Do not use the in-tank pump... EVER
07-13-2015, 05:00 PM
#91
Rennlist Member
Jim,
As someone who has run a 928 in a hot climate for some 16 years now this only confirms what I have espoused for quite some time. On our modest auto cross events I would run with as much weight removed as practical and also with the a/c switched off but if my fuel tank was down to about 1/3 full it would stutter and cut out under hard acceleration out of bends and reduces the cover over the pump inlet. Similarly if I was on longer runs and in mid summer I used to dread stopping at gas stations as I could guarantee the thing would not start unless I opened the bonnet and let things cool off for ten minutes or so and this with an "in tank" pump fitted -ambient conditions in the region of 45C [113F].
With pumps in series the primary pump has to have a significant increment of capacity to ensure the main pump remains primed so your numbers make sense [I could find no data for the in tank pump] and the head is about what I might expect- just enough to get the fluid into the main pump.
It certainly surprises me when I hear of folks running the 044 pump [more capacity] through the same size inlet [?] without an in tank pump. It would be interesting to know if the in tank pump has enough capacity to feed the 044- I suspect it might be big enough.
I guess it all depends on how close to the limit folks are running their systems. Petrol is a multi component system and unlike a pure component that has a specific boiling point, gasoline blends have what we call a boiling point range. In winter time more lighter components can be in the blend to help it vaporise/atomise at the lower winter temps. I do not know the US specs but generally refiners try to keep the blend with component boiling points as close to ambient as possible so that they can maximise production. Presumably fuel injected systems that recycle fuel created a problem in that the fuel heats up as it runs through the engine bay- thus why the fuel runs through the cooler the logic being that you will run the a/c in hotter ambients. I cannot even remember what happened to the fuel in my carburretor cars that I used to play around with in the 70's/80's.
It is not difficult to understand. Short of mounting the fuel tank on the roof there is no practical solution to this dilemma other than direct injection which [as far as I know] does not recirculate fuel.
Because of the above I would not vaguely consider ditching my in tank pump in our climate- maybe different if I was in the UK but each to his own of course.
Rgds
Fred
As someone who has run a 928 in a hot climate for some 16 years now this only confirms what I have espoused for quite some time. On our modest auto cross events I would run with as much weight removed as practical and also with the a/c switched off but if my fuel tank was down to about 1/3 full it would stutter and cut out under hard acceleration out of bends and reduces the cover over the pump inlet. Similarly if I was on longer runs and in mid summer I used to dread stopping at gas stations as I could guarantee the thing would not start unless I opened the bonnet and let things cool off for ten minutes or so and this with an "in tank" pump fitted -ambient conditions in the region of 45C [113F].
With pumps in series the primary pump has to have a significant increment of capacity to ensure the main pump remains primed so your numbers make sense [I could find no data for the in tank pump] and the head is about what I might expect- just enough to get the fluid into the main pump.
It certainly surprises me when I hear of folks running the 044 pump [more capacity] through the same size inlet [?] without an in tank pump. It would be interesting to know if the in tank pump has enough capacity to feed the 044- I suspect it might be big enough.
I guess it all depends on how close to the limit folks are running their systems. Petrol is a multi component system and unlike a pure component that has a specific boiling point, gasoline blends have what we call a boiling point range. In winter time more lighter components can be in the blend to help it vaporise/atomise at the lower winter temps. I do not know the US specs but generally refiners try to keep the blend with component boiling points as close to ambient as possible so that they can maximise production. Presumably fuel injected systems that recycle fuel created a problem in that the fuel heats up as it runs through the engine bay- thus why the fuel runs through the cooler the logic being that you will run the a/c in hotter ambients. I cannot even remember what happened to the fuel in my carburretor cars that I used to play around with in the 70's/80's.
It is not difficult to understand. Short of mounting the fuel tank on the roof there is no practical solution to this dilemma other than direct injection which [as far as I know] does not recirculate fuel.
Because of the above I would not vaguely consider ditching my in tank pump in our climate- maybe different if I was in the UK but each to his own of course.
Rgds
Fred
07-13-2015, 05:31 PM
#92
Ethanol.
Ethanol separates and settles in the gas station tank also. It might have been 10% Eth going INTO the gas station tank, but coming out, no one knows but your engine. 20%? 25%? 28%? Somewhere the line was crossed, and when you stopped, it was all she wrote for that day. Of course, you could have just let it spray hot gas everywhere, and reduce the pressure in the line, then climb under and spray the pump with cool water from your cooler for a while until it built up pressure. Ask me how I know...
