Attention 88-89 LXI owners, read this

[AccordEpicenter]

Ive been looking into the 88-89 accord lxi intake manifold, and it has the dual stage manifold with the butterflies that open the secondary tract. I was foolin around today, and took out my cruise (never used it, dont work anyways) and plugged my vacuum line from my cruise into the vacuum actuator for the secondary butterflies, making them always open instead of closed. All i have to say is it really helped my lxi's powerband and esp top end, and made the car much noticeably faster. I def recommend you other guys try it and tell me what you think.

[turfnnsurf]

The other night i was taking apart a B20A5 intake manifold and noticed the same ports with butterflies controlled by a vacuum line. I was wondering if there would be any gain by keeping them open full time?? My guess it that they only open when the throttle is more then half way open to WOT. I had another thought also. What if a second "plate" could be installed above the original with the butterflies cut out? Kind of like a Spacer plate, maybe it would help increase TQ??

[AZmike]

Keeping the butterflies closed at lower rpm helps your low-end by using the longer intake runners. By sticking them open you may get slightly better high end (maybe around 4000-5000 before they would have opened automatically at 5000 and above), but at the expense of some low-end torque.

[AccordEpicenter]

maybe, im getting a complete 88-89 accord efi manifold and gonna go through it and eliminate the butterflies and what not. You know what, the same setup with the butterflies is on the H22A lude motor and people eliminated that stuff and ported the crap out of it for monsterous improvements in flow. I think this is probably better for flow and supplementing our powerband vs the single runner B16 manifold. As for torque, i noticed a small loss of torque running the butterflies open, but the top end power was worth it, try it. They are supposed to open at like 5k rpm but mine didnt and who knows when they really would so I said whatever and made em work.

[Einstein]

Originally posted by AccordEpicenter
making them always open instead of closed.

Are you sure they are open at idle? I imagine it takes a certain amount of steady vacuum to have them open.

Anyway, I would think a dyno would show the lower RPM suffers, probably up to 2500 RPM.

If it helps your top end, maybe your butterflies weren't opening in the first place because the valve was broke?

[A20A1]

I assume the efi secodnary butterflys are like the secondaries on a carb motor... If it runs off vacuum then it's probably venturi vacuum... though I'm not sure where the efi's venturi port is... I'll have to do a once over on the TB and manifold I got recently.
But anyways The venturi vacuum is not high enough at idle to open the secondaries.
And If you use manifold vacuum then the secondaries would close the instant you pressed the gas.

Venturi vacuum increases as rpms increase

Manifold vacuum decreases as rpms increase
it isn't totally true since it's actully more dependent on the amount of throttle.


Oh and to let you know some varriations of vacuum controlled plates act in the opposite direction. Vacuum to a diaphragm holds the plate closed and as vacuum drops a spring inside the diaphragm or outside on the throttle shaft, pushes open the plate.

[carotman]

The butterflies are actuated by vacuum (they close when there is vacuum)

There is a vacuum canister that allows them to remain shut until the pressure is releived by a valve

[1988starter]

Which tube controlls the secondary butterfly

[AccordEpicenter]

Its hose 13, and when there is vacuum they are opened, not closed. I was noticing a little better performance around 4k.

[A20A1]

Ok so I went inside the shed to check out the efi parts.

Turns out the secondary plates are spring loaded... and manifold vacuum holds them closed.
Which is good cause I don't see anyway they could get enough venturi vacuum @ the TB.

Originally #13 was controlled by the ecu (I'm assuming this cause it routes into the black box)... Which ment even though manifold vacuum dropped under acceleration the ecu still decided when, where and how much to lower the vacuum signal to the secondary diaphragm that controlls the opening of the butterflies.

When you hooked the vacuum from the cruize control to the secondary diaphragm, you bypassed the ecu and basicly hard wired in a manner of speaking, the secondaries directly to manifold vacuum.

>edit
__Ok so there was a little misinformation in this last part... I'm new to efi___
>/edit
Now I'm guessing the ecu isn't compensating for the secondaires at low rpm... it's still controlling the a/f mixture based on #13 still being hooked up and working properly (but it's not since you bypassed it). :D

[Sean]

ecm bases fuel calcs on load. if vacum drops ie more load ecm addsa fuel

[A20A1]

hrm... ok I got that last part wrong. I'm new to Efi

[AccordEpicenter]

did any of you guys try it?

[1988starter]

When my car gets back from being fixed from the damage my gf did to it I will try

[RedneckRicer]

so basically you just hook up the cruise control vacuum line to the #13 Vacuum lines original location?

