diminished power

[1der]

Jack K -
What configuration do you have?
Year, mileage, gear ratio, tire size, 4x4, van weight?

Our stock v10 would experience a drop in power at elevation but it still felt plenty strong. 4x4, 3.73 gears w 31’s (265’s).

[carringb]

Originally Posted by Jack K

The disconcerting aspect is a very sluggish response when, say, I turn onto a curvy mountain road out of a campground and need to accelerate in order to get up to traffic speed. Punch on the skinny pedal, wide open throttle, nothing happens for a bit, then a s-l-o-w acceleration. The revs don't happen. I just didn't expect that kind of performance from a V10. Our passenger car doesn't exhibit that kind of large change in response at altitude, so I'm wondering why does the van. At sea level, it's great, got the 5-Star perf tune, a noticeable improvement over stock. Thanks for your knowledge.

OK I didn't realize you had a V10. It can be expected from the 5.4L, but the V10 should have power to spare even at 10,000 ft unless you're towing a heavy trailer. What's your loaded weight and gear ratio?

[Jack K]

2013 EB E350, odometer 64,610, 4.10, 4X4 w/ Atlas II, 33" tires (285's), weight 10,060 gross (6120 rear, 3920 front) fully loaded with 2 adults + gear add an additional ~500 lbs.

[carringb]

Originally Posted by Jack K

2013 EB E350, odometer 64,610, 4.10, 4X4 w/ Atlas II, 33" tires (285's), weight 10,060 gross (6120 rear, 3920 front) fully loaded with 2 adults + gear add an additional ~500 lbs.

In your case, it's the gears.

Your effective gear ratio is about the same as 3.55 gears with stock tires. Ford didn't offer the V10 with 3.55 gears because its puts operating RPMs too low to make target horsepower. And then your loaded weight just makes it worse.

To restore your gearing to factory 4.10 equivalent, you should be running 4.56 gears. It will make all the difference in the world.

[Jack K]

Originally Posted by carringb

In your case, it's the gears.

Your effective gear ratio is about the same as 3.55 gears with stock tires. Ford didn't offer the V10 with 3.55 gears because its puts operating RPMs too low to make target horsepower. And then your loaded weight just makes it worse.

To restore your gearing to factory 4.10 equivalent, you should be running 4.56 gears. It will make all the difference in the world.

Very good, thanks carringb! I appreciate having a fact-based explanation.

[Jack K]

There is an additional thought. The current tires are nearing their useful life, and I'm considering replacing them with 35" ones. What would be an appropriate gearing for that configuration?

[carringb]

To maintain 4.10 equivalency with 35" tires, you would need 4.88 gears.

On that note, have you ever checked your speedometer now? I'm wondering if it was ever programmed for the taller tires with 4.10 gears? Or does it reads slow? It its correct now, you might have to adjust it again once its properly geared.

BTW - I use https://www.miata.net/garage/tirecalc.html for calc'ing tire ratios. Super useful for knowing the affects of a tire change, then you just use the resulting percentage to calculate the equivalent or proper gear ratios. It's been around for decades, therefore flash is required, so I launch it in Chrome.

[1der]

carringb is da man and has vast experience with his v10. So, I give lots of consideration to his advice.

That being a fact, and for 13 years w our V10 with the same effective gear ratio of 3.55, (3.73 w 31’s vs your 4.10 w 33’s), I think something does not sound right. With our v10 (all stock, no tunes similar mileage to you) which had the four speed (so even less pick up), I never felt like I wanted to change gear ratios even at 10,000 ft or towing a 6,000 lb boat/trailer. I have driven v10’s w 4.10’s w 33’s at sea level with the 5 spd trans and it felt like the engine pulled effortlessly with the extra gear.

What elevation was this campground? Was the trans lever pulled down to first gear? Maybe something in the 5 star tune that was creating a strange condition? Just me - I would first investigate some other possible causes before going the gear change route to eliminate some other engine/trans control, draggy brake, issue.

Gear changing can be a very $lippery $lope. $2500++ for changing two diffs. Do you have lockers? One locker up front will add another $1k.+.

[carringb]

Ray brings up a good point about the transmission selector. A lot of people don't realize that the numbers on the shifter are fully manual. On other other words, if you pull the shifter into "3", it doesn't limit the range to the lower 3 gears like nearly every car. It actually holds it 3rd gear. Even launching from a stop. Ditto "2". If you're starting on a steep grade, leave it "D" or drop it "1".

Might not hurt to drive to find another SMB member member, and try test driving their van, and get a better baseline on what yours should feel like.

BTW - I have 4.56 gears in my van, and 32" tires. That gearing is a little short for an empty van, but works well for me because most of my trips are towing heavy.

[arctictraveller]

The OP posed his question based on a 2001 5.4 which is a totally different animal than the V10. My 2001 5.4, 410 gears, 8300lb van suffers at moderate altitudes. If I don't keep it near the top of the rev scale, I end up downshifting often, and the higher the altitude, the worse it gets. Around 7 to 8k feet, I feel like I should get out and push on steep grades, so what he's experiencing may be normal. Adding a storage box up top certainly hasn't helped either. The mighty 5.4 is a great, low maintance, long lived motor but it's no powerhouse under the best of conditions. Never the less, if this is a new development, there may be an issue developing.