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Luke
Dodge Dakota
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5/13/2006
11:59:14
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 Subject: Y-pipe problems
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There is no connection between the passenger side exhaust manifold, and the Y-pipe on that side. The flanges that the bolts go through are separated because the bolt slid out of the holes. I was wondering if anyone else encountered this. Not a big problem, although it is losing back pressure and sounds bad. I was curious as to how anyone else solved the problem, such as by dealership or DIY. Thanks for any input.
1998 R/C 318ci. Cat-back no mufflers.
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Obio3
Dodge Dakota
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5/13/2006
18:31:01
| RE: Y-pipe problems
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If you really feel the need for back pressure, you need to consider this. When you modify your intake for better breathing, them maybe do a couple of little mods to take advantake of this extra intake air, What is the reason to install headers and a better flowing muffler and duel or bigger exhaust pipes so the extra air coming in can get out creating HP. On a stock V8 engine, right in front of the converter, this being the place of highest back pressure,if you was to install a valve that you can read the pressure at this point your highest reading will be 2 lbs. 3 tops . this is with engine reved high. Now if you discover more pressure then this you have a serious problem that if not corrected will burn valves at a rate connected to the amount of pressure you discover.4 stroke engines do not want or like back pressure. Your always going to have a little and 2 to 3 pounds amounts to nothing. I'd truely like to hear someone that has positive researched information stating you need back pressure to produce HP or torque on a 4 stroke.Everything you read or see on tv shows reduced back pressure Any pressure needed (quinch) is controlled by the valves in the cylender. When that exhaust valve opens it is trying to get rid of the spent air so a new full charge can enter. Back pressure slows this process leaving some in the cylender and not allowing a full new charge. HP goes down period.
So many problems .... So little time
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cuzindoug
GenIII
5/14/2006
10:44:09
| RE: Y-pipe problems
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This was no scientific test, but when I put was contemplating a new exhaust for my truck, I tried the straight pipe, it was loud as hell (sound cool), and my truck idled like a raped three legged dog, and ran down the road even worse. With the stock exhaust, it idled perfectly, but throttle response and over-all acceleration was kind of sluggish. I settled for a high flow cat and a single in single out 40 series flowmaster. It idled a little rougher than stock, but the throttle response was good and acceleration was even better. I don't know if this is because of the 3.9 imbalance due to the "missing" pistons/rods on the crank that need a little back pressure to even out the rough idle, or I just didn't let the computer learn the new air flow, but I could definetly feel the deferences between the 3 setups. Just my .02.
If it doesn't fit, you're using the wrong hammer!
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Kowalski
GenIII
5/15/2006
15:19:57
|  RE: Y-pipe problems
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Just because there is a difference, it doesn't mean it is due to back pressure. Exhausts can be tuned so that the exiting charge will have a certain velocity to scavenge the cylinder of spent gas, and to start pulling the new charge through. Compromises are made at some rpm's. The best way to look at this, is what is needed for efficient scavaging; rather than thinking of it as back pressure.
Lead, follow, or get out of the way
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Luke
Dodge Dakota
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5/15/2006
18:19:07
| RE: Y-pipe problems
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Let me refrase that. I have an exhaust leak + Dual exhaust / no mufflers. Will there be a long term effect on my truck with the low backpressure.
And I was wondering if anyone else had their y-pipe pull away from their exhaust manifold to create a gap in between.
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Norm
Dodge Dakota
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5/15/2006
20:49:22
| RE: Y-pipe problems
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"Will there be a long term effect on my truck with the low backpressure."
The most "back pressure" you have is the piston trying to push the exhaust gases out of the cylinder around the exhaust valve.
Your engine will be just fine if you consider the previous posts and think exhaust velocity instead of that other thing.
Also, if you have the standard firing order (1-8-4-3-6-5-7-2), then you can forget about a 'tuned exhaust', because the left cyliders are not firing alternately with the right cylinders. Because of manifold shape, most of the conflict on the 4.7L is cylinders 5 and 7. 5 is still dumping into the manifold when 7 starts to do the same. That's why most v-8 engines with modified exhaust sound like they need a tune-up.
