Author Topic: 6G75 Variable Intake - The Piston Eater  (Read 8694 times)

Kevin_Slark

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6G75 Variable Intake - The Piston Eater
« on: August 09, 2017, 01:46:55 PM »
Okay, 6G75 Montero owners, I'm approaching 120k on my '03 in the coming months and replacing the lower plenum (MN135871) is part of the recommended service. I don't want to pay $600+ for a new one. I also know they eat pistons when they fail. Like the rest of you, I'm thrifty when it comes to these things and I was considering whether it could be rebuilt.

Guess what - it seems some enterprising Russian has made it happen. Check out these links:
https://www.drive2.com/l/452470751258214980/
https://www.drive2.com/l/472962624342983508/

It seems he got replacement bushings and replaced the original screws with stouter parts. I'm unsure if the butterflies themselves are new or just cleaned well. Of course, the link to the ad on the second link is dead.

The Australians discuss good mechanics being able to rebuild them with new bushings. I'm not familiar with where to acquire those sorts of bushings in the US of A, I'm sure someone with more knowledge has a source. My Googles have revealed nothing relevant.

I also found this on the Wire, about appealing to MMUSA's liability side on this stupid part for DOHC 6G74's:
http://4x4wire.com/forums/ubbthreads.php/topics/367272.html

What do you all think?

Shovel

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Re: 6G75 Variable Intake - The Piston Eater
« Reply #1 on: August 09, 2017, 03:17:42 PM »
Disclaimer:   I don't have one of these engines & don't have the first-hand experience with this,  so take what I'm about to say as nothing more than conversation.

Since the 6G75 Monteros still use an aluminum manifold and those butterflies to try to flatten the torque curve a bit,  would there be value in just throwing the whole thing in the recycle bin and fitting a plastic intake manifold from an Endeavor or Eclipse? 

Or, simply removing the butterflies and running "open" ?

For reference:  In 1999 Ford updated their 3.8L V6 as equipped for Mustang to include a dual plane intake manifold,  with provisions for runner control but none installed.    This engine produced 190 horsepower at 5250 and 220lb torque at 2750.   In 2001 the intake manifold runner control was implemented (no other meaningful changes) and output increased to 193 horsepower at 5500 and 225lb at 2800rpm .    It's a nonzero amount but it's not a big amount and we can expect similar here on a Montero. 

Crumb

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Re: 6G75 Variable Intake - The Piston Eater
« Reply #2 on: August 09, 2017, 04:47:35 PM »
 Charlie was talking about making a better manifold to replace it, maybe he'll chime in.

RyanY

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Re: 6G75 Variable Intake - The Piston Eater
« Reply #3 on: August 09, 2017, 07:47:44 PM »
For reference:  In 1999 Ford updated their 3.8L V6 as equipped for Mustang to include a dual plane intake manifold,  with provisions for runner control but none installed.    This engine produced 190 horsepower at 5250 and 220lb torque at 2750.   In 2001 the intake manifold runner control was implemented (no other meaningful changes) and output increased to 193 horsepower at 5500 and 225lb at 2800rpm ./quote]

The numbers you've quoted are peak HP & torque numbers, which are not what the variable intake system is designed to enhance and are fairly irrelevant to this discussion and the function of the butterfly system. The long runners increase the torque at lower RPMs - an increase that will only be evident if you can compare the ENTIRE torque curves of engines with and without the variable intake functioning. The 3.8 V6 mentioned above may have only picked up 3 peak hp and 5 peak ft/lb of torque, but I'm certain that there were far more significant gains throughout the powerband that weren't reflected in the peak numbers.

If you follow any dyno competitions, it's common to score a vehicle's power and torque outputs by calculating the area under the curve rather than a peak value, as it's more relevant in real-world driving.
 

RyanY

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Re: 6G75 Variable Intake - The Piston Eater
« Reply #4 on: August 09, 2017, 07:55:48 PM »
It seems he got replacement bushings and replaced the original screws with stouter parts. I'm unsure if the butterflies themselves are new or just cleaned well.

