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

[GeeEss]

I am hoping someone can shed some light on an issue I’ve been having, namely low Manifold vacuum.

I am running S/T Quads on a modified 16V Bigport (10.5:1 Compression, Tomei 264 Cams). AE92

Car has A/C & P/S; closed air Intake; i.e. modified S/T Plenum running to AE92 Airbox.

Basically, according to AK (ECU+Harness supplier); my Manifold Vacuum should be around 45-50kPa but its reading around 90-95kPa i.e bugger all vacuum, at idle.

NOTE: AK said Engine has plenty of Vacuum

I have checked all hoses & connections - there are no leaks.

I also took off the T3 Manifold, enlarged the fittings (T3 Manifold came with 1/16 NPT to 2.5mm I.D. Barb, with only ~6-7mm of metal for hose to attach to so I drilled out holes and replaced with 1/8BSP 90 Elbows with a long 4.5mm I.D. Barb to ensure hose was properly retained.

I put it all back together and. . . there was no change in the Manifold readings at all.

AK quite rightly did say he doubted changing the fittings would fix the issue as he thought it was more due to the VAC layout so now I’m pondering the vacuum layout itself.

The Vacuum Collector Tank is bolted to Passenger side of diagonal strut on OEM brace, and originally had 7 Vac lines running to it;

 1 x ½” I.D. VAC line running from 20V ISCV outlet to larg(er) end union on Vacuum Collector Tank
 4 x 4mm VAC lines running from u/side of T3 Manifold (adj. to ITBs) to 1/8 NPT unions on u/s of Collector Tank *
 1 x 4mm VAC line running from FPR to 1/8 NPT union on u/s of Collector Tank.
 1 x 4mm VAC line running from ECU Map union to 1/8 NPT union on u/s of Collector Tank.

* There’s an average 500mm vac line run from ITBs to VAC collector.

 There are also two 1/8 BSP outlets on the top of the T3 Manifold in line with ITB#1 & ITB#4, running to Brake Booster & P/Steer union respectively.

The Manifold VAC gets closer to the figure (45-50kPa) recommended by Harness/ ECU supplier* when I disconnect ISCV; i.e. drops by about 25-30kPa to 65-70kPa. (but still varies a fair bit, with low / high readings = 57 / 72 kPa).

Disconnecting the FPR line has negligible effect on kPa readings. . . .

The car also runs bloody rich. . . . afraid to take it for a run (to test Brake / Steering operation) in case I stuff the Catalyst.

AK suggested I tap another 4 holes and run lines to a separate VAC Tank; i.e. drive just the ISCV off one, and the MAP & FPR off the other. He* said this was a “desperation” measure, as the Manifold vacuum should not be this low, but that doing this might help me isolate / identify the problem.

I’m pretty reluctant to do this, as it would start to make things really messy, with a whole spaghetti load of vac lines cluttering the bay, so what I proposed to do was run larger 6mm Vac hose for 20-30mm from ITBs then split each runner into two via a “Y” fitting & merge the other 4 lines into 2, then 1, then run that line via a Collector / Valve (@ OEM layout in AE111 Levin).

I was intending to try this out 2morrow but what I wanted to ask first was this;

Q: Could the location of the VAC collector (i.e. the 500mm run from ITB-to-Tank) be part of the problem? After all the Collector on the AE101 / AE111’s sits right on top of the Manifold. Would it be worth moving the Collector closer to the ITBs (i.e. to the bulkhead above the steering rack) or am I barking up the wrong tree?

PS: CSV files from ECU can be attached for Reference (if requested).

[Duk]

Basically, according to AK (ECU+Harness supplier); my Manifold Vacuum should be around 45-50kPa but its reading around 90-95kPa i.e bugger all vacuum, at idle.

How are you measuring vacuum, via an accurate mechanical gauge or from the computer?
What computer and MAP sensor? If it's an external MAP sensor, has the computer been set up for the sensor? Is the sensor known to functioning properly?

NOTE: AK said Engine has plenty of Vacuum

How is AK measuring vacuum?

