Samba Member
Joined: August 20, 2003
Posts: 260
Location: Western Mass
| Posted: Wed Oct 17, 2007 11:39 am Post subject: No power | |
| I have a 1972 Bus that I converted to FI with a Vanagon Digijet system. It runs and drives right now. I Have a Vanagon Distributor on it and Vanagon Coil. My problem is it is not making enough power. The Timing is set to 7.5 ATDC. Sometimes the lack of power gets so bad i have to downshift it to 3rd to get up the tiniest grade and 1st gear for a hill near my house i used to be able to climb in 3rd. (back when I had carbs) This low power syndrome thing fluctuates, sometimes its not too bad, other times its horrible. I have reason to believe it may be either my coil or distributor, because both of those I borrowed off of my vanagon, which had a very similar problem. Any ideas? Maybe my coil is crapping out at random times? | |
| ');//--> |
Samba Member
Joined: December 09, 2004
Posts: 2617
Location: Coppell, Texas
| Posted: Wed Oct 17, 2007 1:06 pm Post subject: Re: No power | |||
Huh, I'm confused. You are talking about a Vanagon yes? Lack of power? I did not know this was considered abnormal! Past VW drives: 1967 Beetle, 1973 Beetle, 1977 Bus, 1971 Military Type 181 | |||
| ');//--> |
Samba Member
Joined: August 20, 2003
Posts: 260
Location: Western Mass
| Posted: Wed Oct 17, 2007 2:22 pm Post subject: | |
| Its a vanagon FI system on a bus motor. And by lack of power I mean flooring the gas in 3rd gear gives me 40mph on flat ground, and 1st gear up hills i used to be able to go up in 3rd, lol like a DRASTIC loss of power | |
| ');//--> |
Samba Member
Joined: August 03, 2003
Posts: 34890
Location: The Beach
| Posted: Wed Oct 17, 2007 2:46 pm Post subject: | |
| Why are you timed at 7.5º ATDC? What distributor are you running? | |
| ');//--> |
Samba Member
Joined: March 24, 2004
Posts: 6188
Location: Portland, Oregon
| Posted: Wed Oct 17, 2007 3:04 pm Post subject: | |
| 72 bus, what size engine is in it? What year of vanagon did you pull the FI off of? Did you test all the FI stuff before you bolted it on, or did you just pull the system off a junk Vanagon and bolt it on? | |
| ');//--> |
Samba Member
Joined: August 20, 2003
Posts: 260
Location: Western Mass
| Posted: Wed Oct 17, 2007 4:01 pm Post subject: | |
| 1. 1700 Bus Engine 2. 83-85 Vanagon Digijet System 3. I timed it there because aren't VW bus engines run best with the timing advanced a little? Correct me if I'm wrong but wasn't that the timing for the FI Buses? 4.The Air Box, Wiring, Computer, Idle Control, Temp Sensor have all been tested and are good. 5. It is just the stock vanagon distributor one would find on any 1.9 engine. Things not tested | |
| ');//--> |
Samba Member
Joined: May 02, 2006
Posts: 10078
Location: Abiquiu, NM, USA
| Posted: Thu Oct 18, 2007 9:05 am Post subject: | |
| Not knowing what arrangement you have made with the throttle body and intake plenum, it's hard to say, but it sounds to me like you have insufficient advance. This will also make the engine run extremely hot while it's busy not making any power. It's doubtful you could just use the recommended timing settings for the wbx Digijet, although that's a good enough place to start. Take a look at the diz timing figures here, and see if your diz is the same part number: http://brickwerks.hostinguk.com/VehicleSpecific/T3/info/enginedata/wbx/DGdata.htm It's not exactly the same motor as the DH Digijet sold in the US, but it might be comparable. The specs might also be in Bentley. Anyway, test the amount of vac advance and retard your diz provides. Break it down by the numbers, otherwise you're flying blind. With a strobe hooked up, remove and replace the vac lines and see how much retard is made by plenum vac at idle, how much centrifugal advance is made without the TB vac signal, then with it. You should be able to deduce a new timing setting roughly from the data, so that you arrive at a 38deg. total advance, and then make trial and error adjustments for the best performance. Having a CHT gauge would be very useful here. Please don't PM here, I will not reply. Experience is kryptonite to doctrine. | |
 | ');//--> |
Samba Member
Joined: March 24, 2004
Posts: 6188
Location: Portland, Oregon
| Posted: Thu Oct 18, 2007 9:41 am Post subject: | |
| You're never going to get that to run right, just about all the digijet system is incompatable with air cooleds, except maybe the aux air regulator. Most of the FI from an aircooled vanagon is compatable with the newer baywindow 1.8 and 2.0 liter engines, but I don't even know how well it would work, or if it would work with the older upright 1700 engine. You would have to be able to reprogram the ecu for it to work, for one thing the temp settings are all wrong for an air cooled. Air cooleds run alot hotter then waterboxers. | |
| ');//--> |
Samba Member
Joined: March 13, 2005
Posts: 50338
| Posted: Thu Oct 18, 2007 9:58 am Post subject: | |
| You need to set your timing to 28° BTDC at 3000-3500 rpm, hoses off, pretty much no matter what fuel system you are running.. With a digijet you will also need to connect the plugs to the idle stablizer together when timing it. If you have an advance/retard dizzy and the retard can is shot as is likely your timing is going to be 15° retarded if you set it at 7.5 ATDC. I am not sure how the digijet will work with the Temp Sender II off of an air cooled. Probably alright, and if it doesn't you could just wire up a rheostat on the dash to supply the needed input. | |
| ');//--> |
Samba Member
Joined: October 14, 2004
Posts: 1181
Location: AZ
