carbureted 928?
01-06-2004, 04:39 PM
#31
Rennlist Member
Dont forget my part euro 5 liter with full US AFM system!!!! you say 200 to 230hp, try 293hp at the wheels (ie 350flywheel hp) and it was very reliable!! fuel metering was surpurb, with flat line ratios at 12:5:1 over the entire curve, and with only the use of a couple of regulators to bump the pressure from stock to 52psi. (just higher than S4 pressures)
so, yes, electronic FI is great. but remember, I was running that 293hp to the wheels out of that very restrictive smalll L jet barn door and opening!
find me a stock mustang 5 liter that put out that much even with a carburetor! And then also tell me why the 5 liter part euro boys with CIS are making close to the same hp and the MAF version 5 liters are putting out the close to the same, as well as the 4 valve , 4 cam, better intake, higher compression 5 liter S4 putting out only marginally more hp as well. (the Holbert car at 320ish rear wheel seems high vs most of the S4s with headers getting in the 305 range)
so, I would wonder what carbs would do on a stock S4!! Im sure it could be tuned to be very close to what we are seeing today. especially if what you say is true, that a carburetor is much beter than an Ljet system!!
Mk
so, yes, electronic FI is great. but remember, I was running that 293hp to the wheels out of that very restrictive smalll L jet barn door and opening!
find me a stock mustang 5 liter that put out that much even with a carburetor! And then also tell me why the 5 liter part euro boys with CIS are making close to the same hp and the MAF version 5 liters are putting out the close to the same, as well as the 4 valve , 4 cam, better intake, higher compression 5 liter S4 putting out only marginally more hp as well. (the Holbert car at 320ish rear wheel seems high vs most of the S4s with headers getting in the 305 range)
so, I would wonder what carbs would do on a stock S4!! Im sure it could be tuned to be very close to what we are seeing today. especially if what you say is true, that a carburetor is much beter than an Ljet system!!
Mk
Originally posted by Jim bailey - 928 International
Greg...."Tear off the carbs, put on a decent EFI system" I think that is a very accurate statement .....The initial question however was why put carbs on a 1984 USA 928 ? I think .... Tear off the L-jetronic , put on a decent set of carbs is equally accurate , especially with bigger cams and headers . The biggest problem people have with the carburetors is excessive heat boiling the fuel after shut down since the manifolds are so short and the carbs so close to the heads . No argument here ....Modern EFI is much superior to carbs ......point is L-jetronic 1980-1984 is far from modern or decent but does a good job making 200-230 HP ....... Robby Gordon's offroad Baja trophy truck has a unlimited NASCAR Roush Racing engine FUEL INJECTED and was said to make 950 HP ; easy 100 more than the normal carburated.....his race shop is one block down Mira Loma ave .
Greg...."Tear off the carbs, put on a decent EFI system" I think that is a very accurate statement .....The initial question however was why put carbs on a 1984 USA 928 ? I think .... Tear off the L-jetronic , put on a decent set of carbs is equally accurate , especially with bigger cams and headers . The biggest problem people have with the carburetors is excessive heat boiling the fuel after shut down since the manifolds are so short and the carbs so close to the heads . No argument here ....Modern EFI is much superior to carbs ......point is L-jetronic 1980-1984 is far from modern or decent but does a good job making 200-230 HP ....... Robby Gordon's offroad Baja trophy truck has a unlimited NASCAR Roush Racing engine FUEL INJECTED and was said to make 950 HP ; easy 100 more than the normal carburated.....his race shop is one block down Mira Loma ave .
01-07-2004, 02:40 AM
#32
Burning Brakes
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Jim,
I guess I would come down the middle on that one, I certainly agree that the factory US-Spec L-Jet was far from what I would characterize as "decent" given the current state-of-the-shelf.
I would also have to agree with Mark's findings that the 'barn door' system can be optimized to produce decent output - I'm also getting over 275 RWHP (yes on a dyno) out of a 4.7 on the (basically) stock USA L-Jet system. Yes, I do have mildly ported heads, and mildly uprated cams, and later model exhaust components. But the intake is still through the old flapper. It is a restriction, and I have a fix coming, but it still can put more out than one might think.
I just can't see spending all the $ for 4(!) 2 BBL Webers, making flanges, routing fuel lines, and then making the flippin' linkages synch (ugh), let alone tuning time - when you can "buff up" the factory L-Jet (or even upgrade it) for far less dinero.
