TOPIC: 2007 Buick Rendezvous 3.5litre V6

2007 Buick Rendezvous 3.5litre V6 10 Apr 2019 19:35 #133

  • GregK
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You mean like this?
lookee here
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2007 Buick Rendezvous 3.5litre V6 17 Apr 2019 15:54 #134

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Ok, so I promised an updated photo of my PCV and MAP re-jigging, so here it is:


Starting from the mid right side of the pic, you'll see the green Granatelli spark plug wires coming underneath the wiring for the MAP enhancer circuit. The sensor itself was moved from where you see the inverted vacuum cap in the manifold next to the blue potentiometer, just above the green wires, to where the factory PCV bung is, right downstream of the TB. I initially had the hose more than 2x as long as it is now, but since I've shortened it, I've gotten MUCH better results/mileage/economy (however you look at it).

Now for the PCV re-route: as this is a transverse mounted V6, only one valve cover is accessible without rolling the engine, so I can't easily show you the vacuum cap with a bolt in it that I used to plug the factory breather intake, so you'll have to trust me that it's back there next to the EGR valve and under heater hoses. That said, it's easy to see the upsized rubber hose from the nipple on the front valve cover to the factory breather source port on the intake tube, right below where the spark plug wires for the front bank cross the factory wire bundle. I wonder if there's a way for me to post a correctly oriented photo, as I see it when I lift the hood. That'll be another post, and I'll mark things with arrows and text.
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2007 Buick Rendezvous 3.5litre V6 17 Apr 2019 16:42 #135

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Hopefully this picture is worth more than the proverbial thousand words:



If you double click and zoom in with ctrl+/-, you should be able to read what's what.

the PCV re-route, again, is: the breather destination port on the "back" of the engine has been plugged with a bolt in a vacuum cap, but the breather source on the intake tube is re-purposed as the PCV reroute destination, with the PCV source location remaining the same as the factory engineers intended. what I like about this is that it maintains the direction of flow the designers set up, so if they optimised things, we're not fighting flows.
the MAP sensor got moved to where the PCV vapours were intended to go, but we usually put our vacuum cap...right behind the TB. it got moved from mid-back on the manifold, and that was easy to plug...so another vacuum cap. The metal strap the factory put on the stud that the engine cover attaches to, i imply flipped over and re-purposed it to be my MAP enhancer potentiometer location...a cable tie holds it there til I get around to fabricating a bracket I can stick the shaft of the pot through, like a proper circuit board does.

This is, in my opinion, the best the PCV re-route has ever been on this vehicle. I had teed the lines together, but somehow now the throttle response is better and mileage is up. because of the MAP enhancer, it doesn't vary as much when it the temperature goes down at night or in fall/winter/early spring as it used to prior to this circuit and relocating the sensor.

Next step is installing the EFIE to the upstream o2...but that'll be next week when I take her in for some new back brakes
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2007 Buick Rendezvous 3.5litre V6 08 May 2019 09:12 #136

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Yesterday I had some free time and got to thinking about my MAP re-location.
While I’ve seen slight gains, I haven’t been sure the sensor was seeing the full depth of the manifold vacuum, being attached to the former PCV orifice tube. So I pulled it, and with my Dremel, zapped off the small orifice and found there was enough material to flare the opening further.
I wish I had taken before/after pics, because the difference at the accelerator pedal is quite striking. Throttle response is more accurate than it has ever been: a feather’s weight of difference either way translates immediately. And the re/re and mod took maybe 10 minutes.
If I have a few minutes before the sun goes down, I’ll take a pic of the results, and try to find a reference pic of what the factory put on to show the difference.
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2007 Buick Rendezvous 3.5litre V6 28 May 2019 14:52 #137

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EFIE installed!
for some preliminary results on how it affected Wendy, go see the last post here
needless to say, I'm kicking myself for dragging my feet to get it put on.
as time goes on (it has only been 4-5 days since installation, and 210miles or so), I'll update the gains. these numbers are average combined city/highway miles since I got the vehicle (including the pre-groove period), and include extended idle times to warm her up in the winter.

I think the next thing I'll tackle is some water injection. I'm considering a closed loop system, with the BMW cyclone seperator back on the PCV re-route, the drain of which would feed a coil around the exhaust manifold, that would steam back up through a valve into the intake at the point I relocated my MAP sensor.
Stay tuned, gadgetfolk!
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2007 Buick Rendezvous 3.5litre V6 14 Jul 2020 07:53 #138

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Yikes, has more than a year really passed since I posted an update on my Wendy? Craziness...