Johnny B from Peoria had new bushings made for his 6G74 manifold and still has the plans for them - I don't believe tht he ever figured out a way to seal the front end of the butterfly shaft though.

The butterfly valve screws aren't the problem, they are the symptom - if the butterfly shaft is properly supported by it's bushings, it won't vibrate and the screws won't work themselves loose. Up grading the screws is unnecessary if the bushing issue is properly addressed.

For what it's worth, I replaced the intake plenum on my 95 SR 11 years and 115K miles ago with a new Mitsubishi part, and the butterfly shaft is still rock solid with no side to side play at all. 

Shovel

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Re: 6G75 Variable Intake - The Piston Eater
« Reply #5 on: August 09, 2017, 08:02:13 PM »
In the absence of any credible curves to compare, I used the numbers actually available.   I'm certain they do something or companies wouldn't spend the non trivial money on putting them in there, I suspect larger flowing single plane intake becomes better yet.    Using the same mustang example, swapping a non-variable manifold from a Windstar increases power at all rpms simply owing to it's much larger cross section on all runners.

ChargerX3

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Re: 6G75 Variable Intake - The Piston Eater
« Reply #6 on: August 11, 2017, 10:21:14 PM »
If anyone is offering to get rid of their 75 variable intake then I have a very deserving home for it. :)

bacca

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Re: 6G75 Variable Intake - The Piston Eater
« Reply #7 on: August 13, 2017, 07:02:21 AM »
I went to a local Junk yard. The goal was to pull the plenum from an 03 TAE that just showed up. As I arrived the weather got really bad. Dark skies...etc. So I rushed in there found the Montero and pulled the plenum in about 15 mins. I then found a Kia Sorrento with the Sigma motor. Popped the hood and someone had pulled the Plenum and left it sitting on top for me.

Then the skies opened up and it became a down poor. So I snapped some pics and had to bolt out of there. I attached the quick pics I took to this post.

The Plenum looks like a Gen 2's. It appears that it would bolt but the runner lengths are different and the height is less than that of the Montero Plenum. So I am not sure it will clear the valve covers. It will be close. It does have the butterfly valves but it does not look like you can service those. Just like the Montero.

I may go back today or tomorrow and take it over to the Gen 3 I just pulled the plenum on and see how it would fit.

Looks like the lower section is only $200ish if the Kia manifold works:
http://www.ebay.com/itm/Genuine-VALVE-SUB-ASSEMBLY-INDICATOR-CONTROL-for-Kia-Sorento-OEM-2922139800-/122054718159

I now have two broken plenums and the new one I just pulled feels solid. So I will be putting that on, sending one to Kevin to see if he can find a way to make a repair kit.

ChargerX3

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Re: 6G75 Variable Intake - The Piston Eater
« Reply #8 on: August 13, 2017, 09:12:34 AM »
Oh the want for that intake is so strong.  :'(

JohnnyBfromPeoria

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Re: 6G75 Variable Intake - The Piston Eater
« Reply #9 on: August 16, 2017, 06:50:26 PM »
At one time I had the schematic to make new bushings for my '95's plenum, but I can't find it these days, and all remaining hope may be lost for the time being since I just moved.

The guy that made mine passed away, but he had a chunk of bronze-aluminum alloy left over from the last run of parts he was contracted to build for a space shuttle that my brother (who made the measurements, drew the schematic and put the plenum together for me) and he used to make the bushings themselves. And, as stated above, the end of the shaft leaks to atmosphere so my whole system is currently unplugged electrically with silicone crudely dumped on the end of the assembly to try to plug the leak so my NOX readings weren't so high, causing me to fail an emissions test. I have a spare plenum but haven't taken the time to take it apart to see how the end of the shaft should be sealed correctly.

Putting in new bushings is one of the keys. Setting the screws that hold the butterfly vales to the shaft is important, too. Here, my brother found a good-fitting screwdriver to keep from stripping the heads and used loc-tite on the screws. If the screws protrude from the other side of the shaft you can stake them, but I don't think they do. Thirdly, the linkage on the outside has some bushings that wear out, too. These can rattle and shake the shaft as well. My spare plenum is tight; my original one is not and it makes a racket.