| Posted: Thu Oct 18, 2007 11:48 am Post subject: | |||
That was just the point I was going to make. Digijet relys on some input from the temp sensor II to compensate for engine operating temp. Since the op temps of an air cooled motor are typically higher and tend to fluctuate a lot more this input could be difficult to figure out (at least for my feable brain). If you've got a Bentley manual around for the Vanagon there's a graph in there that shows the range of resistance that sensor is supposed to have over the op temp range of the waterboxer motor. Might be useful information. I agree with others here that probably your biggest issue is the timing thing but getting that temp II input dialed in somehow will definitely help it to run better and more efficiently. I wish you success. | |||
| ');//--> |
Samba Member
Joined: May 02, 2006
Posts: 10078
Location: Abiquiu, NM, USA
| Posted: Thu Oct 18, 2007 3:48 pm Post subject: | |
| The Temp2 sender just regulates the warmup mixture; once it has crossed the warmup temp threshhold, the ECU determines injector opening duration from the lookup table in memory. The table has two axes, rpm and load. There is a correction factor provided by the IAT sensor in the AFM, and once the ECU has the basic duration from the table, it modifies duration in a feedback loop with the O2 sensor to maintain mixture at Lambda, or 14.7:1 AF ratio. The only time Digijet goes off Lambda when the WOT switch closes. Then it goes open-loop, ignoring the O2 signal. Lambda is Lambda, it wouldn't matter one whit whether the engine is water or aircooled as long as you have the Lambda system working. So, if you want to trick the ECU into running in normal mode, you can just bridge the Temp2 sender wires, or ground the sender wire with a single-wire type. Nearly every NTC thermistor you will find on automobiles conforms to the resistance/temp table in the manual, so I doubt there is much if any difference between the Digijet and an aircooled head temp sender. You can verify this by checking datapoints for both engines' temp sensors in their respective manuals. So, if you can position the Temp2 sender where it will be exposed to surface temps over about 170deg.F, you will be sure to have kicked the ECU into normal running mode by the time the motor is warmed up. That shouldn't be a big problem. Of course the ECU only controls injection, and has nothing to do with ignition, which is a standalone system, other than sharing the rpm signal from the Hall generator. I would think, then, that you would be best off using the diz, ignition control module, coil, and idle stabiliser from an aircooled 2 liter late bay or Vanagon instead of from the wbx. The advance curves in wbx's are a lot different than an aircooleds; the wbx can handle more aggressive advance without detonation. Then you need to go thru it piece by piece. I'm assuming that first you know the motor has good compression. Second, you need to be sure that the fuel delivery system is to spec. You need to know that the fuel pump open-line delivery volume is at least one liter per minute. Then establish that the fuel pressure is correct for a Digijet, with and without vacuum signal applied to the regulator. The signal hose should come from the intake plenum after the throttle plate. You can bridge the fuel pump relay to test, and apply vacuum with a handpump to verify that pressure is reduced by 7psi with full vacuum applied. 29psi with full vacuum, 36psi without. The entire intake air plumbing from the ECU output to the intake ports on the heads has to be free of vacuum leaks. Injectors have to seal completely to the intake manifold ends. There has to be 12V at one pin of each injector connector when the system is switched on. The diz retard line should come from the same source as the fuel pressure regulator vac signal. The diz vac advance line should come from the nipple on the TB that is obscured when the throttle is closed, and has vacuum on tip-in. What else? I would take the EEC system completely offline until you have the problem figured out. Check thru all those things, make sure all those subsystems are connected and working correctly. I really think you would be better off using an aircooled ignition system from an aircooled AFC FI bay or Vanagon. The only potential conflict I can imagine by mixing Digijet FI and an AFC diz might be the voltage amplitude of the rpm signal, but I don't think it would be incompatible. You could swap the Hall gen from the Digijet diz to the AFC diz if you're in doubt. Then, you could set the AFC timing according to the specs for AFC aircooled. If you use the Wbx Digijets diz, the basic timing setting might not work well with an aircooled, and the timing curves might not work well with it at all due to the vastly different temp variations under load. Please don't PM here, I will not reply. Experience is kryptonite to doctrine. | |
| | ');//--> |
Samba Member
Joined: August 20, 2003
Posts: 260
Location: Western Mass
| Posted: Mon Oct 22, 2007 6:38 pm Post subject: | |
| sometimes its the simplest of things hahahaha silly me forgot to hook up the vacuum retard hose to the distributor. I hooked that up and re timed the motor at 7.5 ATDC and it runs great now, it idles perfect and I have to let off the gas to keep from speeding on flat ground. With my old carbs I had to put my foot into it to cruise, now it cruises so smooth I forget I've got a motor. I'm fine tweaking everything but am very pleased with its performance. Now to mount an OXY sensor and get even better mileage | |
| ');//--> |
