Craigorypeck
|
| posted on 23/11/11 at 08:11 PM |
|
|
fuel return line back pressure
fuel level in tank is pushing the pressure on my fuel regulator too high.. both the out/return lines are on the sender which is near the bottom..
set up is supercharged bike carbs, 3 bar EFI fuel pump, mallory boost reference regulator. I can get the pressure down to 3 psi which the bike carbs
need when off boost but the level of fuel in the tank is pushing up base pressure, more fuel in tank more pressure at carbs
Not too keen on drilling holes in the tank to raise the return height but would a swan neck inside the tank from the return help
something like this maybe?
|
|
|
|
|
MakeEverything
|
| posted on 23/11/11 at 08:21 PM |
|
|
Why not just have it point upwards rather than a loop?
Kindest Regards,
Richard.
...You can make it foolProof, but youll never make it Idiot Proof!...
|
|
|
daviep
|
| posted on 23/11/11 at 08:29 PM |
|
|
How did you come to this conclusion?
I don't mean to be cheeky but petrol has a pressure gradient of approx. 0.33 psi/foot so unless your tank is 10 feet deep then it would indicate
the pressure is being generated by something other than hydrostatic head.
Are the return lines all of large enough diameter - no restrictions in the sender?
Davie
“A truly great library contains something in it to offend everyone.”
|
|
|
Dusty
|
| posted on 23/11/11 at 08:36 PM |
|
|
Try it with the fuel filler cap off. You may be pressurising the tank somehow.
|
|
|
MakeEverything
|
| posted on 23/11/11 at 08:49 PM |
|
|
quote:
Originally posted by Dusty
Try it with the fuel filler cap off. You may be pressurising the tank somehow.
On this point, it should have a breather.
Kindest Regards,
Richard.
...You can make it foolProof, but youll never make it Idiot Proof!...
|
|
|
Craigorypeck
|
| posted on 23/11/11 at 09:04 PM |
|
|
quote:
Originally posted by MakeEverything
Why not just have it point upwards rather than a loop?
static charges maybe..
|
|
|
blakep82
|
| posted on 23/11/11 at 09:05 PM |
|
|
bike carbs with 3 bar pressure? and carbs with a fuel return line? am i reading that right?
whats higher, your carbs of the fuel in the tank (when full really) ?
the level of fuel would only create any sort of pressure if the level in the tank is higher than the carbs, but then, not much!
my bike carbs only on 1.5psi i think... or 1.5bar, i forget, either way not as high as 3 bar.
also carbs don't really have a fuel return line. fuel rails for injection should though
again, unless i've misunderstood something. i'm not that up on super charging
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
|
|
|
Craigorypeck
|
| posted on 23/11/11 at 09:07 PM |
|
|
quote:
Originally posted by daviep
How did you come to this conclusion?
I don't mean to be cheeky but petrol has a pressure gradient of approx. 0.33 psi/foot so unless your tank is 10 feet deep then it would indicate
the pressure is being generated by something other than hydrostatic head.
Are the return lines all of large enough diameter - no restrictions in the sender?
Davie
No worries... didn't know that!
The return lines are the same diameter, 8mm all round. maybe a 10 return will help.
|
|
|
daviep
|
| posted on 23/11/11 at 09:17 PM |
|
|
I you want to prove the theory then try blowing (with your mouth) in to the tank through the return line with a full tank of fuel, the human lung
cannot produce 3psi of pressure at sea level so if you can blow bubbles into the tank the pressure caused by the weight of full is less than 3psi 
“A truly great library contains something in it to offend everyone.”
|
|
|
Craigorypeck
|
| posted on 23/11/11 at 09:20 PM |
|
|
quote:
Originally posted by blakep82
bike carbs with 3 bar pressure? and carbs with a fuel return line? am i reading that right?
whats higher, your carbs of the fuel in the tank (when full really) ?
the level of fuel would only create any sort of pressure if the level in the tank is higher than the carbs, but then, not much!
my bike carbs only on 1.5psi i think... or 1.5bar, i forget, either way not as high as 3 bar.
also carbs don't really have a fuel return line. fuel rails for injection should though
again, unless i've misunderstood something. i'm not that up on super charging
Turbo spec carb regulator has a return to tank outlet and pressure in ref.. as the reg needs to keep above boost level and the base 1.5-3 psi so an
injection spec pump is needed. eg boost is 10 psi + 3 psi base pressure = 13psi fuel, not many carb pumps will give that.
