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Quadrasteer 8.1L Suburban tow rig

2003 Suburban 2500 Quadrasteer camper towing 8.1L 6.0L swap 4L80-E

Blue85

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12 mpg is in the normal zone towing or not.
When I had it running a year ago it was about 13.5 commuting. For 75 miles empty last week it was more like 14. The real question is what it will see with a camper. Needs some MAF tuning, too.
 

ZooMad75

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When I had it running a year ago it was about 13.5 commuting. For 75 miles empty last week it was more like 14. The real question is what it will see with a camper. Needs some MAF tuning, too.
I've seen 13's to 14's on a couple of tanks so far on mine but it required so much discipline to drive at or below 65 mph and not stomp on the loud pedal it wasn't fun. If I reasonably restrain my right foot I'm typically getting low 12's for mpg. It can be 8-9 if I'm driving it like a pissed off teenager though.

I've got a serious aero disadvantage as well as being pretty heavy at 6,500 pounds.

With the camper I wouldn't be surprised by single digit mileage at all.
 

Blue85

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In my big trip thread (https://ck5.com/forums/threads/how-warm-should-my-engine-get.330868/page-3), I got 9.5MPG average over a few thousand miles with the LQ4. I never really got much over 15.5 without really careful use. Something about deep gears and tiny tires in a heavy SUV prevents good mileage with any gasser. Maybe I'm an optimist, but it seems like a giant, non-down-shifting engine can get better mileage in some towing situations than a medium-sized gear-hunter. Even if that's a wash, the trip will be more enjoyable. (Hence this thread :D)
 

ZooMad75

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In my big trip thread (https://ck5.com/forums/threads/how-warm-should-my-engine-get.330868/page-3), I got 9.5MPG average over a few thousand miles with the LQ4. I never really got much over 15.5 without really careful use. Something about deep gears and tiny tires in a heavy SUV prevents good mileage with any gasser. Maybe I'm an optimist, but it seems like a giant, non-down-shifting engine can get better mileage in some towing situations than a medium-sized gear-hunter. Even if that's a wash, the trip will be more enjoyable. (Hence this thread :D)

I can tell you without a doubt that is exactly what you will find. Granted I had the added variable from going from the slushbox to the manual, but I'm getting comparable mileage between the 8.1 to the 5.3 on my normal running around and highway runs. Again, that is driving within reason and not trying to haul ass all the time.

The main difference is what you noted, the 5.3 couldn't maintain speed all the time in OD so the trans did a lot of downshifting. Around here that could be going uphill on a mountain grade or even into a heavy headwind and the trans would be dumping into 3rd or as far as 2nd. That would be to maintain highway speed. Now in the same terrain, I can pretty much leave the trans in 5th and lean on it if I need to speed up. Only on steeper grades if I let the momentum drop do I actually need to drop a gear to maintain speed.

It's much more enjoyable to drive for sure.
 

imiceman44

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Towing with a 5.3, or even 6.0, sucks.

Martin
Yeah but until you try bigger you don't realize.
I always towed with my 350 in my crew cab, but then I got my turbo diesel truck and realized what I had been missing.
Then I got a freightliner with a 12 liter engine and I was pulling 80k lbs and I was impressed until I got one with a 15 liter.
It's all relative
 

82355

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Not really. My 1988 V10 Suburban with an LO5 towed better than my 2005 K1500 Suburban with a 5.3.

Martin
 

ZooMad75

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Not really. My 1988 V10 Suburban with an LO5 towed better than my 2005 K1500 Suburban with a 5.3.

Martin
Small blocks make better torque at lower rpm than a 5.3 does. Stock vs stock that is.

But more displacement is always better.
 

Blue85

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I don't know that 6500 is all that heavy. I think the aero is a bigger factor. This Sub is like 6100 empty. Pulling a camper you can feel the aero drag even going downhill. I'm sure my K5 is over 6500 lbs in expedition mode and the MPG seems more effected by the roof rack than all the cargo.

As for an 88 towing better than a GMT830, you have to discuss the gears and tires (transmissions would be equivalent).

Plus, a 6.0 has the same stroke as a 5.3 and has pretty much the same power band.
 

ZooMad75

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Aero is a factor in my case for sure. But I can say prior to the camper when mine was loaded for a weeklong trip the 5.3 still struggled just as much on the mountain passes as it did later with the camper. Speeds going up a twisting mountain pass are usually around 40 and adding in steepness and elevation between 9,000 to 11,000 feet, the truck just isn't moving fast enough to have aero effect it as much.

The 5.3, 4.10 gears and 35" tires had an impact on how it did. I could have geared deeper with the tires to help the 5.3 stay up in torque curve better. Or put 33" tires on it, but who does that?
 

folkenheath

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I agree with that, I've seen larger mileage losses from a roof rack with bikes on it than a boat trailer that weighed significantly more than a couple bikes. The wind resistance at speed is a large factor.

Of course that is mostly flat driving, in the mountains the weight would mean more than just increased rolling resistance once up to speed.

In the equations the speed is squared for wind resistance, and the mass is just linear.
 

Blue85

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I may have gotten the CASE learn to work last night. There are many reports on the web of it not working and it's a problem of incomplete instructions and a poor user interface. There is no "start" button and no feedback anything is happening. However, using these modified instructions the fuel cutoff is at about 4100RPM, so something is different. The key is to not click OK until afterward.

CASE Learn: To use the CASE learn function please follow these steps:
1.Ensure the engine is at normal operating temperature (ECT > 170F).
2.Put the vehicle into park (auto) or neutral (manual).
3.Turn off all accessories and A/C.
4.Turn the vehicle off.
5.Apply the parking brake.
6.Press the brake pedal. Keep the brake pedal depressed during the entire procedure. REQUIRED for successful test completion
* Manuals: Use right foot to depress right-hand side of the brake pedal, so when you release the clutch after starting the engine, your left foot can take over on the left side of the brake pedal without releasing the brake pedal.
7.Start the vehicle and let it idle.
8.Press Begin.
* There is not a Begin button. Ignore this.
* Click the Crank Relearn button, do not click okay yet.
* I waited only a couple of seconds between clicking Crank Relearn and beginning to rev the engine
9.Gradually rev the vehicle to fuel cutoff (around 4000-5000 RPM's) over a period of about 4 seconds. When fuel cuts out, immediately release the throttle.
10.Allow the engine to come back to an idle.
* Now press the Okay button
11.Turn the ignition off for at least 15 seconds. This step is required for the VCM to store the newly learned configuration.
 

Blue85

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This makes me wonder why the limiter is so high in P/N to begin with. Seems like it should be just high enough to do CASE learn and no more.
 

Chevy305

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On my '12 Silverado the stock fuel cutoff in P/N is about 3500 rpm. I raised it to 6k because racecar.
 

Blue85

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On my '12 Silverado the stock fuel cutoff in P/N is about 3500 rpm. I raised it to 6k because racecar.
Yeah, makes sense for low stock and high modified (induce fear in EcoBoost drivers?)

I switched to 5W-40 and now hot idle pressure is around 14 @ about 570RPM. Was initially bummed to drop "new" oil so soon, then I realized it had been 900 miles that week. Will probably try bumping idle a bit next flash, but idle is way smoother than my 5.3 engines (remember I'm unable to flash through OBD2 port like a normal car for some reason.)

Have been driving it a bit for fun and no more fault codes. Really smooth passing power with no downshift. Charged the A/C. Nice driving truck.
 
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