Performance for the 3.9

[dvsone]

Wut can I do to this 3.9 to give it some go. Cause the shiet is slow lol.. Wuts the best way to get it going??? Any thoughts will do thanks..

[RagingQuad]

Well, theres a ton you can do.... I would start with some of the basics like so:

*change your plugs to the Autolite 3923's, they run a degree cooler than the stock plugs and make a big difference. Also, change your cap & rotor with a Accell or Borg Warner Select cap & rotor. These have brass contacts and help put more current to the plugs. If your plug wires are ok, leave them....otherwise any 7.5mm wire will do just fine.

*Install an 180 degree thermostat. This will keep your engine cooler and deliver more HP.

*Install a cold air intake. Basicly, a cold air intake will deliver more & cooler air to the engine. Cold air intakes are pretty cheap. I use a Spectre intake for a Honda Civic that I found at Auto Zone....They fit and work EXTREMELY well. and for $50, you get an intake that looks a lot better than a homebrew and will give you some real gains :)

So if you've got $100, and want to add 10-15hp, I would start here, then work up to more serious mods like headers, cat-back exhaust, throttle body, etc....

If you really want to jump in, I have a used F&B 48mm Throttle body for sale (look in the for sale fourm)

I hope this helps. :)

[BIGDANO]

Raging, you got any pictures of that Spectre intake??

[miggity]

any of the bolt-ons listed will help, also consider electric fans. I've got em' and picked up serious gas mileage. They also scare the cat when they come on :)

-miggity

[DakIsBackJack]

When you go to the gas station next time, put 96 octane in itwith an additive used in crochrockets. Friend of mine did that once and........well........he don't got a ride now, nm bad idea.:confused:

[RagingQuad]

Theres a pic of the spectre intake on my site at http://garysdakota.1colony.com/truck.html Just click on the engine pic and a bigger one will show up.

BTW... I have seen the 3.9's actually suffer performance wise from running high octane. When I first started taking the truck to the strip, I was filling up with 93, and ran 17.6's But then one time I filled up with 89 and ran 17.2's

The stock 3.9 does not have a high enough compression ratio to fully utilize 93 or higher fuel. Stick with 87 for daily driving and 89 for the strip... just fill up at a shell, mobil, or BP. Stay away from the discount gas stations!

[DakIsBackJack]

yea stick with brand named gasses. there's only two types of gas stations within a 30 mile radius and thats a Hess and a "Safe-Way" gas station which is owned by Safe-Way Foods.

[frankromano]

if i get the 180 degree thermostat, don't i need to "re computerize" the engine to acknowledge the change or will it automatically pick it up?

[Doms360RT]

My stock 98 3.9 RC 5-speed ran 16.8 @ 80 stock.

[Milan]

my 00 cc auto 6er with big ass tires (i think 31.5) was doing high 17s :(

[Oski3]

I can't use these 3.9 v6 headers. Mine has the 3.7 in
it. Rather than send them back, anybody want them
for $359.00 plus you pay shipping I am in Florida.
Oski3@aol.com. or 813 788-0696

Bill OParowski

[Milan]

what brand and what are they made out of

[Oski3]

They are JBA Headers Nickel plated. but the number is #1939 that you can look up and make sure.
Thanks.

Bill OParowski

[Bigguy18LSU77]

what kind of gas mileage do you guys get? I'm getting around 16mpg in regular driving. I have the Airaid intake and dynaflow exhaust as well, but it doesn't seem to be helping me any. I have a 1997 dak extended cab. Don't know if it is a 3.7 or 3.9 I also have new plugs and wires and rotory on it. The filter is dirty, but that shouldn't drop my mpg should it?

[MoparREVolution]

what kind of gas mileage do you guys get? I'm getting around 16mpg in regular driving. I have the Airaid intake and dynaflow exhaust as well, but it doesn't seem to be helping me any. I have a 1997 dak extended cab. Don't know if it is a 3.7 or 3.9 I also have new plugs and wires and rotory on it. The filter is dirty, but that shouldn't drop my mpg should it?

You have a 3.9, and a clean filter is always better than a dirty one.

On a FULL tank of gas, in my 97 V6 RC....with alot of highway driving.......I get a whopping...............240 miles.........if I'm lucky!!

240 miles on a FULL tank of gas, and I hardly get on it either.....oh well I guess.

[Bigguy18LSU77]

What really gets on my nerves is that my mom has a 99 GMC 5.3 Liter 350 and she gets 22mpg. And I have a 3.9 liter and get 16mpg. That's just not eve right. She has more horsepower AND better gas mileage.