The return straight to jerry can lets the pressure stay down, with sender connected it goes up a further 2 psi.. and increases when there is
significant fuel in the tank. up to around 6 psi in total
I'll check for a breather issue too..
[Edited on 23/11/11 by Craigorypeck]
[Edited on 23/11/11 by Craigorypeck]
|
|
|
r1_pete
|
| posted on 23/11/11 at 09:23 PM |
|
|
Why are you running a 45psi pump, and regulating down to 3 or so psi, you are circulating fuel unecessarily, a 5 psi pump should be all you need for
carbs, I'd hazzard a guess fuel is foaming in the tank, like it does when you're filling up and it triggers the cut out on the nozzle.
|
|
|
Craigorypeck
|
| posted on 23/11/11 at 09:32 PM |
|
|
quote:
Originally posted by r1_pete
Why are you running a 45psi pump, and regulating down to 3 or so psi, you are circulating fuel unecessarily, a 5 psi pump should be all you need for
carbs, I'd hazzard a guess fuel is foaming in the tank, like it does when you're filling up and it triggers the cut out on the nozzle.
As said above, need to keep above boost pressure... You can actually get a 25psi pump but its £130, my 3 bar was £30.
|
|
|
snapper
|
| posted on 24/11/11 at 07:11 AM |
|
|
Perhaps a swirl pot with breather for return flow only
Make sure you have a seoeratelly tank breather
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
|
|
|
Craigorypeck
|
| posted on 24/11/11 at 08:50 AM |
|
|
If I cant get it to behave a swirl pot would keep it all where it needs to be. Cheers.
|
|
|
BaileyPerformance
|
| posted on 24/11/11 at 09:41 PM |
|
|
Hi,
I did a turbo conversion on an old jap 4x4 ages ago, i used a metro turbo SU carb with a FSE regulator (carb type, as used in the metro turbo) I used
an XR3I pump.
I had the same problem, the regulator could not return enough fuel to keep the pressure at the carb below 5psi. The solution was to install a resistor
in line with the pump (about 2ohms) to reduce the pump flow, therefore less fuel to return. From memory i think the pump ran at 9volts with a 2 ohm
resistor, this depends on the pump used, you may have to experiment with different resistor values. A ballast resistor from an ignition coil would be
a good starting point.
Depending on fuel demand at full boost / RPM you may have to short the resistor under boost using a boost operated switch.
Another advantage to this system is less noise from pump, less fuel bubbling in the tank and less electrical load. (important if you are running a
bike engine as the alternators can be low output)
On a different point - Are you aware you must have some sort of boost related ignition retard system?
Cheers Dale.
|
NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
|
Craigorypeck
|
| posted on 24/11/11 at 10:08 PM |
|
|
Hi Dale
..... i hadn't even thought of that idear..
I know jack jones about electronics so how would I do this?
Where do I find a resistor..? whats it look like? lol..
How do you short it to run the pump at full tilt?
apologies for so many questions!
I have a TPS controlled megejolt, can it be mapped to suit a boosted engine or does it need a true MAP signal to work proper?
The megajolt has signal outs that may be utilized somehow to short the resistor... a few years since playing with the megajolt.
|
|
|
BaileyPerformance
|
| posted on 24/11/11 at 11:01 PM |
|
|
quote:
Originally posted by Craigorypeck
Hi Dale
..... i hadn't even thought of that idear..
I know jack jones about electronics so how would I do this?
Where do I find a resistor..? whats it look like? lol..
How do you short it to run the pump at full tilt?
apologies for so many questions!
I have a TPS controlled megejolt, can it be mapped to suit a boosted engine or does it need a true MAP signal to work proper?
The megajolt has signal outs that may be utilized somehow to short the resistor... a few years since playing with the megajolt. [/quot
Hi,
Search Google for ignition coil ballast resistor, its a 2 wire device that you need to wire in line with the pump + wire to drop the voltage too the
pump from 12v to around 9v.
Than a relay could be wired to short out the resistor, the relay contact wire ACROSS the resistor so it is shorted when the relay is energized. The
relay coil could be triggered by the megajolt under boost. You may not need to do this,it depends on what power output you are after? What engine are
you using?
My advise would be dont use bike carbs, that are NOT designed to be boosted, use a Metro SU. (good for over 200bhp).
The best solution is to use megasquirt, will work out cheaper in the end.
Cheers Dale
|
NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
|
BaileyPerformance
|
| posted on 24/11/11 at 11:04 PM |
|
|
Me again!
