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Jared
Dodge Dakota
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8/01/2002
22:56:36
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 Subject: Why is my 4.7 backwards?
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Everybody knows that the 4.7 is a highrevver, and that it lacks the low end of the 5.9...well..my 4.7 auto can smoke the tires anywhere in first..but up top it just leaves something to be desired..like its being held back..i havethese mods:
2 40 Series Flows turned down
Airaid
Third cat removed
the removal of the cat helped some, but it still takes a while to hit the speed limiter, i think m old 5.2 ram w 14x3 k&N, no cat and th same muffs was faster after 80...what do you guys think?
TIA
Jared
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Clevite 77
Dodge Dakota
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8/01/2002
23:49:06
| RE: Why is my 4.7 backwards?
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what year?
how many miles?
take off the airaid, and put the stock back on, just to see hat it does
I did the same, exhaust wise, and did a h-brew, pvc-cone k&n air filter, I have a 4x4 that bearly spins them with 1/2 tank of gas. (2002 CC 4x4 4.7L 3.92's w/LSD) I have some mean top end though, and once I hit about 2500 R's then I'm good to go.
Good ol chrysler, let's put an OHC motor in a 4x4 truck, yea thats smart.
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CThomp
Dodge Dakota
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8/02/2002
09:31:02
| RE: Why is my 4.7 backwards?
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I have a '00 4.7L 5spd. I can smoke the tires though 3rd if I want to. Current mods are:
68mm Fastman
360airtakez
3923's
180 t-stat
very very soon:
carsound cat and some kind of muffler to put in place (can't decide what kind I want though i'm leaning towards an edelbrock or magnaflow)
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CThomp
Dodge Dakota
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8/02/2002
09:34:07
| RE: Why is my 4.7 backwards?
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Why are you running duals? That could be part of the problem. Run a single 2.5" with a high flow muffler. Changing the diameter of the pipe causes low-end loss.
Try a new TB. Fastman makes and excellent 68 and 71. I may get the 71mm in the future if I get bored.
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Jared
Dodge Dakota
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8/02/2002
10:51:26
| RE: Why is my 4.7 backwards?
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The exhaust is there for sound only, and I didn't really notice a loss in low end..but I didnt gain up top either. Its a 2002 RC 4.7 Auto 3.55 with about 6500 miles on it. I am thinking about ditching the Airaid in favor of a homebrew as still have the factory airhat. I have a HUUUUUUGE K&N cone (twice as big as the Airaid filter) Do you guys think this would help a little bit? What about the KB Optimizer Flash? Ive got the money saved up for that I'm just waiting on a window in whice I dont need my truck for a few days. Also anyone that has the flash with an auto, did it stop the hesittion between shifts? Like the engine shutting off, shifting, then coming bak on? Thanks alot guys
Jared
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Duner
Dodge Dakota
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8/02/2002
11:14:23
| RE: Why is my 4.7 backwards?
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I wonder if the KB Optimizer will help with the shifting. The hesitation is actually programmed into the PCM to help improve transmission life (supposedly). I do know that when we put my PCM from my manual trans truck into a truck with an automatic - that it shifted HARD! It would bark the tires at every shift.
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Demon Dakota
DakotaEnthusiast
8/02/2002
12:12:51
| RE: Why is my 4.7 backwards?
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Hard shifts aren't necessarily a bad thing. All that lag and drag through the gears changing is supposed to be harder than a nice firm shift. Sure it's nice for the comfort of those people who drive their trucks and SUV's like cars and minivans, but for those of us who prefer crisp shifts to maximize performance, well, you know the rest...
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Jared
Dodge Dakota
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8/02/2002
13:26:27
| RE: Why is my 4.7 backwards?
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DUNER!! LET ME BORRW URE PCM LOL!!! I guess Flash time for me..thanks alot guys
Jared
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LQ Jones
Dodge Dakota
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8/02/2002
13:32:09
| RE: Why is my 4.7 backwards?
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Message:
I think it would help if you replaced your 3.55's with 3.92's. I order you to do that.
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kota on 20s
GenIII
8/02/2002
13:45:07
| RE: Why is my 4.7 backwards?
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the 3.92's will add more to the bottom, but not on the topend. just get a supercharger or have duner make you a turbo...hehehe
Eric, 98 5.2 5speed, K&N gen II, 50mm TB, 2bbl M-1, 1.7RR's, JBA ciramic headers, carsound cat, dumped gibson, and a lot more
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Clevite 77
Dodge Dakota
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8/02/2002
13:48:08
| RE: Why is my 4.7 backwards?