Ethanol separates and settles in the gas station tank also. It might have been 10% Eth going INTO the gas station tank, but coming out, no one knows but your engine. 20%? 25%? 28%? Somewhere the line was crossed, and when you stopped, it was all she wrote for that day. Of course, you could have just let it spray hot gas everywhere, and reduce the pressure in the line, then climb under and spray the pump with cool water from your cooler for a while until it built up pressure. Ask me how I know...
However, a couple of things so we stay on facts instead of sheer speculation.
1) To separate, the fluid would need to be still. Commercial gas station tanks are not still - they are consistently pumped (on purpose).
2) Even at E15, while there is a difference in V/L ratios, they are not great enough to cause issues and have the ETOH be blamed. http://www.gmcmhphotos.com/photos/da..._pressure_.pdf
3) No where has it been found, noticed, or seen that an E10 pump will pump out E25. It simply does not happen.
Lastly - Ethanol is here to stay. Argue as you will about its source materials, but what else will they increase the octane with do you think? Toluene? Carcinogen. MTBE? Already known to be horrible. Lead?
Replace hoses with Flouro elastomer (Such as 30R9 ) and you are fine there.
*********
As I understand, this fuel heating issue is most of the reason for returnless (which are not really returnless - it just has an intank FPR and relief) fuel systems.
07-13-2015, 05:53 PM
#93
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However, a couple of things so we stay on facts instead of sheer speculation.
1) To separate, the fluid would need to be still. Commercial gas station tanks are not still - they are consistently pumped (on purpose).
2) Even at E15, while there is a difference in V/L ratios, they are not great enough to cause issues and have the ETOH be blamed. http://www.gmcmhphotos.com/photos/da..._pressure_.pdf
3) No where has it been found, noticed, or seen that an E10 pump will pump out E25. It simply does not happen.
1) To separate, the fluid would need to be still. Commercial gas station tanks are not still - they are consistently pumped (on purpose).
2) Even at E15, while there is a difference in V/L ratios, they are not great enough to cause issues and have the ETOH be blamed. http://www.gmcmhphotos.com/photos/da..._pressure_.pdf
3) No where has it been found, noticed, or seen that an E10 pump will pump out E25. It simply does not happen.
2. Then why do mfgs limit engines to 10% Eth and deny warranty, etc for E15? E20? E25? Did you look at your own link? jeez. More bullspit
3. You haven't found it, is not exhaustive. Being that I test every load of pure gas for my airplane, I've gotten samples that were way over E10. If you want to come down to TX and see my results I'll be happy to share them with you. This goes back to 1, you have NO IDEA what rural gas stations do with their tanks. I've also seen cases where an entire truck load of fuel had to be condemned from the blender because they made a mistake with the Eth blend.
Notwithstanding that the 928 was sold way before there was ANY Eth in fuel. Even at E10, it's a crap shoot.
http://www.usatoday.com/story/money/...gines/1873733/
http://www.snopes.com/politics/gasoline/e15.asp
http://newsroom.aaa.com/2012/11/new-...mer-confusion/
Need I go on? You're selling, I'm not buying.
07-13-2015, 06:13 PM
#94
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Those SoCal residents who lived through late 70's and early 80's CIS cars of any flavor know these symptoms well, good or bad. Cali started some interesting fuel blending efforts with the mythical goal of reducing CO2 emissions by adding "oxygenates" to the fuel, and somehow reducing the load on catalytic converters. The additives like $MTBE$ and later $$ethanol$$ (sorry BC...) helped reduce CO emissions on a per pound of fuel consumed basis, in cars that had tired catalysts. It did nothing for the emissions per mile since it takes more pounds of fuel per mile. But the net was low-boiling fuel blends really didn't do well in hot-soak conditions.
The fuel pumps and fuel boiling saga showed up at about the same time. Folks driving premium BMW and M-B sedans found themselves stalled in freeway traffic that wasn't quite as stalled. Folks were not happy! So Bosch joined in the problem/discussion that afflicted a significant portion of their market. The combination of fuel temperature management via the fuel cooler in the AC, with the first-stage pump inside the tank, was the solution they chose.