But, sure, L-Jet is not exactly 'cutting edge' tech.
Greg
I guess I would come down the middle on that one, I certainly agree that the factory US-Spec L-Jet was far from what I would characterize as "decent" given the current state-of-the-shelf.
I would also have to agree with Mark's findings that the 'barn door' system can be optimized to produce decent output - I'm also getting over 275 RWHP (yes on a dyno) out of a 4.7 on the (basically) stock USA L-Jet system. Yes, I do have mildly ported heads, and mildly uprated cams, and later model exhaust components. But the intake is still through the old flapper. It is a restriction, and I have a fix coming, but it still can put more out than one might think.
I just can't see spending all the $ for 4(!) 2 BBL Webers, making flanges, routing fuel lines, and then making the flippin' linkages synch (ugh), let alone tuning time - when you can "buff up" the factory L-Jet (or even upgrade it) for far less dinero.
But, sure, L-Jet is not exactly 'cutting edge' tech.
Greg
01-07-2004, 03:47 PM
#33
Rennlist Member
wow, 275 with a 4.7. thats got to be somekind of record.
even with the small US valves???? (but better cam and ports?)
i had quite a few runs with my 5 liter in the 275 range after 2 seasons, and then the equal length headers got me back up to 285.
the AFM is restrictive, but its not because of the barn door. its because of its size. at 1.5 x 2" square it is like a retrictor plate. however, i think a MAF or CIS opening would only add 10hp or so.
MK
even with the small US valves???? (but better cam and ports?)
i had quite a few runs with my 5 liter in the 275 range after 2 seasons, and then the equal length headers got me back up to 285.
the AFM is restrictive, but its not because of the barn door. its because of its size. at 1.5 x 2" square it is like a retrictor plate. however, i think a MAF or CIS opening would only add 10hp or so.
MK
Originally posted by gbyron
Jim,
I guess I would come down the middle on that one, I certainly agree that the factory US-Spec L-Jet was far from what I would characterize as "decent" given the current state-of-the-shelf.
I would also have to agree with Mark's findings that the 'barn door' system can be optimized to produce decent output - I'm also getting over 275 RWHP (yes on a dyno) out of a 4.7 on the (basically) stock USA L-Jet system. Yes, I do have mildly ported heads, and mildly uprated cams, and later model exhaust components. But the intake is still through the old flapper. It is a restriction, and I have a fix coming, but it still can put more out than one might think.
I just can't see spending all the $ for 4(!) 2 BBL Webers, making flanges, routing fuel lines, and then making the flippin' linkages synch (ugh), let alone tuning time - when you can "buff up" the factory L-Jet (or even upgrade it) for far less dinero.
But, sure, L-Jet is not exactly 'cutting edge' tech.
Greg
Jim,
I guess I would come down the middle on that one, I certainly agree that the factory US-Spec L-Jet was far from what I would characterize as "decent" given the current state-of-the-shelf.
I would also have to agree with Mark's findings that the 'barn door' system can be optimized to produce decent output - I'm also getting over 275 RWHP (yes on a dyno) out of a 4.7 on the (basically) stock USA L-Jet system. Yes, I do have mildly ported heads, and mildly uprated cams, and later model exhaust components. But the intake is still through the old flapper. It is a restriction, and I have a fix coming, but it still can put more out than one might think.
I just can't see spending all the $ for 4(!) 2 BBL Webers, making flanges, routing fuel lines, and then making the flippin' linkages synch (ugh), let alone tuning time - when you can "buff up" the factory L-Jet (or even upgrade it) for far less dinero.
But, sure, L-Jet is not exactly 'cutting edge' tech.
Greg
01-08-2004, 02:37 AM
#34
Burning Brakes
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Originally posted by mark kibort
wow, 275 with a 4.7. thats got to be somekind of record.
even with the small US valves???? (but better cam and ports?)
i had quite a few runs with my 5 liter in the 275 range after 2 seasons, and then the equal length headers got me back up to 285.
the AFM is restrictive, but its not because of the barn door. its because of its size. at 1.5 x 2" square it is like a retrictor plate. however, i think a MAF or CIS opening would only add 10hp or so.
