MODIFICATION , EFI Electronic Secondary Stage Controller

[1988starter]

With my cam I get a lot more power with them open at 4K and beyond but I need them closed for tq. I have thought of changing it but I have too much else on my plate

[A20A1]

They are run off a solenoid? hmm...
I can see the solenoid keeping the butterflies closed by holding vacuum.
This function is like the thermovavle on the carb which bleeds vacuum to keep the secodnary closed when the car is cold.

In either case direct vacuum would still allow the secondaries to operate, and in mostcases increase the vacuum signal strength/responsiveness slightly. You will only be losing the ecu / rpm control functionality.

[A20A1]

Has anyone tried changing the RPM that these butterflies open and close... maybe an easy power mod?

easy... remove the solenoid from the box or get a spare one and then hook it up to a mechanical throttle tirgger switch... I'm not sure if power on or power off causes it to function... but as long as you can get the vacuum canister to hold vacuum for you untill you feel like opening the secondaries then it should work.

only trouble is opening the secondaries earlier then the drop in manifold vacuum occurs... this would casue the butterflies to remain closed till the vacuum dropped enough to open the secondaries.

You could always have a dual solenoid I guess that cuts off the supply of manifold vacuum and just bleeds of the vaccum before the secondary diaphragm allowing it to open prior to the drop in manifold vacuum.

[A20A1]

You can also do it the old fasion way and change the spring rates on the diaphragm... a weaker spring would open the diaphragm in the higher throttle where manifold vacuum is at its lowest... and a stronger spring would open the secondaries earlier overcoming the effects of higer manifold vacuum at lower throttle.

[Busted_Blue]

intersting. I was bored yesterday and a left my intake filterness. It was for just around the block since i was cleaning my throttle body. Anyways, i took it to 6 and at around 5k my car's deep tone from the open throttle body turned into a higher pitchs vroom. Sure sounded like i have something big under the hood but not going anywhere. I guess mine works then . will this more torque fix aid me?

[AccordEpicenter]

unless you have considerable mods, you wont gain anything from messing with the pretec point

[Busted_Blue]

unless you have considerable mods, you wont gain anything from messing with the pretec point

gotcha! I'm stock, and bored but broke so nothing in the works

[87-Lx-i-3Dr]

can i do this to my 87 Lxi ?

[AccordEpicenter]

86-87 intake manifolds dont have the dual runners, so no, only 88-89 lxi/sei

[cahil_1]

Out of curiosity what if you rigged the little control arm that is attached to the diaphram to wide open all the time. i'm just wondering if my torque would be higher at the lowend and throughout the rev cycle or would if just dog out because the air to fuel ratio would be to high early in the rev cycle. i might have to try this.

[cahil_1]

this is directed towards Starter88 were your butterflies staying wipe open? I took a look at mine and i think that they are already staying wide open no change. are they supposed to be down before 5000 rpms then open. i guess i will try and get the solenoid this week. let me know what you think.

[smufguy]

Yes it would. The 86/87 lxi on has single butterflies. I'd say your increase would be at least 20 hp, considering the 86/87 came with 100 hp? and the 88/89 came with 120 hp?

i doubt it, cause first off u got 8.8:1 on the 86-87 and 9.3:1 on the 88-89. Second u got different cams. third, u got a 4-1 header on the 86-87 and 4-2-1 on the 88-89. So i would say possibly half the power or even much less from it in stock form. U might get about 115hp or somethinglike that. Thats about it, and this is comparing to the stock form

[1988starter]

this is directed towards Starter88 were your butterflies staying wipe open? I took a look at mine and i think that they are already staying wide open no change. are they supposed to be down before 5000 rpms then open. i guess i will try and get the solenoid this week. let me know what you think.

Mine were alaways wide open. If you set yours to be wide open you will gain a little after 4K but the low end will suffer.

with the engine off they are open and below 5k they are closed

[cahil_1]

OK today i really got in there and verified that they are staying in the wide open position. so i am pretty sure that the solenoid is shot and maybe even the diaphram. gonna test the diaphram with vaccum pump. thanks for the help.

[Vanilla Sky]

ok, as you guys know, a lot of you guys are disabling the vacuum secondary butterflies on your EFI cars... do you guys think there would be any benifit of having it open at a set RPM as opposed to at a certain engine vacuum condion? i'll be upgrading to EFI soon enough and i think this might be something worth looking at, especially since solenoids can be had for cheap, and the wiring wouldn't be too hard to do... would be especially easy with an aftermarket ignition... so what do you guys think? whould i just take the secondary butterflies out? hook them up as stock? what do you guys think?

[AccordEpicenter]

you have anything even resembling a stock motor youll get way better power under 5k rpm if you leave them setup the stock way. Removing them or leaving them open all the time makes you lose a bit of power

[Vanilla Sky]

well, i want to keep them operational, but i think there are ways better than vacuum to control them...

i just want to run a minimalist vacuum setup, but keep as much of the reliability, drivability, and fuel mileage as possible... i just figured changing when it engaged might be better

[AccordEpicenter]

unless you have a significant amt of mods (intake/header/exhaust/cam or somthing comparable, changing the pretec point wont help much

[Vanilla Sky]

so, are you saying it would be of a bit of help but not on a stock car? that's pretty much what i figured it would come to...

[AccordEpicenter]

pretty much. I was running like high 15s when i was na, on the stock crossover point

[A20A1]

If you want to change when the secondaries engage then buy an adjustable secondary diaphragm like the ones use on carbs... or find a way to add a screw and washer to adjust spring tension on the diaphragm... this will adjust how much of a drop in vacuum you'll need before you get WOT on the secondaries.

[POS carb]

they are in fact RPM operated, the ecu triggers at a preset RPM; it just uses stored vacuum for the force, not direct engine vacuum.
Hack the ecu to think it's at a different rpm is what you are looking for. hell you can get a drag tach shift light and hook it up to that, some are even adjustable

[A20A1]

But you could hook it to direct manifold vacuum... and then adjust the diaphragm... it's much easie then modding ecu's

[AccordEpicenter]

id say if you dropped it a little bit itd help, maybe 500rpm or so... you should use an rpm activated switch to adjust the changeover, just wire it up to the solenoid in the mystery box instead of using the ecu signal. There is actually a vaccuum tank to supply the vaccuum to this solenoid to keep the butterflies closed, remember they are open until they have vaccuum to them, then they close.

[Strugglebucket]

id say if you dropped it a little bit itd help, maybe 500rpm or so... you should use an rpm activated switch to adjust the changeover, just wire it up to the solenoid in the mystery box instead of using the ecu signal. There is actually a vaccuum tank to supply the vaccuum to this solenoid to keep the butterflies closed, remember they are open until they have vaccuum to them, then they close.

that's exactly what i did. i have a rev switch from summit wired to the solenoid so that it switches at 4,000rpm instead of 5,000. it's very easy to do. i could probably make a how-to if anyone's interested.

it helps in my situation because i've got a bored t/b, polished/port matched intake, and head work done.