It would look really goofy but the question was about an easy power increase and smaller tires will do just that.
As far as looks go I think 255/70/17 is a good size for a two wheel drive.

 

since that post was originally made, and after over 10k miles on the rig- my perspective has changed... understand, some of these mods are sustainability mods, others for performance- but here they are:

1. gears.. no single mod has done what the gears have done.. it was the most expensive.. instant performance, and makes life easier on all other parts and pieces.. if I had to choose just one- it would be gears..

2. SCT.. I know there are other options similar such as Mopar PCM w/B&M flash, or hypertech, or superchips- but I'm happy with the SCT.. since the original purchase, I went back and dropped another benji to get the unlimited programming.. basically, to support the heavier injectors- but also to support a cam swap which is in my future..

3. exhaust.. opening up the exhaust gave me power, gave me better mileage, and altered the power curve to produce more at a lower RPM (and more at a higher, but I wasn't aiming for that).. eliminating the Y pipe was the single most important part of it..

t4- intake manifold.. eliminated the concern for the plenum gasket blowing ever again.. coupled with gears, it doesn't hurt bottom end..

t4- timing chain.. more precise and less slop.. 'nuff said..

t4- e-fans.. the engine doesn't have the parasitic loss of power under 1kRPM it did before.. meaning, more torque to the terra right off the line.. which is nice to have when towing/hauling/pushing if you plow.. they have turned out to be very reliable, and my needle hasn't past the 1/2 mark in ANY conditions since the install.

t4- aux tranny cooler/ external filter/ check delete.. I'm running on a OE tranny at 164kish miles.. it's still strong as ever.. it's not broken 180* since the install one single time.. cooler trannies are happier trannies..

t4- gauges.. I have a pillar pod w/3.. wideband a/f, tranny temperature, and vacuum.. these, when monitored and when you pay heed to what they are saying are something I will never go without again.

5. good ignition parts and pieces.. not necessarily expensive, as is the case with champion plugs being much better than NGK iridium, but good quality parts..

6. goodhood ram air.. cooler intake temperature is always better than warmer.. i now have a true CAI, and good flow.. i squeezed an extra 1~1.5 MPG's with this alone..

honorable mention: H&S 1.7 rocker rollers.. they should have made the above list, but they are simply trumped in my opinion by the ten above- and this is a top ten list after all.. they reduce parasitic loss through the valve train, and provide more lift to the valves.. they aren't to be ignored, but they are still just a band-aid to the tiny toy cam that is OE on these things..



now, if I had it to do over?

1-gears
2-permanent plenum fix- plate or A-G
3-exhaust
4-tuner, to prep for:
5-cam, RV cam, or 206x (complimented by gears I could use the 206)
6-TC of decent quality and matched to weight/purpose/RPM range
7-efans
8-complete tune, including timing chain
9-gauges
10-tranny cooler/external filter/check delete

THAT course of action, and nothing else needs to be concerned with..

 

Very interesting drew. Couple questions.

Any idea what your total mpg's improvement is in it's current state as compared with a stock config? I ask since your current list is about identical to mine with the exception of a couple of the mileage mods I've yet to install such as efan and ramair. Just curious about where I may land mileage wise.

Edit: please disregard the following paragraph. google is my friend.
Do you know a (safe) way to have fuel pressure be one of the gauges? I think my ideal scenario would be 1. fuel pressure 2. A/F ratio 3. vacuum. I'd probably end up with an oil pressure gauge too though since I'm doing it might as well do it right. Note I'm not saying tranny temp since I have no torque converter.

 

I get the same mileage as I did N/A and I usually have some right foot playtime while doing it. It also drives like stock until I put my foot into it.

How's this for turbo lag?

 

I've never owned one of the V6's. I understand there is a Mopar PCM which is supposed to work with them. Also you could likely do things to the exhaust. I'd bet the throttle body mods would also apply. I'd call John at SE and see what he says. It's like being in the twilight zone but the dude seems to know alot abut these things.

 

I'd have to put stock wheels/tires back on to get accurate info on that.. it's not the height or width, though that certainly factors too, as much as it is the weight of those dang things.. I would estimate a stock steel wheel and OE tire to be somewhere in the neighborhood of 80 pounds.. I happen to know for a fact the wheel/tires I'm using are 180#.. that's 320# (estimated) compared to 720#.. the rolling resistance is much greater with the wider and more aggressive tire, as well as the height of the tire altering (which was somewhat addressed by gears)..

