Highway & Heavy Parts Answers Your Diesel Engine Questions: Turbochargers


customer questions turbocharger | Highway & Heavy Parts


Here at Highway & Heavy Parts, we sell a lot of turbochargers. We carry a number of the industry's leading brands for all major OEMs, and have helped diagnose a lot of our customers' turbo failures. We provide solutions to help get them back on the road.

Like a lot of the various diesel engine components we carry, a lot of questions come into our sales department and social media about turbochargers, and sometimes it's difficult to get to all of them.

So, today we're answering all your turbocharger related questions! You can also check out our video for more information:



Need help with your turbocharger problem? Our ASE Certified Technicians are ready to help you with your diesel engine questions!

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Your Diesel Engine Turbo Questions

If you're looking for answers to your diesel engine questions, we're here to help! Below are some of the questions we get asked frequently here at HHP:


What does the AR# refer to and how does it affect turbo operation? 


turbo questions ar number | Highway & Heavy Parts


The AR # describes the geometric characteristics of all compressor and turbine housings. Technically, it's defined by the cross sectional area divided by the radius of the turbo center line. 

Commonly, we're looking at AR #s on exhaust housings. If you think about it, the smaller AR # is going to spool the turbo faster, but it's also going to create some restriction in the exhaust housing. So, if you go from a 1.32 AR housing to a 1.45, the 1.45 will slow the turbo down just a little bit, but it will also allow exhaust gas to more easily escape the exhaust housing. This potentially lowers the exhaust gas temperature.


Why do SDP ESNs use different turbochargers that are harder to source?

SDP engines commonly use a Garrett turbo with an actual ball bearing in the center sections as opposed to the standard bushing most turbochargers use. They've been proprietary to CAT, and some tech is harder to come by.


What is the difference between a turbo with and without a wastegate?  Can wastegated turbos be removed and replaced with non-wastegated turbos and vice versa? 

So, the difference between the two is that a turbo with a wastegate is designed to spool up quickly, but you would get into a situation where you'd overspeed the turbo if it didn't have a wastegate on it. The wastegate allows some of the exhaust gasses in the turbine housing to escape around the turbine wheel. This keeps those turbo speeds in check.

One thing that we do see occasionally is people with wastegated turbos putting vice grips on the hose that goes to the wastegate, essentially overriding it. This lets the turbo over-speed. Eventually, the compressor wheel will blow apart because it's not designed to go that fast.

There are typically turbochargers that will work in place of one another. One that comes to mind commonly is the 60 series Detroit. A lot of those engines come with the wastegated turbo. A lot of people like to go with the non-wastegated turbo for performance reasons. Going from your 172743 to the 171702, for example. Those both fit in the same place, but one is wastegated and one is not. 

Want to know more about wastegates? Check out our article on how wastegates work on diesel engine turbos.


Is the Cummins ISX the only OEM that uses a variable geometry turbocharger? 

No, there are a lot of OEMs that use a variable geometry turbo, including Volvo. Mack, Detroit Diesel, and Navistar. It's getting to the point in emission requirements where VGTs are needed for regeneration purposes. So, many OEMs use VGTs.

Looking for more info on VGTs? We have a post on how variable geometry turbochargers work.


What are the specs of a "Big Cat" turbocharger and what horsepower range is it good for?

The Big Cat turbo is a non-wastegated turbo with a 78mm compressor wheel and a 1.32 AR housing. The turbo is good from about 550 to about 700 horsepower. It's a very popular turbo.


If you have any further questions on turbochargers from any major OEM, let us know!


Need a diesel engine turbo or other replacement part? We have ASE Certified Technicians on staff who can help find you the right parts for the job! Give us a call at 844-304-7688, or request a quote online