MK
wow, 275 with a 4.7. thats got to be somekind of record.
even with the small US valves???? (but better cam and ports?)
i had quite a few runs with my 5 liter in the 275 range after 2 seasons, and then the equal length headers got me back up to 285.
the AFM is restrictive, but its not because of the barn door. its because of its size. at 1.5 x 2" square it is like a retrictor plate. however, i think a MAF or CIS opening would only add 10hp or so.
MK
Might be a record, but I seriously doubt it. The fundamentals of the engine, even in 2v config, are pretty sound (esp considering the primitive design tools in use at the time - slide rules and calculators anyone?) the limitations of power are more about how Porsche made emissions than basic design flaws. That, and the current 'state of the shelf' is light years ahead of 20+ year old 'state of the art' when it comes to lotsa things automotive. I'd wager I'm not the only guy who knows what I know, and has done what I've done.
True, it's not really the door itself - IIRC, Bosch claims a loss of ~.17 PSIA from end to end of the meter, and my testing pretty well duplicated those results. You're right, it's the entrance (rectangular like a flippin' stone-age domestic INT/EX port) and the overall size of the passage. As well as the fact that every convolution in a manifold costs you flow speed, but I digress...
Besides, the RoW 4.7 was a 300+ BHP car, and there as more on the table, before they went 32v for emissions, maybe some TQ (and I'm sure "image" played a part as well). God knows, they really never got much more HP out of the 5.0L than the 4.7 until the GTS, and then only ~50. Hardly what they could've done, but that would've made the 911 look even more like the silly little uber-bug that it is...
In the next couple of months - spare time permitting - I think 300 RWHP is probably doable before the intake and blower go on. Then the starting goal becomes something north of 600 RWHP. There's really no reason not to get 800+ RWHP (force fed) if you set it up right. The flippin' Mustang Cobra guys are already getting it, and we have a bigger (and still superior) engine. If only saddled by some tech that ain't exactly leading edge anymore.
Right now, I have way too many projects in the que to start messing around with the order they are in. Oh well.
Greg
01-08-2004, 05:07 PM
#35
Rennlist Member
YOU GET IT!!!
Good to discuss with someone that knows the big picture.
anyway, good luck with the add ons. I also was pretty amazed that the euro 4.7s could make close to as much as the 5 liter 4 valvers, even with the second gen intake and bigger valves! Im sure with even bigger 2 valves and more attention paid to the intake runners and ports, as much or more hp could be seen. I wish, in someways, i had my old 2 valver around to do the bolt ons with you!!. heck, mine is one of the strongest 4 valvers around at 5 liter and it is still only in the 320 to 335 hp rear wheel range.
(with mistery cams! probably the 85 cams that were modified for the S4 if i was to guess looking at the numerology)
MK
Good to discuss with someone that knows the big picture.
anyway, good luck with the add ons. I also was pretty amazed that the euro 4.7s could make close to as much as the 5 liter 4 valvers, even with the second gen intake and bigger valves! Im sure with even bigger 2 valves and more attention paid to the intake runners and ports, as much or more hp could be seen. I wish, in someways, i had my old 2 valver around to do the bolt ons with you!!. heck, mine is one of the strongest 4 valvers around at 5 liter and it is still only in the 320 to 335 hp rear wheel range.
(with mistery cams! probably the 85 cams that were modified for the S4 if i was to guess looking at the numerology)
MK
Originally posted by gbyron
Mark,
Might be a record, but I seriously doubt it. The fundamentals of the engine, even in 2v config, are pretty sound (esp considering the primitive design tools in use at the time - slide rules and calculators anyone?) the limitations of power are more about how Porsche made emissions than basic design flaws. That, and the current 'state of the shelf' is light years ahead of 20+ year old 'state of the art' when it comes to lotsa things automotive. I'd wager I'm not the only guy who knows what I know, and has done what I've done.
True, it's not really the door itself - IIRC, Bosch claims a loss of ~.17 PSIA from end to end of the meter, and my testing pretty well duplicated those results. You're right, it's the entrance (rectangular like a flippin' stone-age domestic INT/EX port) and the overall size of the passage. As well as the fact that every convolution in a manifold costs you flow speed, but I digress...
Besides, the RoW 4.7 was a 300+ BHP car, and there as more on the table, before they went 32v for emissions, maybe some TQ (and I'm sure "image" played a part as well). God knows, they really never got much more HP out of the 5.0L than the 4.7 until the GTS, and then only ~50. Hardly what they could've done, but that would've made the 911 look even more like the silly little uber-bug that it is...