Cross back to US-made cars of the same period that potentially had the same issues. For several reasons, US manufacturers took the path of adding the fuel pump to the bottom of the fuel level sensor assembly, and dropping that into the tank so the pump could sit submerged in fuel at the bottom. Suddenly no issues with leaking or frozen fittings sitting below the normal fuel level. Fittings that aren't there won't leak, it turns out. No restrictions except a long nylon screen filter sock. The head fitting (one...) is typically a sandwich fitting that clamps the top of the tank, and the whole thing is serviced from an access port in the trunk or under the rear deck on passenger cars. In my opinion, this is one area where Porsche could easily have learned from the 'murikans. Also the Swedes and some 'other' European branches of the American companies.
The fuel pumps and fuel boiling saga showed up at about the same time. Folks driving premium BMW and M-B sedans found themselves stalled in freeway traffic that wasn't quite as stalled. Folks were not happy! So Bosch joined in the problem/discussion that afflicted a significant portion of their market. The combination of fuel temperature management via the fuel cooler in the AC, with the first-stage pump inside the tank, was the solution they chose.
Cross back to US-made cars of the same period that potentially had the same issues. For several reasons, US manufacturers took the path of adding the fuel pump to the bottom of the fuel level sensor assembly, and dropping that into the tank so the pump could sit submerged in fuel at the bottom. Suddenly no issues with leaking or frozen fittings sitting below the normal fuel level. Fittings that aren't there won't leak, it turns out. No restrictions except a long nylon screen filter sock. The head fitting (one...) is typically a sandwich fitting that clamps the top of the tank, and the whole thing is serviced from an access port in the trunk or under the rear deck on passenger cars. In my opinion, this is one area where Porsche could easily have learned from the 'murikans. Also the Swedes and some 'other' European branches of the American companies.
07-13-2015, 06:20 PM
#95
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Those SoCal residents who lived through late 70's and early 80's CIS cars of any flavor know these symptoms well, good or bad.
The head fitting (one...) is typically a sandwich fitting that clamps the top of the tank, and the whole thing is serviced from an access port in the trunk or under the rear deck on passenger cars. In my opinion, this is one area where Porsche could easily have learned from the 'murikans. Also the Swedes and some 'other' European branches of the American companies.
The head fitting (one...) is typically a sandwich fitting that clamps the top of the tank, and the whole thing is serviced from an access port in the trunk or under the rear deck on passenger cars. In my opinion, this is one area where Porsche could easily have learned from the 'murikans. Also the Swedes and some 'other' European branches of the American companies.
Here's the solution to repl the in-tank pump in a Ford Focus(if you are squeamish about body cutting, don't watch)
07-13-2015, 06:26 PM
#96
1. Every gas station? All the time? Bullspit.
2. Then why do mfgs limit engines to 10% Eth and deny warranty, etc for E15? E20? E25? Did you look at your own link? jeez. More bullspit
3. You haven't found it, is not exhaustive. Being that I test every load of pure gas for my airplane, I've gotten samples that were way over E10. If you want to come down to TX and see my results I'll be happy to share them with you. This goes back to 1, you have NO IDEA what rural gas stations do with their tanks. I've also seen cases where an entire truck load of fuel had to be condemned from the blender because they made a mistake with the Eth blend.
Notwithstanding that the 928 was sold way before there was ANY Eth in fuel. Even at E10, it's a crap shoot.
http://www.usatoday.com/story/money/...gines/1873733/
http://www.snopes.com/politics/gasoline/e15.asp
http://newsroom.aaa.com/2012/11/new-...mer-confusion/
Need I go on? You're selling, I'm not buying.
2. Then why do mfgs limit engines to 10% Eth and deny warranty, etc for E15? E20? E25? Did you look at your own link? jeez. More bullspit
3. You haven't found it, is not exhaustive. Being that I test every load of pure gas for my airplane, I've gotten samples that were way over E10. If you want to come down to TX and see my results I'll be happy to share them with you. This goes back to 1, you have NO IDEA what rural gas stations do with their tanks. I've also seen cases where an entire truck load of fuel had to be condemned from the blender because they made a mistake with the Eth blend.
Notwithstanding that the 928 was sold way before there was ANY Eth in fuel. Even at E10, it's a crap shoot.
http://www.usatoday.com/story/money/...gines/1873733/
http://www.snopes.com/politics/gasoline/e15.asp
http://newsroom.aaa.com/2012/11/new-...mer-confusion/
Need I go on? You're selling, I'm not buying.
I don't need or want to sell your kind anything.
