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Discussion Starter · #1 ·
So here is for all you that ask the good old question... "what if i remove the secondary throttle plate (STP)?....."
well here are the facts....
base bike: 2007 SV1000s custom mufflers, custom fiberglass airbox, TRE, UNI air filter:
MAX:
111.6 HP @ 9675
70.3 ft./lbs. @ 7650

Other points:
99.8 HP @ 7650
64.3 ft./lbs. @ 4800
107.8 HP @ 10250
65.6 ft./lbs. @ 10250

Removed STP: noted a loss of low-midrange power of -2.4 HP and -1.3 ft./lbs. between 2600-3900 RPM's
MAX:
112.1 HP @ 9860
69.9 ft./lbs. @ 7590

Other points:
97.6 HP @ 7650
62.9 ft./lbs. @ 4350
109.2 HP @ 10250
67.6 ft./lbs. @ 10250

*Then I took the STP's and got a little creative...I drilled a few 5/8 in. holes:
MAX:
113.9 HP @ 9990
71.2 ft./lbs. @ 6850

Other points:
100.1 HP @ 7650
64.7 ft./lbs. @ 4100
112.3 HP @ 10250
69.5 ft./lbs @ 10250

So I hope this gives you guys some new mod to go try on your own bike. oh, and i also did the primary and secondary throttle plate adjustments before each group run. the bike now feels more lively on the road, and pulls very hard from down low. it was even enough to trump a stock looking GSXR1000 upto 80MPH, thats when he passed me and stayed ahead, by less than a bikes length, to 130MPH were we stopped. So i reccomend this mode to everyone. Only down side i noticed was a loss of 2 MPG with hard use. I will post some "real" pictures when i open up my bike to start testing on a throttle body riser plate.
 

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Knowledge is Horsepower
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I tried removing them also. Only thing I noticed was the large MPG decrease.

Interesting find though. Thanks for real world results. Not worth the effort for 2 hp though and the point of no return is crossed drilling them.
 

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KNEE DRAGGER
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Nice work!

The largest gains I have found were from removal of the plates and shafts. Those shafts really restrict aifflow. It takes a few other tricks after that to get the STV motors not to throw errors but it can be done.

You can also modify the primary shaft a bit to get better air flow too!

I have two more sets of modified units in progress so I can try to post pics when completed, if I am ever home long enough to finish them.

-MS
 

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Discussion Starter · #4 ·
my main goal was to see what exactly would happen if you removed the plates entirely. i wanted to dispell the myth with some facts. the loss in MPG is due in part to a lack of atomization of the fuel at low rpm's cuased by the lack of velocity in the incoming air.

as for the 2 HP gain, it may not seem like a lot but when you look at the graph (or the "other points" ) you notice a smoother and longer power and torque curve. I used various equipment also to meassure what was happening (thermal couples, air flow and speed rate meteres, etc.) with the holes in the plates the air velocity increased by 1.6% over stock from 1500- 3500 RPM, with a 1.4 % increase from 3500- 5600 RPM. the most interesting part is that with the STP fully opened the velocity and density increased by 2.2 % from 5600- 9850 RPM, then steady at 1.8% from 9850- 10250 RPM.

Anyway thats just for all you to know, whether you do it or not depends on whether you think its personaly worth it.

**Note: for all you engineers on here....the % increase shown was velocity and total density NOT volume.**
 

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Interesting stuff. For 2 peak hp and rideability improvements across the whole RPM range, this sounds like a worthwhile mod.

Worst case, I can't imagine the throttle plates being too expensive if you drilled them and then wanted to go back to stock.

<edit> Just had a thought--why would drilling holes in the STVs affect peak power? The STVs ought to be completely open that high in the RPM range, and since only the edges of the STVs would be in the airstream, the holes in the flat face would seem to have no effect. Any ideas?
 

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Mentally Disturbed
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good info, :bleh::bleh::bleh:
 

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Discussion Starter · #8 ·
Interesting stuff. For 2 peak hp and rideability improvements across the whole RPM range, this sounds like a worthwhile mod.

