16V Bigport+20V Quads. Low Manifold pressure issues

[jondee86]

When the Adaptronic ECU runs in TPS only mode with V.E. tuning, it still factors some MAP input into the tune. It also uses the MAP sensor input for certain fuel compensations. This is because when the throttles open, the MAP signal responds more rapidly than airflow or RPM.



So, even if you don't have a lot of manifold vacuum, it is still worth having a functional MAP signal for the ECU.

Cheers... jondee86

[GeeEss]

Hi Jondee,

Re. Issues:
I finally got the Vac system finished today, using your basic layout and yes, it’s a hell of a lot neater than what I had. I will outline what I did at the end but first I have to say that – despite all that effort, my MAP vacuum is still ~ 70kPa - with ISCV attached (haven’t tried it w/ ISCV disconnected as I don’t see the point; with P/S & Air I need it.).

At the moment the cars not running right – it idles at ~3700RPM for 15-20 sec and then “pulses” I.e. too much air / not enough vacuum so the engine revs out, then goes into idle cut mode, and keeps cycling this process.

{Funnily enough, on my first tuning attempt it was idling rough but steady at about 900RPM – but this was because the throttle linkage was fouling on the Fuel Rail & only had ½ the proper travel – so the 100% TPS deflection value “learned” by WARI was only about 1200; about 50% of proper figure of ~ 2150.

I was quite careful with the vac lines, made sure all were properly pushed onto Barbs + secured with zip-ties so it’s unlikely a Vac leak is causing above issues but I’ll start it up again 2morrow & pour water all over intake & see what happens.

Re. Actions / Remedy:

Not sure what I should do;
1. I.e. just accept that this is the best vacuum I'm gonna get and tune according to these parameters. I took the car for a drive; yes the brakes seemed a bit lifeless but they were OK; not a patch on the AE111's in terms of feel though. . . and no I haven't tried turning on the Lights & A/C. . .

2. (Assuming I can't solve it) Take the car to a professional to see if they can diagnose / improve the Vacuum System. I don't like this option as its likely to involve considerable expense - BUT if anyone knows a workshop in Sydney with good 16V 4AGE+Quads credentials I might consider dropping in to see them.

Re. 20V ISCV:
Being as this beast seems to be the fount of all my problems I wanted to at least make sure I’ve plumbed it correctly. You said “When you look at the factory ISCV you should be seeing something like a 12mm tube on the airbox side, and something like a 15mm tube on the throttle side”.

I think I’ve got mine “wired” opposite to this, with 12mm tube running to Collector, and 15mm tube running to Airbox / Plenum as outlined by this article >:: DIY Stuffs < 1/3 down page >. Can you confirm the right layout; and whether (if I DO have this ass-about) this may be causing my problems?

Re. Layout:
I should have taken pictures I know but I’ll try & explain what I’ve done.

I used a modified Big-port Fuel Rail @ yourself and tapped 1/8 BSP Barbs into u/side of T3 Manifold about ½ way between Head / ITB Mating faces. I used the 4 Injector holes + had another 3 tapped into Rail between existing holes. I also had FPR hole tapped out ¼ BSP to fit a Vac union for the 20V ISCV. So I have 7 1/8 BSP outlet Barbs; 4 to ITBs, and 3 plugged.

Not sure why you didn’t mention it but I couldn’t believe how lucky it was that Fuel Rail Mount Hole Pitch (~ 87.5mm) = Pitch between Mount holes in ITBs for OEM S/T Vac Line Bracket; i.e. Fuel Rail bolts directly to ITBs w/o any modifications – brilliant!

In place of your custom smaller cylindrical Collector for MAP / FPR vacuum I used an eagle box I got from T3 Tuning. I tapped two holes in Fuel Rail / ISCV Collector and Piggy Backed Eagle / MAP Collector directly onto it.

I had the six 1/8 NPT | 5-6mm Nylon Barbs that came with it turned down to 4mm and ran 6 X 3mm Vac Lines to original 1/16 NPT Barbs on T3 Manifold; 4 to ITBs, 1 to FPR and 1 to Dashpot* / Oil Canister (this was running direct to little OEM outlet on top of #1 ITB but I re-routed it to use up spare outlet. I then ran 4mm Map Vac line to one end outlet on Eagle Box (other end plugged).

[jondee86]

OK... just a few random factoids that are worth going over, to make sure that
we are both on the same page

- Looking at my last log, I see that my hot idle is around 1000 rpm, with a MAP
reading of around 80 kPa. TPS zero, WT 86 deg, ISCV value 25 <== Note this !!

- From the Idle tab in WARI, ISCV minimum value 22, maximum value 100. It is
important that the minimum value be set lower than the actual value required to
maintain your target idle speed. If the minimum value is too high, the ECU cannot
bring the idle speed down to target.There is a separate compensation table for WT.

- You are correct (my bad), the larger tube on the ISCV connects to the air box.

- From the Aux Out tab in WARI, Aux 1 = Idle Control, PWM @ 250 Hz, and
Aux 2 = Inverted Idle Control, PWM @ 250 Hz. Obviously, your ISCV needs to be
hooked up to the appropriate ECU outputs, and have a switched 12V supply.

- Again, on the Idle tab, under Open Loop Idle Control, there is a Base Idle
Value table that needs to be completed. This is a kind of trial and error thing that
you create by starting the engine from cold and noting the ISCV value you need to
hold target idle at every 5 deg interval. I recommend getting started in closed loop.

