2.9L Reality Check: Highway capable?

[Curious Hound]

I would expect better performance from a stock 2.9l. 4.10 gears and 31" tires should be fine. I'm not sure how the auto transmission should affect it.

As comparison, I drive a 3.0l pushing 35" tires through 4.56 gears. I have a manual transmission and I can downshift at will. It's not a great comparison though. The 3.0 makes power at a much higher rpm. Still, I would expect your rig to outperform mine.

 

[fastpakr]

I would expect better performance from a stock 2.9l. 4.10 gears and 31" tires should be fine. I'm not sure how the auto transmission should affect it.

As comparison, I drive a 3.0l pushing 35" tires through 4.56 gears. I have a manual transmission and I can downshift at will. It's not a great comparison though. The 3.0 makes power at a much higher rpm. Still, I would expect your rig to outperform mine.

A properly running 2.9 would handle that combination just fine. I've put a lot of miles on a Ranger and a Bronco II with that motor and it worked very well.

 

[Uncle Gump]

Uncle Gump,

You are correct, I did forget to list the Hypertech CHiP and how the last one I bought was $12, brand new in box, never used on OCT2020.

WoW...you are correct. It costs less.
• $104, BORLA 2¼" SS turbo muffler, summit racing
• $80, 2¼" SS hi flow cat, summit racing
$139, 2¼" mandrel bent 409 SS tubing 8 piece kit, eBay ($250 from Summit).

$104
+$80
+$140=$324

I'm not gonna argue about this...

I see you edited your post and then just deleted it. Way to go.

 

[eightynine4x4]

Anybody see the HG videos I posted? It’s last post on first page so you might miss it.
From what I can tell from doing a little research, the idle HG looks good but I’m unsure how to interpret all of the variation during acceleration and such.
If I have no HG issues, then what next for looking for OWM power.. just start popping the covers and really inspect some hardware?

 

[ecgreen]

Fun topic! I can only speak for a B2 2.9L

And my answer is....



....



....



Wait for it...


...

HECK NO!!!

 

[RonD]

You are dropping to 0" vacuum under load, that means NO AIR FLOW thru the engine, so 0 power at that time
That can happen when you lug an engine, RPM/power is way too low to push the weight of the vehicle
Maybe try the hill in 2nd instead of 3rd to keep those RPM closer to 2,600, or 3rd instead of OD

Vacuum is what pulls the new air with fuel added into the engine
So either air flow IN is restricted or air flow OUT(exhaust) is restricted

Pull off the air cleaner and have a look, leave it out and leave top off the air cleaner, box

Start engine
Put RPMs at 2,600 and hold it there
Watch the vacuum gauge, should stay steady, if its slowly dropping then exhaust is most likely restricted, reduced AIR OUT

 

[eightynine4x4]

You are dropping to 0" vacuum under load, that means NO AIR FLOW thru the engine, so 0 power at that time
That can happen when you lug an engine, RPM/power is way too low to push the weight of the vehicle
Maybe try the hill in 2nd instead of 3rd to keep those RPM closer to 2,600, or 3rd instead of OD

Vacuum is what pulls the new air with fuel added into the engine
So either air flow IN is restricted or air flow OUT(exhaust) is restricted

Pull off the air cleaner and have a look, leave it out and leave top off the air cleaner, box

Start engine
Put RPMs at 2,600 and hold it there
Watch the vacuum gauge, should stay steady, if its slowly dropping then exhaust is most likely restricted, reduced AIR OUT

To be clear, I wish I had a manual but it’s automatic. I REALLY wish. Not just sorta wish. My 175cc motorcycle also lives on high rpm’s so I’m always downshifting and strategizing and it’s a breeze.
For the 2.9 I guess I could rely on the column shifter but that sounds super cumbersome and clumsy. But I’ve never tried so can’t knock it.

Its raining hard so couldn’t undo the air filter but I decided to park and hold the rpm’s at 2600 for a full minute to see what the HG did. It stayed exactly the same the whole time.

I already put a new air filter in last summer and reshreshed some of the screws for the box since it wasn’t really sealed. I also gahd already cleaned the throttle bottle thoroughly inside and also checked the valve or whatever that was.

