I want to make sure I'm understanding the system and how it may apply to me. From my understanding, the IAB's would be open with the engine off but close when the car is idling because at idle, the control box applies vacume to shut it. But at I believe 4900, it releases the vacume effectively opening the IAB's (so no vacume will open them and vacume closes them).

Right now, my IAB switch's vacume line is hooked directly to the intake manifold, not a switch. I'm thinking that my IAB's are stuck closed all the time therefore giving me nice low end but makes it fall flat on the top end (like from 5200 on the curve changes angle to less of a climb).

Anyone agree? Here's my dyno...notice how it falls flat up top?



Here's my tuning settings...notice how they had to take almost twice as much fuel away above 6K?

V/T Cont
L->H: 4600
H->L: 4500

Wide Throttle - LVt
1000 -6
1500 -6
2000 -6
2500 -6
3000 -8
3600 -8
4200 -9
4400 -9

Wide Throttle - HVt
4400 +0
4800 +4
5200 +4
5600 -5
6000 -7
6400 -10
6900 -13
7500 -14

The only issue I see now is that I'll need to get it retuned with the extra air. Maybe just adjust it to like -7 all the way across? I'm sure they'll need to adjust the fuel from where VTEC is kicking in for the max tune.

Right now, I will probably just leave them open as I don't think I have the complete IAB system (control box etc) to effectively have them open and closed at the appropriate times.


Modified by Daily Interlude at 5:03 PM 11/8/2005

 

If you have the IABs conncted without the box/solenoid and NO check valve then you will have the short runners open all the time you are at WOT and long runners when you are at idle and cruising part throttle.

If you had the check valve then you would *always* be on the long runners. That would be bad.

The IABs default to "open" without a vacuum i.e. WOT. You can tell by pulling your TB and having a peek. When you start the car you can watch the IAB's close as the manifold pulls more vacuum. If you put YOUR car in neutral, open the hood and operate the throttle by hand you can see the opening/closing mechanism fluctuate when you cram the throttle open. On a stock car you could watch the IABs open after ~4900 rpm then shut again when you let off the throttle.

When I look at your Dyno I see the characteristic drop in torque from 3250-4250rpm indiciative that you are on your short runners. If you go to the Officiall Prelude Dynos Page you will see that same dip in torque on H22's tuned with a P28 (no IAB support) as well as people with the IAB shut off. Like my old H22 on a P28 (red line):


You can also see from stock dynos using the P13 ECU that H22s run real rich while in VTEC from the factory. That would help explain your leaning settings.

Pirate

 

My iab's where always closed as they where hooked up directly to the intake manifold (no control box or check valve or anything). They never opened up in the higher RPMs...so there is no opening and closing other than the closing when I first start the car (as there is always vacume to keep the closed).

Is this bad? I couldn't quite tell from the way you worded which was was bad...

I disconnected this direct connect (plugged the intake manifold) which kept them open all the time. I felt the loss on the bottom end maybe a hair and it felt like it pulled a bit harder on the top end. Considering the old configuration and it's current configuration, this should be expected I believe.

I was out here trying to get the stock 88 IAB thing to work but I could never get vacume to come out the back side of the valve/switch so it still remains open all the time.

And while most run rich from the factory, have you ever heard of someone gaining 20hp by tuning their fuel curve alone (with a VAFC)? Mine did...

 

If you have number 9 in between your IAB diaphram and the manifold then just remove it. Your top end will be better if your IABs do not open after 4900rpm.

Pirate

 

I don't have #9 or #12 or anything else.

I'm going to look further into getting my 88 IAB system working. It's all there apparently and the device says it's getting power like it should. It says that if it's getting power but not giving suction on hose #12 that the device needs replacing (not in your diagram...the hose actually labeled in the engine bay as I still have the 88 vacume control box on the firewall though none of it's really hooked up right other than the MAP sensor). I have another control box and the device from it did the same thing. I have to research on how the system should be connected...I don't think I have it right.

So w/ this said, I've always seen people disconnecting the hose to have them stay open all the time. Would it be better to have them open all the time (more air flow, right...at the cost of low end though) or closed all the time (so only 4 runners are used meaning less air flow but better bottom end)?

BTW, what's #11 on that diagram you posted? I wonder if anyone has any of this for sale...but then again, I'll have to deal with wiring into this mess of an engine bay wiring (stock wiring harness from 88 with OBD1 connectors and then an OBD0 to OBD1 conversion harness at the ECU). I guess I could try to hook it all up but would it be worth it? I plan on doing some more mods looking for ~240-250whp so should I just remove them all together?

 

Ok first IMO it is better to have them open all the time. Since when I punch it I expect to get some power, but that is me.

Refering to the diagram, #12 gets its vacuum from the manifold through #28, #9, and #25. #9 is a check valve that keeps the vacuum in the box (#12) when you stomp on the gas (manifold pressure goes to 1000mbar). When you get to 4900 RPM the ECU sends a signal to #11 (a solenoid valve) to open and release the vacuum in the box. When the vacuum goes away then the IABs open.

The IABs stay open until you are below 4900 at least with the throttle closed (manifold pressure is at 500mbar).

If you have the IAB diaphram (#34) connected straight to the plenum with a single piece of vacuum line then they will be closed at idle or while cruising (the manifold has lots of vacuum) but as soon as you crack the throttle they will open since the vacuum holding them closed goes away immediately.