The bushings themselves can be measured with a micrometer, but you'd do best to find ones that fit well or your new ones will be loose, too. Best would be to mic the actual openings in the plenum where the bushings sit. Then mic the shaft and you'll have what it takes to make new ones. There are companies online that will make them to order out of several materials, but I can't suggest anything. The plenum is aluminum and the shaft is steel so use your best judgment.

I tend to side with RyanY on the "under the curve" totality of the design. Since that's what was on there stock, I would like to keep it that way. At least as long as it doesn't affect how my future supercharger works (kidding).

John B.
AZ Crew/East Sider/Former 14th St Crew
95 SR, 35x12.5-15 on 8" steelies, 2" BL, stuff cut off, stuff welded on, lights, sound, front ARB pending
87 Raider, There's a turbo 2.6 under its hood, really
83 "Dodge" Power Ram 50, a bit lifted, way slow and gets more comments from random people than the other two put together
'95 Montero SR. Pretty much stock, Trail Gear Sliders, ADD skid plates, Stereo by Shovel, Timing maintenance by Pa_Jero

bugshield

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Re: 6G75 Variable Intake - The Piston Eater
« Reply #10 on: August 30, 2017, 10:09:06 AM »
While I had my intake plenum off for a set of spark plugs, I removed/reinstalled all the tuning-valve screws with red Locktite and hit the protruding threads with a chisel after tightening them down - that will hopefully prevent dropping a screw down the intake.

I also removed the front bushing behind the actuator and, while there does seem to be wear to the shoulder of the bushing (165k miles), I think that bushing can be well supported and sealed by replacing the o-ring with a new and better-fitting one.  The o-ring I removed was very brittle and did nothing to provide a vacuum seal or support the bushing.  Honestly, I'm not sure the bushing was designed to carry the load directly rather than via the o-ring as the engagement surface is very small.

I hope this information helps someone else.

Kevin_Slark

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Re: 6G75 Variable Intake - The Piston Eater
« Reply #11 on: October 09, 2017, 02:41:45 PM »
In the past two months, I have tracked down the man in Novokuznetsk, Kemovo Oblast, Russia that makes intake bushings for the 6G75, 6G74, and a whole range of Hyundai GU motors. Via whatsapp and Google Translate, I've made a new friend.

I purchased a set of 6G75 bushings from him for $85, here they are in all their glory!


No, I don't know what they're made of, I asked but Lissa911 wouldn't tell me. I've done it narrowed down to a handful of Russian-developed polymers, but they have excellent reviews all across drive2.ru, so I don't care at this point.

Later this week, I'm starting the install and will fully document it in English. Admins, please let me know how to submit this to the wiki. The screws and lock nuts I've ordered from McMaster-Carr should be here tomorrow, that's all I lack in order to make some magic happen.

Hit me up if anyone has questions.

I asked Lissa if he would prefer to deal with one person in the United States or take orders from whomever, he told me that foreign payments from a single person were treated far less suspiciously in his part of the world.

The current plan is to offer up these kits at $90 ($85 my cost, $5 to ship them to you from me in Mississippi), plus a "complete kit" with new stainless butterfly fasteners for a few dollars more.

offthepath

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Re: 6G75 Variable Intake - The Piston Eater
« Reply #12 on: November 14, 2017, 07:53:42 PM »
This post took from from Expo over here.  Really good work!!  I want a kit, let me know the best way to get you the $$$.

Ben

ChargerX3

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Re: 6G75 Variable Intake - The Piston Eater
« Reply #13 on: November 14, 2017, 09:58:47 PM »
These would be ideal to 3d print from home. Might ask for his drawings.

Kevin_Slark

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Re: 6G75 Variable Intake - The Piston Eater
« Reply #14 on: November 15, 2017, 12:39:27 PM »
ChargerX3, I tried that, but Lisin is protective of his IP in these things. He's a nice guy and has a family, ever bit of scratch comes in handy in Russia.

Ordering info is coming soon!