[Animal15]

Do you really want da ISCV?
can u upload pic of your setup ?

cause i got same set-up with out ISCV no problem in vacuum .

sometimes the problem is the ISCV never shuts completely, it always stays open at the required amount to maintain idle even when you're not idling. That way it can 'catch' the revs when they begin to drop so you never stall.

If you want to use a ISCV then you'll have to make a setup similar to the standard 20v manifold where it takes the vac for the brake booster from a larger port behind throttle 1 & 4 so it gets a nice strong signal by tapping some holes into the T3 adapter yourself.
(thnx to Derek)

If you connect ISCV directly to other end of the eagle box it won't work.... (even if it works you not gonna have breaks )

[GeeEss]

Q: How are you measuring vacuum, via an accurate mechanical gauge or from the computer?
A: From the ECU

Q: What computer and MAP sensor? If it's an external MAP sensor, has the computer been set up for the sensor? Is the sensor known to functioning properly?
A: Adaptronic e420d with internal MAP sensor (its working fine according to AK)

Q: How is AK measuring vacuum?
A: Reading directly off ECU files I've sent him.

[knightrous]

I had a similar experience with when I put my MegaSquirt onto my 20V Silvertop recently. I found out after a fair chunk of googling (but it's not in any of the 20V swap or 16V + quad guides) but the Silvertop ITB's have their vacuum ports IN FRONT of the butter flies (well cylinder 1 & 4 are just behind, they provide vacuum to brake booster and reg) and they read basically mostly atmospheric... I drilled holes back where the Blacktop ITB's have their vacuum ports and the problem disappeared (It idle at 50-60kpa). The Silvertop ECU doesn't have a problem from this setup as it relies on AFM.

Quick picture of where I shifted the two vacuum ports on cylinders 2 & 3 and with them all connected to my vacuum manifold.

[GeeEss]

I'm using a T3 Manifold (which the TBs mount on) and drawing vacuum off that (it comes pre-drilled with 4x 1/16NPT fittings inline with each TB) so I am drawing vacuum from behind the Butterflies so I don't think that's the problem.

I am however also using custom Adapter plates (~ 20mm thick) that I had made up which basically spin each TB around 180 Deg so they are right way up (i.e. @ OEM in S/T). I did this because I think the T3 layout (with TBs inverted & throttle linkage on underside) is a PITA. This means I have an extra component & extra set of gaskets between the TBs & Head but I don't think this is the problem either.

Note: I am using the port on TB#1 for vac. for the Charcoal Canister. TB#4 Port is blocked off but I was going to use it for Vac. for FPR @ OEM (currently drawing FPR Vac. via Collector).

When the Map vacuum line is disconnected from the Collector and run straight to the VAC. port on TB#4 the MAP Vacuum then reads down to 32kPa (but readings of course vary heaps because it's only connected to 1 cylinder. Because of this AK (Harness/ECU guy) reckons the problem is with my Vac. set up (and not Cam timing etc)

As discussed I will (hopefully) split the 4 TB vac lines into two then merge via a small collector before running to ECU MAP port. Be interesting to see what Vac readings I get then. . .

I'm surprised that you're only using 4mm vac hose for Brake Booster; wouldn't have thought that was enough considering OEM S/T layout is 2 x 12mm lines.

At any rate I am interested in your Collector positioning; I will also move my Collector closer to the TB vac ports @ mentioned above to see if that makes a difference.

You're lucky you're still running OEM intake set-up; I feel like I'm trying to re-invent the wheel here (I haven't even turned on A/C yet - no doubt there will be further issues there. . .)

[Cuzzo]

Can you install a working known gauge in-line with the ecu to confirm the vac readings?

[GeeEss]

Been meaning to get one. . . .; I'm going straight to eBay after I log off. . . .

[Duk]

Basically, according to AK (ECU+Harness supplier); my Manifold Vacuum should be around 45-50kPa but its reading around 90-95kPa i.e bugger all vacuum, at idle.

NOTE: AK said Engine has plenty of Vacuum

Q: How is AK measuring vacuum?
A: Reading directly off ECU files I've sent him.

