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As some of you might have gathered from our introductory post in the New Members Forum, Rasant Products (very well-known for amazingly beautiful and functional ITB kits and custom GT3 intake plenum setups for the air-cooled cars), was recently acquired and the company relocated to the Seattle area of Western Washington. As part of the Rasant expansion, the company also acquired the designs and other IP from VCB Engineering for their beautiful, compact and simple to install 928 supercharger kit and we are relaunching the kits here.
The existing kit is based on the extremely efficient, low-heat, low-noise Rotrex centrifugal units (currently the C38-91 model with a 3" inlet.) The Rotrex design is basically that of a belt-driven turbocharger! The Rotrex designs feature a patented, low friction, "geared-up" internal planetary ratio system, which functions on a special traction fluid. The turbine is spooled up anywhere from 1:6 and 1:7 in the largest units, to 1:8 and 1:9 in the mid-sized units and to as much as 1:13 in the smaller units. The impellers have a maximum operating speed then of anywhere from 90,000 rpm to as much as 240,000 rpm (with variable input speed tuning, via various available pulley sizes!)
We're posting pictures here of some of the past kit installations (not sure who owns these cars now, but hope that it is okay to post them since they exist in the public domain.) We will have a new kit installed on our own 1987 32-valve S4 house-project / test mule soon and then we will post pictures of that installation as well. We'll be documenting the installation process and the initial goal would be installation of at least one kit in its current iteration, so that we can experience any issues firsthand, update installation documentation and identify early items with room for improvement.
The test car is headed to a local DynoJet chassis dyno next week to document some baseline pulls for our car, on local fuel and at local altitude. We'll post a copy of the "before" dyno sheet soon and then head back to the same dyno for post-installation results! We'll be running the first installation on modified chips tuned with the SharkTuner software, but Rasant already offers a couple of fully-programmable, stand-alone engine management systems (with the Emtron platfom at the upper end of those options.)
Leading up to this post, we have quite literally consumed every word ever written publicly about the various 928 supercharger kits here on Rennlist for kits that used to be available on the market. The flame-wars were extremely disparaging to witness, but I hope that we can get a fresh start and an honest, open dialogue about what's good and what needs to be done to develop the kits further. We currently have a 16-valve V8 kit in the works as well (and we have several iterations of Rotrex-based kits under development for the rest of the transaxle Porsche model lineup - including for the 07K 5-cylinder engine in the 924 / 944 / 951 and 968 chassis.)
We've tried to reach out to a few folks who seemed open to constructive conversations for input as well, but we would like to open up this thread for further practical feedback, technical suggestions and ideas on how we might improve on the product. We had a full day visit here at our office this week with the Rotrex Head of Operations out of Denmark, along with one of their other lead engineers and the support that we can expect from them is phenomenal! Their entire manufacturing process is now 100% robotic and assembly is tracked by single individual (registered via the unique, laser-engraved serial number on each unit!)
Even the source and vendor for all raw materials utilized in the manufacturing of each unit, is logged by that serial number! (The quality control process for each hand-built unit, is also out of this world.) The conversations around the efficiency of superchargers versus turbochargers (and particularly the Rotrex centrifugal design over other older "gearbox" supercharger designs), was very revealing! They don't produce the heat of turbos (because you don't have the restriction in the exhaust ports), so now you don't need to dump as much fuel into the cylinders to cool things down and you can run more timing!
Pricing information will be available soon and the kits will eventually be listed on the Rasant Products web page at www.RasantProducts.com (in the interim, Rasant is shipping all sorts of parts, so feel free to send PMs here, or emails and phone calls to the listed contact information on the current Rasant Products placeholder landing page!)
Last edited by Rasant Products; 10-21-2023 at 09:55 PM.
It looks like a tidy install with minimum work required to service the belt.
Based on the pictures you might want to consider as an addon ,
some Hans motor mounts to lower the engine to make the induction hoses an easier fit.
Or just run the collapsed stock mounts.
I have a general question; are our 30/40+ year old cars able to withstand this mod (increased load/heat or otherwise increased strain on such old engine parts)
WITHOUT an internal look-see (heads, head gaskets, rings etc)?
I had dinner with some local folks last night and we were talking about superchargers, coincidentally. (We also had a fun visit from someone that really liked @Michael Benno car, and regaled us with a story about his time with twin turbocharged 928s).
Having missed out on the initial development and flame wars on these kinds of parts for the cars, is going this route now easier with things like the @PorKen chip? From previous conversations with Ken about the adaptability of those chips, it seems like they'd make the ECU part of things pretty easy, as far as implementation goes, on that side of things.
Considering they are in our neck of the woods (Woodinville), maybe we can get something going on the PacNW list and have a gathering/visit one of these days...
It’ll be awesome to have another SC kit available to everyone! I know the earlier kits had modified (shortening) stock fuel rail on the driver side. What’s your new kits offering…new fuel rails?
It looks like a tidy install with minimum work required to service the belt.
Based on the pictures you might want to consider as an addon, some Hans motor mounts to lower the engine to make the induction hoses an easier fit.
Or just run the collapsed stock mounts.
Thanks @Mrmerlin - It is indeed a super-easy kit to install and installation is fairly brisk. It was even designed in such a way that the belt can be removed and reinstalled on the way to and back from an event, or once a year for things such as a visit from, say one's mother-at-war for example.
