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Engine Specific Info and Questions => TDI Engine -General Info => Topic started by: MikkiJayne on November 09, 2007, 12:21:40 pm
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Hi all,
I'm putting a 1Z TDI in my Corrado this weekend and I'd like some opinions on my fuel tank options please :)
1, The Corrado tank has a low pressure gas lift pump
2, I have a mk3 Golf GTI tank, which has a high pressure gas pump
3, I also have a mk3 Golf TDI tank sender unit with no pump which will fit the GTI tank
Now I have to remove the tank whatever happens since the breather is blocked and it won't fill properly, so any of the above options is equally valid as the others.
Also I'm not leaving this at 90bhp :wink: I'm building a 200bhp AHU to go in the car eventually, so I'm looking for my best long term option. I've heard that the top end is better with a lift pump, hence my query.
All opinions welcome 8)
Mikki x
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The low pressure pump could act as a feed pump for now, pulling directly from the tank. It'd work nicely for this purpose as long as it is in good condition.
If needed...another low pressure pump could be installed at a later date inline somewhere in between the tank and pump to further "assist" the pulling of fuel.
So...I'd just use the in tank 'rado one for now.
Joe
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low pressure gas pump? out of what car? the high pressure pumps are around 65 psi or more. using that will throw off your dynamic timing.
you would only want somewhere in the range of 5-9 psi.
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On the gas VW's and depending on what fuel system you are using there are variations of pumps...
The pumps that exist in the tank themselves are merely low pressure "transfer" pumps... should cause no problems with our setups.
Its the similar to the "lift pump" provided in later TDI's tanks.
LATE MK1 cabbys (Digifant) have a lift pump in-tank, Digifant MKII's, most 16v cars and then you move into the MK3's and IV's as well if memory serves me correctly. MKIV PD's have there own "lift pump" that comes with the car and is now a popular upgrade for those with the MKIV ALH's that can simply add it to assist the VE pump cars.
Here is a pic of a cabby one..
(http://i153.photobucket.com/albums/s211/swimmerjaxon/cabrio013.jpg)
The secondary pumps are usually the high pressure pumps that would provide TOOO much pressure for the injection pump. The highest pressure pumps are found on older CIS cars. The highest pressure one I can think of "stock" is the one found in the OLD MK1's with CIS, sits right under the passenger side just in front of the p side rear wheel (capable of 100psi just open flow)...
Here is what a b3 one looks like
(http://home.comcast.net/~richago/media/Picture_07.JPG)
Later CIS/ CIS-E Motronic systems and Digifant have a "secondary" pump located in a simlar location (p side, just in front of the rear p side wheel) but are much smaller, lower pressure and also have a accumlation box as well (Depending on what year, engine, fuel system VIN split, etc)
Here is a thread on TDIclub about it...
http://forums.tdiclub.com/showthread.php?t=143129
A fuel pressure regulator, etc. can be used to trim the pressure down as well.
Joe
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Ok thanks. So I could use the Corrado lift pump if needed, but not the Golf 3 pressure pump.
But is there any advantage to using the lift pump?
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The gasser transfer pump....the PD's lift pump (for MKIV PD people or ALH's wanting an upgrade) does have benefits in helping the injection pumps internal pump PULL fuel to the injection pump and keep enough fuel present to prevent starvation at the injection pump, air in the lines/bubbles forming, etc. It does have its benefits when the injection pump really needs to pull more fuel...especially in cars that are significantly fueled and even stock ones *several threads on here about it...even in the IDI forums*.
I can HEAR my fuel pump pick up, kick up...gear up...whatever you want to call it when the mTDI is demanding more fuel...
It does indeed have a benifit...mainly, to assist the injection pump in pulling fuel from the fuel supply.
Joe
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is the PD pump self regulated? i thought it delivers around 50 psi as the pump injectors cannot suck any fuel at all.
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The PD lift pump push only 10psi, there is another pump (tandem pump) on the side of the head which pushes 50-100psi at the injector unit.
Lift pump on a VE engine will not add power, but it will be useful to not lose some power and help the pump.
On other european car an truck with VE pump, lucas pump., zexel.....etc... the most of the time It have a lift pump, mechanic or electric.
7-10 psi is perfect.
