Question for those who tow with twins

[PC12Driver]

For my day to day driving with some occasional, um, "test" runs, my Dodgezilla hybrid with the wastegated 14cm housing works great. But I was kinda disappointed with the towing performance. On slight to moderate hills with the trailer in tow (10k 5ver) I'd hit 1200 deg egt before I'd see boost in the high twentys. More throttle would get more boost, but the temps would jump into the danger zone, and I really don't want to accelerate. Downshifting and getting the RPMs above 2000 would get the boost up and the egts down, but I'd be doing more shifting than what I needed to do over the same grades than I did back with only an EZ and the stock turbo. And now that my head is currently getting fire-ringed and will be re-assembled with studs after my blown head gasket, I'm looking into the twins thing a little harder.



So, for those of you that tow with twins, how are they? I don't think I would want anything bigger than a 35 for the top turbo, since I'm mainly concerned about the low to mid range performance. But would I experience the same deadband in the lower RPMs (below 2000) like I do with my DZ/14? I've read that twins will spool slower than the small turbo by itself, but is that referencing time in seconds or does that mean that it lights off later in the RPM's? With my engine all apart and the new rings/studs I'm thinking now would be the time to do it, but I want to make sure that I don't end up making my problem worse. Any insights?



BTW, anyone try the BD twins? The price seems right but I don't see much about them.

 

[bmoeller]

Might want to send a PM to propuller.



He tows with his twins. He has alot more power though, so it won't be quite an apples to apples comparison.



The BD twins, I think, are still fairly new.

 

[ROADWARRIOR]

My truck and trailer totaled around 16k on my vacation last fall. At the time, I was running Hot Mach 3's and I never had any problem getting high temps. The highest I saw was around 1050 at 40psi in 5th gear up the biggest hills I came across in North East MI. My boost starts coming on around 1200rpm. I don't have any of the under 2k rpm problems you explain. I am also running a Scheid street cam. My set up has been awesome for towing. This was with the Comp box off.



Dan

 

[RonA]

Odd that you are not seeing an improvement over your stock turbo with the DZ/14. I ran my top turbo as a single for a while before twins and it worked very well for towing. Small twins work very well for towing. But the DZ you have should not be dead below 2000 rpm.

 

[Mark_Kendrick]

For my day to day driving with some occasional, um, "test" runs, my Dodgezilla hybrid with the wastegated 14cm housing works great. But I was kinda disappointed with the towing performance. On slight to moderate hills with the trailer in tow (10k 5ver) I'd hit 1200 deg egt before I'd see boost in the high twentys. More throttle would get more boost, but the temps would jump into the danger zone, and I really don't want to accelerate. Downshifting and getting the RPMs above 2000 would get the boost up and the egts down, but I'd be doing more shifting than what I needed to do over the same grades than I did back with only an EZ and the stock turbo. And now that my head is currently getting fire-ringed and will be re-assembled with studs after my blown head gasket, I'm looking into the twins thing a little harder.



So, for those of you that tow with twins, how are they? I don't think I would want anything bigger than a 35 for the top turbo, since I'm mainly concerned about the low to mid range performance. But would I experience the same deadband in the lower RPMs (below 2000) like I do with my DZ/14? I've read that twins will spool slower than the small turbo by itself, but is that referencing time in seconds or does that mean that it lights off later in the RPM's? With my engine all apart and the new rings/studs I'm thinking now would be the time to do it, but I want to make sure that I don't end up making my problem worse. Any insights?



BTW, anyone try the BD twins? The price seems right but I don't see much about them.

My 3500 is basically like yours and I have towed at over 27000# gcw and not seen the high side of 1325 preturbo. Uphill in 6th at 82mph on the cruise control .



I was running 200hp honed injectors and an EZ (FMS was off for towing) . I ran a HX35-12 and an HT3B.



The kits I build now use the B2 instead of a 3B. It gives better spoolup, more overall power, and it's physically shorter so the fit is easier.



Later,

Mark

 

[PC12Driver]

Ron, I wouldn't say it was completely dead (I could still get 20-something psi), but I did feel that I was "under" the turbo. If I hit the hills at 60-65 I'd have to back off and/or downshift. Hitting similar or larger grades at 70-75would put the rpms near 2k and the boost into the 30's and I'd feel "on" the turbo, and temps wouldn't be as much of an issue. The problem was compounded with altitude.



