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928 Supercharger question...

Discussion in '308/328' started by mike996, Nov 20, 2019.

  1. mike996

    mike996 F1 Veteran

    Jun 14, 2008
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    Back around 2009 I was thinking about purchasing the 928 Motorsports supercharger kit for my '89 328. In fact, I had intended to do so but the IRS decided I owed them money that year, so I couldn't afford it. Subsequently, I lost interest but it is now rekindled.

    One thing that concerns me is that the manufacturer states it will add approximately 50% more power. In my experience, that is beyond what most cars' OEM systems can withstand without modification. 30% increase is a generally safe without other mods to the engine/drive train.

    Has anyone purchased/installed the 928 supercharger and run it successfully over several years WITHOUT any issues with the stock drivetrain/clutch, cylinder head gaskets, or other components?
     
  2. Rifledriver

    Rifledriver Two Time F1 World Champ

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    #2 Rifledriver, Nov 20, 2019
    Last edited: Nov 20, 2019

    Except for sizes, compression ratios etc the 308QV/328 line all used the same cranks, rods, pistons, head gaskets etc. as the F40 with 500 HP. The F40 did have a very effective piston cooling system.

    The clutch and drive train are very sturdy providing you are not side stepping the clutch. When you do you will key hole the holes in the ring gear and carrier prior to breaking the bolts. If there is an issue with the clutch the V12 clutch from Daytona/400 etc is the same with more clamping pressure.

    If you have a hankering for 100 or so more HP it is probably the way to go.
     
  3. mike996

    mike996 F1 Veteran

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    Thanks RD, great info! :)
     
  4. jim rosenthal

    jim rosenthal Karting
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    Tell you what, Mike, come up here and install one on my car, that way when you start yours it will be that much easier. :)
     
  5. mike996

    mike996 F1 Veteran

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    Thanks Jim, it's a great offer. If I actually had the time to do that, I'd much prefer spending your money on a supercharger first! Welcome to the site! you probably already know, it's best not to ask about cam belt intervals/methods or oil preferences! :) Just kidding!

    Well, sort of. ;)
     
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  6. shashi27

    shashi27 Formula Junior
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    Hi Mike, I have had one on my car for about four years with no issues. You can set the level of boost by the angle of the pulley on the SC. Mine is at the lowest setting. Most of the time the car drives like a normal 308. Only when you step into it does the supercharger make itself known and you get the acceleration you wouldn’t expect from a standard 308. My engine is for the most part stock though I added a Forza water pump. I like that it is bolt on and I can go back to stock. I have upgraded brakes, coil overs, and bushes to handle the power. It is as a Sunday driver. No leaks or problems.

    The only downside is that you get that SC whine all of the time. For the money it is a good option.

    Shashi
     
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  7. mike996

    mike996 F1 Veteran

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    Thanks, Shashi! Long term use report is really valuable!!!! :)
     
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  8. Rifledriver

    Rifledriver Two Time F1 World Champ

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    Is it centrifugal or a PD blower? Sounds like a centrifugal from your description.
     
  9. Lawrence Coppari

    Lawrence Coppari Formula 3

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    I wonder if a clutch could be installed on the drive belt that would allow the driver to control when the supercharger operates. I have an AMG Mercedes with a clutch on its accessory belt that does not engage the Roots type supercharger until the throttle reaches a certain opening.
     
  10. Rifledriver

    Rifledriver Two Time F1 World Champ

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    That is done primarily to increase fuel mileage and make passing the various smog standards more easily. Superchargers, especially of the positive displacement type are terrible parasites and kill fuel mileage. I actually like blower noise but in a car like a MB I can see where it could be a negative too.

    With a positive displacement type on a 100% duty cycle the additional throttle response and low throttle input improvement is just not something I am willing to trade away for more MPG.
     
  11. sltillim

    sltillim Formula 3
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  12. Rifledriver

    Rifledriver Two Time F1 World Champ

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  13. mike996

    mike996 F1 Veteran

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  14. shashi27

    shashi27 Formula Junior
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    Yeah. 4L would be my optimum choice but I can justify the price. That gets me another car to place with, or an upgrade (manual 430). I just can’t seem to let this one go though.
     
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  15. mike996

    mike996 F1 Veteran

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    The one thing that concerns me was the issue someone had here of the kit not fitting due to interference with the frame. It would be most upsetting to purchase the kit and have that occur, especially since he explained that 928 Motosports would not refund the price. I can understand their reluctance to do so since the kit would have had to be partially installed to figure that out and is, therefore, no longer "new" but still, if it's marketed as fitting 308s'328s and doesn't, it seems there should be some recourse.
     
  16. Rifledriver

    Rifledriver Two Time F1 World Champ

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    I did a 3.5 liter in my own car with all the best parts etc. I have told others that inquired about me doing one for them and my response is always the car isn't worth it. As much as I like 328s its expensive to do that. Buy one with a good engine and take care of it.
     
