I'm adding info as I go and pics won't be posted until my return on the 13th.. here's what I've got right now.


Physical Differences:

How do you know what unit you have?

Rotrex C30-94 units and HKSGT7404 units look similar in appearance but do have some differences. Rotrex’s have “Rotrex” or “Holset” in the casting while the HKS’ will have “HKS” a long with a “HKS GT Supercharger” label visible on the top of the blower itself. It its believed that the original superchargers came with Rotrex and HKS later developed their own blower, they incorporated the 7404 on the newer kits.

The mounting brackets are different as well. The Rotrex has 4 longer mounting bolts that go through the blower completely while the HKS has only 3 in a triangular fashion and attach to thread wholes on the face of the blower. The idler, bracket pulley from either of the units are interchangeable but the pulley’s don’t look to be.

Rotrex Bracket:



Rotrex Blower:



HKS Bracket:



HKS Blower:



Bracket spacing on the HKS:



Bracket spacing on the Rotrex:



HKS uses a cylindrical container for the HKS Supercharger Fluid and Rotrex uses a square shaped one. The oil cooler hoses also attach differently on the units, the Rotrex has banjo fittings at the 10 and 2 ‘o’ clock postion. The HKS has it’s banjo fittings on the aft of the blower.

Intercooler, Bypass Valves & Chargepipes:

These parts are exactly the same for both kits as I've used the pipes/intercooler from the Rotrex kit on the HKS without any issues whatsoever. If your having an issue with the bypass valve, the OEM kit bypass valve has been discontinued. Other options are available if you wish to use the bypass but it can be converted to a BOV. Sam@GTM recommend the TurboSmart bypass valve for it's efficiency, size, and price. The HKS Race Bypass Valve is available too. The biggest problem with the OEM location is that your limited on space, a HKS SSVQ will not fit in the OEM location so you'd have to put it further down(i.e. right before the intercooler).

 

Operation Differences:

Rotrex’s run a slip system and engage at 5% slippage, the HKS uses a eccentric type and creates boost when your foot is on the gas. They’re relatively quiet units but do have a “sucking” air sound coming from the front of the car so it’s not completely silent as some have said. Oiling is done in a clockwise position:

1. Reservoir
2. Inline filter
3. Blower
4. Oil cooler


Pulleys:

A range of pulleys can be purchased through individual sources. All OEM C38/HKSGT7404's come with 95mm pulleys. There are instances of people using 90mm and 85mm pulleys(I have 90mm pulleys on both superchargers) but most will agree that the 85mm is dangerously close to over spinning the blower unless you have an aftermarket crank pulley(i.e. ATi and Fluidampr) which is larger than the OEM Nissan pulley(albeit not by very much). They're an 8 rib pulley for both set ups but the lip on the inner side of the pulley(side that mates with the supercharger) has a lip to it and do not work with the HKSGT7404 because its too big. GTM's pulley's are a very nice piece





Pictures of how the kits come:

Rotrex:



HKS:



Installed differences:

Rotrex



HKS

 

Oiling systems:

Oil is a HUGE deal on these particular units. Their oiling systems are the same but the oil is very different and are blower specific. Every unit consists of:

• Blower unit
• Supercharger oil cooler
• Inline filter
• Reservoir
• Supercharger Oil(HKS for HKS and SX100 for Rotrex)

Rotrex requires oil changes at 80,000km/50,000mi, 2 years or which ever is first. Active does their service on HKS kits at 100,000km/62,000mi so I'm going to use this as a benchmark for the HKS kit. Oil is NOT interchangeable, I’ve received the same information from both URD(Underdog Racing), Kraftwerk, and Active Autowerke (which uses both units on a multitude of BMW’s). The oiling compounds are different and if you ever used HKS fluid in a Rotrex(same principle applies the other way too) and something goes wrong… the warranty is void on the blower and your going to fork out $2-3K for a new kit as units are not available for purchase individually. I’m sure if you were in a pinch you could but they very adamant about not mixing fluids.

HKS Traction fluid P/N:

G08834-K00020-00



GTM and Active carry the oil but.... it's hard to come by and still is on order:

http://www.gtmotorsports.com/product...1&cat=0&page=1

http://store.activeautowerke.com/hks...fluid-p66.aspx

Rortrex Fluid can be had in different places:



http://www.urdusa.com/Forced-Inducti...duct_info.html

http://store.activeautowerke.com/rot...fluid-p65.aspx

http://www.kraftwerksusa.com/product...p?productId=37

I just recently bought fluid and filters through URDUSA.com, they had it in stock and it was at my house in 3 days.

 

reserved for later

 

and one more for good measure... I talk a lot.

 

not seeing any info

drunk post?

 

It was really late and I don't have all the pics. I leave to Washington St today and will be there until the 13th, I'll have some info by tonight.

 

picked a good time to come up here lol :P rain and 40 degree weather all week lmao

 

The Gorge never sees sunshine! I fly into Portland and drive to Bingen/Hood River.

 

ah your going to the other side of the mountains :P its even colder over there! no rain though this week i dont think atleast tho :P

 

in for info

 

I have lots of pics also, and can comment on anything that needs be.

 

I'll be getting those pics from you when I get back and your welcome to add anything you want on this thread. I'm going to incorporate Gab3d's build here because it also has to do with Rotrex.

 

Reading the info does this mean the rotrex is better or hks.. sorry for the noob question

 

No such thing as a noob question in regards to Rotrex/HKS. The HKS units seem to make "better" power because of how they create boost. Rotrex has more support and blower options. HKS has 2 units that are available for purchase... a 8550 and a 7404. Active Autowerke uses both in their kits but uses 8550's for the newer kits(E92 M3) and use Rotrex for the older kits because of physical size issues. The Rotrex's have several units per range(C15,C30,C38). I believe the HKS is better but that is relative, both units are export(HKS Japan-Rotrex UK) but more people are using the Rotrex due to their support.

 

Side note of info on Hks oil feed and drain they are not banjo fittings. They are on the bottom opposed to the top mounted rotrex.

 

Good set of info, regarding the way it makes boost where did you get the info from? By looking at the way boost is built on the 7040 on the HKS VQ kit and comparing that to the 8550 on the AA e90 kit, they seem to be employing different means eventhough they are both HKS unit. My guess based on ctran77's HKS kit, which is also using an 8550, is that the compressor desgined has changed post 2008 and is now more similar to the rotrex, but I'm just guessing here. Do you have pictures comparing the impeller?

 

I got the info from Active. HKS only made that one 8550 here at HKSUSA which never made it into production. I believe the impeller's are the same but unfortunately I wasn't able to take it apart because it's going back to HKS Japan. I would like to the think the housing is what's the difference in terms of power. I'm very interested in your set up and I think it would be good for Same or Mike to add info here because it's a Rotrex based kit. One thing to keep in mind is I've seen a bunch of different pics of the kit.



Look at the bypass location on this pic of kit above... I'm going to include upgrades in one of the reserved area's.

 

Good informative thread,well done. Temp in Sydney is 33c (about 96f ) and strangely it's been pouring for most of December.

 

This is what I was referring to. Take a look at the behavior of the 8550 and the 7040 from the old HKS kit. On a side note, it's interesting that they advertise that the vq kit comes with the 8550 as oppose to the 7040.

http://www.hks-power.co.jp/products/...rformance.html