In the next couple of months - spare time permitting - I think 300 RWHP is probably doable before the intake and blower go on. Then the starting goal becomes something north of 600 RWHP. There's really no reason not to get 800+ RWHP (force fed) if you set it up right. The flippin' Mustang Cobra guys are already getting it, and we have a bigger (and still superior) engine. If only saddled by some tech that ain't exactly leading edge anymore.
Right now, I have way too many projects in the que to start messing around with the order they are in. Oh well.
Greg
Mark,
Might be a record, but I seriously doubt it. The fundamentals of the engine, even in 2v config, are pretty sound (esp considering the primitive design tools in use at the time - slide rules and calculators anyone?) the limitations of power are more about how Porsche made emissions than basic design flaws. That, and the current 'state of the shelf' is light years ahead of 20+ year old 'state of the art' when it comes to lotsa things automotive. I'd wager I'm not the only guy who knows what I know, and has done what I've done.
True, it's not really the door itself - IIRC, Bosch claims a loss of ~.17 PSIA from end to end of the meter, and my testing pretty well duplicated those results. You're right, it's the entrance (rectangular like a flippin' stone-age domestic INT/EX port) and the overall size of the passage. As well as the fact that every convolution in a manifold costs you flow speed, but I digress...
Besides, the RoW 4.7 was a 300+ BHP car, and there as more on the table, before they went 32v for emissions, maybe some TQ (and I'm sure "image" played a part as well). God knows, they really never got much more HP out of the 5.0L than the 4.7 until the GTS, and then only ~50. Hardly what they could've done, but that would've made the 911 look even more like the silly little uber-bug that it is...
In the next couple of months - spare time permitting - I think 300 RWHP is probably doable before the intake and blower go on. Then the starting goal becomes something north of 600 RWHP. There's really no reason not to get 800+ RWHP (force fed) if you set it up right. The flippin' Mustang Cobra guys are already getting it, and we have a bigger (and still superior) engine. If only saddled by some tech that ain't exactly leading edge anymore.
Right now, I have way too many projects in the que to start messing around with the order they are in. Oh well.
Greg
01-09-2004, 02:00 AM
#36
Burning Brakes
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Originally posted by mark kibort
YOU GET IT!!!
Good to discuss with someone that knows the big picture.
anyway, good luck with the add ons. I also was pretty amazed that the euro 4.7s could make close to as much as the 5 liter 4 valvers, even with the second gen intake and bigger valves! Im sure with even bigger 2 valves and more attention paid to the intake runners and ports, as much or more hp could be seen. I wish, in someways, i had my old 2 valver around to do the bolt ons with you!!. heck, mine is one of the strongest 4 valvers around at 5 liter and it is still only in the 320 to 335 hp rear wheel range.
(with mistery cams! probably the 85 cams that were modified for the S4 if i was to guess looking at the numerology)
MK
YOU GET IT!!!
Good to discuss with someone that knows the big picture.
anyway, good luck with the add ons. I also was pretty amazed that the euro 4.7s could make close to as much as the 5 liter 4 valvers, even with the second gen intake and bigger valves! Im sure with even bigger 2 valves and more attention paid to the intake runners and ports, as much or more hp could be seen. I wish, in someways, i had my old 2 valver around to do the bolt ons with you!!. heck, mine is one of the strongest 4 valvers around at 5 liter and it is still only in the 320 to 335 hp rear wheel range.
(with mistery cams! probably the 85 cams that were modified for the S4 if i was to guess looking at the numerology)
MK
It's all about modern systems and management. The 4v heads are ok, but they need a modern - not cousin Fred's - serious port and flow job. The intake is a serious compromise and desperately needs an updated replacement. Threshie's intake seems neat, but the price tag is reflective of the methodology and constraints he (apparently) imposed on himself in the design process.
LH2 for all it's goodness (and it's still not quite dustbin tech which IS impressive for the age of the system) is not user definable, and 'piggyback' systems are a rigjob at best. It needs more modern management - and it's available for an acceptable price point. Too many vacuum ports to leak, lotsa compromises.
Fuel system also has it's opportunities. Piston design could be better.
10 HP here, 20 HP there, eventually it does add up.
Gotta love those mystery cams....
There's a list of products that I'm working on, but the development is currently focused in the 2v realm - 4v stuff is down on the list a bit.
Greg
