Stock Y pipe junction NOT a good design

[m95roadster]

To all who think they have lost low end torque with a properly designed aftermarket cat-back system that includes the "Y" (not a homemade or muffler shop special either), show me the dynos! It doesn't even show the low end of the rpm graph on the dyno run. The dyno runs start at around 3800 rpm!

[gr8titan]

Originally Posted by Ridley

I also know for a fact, that backpressure will never increase HP or torque. It's always in the scavenging, not the backpressure, but the two are not always mutually exclusive. What would be ideal, is to use a servo driven butterfly in the exhaust such as in the yamaha EXUP system found in their hi-po bikes. The key to peak numbers though, will always be having the highest flowing exhaust, you just need to have the cam profiles, and the rest of the system to match.

The common fact you and I have here is that backpressure is DOES NOT increase power. Anything else is just to drive the point further. That is the theory I've always adhered to regardless of who is trying to argue that the Titan needs back-pressure.

And that's exactly what I am trying to say: That one owner's poor dyno result due to Brand X exhaust (with mod a-b-c) does not conclusively mean that the Titans need backpressure for power. For all we know, it could have been a poor combination of mods or lack of complimentary mods. Look at the "other Titan Joes" with catbacks. They didn't all mention the loss of torque. To the contrary, if we look at the larger picture, ALL tuned exhaust system are geared to maximum exhaust scavenging (least amount of BP) and these manufacturers would have gone out of business if backpressure is good. The only difference amongst them is that one is tuned better than the other.

[BRACEYOSELF777]

Originally Posted by dawgs77

A person at another club has proved with dynos that the Titan likes the smaller diameter Y-pipes. Hence JBA and Magnaflow(which uses stock Y) did really well in the Dyno tests.

Banks was not tested however.

Word! I believe the stock Y-pipes were left in reason when Magnaflow did testing on the product...and I know for sure...companies in the market try every option from sounds...to fit...to make sure the final product is beyond the customers expectation. Now if they saw gains from the Y-pipe...in no doubt, they would of included a new Y-pipe in the package but obviously...there wasn't any drastic changes or probably loss of preformance..like lower end torque. Its my opinion on what information I've learned from being on this site. Your the first to claim that the stock Y-pipes are inferior. No offenses...just talking gear head talk.

[Matchgrade]

By going with a better flowing (bigger) Y-pipe you should make more torque, but it will be higher in the powerband (at a higher rpm). This will help with high speed runs or even drag racing (especially with the trans and gears that the Titan has). What will be lost is the higher torque numbers in the lower rpm range. This hurts the guy pulling his 6500 lb. trailer at the 2000 to 2500 rpm range. He will have to rev the engine higher to get to the same towing torque that they used to have with the smaller Y-pipe.
More dramatic changes can be seen when changing size and length of headers and intake runners. Thats when going bigger could not only move the torque curve, but also raise HP at the cost of peak torque numbers.
If you want to go fast, go big. If you want to pull well, stay small.

[mecedesboy]

Originally Posted by Matchgrade

By going with a better flowing (bigger) Y-pipe you should make more torque, but it will be higher in the powerband (at a higher rpm). This will help with high speed runs or even drag racing (especially with the trans and gears that the Titan has). What will be lost is the higher torque numbers in the lower rpm range. This hurts the guy pulling his 6500 lb. trailer at the 2000 to 2500 rpm range. He will have to rev the engine higher to get to the same towing torque that they used to have with the smaller Y-pipe.
More dramatic changes can be seen when changing size and length of headers and intake runners. Thats when going bigger could not only move the torque curve, but also raise HP at the cost of peak torque numbers.
If you want to go fast, go big. If you want to pull well, stay small.

therefore it follows, that most of us are looking for the best of both worlds.
so the first step in achieving this would be to remove the stock Y and replace with a larger diameter.