Its already been bought by your country as a solution to contaminated ground water, carcinogen creation, and other sundries. Deal with it. E15 will be around the corner. A bunch of government speak for "it will be shoved down your throats soon because the lobby pays more" http://www.epa.gov/OMS/regs/fuels/ad...15/e15-faq.htm
RE: Your links: Hogspit (In your language) - Flouro - based fuel lines and seals, and a sensor (Flex fuel sensor) (E15 will need more fuel volume than E10) and call it good. I run 928s on E85. Other than a few rubber problems, its been great. Probably 8 years and over 50,000 miles in all different 928s.
07-13-2015, 06:50 PM
#97
Former Sponsor
I'm a proponent of the in tank fuel pump. I re-install them 100% of the time, on cars originally equipped with them. (And I've never seen one of those in-tank fuel pump hoses with less than 15 years of use fail....so I don't even change the hose on the new pump to one of my own hoses!)
It's not me trying to keep things as original as possible.
It's just that I believe Porsche re-fitted that in-tank pump in 1989 for a reason.....and that reason wasn't because Bosch could no longer supply the 1988 external pump, or that Porsche felt the need to spend another $200 per car because they were making too much money....
I figure those engineers knew a whole bunch more than I do about what they were building.
I've been a professional Porsche mechanic for over 40 years.....and while I've certainly seen a few "errors" from the Porsche factory, by and large, you'd better have a damn good reason to change things, before you just decide they didn't know what they were doing!
It's not me trying to keep things as original as possible.
It's just that I believe Porsche re-fitted that in-tank pump in 1989 for a reason.....and that reason wasn't because Bosch could no longer supply the 1988 external pump, or that Porsche felt the need to spend another $200 per car because they were making too much money....
I figure those engineers knew a whole bunch more than I do about what they were building.
I've been a professional Porsche mechanic for over 40 years.....and while I've certainly seen a few "errors" from the Porsche factory, by and large, you'd better have a damn good reason to change things, before you just decide they didn't know what they were doing!
07-13-2015, 07:17 PM
#98
Rennlist Member
Now that said, I cannot say the fuel cooler was doing an outstanding job... I didn't have my IR gun with me, but the hand-on-tank-o-meter said "pretty darn warm", could have been 120-130. The AC was running well, I'm just not sure there is enough heat-exchange capacity. Has anyone had one apart?
Cheers, Jim
07-13-2015, 07:58 PM
#99
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<<...>>
I cannot say the fuel cooler was doing an outstanding job... I didn't have my IR gun with me, but the hand-on-tank-o-meter said "pretty darn warm", could have been 120-130. The AC was running well, I'm just not sure there is enough heat-exchange capacity. Has anyone had one apart?
Cheers, Jim
I cannot say the fuel cooler was doing an outstanding job... I didn't have my IR gun with me, but the hand-on-tank-o-meter said "pretty darn warm", could have been 120-130. The AC was running well, I'm just not sure there is enough heat-exchange capacity. Has anyone had one apart?
Cheers, Jim
I had a very interesting discussion recently with an equipment supplier, routers and switches in this case, who opined that excess heat was the cause of his equipment failure. He said it was good to 140ºF, but that ours were way too hot. I asked him to put his hand on the equipment. "Way too hot!" he said, with is hand still flat on top of his hardware in the cabinet. When I suggested that 140º was too hot to touch, he laughed. So out came the IR gun, which read 105º Turns out that 115º is uncomfortable for any extended contact, 125º will give first-degree burns after a short while, and his 140º will cause a dirty word to escape your mouth as you snap your hand away.
Meanwhile... Vapor pressure of various gasoline components are all over the place. So much blending variation that it's hard to say what universal hard limits there might be. Cold weather. Cold in the mountains. Hot weather, and worst-case really hot in the mountains, all present different fuel requirements including net vapor pressure. Gas at individual stations is all over the map too. So trying to define a particular universal circumstance or limits beyond which we might suffer main pump first-stage fuel boiling is a bit of a crapshoot.
07-13-2015, 07:59 PM
#100
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I figure those engineers knew a whole bunch more than I do about what they were building.
I've been a professional Porsche mechanic for over 40 years.....and while I've certainly seen a few "errors" from the Porsche factory, by and large, you'd better have a damn good reason to change things, before you just decide they didn't know what they were doing!
I can start with the 356 and note mistakes all the way up to the Panamera. As a 928 expert, you should well know more errors than I. There are plenty. Was the in-tank pump one of them? It fixed the issue they found with fuel vaporization, and look at all modern cars you'll find submerged pumps. However, for 99% of us 99% of the time, not needed. One guy hits the Ethanol, heat, speed trifecta and everyones 'sky is falling!'. harumpf...