- With the ITB setup, it is desirable that the ISCV be the only source of idle air.
Any other device or un-plugged opening or vacuum leak will raise the idle speed.
Therefore, check that your throttle butterflys close fully, and that they all start to
open at the same time when you operate the main linkage. Cap all un-used vacuum
ports. Check for vacuum leaks with a length of garden hose. One end in your ear
and the other probing around the intake side of a running engine.

- Turn fuel cut off by setting "RPM Higher" to >8000 rpm.

One way of validating the idle control system is to simply use your thumb to partially
block off the airbox end of the ISCV hose. If you can control the idle speed by moving
your thumb, and stall (or nearly stall) the engine by blocking the hose, the system is
good. Control problems, if they exist, will be due to a faulty valve, or ECU settings.

Cheers... jondee86

[GeeEss]

Hi Jondee,

All in all I think (fingers crossed) I have the Vac Layout sorted. Only??? is the ISCV {see below}.

I’m now getting 50kPa Map reading which is the target value given by the Harness / ECU supplier.

It’s all good with the 3700RPM idle; so simple it’s stupid. I cut my AE92 Throttle Cable down for the Quads but cut it a touch too much. In a nutshell the cable was accidentally over-tightened.

MAP: I removed the Dashpot line from the smaller Collector feeding ITBs, FPR & MAP and re-routed to the larger ISCV Collector. This alone dropped MAP reading 7-9kPa to 60kPa.

Idle = 50 < Min=50/Max = 70 > | Idle RPM = 746 (avg) | AFR = 14.9
Map = 60kPa | TPS = 0 | WT (°C) = 27-29 (0-35 sec) | ISCV value = Idle Value?

I was then advised to test the operation of the ISCV by varying the Min/Max idle settings; starting at 0 / 0 and incrementally increasing Max value. {Log File values below}

I then tried cranking it again to do this but the plugs gave out. They were totally black & wet on removal. The car has been running really rich ever since I put the Quads in {fuelling hasn’t been addressed because I was trying to sort out Vac issues}.

I put new plugs in and ran car at Default 40-60 Idle settings and . . Map dropped to 60kPa. . . . I go inside, have a coffee, come out & repeat, increasing Idle Max setting and I notice 2 things;

1. Varying Max Idle settings has no effect on Idle Speed; {faulty ISCV?}
2. MAP reading has dropped down 10kPa; now consistently 50kPa!!!

So now, Map readings are good enough to sort out fuelling, which is next step.

Readings from Log files {new plugs} are as follows;

Idle = 40 < Min=40/Max = 60 > | | Idle RPM = 1069 (avg) | AFR = 15.4
Map = 53kPa | TPS = 0 | WT (°C) = 37-50 (0-120sec) | ISCV value = 40?

Idle = 0 < Min=0/Max = 0 > | Idle RPM = 973 (avg) | AFR = 14.9
Map = 55kPa | TPS = 0 | WT (°C) = 52 (0-17sec) | ISCV value = 0?

Idle = 10 < Min=0/Max = 10 > | Idle RPM = 1045 (avg) | AFR = 14.9
Map = 51kPa | TPS = 0 | WT (°C) = 60-65 (0-32sec) | ISCV value = 10?

Idle = 30 < Min=0/Max = 50 > | Idle RPM = 1011 (avg) | AFR = 14.9–15.0 (0-22sec)
Map = 51kPa | TPS = 0 | WT (°C) = 55 (0-22sec) | ISCV value = 30?

Idle = 30 < Min=0/Max = 100 > | Idle RPM = 1034 (avg) | AFR = 14.9–14.6 (0-52sec)
Map = 51kPa | TPS = 0 | WT (°C) = 58 (0-22sec) | ISCV value = 30?


Re. “ISCV = 25” I’ve noted this but what’s the significance of this value?

PS: Are you absolutely sure about inlet / outlet routings on ISCV? I’ve Googled this but cannot find any consistent information on which pipe is inlet & which is outlet & if it really makes a difference which way ISCV is plumbed.

I had the larger 15mm pipe running to air-box and changed around @ your original suggestion (PITA job). Car seems to run OK & I can vary idle by blocking off inlet hose with thumb) but varying Idle settings @ above has little effect on Idle RPM– does this indicate a faulty ISCV or simply that plumbing is wrong way around & that I need to change back to what I had before?

[jondee86]

Hmmm.... so, one thing at a time...

ISCV min = lowest value to which the ECU is allowed drive the valve.
ISCV max = highest value to which the ECU is allowed to drive the valve.
IDLE value from Live Gauges = current setting of ISCV by ECU.

- To force idle high, set max to 100 and increment min up.
- To force idle low, set min to zero and increment max down.
- To let ECU do its thing, set min to zero and max to 100. Then the ECU
will set the valve according to the target position vs water temp table.
- Once the table is established, set the min value 2 or 3 units below your
desired hot idle value. Leave the max value at 100.
- When max = zero, the valve should be forced fully closed.
- When min = 100 the valve should be forced fully open (can't be sure
of that if max is less than 100, since I don't know if min overrides max
- If the valve is fully closed the engine should stall.
- If the valve is fully open, the engine should idle at 3000-4000 rpm.

Normally, the ISCV max setting will be 100. That allows the ECU to
drive the ISCV fully open to allow extra air for starting. Once the engine
is running, the ECU will drive the valve to the position indicated in the
target position vs water temp table.

Your actual ISCV values will be different from mine, as the flow
characteristics of your tubing setup will be different to mine. But the
setup principles are the same.

Cheers... jondee86