[ryan27]

I have an '02 3.9 and in conservative driving i get around 22-23 mpg. I think the most miles I've had out of one tank are 420 approx. I guess I get pretty decent milage.

[dakota_john]

I get about 22-23 mpg on the highway.

The most i have squeezed out my truck is 400 miles on a full tank of gas.

That's with a 3.9L with an Air Raid intake, JBA Headers, and cat back exhaust system.

I also stick between 60 and 65 mph on the highway. Anything above that and your gas mileage drops way off.

[dakota g33k]

my v6 is stock, best i got out of it was 22mpg on road trip dong under 70mph on the highway. conservative city driving gets me around 15~17mpg. farthest i've ever dared to go on a tank was 302 miles. get gas lights up at 200 city / 240 highway, usually takes at least 16 gallons to filll up the 22 gallon tank.

when i'd cruise 80mph on the highway my best was always 16mpg.

[spitz]

man with my 22 gal tank i always take it down to the red line and get between 320-340. once on a good trip i got 397 but that was all highway with a some idiling (i was delivering lost luggage at the time so it was with bags in the bad also) and have never put in more than 20.75 gal. so it has a "reserve" of 1.25 for idiots who try to use it past the E line.

[3.9dakota]

to answer frank's question, you dont need to reset anything with the 180* thermostat, you just put it in and go. it is all mechanical.

[venom]

I have a 99 dak with the 3.9. I have currently put on a set of JBA coated headers, Gisbon Dual Exhaust, a K&N air filter in an edelbrock air clean assembly and the thing is smokin, I mean no V8 but the thing hauls ass.

[Dodgerjack]

There are so many different ways these trucks are set up that can affect mileage. Just comparing a V8 to a 6 doesn't tell the whole story without taking these into consideration at a minimum:

Extended cab--weight
Topper or tonneau--weight, aerodynamics
4x4--weight, parasitic rotating mass
Gearing--engine rpm
Tires/wheels--engine rpm, weight, rolling resistance
Automatic vs manual transmission

I've always battled with around-town mileage. I think it has to do mostly with the extra weight of the extended cab, topper, and the parasitic drag of the 4 wheel drive. This is especially noticeable in the winter when all those gears and axles have to turn in the cold (sometimes below zero here in MinneSNOWta).

I've been keeping pretty close track for about 5 years, and these are my numbers with the 3.9 with the above equipment, plus automatic, 3.5:1 gears and K&N filter (otherwise bone stock):

Short trips only around town~11 mpg winter, 12 summer.
Mixed freeway and around-town~13 mpg winter, 14 summer
Highway, any season, at 60-70 mph~17-19 depending mostly on wind.

I have 15" wheels with 235 75R tires. I'm doing about 2000 rpm at 60-65.

I'm planning to put in an ACCELL or Borg Warner Select distributor cap as mentioned above (thanks) and see what happens with that.

[03quad]

Well ive got a quad cab 3.9 auto 25 gallon tank I left columbus Ga and arrived at orlando Fl in 5 hours approx 355 miles, max cruising speed 75 ish and still had a quarter of a tank left after that. ive got very mild mods bolt ons flowmaster cat back (not tru duel) and the power shot i think cold air intake from 360 air intakez
not bad for the heavy four door .

[Dodgerjack]

Wish I had that 25 gallon tank! I'm wearing out my gas cap with the 19.5.

If your gas gauge is exactly right, your mileage calculates to 18.9, which is really close to my typical highway mileage.

To calculate true mpg, there's no substitute for setting the trip meter to "0" at fill-up and then checking it against the amount you put in at the next fill-up.

[sailsurf7713]

bigguy, yeah a dirty air filter can really hurt gas mileage cause when the engine can't suck in an adaquate amount of air it sucks in more gas. and the dakota at 5200 pounds (extended cab) is an unnaturally heavy frigin truck so thats probably why you don't get the gas mileage of the GMC.

should i put 32 inch tires on my 98 dakota (2wd) or stick with the 30's?

