General Modding question

Have a 2002 Dodge Dakota with a 4.7 engine using the JTEC controller, still on the stock tune and am waiting for the mods to be done before tuning.

What I have done...

• 70mm TB
• Airaid intake tube
• turning vane for intake tube
• air box baffle to remove turbulence
• insulated a lot of heat sources
• fuel rail wrapped

Left on the list to work on

• JBA headers in the garage
• custom Y pipe with the ability to insert a flow restrictor plate/reducer (low end torque)
• new cat
• cat back exhaust
• HPT tune

Motor rips pretty good right now and now have an issue with a mis-fire on 1 cylinder (7) but only under certain conditions (high load, low MAP)... no codes other than the mis-fire code.

Question I have is, since this motor does not have knock sensors, is it possible that these mods are now forcing me into a higher octane fuel? (still using regular)

It occurred to me this morning this might be the case and plan to test it out.

With what I have achieved, if I never tuned it... I would not be disappointed. But... still planning to optimize the exhaust next. Once I solve the mis-fire, the plan is to do the headers, then y-pipe, cat & cat back exhaust then tune it.

TIA

Miss fire could be bad plug,……….

Air Ram has some good parts for the 4.7, they’re the one to talk to about it,

Whoops... forgot to mention, new plugs recent coil packs and injectors. The only time the mis-fire occurs is when on it hard and it is always cylinder #7. This problem never shows itself when I behave.

Been a lot time since I played with a 4.7, shame of it is it’s got potential, just no support.

Talk to the air ram guy. I had a 2000 4.7 5 speed rc4x2 Dakota, fun truck, miss it but just not enough play toy parts for them.

The oem intake manifold is notorious for poor fuel distribution, but honestly I don’t remember how it affects 7, if this was high load high rpm It would be the result of the stock manifold , # 5 draws air just before #7 , but low map high load you’ll not see those issues.

Do you have any log files? Do you have a tune pulled from the computer?

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Originally Posted by PurpleRam

Been a lot time since I played with a 4.7, shame of it is it’s got potential, just no support.

Talk to the air ram guy. I had a 2000 4.7 5 speed rc4x2 Dakota, fun truck, miss it but just not enough play toy parts for them.

The oem intake manifold is notorious for poor fuel distribution, but honestly I don’t remember how it affects 7, if this was high load high rpm It would be the result of the stock manifold , # 5 draws air just before #7 , but low map high load you’ll not see those issues.

Do you have any log files? Do you have a tune pulled from the computer?

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I will email them (Air Ram). I bet that 2000 dak you had was fun... being a truck guy, I have thought of trying to locate a RC 4wd 5spd truck to shift over to from the QC truck I have now (which is a 2nd truck & a backup to the 2005 Ram cummins truck I have). the thought would be to shift over to an awd transfer case, lower it and make it more of a street truck since I have the Ram for off road use.

On the oem intake manifold comment... the not sure how you mean that since it is port injection. The injectors I dropped in there are a 12 hole injector (miss existed before the manifold & injector swap) and appear to be working as expected. I cleaned them in an ultrasonic tank prior to the install.

I have the oem tune pulled but have not logged anything on it yet, dont have the bandwidth (too many open projects on the plate atm).

I am going to dump in premium on the next fillup & see if the problem repeats. (my goal was to get the most out of the engine on the worst fuel, I may have found that tipping point)

The 5/7 thing relates to dry air flow before injector, let’s say #5 gets 100cfm of air & .0660 gms of fuel, # 7 might get 98cfm &.0660 gms of fuel, logic dictates 7is richer than 5 at this point, so 7 stumble, wet manifold would be different. Now in high map situation its more likely, now the boosted crowd do not have this problem, the “boost device is force feeding the cylinders, while na (fundamentally) has to solely rely on vacuum created by piston draw to fill the cylinder, low map situation there’s more “air” to draw against than high map. Low map(10-40kPa) high map (70-105kPa)

Quote:

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Originally Posted by PurpleRam

The 5/7 thing relates to dry air flow before injector, let’s say #5 gets 100cfm of air & .0660 gms of fuel, # 7 might get 98cfm &.0660 gms of fuel, logic dictates 7is richer than 5 at this point, so 7 stumble, wet manifold would be different. Now in high map situation its more likely, now the boosted crowd do not have this problem, the “boost device is force feeding the cylinders, while na (fundamentally) has to solely rely on vacuum created by piston draw to fill the cylinder, low map situation there’s more “air” to draw against than high map. Low map(10-40kPa) high map (70-105kPa)

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AFR in cylinder makes sense... with what your saying running a higher octane fuel should not change anything, assuming the scenario you mentioned is what is happening under those conditions that set the code.

