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So I was detailing the Enclave the other night in the garage and slid underneath the Enclave to see what was under there. These are a couple things that caught my attention.

Not a true dual exhaust system: The exhaust system on this car is very complex, probably due to current emission standard requirements. The horizonatally opposed V6 has one bank of exhaust that comes out in the front of the engine and one in the back. Each bank appears to have a small catalytic converter before the two systems merge right before a large secondary catalytic converter. After the 2nd catalytic converter, the one pipe goes along the passenger side of the drive axel (we have an AWD) and then into a main muffler that is under the rear passenger seat. After this muffler, the exhaust splits into two separate pipes and then there are small mufflers right before the two tail pipes. The very weird part of the exhaust system is that the rear bank exhaust does a complete 360 degree turn before it enters the main catalytic converter. I'm speculating that it needs this extra length for some good reason but on the surface it seems highly inefficient (possible reasons: Length of the rear pipe needs to be the same as the front pipe <which has farther to travel> or something to do with emissions that requires more distance between the small initial catalytic converter and the main catalytic converter.)

The gas tank is very long and shallow: The gas tank runs under the driver's side of the Enclave (exhaust is on the other side) and it is a very long and shallow tank. It is about two feet wide and 5-6 feet long and runs from under the driver's seat back to rear wheel well. There is a nice heavy duty metal bar that hangs about 2 inches below the bottom of the tank along the driver's side edge to protect the tank should you bottom out the Enclave. The exhaust system is the sacrificial lamb on the other side and hangs down at about the same level as this sacrificial bar. I was surprised the tank was located on the driver's side and you would expect it to either be centered on the vehicle or located on the passenger's side for better weight balance. Of course this isn't a sports car so that isn't as important in this vehicle but I'd be curious what the left/right weight balance of this vehicle would be on a full tank of gas. The battery/exhaust/brake lines are on the passenger's side so that helps counter the weight imbalance somewhat. I'm wondering how the fuel level measurement is done on a tank that is so shallow like this. It makes me wonder how accurate the guage can be with such a shallow tank. I would think that the gas would be sloshing around so much in such a shallow tank that the level could be all over the place and difficult to measure. I'm sure that was a fun engineering challenge for someone.
 

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"It makes me wonder how accurate the guage can be with such a shallow tank. I would think that the gas would be sloshing around so much in such a shallow tank that the level could be all over the place and difficult to measure."

Interesting observations. Indeed, my fuel gauge is not accurate and does move all around. I can start out at 3/4 of a tank and in 2 minutes it is reading less than 1/2, go up a hill, and I am at a full tank. Going in to the shop someday for this if I ever get any time from work!
 

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I had mine on the rack Saturday doing the oil change and throttle body cleaning. It is very interesting under there for sure. Changing the oil filter is a pain, but otherwise not bad. I saw that curve on the pipe coming out of the cylinder head closest to the firewall.

They had to bend it to make it fit properly, since the O2 sensors measure all the exhaust coming out before and after the catalytic converters.

That 60 degree V6 engine is quite unique. I hope it lasts a good long time. I have the FWD, so no rear differential.

I ordered my shop manuals from HELM, INC last night. I think they are a good value at $135.00 plus shipping, handling and tax. $167.00 overall.

You are right about the fuel gauge. Park on a hill and things really register crazily. I'll see how things work out as I travel east next week.

Thanks
 

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Equal length headers are very common. It is done on purpose.....to make the torque curve the same for all six cylinders.
 

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True dual Exhausts exist mainly on trucks and some high end Sport Cars like the Vette. Way back in 1968 my '68 Fire Bird 350 HO had a single pipe ran back to the muffler and
had a "side way mounted Muffler" that split into dual exhaust pipes. Same on my '93 Trans Am , my son's '94 Z28 , and my Wife's
2000 Grand Am GT with Ram air. Even the chevy SS's had this in the 80's. I think it is a matter of space available somewhat and cost.
 

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VQinside said:
I'm wondering how the fuel level measurement is done on a tank that is so shallow like this. It makes me wonder how accurate the gauge can be with such a shallow tank. I would think that the gas would be sloshing around so much in such a shallow tank that the level could be all over the place and difficult to measure.
bsox said:
... my fuel gauge is not accurate and does move all around. I can start out at 3/4 of a tank and in 2 minutes it is reading less than 1/2, go up a hill, and I am at a full tank. Going in to the shop someday for this if I ever get any time from work!
GSEREP1 said:
You are right about the fuel gauge. Park on a hill and things really register crazily.
You guys are correct. Have you read my testimonial?
(http://www.enclaveforum.net/index.php?topic=2730.msg38207#msg38207).

Fuel pumps used to drink from the bottom of the tank, sometimes even from a sump, I believe. Any sign of such an arrangement under the lambda?
 

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The exhaust runners look weird because this is how the exhaust is 'tuned' for efficiency and sound. The lengths of the pipes are determined so that the exhaust pulses can merge and not hit junctions or the muffler at the same time. This also allows for less backpressure in the engine (more horsepower at higher rpm's). It is amazing how the exhaust note can change with just a very small difference in pipe length.
 
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