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The PD lift pump push only 10psi, there is another pump (tandem pump) on the side of the head which pushes 50-100psi at the injector unit.
ah this helps immensely! i might not need the in tank lift pump for my PD then...
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couldn't have answered it better myself :)
Joe
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Those of you that are running lift pumps - how are you powering them?
I think it would be too much strain on the pump and pipework to just run it on the ignition, and my ECU doesn't have any facility for an electric pump.
I'm thinking maybe a mk1 GTI fuel pump relay that switches on when it gets an rpm signal?
Thanks, Mikki x
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Any switched circuit is going to require a connection at the ignition at somewhere/some point. This isn't a huge deal. If the pump draws quite a few amps, etc... it might be worthy to go ahead and "relay it" as there your only using the switch "ignition" circuit to acutate the relay and power for the pump is drawn directly from a power source connection (i.e. direct 12v power from the battery).
A pump though that draws the kind of power to need the relay really bad would be a primary pump on a gasser... thus the relay...
Pumps that are for our applications shouldn't draw that much power so I don't think a relay is required...but it never hurts.
Inline fuse....def.
Joe
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Thanks, but current draw isn't a problem. It already has everything in place to power the pump (relay, fuse, etc) from the original engine. What I'm looking for is something that will only switch on the pump while the engine is running - this was done by the original gas ecu which is obviously now gone.
If it's simply switched on the ignition then the pump can run when the engine isn't, thus either stalling or overloading the pump, or over-pressurising the lines (unlikely).
If the inj pump has something like a carb float valve it will be fine and just return the excess fuel to the tank, but I don't know if it works like that?
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I put a PD150 in my MK3 and I kept the existing pump. Pressure would have been far too high so I ended up using a bypass regulator down under the car to drop pressure to ~2.5 bar. From there I have a non-return style Holley regulator under the hood with a gauge on it so I can fine tune the fuel pressure at around 10 psi. This has been working perfectly thus far. I would recommend you use the existing lift pump though as that should give you more volume than actual pressure which is what the pump needs. If you must use a higher pressure pump then you will want to regulate it down as I did.
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The ECU has nothing to do with turning the pump on or off.
The fuel pump relay on the the corrado was switched "on" by the ignition circuit, off a switched current line. (Switched circuits have to somewhere operate on any car OFF the ignition circuit or a SEPERATE switch (therefore another "switched" circuit). Its the same on most every VW gasser I've worked on as well... as well as most any car with a factory electric fuel pump, etc.
The exception to this could be the "latest" cars that throw almost all control over to the ECU...but I'm skeptical that would be the case.
If you have it properly hooked up to the switched circuit, then it will "come on" when the relay is signaled at the "contact" position of the ignition switch...then turn off when the key is turned off.
If it runs with the ignition off...something is wrong with the wiring and/or the relay.
You can also run your own "switch" I suppose if you want independently...but with the lift pump operating with its simple job...I can't see why you'd want it off other than maybe just being able to kill it.
Most fuel/transfer/lift pumps... will not keep the lines "Pressurized" all the time...especially what you are talking about using...
The injection pump does not have anything like a carb float...but does have a return line circuit.
Hmm...make sense?
Joe
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Sorry but you are wrong on this one. The ECU has everything to do with controlling the pump!
The fuel pump relay + supply is on the switched ignition, but the - goes straight to the ECU. When the ignition is switched on the ECU gives a brief pulse to the relay to prime the pump, and then switches it off again. Only when it receives a signal that the engine is turning (from the hall sender in the dizzy) does it turn the pump back on. It will remain on while the engine is spinning. If the engine stalls for any reason it will turn the pump off, likewise if you shut it off with the key. Every car with electronic fuel injection does this.
A variation on this is found in A1 and A2 cars with CIS (K-Jet) which don't have an ECU. They have a special relay which gives the pump prime pulse when the ignition is switched on, then they wait for an rpm signal from the coil. When an rpm signal is received a timer circuit will switch on the pump, and will continue to do so while it receives ignition pulses while the engine is running. Again, if the engine stops no more rpm signal so it shuts down, and ditto if you turn it off.
For now I'm going to switch the pump on the ignition, since I don't tend to sit in the car with the ignition on anyway, but in the end I will use the CIS relay triggered from either the ECU rpm output, or the Alternator W wire. That way if there is an accident and the engine stops but the ignition is still on, the pump will turn off and not (potentially) spray fuel everywhere.