You must have a MAP signal to do it properly, so the timing can be retarded under boost. Megajolt has a map sensor built in i think so no problem, but
it must be mapped.
|
NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
|
Craigorypeck
|
| posted on 25/11/11 at 08:48 AM |
|
|
Thanks again Dale.. good info
Loads of Kawasaki bikes have been turbo'd and theres loads of info and good results online, Apparently keihin carbs have sealed shafts and will
handle a bar of boost with no probs.
I have an NA YB with mildish 288 deg cams in and theres an m45 on the side now.
Boost wont be massive so maybe the TPS megajolt will suffice, I'd have to buy the different MJ controlller thats got the MAP sensor and would be
as well heading for EFI & MS in that case.
Boost should be linear and with the correct spring in the BOV shouldn't have any spikes to worry about.. fingers crossed
Determined to get a decent result with whats there and without spending too much cash...!
Should get back on it at the weekend.
Cheers
|
|
|
BaileyPerformance
|
| posted on 25/11/11 at 09:47 PM |
|
|
quote:
Originally posted by Craigorypeck
Thanks again Dale.. good info
Loads of Kawasaki bikes have been turbo'd and theres loads of info and good results online, Apparently keihin carbs have sealed shafts and will
handle a bar of boost with no probs.
I have an NA YB with mildish 288 deg cams in and theres an m45 on the side now.
Boost wont be massive so maybe the TPS megajolt will suffice, I'd have to buy the different MJ controlller thats got the MAP sensor and would be
as well heading for EFI & MS in that case.
Boost should be linear and with the correct spring in the BOV shouldn't have any spikes to worry about.. fingers crossed
Determined to get a decent result with whats there and without spending too much cash...!
Should get back on it at the weekend.
Cheers
Hi,
You've got an expensive engine there! we did an NA cosworth on jenveys and megasquirt in an autograss car and it made 262BHP!!
I would say an M45 wouldn't feed it, if you gear the blower to make even low boost (8psi) the charge temp would be too high and you will be over
the RPM rating of the blower(16000RPM i think?). I would advise you swap the M45 for an M90 (cheap on ebay) and use a YB turbo inlet manifold,
throttle body and fuel rail (again available on ebay). feed the throttle body via an intercooler and a VERY big dump valve (as the blower needs to
vent when throttle closed, same as using carbs). I would use megasquirt MS2 with rover tomcat turbo injectors, all this should make 300+BHP at
1bar.
I recon you could do all that for less than £1000.
The only other comment i have is 288degree cams are soft for an NA but full race for a supercharged engine. You may find boost will be lost down the
exhaust at low RPM, loosing the advantage of the blower.(over a turbo)
I'm very interested how you get on, forced induction is always the way to go for real power!
Good luck with your project.
|
NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
|
MakeEverything
|
| posted on 26/11/11 at 01:09 AM |
|
|
Get hold of the supercharger map from the eaton website (or I can email it to you). This will tell you what efficiency the charger runs at different
RPM ranges, so is very useful in determining pulley sizes and ratio. You will need an intercooler as well to keep the charge temperature down as said
above. The M62 is another smaller alternative to the M45.
My blog will give you a load of information for your project, and I haven't needed to cock around with resistors or anything like that.
ETA the M62 is physically quite small (smaller than the m90) but has more capacity than the M45.
[Edited on 26-11-11 by MakeEverything]
Kindest Regards,
Richard.
...You can make it foolProof, but youll never make it Idiot Proof!...
|
|
|
Craigorypeck
|
| posted on 26/11/11 at 04:35 PM |
|
|
The bonnet barely shuts as is. interesting learning curve tho.. I built the YB to behave as its a weekend toy/everyday car in the summer hence the
mild cams and a CR of 10.5:1..
Its goes well as is (especially up rev range) but as always I got a bit bored as we all do, and thought that with the mild NA cams and moderate CR.
I'm going to dial a bit of overlap out and hopefully gain a bit of extra low torque and maybe a few BHP via the M45 geared at 2:1, the m45 will
spin to 14000 so a redline of 7000, I've read an m45 will produce enough air to make 240 bhp apperntly.
I'm guessing i have 180-185+ BHP in NA form... I'm not expecting much more than 5-6psi from the charger as its small.
I have a 50mm tial type BOV and a good sized intercooler up front and if I moved the servo could squeeze a bigger blower in but the funds are
scarce.
I have a look for your blog too
Cheers again
|
|
|
