TOPIC: 2007 Buick Rendezvous 3.5litre V6

The wheel bearings/hubs and brakes were done last night, and in the little driving I've done since, I've noticed the silence of the running/rolling vehicle has surprised pedestrians. Maybe the post-groove whistle that some vehicles achieve is a safety feature!

One thing that will definitely improve mileage numbers is the new plugs and wires: it idles just a small bit higher now - maybe 100 rpm, so opening the gap and making a larger, stronger spark will get that back to or below factory-spec "normal" as far as the computer is concerned. With luck, I'm hoping for 50+ mpg combined economy, or double the gov't rating/estimate. RVS treatment of the power train might even beat that. I'm still curious about the emissions data - looking for a way to get numbers on that.

So, I've been trying to show y'all this for a while from my mileage tracking app



You will notice on the right hand side of this graph that there has been a significant "evening out " of fuel consumption, with a few exceptions:

where the consumption line crosses the average line 13 data points from the right is where I did the PCV re-route, pre-groove. it got to be rock solid around 9.5L/100km, and I can't explain that first wee spike except maybe it might have been the computer readjusting to the change from winter to summer gas.

to the right of that, the peak at 6 datapoints from the right of the chart is where I did the groove. quite obviously, all of the idling to reprogram the ECU twice ate a LOT of fuel...not to mention the "drive it like it's stolen" part of the re-program

The very last datapoint on the right is today's fill-up. Since the PCV re-route, it still seems to be on a downward trend, albeit ever so slightly. maybe I gave too much credit to replacing my front wheelbearings and brakes. (I was expecting a bit more improvement from those fixes, frankly, especially considering the noises from my front end).

I'm still waiting on my Granatelli spark plug wires to replace and upgap my plugs, but that's not going to happen before this weekend's 400+ mile round trip to a wedding. I'll be SUPER happy to have fuel left in my tank when I get back...so stay tuned for a roadtrip update on Sunday!!

You are doing a superb job of documenting Wendy's progress. (I like that name it sounds like a pretty breezy friendly girl )

Will be interesting to see your comments on the Ignition upgrade. I'd expect a deeper exhaust note, better throttle response, and a really flat stable idle. I spend a fair amount of time listening to an engines idle, can tell a lot from it. Economy should improve too, IF you keep the foot out of it!

Have a great time at the Wedding, those are about the best gig to play, IMHO. Safe journey!

Tracy G

Thank you, sir! It's fun and easy with the right tools, like most jobs, if you're into doing the work.

I'm having trouble deciding where to set the plug gap. Ron's suggestion is to start at 25% over spec and keep increasing from there until the engine stumbles or mileage decreases/economy suffers. because it's a pain to get to the back plugs on this, I'd prefer to get more bulls-eyed before I go ahead.

Factory spec is .060", so 25% above that is .075"; my wire gauge has one at .080" (33%), so that's where I'm thinking just for simplicity's sake. with ~20000V coming from the coil, and not getting sucked up by the wires, that should make for a sizable spark...

(as an aside, I bought Aaron's ignition book. lots of food for thought in there, and very logically presented/put together...maybe someday I'll put some brainpower into figuring out how to make it work for this vehicle)

Greg, take an Ohms reading of your old wires when you do the swap. Then the same on the Granetelli's, it blew my mind to see Zero Ohms on those Granetelli's! The higher the Ohms reading on the old wires, the better the Granetelli's will work. 80 thou is a BIG gap--heck 60 thou is a big stock gap as well. Might compromise and go w/ .075" if your gauge has that size. This might allow for more time/miles/ gap growth and give longer service life. I'd put a small dab of silicone dielectric grease in the Granetelli spark plug boots too, if they come without it. Will likely be years before you change out these new plugs, don't want those boots sticking to the plug ceramic esp. if it's an awkward angle to grasp and twist the boots on any of the plugs. Based on my own experience.

Yes Aaron Murakami is an amazing guy, that Plasma Ignition download he sells is a real Gem! He cane up w/ an ingenious short-cut to create the Plasma effect, and Man oh Man, it is one Mean Spark! IF you ever do do that build, get in touch w/ me, I have a source for the diode blocks bookmarked, and some extra needed materials too. A Plasma spark ignition build has to be done Just So...