Hans and I had a great chat last week and there might even be some ways to work together to bring improvements to the kit, utilizing some of his parts - yes.
Originally Posted by Shirah
I have a general question; are our 30/40+ year old cars able to withstand this mod (increased load/heat or otherwise increased strain on such old engine parts)
WITHOUT an internal look-see (heads, head gaskets, rings etc)?
Just asking!
@Shirah - Meh, your motor is either good or it is not. If it is currently consuming vast amounts of oil and / or smoking all of the time, then yeah - it would need to be rebuilt anyway. With low boost, you're not going to hurt anything.
If somebody out there wants to run higher than the recommended boost, then yes - you should ABSOLUTELY first rebuild the engine and install stronger forged internals and fresh head gaskets.
Even on the house-project that we have selected for installation of the first kit under Rasant's ownership, we are going to do some things such as a compression test, a leak-down test, inspect the MAS and so on - just as a date-stamp precursor and to evaluate the current condition of the mechanical unit.
Eventually, we will rebuild it and then also run higher boost.
If you have a healthy motor though, it'll be fine. If it's already a tired motor, then it is tired. Either way - 7, 8, 9, 10psi isn't going to hurt it more. I'd be worried about the unburned oil washing over the MAS sensor already, and through the cats today (even without forced-induction.)
Originally Posted by Zirconocene
I had dinner with some local folks last night and we were talking about superchargers, coincidentally. (We also had a fun visit from someone that really liked @Michael Benno car, and regaled us with a story about his time with twin turbocharged 928s).
Having missed out on the initial development and flame wars on these kinds of parts for the cars, is going this route now easier with things like the @PorKen chip? From previous conversations with Ken about the adaptability of those chips, it seems like they'd make the ECU part of things pretty easy, as far as implementation goes, on that side of things.
I'm looking forward to seeing the development.
Cheers
@Zirconocene - I am not familiar with the PorKen chip - only with their upgraded timing belt tensioner (which I love by the way.) Also, I would like to ask personally, that we suspend with the aforementioned flame wars!
For the relaunch of the kit, Rasant Products is going to take a pretty staunch position on engine management for accurate fueling and ignition timing, as well as intercooling (or at least conservative timing without intercooling.) I'd prefer to go the safest route such as "stipulating" that - Anyone purchasing the kit HAS to purchase an intercooler; Anyone purchasing the kit HAS to purchase a fully programmable, stand-alone engine management system; All kits MUST be installed by Rasant Products (or by an authorized installer!) and All installations must be tuned by a Rasant Products tuner.
However, I know that this is not a reality. People will do what they want to and one can't stop it. Some owners will already have their own tuning software on the car. Some folks are experienced tuners in their own right. Some of us want to do our own installations and the kit was designed with that in mind.
There are so many variables here then. Besides -
Superchargers don't create the exhaust restriction that turbocharging does and therefore does not have the heat buildup. You can run less fuel and more timing, for the same amount of boost! Rotrex superchargers - specifically - build less heat than many other superchargers on the market today and ahve their own contained oil and cooling system. Rotrex superchargers are so efficient that with anything below 8-9 psi of boost, you don't really need to run intercooling - all installations can always benefit from intercooling at ANY pressure, but you don't NEED it! Victor (VCB Engineering) and Jim (SharkTuner) are both convinced that the SharkTuning software with two accurately programmed chips "CAN" be sufficient for these cars at low boost!
So, we will make recommendations, but we won't enforce it as a condition of purchase. As long as the cooling system is fresh with a solid radiator, a fresh timing belt and a new water pump, you should be good with low boost AND the SharkTuner chip at a minimum.
We offer a function-rich, fully-programmable, stand-alone engine management system with a wiring harness for under $2K - why not go that route!?
Originally Posted by Tom. M
Considering they are in our neck of the woods (Woodinville), maybe we can get something going on the PacNW list and have a gathering/visit one of these days...
@Tom. M - We'd LOVE to host you and some of the other folks from the community out here some time. Would you like to spearhead that? Please make contact with us via the www.RasantProducts.com website and ask to schedule an event. We'll gladly host - by invitation.
Originally Posted by Darien
It’ll be awesome to have another SC kit available to everyone! I know the earlier kits had modified (shortening) stock fuel rail on the driver side. What’s your new kits offering…new fuel rails?
Keep the updates coming!
@Darien - Thanks, we are EXTREMELY excited to be relaunching the kit (and I for one, can't wait to experience it on the house test mule for myself.) I've driven supercharged 928 examples before and it totally transforms the car.
Yes, for the moment, we will keep the replacement setup for one of the fuel rails, but like I had mentioned earlier, there is going to be a bit of a kit-redesign in the works (once we have installed it in the current configuration - and as sold before - to assess where were are with it.)
Here is the house test-mule getting the kit.
Last edited by Rasant Products; 10-24-2023 at 01:07 AM.
Okay, the car went to a local DynoJet this morning for the baseline pulls prior to the Rotrex supercharger kit installation. As promised, see results below -
My guess in the other thread was pretty close. What's up with the A/F. Very lean. You should be in the 10's by the end of the run. Almost as if it didn't go to open loop. Did you check the throttle position sensor to make sure it's operational as it should have switched to the open loop map at WOT.
10-21-2023, 09:42 PM
928 Rotrex Supercharger Kit Relaunch!
