turbo exhaust housing?

[Chrisw]

My question is, if all other things were to stay the same but a guy was to swap out the hot side of the turbo for the next size up say a 12cm to a 14cm or a 14 to a 16. (boost stays the same at max boost)



1. (unloaded) How much effect will it have on every day fuel MPG with the lower boost at that same load? I have been told that just because boost is down it's still moving the same amount of air ... ok, sure it is ... ... I am seeing 200 degree or more rise in egt at lower rpm. Once the rpm comes up it seem to be the same or better then before, when I have my foot on the floor egt temps seem to be lower by at least 150 degrees.



2. how about towing? is it worth the extra lag and lost of lower rpm torque for extra cooling and more power around 1900 rpm on up? When the turbo becomes more efficent



Truck runs out so much better then before with the new housing it just flat gets it on the interstate. As for a everyday driver I have learned how to dive with the slower spool up. And the new found power is nice on the top end too. I don't feel that it will have a proublem pulling at 70 mph. But I am sure that I can't pull at 55mph in 6th because the turbo doesn't spool very well at 1500 rpm anymore. But I quess that is why dodge made a 5th gear



For the guys out there that have changed the exhaust housing do you ever wish you still had the smaller one back? if so when? Or does the old saying "GO BIG OR GO HOME" apply here



thanks for any help

chris

 

[McCRam]

Bumping this to the top. I have been wondering these same questions.

 

[Forrest Nearing]

boost won't stay the same unless you're wastegated...



go big or go home

 

[JGK]

Chrisw,



In general, the larger exhaust housing is going to flow more exhaust gases at a given RPM, but it won't spin the turbo as fast at that RPM, thus, you'll see lower boost. At lower boost, less air to the engine to burn the fuel, so you may actually see higher EGTs at those lower revs.



On the plus side, at the higher revs, the bigger housing will allow more exhaust flow, thus helping to lower EGTs. Also, the turbo won't be inclinded to boost beyond it's MAP range so quickly. So the bigger housings compromise the low-end boost and EGTs to help with the high-end boost and EGTs.



In a towing rig, you usually aren't towing at the extreme upper rev range, say, 2500 and up, except maybe when in a lower gear and pulling up a hill. Towing is done on the freeway at lower revs. So smaller housings are generally used to give more boost down there and lower EGTs. If you look at PDR's twin setups, towing twins employ smaller exhaust housings to give more boost at lower revs, whereas the racing/play twins use larger housings cuz you're generally running at higher revs.



That's the way I understand it, anyway. I'm no fluid dynamics engineer - but I did stay at a Holiday... . no, I won't do that.



-Jay

 

[Chrisw]

I would have forgot about this thread if it wouldn't have sent me an e-mail



Anyway, I am now running a Killer2B turbo with a 14cm exhaust housing witch should flow about as much as a 16cm from a HX-40. Compressure is a 64mm with a different wheel then most, as of last month I was the 2nd person to get one of the new wheel to try out. So chances are if you are running a Killer2B it's not like mine.



First thing I noticed was spool up is not as good on low end (NO SURPRISE) But once rpm comes up it more then fast enough for me. I am not going to go into a long winded thing about how and what all it effects but I will say, My MPG is down about 2-3 mpg from when I was running the little turbo HTB2. Empty cruse set out on the interstate egt is up about 200-300 on the same road with the same road speed.



I pulled a light load the other day, egt and power is very easly keep in check with the 6 speed by increassing the rpm a little, I don't think I would like it as much with an auto or if I pulled every day on 55 mph roads I would want to beable to use or make more power in the lower rpm range. I don't tow often and almost always it's light compaired to some of the guys on hear.



I have tried a stock turbo, H2E w/17cm hated it, hasiely HX-50 with a 15. 5cm great turbo when WOT but sucked around town. HTB2 with a 12cm, Great turbo, unreal for towing, I was making full boost at 1600 rpm when towing and great MPG first time truck ever got over 20mpg on more then one tank. Just not enough cooling for me when the fuel pedal would get stuck on the floor for some strange reason went to a Killier2B with a 12cm Turbo would surge very badly, put a 14cm exhaust housing on it and that helped but still would surge very badly, End up putting a new cartarge in it with a new wheel on it with the 12cm housing WOW BEST setup every very quick and fast. If I was going to tow I would have keep that set up. I end up switching to a 14cm exhaust housing one day for the fun of it to see what would happen. truck felt great, and droped my egt on top end witch was the real reason I started speeding money in the first place. So I thought I would keep it so I wouldn't have to pull the turbo back off again. Over all this is the best set up for my truck and the way I drive my truck to date. The dyno numbers above was with the old Killer2B cartarge, truck feels much better and is smoother then before.



As a side note I have found that with a load and on a steep missouri hill I can make it surge a little, but I have to try and push a lot of fuel down low in the rpm and it just dosen't feel good went doing it, I can easly tell that I am trying to make it make power were it dosn't want too, and egt start to run way at the same time.



just think of all the thing I wouldn't have learned if I would what just spent money on twins the first time.

 

[DRiddel]

Chrisw I am thinking of doing the same set up but I didn't know what kind numbers it would put up and if was an ok daily driver? By the way do you have any times (1/4) with the set up you have now?



Thanks

 

[Chrisw]

DRiddel, I don't have a clue to what mods you have made to your truck. For my truck and the way I drive it this set up is the best I have ever had. If I would have had less power the HTB2 would have been my first choice do to the unreal spool up time and always having boost when driving. But that turbo just wouldn't cool my EGT enough when my foot was flat on the floor with a fueling box set to max and 200hp injectors (BD6) It just wasn't big enough. I can't stand a truck with lots of turbo lag, and the Killer2B is only a little slow in the upper gears when the rpm is below 1800. It's very driveable even with large injectors I can launch from a stop with very little smoke.



I have never run my dodge on a track but I am sure it would suprise me if I knew just how fast it was. It will hit 90 mph going down the on ramp to the interstate with out much trouble, Last time I was at the drag stip I got beat buy a truck with a lot less HP but it was an auto. I just can't shift it fast enought to keep up with the autos, ever since then I have never been back to the track.

 

[moolie]

how's it going chris i see your issue with the truck trying to make power at low rpm and it doesn't feel right and egt's soar. I have the same exact issue with mine and it's a drag until the transmission downshifts then i figure the rpms go up and everything comes alive any word on the twins setup with this turbo as one of the two yet. Paul told me first of the year, then when i called him again he was saying like early spring. i hope it's able to provide a more all around consistant level of performance for me