Now this is the part that I'm trying to wrap my brain around and I think you have the perfect scenereo to help me with it: when you put the second turbo inline with the DZ/14, does that increase the low RPM boost or does the bottom turbo add drag and make it worse?

 

[Mark_Kendrick]

Ron, I wouldn't say it was completely dead (I could still get 20-something psi), but I did feel that I was "under" the turbo. If I hit the hills at 60-65 I'd have to back off and/or downshift. Hitting similar or larger grades at 70-75would put the rpms near 2k and the boost into the 30's and I'd feel "on" the turbo, and temps wouldn't be as much of an issue. The problem was compounded with altitude.



Now this is the part that I'm trying to wrap my brain around and I think you have the perfect scenereo to help me with it: when you put the second turbo inline with the DZ/14, does that increase the low RPM boost or does the bottom turbo add drag and make it worse?

It's going to make it worse. I suggest you change to a 12cm housing to increase the bottom end performance.



Your 24v doesn't have the low end of Ron's p-pumped 1st Gen. I don't like the way larger exhaust housings behave on a vp44 equipped truck.



A set of twins is ALWAYS slighly slower than the smallest turbo in the set. It's due to the fact that there's a big turbo upstram on the compressor side and downstream on the turbine side. The change is minor but measurable.

 

[PC12Driver]

Ida thunk the 12cm housing with twins would be to small. I'm guesssing that would require a fairly high flowing external wastegate, eh? So then for faster spoolup would I keep the DZ or go with my smaller factory 35 (less rotating mass)?



How many psi's are you running your setups at?

 

[RHARVEY]

This may be a wrong statement or a stupid answer. My understanding is that the ECM keeps the fuel limited on the bottom end. Somewhere around the towing rpms but starts to open it up on the top end. The problem is that in the lower rpms. . you are not running enough fuel to spool that turbo. By the time you give it more go juice the egts come up and it hard to pull back up to make up the mph.

What a friend of mine did was replace his stock ECM with the MAD ECM which opened up the fuel flood gates right off idle. He said instead of feeling all the power on the top end ... it starts right off idle. He said that the boost is up right then!



Rick

 

[RonA]

I was wrong. I went out to the hardware store earlier and watched my pyro lugging along on a steep grade. At about 55 to 60 the egt runs a little higher. If i had a trailer on behind it would be alot worse. I don't notice hills anymore when I'm empty, with twins the egt doesn't become an issue empty unless you are being crazy. Talk to Mark about the 12cm housing and twins. He builds them all the time.

 

[PC12Driver]

Yeah, I know I can crank the Comp's responsiveness and get the bottom end back, but I'd like to keep the smoke down a bit. I guess I may be wanting to much...



I think you're right Ron. Sounds like Mark is building about what I need.

 

[Mark_Kendrick]

Ida thunk the 12cm housing with twins would be to small. I'm guesssing that would require a fairly high flowing external wastegate, eh? So then for faster spoolup would I keep the DZ or go with my smaller factory 35 (less rotating mass)?



How many psi's are you running your setups at?

I run a minimum of a 32mm wastegate It is possible to set the gate to make less boost with the twins than was made with the single. . it would be sorta pointless though



I have cutomers that make well over 600hp(~640 actually) on 24Vs using 12 and 14cm housings.

 

[PC12Driver]

And the wastegated exhaust is dumped into the drive of the second turbo?

 

[Mark_Kendrick]

Yes. It's dumped properly

here are some better pics...

http://www.kendrickdiesel.com/Compounds.htm

http://www.kendrickdiesel.com/hx35_b2_With_exchanger/

 

[patcarman]

mark i was curious if i could talk to u about using my stock turbo in a twin setup,i think i talked to u before and u said it was possible, thanks for the reply kelley

 

[Mark_Kendrick]

mark i was curious if i could talk to u about using my stock turbo in a twin setup,i think i talked to u before and u said it was possible, thanks for the reply kelley

Feel free to call... 817 343 8666.



The stock turbo (HY9) can be used to ~550 hp. If you have the 35/12 it's good to around 600 maybe a little more.



Lately I use B2 instead of 3Bs so the autos can keep their heat exchanger.



It's a tight fit.



thanks,

Mark

 

[RonA]

Mark.

How much louder is the whine from the B2 compared to the 3b. 25%, 50%?The 3b is plenty loud enough for me, but I know some want jet engine scream.