And, Aaron Murakami's info is the reason I found the Gadgetman Groove to begin with.

have a Great time on your trip!

Tracy G

I've got a set of Fine Wire Iridium plugs to put in place of the factory platinums. The harder material is supposed to last longer, and be a better conductor than platinum. And Granatelli has shipped my wires -a non-stock item that had to be made- but they won't get here in time for the weekend. (FedEx ain't what she used to be, but that's another story...) and I have a pot of dielectric at the ready, right next to the anti-seize...all I need is to find that sexy magnetic spark plug socket I got...

Just a quick update on instantaneous mileage results:
It's been pretty hot (for here) and humid, and today my readout hit 0L/100km! And held it for a good 5 seconds at 40mph on a straight and level road. From there it went up to 3.5L/100km until I had to stop. That's 60+mpg. Unbelievable. On 89octane E5 with a milder MPG remedy than the original recipe - only 5 aspirin.
I think the readout comes from injector duration. This would imply that the engine was running off of vapours from the PCV reroute, but also from the evap system.
I haven't yet replaced plugs/wires. I'm reluctant to mess with what I have going on in case it goes away. Then again, maybe it will solidify gains and increase them.

What??? You got 60 MPG??? I see something about you did it for 5 seconds.
I do get 45 MPG results for 10 seconds or so with my rig but then right back down to normal.
Were you using the Scangauge or Enginelink to get the figures?
That would be outstanding if this is sustainable.

No sir, I got better than 60MPG for a half-mile stretch PAST the 0L/100km period, the one that lasted about 5 seconds.

There are a little less than 3.8 litres in a US gallon and just a hair under 62 miles in 100km.
3.5L/100km is about 65MPG, round numbers, close enough for horseshoes and hand grenades.

EDIT: It's actually 67.2 MPG

But that's beside my points.

The instantaneous mileage readout on my instrument cluster obviously calculates fuel delivery based on pulse width of the fuel injectors. Unless that zero reading was erroneous, the engine was getting gasoline vapour to burn from the EVAP system as well as petrochemical soup in blow by re-routed to the intake air stream by our PCV re-route. Or the engine was running on humid summer air. (Truthfully, I think the evap vapour/blow by combined with the humidity in the air in the right way for those brief seconds)

Also, vehicle was in a state of equilibrium, where all the forces were perfectly in balance. I wasn't trying to accelerate, I wasn't going downhill or turning. The power produced by the engine balanced out all the forces against the rolling vehicle perfectly for a 5 second timeframe, indicating that it IS indeed possible.

And that's what we should strive for.

This is similar to what happened on my Orange Test with the Subie. Though I had no scan gauge or other electronics for that, just paper, pen and calculator. And it was a 50 mile test under the most exact conditions possible.

But you and Wendy are sure achieving impressive results, Greg!

You've set another Gadgetman Milestone, doubtless on the way to further gains. It's a rush, to see numbers like these, even for a relatively short time. It builds excitement, and the drive to press on to further accomplishment.

Myself, I would be all about getting the new plugs/wires installed, they should only help. I would be puzzled if that were not the case.

Seeing really high economy numbers like these is a bit like pole-vaulting. That moment when you realize you cleared the bar, higher than ever before!

I tip my hat, sir!

Tracy G

Personally, I'd like to see that number (3.5L/100km) year round on the highway...

So yes, you're right Tracy, I should get my butt in gear and get the new plugs and wires installed.
I've measured the wire resistance, and while it's not Zero, I get 0.1 ohms. close enough!

I've also measured the spark plug resistances. The average is just below 5k Ohms. I'm going to try to balance them between cylinders to try and keep the spark consistant.

Have had those short spurts too when I was getting 45-55mpg and it felt like the truck was going downhill in neutral. This once lasted for about 30 seconds on the longest burst but then the computer kicked in to kill the success. So smooth and the way an engine should run but they designed it instead to burn fuel.
And we are a free people?

Here is a video that puzzled me on this guys success with just rerouting the blow by exhaust from the valve cover to a canister. Sorta like the PCV reroute and reburn theory.