FAST Supercharged 928
07-02-2002, 06:07 PM
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FAST Supercharged 928
Hello gang,
I was just wondering if anybody has any thoughts to this product for our sharks. I am itching for more power out of my shark, and it seems like supercharging seems like the route to go. I've heard from people that a supercharger compromises the engine life of the vehicle. Roughly how long of an install would it be and what would the installation costs be roughly, as I am not mechanically incline? I know I should be asking these questions to the people at FAST, but I wanted to hear from fellow owners who may have already done it or just someone's two cents worth. Much appreciated.
Ed
85 928s Auto
White/Burgandy
I was just wondering if anybody has any thoughts to this product for our sharks. I am itching for more power out of my shark, and it seems like supercharging seems like the route to go. I've heard from people that a supercharger compromises the engine life of the vehicle. Roughly how long of an install would it be and what would the installation costs be roughly, as I am not mechanically incline? I know I should be asking these questions to the people at FAST, but I wanted to hear from fellow owners who may have already done it or just someone's two cents worth. Much appreciated.
Ed
85 928s Auto
White/Burgandy
07-02-2002, 06:28 PM
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Last I heard (this was a few years ago) Devek International was working on a supercharger for the 928. I was told that they had a prototype in one of their cars but it was still early in development. Maybe they've gotten closer to a finished design.
I have heard that supercharging causes many issues in the 928 as it has, already, an extremely complex engine.
I've heard speculation that such a modification could cost anywhere from $6000 to $10,000.
I have heard that supercharging causes many issues in the 928 as it has, already, an extremely complex engine.
I've heard speculation that such a modification could cost anywhere from $6000 to $10,000.
07-03-2002, 02:27 AM
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<a href="http://www.projekt928.com/" target="_blank">http://www.projekt928.com/</a>
<a href="http://www.supercharged928.com/" target="_blank">http://www.supercharged928.com/</a> <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
<a href="http://www.supercharged928.com/" target="_blank">http://www.supercharged928.com/</a> <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
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07-06-2002, 06:19 PM
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That kit has supposedly been in development for like 2 years or something, according to the 944 board. There is a shop near where i live that will do a supercharger for me for about 5,000 including a custom built intercooler and custom pullleys and brackets, we are just trying to figure out how to do it with out standalone engine managment. But sinec I have an 84 i have to convert to MAF.
07-07-2002, 06:45 PM
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Well I have decided on a<a href="http://www.sdsefi.com" target="_blank">sds</a> engine managment system with bigger injectors. A vortech supercharger since that z-enginerring place wont respond back to me. I am looking for another one that a company called Area 51 makes but i cant find them either. I am only going to run 8pnds of boost.
07-08-2002, 04:26 PM
#11
[quote]Originally posted by lobis:
<strong>we are just trying to figure out how to do it with out standalone engine managment. But sinec I have an 84 i have to convert to MAF.</strong><hr></blockquote>
There are two supercharged 928s in our local group. One is an '88 and the other a '78 Euro. Neither one has a stand alone engine management system on it. The '88 uses all stock engine management, and uses changes in fuel pressure to tune the mixture. The '78 uses the stock CIS system. The '88 was making 410hp on the dyno before larger fuel injectors were put in, and according to a G-Tech the '78 makes around 360hp. Both of them will be putting on intercoolers in the near future. The '88 makes 9 psi of boost, and the '78 11 psi.
<strong>we are just trying to figure out how to do it with out standalone engine managment. But sinec I have an 84 i have to convert to MAF.</strong><hr></blockquote>
There are two supercharged 928s in our local group. One is an '88 and the other a '78 Euro. Neither one has a stand alone engine management system on it. The '88 uses all stock engine management, and uses changes in fuel pressure to tune the mixture. The '78 uses the stock CIS system. The '88 was making 410hp on the dyno before larger fuel injectors were put in, and according to a G-Tech the '78 makes around 360hp. Both of them will be putting on intercoolers in the near future. The '88 makes 9 psi of boost, and the '78 11 psi.
07-09-2002, 12:27 PM
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Hi Mike,
Idle (for now) curiosity here:
I remember some discussion at last year's SITM on SC cars running rich and why (without any conclusion). Why wouldn't the standard LH/MAF be able to control the mixture w/o resorting to higher fuel pressures? I know one reason for raising the pressure is to get sufficient fuel but I assume heavier injectors could do this alone? I'm a novice on LH systems but thought that the combination of the MAF and injector "open" timing(even w heavier injectors) from the LH would allow the brain to control the mixture w feedback from the OXS...or is the opening time pre-programmed to correspond w load and MAF readings and not a function of OXS readings? I assume that minimum injector open times could give you a rich condition at low rpm/load if you upped the pressure/had larger injectors but don't recall if Randy was running rich across the board or just at low load.
Just trying to understand why additional engine management is required. Did Randy ever figure out why he was running rich on his car (FAST SC w intercooler). If anyone has a good source of tutorial info that would help explain this, I'd appreciate it. I've got the Bosche Fuel Inj and Engine Mgmnt book but have to admit I haven't done more than a quick read on the LH since my '82 is AFC.
