hacker-pschorr

Nope - Carl designed his own 32V kit using a different blower and stopped marketing the Murf928 kit.

Easy way to tell them apart, Murf928 = Vortech Supercharger.

Yes - directly from Tim Murphy

The kits listed on the 928 Motorsport site have nothing to do with the Murf928 kit.

Different bracket, tensionsing system, pulleys, intercooler etc....

As far as I know, Carl's kit is only available with a Corky Bell FMU to adjust fuel pressure under boost & stock ignition timing.

Murf Stage 1 can either be had with a Vortech FMU or custom fuel chips with 42lbs injectors. Both come with custom ignitions chips.
Murf Stage 3 kits all include 42lb injectors and custom fuel & ignition chips.

andy-gts

That's because people like to confuse "boost" with "power". Just because you are making boost doesn't mean the car is making any power.

As for the claim "no power under 4k".......the person claiming this did not buy a Murf928 kit, and the setup he did buy also had him buying a SharkTuner to tune it himself.
I'll stop there to avoid saying something I might regret later. It's just a perfect example showing there is a lot more to making power than simply shoving some boost at the throttle plate.

Hacker,
Yes you are right , and I enjoyed trying to sharktune and found it very fascinating........now I see that chassis dyno would have helped and that was a while ago.....sometimes I embellish the down side of centrifugal a bit to justify my stroker motor desires.
Just my experience with one type....definately not an expert!

EspritS4s

Hacker,
Thanks for clearing that up for me. I have a used Murf kit on the way with some missing parts, so I know who to contact for info now.

hacker-pschorr

I give you a ton of credit for the work you did on the GTS. I'm lucky to have two very experienced tuners (Mike Schmidt aka Z and Luke @ Beyond Redline) in my corner. I don't even attempt to tune my car anymore. Sure I sit in the passenger seat and run the laptop, but Luke is behind the wheel on the dyno running the show.

Your stroker is going to be one hell of an engine. It's going to be a perfect example of how to make boat loads of power without any boost!!!

You mentioned open road racing. Do you plan to do a full cage for the unlimited class?


No problem, just send an e-mail to info@murf928.com.

rgs944

I am far from any expert but here is my thoughts from someone who is considering a SC kit in the future for either the 968 or 928. What I really like about Carl's stage 1 kit is ease of installation and low boost. I do not plan to race but would just like another 25 or 30% more power in either car to bring them more up to modern specs. That should be able to be done safely enough without spending another 6-12K upgrading the car so it can take the extra power of some other systems. If I want to get into upgrading injectors, clutches, brakes, transmissions, etc.,,, at that point I think I would just spend that money on a late model Z06.

SQLGuy

OK. This may be bad form, but it's my money, my time, and my car, so I'm going to name names.

At this point I'm down to choosing between the Murf and 928 Motorsports Stage 1 kits.

The rear turbo sounds interesting and creative, but, call it prejudice, or lack of imagination, I really don't like the idea of my air intake back by the muffler, and I still can't believe that 24 feet of air column between exhaust and intake doesn't contribute to some amount of lag.

The twin screw is a bit too expensive, a bit too prototypical, and much too unavailable.

So, here's what I think I know about the two currently availble kits:

1. Both Murf and 928 Motorsports have really great people that are happy to answer questions and work with you on project details.

2. Murf has a lot of 928 installs, and, as far as I can tell, all the people that have installed these kits are happy with them.

3. The 928MS kit is newer and doesn't seem to have as many installs. They tell me there have been about 100 sold, but I don't know whether that includes Ferrari and 968 kits as well. Here, I've heard from two people that have them: one happy and the other not so much.

4. The Murf SC is a Vortech which is self-contained oil lubricated (no oil lines), has somewhere between 73% and 78% efficiency (can't tell for sure because I can't find the details for a V3 T-trim unit), is gear driven, and is rated for pretty large engines (bigger than mine; again, can't find the exact details for this unit).

5. The 928MS SC is a Raptor V unit, which is dry lubricated (ceramic bearings), has a 75% efficiency (+/- 5%), is belt driven, and is rated for engines just up to the size of mine (actually < 5.0l, per the Raptor web site).

6. Both kits include an FMU for modification of fueling. The Murf kit also includes a custom ignition map to retard ignition timing under boost.

7. The Murf kit seems to have an air intake snout down behind the radiator, while the 928MS kit has a cold air intake filter that sits across the top of the radiator.

8. Both kits include replacement fans. Both fans sets use the stock fan controller circuits. The Murf kit uses 4 small "muffin" fans. The 928MS kit uses 2 smaller than stock (8") fans, and offers the additional cost option of a larger pusher fan.