Something is a bit weird here. You say that the engine is only showing 45-50kpa of vacuum, but AK is saying that the engine has plenty of vacuum based on the "ECU files" (data logs?) you sent him.
Well the data logs can only log the output from the same MAP sensor that the computer uses to help run the engine.......

Have a look in the WARI software and check that the settings for the MAP sensor in the 'Analogue Calibration' page are correct.

From the manual: Page 21
"If you are using the internal MAP sensor inside the Select ECU, you may need to adjust the ‘Internal MAP sensor offset’, as shown below.
You should see a reading of 100kPa at atmospheric pressure."

[jondee86]

Running an ISCV will drop the vacuum in your collector tank. My smallport with
ITB's, 272/268 cams and an ISCV idles at 78-80 kPa. I have a 420e and run a
TPS only VE tune to get around the low vacuum issue.

Cheers... jondee86

[allencr]

What's the compression?
The brake servo needs a lot of volume, a sensor/gauge needs next to nothing and can be run off a single port, excluding pulsations with out a damper/restriction, so I'd use a collector for brakes only or 2 ports at most, directly - shortest distance & diameter, for a sensor/gauge/MAP.
1 x 4mm VAC line running from ECU Map union to 1/8 NPT union on u/s of Collector Tank.

What idle speed & what vacuum @11-1500?
Have you poured water all over that intake setup, choking it out or other testing??

What issue/s other then the specific number?

[GeeEss]

Haven't had much time to work on the car lately but I did have a couple of spare hours yesterday and I thought I'd give you guys an update.

File_A
I disconnected all 4 ITB VAC runners from Eagle Box and merged them together via an elbow and 3 Tee pieces, then ran the merged line straight to ECU MAP port via the small OEM Valve / Collector? used on the B/T Map Sensor line - the Map Vacuum dropped about 5kPa (in comparison with the Eagle Box set up) to 61kPa (average) but the readings were quite erratic (+/- 4KpA).

File_B
I then decided to cobble together a larger Collector to see if I could get more consistent readings so I made one out of an old plastic container about the size of a standard peanut butter jar. The readings were slightly lower (59kPa average) but much more consistent, varying only +/- 1 kPa, until 7.5sec into readings, when system seemed to lose vacuum.

File_C
I was curious to see what would happen if I took readings again after 1-2 blips of the throttle so took them again about 60 sec after above. Readings were quite consistent with Map vacuum = 59.2kPa average.

File_D: Cam Cover Breather blocked off:
I had previously (i.e. 2 weeks ago) removed the Plenum so things (i.e. TB VAC lines) would be easier to get to but this meant the Cam Cover breather port was left open to the atmosphere. (my layout has it plumbing back into the airbox duct before it reaches Plenum).

I was curious to see how blocking this off would affect the Map readings so did another run with it blocked off and noticed the MAP Vacuum readings dropped ~2kPa to about 57.5kPa. (This test is probably irrelevant but I'd thought I'd mention it. . . But WAS wondering whether it would be better if I just stuck a small K&N filter on the nd of it???)

Catalyst:
AK said car should be OK to drive (with ISCV detached) but it was still running very rich - mind you I only ran the engine for 60seconds or so at a time.

I would like to take it for a 15 minute drive to see how the steering & brakes behave but am worried I'll stuff the Catalyst if its too rich - is this a reasonable concern?

02 Sensor?
The other thing I noted is that in the WARI Program (in the "'Analogue Calibration' page I think) the program says there is no Oxygen Sensor attached which is incorrect (I have a Denso 4-wire @ 20V OEM). This may be another factor in the engine running too rich so I will run the test again & see what happens.

At any rate; AK reckons MAP Vacuum of 60kPa is OK as long as its fairly stable, but I'd still like to see if I can improve on that. At the moment all I've done is merge the 4 runners from the ITBs; i.e. they are still ~ 500mm in length (*as Collector was mounted on OEM Brace / passenger side - couldn't fit directly behind on Firewall due to OEM S/T Plenum).