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the bigger filter really won't do any good, as long as the one you currently have isn't tiny, once you get to a certain point, your tb will only suck, in so much air. it will however stay cleaner longer.
hey CThomp, hows that 68mm treating you? I now wanna say forget this whole 4.7L stuff just put a 5.7L in an R/T and I'll buy it lol.
I would guess that his "freer" flowing exhaust would hurt low end and gain top end. at least mine did. Unless.......the exhaust shop screwed something up. Look underneath and see if there is any crimps in there or excessive, or sharp bends.
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Rob
GenIII
8/02/2002
13:59:33
| RE: Why is my 4.7 backwards?
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Message:
Jared- I understand what you are saying but the fact is the motor is a high rever and has great quick acceleration that seems to drop of at the higher speeds.I feel the same way that is why I am going to switch my 3.55 to 3.92 or possibly 4.10 so it will hold the high rpm and hopefully pull much better through the higher speeds.
robertshaw 180 thermostat,Z-Tube,Magnaflow stainless exhaust,jet stage 2,throttle body spacer,,Street scene bumper cover,Stull full billet grill and shell,street scene gen 2 rollpan,Apc clear corners,Apc euro tails,DJM 2inch control arms and 3 inch block,power slot brake rotors 18x8 boyd atlas rims
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Clevite 77
Dodge Dakota
JOIN HERE
8/02/2002
14:02:01
| RE: Why is my 4.7 backwards?
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hey kota on 20s,
I'd say your statement is a bit off,
3.92's will give you more power throughout, unless the guy with 3.92's is at 6,000rpms, he'll always have more power.
think of it this way, (5spd) if your in 5th at 60mph and you nail it, it'll just bog down, now if 3.92's resembles lets say 3rd gear, and you nail it, you'll get more pulling power.
what 3.55's will help you with is gas mileage and it'll keep the engine r's down. Now a 3.92 will run out of gear before a 3.55 will. And what I mean buy that is if, the motor had enough power to reach 6,000 rpms in it's top gear, with both 3.55's and 3.92's, the 3.55 will have a higher top speed, but not pulling power.
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kota on 20s
GenIII
8/02/2002
14:46:00
| RE: Why is my 4.7 backwards?
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Message:
Clevite, what i was saying is that, say you were at WOT. the 3.92's will get you moving faster, but the only thing that will make it "seem" like it is pulling harder is because the engine is reving faster.
i know what you said is correct, and that is because with the 3.92's the engine is in the powerband and when you hit the gas, you will get a better responce because if that.
Eric, 98 5.2 5speed, K&N gen II, 50mm TB, 2bbl M-1, 1.7RR's, JBA ciramic headers, carsound cat, dumped gibson, and a lot more
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CThomp
Dodge Dakota
JOIN HERE
8/02/2002
15:32:41
| RE: Why is my 4.7 backwards?
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The 68mm is great. Did you ever invest in one?I'm moving on to exhaust now. I don't know how much a carsound cat and edelbrock exhaust will help me but i'm pretty sure they won't hurt me as long as I stay with the stock diameter pipe.
By the way...any idea how long the stock muffler on the 4.7 is?
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Rick
Dodge Dakota
JOIN HERE
8/02/2002
16:19:59
|  RE: Why is my 4.7 backwards?
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Message:
The only diff. between the 3:55 and the 3:92 is wheel and tire size,A 3:55 with 15in wheels and tires are the same as 3:92 with 16in wheels and tires. Try it if you have a 3:55 with 16in wheels and tires,Try to get some one with 15in wheels and tires to put on your truck.
1in means alot,Unless it's 4 your wife. hehe
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kota on 20s
GenIII
8/03/2002
00:42:36
| RE: Why is my 4.7 backwards?
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Message:
Rick, we are talking about actual gear ratio's... not the adverse effects that tires have on gear ratio's. also, rim size has no bearing on how a tire changes the ratio. it is all on the tire size
take me for example, my stock 215/75/15's have a bigger overall diameter than my 255/35/20's! even though my current rims are 5 inches bigger than stock, the OD is smaller! this brings my stock 3.55 ratio to a 3.64, thus giving me better acceration over the stock size (not to mencion better grip on the road)
Eric, 98 5.2 5speed, K&N gen II, 50mm TB, 2bbl M-1, 1.7RR's, JBA ciramic headers, carsound cat, dumped gibson, and a lot more
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Bob W
GenIII
8/03/2002
10:42:24
|  RE: Why is my 4.7 backwards?