However, one project I have not yet addressed is that one of the two air tubes from front grill is totally gone. The passenger side tube is fine but the driver side is gone.. there’s supposed be to a tube that takes a path from under air box and over the driver grill. So what’s left is an air input next to the fan. Not the cleanest air. The other one properly goes to grill. So that means 1/2 of the air is not ideal. But given the fact that I have no grill or no fenders on right now, I think a whole lot of decently fresh air is getting into both air inputs, especially on a highway with tons of head wind.
I would love to be wrong about this and find that when I hook up the second air tube that my truck can hit 88mph and disappear…

 

[RonD]

Exhaust is clear

Recheck your spark timing after engine is warmed up and SPOUT unplugged, try 12deg BTDC

 

[Uncle Gump]

I would recheck vacuum while engine is under load... not sitting in park on a free rev

 

[eightynine4x4]

Exhaust is clear

Recheck your spark timing after engine is warmed up and SPOUT unplugged, try 12deg BTDC

Ok I’ll give it a look. I just did this in the fall, and it made a very huge improvement! It’s also how I learned that the distributor cap was left so loose by previous owner that it was literally rotating gradually and obviously altering performance behind the scenes so to speak. I made sure to thoroughly secure it when I was done with the timing and the engine seems to perform the same now as it did then, which was a major upgrade from prior.

Im also wondering if maybe the distributor itself needs to be replaced. I put in a new cap when doing the timing, but isn’t the whole distributor in need of replacement sometimes? I haven’t learned much about that part yet.

I might opt for a K&N filter despite it being debatable snake oil. Reason is I just don’t have a lot of faith if the state of my OEM air input pathways. It’s kind of beat up and like i said a tube is missing. With a K&N sitting on top I can at least in good conscience eliminate air input as an issue. If anyone wants to point me to one that bolts right up the the 2.9 throttle body I’m all ears.

I get some serious lumpiness once in a while too. Feels like I’m carrying the weight of a dead cylinder, but i've never dealt with that so can't speak from experience. But it feels like the engine is slinging extra weight around and around, shaking everything. Doesn’t happen often and it’s only ever during warmup. A burst or two of throttle usually clears it. Here is a video of exactly this from earlier today. If you happen to listen in headphones or speakers you can really feel the lumpiness.

I really want to tie this issue with the highway power issue somehow. My gut feeling is i have to open up the engine and take a look. But this miss doesn't happen at all after warmup and especially not at higher speeds.

In this video it took a third burst of throttle, up to 3.5k, to finally clear it.

Dropbox

www.dropbox.com

I would recheck vacuum while engine is under load... not sitting in park on a free rev

There is a second video in that same post, it shows HG under various loads up and down a couple hills.

 

[Uncle Gump]

Sure looks like you go to near zero vacuum under load... to me it appears to have a restricted exhaust.

 

[eightynine4x4]

Here’s a vid of me holding approx 2600 rpm for a minute and HG staying above 20 the whole time.

Dropbox

www.dropbox.com

Im not sure I have a restricted exhaust because the HG doesn’t drop at all when holding RPMs even after a full minute. I’m also not sure that dropping close to zero during acceleration is bad.

Here’s just an example guide and most say the same thing..

“”… vacuum is highest at idle and drops off to zero the closer you get to wide open throttle (WOT). With the engine running, take your first reading. Raise the RPM to about 2000 or 2500 and watch the gauge. If you have an exhaust restriction, you’ll begin to notice that vacuum will slowly drop off over time, and it might be harder to maintain the RPM. If the vacuum remains the same, then you don’t have a restriction and you can move on to other tests””

 

[Uncle Gump]

Well... the first video where you were driving you were holding slightly above 2k and you had nearly 0 vacuum. That is what I based my comment on.

I've always tested for restricted exhaust dynamically... not with the vehicle in park. It seems to me you have a problem while driving... not while sitting in park.

 

[eightynine4x4]

Well... the first video where you were driving you were holding slightly above 2k and you had nearly 0 vacuum. That is what I based my comment on.

I've always tested for restricted exhaust dynamically... not with the vehicle in park. It seems to me you have a problem while driving... not while sitting in park.

Im certainly not opposed to the idea that there’s a restriction in the exhaust! Only trying to correctly interpret the readings. Yes I’m also concerned that it reaches zero, just don’t know enough about how this works. If anything, I guess maybe the fact that it’s a sustained zero is what the real problem is.. maybe reaching zero momentarily after acceleration is fine but hanging out at zero while under load, which my truck does, is a sign of something wrong with flow. Just guessing here.

On a side note and to review my output…my cat is new, muffler is new, pipes after cat are new, right manifold is new. Y pipe and left manifold are old. I did a leak test and found no leaks other than a small one at entry to cat, but that doesn’t mean the left manifold or left part of Y pipe isn’t blocked. It could be blocked and the leak test is null and void.

I think the smarter thing to try first is installing a new and simpler air input situation and just seeing if that changes anything and even if no change then I can still rule out the air intake. I’d live to just pop a $75 K&N filter directly onto the throttle body and not spend $300 on some tubing accessory between the two, so that’s what I’ll look for.

 

[fastpakr]

If you're getting zero vacuum at WOT, I don't see how the air intake side of the equation could possibly be a restriction.