Engine/Transmission (1998.5 - 2002) 4" Exhaust With Stock Turbo

[WWalters]

Last year I replaced the stock muffler and resonator on my truck and replaced it with a Walker 21468 low restriction muffler. Other than this modification the truck is stock. I've been thinking about going to a 4" exhaust set up from turbo to tail. The truck has the HY-35 turbo so the outlet to the down pipe is close to 3". Before I spend the money I had a few questions that you guys can help me with:



1) Do you think the EGT's would be higher with the smaller turbo or would the 4" lower EGT's?



2) Obviously the truck would breathe better so I would expect some performance improvement. Right?



3) Should I just wait until I can afford an HX-40 and save the cost of a new down pipe?



I would appreciate any suggestions.

 

[LSMITH]

1, yes. a little bit. Do you need EGT reductions? How much reduction?



2, nope, nada none. Unless HEAVILY modified the gain is very slight.



3, depends really, where are you going to end up for HP? How are you going to make that HP? If you make 350 or less with injectors and timing there is no reason for a 40, if you make 300 or more with a wire tap the 40 is going to have a hard time taming EGT.

 

[RustyJC]

1. Unless backpressure increased with the 4" system compared to what you have now (not likely), EGT's should not increase. If backpressure drop with the 4" system, EGT's should drop as well.



2. You'll probably hear it more than you'll feel it. The only real performance increase would be due to a reduction in backpressure that would lead to lower exhaust pumping losses. This would be extremely minor.



3. Your call. If you elect to go with the 4" system now, as you state you should only have to change the downpipe when you go to the HX-40.



I went to the 4" exhaust system primarily to help with EGT's. Our ETH/DEE was reaching 1300 degF pre-turbo when towing our 5th wheel. The 4" exhaust system was installed on the same weekend as an Edge EZ (with boost elbow), so I can't say how much difference each item made, but the main contributor to our EGT reduction (1100 degF after the changes) was the boost elbow - boost increased from around 20 psig to 30 psig.



Most people buy the 4" exhaust systems for the sound and looks - for a stock or near-stock engine, you really can't justify the cost based on any measurable performance increases, IMHO.



Rusty

 

[WWalters]

Thanks LS Smith and Rusty JC for the replies. I should have mentioned that I don't pull anything with my truck or haven't up to this point. The truck is used for driving back & forth to work ( in stop & go traffic I might add) and for pleasure.



I asked about the EGT's because I had read in a thread on this site that someone did experience an increase in EGT's when going to a 4" system with the stock turbo. I don't remember all the details though.



My truck has around 20k on it, at some point in the future I do plan to start bombing; I guess the 4" would just be the first step.

 

[JPLB22]

WWalters



My truck is basicly identical to yours. Except I'm 4x4 and SLT. And you only have about 1500 more miles than me. The first and only BOMB I've done so far is a 4" turbo back exhaust. What RustyJC said about hearing it more than you feel it is absolutely true. I noticed no performance gain whatsoever, but the sound is GREAT. I am also planning on more BOMBs too, I am just trying to get as many of the "for protection" BOMBs out of the way as possible.

 

[pwr2tow]

To performance gains there was a very good article written by Ted Jannety, and yes there is a performance gain. Do a search under Teds name and you should come up with it.



The increase in performance is very hard to detect, for example; When I replaced my stock injectors with stage I injectors I thought I had wasted my money, couldn't feel the difference. Yet when I did my zero to 60 time test it showed a 2 second decrease in time. Then I had it dynoed and there was a 60 HP increase over stock. With these big trucks and as much as they weigh it is hard to tell by the seat of the pants test if there is any gain.



Ron

 

[JPLB22]

ronsram1999



I did seem to notice that the truck did run up a long steep canyon (just dry, no pulling) a little better sometime after the exhaust was put on. But my truck only has 18,500 miles, so I don't know how much to attribute to break in or if there was a power improvement from the addition of 4" exhaust. I have not dynoed yet or done any track time. The dynoes in my area always seem to be taken up by rice burners . I figure I will wait for more BOMBs to go to the track.

 

[WWalters]

Thanks Ronsram1999 for the tip. According to Ted Jannetty and his " Proper Order for Upgrading ISB Engines", the stock exhaust pipe size of 3 inches can support 200-250hp and this is with mandrel bent tubing. My 2002 is rated at 235hp I believe. This doesn't give much room for any kind of performance upgrade.



Looks like I will be upgrading to the 4" system since even a stock Dodge CTD will benefit. Thanks everyone for their reponses.

 

[SnoKing]

I thought Ted said stock is good to 350HP. SNOKING

 

[rweis]

I am in the same boat, 2002 HY35 no bombs, yet.



As far as I can tell is you bomb the air first, its gotta breathe.



Then the transmission so you don't burn the stocker up and CAN put in updates.



Then the fuel last.



Rightly or wrongly I am doing a Scotty II for input and a 4" for output. Will not make much difference to a stocker though and I know that.



Then a larger turbine and that should finish the air.



Then update the transmission to hold the fuel bombs and ought to feel a little difference there.



Then the fuel and box bombs where the REAL hp differences are.



One persons opinion,



Bob Weis

 

[LSMITH]

I hope you guys have the extra money laying around to spend it on intake and exhuast mods that you don't need. The intake is good for well over 300 RWHP bone stock, as is the exhuast. Straight pipe it and the exhuast is good for 375. Go back and read the testing done by Joe Donnelly on a DYNO under the SAME conditions, not rely on seat of the pants feelings or stopwatch testing on different days and conditions.



I have done the intake and exhuast on my truck and it was a total waste of money, unless you want to pay for the sound... . I am around 350RWHP.

 

[Hohn]

LSMITH:



I totally agree. That's why I am STRONGLY considering stopping my bombs at the 350rwhp point. I think I should be pretty close to that with my EZ and dd2s.



My thinking is that the marine ISBs can hit 370 (though I am sure they aren't the same as our engines), so I am not exceeded design specs as much as the 450hp and up guys.



I also think the 350rwhp point is the point of diminishing returns. Since I am making my power with injectors, I can keep fairly cool.



By stopping at 350hp, I have these advantages:

- no need to replace turbo

- no need for exhaust upgrades (no chance of "drone")

- No need for Scotty or other intake that creates a deafening whine

- I can baby it enough to keep the stock clutch alive for a little while



So, to get the the 350HP level (assuming ~230 stock HO), I spent around a grand between EZ and injectors. That comes out to about $8. 30 per added horse.

If I go to the 400hp level, I need a PDR40 ($900?), exhaust ($400), intake ($200), a wire tap box ($150 more than EZ) and clutch ($900). This adds up to $15 per added horse.



On a per-hp basis, going over 350 can cost you DOUBLE. True, I will probably need a clutch anyway @350rwhp, but you can see that this alone isn't enough to change the economics.



Never mind the economics of SERIOUS bombs (twins, modified pump, Mitchell Clutch, etc. )



HOHN

 

[Huff N Puff]

Get an HX40

By the way I have one,I took it off to repl. it with a pair of twins. I t was an exellent turbo the truck ran in the mid to lower 13s consitantly it has less than 2000 miles on it, it includes a 4in down pipe I'd like 750. 00$ for the both. Merv