Engine/Transmission (1998.5 - 2002) 99 Auto - want to go Mach 4s + htb2/12 or 14?

[Joe Mc]

Want more power - yep sliding the slippery slope. I can get a great deal on trading my 1. 6 sticks up to new 4s, and a new htb2/12 or 14 with downpipe. Presently with my stock turbo, comp tapped and 1. 6s I can see spikes to 1500* quickly with comp turned to 4-3 and up.



I know this (4s and htb/2 deal) seems like a no brainer. I just have a few questions. For those willing to reply please speak from first hand experience with a 99 ISB 215 auto - (also see sig). What is the difference between the htb2/12 and the 14 - the housings are a different size - but does one spool quicker in the low rpms than the other? does one provide more of an egt reduction than the other? Which would work best with my setup? Oh, I never tow - most load I've ever had in the bed is 1500# - mainly used as my daily driver, occasional light utility and constant loads of fun



Mainly wondering what's the diff between the 12 Vs. 14. Looking to increase fun factor and reduce egts. Appreciate your comments.

 

[LOtero]

this is an answer i got from a fellow TDR member on the same subject, very helpful.



I'm really liking my HTB2. The power comes on smoothly down low and keeps pulling on top. My old Dodgezilla felt smooth on the bottom, but that's because it didn't light off until I built some rpms. The HTB2 just smoothly starts building boost starting about 1,500 rpm. It has also cleaned up quite a bit of smoke.



As far as temps, I have yet to break 1300* with the box on 5x5 and my Mach2 (100hp) injectors (for reference, that's about 100* cooler than the DZ/14). In my daily driving mode (Comp on 3x3, about 400hp) I can barely touch 1100*. And that's with the wastegate still set at 33-35psi (the turbo is good for about 45 psi, so I have room to grow). Keep in mind, I do have a cam, and that will knock 50-100* off a non-cammed truck.



I'm a big fan of smaller exhaust housings. The only place a 14cm housing is an advantage is on the top end. Everywhere else the 12cm housing has the advantage as far as spooling and lower egts. And as my egts prove, at 460hp the 12cm housing is not a limiting factor at all. The wastegates on these things are HUGE and will have no problem managing boost/drive pressure on high HP trucks. And especially since you have big tires and a tight auto, I'd really lean towards the 12cm housing.



So don't fall for the bigger is better attitude that seems to be popular here on the TDR. Yes, the 14cm housing may make things cooler on the top end at full throttle (not always the case; I know a fellow with a HTBG that dropped from a 14cm to a 12cm and actually had slightly lower egts), but the 12cm will run cooler and get more boost sooner into the engine, which means the power comes on quicker. I guess it comes down to what you plan on doing with your truck.



Quality wise, the HTT makes the old Holsets look like toys. The machining is so much cleaner on the HTTs and they just look so much better thought out. I'm pretty sure this is the last turbo I'll have on my truck. It does everything I need it to with very little compromise on the bottom end (every larger turbo will loose some bottom end, it's just a matter of to what degree). Aside from losing my turbo mounted exhaust brake, everything else has been positive about the HTB2/12.

 

[Joe Mc]

LOtero - thanks. Anyone else out there?

 

[rivercat]

yep on the auto go with the 12

 

[PC12Driver]

Thanks LOtero, I didn't want to type that over again!

 

[paulb]

I love my HTT 62/14 (and the S400 below it :-laf ). I agree with what everyone has said, but I thought I would add a little. The two things that the 14cm will do over the 12cm is, one spool slightly slower ( probably not much at your altitude), and two it will reduce drive pressure. My suggest would be that if you are looking for stop light to stop light performance, go with the 12cm. If you plan on going drag racing go with the 14cm. If you have a drag comp you will be able to peg the pyro with either housing, in the 1/4 mile. The difference will be how much drive pressure it takes to get there.



Oh, yeah... The 62/14 makes a great top turbo in a set of twins! Oo.



Paul

 

[Joe Mc]

Great thanks. Now allow me to show why this (TDR) site is such a great place to share and learn . . . What'd ya mean "drive pressure"

 

[paulb]

Great thanks. Now allow me to show why this (TDR) site is such a great place to share and learn . . . What'd ya mean "drive pressure"

The pressure in the exhaust manifold, that drives the turbo(s). Often called back pressure. The lower amount of drive pressure (breaths better), that will produce a higher amount of boost, at any given power level, will produce more hp. This is a big generalization, but for the most part true. Unfortunately we don't operate at just one power level or RPM, so sacrifices must be made...



Paul

 

[Joe Mc]

Ah, OK makes sense now - different but the same as back pressure kinda sorta. Thanks.