My "Supermodel928" runs 13.3/105 and 0-60 in 4.8sec
02-28-2005, 01:31 PM
#46
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I'm not convinced that the issue is life/reliability of the injector. I think it is accuracy of fuel delivery. That is, "they" recommend that you run no more than 80% duty cycle to give an allowance for engine at low temps (need more injector time that hot) and so on.
You need some margins in a system to work with. Although most s/c cars are being individually tuned for A/F, so some of the normal deisgn rules don't apply.
You need some margins in a system to work with. Although most s/c cars are being individually tuned for A/F, so some of the normal deisgn rules don't apply.
02-28-2005, 02:13 PM
#47
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John,
I agree with your observation and points.. I also think that the BSFC of the engines can differ, and can be better than .45 NA, and .55 FA as many have quoted from Corky Bell's book... In addition, if you look at the timing, and RPM, you can equate the duty cycle of the injector to a function of time. So, once the RPM goes above a certain amount, the injector has no choice but TO STAY OPEN due to the time it takes for 1 CRANKSHAFT Revolution. This will be measured in MILLISECONDS, and unless the ECU has this bandwidth, and the ability to open and close the injectors faster than the open time requirement based on RPM, it will not matter... At lower RPM's, it will be a function of the perceived LOAD as stored in the fuel map tables....
Some of us may have forgotten what Duty Cycle really is in the way it relates to the engine's operation... The injector will not fail from being open all the time. The wear rate is more related to the Opening/Closing cycles in total... Full Open is just that, the nozzle is open so the fuel flow goes through..
I think some 928 engines in NA form can run as good as .41 BSFC or better.. When boosted, they can use smaller injectors with bumped fuel pressure to "overdrive" the injector for that higher fuel requirement.. It depends on the state and tune of the engine..... It is possible to calculate the BSFC.. I believe that at the 275 RWHP mark, using stock 19# injectors the S4 engine is at .41 BSFC I could be off, but I think this was the calculated amount when I ran the numbers the last time.
I guess I'm beginning to sound like MK... The real answer, is always: "It depends..."
I agree with your observation and points.. I also think that the BSFC of the engines can differ, and can be better than .45 NA, and .55 FA as many have quoted from Corky Bell's book... In addition, if you look at the timing, and RPM, you can equate the duty cycle of the injector to a function of time. So, once the RPM goes above a certain amount, the injector has no choice but TO STAY OPEN due to the time it takes for 1 CRANKSHAFT Revolution. This will be measured in MILLISECONDS, and unless the ECU has this bandwidth, and the ability to open and close the injectors faster than the open time requirement based on RPM, it will not matter... At lower RPM's, it will be a function of the perceived LOAD as stored in the fuel map tables....
Some of us may have forgotten what Duty Cycle really is in the way it relates to the engine's operation... The injector will not fail from being open all the time. The wear rate is more related to the Opening/Closing cycles in total... Full Open is just that, the nozzle is open so the fuel flow goes through..
I think some 928 engines in NA form can run as good as .41 BSFC or better.. When boosted, they can use smaller injectors with bumped fuel pressure to "overdrive" the injector for that higher fuel requirement.. It depends on the state and tune of the engine..... It is possible to calculate the BSFC.. I believe that at the 275 RWHP mark, using stock 19# injectors the S4 engine is at .41 BSFC I could be off, but I think this was the calculated amount when I ran the numbers the last time.
I guess I'm beginning to sound like MK... The real answer, is always: "It depends..."
02-28-2005, 02:21 PM
#48
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.".... So, once the RPM goes above a certain amount, the injector has no choice but TO STAY OPEN due to the time it takes for 1 CRANKSHAFT Revolution...."
hi Richard,
I would qualify this by saying that it not only depends on rpm, but also throttle position - MAF volts - "load". But all your points taken...
All I can say about these s/c cars is - I WANT ONE !!
Regards
hi Richard,
I would qualify this by saying that it not only depends on rpm, but also throttle position - MAF volts - "load". But all your points taken...
All I can say about these s/c cars is - I WANT ONE !!
Regards
02-28-2005, 02:24 PM
#49
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"Fuel injector expert Russ Collins says injectors can begin to fibrillate at more than 80%dc causing fuel delivery to become nonlinear in fuel delivery and causing lean out problems."
There is another section that has a Bosch injector designerdude saying the same thing. Actually the Bosch guy states that staying open cause total failure, not just lean out problems.
I am not trying to be disagreeable but from what I have read...
Some of us may have forgotten what Duty Cycle really is in the way it relates to the engine's operation... The injector will not fail from being open all the time. The wear rate is more related to the Opening/Closing cycles in total... Full Open is just that, the nozzle is open so the fuel flow goes through..
I
There is another section that has a Bosch injector designerdude saying the same thing. Actually the Bosch guy states that staying open cause total failure, not just lean out problems.
I am not trying to be disagreeable but from what I have read...
Originally Posted by blau928
Some of us may have forgotten what Duty Cycle really is in the way it relates to the engine's operation... The injector will not fail from being open all the time. The wear rate is more related to the Opening/Closing cycles in total... Full Open is just that, the nozzle is open so the fuel flow goes through..
