I installed my wicked wheel about 2 months ago and was impressed with the results IE quicker spool up and reduction in stall/ surge. Having said that, my Buddy who has a 03 cummins HO just today got his guages and 100 h/p Edge Module. He let me drive his truck and I noticed that his turbo spools up quite considerabley faster than mine. I have the diablo predator 100 hp 4" turbo back exhaust, open air intake and wicked wheel. Not only faster but considerably higher as well. It was nothing to get 27+ lb of boost with 3/4 throttle. Since its not my truck I did not push it any further than that. What is the deal?? his stock turbo and wheel should not spool faster than my stock turbo with my after marked wheel, should It. If so, I may be looking into holsett for my next turbo!! By the way, I noticed no surge or stall on his truck whatsoever with the factory turbo and wheel..

 

Since I own a Dodge/Cummins I'll take a stab at this. The Cummins 5.9L 6cyl ISB that comes in the Dodge trucks came with one of two Holset turbos.

On trucks that have auto trannies, it has the Holset HY35.
On trucks that have stick shifts, they have the Holset HX35

The only difference is that on the HY35 has a 12cm exhuast housing as opposed to the HX35's 14 cm exhaust housing.

Both turbos are good to 35 psi of boost. After 35 psi you start to really heat up the air and you risk overspeeding the turbo. Both have a 4 inch air inlet. In thier stock form, they are wastegated to either 22 or 25 psi.

The best thing is these turbos can really whistle good. I love the sound it makes.

 

One more thing I wanted to add. The turbo on the Cummins is bolted directly to the exhaust manifold. The exhaust gas doesn't have to travel as far to get to the turbo. That is probably why they spool up faster.

 

Dumb question but does it have anything to do with the higher rpm of the 6 vs V8?

 

No. The 7.3L Powerstroke and the 5.9L Cummins have the same RPM range. Both redline at around 3200 RPM. If it is an old 12 valve Cummins (98 and older) its redline is at 3000. As I said before, the exhuast gas on the Cummins doesn't have to travel far to get to the turbo. On the Powerstroke however, the exhaust gas has to flow through 2 pipes and then feed the turbo. The gas has to travel a considerable distance before reaching the turbo as compared to the Cummins.

 

I sthe ford turbo bigger? A smaller turbo will spool faster.

 

I am not sure on the size. The Garrett may be bigger than the Holsett, but not by much if it is. I haven't measured each one specifically but this is just from looking at them side by side, in thier respective trucks of course. I was comparing the Holsett in my Ram to the Garrett in my friends F350.

While a smaller turbo can spool faster, a lot of that depends on a few things. Like the exhaust wheel, the compressor wheel, how thier blades are pitched, etc.