Here's the latest: I've recently added a passive induction water bubbler. And I'm SUPER happy I did: for my past 2 tanks (68L, 18USgal), I've travelled over 900km (557mi) each, an all-time high. I set out a few years ago to see if I could achieve 1000km (619mi) on a tank, and it seems that I'm inching ever closer to it. this addition of about 8oz of water per tank has returned an extra 70 or so miles from each tank

To get to this point, I had to remove the MAP enhancer (it was causing very hard shifts of the transmission), move the MAP sensor back to the factory location, and re-plumb the PCV system back to stock, with a couple of modifications: the Breather line off the intake snorkel/tube remains at 3/4" ID, but the PCV line has returned to roughly the 5/16" stock to fit the T-junction I used to add the bubbler and it's needle valve to control moisture into the manifold. (see diagram below...I'll attach a pic later)

water does indeed cool the intake air charge significantly: There is one extended downhill run that I drive on a weekly basis- maybe 3 miles, with enough of a grade to be able to take my foot from the gas and coast while the engine/transmission do most of the speed control. From "normal operating temperature," I watched the gauge drop to almost below where this car goes into closed loop over this run - a good 30-40 degrees, from the combination of water induction and curtailed/reduced fuel delivery.

I did have to tweak the EFIE voltage a hair, and I may do so again if I keep getting these same results - I do want to take this as far as I can without a negative impact on how the car drives.
Right now, I'm kicking myself for not doing this sooner, because it was such a cheap and easy addition with such tangible results.

One thing I am noticing is that the oil might be a bit dirtier than usual at this point in its life, presumably from decarbonization...but my oil life monitor seems fine with it, as I'm on track for my first 10k km (6000 mi) oil change in this car since it came into my care. Another thing: the engine has never been quieter...and Buicks are known for being smooth and quiet!. The tires are annoyingly loud on the pavement now to me...friends are telling me I'm turning this vehicle into a deeper sleeper.
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2007 Buick Rendezvous 3.5litre V6 21 Jul 2020 21:04 #139

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Here's another thread where I've dug a bit deeper into efficiency gains vs quantity of water. I actually found a research paper by actual engineers about it, but they did static testing and computer simulation rather than real-world road studies. They also used a direct injection engine, but they got some pretty remarkable results because they could REALLY control the water .

water vapour in EGR

I'll reiterate my hope that whomever might still be following along here gives it a shot on their ride. I got the aquarium air stones, silicone hose, water bottle and fittings for less than $20 but I've already saved that and more at the pump....and I suppose I should finally take and upload a pic of my setup, shouldn't I?

Here’s a photo of my current set-up:
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2007 Buick Rendezvous 3.5litre V6 13 Sep 2020 10:57 #140

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So I put the MAP sensor adjuster back on the other day and had something interesting happen:

Wendy's engine stalled while I was pulling into a parking lot off of a major street (luckily nobody was behind me!) and wouldn't start until I removed the adjuster.
What I figure that means is twofold:
1 - the temp had dropped (it was the evening and the daytime was much warmer) so the air density had changed, but between MAP and EFIE on the o2, fuel delivery was trimmed to the point the engine wouldn't run, and
2 - Wendy's running about as lean as she can get.

I spent a bit of time adjusting the MAP, the EFIE (reduce the MAP offset, reduce the EFIE offset and a slight increase to the amount of water) and water induction so that hopefully it won't happen again. and it's working - I filled up the tank and have driven with these adjustments in place. normally it takes ~120 km to go from above the full mark to the full mark on the gas gauge, but it didn't move until 157km. those ~37km (~23 miles) are a further improvement of just under 30%. I'm going to keep an eye on this and keep everybody posted here.

I'm cautiously optimistic that I'll get the 1000km out of the tank that I set out to achieve when I started down the road with the groove on Wendy.
Stay tuned, folks! this stuff works for you if you keep working at it!

I'll
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2007 Buick Rendezvous 3.5litre V6 17 Sep 2020 00:52 #141

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I decided to look at the trip meter and range estimate when I got home tonight - fuel gauge is showing down about 1/3rd from full:

410 km since I filled up and 471 km to empty- that’s 880km (550mi) total range. I’m getting closer to my 1000km/619mile goal from the 68liter/18.5 gallon tank.
It’s not magic: If you’re diligent, the results come, friends. This stuff works! Get grooved, upgrade your ignition (increase spark plug gap, use the lowest resistance wires), intercept and modify signals from sensors to computer, treat your engine with triboceramics like Snake Oil (and use synthetic oils - it’s not expensive anymore: 2gal of Kirkland brand at Costco for $30!) and it all pays for itself over time. Wendy has 160 thousand miles on her now, and she still loves to run, and she runs smooth and quiet still.
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