I
02-28-2005, 02:31 PM
#50
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John,
I agree with you, as you can see from my prior statement....
Jim,
It is quite acceptable to me to be disagreed with.. I do not know it all, and will never be able to learn enough about this stuff in my lifetime..... I think the more info we have, the better off we are in making informed, educated decisions, and analysis.
Cheers,
I agree with you, as you can see from my prior statement....
At lower RPM's, it will be a function of the perceived LOAD as stored in the fuel map tables....
It is quite acceptable to me to be disagreed with.. I do not know it all, and will never be able to learn enough about this stuff in my lifetime..... I think the more info we have, the better off we are in making informed, educated decisions, and analysis.
I am not trying to be disagreeable but from what I have read...
Cheers,
02-28-2005, 02:33 PM
#51
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Interesting info ! But there are injectors and injectors, driven by several generations of ECUs. Later ECUs, incluuding S4 onwards, limit the holding curreent into the injectors, once they have opened, this must help life.
I guess they did this because of the life problem you read about ?
I guess they did this because of the life problem you read about ?
02-28-2005, 03:07 PM
#52
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the 84 injectors are higher flow rate than the S4?? thats interesting. yes, the stock fuel pressure for the 84 is in the 30psi range. I bumped it up over a 4 year period of mods to 53psi and got the 293hp at the rears. havent checked my S4 fuel pressure yet, but as you know, its in the 320+hp range with a fuel regulator with several turns richer. I would have to imagine that it is in the mid 50s (psi) for sure.
I know Anderson was spitting rich for a while with his car until he was able to back off the pressure from his big injectors. now, at 485 rear wheel hp, he is in the right mixture range and still had some rich issues, that his new 4" tube, with stock donated maf sensor seemed to fix.
mk
I know Anderson was spitting rich for a while with his car until he was able to back off the pressure from his big injectors. now, at 485 rear wheel hp, he is in the right mixture range and still had some rich issues, that his new 4" tube, with stock donated maf sensor seemed to fix.
mk
Originally Posted by GoRideSno
The S4 has 19# injectors but idle fuel pressure is 57 v/s 43.5 (at which injectors are measured) so they act like 22# injectors. 80-84 cars have 24# injectors (low Z though). I can't recall the pressure off the top of my head.
Thanks Mark, exactly what I thought. And exactly what I suggest for setups that are making 400rwhp and below for S4. Above that need to have the BEGI2025 reg.
Andy K
Thanks Mark, exactly what I thought. And exactly what I suggest for setups that are making 400rwhp and below for S4. Above that need to have the BEGI2025 reg.
Andy K
02-28-2005, 05:38 PM
#53
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Originally Posted by Jim_H
I am not trying to be disagreeable but from what I have read...
03-01-2005, 08:19 PM
#56
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that is so cool!!
do you know if anyone has this kind of data for a 5 speed?
plus, how much does a system like this cost. It would be cool to get some data off the track!
MK
do you know if anyone has this kind of data for a 5 speed?
plus, how much does a system like this cost. It would be cool to get some data off the track!
MK
Originally Posted by Tony
I went to the drag strip last night here in Vegas. In a nut shell these are my 3 time slips and and a screen shot of the GTEC showing a 0-60 run that coincided with timeslip #2
Ill have more later inlcuding video
(Thanks Bill 
) as im litterally out the door to help Darien with a timing belt change. I just wanted to get this posted. Im pretty F-N happy with it!. With some work i may be able to get 13.0....but we know how hard those last 10ths are to get. With drag radials i know i could do it, as again, i left a little time in the 1st 60ft 
Car was ran as driven on the street, pump gas and street tires, however i did drop the tire pressure to 20psi on my 18" wheels.
I got lots of on the car, including the sound. People were generally amazed that its an 87 with 151,000 miles!!
more to come later
....and BTW, no $hit about my RT in #1.
They installed a new set of lights at the strip for these "Midnight Mayhem" sessions. They are basically a set of trafic lights...but on the first runs, no one really knew how to stage or run them...
Theis GTECH runs corresdonds with run #2 for reference. It shows that the device is pretty acurate overall...with in 1mph and 1/10thsec
Ill have more later inlcuding video
(Thanks Bill ) as im litterally out the door to help Darien with a timing belt change. I just wanted to get this posted. Im pretty F-N happy with it!. With some work i may be able to get 13.0....but we know how hard those last 10ths are to get. With drag radials i know i could do it, as again, i left a little time in the 1st 60ft Car was ran as driven on the street, pump gas and street tires, however i did drop the tire pressure to 20psi on my 18" wheels.
I got lots of
on the car, including the sound. People were generally amazed that its an 87 with 151,000 miles!!more to come later
....and BTW, no $hit about my RT in #1.
They installed a new set of lights at the strip for these "Midnight Mayhem" sessions. They are basically a set of trafic lights...but on the first runs, no one really knew how to stage or run them... Theis GTECH runs corresdonds with run #2 for reference. It shows that the device is pretty acurate overall...with in 1mph and 1/10thsec