Jim
Idle (for now) curiosity here:
I remember some discussion at last year's SITM on SC cars running rich and why (without any conclusion). Why wouldn't the standard LH/MAF be able to control the mixture w/o resorting to higher fuel pressures? I know one reason for raising the pressure is to get sufficient fuel but I assume heavier injectors could do this alone? I'm a novice on LH systems but thought that the combination of the MAF and injector "open" timing(even w heavier injectors) from the LH would allow the brain to control the mixture w feedback from the OXS...or is the opening time pre-programmed to correspond w load and MAF readings and not a function of OXS readings? I assume that minimum injector open times could give you a rich condition at low rpm/load if you upped the pressure/had larger injectors but don't recall if Randy was running rich across the board or just at low load.
Just trying to understand why additional engine management is required. Did Randy ever figure out why he was running rich on his car (FAST SC w intercooler). If anyone has a good source of tutorial info that would help explain this, I'd appreciate it. I've got the Bosche Fuel Inj and Engine Mgmnt book but have to admit I haven't done more than a quick read on the LH since my '82 is AFC.
Jim
07-09-2002, 02:37 PM
#13
Hi Jim,
Not all supercharged cars are necessarily running rich. It depends on what fuel modifications have been done, and how they've been tuned. The stock LH and MAF can control the mixture, but only at part throttle. The information from the O2 sensor is used by the LH to adjust the mixture, but at full throttle the LH ignores the O2 sensor, and uses only the airflow information from the MAF. It uses the information programmed into the full throttle maps in the chips to determine the injector pulse time for the volume of air going through the MAF. At full throttle the LH doesn't know what the mixture really is. It just knows to fire the injectors the programmed length of time for the particular airflow signal it's getting from the MAF. If you put in larger injectors, the LH doesn't know it at full throttle, and will pulse the injectors for the same length of time as it would the stock smaller ones. You'd have more fuel flow at full throttle then. Depending on how large the injectors are, and how much fuel you want, you could adjust the fuel pressure either higher or lower. At part throttle the LH would again adjust the injector pulse time based on information from the O2 sensor. If you have the larger injectors in, the LH would know it and shorten the injector pulse time to get the mixture back where it's supposed to be.
I don't remember the specifics of Randy's car running rich, but I know that he did make some fuel pressure adjustments for full throttle since then. Unless the new injectors are a lot larger than stock, or the fuel pressure is a lot higher than stock, the LH, MAF, and O2 sensor should be able to handle the part throttle mixture adjustment. If not, it's usually caused by a problem not directly related to installing the larger injectors, like a bad MAF or O2 sensor. If an extreme increase in injector size or fuel pressure is made at part throttle, there may be problems because the injector pulse time would need to be shortened too much. Injectors don't work properly if that pulse time is too short, or the LH might not even be able to provide a pulse time that short.
Not all supercharged cars are necessarily running rich. It depends on what fuel modifications have been done, and how they've been tuned. The stock LH and MAF can control the mixture, but only at part throttle. The information from the O2 sensor is used by the LH to adjust the mixture, but at full throttle the LH ignores the O2 sensor, and uses only the airflow information from the MAF. It uses the information programmed into the full throttle maps in the chips to determine the injector pulse time for the volume of air going through the MAF. At full throttle the LH doesn't know what the mixture really is. It just knows to fire the injectors the programmed length of time for the particular airflow signal it's getting from the MAF. If you put in larger injectors, the LH doesn't know it at full throttle, and will pulse the injectors for the same length of time as it would the stock smaller ones. You'd have more fuel flow at full throttle then. Depending on how large the injectors are, and how much fuel you want, you could adjust the fuel pressure either higher or lower. At part throttle the LH would again adjust the injector pulse time based on information from the O2 sensor. If you have the larger injectors in, the LH would know it and shorten the injector pulse time to get the mixture back where it's supposed to be.
I don't remember the specifics of Randy's car running rich, but I know that he did make some fuel pressure adjustments for full throttle since then. Unless the new injectors are a lot larger than stock, or the fuel pressure is a lot higher than stock, the LH, MAF, and O2 sensor should be able to handle the part throttle mixture adjustment. If not, it's usually caused by a problem not directly related to installing the larger injectors, like a bad MAF or O2 sensor. If an extreme increase in injector size or fuel pressure is made at part throttle, there may be problems because the injector pulse time would need to be shortened too much. Injectors don't work properly if that pulse time is too short, or the LH might not even be able to provide a pulse time that short.
07-09-2002, 05:22 PM
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great explanation, thanks Mike. So you could probably get 'tuned in' by doing a dyno run and adjusting the fuel pressure to optimize the mixture. Now I see why an earlier thread was discussing the use of the Dastek...the piggyback computer could take care of the full throttle adjustments, right?
take care. I'll be in your neck of the woods the week of August 5, maybe we can meet up for a beer.
Jim
take care. I'll be in your neck of the woods the week of August 5, maybe we can meet up for a beer.
Jim
07-09-2002, 05:55 PM
#15
The Dastek is able to adjust the full throttle mixture. It intercepts the signal from the MAF, and allows you to modify that signal before it goes to the LH. If you tune the Dastek to increase the voltage from the MAF to the LH at a particular RPM point, the LH will think that there's actually more air going into the engine than there really is. The LH makes the mixture richer by lengthening the pulse width of the injectors to what the full throttle maps say is needed for the airflow that the LH thinks is occuring. The mixture is made leaner by tuning the Dastek to reduce the voltage signal from the MAF to the LH. The direction and amount of mixture change can be set differently at different RPM points over the engine's range.
I'm not sure yet, but I may be out at Devek Day for at least part of that week. Let me know if and when you're going to be around though.
I'm not sure yet, but I may be out at Devek Day for at least part of that week. Let me know if and when you're going to be around though.