Worst case, I can't imagine the throttle plates being too expensive if you drilled them and then wanted to go back to stock.

<edit> Just had a thought--why would drilling holes in the STVs affect peak power? The STVs ought to be completely open that high in the RPM range, and since only the edges of the STVs would be in the airstream, the holes in the flat face would seem to have no effect. Any ideas?
looking at the stv's in the full open they actualy affect the air flow quite a bit. that is to say they dont open an entire 90 degrees there is some slop that cuases the vaccuum of the motor to pull them slightly shut. the holes in the plates actualy work to allow more air velocity while at the same time increasing the wave pattern of incoming air. this then will allow better fuel atomization and better combustion. thats where the power gains and smoothed (and lengthened) power band come from.
 

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Well, I'm sold doing this mod on my SV.

Did you drill the holes using a handheld drill or a press?
 

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Discussion Starter · #10 ·
i did the first hole using a handheld and there was a little bit of flex in the plate so switched to a press. dont apply to much pressure just let the drill bit do most of the work.
 

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Double Dumb Ass
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Nice work Prophet! Can someone get this man a Mod-Monkey?
 

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Discussion Starter · #12 ·
ok so here the "real" pictures of the STP/STV modification. also there is a picture of the semi-ram air plate that i made. when on the dyno and air was forced into the raised tank openning using a fan i saw a 1.8 HP and 0.6 FT/LBS increase through out the rpm range. with out this plate and air added saw a 0.9 HP / 0.2 FT/LBS increase through out. enjoy.
 

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Nice post a definant must do mod. What are your findings on the riser plates and how much longer are you making the intake runners.
 

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Mile eater
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Are those really 3/8 inch holes? They look a little smaller in the pics.

I too noticed an increase on the dyno with a fan blowing in front of the tank that was spaced up 10mm or so. I have holes cut in the sides and back of the airbox lid.

Nice mod, I gotta try it.
 

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Thanks for the pics and all of the details. Your bike looks sweet too, and that means a lot coming from someone who doesn't particularly like black, and who thinks that most bikes better left mostly stock.
 

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Knowledge is Horsepower
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looking at the stv's in the full open they actualy affect the air flow quite a bit. that is to say they dont open an entire 90 degrees there is some slop that cuases the vaccuum of the motor to pull them slightly shut. the holes in the plates actualy work to allow more air velocity while at the same time increasing the wave pattern of incoming air. this then will allow better fuel atomization and better combustion. thats where the power gains and smoothed (and lengthened) power band come from.
The STV's lag the TV's a certain amount, how many degrees, I am not sure. The STV's do not have any "slop" since they are gear driven by a servo. But, I'm not sure if they are fully "open" (perpendicular) when you are at WOT. I'd have to actually look. You could adjust the STV TPS, but it may jam up the STV's if not adjusted correctly.
 

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Discussion Starter · #17 ·
as for the intake runners and throttle riser.....that project is currently on hold do to an unforseen issue with spacing and brackets getting moved, etc. i am however thinking of adding velocity stacks as was previously mentioned and i will play with different lengths.
the mechanical drive for the stvs has some freeplay in the gears. not much but its there.
i am adding some heat protection to the airbox today and am going back to the dyno on sunday so we'll see if that does anything. i will post pictures later.
thanks for the great comments everyone.
 

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Discussion Starter · #18 ·
Ok, so here are the pictures of what i did to lower/maintain a cooler intake air temp. i took her to the dyno and found no real increase in power (0.1HP/ 0.2ft/lbs. through out the rpm range). however the thermal couple showed a 18.9 degree (cooler) difference between having and not having the heat protection. next will be to make a heat barrier plate and try again.
 

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Hey prophet, what exactly are those pics of? All I can discern for sure is that there's what appears to be some aluminum foil.

Oh wait, it looks like you covered the outside of the airbox with foil. Is that correct?
 
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