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I posted this in another thread, but didnt get any response. Is the close enough to still prevent the back pulses and air from causing problems. The guy that bored it told me he would make new butterfly plates but then he said he could not make them so these are the stock ones.

 

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Thats not a problem, it's not perfect, but pulse wise it'll work just fine.

Because of the design and mechanics of those, you can use perfectly round plates and adjust 'em so they sit flat.
Unlike the TB, there isn't a sensor to get screwed up by that on those plates.

Personally, i think i'd just stick with the stock plates though, easier that way.
 

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they really aren't that hard. you could make them yourself if you want to:









well there are some pics i took when i made mine. hope it helps. i just used hardened aluminum plate. but brass would be better. something like 1/32" thickness

Russ
 

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He can't make them for the same reason Toofast couldn't make a new throttle plate. Throttle plates are an eliptical shape and your geometry better be good to make a new one.

Why not just take one of the old ones and using it as a template, make new ones a bit larger.

I'm impressed with Lude4ever's work.

But really this is not that important..so there is a bit of air leaking around the butterflys before they are opened up. I don't think the engine will care.
 

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I'm sure you already did, but make sure those screws are TIGHT.
They are split, also, so you can pound the split back out to make sure they don't come lose.

Engine inhaling a screw = bad.


Those plates can be perfectly round, they don't have to seal perfectly, nor is there a sensor on them, which remove the two problems with round throttle plates.
 

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i wouldnt worry about it, leave it as it is. they are closed from idle to 5k rpms, and may cause you to lose maybe 1-2hp max and 2-3 ft/lbs of torque max at low rpm (idle-3000rpm), wont make a difference at all from 3k-4k, and may even give you a 1hp and 1ft/lb from 4k-5k before they open. if you search you can find a dyno sheet from someone who pulled a few consecutive runs, with butterflies stuck open and with them stuck closed for the entire pull, and found that the optimal opening point is actually around 4500-4700 instead of the actual 5k set point. and also found that with them stuck open all the way, you only lose a few hp and a few ft/lbs of torque in the lower rpm range. so with them being about equivilent to being 10%-15% open from the gap, theoretically you would only lose about 10%-15% of the difference in power between being fully sealed and stuck fully open, at lower rpms.

for example, if at 3k you have 65hp with the secondaries closed like they should be, and 62hp with them stuck open all the way, thats a difference of 3hp. theoretically being open equivilent to 15%, 15% of 4hp is 0.6hp, so you would theoretically lose 0.6hp at 3k which is something to laugh at.

im trying to find that dyno sheet right now that shows the 2 pulls between secondaries being stuck open and stuck closed for entire pull. i'll post it in here soon as i find it, if i find it, then you can compare and decide on your own how much of a difference it would make with a slight gap like you have up to 5k

still cant find the dyno sheet, ben searching for like an hour lol

can anyone find it and post it in here? the dyno sheet showing one pull with the secondaries stuck closed for the entire pull and a second pull with the secondaries stuck open for the entire pull? you guys know the one im talking about, i just cant seem to find it
 

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Odd, I've read repeatedly (can't find it now, of course) that they open right around 4000 RPM, which is why the 90-91 d2a4 guys get such crap mileage on the freeway because at 75 mph the secondaries are wide open and fuel is flowin' free... ¿no?
 

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alanoneil said:
Odd, I've read repeatedly (can't find it now, of course) that they open right around 4000 RPM, which is why the 90-91 d2a4 guys get such crap mileage on the freeway because at 75 mph the secondaries are wide open and fuel is flowin' free... ¿no?
Most 90/91 cars have a B21A1, which do not have any butterflies at all.
 

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Whoa, you serious? Only the B20A(5) intake manifolds have butterflies? So do the B21A(1) manis still have the two separate sets of runners, just with air flowing through both at all times? If Honda thought it was a good enough design to even use it on later H-series intakes, why skip it on the B21?
 

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It was me that did the dyno runs.
They open at 4800 rpms. That is for all years of B20.
If yours shows 5k then something is wrong. Probably an over-enthusiastic tacho.

If you still can't find my dyno sheets I'll have a look for them later.
 

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Both.
It's operated by vacuum but the signal is done from the ECU.
It works a solenoid with 5v that opens the vacuum system.
 

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Pure ECU, there is a vacuum reservoir to hold them closed untill the ECU sends the signal to dump the vacuum and allow them to open.


Three out of three preludes i've test driven have had them open dead on 5k by their respective tacs.

200rpm is a bit small to argue over, don't you think?


EDIT:
Service manual page http://www.teaminterlude.com/documentation/3rdgen/62sf100/6-203.pdf says that in testing, you should raise engine speed to 5000rpm to test for them opening.
 
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