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ramewe
Dodge Dakota
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5/17/2006
00:48:01
| RE: Y-pipe problems
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i dont play on line to much and im not allways right but i can say that try what you think will work if it dosent than keep trying than you will learn to do all. all i can say is fix your leak or install headers true duals (NO CATS)with good flowing mufflers that you like (and not cause they sound good) and rig a pump to suck out your crank case, so it to can breath better and you will feel a gain in HP.
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Huggins
Dodge Dakota
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5/18/2006
22:08:33
|  RE: Y-pipe problems
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Look, these engines aren't jet engines!!! What everyone on here is forgetting is that these engines are OBD2 emmission vehicles... What's going to happen with the exhaust leak at the header flange to y-pipe connection is that air is going to be drawn into the exhaust system and cause the o2's to read lean, causing the fuel mixture to steadily go richer and richer until it is at it limits and set the check engine light... Also the rich fuel mixture will wash the oil off of the cylinder walls causing them to glaze over resulting in oil burn and eventual engine rebuild... Not to mention the fact that you will have raw gas down in the engine oil...
Exhaust system depend on pulses to make power and torque, which is why only extremely high rpm engines will dump the exhaust straight out into the atmosphere... Heck if Nascar regulations weren't so tight and strict, they'de run all kinds of extremely long header setups... Right now they all pretty well stick to around the 32" per cylinder mark... I know some people running 6' long primary tubes and making more power in the 8 to 9000 rpm range on little honda engines...
If you seem to have this problem a lot then have someone weld some washers onto the flanges so instead of a slot you now have a hole to stick the bolt through and use some regular washers combined with some lock washers on the bolts and make sure that they are very tight when you tighten them... You will need to go back and tighten them one more time about a week later due to heat allowing the bolts to stretch not to mention the flange itself to kinda bend around a little more...
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Obio3
Dodge Dakota
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5/19/2006
02:00:06
| RE: Y-pipe problems
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Nice post huggins..... The most important thing to remember when you deside to change your exhaust is the amount of pressurs I mentioned . 2 pounds is right on and 3 pounds is max reved high. The cross over pipe is there to lower LONG DISTANCE pressure. Very important part of the exhaust unless you go with bigger pipes for true duels. You really need to do the homework to get the size correct
So many problems .... So little time
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Obio3
Dodge Dakota
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5/19/2006
10:56:42
| RE: Y-pipe problems
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Sorry. When I said the crossover pipe I was refering to factory duels being converted to after market true duels.
So many problems .... So little time
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Luke
Dodge Dakota
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5/19/2006
11:41:19
| RE: Y-pipe problems
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Thank you for the responses. I will get the problem
checked out as soon as i can.
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Lurkin
Dodge Dakota
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5/22/2006
10:45:27
| RE: Y-pipe problems
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Good post Huggins, but make sure that everyone understands that your statements are only valid if the exhaust leak is before the O2 sensor.
I'm not sure on the 98, but most of the Gen 3's have the O2 sensors upstream from the Y-pipe.
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Huggins
Dodge Dakota
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5/22/2006
15:07:06
| RE: Y-pipe problems
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Yes I guess I did leave that one out... 97 - 99 dakotas had two O2's as far as I know of "one just before the cat and one just after the cat"... These were after the y-pipe... However exhaust leaks will still hurt hp and torque anywhere in the system due to the fact that air is drawn in and taking up space in the exhaust system "creating back pressure"... Yes exhaust is still blown out at idle and lower rpms, but once exhaust speed or movement through the pipes starts getting higher, air will be drawn in, not blown out... This only applies to leaks, not striaght out dumps such as the end of the tail pipe...
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Luke
Dodge Dakota
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5/22/2006
17:28:39
| RE: Y-pipe problems
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the leak is well before the cat. i dont believe i have 2 sensors. I have a custom set up. But good thinking.
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Huggins
Dodge Dakota
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5/22/2006
22:45:47
| RE: Y-pipe problems
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Luke as long as your truck still is passing emmissions, you are required to have both O2's in place and working, mainly one before and after the catelytic converter... This of course is dependant souly on the area in which you live... Also like Lurkin stated as long as the leak is in front of or rather before the O2's, it will cause the previously stated issues...
You know vehicles are allready required to control ignition systems and fuel control individually per cylinder via coil on plug and indepently controlled fuel injectors, that it really won't be that much longer before you will start seeing O2 sensors per cylinder to control the fuel mixtures individually... I think a lot of people out there have forseen this coming, but I guess it's just a matter of time before it actually happens...
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