Trying to wrap my head around your last comment in relation to one mod not listed.. (pvc tubes pictured below). What I set out to do with the tube (1st one tried was a 15" 1.5" pvc plumbed into the brake booster line) was to smooth out the vacuum signal from the MAP sensor in an effort to see cause & effect on mpg's. (currently commuting in this truck while Ram is down for a clutch swap). What I got was a very noticeable SOTP bump in power between ~1000-3000 rpms. After 3k, power fades. After playing with the length of both tubes I ended up settling for 1 15" & 1 9" tube. That was with the original long runner intake. Last weekends '03 manifold swap with shorter runners was (as expected) a good change for the mid range power without sacrificing much if any low end power. Had no CE light w/o the tubes attached with this manifold. Added back the 15" tube by itself and again, nice SOTP bump in power where I like it but this time mid range power is still better than with the long runner IM. When I filled up after a tank w/o the tube, I had stomped on it some getting onto a street (big grin for still not being tuned at this point) and thats when the CE light popped on (again). Then it clicked that something else is going on in #7. (thought it was an injector as I already swapped coils & plugs, now coils & plugs are new & injectors are the 12 hole Denso 704's) Looking at the firing order I now see what your saying about the available air for #7 after #5 fires (seems stupid to have adjacent cylinders fire one after the other)


https://photos.smugmug.com/Dakota/Ai..._061800-XL.jpg

Have stomped on it wit the 15 tube? Did still toss a code?

It tossed code with tube, and thinking about it, should go back to no tube and repeat to see if code comes back now that I know what I know...

Normal daily driving there is no code. Will post up what I get when I know... it would be sad to have to remove it if it is the root cause, it does add a nice bit of power.

Do you have any logs of your Dak?

No logs, I have not had the bandwidth to go get them... heading out on business trip next week and will make it a priority when I get back.

Freezeframe data says it is occurring at 127* CT & 900 or so rpms... I pulled the pvc mod off prior to leaving for this trip, will see how the code does for a couple of weeks. I appears to me that there is a certain condition that pops up where the pending code gets set and then tripped on the next occurance.

An update... it appears the length of the added tube(s) affect the misfire on #7. I went back to no tube and still had the misfire and it appeared more frequently as seen by the freeze frame data.

So now knowing what I know, I had nothing to loose experimenting with tube length and placement. (misfire code with no tube & 15" length off brake booster) What appears to be working significantly better than the 2 previous configurations is the current length of tube (12in) installed off the vacuum port on the IM. Why does 12 off the vacuum port vs 15 off the brake booster port make a difference??? no idea. Power is better with the 15 & 9 off both ports for the way I drive but I'd prefer no CEL on the dash. I have over 300 miles on it in the current state with no CEL/FF data. (truck is a daily driver while the Ram is down)

As it is, power is excellent (but not the best as stated above) with the '03 IM, Airaid intake tube with turning vane, 70mm TB, air deflector under the air filter to remove turbulence at the filter. Pulls nicely up to the shift that occurs past 4k with no CEL and bottom end torque is more than enough for how the truck is used.

Overall night & day compared to stock. Rams clutch is in hand and going in soon which will allow me to get back to the attempted tuning on this truck (1st attempt erased the ECU as it was not supported yet).

@PurpleRam thanks for your input!


Next mod JBA shorties followed by a custom Y pipe followed by a fresh cat & cat back exhaust, one at a time of course.

If I understand what you doing , your adding a tube to a Vacuum port and the other end is just drawing in fresh air .

Quote:

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Originally Posted by rays04gtx

If I understand what you doing , your adding a tube to a Vacuum port and the other end is just drawing in fresh air .

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No the tube is not open on the end, it is sort of like a Helmholtz resonator attached to the port.

ECU is still reporting freeze frame data but no CE code or pending code. Have approx 450 miles now on this configuration.