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interesting...never have seen/heard that before and I've done a few gas-diesel conversions on late mk2 as well (digifant) and a b3 AAZ conversion for friends and never had any issues with the fuel pump there either "running after". We removed the entire ECU harness... and leaving the entire fuel pump circuit intact and it was fine "independent" of the ECU as long as you make sure what you are removing remains a switch circuit and is grounded correctly.
In this case...the wire leading from the ignition to the ECU (in fuel pump circuit) was to initially "prime" the pump and accumulate pressure for starting...turn the engine over, and VROOM.
The pump that is primed is the primary pump for fuel injection w/ the accumulator to of course build pressure in the lines. This was of course removed from the car (as its far to high a pressure to use as a lift pump), however...the transfer pump had no issues.
I know what you mean as well, as I have a b3 variant right now with CIS-E motronic and know about the "primary" (secondary in row with the transfer pump if you want to get technical) does start initially when the key is "on contact" making a connection with the ECU, etc. but never runs after...
Early mk1 and mk2 still do have a control box for CIS...I have one sitting downstairs, its an ECM as plain as day.
Relays are not complex devices, and receive electrical voltage (in a variety of voltages) to essentially turn on/off switches...they don't receive complex square wave signals, etc. and feedback from the ECU. Again...unless we are dealing with the latest in technology that may hand alot of that over to the ECU.
Interesting none the less...maybe we're thinking along the same lines but our talk isn't aligning somewhere...
Are you talking about this whole relationship in regards to getting it setup with the TDI electronics? Maybe thats the issue.
Joe
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I'm beginning to wonder whether US electrics are slightly different to Europe?
On the Corrado the lift pump and pressure pump are wired in parallel, so they both come on together. They run on the same relay, and the same wire in the fusebox, and are triggered by the ECU.
On US CIS cars you did have an ECU of sorts, because I think you had knock sensors and cats way before we did. In that case I would expect that to run the fuel pumps. UK CIS cars didn't have an ECU at all (except the 16V), and they have this special relay I'm talking about which has a circuit board in it.
The circuit is a 555 timer chip. When it powers up (ignition on) it runs the pump for a second or so - the prime pulse - then it turns off. An ignition event will trigger it again, for another second. Since ignition events happen more often than every second, the timer never gets a change to turn off, therefore keeps the pumps running. As soon as the engine stops the timer expires and switches off too.
One very important point to note - on CE2 cars the diesel glow plug relay is in the same location as the gas fuel pump relay. If you leave the fuel pump(s) connected then they will run for a second or so when you turn on the ignition, as the ECU / etc will turn on the glow plugs! That's what your B3 variant is doing :wink:
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Interesting...
I don't think the electronics are all that different (with exception to emissions, etc). but I can see what you are saying.
In the end... the "loop" that you are talking about itself (the ECU in this situation) acts like a switch as well. The ECU is still triggered by the ignition and allows the turning on/off of this circuit.
I think we are on the same page now.
In relationship with my b3. I'm doing my second TDI here this winter...currently...rebuilding the motor (or rather prepping for that...) at the moment. It'll be another "mTDI" but I plan on installing a complete AAZ b3 wiring harness. I love the ease of CE2 and its "expandability" if you want to call it that. Makes swaps SOOO much easier. However, when I do the swap, like on the MK2's of previous swaps (non electronic...most were CE2 though) I want to be able to pull the entire ECU loom/engine harness from the motor and install the diesel wiring harness...just cleans things up and makes it much easier.
We I believe were on the same page...just looking from different angles...I was looking starting at the ignition (which does have to "turn on" the ECU to allow this "loop" to occur (i.e. turning on the pump briefly, priming, etc) whereas you were speaking in terms of the ECU itself. I see the potential problem that you are facing and the "way" you were looking at it from the standpoint of adding the TDI electronics into the mix; in which in most cases with exception to PD's had no "lift pumps" there fore...no real way for the signal to occur without creating your own relayed circuit or a switched circuit.
In the b3...I'll have to account for the loss of the ECU triggering the fuel pump circuit which should be some fairly simple wiring to the fuel pump relay to allow this to occur.
Makes sense :)
Joe