

Look at the R6 / R1 setup. they look almost identical to CV Mikuni's from the outside, diaphram slides etc... but with injection. If there was not a need for this type of "airspeed conditioning" then why would other manurfacturers be concerning themselves with it too?

The option to wind the throttle on hard at any revs, in any gear and have the bike pull like a train is purely down to torque, not BHP. (hell, if you want a peaky motor, go get a 2T lol)
 

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Discussion Starter · #7 ·
What I meant is that the ECU uses the STPS in conjuction with the known step size of the stepper motor to put the valve in the position it wants it. This position itself is determined by the ECU based on RPM and TP (maybe gear position too, who knows).
Indeed, therein lies the problem, "who knows".

I wish someone did, would be nice to get this sytem working on my project bike, then I could stick the thing on a dyno and see if tuning the STCS really does make any difference to the behaviour of the engine.
 

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Indeed, therein lies the problem, "who knows".

I wish someone did, would be nice to get this sytem working on my project bike, then I could stick the thing on a dyno and see if tuning the STCS really does make any difference to the behaviour of the engine.

Are you sure you want to waste, err I meant spend your time trying to 'tune in' the STVS?
It's much easier to rip them out, add short stacks and gain 8hp+4ft.lbs. wouldn't you say?

Luckily for you I did "stick the thing on a dyno", before and after dyno runs when I removed the secondary throttle valves
AND THE ROD and added short stacks, showed gains all the way from 4,000rpm to redline, no loss anywhere,
the torque did get peaky though at 8,500rpm and that's without any fuel changes.
 

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Discussion Starter · #10 ·
Well, they arent actually staying on a GSXR1000, thats why I wanted to see if I could still use them.

Do you have any dyno printouts of before / after that you could put up? Would be interesting to see the results.

Granted the results of running with / without STCS is probly not half as pronounced on a litre bike than it would be on a 600, since 42mm ITBs on a 1000cc bike are much closer to home than 38mm's on a 600.

Seeing as Im putting them on a 1216cc lump anyway, guess your right that I probly wouldnt need the STCS system, but would be interested to see dyno charts of before / after removal
 

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its a great mod and worth doing in conjuction with other cheap mods like the stacks, plugs, and pair...

the hardest part of the mod is simply to get the sensor to think the dummy rod is in there correctly to avoid the fi light... better throttle response is really what you should expect from removing the plates and rod..
 

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Where can you get the "how to" on removing the secondary blades? And where can I buy the short stacks?
 

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Discussion Starter · #14 ·
Is that on a GSXR1000 after just having the secondaries removed, or did you do more than that at the same time? (pair mod, different stacks etc)
 

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Stam,

That is with short stacks mod too, am I right?

If so what is the gain just with the secondarys removed. It may gain more power and for dyno shootouts it looks good, but what I hear is most people that take them out go slower on the track, that is less throttle control.

Cheers, Craig.
 

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Is that on a GSXR1000 after just having the secondaries removed, or did you do more than
that at the same time? (pair mod, different stacks etc)
Yes, a GSXR1000k3.
The second dyno run is about a week later. The SAE correction factors are 1.03 & 1.05.
The 'all four 750 short stacks' and removal of the secondary throttle valves and the rod are the main
reason for the power increase on the second set or runs.
Other changes were lighter wheel (same tyre re-mounted on the new rim) 520 chain, new sparks and
a BMC race air filter.
In a later dyno session I discovered that the BMC was worth a 1hp loss (without a custom map that is).
Read about it here: DynoRUN#2: look ma BMCr 750ss Iridiums 520chain STV_no_more


Stam,

That is with short stacks mod too, am I right?

If so what is the gain just with the secondarys removed. It may gain more power and for dyno shootouts it looks good, but what I hear is most people that take them out go slower on the track, that is less throttle control.

Cheers, Craig.

Yes, all four 750ss combined with the STV removal.
I didn't dyno separately. I had seen enough info to believe they would work well together. Plus I am not running a full engine development program...
Did the people that took them to the track have custom maps made?
I can tell you that without a custom map the throttle response bellow 5k is worse.
I know a few racers that like them.
Yosh sell a doodad that locks the STVs fully open for racing. If their racers use it than they are doing it precisely for
improved throttle control only, as you will not gain any hp if you leave the rod and valves in.

I now have a custom map and I think the throttle response is improved quite a bit with the STVs gone.
Improved in the sense that the engine responds more immediately to throttle inputs than before.
Some people may not like this.
 

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Stam, that may be part of the reason some can't get it to work without them - mapping it right.

I seem to remember that some of the WSB teams left them in. Anyone know about that?
 

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So yeah Ive seen this work well on buds 1000. So much so that I'm following suit. Easy to do and throttle response is through the roof. Increases in power are also nice. Also might want to try taping up the velocity stacks. Increases power
 
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