9. So, given all of this, installation time/effort for the two kits should be similar, with a bit more work on the Murf side owing to swapping the EPROM in the ignition ECU.

Concerns:

I would expect cooler air, assuming all data so far is accurate, from the 928MS unit, because of its cold air intake and maybe because of its ceramic coated impeller. I'm not sure this is a big of a differentiator as it has previously been made out to be, though, because the Vortech efficiency looks to be on par with that of the Raptor, and the current Vortech is not lubricated by engine oil.

Googling Raptor doesn't seem to turn up any reliability problems, except broken drive belts. Not an issue with Vortech.

Ignition timing is big question to me. I know that S3's used a MAP sensor in the ignition ECU that retarded based on load, but A) Not sure if S4 has this and B) If it does, does stock ECU MAP sensor accept +.5 Bar? S4 does have a good knock sensor system, but I'd rather not be relying on it all the time.

The feedback you guys have given so far has been really helpful. Thanks again for sharing your knowledge and experiences.

Paul

auzivision

One minor correction... Murf kit sucks cool air out from under the front of the fender, not from behind the radiator. Carl kit suck air from above the radiator and heat rises. Truth be told, sucking air in at the tail just might be the 'coolest' spot.

hacker-pschorr

Murf928 Stage 1 can be purchased without the FMU and instead 42lb injectors with custom fuel chips.

IMO this is the best way to go. I need to check with Tim on current prices of the injectors.
Using an FMU is the "old school" way of doing it before the Shark Tuner was available.
Going with new injectors also takes one item of my personal "to-do" list before adding boost, and that's having the injectors professionally cleaned.

Another advantage to this setup is an easier transition to Stage III if you decide to go this route down the road.

There is an airbox on the supercharger behind the radiator. Off that airbox is an intake hose that routes to the fender which places the air filter behind the headlight. Nice source of fresh air, no cutting or permanent modifications are required.

Personally I would never run boost in a 928 with a stock ignition map.

SQLGuy

Thanks for the correction on the Murf intake.

As to heat rising, though... that's in still air, and if it has a place to go. When moving, the majority of the air moving through the engine compartment is going to be pulled down and out under the car.

AO

Ding ding ding ding! We have a winner.

Other things to consider are the availability of an upgrade path.

I believe the 928MS kit tops out at about 7psi with no intercooler option to go beyond.

The Murf kit has a Stage III option that can be added at any time. to take you upto about 14psi!

(Okay a little time out here. Everyone I've ever talked to with a Murf Stage I has always considered upgrading to a Stage III. Not because a Stage I isn't powerful enough, but because the option is there and boost is addictive like crack! You don't get that option with the 928 MS kit.)

But I personally think it is irresponsible to send out a kit that you know is going to cause damage to the motor through knocking. Tim Murphy has invested considerable dyno time ($$$$) getting the tune just right.

If it were me making the call between these two kits, I wouldn't hesitate. I'd get a Murf kit, hands down!

dprantl

+1000. You are just asking for trouble if you run boost through a 928 with stock ignition maps, even if you do change the octane loop to 91 (which will buy you a small safety margin). Even on an S4+, the EZK can only dial back timing once knock has been detected, so a little damage may already have been done. Multiply this by say 20 runs in a short period of time and you are pounding the crap out of your rod bearings which are pretty soft on the 928 to begin with.

Dan
'91 928GT S/C 475hp/460lb.ft

John Speake

As a point of possible interest I would add that the MAP sensor in an S3 or Euro S2 does not register positive manifold vacuum, so is useless under boost.
The load signal of the EZK is OK to use with boost, as long as the EZK is remapped. Unless you remap an S4 or later igntion, and (say) run 6 psi boost, you need to reduce igntion timing at max cylinder pressure by about 6 degrees. The total retard range from the knock system is 9 degrees, so you can see there is risk with such a small safety margin if you don't remap. You only need an injector on one cylinder not to flow as well as the others, and you could be in trouble. Or a bad batch of petrol (gas)...

AO

Whoa! I missed this the first time. I don't believe they've sold 100 928 MS kits. I know they sold the majority of Murf's kits back when they carried them, so my guess is Carl is saying he's sold 100 kits - leaving you to infer that they are 928MS kits. But I'd bet most of them or a large percentage are probably Murf kits.

SeanR

I'm sure there has been a bit of an embellishment with the number sold. ATI laughed when I asked them of they had sold 100 of the harmonic dampeners through them. They said "nope, only 6"

AO

You guys are missing the point, 928MS always posts "corrected" crank numbers, not RW numbers.