[Milan]

an extended cab dakota only weighs about 4200 not 5200

[DigitalBoy000]

lol thats weird.... I've got a 3.9v6 in my 96 Dak 5speed and i'm getting like 20mpg and I drive the hell out of it too! :drive:

[greygoat94]

My 94 single cab weighs 4590. I wish I could shave off 300 lbs. lol I also have a tonneau cover with the 22 gallon tank and I can pull about 320 to a tank, but work is about a 20 mile drive on I-20 where I'm doin 70-80 depending on traffic

[Milan]

my old 00 3.9 cc weighed in at 4050 with me in it and i weigh 250

[92dakotahd]

My 94 single cab weighs 4590. I wish I could shave off 300 lbs. lol I also have a tonneau cover with the 22 gallon tank and I can pull about 320 to a tank, but work is about a 20 mile drive on I-20 where I'm doin 70-80 depending on traffic

Is yours a 4x4? A GenII should weigh in at 3400 for an RC and about 3800 for a CC if I am correct, those are approximates. GenIIs I *THINK* weight about 400 lbs. less than a GenIII of the same model (RC vs RC, CC vs. CC) So if yours is weighing in at nearly 4600 you've got to have a load of something in there.

I just got back from a trip with my truck to Tennessee, 22 gallon tank, made it 351 miles between fill-ups. About 17 or so gallons, the dummy light comes on really early, usually with about 5 gallons to go, I see no reason why on the highway this truck can go 400 miles.

Stats Are:
92 CC 3.9L Auto 175K (A500 with about 10K on it)
Trans-Go
K&N Drop-in
Dueller A/T Revos (11K) 235/75/15
Cat-back mufflerless duals
Mopar PCM (Runnin 92 Octane)
Soft tonneau and 2 peeps inside.

[Dodgerjack]

Is yours a 4x4?

Good question! This would make a difference, wouldn't it? Remember, you gotta consider all the variables--including body style and equipment (automatics, for instance, weigh more than manuals).

I looked all over the 'net last night for CURB WEIGHT figures and found nothing. One place you can look is on your vehicle's sticker, if you have it, for shipping weight (dry) or curb weight ("wet"). But the figure on your vehicle's door tag is gvwr or Gross Vehicle Weight Rating, and is the MAXIMUM allowed with vehicle fully loaded with passengers and cargo. This often tops 5000 lbs. I think my '96 extended cab SLT 4x4 with auto is 5450. This is NOT the vehicle weight though.

It makes sense that curb weight is hard to find specs on because it varies so much depending on the individual vehicle style and equipment.

You can always drive it on a truck scale! Say hi to the gendarmes. :wave:

[greygoat94]

I looked on the sticker in the door jamb, and it says 4590. 94 SC auto 2wd 3.9. Other than dropping my spare and a fiberglass hood, that's about what I'm stuck with on weight.

[MoPaR DaK]

bigguy, yeah a dirty air filter can really hurt gas mileage cause when the engine can't suck in an adaquate amount of air it sucks in more gas.
No it does not. If it really did do that it would run very rich. What really happens is there is not as much air to add to that fuel and there is not as much power being produced... thus the engine having to work harder and getting bad gas milage.

[MoPaR DaK]

If you want your sixer to move a little better then deff get a 48mm tb and get some lower ratio rear gears to help it along. Gears are not a engine mod but help a great bit. Go 4.10's for a automatic or 3.90's for the 5 speed. Gas milage will suffer from the gears though since everybody is so concerned with having a fast truck that gets great gas milage.

[Dodgerjack]

the sticker in the door jamb, and it says 4590.

greygoat,

Look at the plate again. If the number is stampted next to "GVWR", this would be your Gross Vehicle Weight Rating and NOT the curb weight. It's the maximum total vehicle weight allowed with passengers and cargo. Your curb weight is lower. If you have the original Window Sticker, it may give your curb weight or shipping weight. Curb weight includes fluids, shipping weight is "dry." These vehicles are heavy, but thankfully not THAT heavy. Go ahead and put your spare back in--you might need it!

[go---fish]

I do think "bang for your buck" is spent best on the throttle body. Just simply slapping the wider v-8 seems to bring in the difference .. then with the cold air intake - thats well under $200 - $300 range and seems to get the most improvements.

[ritual3313]

I have a 89 4x4 with a 3.9 Carb on it. Anything I can do really or am I S.O.L.?

[MoPaR DaK]

You have a premag V6, very very limited.

[Dodgerjack]

I just had my best performance/mileage gain yet with one simple "mod": FIX THE STUPID DISC BRAKES! They were evidently dragging badly, even though I had no noticeable pulling to one side or the other. New slider bolts (along with pads and rotors) freed everything up nicely, and I went from 14 mpg in general all-around driving to 17 on the very first post-brake-job tank! Noticeably peppier too. :woowoo:
This won't work for everyone of course, but it's an overlooked factor especially for a person who's lazy about brakes like I've been. They were "inspected" regularly but none of the "inspectors" ever really looked closely--obviously because the last brake job (before I bought the truck) was done by some moron who stripped a slider bolt and just left it out! Lucky for me, there is a replacement available with self-tapping oversized threads, and it worked. :bow:

[Slow97dakota]

lol@ all the responces and only a few in this post helpin the guy out. 1.7 roller rockers are availiable and u can port your stock intake manifold, all worth good gains, leave headers till the end

[Dodgerjack]

...only a few in this post helpin the guy out.

