philwaters Posted June 22, 2005 Share Posted June 22, 2005 I have a problem with the fuel pressure on my car. I am 90% through converting my car to TB's, etc. On Sunday I went out for a run, logging from my ECU, and using Chris Good's mapping app on the datalog when I get back, and so on. However, half way through my 15-20 min run I noticed the car was starting to run leaner (I have on of Bill S's wideband readouts - also connected to the ECU). When I got home I shut the car down and pushed it back into the garage. I whipped the bonnet off and flicked on the ignition again and watched my in-line fuel pressure gauge spin up to ~30psi while the pump primed the system, then shut off. I had set this to 42psi when I installed everything. I then left the car for 2hrs to cool down while I went off and sulked indoors. I then tried the same test again and I saw ~38psi, and another hour later I saw 40psi. Now... I only used bog standard injection fuel hose (branded Codans or something, rated to 12 Bar) when I converted over, nothing fancy (expensive) and I have noticed that it has got softer and easier to squeeze as it has been run and get's warm. The question is - is this my problem? I have a long run of this hose from the tank to the TB's, past a hot LSD, gearbox and past the engine. Does expanding hose cause pressure drops, or do you just get a greater volume (larger ID of pipe x length) of fuel at the same pressure (set on my adjustable regulator)? I assume that the regulator is just like putting your thumb over a hose, restricting the flow, thus increasing the pressure. I think it is the problem, just after a sanity check really, or possible causes if changing to Aeroquip doesn't fix it. Phil Waters Link to comment Share on other sites More sharing options...
Colin Mill Posted June 22, 2005 Share Posted June 22, 2005 Hi Phil I would have thought the problem would be with the regulator. The volume change of the pipe must be quite small and the pump throughput must exceed the maximum fuel demand of the engine at fully loud (say 10cc/second). It seems very odd all the same! Link to comment Share on other sites More sharing options...
stevefoster Posted June 22, 2005 Share Posted June 22, 2005 Can't see it being the fuel hose. The pump will just pressure it up and reg will back the fuel up to the set pressure. 12bar is the same rating as the Goodridge stuff I am using. Can't say I've checked it to see if it's heat softened a bit as I've not had this problem. Sound's more like your Fuel pressure reg. I have a spare one if you want to try that... Are you sure your air temp map is right for these high amb temps (do you have an air temp map BTW?). That would not affect the pressure though... Hants (North) and Berkshire Area club site here Club meeting pics here Link to comment Share on other sites More sharing options...
Rob Walker Posted June 22, 2005 Share Posted June 22, 2005 Jenvey advised me against fitting an adjustable pressure reg said they were useless unless you buy a very expensive one. They supplied me with Weber fixed pressure reg which works well Link to comment Share on other sites More sharing options...
Alex Wong1697456877 Posted June 22, 2005 Share Posted June 22, 2005 I had problems when I first did my TB conversion - the reg was fine but the pump was struggling. I got an uprated pump from Caterham and that sorted it. The symptoms weren't quite thesame. I could set and maintain a pressure at idle then as soon as I opened the throttle, the pressure fell. Link to comment Share on other sites More sharing options...
philwaters Posted June 22, 2005 Author Share Posted June 22, 2005 Thanks guys, but I can't see how my FPR can change depending on temperature , it is only a diaphragm restriction isn't it? You set the pressure for a given system, if that system changes, does it not effect what the regulator sees and is acting on? The hose/circuit will cause a pressure on it's own - the pump can only deliver so much down it over time, if you then increase the flow, the starting point that the restriction of the FPR is acting against is now different, so it would need re-setting. It isn't clever enough to adjust to a new flow rate is it..... However, now that I know what pressure I want, maybe a fixed one is the way to go - I will look around. However, I wouldn't mind trying your spare Steve. I have the R500 pump I think, and it copes fine when reving the engine when freshly started, and indeed when I bedded the cams in at 2k for 20 mins it was fine. Phil Waters Link to comment Share on other sites More sharing options...
