Out of Air

[JStraw]

Hi all, I just made a 750 mile (empty) trip with my newly installed 14cm2 housing. Lower speeds were great but on the open interstate, the 18cm2 would pull the truck to over 110mph where-as the 14cm2 ran out of steam (seemed restricted) at 85mph floored. Is this a commomality with going to the 14cm2.



I'm not pleased with the lack of umph at interstate speed if this loss of top end is caused by the 14cm2. It ran like a stripped ape with the 18cm2. Only good news was that I got over 20mpg on the trip.

 

[formula]

That's one reason I switched back to my 18. 5 housing. The 14 makes for better driveability on low to midrange, but the power is in the bigger housing. Your performance loss does seem a bit severe though. Did you change anything else when you swapped housings?



Sean

 

[glhs]

Is your 14cm housing wastegated or non wastegated? What was your max boost before and after the install? I agree with Sean; that sounds pretty severe for just one change. Kurt

 

[JStraw]

O. K. , I'll have to do another run with the 14cm2 to give it a fair shake. Found out my transmission needed the kick down cable adjusted and afterwards she ran like before with the 18cm2. what an oddity

 

[R.E. Miller]

Had similar things happen since I went with the 12cm housing. To do 80-85, you really have to floor the thing compared to before. Did find that the egt's were better controlled during towing, but I am not really all that fueled up either. I want to go with a 16cm housing, the initial delay is worth the kick in the pants that you get once it is spooled. Plus I think that with modest fueling changes, the delay will become absent.



Russell

 

[BushWakr - RIP]

General rule of thumb:



Each size you go DOWN in housing size provides better bottom end response and about 2-3psi more boost. It also looses at the top end of the RPM/MPH levels. The inlet to the smaller housing becomes too restrictive and causes backpressure or "high drive pressure" which in turn contibutes to higher EGT's, and poorer airflow at the top.



Reversing the process subtracts 2-3psi boost, slows the responsiveness a bit at the bottom end, and adds better air supply at the top end, and less backpressure/drive pressures at the top.

The way to have your cake and eat it too... ... . use a modified turbo like the HX35 with a 16 housing. The mods to the turbo compensate for responsiveness losses, and results in a much better all around system. I'm testing this right now, in conjunction with the governor spring.





bob.