[gr8titan]

Originally Posted by BRACEYOSELF777

Word! I believe the stock Y-pipes were left in reason when Magnaflow did testing on the product...and I know for sure...companies in the market try every option from sounds...to fit...to make sure the final product is beyond the customers expectation. Now if they saw gains from the Y-pipe...in no doubt, they would of included a new Y-pipe in the package but obviously...there wasn't any drastic changes or probably loss of preformance..like lower end torque. Its my opinion on what information I've learned from being on this site. Your the first to claim that the stock Y-pipes are inferior. No offenses...just talking gear head talk.

He's not the first one.
This topic has been beaten to death more than a year and a half ago by "pioneer modders" who opened up and dissected their exhaust system to show the restrictive Y-pipe and muffler for the other members to evaluate. Here's the TT link as posted earlier by 37L1: www.Titantalk.com/forums/297595-post14.html

[P's Titan]

Originally Posted by gr8titan

He's not the first one.
This topic has been beaten to death more than a year and a half ago by "pioneer modders" who opened up and dissected their exhaust system to show the restrictive Y-pipe and muffler for the other members to evaluate. Here's the TT link as posted earlier by 37L1: www.Titantalk.com/forums/297595-post14.html

a link for the whole thread, not just that single post..

So, Whats Wrong With The Stock Exhaust System?

[Hew G. Wrection]

anyone tried true duals yet?

[Blown330]

Anyone have any timeslips of a direct before and after with just the exaust system changed? Dyno's are tuning tools first and foremost....not something to be trusted as much for hp/tq figures over any period of time. Recent experience has shown that a highly opened up exhaust system can and does shift the torque curve/peak up the RPM range. Namely on a low 10-second street/strip supercharged Mustang coupe. Went from a set of Bassani shorty headers, 2.5" high-flow catalytic x-pipe, and 2.5" Bassani mufflers to a set of custom made Kooks SS 1-7/8" primary longtube headers, 3" Dr. Gas X-pipe, and Spin Tech race mufflers. The car visibly lost power in the 60' and verified on the datalogs. Went from running 10.15 @ 132 to 10.34 @ 130. Changes to the tune did little...the bottom end torque simply isn't there anymore. I know this is an extreme case but it does show that you can loose some bottom end from a free flowing exhaust.

[miketan]

This is exactly what you don't want for a relatively heavy vehicle like the Titan. At 5300+lbs, the Titan needs a significant amount of low-end TQ to get all that mass moving. Increasing HP at the expense of TQ is bad especially on a truck. Until there's a selection of aftermarket cams and other mods for the Endurance V8, this low-end TQ loss problem some people are noticing will continue.

The low-end TQ loss problem is an issue of perception. A larger Y-pipe and catback exhaust may increase total TQ thoughout the rpm range which equates to more peak HP. However, the TQ increase is occuring at a higher RPM than before. The entire TQ curve has now been shifted higher. Exactly what you don't want on a vehicle that's primarily designed to haul and tow things IMO.

[mecedesboy]

Originally Posted by miketan

This is exactly what you don't want for a relatively heavy vehicle like the Titan. At 5300+lbs, the Titan needs a significant amount of low-end TQ to get all that mass moving. Increasing HP at the expense of TQ is bad especially on a truck. Until there's a selection of aftermarket cams and other mods for the Endurance V8, this low-end TQ loss problem some people are noticing will continue.

The low-end TQ loss problem is an issue of perception. A larger Y-pipe and catback exhaust may increase total TQ thoughout the rpm range which equates to more peak HP. However, the TQ increase is occuring at a higher RPM than before. The entire TQ curve has now been shifted higher. Exactly what you don't want on a vehicle that's primarily designed to haul and tow things IMO.

IMO i want the biggest baddest monsta of a motar in my truck!!

[Armada]

Originally Posted by miketan

This is exactly what you don't want for a relatively heavy vehicle like the Titan. At 5300+lbs, the Titan needs a significant amount of low-end TQ to get all that mass moving. Increasing HP at the expense of TQ is bad especially on a truck. Until there's a selection of aftermarket cams and other mods for the Endurance V8, this low-end TQ loss problem some people are noticing will continue.