  17. mike996

    mike996 F1 Veteran

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    FWIW, I contacted the guy selling the 928 moto supercharger on Craigslist (post #11). He's selling it as part of an estate sale. The original buyer of the kit passed away, never having installed it. The seller is not knowledgeable re the kit or the car. I almost bought it but I couldn't verify that all the pieces were present and that they are the "current" pieces that 928 Motosports provides. It's a good deal IF everything is there - $2k under the regular selling price. I was looking at the pics he provided and at the pics at 928 motosports to see if I could determine if all the parts are there. They SEEM to be EXCEPT for the adjustable brace that goes from the intake manifold to the supercharger support. That part MIGHT be in the kit but I didn't see it in the pics. Frankly, if that was the only missing part, it would be an easy one to make up with hardware-store parts. The seller has parts and the invoice, but no instructions. I suppose the instructions are available from 928.

    Also, I have never used Craigslist or, until post #11, even looked at it. I am reluctant to gamble $5k on my first experience! ;)
     
  18. ferrariowner

    ferrariowner Formula Junior

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    How does the kit provide for proper fuel and timing under boost?
     
  19. mike996

    mike996 F1 Veteran

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    Well - fueling is the job of the K-Jet. Per 928 motosports, the OEM K-jet can provide sufficient fueling for the boost as set in the kit. They also say no timing changes are made/needed in the application.
     
  20. Rifledriver

    Rifledriver Two Time F1 World Champ

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    #20 Rifledriver, Nov 25, 2019
    Last edited: Nov 25, 2019

    Stock compression is pretty low, stock timing is pretty conservative so not real surprised. Besides with a centrifugal boost only becomes significant at high rpm.

    I have just shy of 11:1 compression in my 328 with the most advance available from the Microplex and I get no detonation.


    When you spoke to them did they say who much boost the system was designed for? They may have different pulley ratios but I am wondering how much with a stock CIS system.
     
  21. ferrariowner

    ferrariowner Formula Junior

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    Mike,
    I like boosted engines and wish you all the best. I have been running a hi boost turbo Ferrari engine for 20 years. I and others on this forum have learned some expensive lessons. I offer the following;
    • Stock Ferrari pistons have very thin/brittle compression rings that will break when you have detonation (if you make enough boost and run stock ignition timing, it will detonate)
    • I would not trust the crude K-jetronic system to deliver the proper fuel ratio under boost. There is no barometric or temp feedback sensors to adjust the fuel ratio under different atmospheric conditions. This too, will cause detonation.
    • Below is an effective compression chart for boosted engines (check the 9 to 1 line for a stock compression for a 308 engine) If you run just 6 PSI you will have an effective compression ratio of 12.7 to 1!!
    • Naturally aspirated engine compression ratios are not a good comparison. Compressed air is hot and much more likely to cause detonation.
    • If you have any doubts about what I am relaying to you, call the god father of Ferrari hot rodding,Bob Norwood
    • Good luck.
    • Image Unavailable, Please Login
     
  22. mike996

    mike996 F1 Veteran

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    #22 mike996, Nov 26, 2019
    Last edited: Nov 26, 2019
    Good info, thanks! Your points are one of the reasons I was concerned about the HP increase with 928 motosports unit.

    RifleD - I do not know the actual boost pressure they run; I didn't think to ask but the boost can be roughly calculated from the HP increase on their dyno chart. Basically, 15PSI of boost, assuming adequate fueling, will roughly double the HP; 5 Psi will produce around 30% more, 10 will produce around 65% more, etc. Their 130HP increase based on the stock HP would indicate around 10-11PSI. I have done a fair bit of forced induction work on US auto engines and would not be comfortable with more than 5 PSI on engines I am familiar with without an intercooler (and other possible engine/drivetrain mods). That's why I had the question re the power increase vs the OEM 3x8 components.
     
  23. Lawrence Coppari

    Lawrence Coppari Formula 3

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    A good formula for heating of air due to compression is: T2=T1 * (P2/P1)**.285. The double asterisk indication denotes exponentiation of the absolute pressure ratio. The .285 is specifically for air.
    Temperatures and pressures MUST be in absolute values. This is theoretical and comes from basic thermodynamics. Once I had a student at Road Atlanta who was an instrumentation engineer. He had a 944 turbo like mine so I was assigned as his instructor for the weekend. I think this was PCA but it could have been a BMWCCA driver school. The guy had everything instrumented on his car. Air/fuel ratio, pre-compressor temperature, post compressor temperature, pre-intercooler and post intercooler temperatures, fuel flow rate, exhaust temperature, pre and post compressor pressures, etc.. The driver's cabin looked like an operation process control center in a chemical plant. As a thermal analyst for a chemical company I thought it would be interesting to test out the above relation which is for isentropic compression of the ideal gas, air. So I jotted down readings at full boost while on the long back straightaway during full boost. Calculated results represented measured reading quite well.
     
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  24. ferrariowner

    ferrariowner Formula Junior

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    I log most of the same data as well. No time to look at it while driving:)
     
  25. jim rosenthal

    jim rosenthal Karting
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    You guys have successfully talked me out of a blower on my 308. I'm just going to get it running and drive the wheels off it... :)
     
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