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Message:
Kota, I don't think you will get better grip with 215/75's over 255/35 the 215 would be 8.5 " wide and the 255 would 10.0 that is a lot more rubber on the road and the lower profile tire should add even more.
Let me know if I'm missing something.
Bob
Gibson headers, Gibson Cat-back, Edelbrock IAS shocks, K & N drop in, 180 stat, Jet stage II chip, ARE Lid
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Rick
Dodge Dakota
JOIN HERE
8/03/2002
15:34:16
|  RE: Why is my 4.7 backwards?
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Message:
Kota what I was saying is that a truck with 3:92 gear with stock 16in wheel and tire turn the same RPM'S as a truck with a 3:55 gear with 15in stock wheel and tire.
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kota on 20s
GenIII
8/03/2002
23:22:10
| RE: Why is my 4.7 backwards?
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Message:
yeah bob, you are correct. i was refering to getting better grip with the 255's.
rick arnt the 16's a 255/65/16?
Eric, 98 5.2 5speed, K&N gen II, 50mm TB, 2bbl M-1, 1.7RR's, JBA ciramic headers, carsound cat, dumped gibson, and a lot more
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kryp2nite
Dodge Dakota
JOIN HERE
8/03/2002
23:28:48
| RE: Why is my 4.7 backwards?
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Message:
wouldnt better grip also depend on the quality of the tire?
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CasuObserver
Dodge Dakota
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8/04/2002
22:38:31
| RE: Why is my 4.7 backwards?
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Message:
Maybe not so backwards as you might think. (Check out: http://www.e31.net/navmisc_e.html, ->Misc ->Torque & HP.)
What you're really interested in is the amount of torque available at the engine at a particular rpm, and at the gearbox in the gear you've selected, and at the rubber on the road.
First, power is a mathematical function of the dyno-measured torque and whatever rpm the engine is running at to make that torque. Secondly, power is the amount of work an engine does per unit time. So, torque is directly important in acceleration, power is only indirectly so.
The article states that you want an engine that has higher torque available at higher rpm ranges, so that you can maintain maximum torque longer, without having to shift up. You have to shift up, because there is a point where you start to 'waste' engine power at the upper end of the power band. Power is 'wasted' at the top of the power band (even as the power band is still going up), because at some point absolutely less torque is being generated despite greater fuel burn. Torque is what is really useful in acceleration; not power. In the chart, from 5000 to 6000 rpm, power output (and fuel consumption per second) is still increasing, but torque is already decreasing. So the motor is working harder burning lots of fuel & making lots of noise but delivering absolutely less useful torque. When that starts, you have to gear up. However, if the torque curve follows the power curve more closely to its limit, then you can make more use out of the maximum amount of fuel that a motor can burn.
Turbocharged engines really flatten the torque curve, making max torque (& therefore acceleration) available at a wider rpm range. At extremes in the rpm band, an increase in power isn't necessary in order to get the increased torque (and therefore increased acceleration) on both ends of the curve. Can't do that with normal engines though, so you just try to shift the torque curve as high as possible to make full use of of the engines power band.
Also, it claims that a motor with a very high redline mated with short gearing will give a much higher gearbox torque, and therefore much higher acceleration. (If compared to a motor with low redline). I'd assume though, that you'd need a flat torque curve available over a wide range of rpms.
So,
= you'd have to look at the theoretical and dyno'd power and torque curves of your 4.7 engine (to see if there was anything unusual and for further calculations). Also get the dyno'd (torque) curves of the truck at the gearbox for each gear (plotted against rpm and highway(wheel) speed and calculated powerband).
= Look and see how your gearbox torque varies with your rpm/wheel speed in each gear to see at what vehicle speed your best acceleration would/should be for that gear (i.e. speed & rpm where you have maximum gearbox torque). That will give you a better idea of what the Dak is really doing, and where torque/max acceleration would be starting and dropping off in a particular gear
= Look and see where your rpm is for any highway speed in a particular gear, and look to see where on the torque/powerband you are for that rpm.
Build yourself a spreadsheet using gear ratios and engine dyno results to see which gear you should be running in at a particular highway speed, and where you should be shifting.
When you check out all the curves this way, if you see anything screwy and illogical, find out what the problem could be. Maybe it's the way the computer was programmed, to deal with things like emissions or vehicle structural limitations. Or maybe, there is actually a maintenance problem or design oversight that you can fix with aftermarket parts.
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