Pirate

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PirateMcFred &raquo;</TD></TR><TR><TD CLASS="quote">If you have the IAB diaphram (#34) connected straight to the plenum with a single piece of vacuum line then they will be closed at idle or while cruising (the manifold has lots of vacuum) but as soon as you crack the throttle they will open since the vacuum holding them closed goes away immediately.

Pirate</TD></TR></TABLE>I was with you all the way until here. So you say that the vacume the diaphram will see goes away when you open the throttle? I thought the vacume pressure would rise when opening the throttle...

If this is all true, how does the diaphram get vacume to keep the diaphram closed before 4900 w/ a stock setup at WOT? From what you're saying, the vacume should dissappear therefore opening the butterflies...

I appreciate your help/patience!

 

just take a look at how they sit while the car is off...they should be fully open, then watch them as the car starts...they should close up, then watch as you apply throttle, they should open up gradually...

if they dont do that they are messed up....if it was me and they didnt work i would have them always open, the little bit lost below 4grand is no big deal....

ps thats how the stock cams go....they flatten out up top....

oh and good job tuning it, you picked up a lot of hp....nice work

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mgags7 &raquo;</TD></TR><TR><TD CLASS="quote">just take a look at how they sit while the car is off...they should be fully open, then watch them as the car starts...they should close up, then watch as you apply throttle, they should open up gradually...

if they dont do that they are messed up....if it was me and they didnt work i would have them always open, the little bit lost below 4grand is no big deal....

ps thats how the stock cams go....they flatten out up top....

oh and good job tuning it, you picked up a lot of hp....nice work </TD></TR></TABLE>So the intake manifold does loose vacume as you open the throttle?

BTW, I don't have stock cams...turbo stage 2 cams (don't ask though!).

And the tuning was really getting back what was lost somwhere/somehow...sub 150whp on an H22 with the mods I had is crazy. I about fell out when I saw that!


BUT, I'll have to play with it some. I'll hook it back up directly to the intake manifold and see if they open back up when I open the throttle. If not, I'll make sure to just leave them open all the time until I can figure out the stock 88 IAB system...

 

Think of your IM as a sealed bottle with a vacuum inside. When you open the cap on the bottle the vacuum goes away. The same thing happens when you open the throttle plate.

So when you are at idle or while steadily cruising your manifold has a lot of vacuum. when you mash on the gas it goes away.

In the above diagram #9 is a check valve. A check valve is a one-way valve. You can put it to your lips and be able to blow though it one direction but not the other. This check valve when properly installed would normally keep a vacuum stored in the black box under the IM which hold the IAB's closed until the ECU opens the electronic valve (#11 solenoid valve) at a certain RPM. When the ECU signals the solenoid to open the vacuum goes away and the IABs close.

Without the check valve the IABs would open directly after you opened the throttle in the setup you describe.

make sense yet?
Pirate

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PirateMcFred &raquo;</TD></TR><TR><TD CLASS="quote">Think of your IM as a sealed bottle with a vacuum inside. When you open the cap on the bottle the vacuum goes away. The same thing happens when you open the throttle plate.

So when you are at idle or while steadily cruising your manifold has a lot of vacuum. when you mash on the gas it goes away.

In the above diagram #9 is a check valve. A check valve is a one-way valve. You can put it to your lips and be able to blow though it one direction but not the other. This check valve when properly installed would normally keep a vacuum stored in the black box under the IM which hold the IAB's closed until the ECU opens the electronic valve (#11 solenoid valve) at a certain RPM. When the ECU signals the solenoid to open the vacuum goes away and the IABs close.

Without the check valve the IABs would open directly after you opened the throttle in the setup you describe.

make sense yet?
Pirate</TD></TR></TABLE>Sure except how does the engine get enough air when you open the throttle then? Is it expected to just float in? I'd imagine it still has to suck it in...open throttle or not.

If there is no vacume at open throttle, how does the fuel regulator get opened more to add more fuel?

Also, I'm pretty sure that the times when I had the intake off and revved the engine, it was still sucking in air therefore still has vacume in it.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PirateMcFred &raquo;</TD></TR><TR><TD CLASS="quote">
If you have the IAB diaphram (#34) connected straight to the plenum with a single piece of vacuum line then they will be closed at idle or while cruising (the manifold has lots of vacuum) but as soon as you crack the throttle they will open since the vacuum holding them closed goes away immediately.
Pirate</TD></TR></TABLE>

So if i did this i would just lose a little bottom/midrange but gain a little top end?
The whole purpose of the dual stage is to create turbulence at lower rpms and provide enough airflow at higher rpms right? Just making sure

 

longer runners work better for low end, shorter better for the top....

you will lose bottom end, and the top end will be the same, above 4500 its the same...

 

OK, I just went outside and to my amazement, the butterflies open when I got on the throttle with them hooked directly to the manifold. Just barely opening the throttle didn't make them open though. It doesn't need a WOT type of opening though. Anything more than a minor input opened them but if I gave continuously more throttle slowly, they stayed shut.

Learn something new everyday!

But the point is at low RPM, if I get on it, it's still leaving them open so I'm loosing bottom end some (except with minor throttle inputs apparently).

W/ that in mind, I guess I need to try to launch at at least 4200+ rpms when the way they currently are to avoid the torque loss.