I would like to reposition the Collector as close as possible to the ITB vac ports & take readings again as I wouldn't be surprised if there are some losses there.

Re. allencr
Compression has been raised from 9.4:1 > 10.5:1, but Cams are only 264 Duration.

Brake Vacuum is taken direct (i.e. not via Collector) via a dedicated port drilled on top of T3 Manifold behind TB#1 @ AE111 B/T. I know ppl say to run it via Collector but if so why didn't Toyota didn't do it (i.e. via the Collector on top of the OEM Manifold?)

Map vacuum on an AE111 is taken direct from centre of intake Manifold adj. to head (i.e. not via Collector); with a small in-line Valve/ Collector near the Sensor which makes me think there is a transverse runner in B/T intake casting drawing in air from all 4 runners (can anyone confirm this?).

Re. shortest distance: ECU (e420d) has integral MAP sensor so min. Vac line distance is ~ 0.8M. Again @ above; I'll move the Collector closer to ITB vac ports

Re. What idle speed & Vacuum. See attached ECU file.

Re. VAC Testing intake. Not comprehensively (i.e. w/ pump / spray nozzle & directing water up at all gaskets & ports on underside of Manifold - will get round to that in next 2-3 days.

Re. Other issues. None apart from the fact I've disconnected the AE92 Idle Up Contraption (didn't think I needed it with 20V ISCV) but wondering now; will ECU control idle when A/C comes on? - guess I'll find out when I turn it on - haven't got that far yet.

[jondee86]

Double post... deleted

[jondee86]

Not a good idea to block off the cam cover vent on a 16V, as that will
pressurise the crankcase.
The ECU has a an "idle-up" setting to signal the ISCV to admit extra air
when the A/C turns on.
I'd suggest you keep the "non-flow" vacuum connected items separate
from the "flow" vacuum items i.e. FPR and MAP signals from one small
collector averaging off all four manifold runners, and a second larger
connection setup for the ISCV and brake booster.
That little round plastic thing in the factory MAP line is a pulsation damper.
Small diameter hoses are fine for the sensor lines, as that helps to damp
signal fluctuations.
Although I only have 70 kPa (abs) vacuum at idle, I haven't noticed any
problems with braking, even when giving it a fair amount of stick.

Cheers... jondee86

[GeeEss]

Not a good idea to block off the cam cover vent on a 16V, as that will
pressurise the crankcase.
The ECU has a an "idle-up" setting to signal the ISCV to admit extra air
when the A/C turns on.
I'd suggest you keep the "non-flow" vacuum connected items separate
from the "flow" vacuum items i.e. FPR and MAP signals from one small
collector averaging off all four manifold runners, and a second larger
connection setup for the ISCV and brake booster.
That little round plastic thing in the factory MAP line is a pulsation damper.
Small diameter hoses are fine for the sensor lines, as that helps to damp
signal fluctuations.
Although I only have 70 kPa (abs) vacuum at idle, I haven't noticed any
problems with braking, even when giving it a fair amount of stick.

Cheers... jondee86

--------------------------------------------------------------------------------

OK, thanks. . .

Please clarify what you mean by "larger connection setup" <for the ISCV and brake booster.>

In addition to 4 pre-drilled ports on u/side of T3 Manifold for MAP Vac.; I also drilled two larger holes at each end of t/side of T3 Manifold for direct (i.e. not via Collector) supply of Vacuum to; 1. Brake Booster and 2. Power Steering.

The ISCV Vac was plumbed into Eagle box, i.e. was also drawing Vac. from 4 ITB runners serving MAP Sensor which apparently is why MAP vac readings were too low.

So, it seems that I need to swap around P/S and ISCV vac lines; i.e. so that ISCV vacuum is drawn directly from 1/8 union currently serving P/Steer < image>, and to re-route P/Steer line via the Collector.

My only ??? with that set-up; if I'm drawing ISCV vacuum from just one port / cylinder should I have another in-line Collector to smooth out the pulses from that cylinder?

Thanks; GeeEss