Ya never know what'll help--and he asked for "any thoughts." Weight+drag=big performance drains. Sometimes, the engine isn't the problem ('specially when it's a 3.9 Magnum) :biggthump

[realdeal7369]

What really gets on my nerves is that my mom has a 99 GMC 5.3 Liter 350 and she gets 22mpg. And I have a 3.9 liter and get 16mpg. That's just not eve right. She has more horsepower AND better gas mileage.

the 350 has been around for ages, so its safe to say its been worked oven on over the years to get the best out of it. very efficient motor for some reason. its all in the cam, and heads, and how it all interacts with one another. take your heads off your 3.9, shave then, do some port and polish work on them, im sure youll see a difference.

wish i woulda did that to mine when i had them off at one point.

[KREWZER]

Do the 99s have that "power on demand" thing? where it cuts out to four
cylinders?

[Slow97dakota]

Ya never know what'll help--and he asked for "any thoughts." Weight+drag=big performance drains. Sometimes, the engine isn't the problem ('specially when it's a 3.9 Magnum) :biggthump
re read the thread. the entire thing! then tell me that 2/3's of this wasent useless to his ? im not badmouthin ne 1 just thought that was funny

[KREWZER]

Read any thread, almost all of them get off topic somewhere :jester:

[Dodgerjack]

im not badmouthin

SLow97,

No worries, man, I didn't think you were badmouthin' anyone, and I wasn't trying to badmouth you, just pointing out that strange little things can cause slowness (in me and in my truck*). It's maybe a good idea (and courteous) to stay somewhere in the neighborhood of the original topic, but "thinkin' out loud" seems to have solved a lot of questions of the automotive variety. Enjoy! :wave:

[92dakotahd]

Do the 99s have that "power on demand" thing? where it cuts out to four
cylinders?

The only vehicle I've heard of that on in a mopar is the Hemi cars and the multidisplacement system.

[KREWZER]

Yeah i dont know, I dont know anything or care about GM, although ive heard that the Canyons or whatever truck it is with the Inline 5, the fifth cylinder cuts out.

[N56629]

Some enterprising 3.9 owner might be able to make this work. I'm thinking that it will go cheap enough to give it a try.

3.9 Supercharger (http://cgi.ebay.com/ebaymotors/C30-NOS-V6-3-9L-B-M-SuPeRCHaRGeR-KiT-Dodge-Ply-Chry-NeW_W0QQcmdZViewItemQQcategoryZ10076QQitemZ4573857 515QQrdZ1QQsspagenameZWDVW)

[KREWZER]

Yeah i saw that too, its for Pre Mags though. Unless u wanna switch ur engine to carb.

[N56629]

Yeah i saw that too, its for Pre Mags though. Unless u wanna switch ur engine to carb.

I think you could convert the manifold to injection by adding bungs. Not sure how the rest would work. I didn't look that closely. I just thought someone might be interested.

[KREWZER]

would that work? If u drilled out the holes for the injectors?

[N56629]

would that work? If u drilled out the holes for the injectors?

You would likely have weld in some bungs. You can buy the M1 intake with or without the injector holes but the bungs are cast into all of the manifolds. I've seen a number of different manifolds with this modification but I'm not sure that all manifolds work equally well. You would have to be able to get good alignment with the valve ports and fab your own fuel rails.

I'll have to see if I can find some pics of a modified manifold.

[KREWZER]

too much work :biggthump

[N56629]

This might help.

http://www.force-efi.com/machefi.htm

http://www.injector.com/fuelinjectorsaccessories.php

[KREWZER]

Thats cool as hell, i knew it could be done, but i dont have the money for something like that. I bet that B&M Supercharger on a MAGNUM V6 would definitely be a ONE-OF-A-KIND though.

[Dodgerjack]

I believe that the Colorado is the Chevy with the 5 cylinder. With one cylinder that cuts out? What'll they think of next? I've heard the "5" is supposedly a "highly rated" engine by the automotive press, but I wonder what they'll think of it in a few years. Considering how lousy the "8-6-4" Cadillac engine worked, I'd hold out on the cut-out engines, even though electronics is a lot better than it was when that one came out. They virtually all got converted back to plain old "8"s pretty quickly. An aftermarket kit? Call me old-fashioned but I'm skeptical.