[AccordEpicenter]

there is a vaccum actuator that moves a linkage on the side of the intake manifold, and I switched it with the cruise control vacuum line, but i also tried the fuel pressure regulator's vacuum line and left the hoses off the regulator and that boosts your fuel pressure. Im trying to see if it gives any real gains, i felt my car pull harder at and after 4k... tell me what u find out.

[RedneckRicer]

i'll have to check that out tomorrow, free power is a good thing, lol

[1988starter]

OK I gave it a try it plls a lot harder after 4,250 but I have lost a bit of gas mileage

[AccordEpicenter]

thats exactly what I felt. Ill have to see about the lost gas mileage.

[1988starter]

I actually had an extra unused vacume port on m,y intake manifold so I pluged it into that.

[AccordEpicenter]

I do too but i had the Vaccum line laying around for the cruise and i figured itd be easier to do that

[Swan]

what exactly are you people talking about?? I found the "13" line that goes from a box against the firewall on the left side, that goes all the way around to the other side of my engine..... but what do I do with it??? can someone give me detailed instructions?

[1988starter]

ok here they are sorry they are so fuzzy what I did was remove the tube that goes to the coltroll diaphram and plug it with the plug that was on the TB then connect it to the empty port (tube to the right in pict 2.


http://www.geocities.com/geezpict/cai/butt.txt

http://www.geocities.com/geezpict/cai/butt2.txt

[rare_89lxi_coupe]

oh.when you put it that way it's all so clear....

[rare_89lxi_coupe]

it was interesting of you to think of this, though I'm in need of all the gas I can get and I need to save it-Julie is a poor white girl. LOL. is there a significant difference?

[1988starter]

If it is too much ifference you can alaways switch it back

[InfinityAudioLXi]

I think its just me but WOW i am so damn lost by just reading this! maybe i'll have to look at the engine itself because I have NO idea what, and where, the hell #13 is, and what, and where the cruise control thingy is. =o(

[LX-i 4EVER]

I tryed it, and did you notice that when you rev it up a little bit in neutral that the rpm's drop quickly? I noticed it, I was just wondering if you did too.

[InfinityAudioLXi]

okay sorry about being so retarded but i did figure it out now! thanks for listening to my stupidity! lol i'll try it and respond

[Strugglebucket]

I know this is old but I still have a couple of questions regarding the secondary butterflies. The '88 and '89 shop manuals don't even mention them, save for picturing the bypass solenoid in the black box.

First question: Is the operation of the actuator dependent upon throttle position or rpms? Or something else (map sensor)?

Second question: Does the solenoid that controls the valves function as a simple open/close or can it vary the amount of vaccum (gradually open and close)? I know all it takes to find out is to look at the engine while it's running but mine is taken apart right now:(

[AccordEpicenter]

it opens at 5000 rpm, its only rpm dependant... only if the engine is up to full operating temp. It is digital open/close operation, so its either working or not, no variable vacuum

[Strugglebucket]

Aha! So if it only opens at 5,000 rpms, that's why the people that left them open felt gains around 4k.
The reason I was asking is because I am debating whether to use the secondary butterflies or remove them altogether. I'm kinding leaning towards removing them now.
The only concern I have is what was mentioned before about the revs dropping faster-meaning it would be tricky to shift and stay within the powerband using the stock accord gears. I know that Darryl from Openloop removed the secondaries from his car and likes it but he also said he's using some really tight gears in his tranny.

I wonder if there is a way to make the butterflies open and close gradually? If you could somehow do that it seems like you would be able to increase power throughout the entire range. It would probably be a lot more complicated than I'm imagining right now but it's just a thought.

[AccordEpicenter]

no if they open or close gradually youll fuck up the manifold flow and lose power. Ive found through experimentation that to leave them in place and operating so they open at 5k provides the best acceleration. The torque gain is quite noticeable

[Strugglebucket]

So you're saying those little square runners provide optimal response up to 5k?
What if you've got a bored throttle body, polished manifold, and p&p'd head?

[AccordEpicenter]

then you might wanna figure out a way to bring the pretec engagement down a bit

[DanLXI88]

Hey AccordEpicenter alot of time has passed since you first posted on this. Do you still have the same setup or did you it change back ?

[AccordEpicenter]

its running the stock way, closed to 5K opens after that... i was thinking about messing with it more but id rather finish my project engine

[Justin86]

Well I have a 89 manifold now and I was thinking about porting to then I though whay not just remove the butterfly valves completely. When I get another manifold I will try it, but I have to wait of a local yard to pick one up first.