I'm guessing here, but I'm of the opinion that if I swapped back to stock tires/wheels, and took the heavier suspension (lift) parts and pieces off and returned it to stock, I'd get somewhere around 17 overall MPG's.. that would be 15~16 city, and 19~20 or so highway.. that's with a heavy **** 3rd gen QC, 5.9L 4x4.. As it is, I get just over 13 city, and right at 13.5 highway (those dang tires, man).. something that's happened to me recently is that has edged up to nearing 15 highway.. I'm trying to track down why in another thread.. My truck, stock, turned about 12 city, and 14~15 highway..

a bunch of things happened at once mechanically, and then the gauges and monitoring software got involved and altered my driving style.. For instance, (and I don't care to argue it, I just know it to be true) decently rapid accelerations are easier on fuel than slow rolls up to speed.. Yeah, I dump more fuel quicker, but I get 'out' of it instead of prolonging it.. it sounds like a word problem from 5th grade math class but: "using 300cc of fuel per minute for twenty seconds < using 200cc of fuel per minute for forty seconds"..

anyway, fuel consumption was something I actually watched.. here is what happened, IIRC.. If I hadn't changed the wheels/tires/suspension, the same ratio should hold accurate as well:

headers- very little.. like, nothing..

cut out Y pipe, ran dual exhaust w/x-pipe- as much as 2mpg.. BUT, this goes back to 5th grade math class again, because opening the exhaust opened some usable power in a lower range, meaning less go-foot.. did it improve engine economy or did it eliminate the need to 'get into it deeper for the same performance'? I don't know.. I'd lean toward the latter, though.

e-fan: eliminated parasitic power loss.. more energy off the line to get things rolling with equal engine speed.. I can't get around that in any way to discredit the fact that more toque is present at engine speeds just over idle.. I think the engine catches up to it pretty quick though, meaning the 'performance' aspects of running an e-fan set-up is lost on these engines when the engine speed breaks 1kRPM or so.. but, that torque is there below that, that wasn't before.. and- it's PRECISELY where you need it most.. back to 5th grade math class, and factor that in too.. I know the fans give me at least 1MPG more- but that 1MPG is going to be evident in city driving only.. put her on the highway, and there is NO benefit to e-fans..

ram air hood/ true CAI: for every 10 degrees lower intake air temperature, add 1/2 a pony.. simple fact.. 40 degrees (I do this in the winter easily), is 2 ponies.. that is simply the air density measured by temperature scale.. there is more in play here.. cooler air is denser air so more o2 is crammed in the cylinder with each gulp.. what is sometimes forgotten, is that more air means it needs more catalyst (fuel), BUT, that it's safer to advance timing on (as per IAT bouncing off of coolant temperature and o2 sensor readings).. advancing the timing closer to TDC? less head space, more confined space for that magic explosion, and less concern of the engine pre-detonating the charge.. the most magic place is a fraction of a moment before TDC, so by the time the piston actually hits TDC, the explosion is just starting to push with vigor.. now, this ain't no race engine, and this isn't happening in mine- but, the PCM can allow advancing of timing as much as 2 degrees when it detects it's safe to do so.. BLAM.. more ponies.. more go-go compared directly to a warmer air (less dense) air charge.. it's because of more o2 getting into the cylinder as well as the engine advancing spark.. but let's focus on the a/f (it runs richer at the same time), and go back to 5th grade for a little bit:

the a/f is STILL at a comparable ratio as it is without the cooler air- there is just more of it, and therefor, more fuel.. as long as the advance in timing occurs, there is benefit.. if there is no advance in timing, your only taking advantage of the added o2+fuel.. you don't get as much use out of it, it is my contention.. but if it does? more go-go with less RPM.. you get to speed quicker..

gears- I hate this.. but I'll try.. there is a mechanical and absolute measure of RPM's vs. Engine Speed vs. Gear Ratio (tranny, ring and pinion, tire height).. it can't be argued.. If I were to tell you my overall drive ratio (involving all reductions/amplifications), you could tell me my engine speed... <- that's a period.. you could do it from the opposite direction too.. meaning, I tell you engine speed, and ratio's, and you tell me forward speed..

manufacturers use this ratio to cheat.. they post MPG's based on the math and ratio's.. and figure displacement in there, and how much fuel the vehicle consumes at that engine speed while maintaining 14.7:1 a/f ratio..