07-13-2015, 08:02 PM
#101
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I'm a proponent of the in tank fuel pump. I re-install them 100% of the time, on cars originally equipped with them. (And I've never seen one of those in-tank fuel pump hoses with less than 15 years of use fail....so I don't even change the hose on the new pump to one of my own hoses!)
<<...>>
<<...>>
07-13-2015, 08:09 PM
#102
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I was going to ring you about fitting your better hose to my new spare Bosch in-tank pump I have on the shelf. Guess you saved me a call, unless you think it's a good idea. No telling how long it will sit in the box, but it might be a candidate for installation as PM, especially after the growing list of 'stranded' cars lately. Thoughts?
07-13-2015, 08:09 PM
#103
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Footnote--
With my long history with fuel pump and vapor-lock issues in Bosch-equipped cars, I took an extra step when refitting the fuel rails as part of the little intake-refresh project. I meticulously added foam insulation layers to the fuel rails, to perhaps reduce the amount of heat transferred to the rails and ultimately the fuel inside. I did not try to insulate the exposed metal fuel piping, although it would make a lot of sense to do so. The pressure-side line that comes up the passenger fenderwall is a perfect candidate, thanks to its proximity to the right-side head and exhaust.
With my long history with fuel pump and vapor-lock issues in Bosch-equipped cars, I took an extra step when refitting the fuel rails as part of the little intake-refresh project. I meticulously added foam insulation layers to the fuel rails, to perhaps reduce the amount of heat transferred to the rails and ultimately the fuel inside. I did not try to insulate the exposed metal fuel piping, although it would make a lot of sense to do so. The pressure-side line that comes up the passenger fenderwall is a perfect candidate, thanks to its proximity to the right-side head and exhaust.
07-13-2015, 08:36 PM
#104
Former Sponsor
Oh my. While I generally respect Porsche for decent engineering, they were not, and haven't proven to be much better than any other car designer. In fact, worse than most.
I can start with the 356 and note mistakes all the way up to the Panamera. As a 928 expert, you should well know more errors than I. There are plenty. Was the in-tank pump one of them? It fixed the issue they found with fuel vaporization, and look at all modern cars you'll find submerged pumps. However, for 99% of us 99% of the time, not needed. One guy hits the Ethanol, heat, speed trifecta and everyones 'sky is falling!'. harumpf...
I can start with the 356 and note mistakes all the way up to the Panamera. As a 928 expert, you should well know more errors than I. There are plenty. Was the in-tank pump one of them? It fixed the issue they found with fuel vaporization, and look at all modern cars you'll find submerged pumps. However, for 99% of us 99% of the time, not needed. One guy hits the Ethanol, heat, speed trifecta and everyones 'sky is falling!'. harumpf...
Let me retry.
I didn't say the sky was falling.
I simply said:
* I believe the engineers added "back" the in-tank pump, in 1989, for a reason.
* That I wasn't as good at engineering as they were.
* That I had seen nothing that made me think that the in-tank pump was a terrible idea and that I should remove it on every car that I worked on.
BTW....Nothing that happened to Jim Corenman has changed my mind about any of those points.
So, in my world, the sky is absolutely fine.....no chance of it falling, here. Nothing has changed. I've got zero customers to call and tell that I made a mistake and they need to come and see me before they leave on an extended summer trip in their 928.
07-13-2015, 08:56 PM
#105
Former Sponsor
I was going to ring you about fitting your better hose to my new spare Bosch in-tank pump I have on the shelf. Guess you saved me a call, unless you think it's a good idea. No telling how long it will sit in the box, but it might be a candidate for installation as PM, especially after the growing list of 'stranded' cars lately. Thoughts?
I have no way of telling if or for how long "my" short section of hose is going to last. Goodridge sales tells me that the hose is compatible with all things in fuel.
Right! I totally believe salesmen.
Roger ordered up a bunch of hoses and clamps to supply to his customers. I think I charged him for the clamps...and told him that "the hose" was experimental and let me know if anyone had problems. (Besides that, it literally costs me more to cut the hose into those short sections than the hose could ever cost....it's like $.10 worth of hose!)
Get back to me, in 20 years.....I might know more.
In the meantime, if you've got a split hose, I've got an unproven solution that is better than the split hose they have right now.
Replace the original hose that is brand new? Charge someone to replace a hose that I believe will last for 15 years and that I believe is usually damaged when the pump is removed?
Not my style.