Colin Mill Posted June 22, 2005 Share Posted June 22, 2005 Hi Phil I think the restriction of the pipework would be way lower than the pressure drop across the regulator (after all carb systems have very low pressure pumps that work down similar lengths of pipe) However I can't see why the regulator should be so temperature affected - its hard to see there being enough differential expansion in the regulator components to cause it (unless it was actively designed to do so 😬) Link to comment Share on other sites More sharing options...
stevefoster Posted June 22, 2005 Share Posted June 22, 2005 Phil, Do you have push on hoses? I made sure at installation my pump could keep up by opening all the injectors and pressuring the rail up to 60psi with it emptying in to a bowl. What the pressure maintain and measured the flow rate. I think the JPE / R500 pump is a Rover 200 Turbo one (probably other cars too) and is up to our needs. Hants (North) and Berkshire Area club site here Club meeting pics here Link to comment Share on other sites More sharing options...
philwaters Posted June 22, 2005 Author Share Posted June 22, 2005 I know - that's why I was after a sanity check - my head is starting to hurt! Does anyone know what pressure the R500's run at? Another option might be that the pressure is too low and the pump is overheating - but then it is submerged in a fuel and at the back of the car away from heat sources.... I can't see this being an issue though. Phil Waters Link to comment Share on other sites More sharing options...
philwaters Posted June 22, 2005 Author Share Posted June 22, 2005 Steve, push on, but no where near as hard to push on as yours - mine gives a lot when needed, while I remember yours was really hard to fit - hence my brain blaming it. I can't easily test my flow like that as my injectors are low impedance, so would burn out with a continuous supply of 12v... Phil Waters Link to comment Share on other sites More sharing options...
F355GTS Posted June 22, 2005 Share Posted June 22, 2005 Phil Speak ot Steve Mell, he had this problem with the type of pressure reg you have, ie as it gets hotter the pressure drops, however the one you have didn't show these symptoms when mapped by Steve Greenald Mark Link to comment Share on other sites More sharing options...
Peter T Posted June 22, 2005 Share Posted June 22, 2005 Some cheap regulators cannot hold decent pressure, let alone stabilise themselves in hot/ cold weather. I had the same version as Steve's, cr*p i tested it with my Sykes pickavent testing equipment and it showed massive readings and was very unstable at holding pressure. Binned mine and spent proper money, which is why good regulators cost good money. What is the point of paying money to map your car with the correct amount of fuel and pressure if you know that everytime it is possible that it could be lower or higher. Carbon Components from K9 Composites Link to comment Share on other sites More sharing options...
philwaters Posted June 22, 2005 Author Share Posted June 22, 2005 Mark, thanks - I recall him telling me something about it a while ago - I'll re-ask. The fact that it was fine on your car is what is confusing me. Maybe it is due to the location. I have mounted it where the washer bottle used to be, so behind the engine, above the gearbox - not the best place for heat... but I know Mr Fosters is roughly there, so I assumed it would be ok. Peter - Thanks for the comment. What makes should I look out for for decent ones? Although I think a 3 Bar fixed is probably the simplest route, I can do away with the gauge then after testing it. Phil Waters Link to comment Share on other sites More sharing options...
Peter T Posted June 22, 2005 Share Posted June 22, 2005 Buying a fixed Bosch unit, they are the best, they hold pressure fine. Carbon Components from K9 Composites Link to comment Share on other sites More sharing options...
Colin Mill Posted June 22, 2005 Share Posted June 22, 2005 Hi Peter Do you know if its possible to still get the old style Bosch adjustable regulators (as per the early Jet-tronic systems on VW 412, VW-Porsche 914, late 60's Mercs etc)? Link to comment Share on other sites More sharing options...
Bob Corb Posted June 22, 2005 Share Posted June 22, 2005 Is the fuel tank becoming pressurised due to heat... I fitted an anti rollover valve once and it caused the tank to pressurisehad some strange effects... Also is the return hose kinked or compressed at all? Try flowing the return into a bucket temporarily and see what happens. Take extra special care when doing so and keep a fire extinguisher close at hand when playing with fuel circuits... Link to comment Share on other sites More sharing options...