The low-end TQ loss problem is an issue of perception. A larger Y-pipe and catback exhaust may increase total TQ thoughout the rpm range which equates to more peak HP. However, the TQ increase is occuring at a higher RPM than before. The entire TQ curve has now been shifted higher. Exactly what you don't want on a vehicle that's primarily designed to haul and tow things IMO.

I agree. I tow an 8,000 lb. trailer pretty regularly and need the torque down low. I have a completely stock exhaust. Here are a couple G-Tech charts showing what the stock exhaust is capable of doing. I do not suggest these numbers to be absolutes, but they are very close, and there are posted time slips and a video of another completely stock Armada running 14.9's, almost identical to these values.

The horsepower and torque values do have to be considered somewhat differently from those generated by a chassis dyno. G-Tech measures those values out on the road, taking into consideration wind, aerodynamics and drag, so the numbers are influenced by our very brick-like profile and that should be considered. A chassis dyno meets no wind or aerodynamic resistance or drag from the rolling resistance of the front tires, etc.

Please note how our torque curve does favor the low end. But it is smooth and not peaky. The horsepower v. time chart is interesting in that it graphically shows just how poor the aerodynamics of our tricks are and how this cuts into effective horsepower as speed increases.

Finally, I did these runs back-to-back from opposite directions to eliminate any issues of whether the road was level or whether the wind was a factor.

I'm sticking with the factory exhaust for now. I need the torque (awesome tow rig) and am very happy with the performance when the trailer is not behind me.

Now that the truck is well broken in and cool weather is on the horison, I think I'll make some new comparison runs and perhaps take it to the strip in Mobile to see how the data correlates.

[m95roadster]

Originally Posted by Blown330

Anyone have any timeslips of a direct before and after with just the exaust system changed? Dyno's are tuning tools first and foremost....not something to be trusted as much for hp/tq figures over any period of time. Recent experience has shown that a highly opened up exhaust system can and does shift the torque curve/peak up the RPM range. Namely on a low 10-second street/strip supercharged Mustang coupe. Went from a set of Bassani shorty headers, 2.5" high-flow catalytic x-pipe, and 2.5" Bassani mufflers to a set of custom made Kooks SS 1-7/8" primary longtube headers, 3" Dr. Gas X-pipe, and Spin Tech race mufflers. The car visibly lost power in the 60' and verified on the datalogs. Went from running 10.15 @ 132 to 10.34 @ 130. Changes to the tune did little...the bottom end torque simply isn't there anymore. I know this is an extreme case but it does show that you can loose some bottom end from a free flowing exhaust.

Sure, the curve will shift upwards with a set of agressive headers. However, we're tallking cat-back systems here. Like I said in a previous post, anything after the cats will not shift the curve, but will usually increase hp/tq across the whole range on a restrictive OEM system.

FYI, the_head decreased his times by a 10th in the quarter with the Banks system which uses a huge 3" "Y" pipe.

[m95roadster]

Originally Posted by miketan

The low-end TQ loss problem is an issue of perception. A larger Y-pipe and catback exhaust may increase total TQ thoughout the rpm range which equates to more peak HP. However, the TQ increase is occuring at a higher RPM than before. The entire TQ curve has now been shifted higher. Exactly what you don't want on a vehicle that's primarily designed to haul and tow things IMO.

You're right it is perception. However, I don't agree about the TQ curve shifting higher. There is an increase across the board. If you can, show me data proving this.

[Blown330]

Originally Posted by m95roadster

Sure, the curve will shift upwards with a set of agressive headers. However, we're tallking cat-back systems here. Like I said in a previous post, anything after the cats will not shift the curve, but will usually increase hp/tq across the whole range on a restrictive OEM system.

FYI, the_head decreased his times by a 10th in the quarter with the Banks system which uses a huge 3" "Y" pipe.

Agreed...my point point was more towards adressing the "myth" of backpressure as a whole. I'm sure that a well designed cat back system of proper tuned length can affect an increase such as you've stated. Those who think they can run solid 3" pipes that dump just behind the transmission with nothing but bullet mufflers are going to be in for a sorry surprise though.