Written by PJ Pitcher. AKA Turbology.

When we talk about ‘style’ in drifting, some of the first things that come to mind are of course the aesthetics of the car, and also the driver’s particular way of sliding it. Be it an eye-catching livery or big, smoky angle, cool points matter, especially since drifting is not about who crosses the finish line first. That being said, sound is an equally important sensory factor in drifting, because all those cool graphics and vaporized tires need a soundtrack to bring them to life.

if you are anything like us, and chances are good that you are, since you are reading this, smashing the limiter, chattering turbos and howling V8s hold some of the greatest appeal in drifting. That brings us to Scott Onishi, owner of OCD Works, and his now-infamous T51R turbo modification. OK DL, maybe I am a bit new to the game, but WTF is a T51R, first of all? It was old Garrett turbocharger that was sold by Japanese company HKS.  They sold as 71mm,(KAI) and 76mm(SPL). 


OK great, who cares, what’s the big deal? In their heyday, these were cutting-edge turbos. Where many of the big name Japanese tuners were still running Mitsubishi-based turbos, the T51R units used Garrett center cartridges with proprietary compressor and turbine housings. They also featured a unique anti-surge design, so the slightest bit of load, even free-revving, produced noticeably-loud whistling, as demonstrated here.

That brings us back to Scott-san at his Tennessee-based workshop. The OCD crew specializes in multi-axis CNC parts, and Onishi devised a clever process to modify nearly any turbo compressor housing to sound like the iconic T51R. Each compressor cover is carefully secured on a custom jig before being precisely machined in the CNC cabinet. Meanwhile, a custom insert is milled to exact specs from a six-pound billet of aluminum.

Once the housing has been hogged out and the insert milled, the two are assembled and the cover is ready for shipping back to its owner. Alternatively, OCD also offers brand new turbos from all the well-known manufacturers with the T51R modification already performed.The service is available for most small, mid and large-frame turbos, though larger compressor housings may cost slightly more. Some small-frame turbos may not have enough removable material for the mod.



Now the most important question: why do it? While Onishi tells us that independent, third-party shops have shown increased numbers on the dyno after the modification, he is quick to stress that this upgrade is first and foremost for greater driving pleasure, quite simply. There may be some physics-based explanation of improved laminar flow etc, but that is squarely above our pay grade. This is all about style, and now you can whistle at babes while you shred!


Will this modification void the factory warranty of my existing turbocharger?
As with nearly any other product, many manufacturers' warranties normally state that any modification to their turbochargers will void the warranty. Therefore, the same holds true for welding a V-band or new flange, as well as anodizing, powdercoating, ceramic coating, and tapping to modify for a speed sensor. All these modifications will technically void your warranty as well.
PS, One of large turbocharger company seen us machining compressor cover daily and they actually made exactly same thing as prototype and showed at trade show.  Therefore, if one of manufacture does it.  how do you void warranty. 
I have compressor cover which was machined by another company however, it does not work. Can you fix it?
Unfortunately most all of time, once compressor cover are machined wrong , then there is no going back.   In most case, which will require to start from new compressor cover, if manufacture offers as compressor cover itself as replacement parts.   If not, you will be buying another turbocharger to replace your compressor cover.  So be sure to send it to us, and get it machined correctly.  just because someone copy our stuff and you can purchase cheaper does not mean that always good deal.  

Can I purchase a new compressor housing from you with the mod so I don't have to send in mine?
Yes, you can go to our website to purchase one, we offer nearly all the major and well-known brands.

Does this mod help my turbo spool faster?
No, it will operate exactly the same as before the modification. Does it make more power or lose power? No, the turbocharger will operate exactly the same, which means if your car is tuned previous to our machining, the parameters will remain exactly the same.

Can you do this on turbochargers with a 3.0'' (76mm) inlet?
It is possible on some compressor housings. It is all depends on how much factory casting is available for machining.

Can this mod be done on the Borg Warner EFR series ?
Yes, most all of them except those with a 3-inch inlet. If you have a 3.0" (76mm) cover, we can convert it to an SX-E series cover which we also sell.

Can I remove the mod, if I don't want the sound anymore?
No, the modification is permanent and irreversible.

Can the insert be polished, powdercoated, or anodized a different color?
Yes, however it must be done prior to our finish machining, so please plan and let us know ahead of time. 

Does your price include shipping it back to me?
When you check out, you will be charged for return shipping.

How long does it take to get my turbo back once you receive it?
Normal turn-around is four (4-6) business days from receipt. We do not work on ANY weekends or holidays.

Do you guys have a phone number I can call if I have question?
To ensure mutual accountability on both your end and our own, we only communicate via email. Should there be an issue, we will have records of dialogue to reference. 
Can the modification be performed on a factory turbocharger? 
Yes and no, as most factory gasoline turbochargers are not machinable, but many diesel factory turbochargers are machinable.
Why am I not getting confirmation or update on email?
You will need to make sure that you use email address which you have full access to . 
ex: I used old paypal email address which I have no way to access to ,  or I do not use that email address anymore so on.     We will automatically send you email base on your information that is on your purchase.  
How long does process takes?
We normally process all machining in 6-10 business days, and Most all parts are coming from manufacture unless its noted, therefore, 6-10 business days are for machining time frame ONLY.

Do you guys ship overseas?
Yes, we ship worldwide via DHL.
How long does polish and powdercoating takes if I want to add on my purchase?
Normally it takes 6-8 days turn around time on both polishing and powdercoating.  

How much does the modification cost?
All of our prices are based on the size of your compressor inlet cover. Most all factory or aftermarket turbocharger companies provide these specifications on their websites. 

My cover was machined, however, it does not sound the same as other videos? 
A good question with a simple answer. A turbocharger is simply an inert mechanical device until driven by exhaust gas. The more exhaust energy and gas pressure, the more your turbocharger will accelerate faster than others.

Using a BW S366 on a 0.9-liter 3-cylinder diesel Smart Car as an example, it is far too big that and will not spool efficiently. If this S366 was used on this engine, then the shaft speed of the turbocharger will be very poor and slow, which will not make any sound.

But if you use the same BW S366 on a 5.67-liter 8-cylinder gasoline GM engine, you will be driving this turbocharger much faster than with the low-flowing and volume 0.9L engine. Therefore, the spooling sound will happen much sooner and louder.

Even the exact same turbocharger used on engine set-ups of very similar configuration can sound totally different. Just because they share identical parts or components, there will still be slight variances even among the same manufacturer.

When you buy a new car, even two identical models off the dealer lot will have different dyno power and torque results. Even though they are the same car, all things are different in real-world scenarios and working conditions, the same as turbos.