I reply to every thread Posted June 28, 2005 Share Posted June 28, 2005 Yours isn't a Malpassi by any chance..........................? Link to comment Share on other sites More sharing options...
Anthony Posted June 29, 2005 Share Posted June 29, 2005 Pete Did you not use the one with the Swindon set up in the end ? Link to comment Share on other sites More sharing options...
Peter T Posted June 29, 2005 Share Posted June 29, 2005 Yes Anthony i did, and it was a small fortune to buy as i could not guarantee getting 4 BAR all the time with my JPE pump so i opted for a 3.5 BAR Now i have some mega injectors (1180 cc a minute) which i am going to try, as the 8 injector set up is causing a pain regarding a filter Carbon Components from K9 Composites Link to comment Share on other sites More sharing options...
Anthony Posted June 29, 2005 Share Posted June 29, 2005 OK, now I am worried, I have std R500 filter, and 5 bar pump - off comp EVO 7 From recollection tank is empty in a pretty short time ! a) Why do you need mega injectors ? b) Whats the issue with filter Link to comment Share on other sites More sharing options...
I reply to every thread Posted June 29, 2005 Share Posted June 29, 2005 Anthony - if you have bigger injectors then you can run a lower fuel pressure (in broad terms). You need to be able to hold A consistent fuel pressure to be able to map. So if you can hold a high pressure - say 4 bar - you can run a "smaller" injector although you may still run into cycle issues. If you can hold 2 bar consistantly then you may need a bigger injector. These are the issues I am facing at the mo. Link to comment Share on other sites More sharing options...
Peter T Posted June 29, 2005 Share Posted June 29, 2005 Being that the injectors are very near to the ram stack, putting a filter very close defeats the object, as it slows the incoming air speed which causes turbulance in the stack and results in a power drop. This is probably not going to be a major problem as most of the time the engine will not be at 9K+ all the time, but issues with lean mixture also presents a problem, unless you can run a closed loop facility and lambda ECU. Seeing that power can be achieved with one set of injectors and mixture issues are anon, i have decided to change as the transistion between the two was not perfect, as a better ECU would have a better mapping structurelike a Pectel or Motec, but i have no monies left for this, i will use large injectors with a very short duration and see if this is better. Carbon Components from K9 Composites Link to comment Share on other sites More sharing options...
Peter T Posted June 29, 2005 Share Posted June 29, 2005 PS, you need to have at least 14 volts powering the JPE pump to keep good pressure, so a good alternator is a must. Carbon Components from K9 Composites Link to comment Share on other sites More sharing options...
EFA Posted June 29, 2005 Share Posted June 29, 2005 Oh good, someone has mentioned how you power the fuel pump. Voltage drop along the supply cables is an issue - they draw quite a current! You should be using min 30A rated cable and ensure the ground conection is good. Power it straight off the battery through a relay. The JPE pump is really on the limit at 60psi. Also make sure you have the reg mounted the correct way up!!! Makes a huge difference to stability. I run a cheap double diaphragm one with no issues at all. Delivers a rock steady 60psi with a Bosch 907 external pump. Pete - I have money which says your 1100cc/min injectors will mean you engine will not idle. I am running 1.5% duty cycle on 480cc/min and am seeing switch latency issues as they cannot run reliably at this low cycle. Link to comment Share on other sites More sharing options...
I reply to every thread Posted June 29, 2005 Share Posted June 29, 2005 So I'm gonna be OK with a JPE in tank pump attached to the standard loom if I run a fairly low pressure (45psi) with bigger injectors than the straw ones I currently have 🤔 That is what Steve Greenauld is telling me. Don't for christs sake tell me that I have to rewire the friggin car & get a brise alternator that: A) Doesn't fit B) Costs a fortune C) breaks Link to comment Share on other sites More sharing options...
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