this is hogwash.... unless you are on dead straight, and dead flat roads, and in winds of zero value, you are NOT maintaining 14.7 and steady vacuum at any speed.. you're either goosing it to maintain speed a little, or you're floating it to shave some off.. the engine is either loaded, or it isn't.. the a/f changes when you are accelerating because it has more fuel- it doesn't respond instantly- it has to catch up to the amount of air/fuel you are putting into it- while doing that, it doesn't burn fuel until it catches up.. it passes it right through your exhaust..

the trick is finding the right gear to get forward speed while NOT dumping a ton of excess fuel, and having the right overall gear to maintain that speed without having to constantly pull or push fuel.. you want it on a plane.. like a generator sits at a steady speed as you pull load (electricity) draw from it.. .. It's been my experience that is almost impossible to do with these rigs.. you're either low geared to get you there easier and then pay for higher engine speed, or you struggle to get there with higher gears but settle way low in the RPM range holding it..

in a perfect world, your o/d gear would be a lower ratio than it is.. it would not drop all those RPM's when shifting to it, making the truck a dog and making it struggle to just maintain speed.. And, God help you if you're trying to accelerate in 4th.. if mother Mopar wasn't using their calculators and trying to appease the government, a lower ratio o/d would have been employed that allows the engine to 'plane' off a lot easier.. but they didn't.. and we load the engine just trying to maintain speed.. it sucks..

you have a manual shift.. I had one several years ago in a dakota.. I don't recall 5th being as big a dog as 4th is on these, but I don't recall it being good either..

to combat the load at cruising speeds, we build up the engines output- or attempt to lower the power curve to a place just above or right at the engine speed at forward cruising speeds.. and, we fail miserably. and, because the platform mother Mopar left us with is demanding in one location (down low) or the other (up high).. that's why, in my opinion, these engines are so hard to figure- and why it's hard to compare my truck to someone else's or vice versa..

the trick with gears, is this; keep the engine unloaded at the forward speeds you most often use.. throw RPM's out the window, because even though they factor into the equation, it's my contention they don't do so as much as that engine load (vacuum, a/f ratio) does.. edited to add this: highway/street speed limits are what kill our mileage.. if you were to totally ignore them, and do what you wanted to do instead of what the government specifies is safe for all, you could make forward speed match engine speed and keep it at a perfect constant load- and conserve fuel.. but, you'd also be doing about 45~47mph on the highway, and 30mph or so on city streets.. if you were to just try that for a tank of gas, most folks here (with healthy engines) would see 15~16mpg city and 20 highway easily.. but, c'mon, we're simply not going to drive that slow, right?

also, and this is huge- I run my truck near sea level, and through very little elevation change (hills), so, I'm going to get numbers that most of you won't when it comes to mileage.. I don't have to run my truck near as hard as y'all do..

jesus. that turned into a book, no?

 

yea it did, but its very informative. anyone that reads this thread is going to learn something. this should be made into a sticky for those that are goin to continually ask questions imo.

 

Wow "book" may not be a strong enough term. I'm thinking novel.

Thanks for the details man. It's very helpful.

What tires are you running? I think you said 35" right? That's what I'm running so we should be fairly comparable in that respect. Though you have the 3rd gen body and the 4.56's so it is true that comparisons are hard.

Still I was hoping you'd say something better than 13.5. It must have really sucked the gas when it was pre mods.

 

if i hadn't done anything but the lift and tires, and left the engine and gears alone, i'd beyond doubt be in the 8 overall mpg range, and maybe hit 12 on the highway due to higher axle ratio + higher overall ratio due to tire height..

I pay with the lower gears on the highway.. I make up for it in the city..

with the mods, sans the gears and tires/lift- I could no doubt touch 19~20mpg highway, there isn't a doubt in my mind..

growing up, I had a buddy with a dodge colt.. a 4 banger POS with only one single good thing about it.. it had a two speed rear-end.. you shifted gears (manual either four or five speed), and when you were done, you could clutch it one more time, and pull a lever that shifted it into a higher axle ratio... you simply chose one of two axle ratios depending on use.. we would goof off and shift all eight (or ten, if I could recall the gearbox) gears just to make things interesting..

I wish like hell I had a two speed rear-end substantial enough for this rig.. I'd have a 5.12:1 and a 3.23:1, and I wouldn't need that goofy o/d anymore..

yes, I run 35" Cepek FCII's.

 

Man that would be so cool!

I always liked the Colts. There was one version with a Rabbit engine that ran really well, well for being a little POS that is. I doubt that was the one you had though as the water cooled VW engines mate to front drive tranny. I liked those things.