Sometimes, parts work.

I was ready to sell our 2000 Grand Cherokee and put my wife in something more modern. But I couldn't come up with the justification for spending $40k to replace a nearly perfect low mileage original owner vehicle that she loves. The best I could do would be to get something she liked as much. So I decided to put a bit of time and money into it to fix the little things that were screwed up - bad taillight circuit board, broken solder joint in the turn flasher, etc.

She also wanted some more power out of the 4.7. I looked around and found an old dyno test from Four Wheeler where a flash and intake had made a significant difference. What the heck, it's worth a try.

Purple stock, blue Airaid intake plus TB spacer, red is intake plus chip.

The intake makes awesome growly noises when you get on it. Janel loves the roar. Maybe a little too much, I think she's been terrorizing other commuters.

But the real surprise was the tune. It's a Superchips Flashpak and I wish ours were that easy to install. It made the advertised big chunk of torque. What I didn't expect was the changes in how the trans works. It's a whole lot smoother. I think what's happening is that it used to hang on to OD as long as possible, until it had to drop 2-3 gears to get anything done. Now, I think it's dropping out of OD more easily so it can put down a little more torque but not ALL the torque. And, of course, it's got more to share. Climbing passes in the mountains is a lot smoother and quieter. Fuel economy doesn't seem to be touched, although we feed it 87 octane now instead of 85.

Color me seriously impressed. If you've got one of these, get yourself the tune. At just over $300, it makes a real difference to the way the vehicle drives. I have no association and I paid normal street price through normal vendors to get these parts - but I can't think of the last time I've come across such a good piece of work on the aftermarket, and I had to share.

That whole era of Jeeps has mediocre tuning at best from the factory (both for the engine and the trans).  Good tuning can definitely make a big improvement.  Heck, with some crafty tuning I managed a solid 10% or more gain over stock highway mpg even though I've got a bigger cam and other potentially mpg-robbing performance bits. 

Man, that's a bucket load of torque right where you typically use it.  That really had to make the Jeep more fun to drive.

This is like when someone asks if they should get the Little Enchilada for their MSM.  My answer is now no.  They should go straight for the Big Enchilada.  Makes you wonder why manufacturers leave so much unused potential on the table.

Where do you get 85 octane? The lowest I've seen since like 1986 is 87.

Every gas station in Colorado, to start! Octane availability and fuel quality generally gets worse when you cross the Rockies. The best we can get here is 91.

Oh, the elevation reduces the need for octane by "lowering" compression doesn't it?

GCrites80s said:

Oh, the elevation reduces the need for octane by "lowering" compression doesn't it?

In an NA engine, yes.  In a boosted engine, less so.  Which makes the lower octane choices in high altitude areas kinda concerning. 

You see the same thing in California and most of the western states IIRC. The local claim is that it's due to altitude, but that doesn't explain the lower states that do the same or what it does to turbocharged vehicles.

States might have to re-evaluate that considering that car companies have decided to turbo everything.

Yeah, the states will be the ones who have to change.  

We just ran 15 hours at Laguna Seca with a turbocharged 13:1 engine on 91 octane. It can be done.

I wanna say the Prius i was driving today has 13:1 compression and i WOT it all over the place on 87 octane. Points in advance to whoever knows why that works.

As to the OP, that was the era of the 'death tune', which while not exactly referring to the 4.7 engine does refer to Chrysler's strategy of hitting emissions targets by seriously detuning its engines. It's kinda like VW 'dieselgate' except they did the 'right' thing. 

My dad's 01 Ram needs a tune pretty bad. It is STARK contrast driving the same engines in Dodges from ~94-95 and then in ~98-01s. Same engine, same hp/tq rating, totally different drivability and satisfaction levels.

In reply to Vigo :

I seem to remember reading one of the advantages of direct injection is how it cools the intake charge and helps with higher compression. Plus, it's harder for the incoming mixture to pre-ignite when fuel isn't injected until the last possible moment.

My ex- has a Grand Cherokee, although I don't remember what year it is or if it has a 4.7 V8.  Still, I forwarded the OP to her, although as she tends to research the crap out of her cars, she probably already knows about it.

In reply to Vigo :

Something to do with the Atkinson Cycle?

Something to do with the Atkinson Cycle?

Yes, the late intake valve closing reduces the 'actual/dynamic' compression ratio to something much lower than the 13:1 static number would have you believe.  

I seem to remember reading one of the advantages of direct injection is how it cools the intake charge and helps with higher compression. Plus, it's harder for the incoming mixture to pre-ignite when fuel isn't injected until the last possible moment.

That's true of direct injection in general. It happens that the Prius has never had direct injection, but that's not to say it won't in the future. Makes you wonder if a DI Atkinson Cycle engine couldn't have something like 18:1 static compression.. hmm. There's a lot about Atkinson Cycle that i'm vague on, like how you can inject fuel on the intake stroke and then blow it back out on the compression stroke before the intake valve closes, and account for that in subsequent injection cycles. I'm turning my brain off for the night.. 

Vigo said: There's a lot about Atkinson Cycle that i'm vague on, like how you can inject fuel on the intake stroke and then blow it back out on the compression stroke before the intake valve closes, and account for that in subsequent injection cycles. I'm turning my brain off for the night.. 

That actually might explain why the Prius doesn't use DI.  If it's pushing fuel back out into the manifold like that, the gains from DI are likely much smaller (if there are gains at all).  

Keith Tanner said:

Purple stock, blue Airaid intake plus TB spacer, red is intake plus chip.

Wild to see those sorts of gains on a normally aspirated engine. I can't imagine why the engineers would have left so much on the table.

Well, keep in mind that the Dodge 4.7 was doing just fine against the Ford 4.6 when it came out for example, and at first it was only in smaller trucks. Those Dakotas and Grand Cherokees were downright quick in that day with the 'detuned' 4.7, so Dodge didn't have to hit a very high bar to impress its customers at first. But impressing the EPA was not optional!!

I bout a 1999 GC which was the first of this series.  I loved that thing, it had the perfect mix of space, power, luxury and utility.  What else could you load to the gills with stuff, comfortably cruise 10 hours to the beach, then drive ON the beach or out to a fancy dinner?  

The first and 2nd gen Grand Cherokees definitely still have a useful place in the world.  There aren't a whole lot of other choices out there that are equally comfortable and not-massive with that same mix of off-road capability and not being over-complicated.  

While we're creating a soccer mom apocalypse vehicle, look at adding cheap headers and you will be flat amazed with what they give in MPG's tq, and hp.  They really are choked off by the factory manifolds and the aftermarket ones are CHEAP!!!  

pinchvalve said:

I bout a 1999 GC which was the first of this series.  I loved that thing, it had the perfect mix of space, power, luxury and utility.  What else could you load to the gills with stuff, comfortably cruise 10 hours to the beach, then drive ON the beach or out to a fancy dinner?  

Well, a Range Rover. Pretty much invented the luxury SUV space 

Headers, eh? Hmm.

The Jeep Wagoneer might have actually spurred the more luxurious side of the Range Rover. The Wagoneer and Range Rover wiki pages both seem to give the nod to the Jeep.

https://en.wikipedia.org/wiki/Jeep_Wagoneer_(SJ)#The_Super_Wagoneer

I suspect that was more of an example of parallel evolution. The Rangie was a big hit with the UK country set, I don't think Land Rover really paid much attention to what was going on in the colonies in the 70's - despite the fact that the original purpose of the company was export.