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D-Jet PhD Sticky. Newbies Need Not Enter. Advanced FI Tuning
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rosevillain
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PostPosted: Sat Jun 04, 2011 11:10 am    Post subject: Reply with quote

Here it goes…

I wanted a smooth running, torquier than stock, easy to build, possible to tune, engine for my daily driven ‘68 square with factory d-jet. I drive 64 mostly freeway miles round trip 5 days a week. I also wanted to test the tunability of the factory d-jet, and perhaps find work arounds to its limitations.

1776(?), built on a dual relief case, oil filter take off from the side, DPR C/W 69mm crank, Mahle 90.5’s, stock 034 heads (step machined off, rebuilt locally, fluffed and buffed by me following Wilson book but maintaining the round port, single springs, stock rockers), 7.8 c/r, custom grind cam, reground stock lifters (the red ones).

Cam was built locally by DR Camshafts in Single Springs, CA. He listed 914 d-jet cams on his website, and was interested and engaging on the phone regarding my build. We discussed my expectations and my application. I took him a couple of cores, and he reground a cam similar to one of his 914 d-jet cams. 254’ advertised duration, .426” lift with 1.4 rockers (.334” with 1.1’s), 109’ lobe centers. By widening the lobe centers, it allowed more duration without changing the intake valve opening point at all. Wider lobe centers also allow a smoother idle (more vacuum), and lowers the peak torque RPM as compared to narrower lobe centers ( I read too much).

The biggest issue that I am having is the early (B-ECU) d-jet does not allow for adjustability of the full load enrichening (mentioned by Ray G. a while ago, but not taken to heart). I think that the full load enrichening is not activating, as when I accelerate at highway speeds, I get a ping. The switch does not engage in the driveway (I do understand that there is no load to speak of in this configuration).

I have run a 50 ohm resistor at temp sensor 1, and unplugged temp sensor 2, and jacked the fuel pressure up to 35. I have tried timing it at -5’, 0’, and +5’. It is rich at idle, there is much carbon in the exhaust, and nothing feels hot. I think that I have too much vacuum in the plenum, that is not allowing the switch to move.

I had the same ping under full load issue with the 1600 (fluffed and buffed heads), but only when really trying to kick its ass. I am in the middle of trying something really dumb to make this work.
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raygreenwood
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PostPosted: Sat Jun 04, 2011 11:52 am    Post subject: Reply with quote

Measure your vacuum at idle. If the vacuum is too high...you actually run lean...not rich. What is your fuel pressure? Is it stable? this is really common when going up in size but changing little else. Measure these tow things and get back to us. Ray
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voeltzwagen
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PostPosted: Sat Jun 04, 2011 5:20 pm    Post subject: Reply with quote

I'm also going to be bumping up to a 1776. Right now I plan on using a stock cam, but possibly running some larger valves, maybe something that is 40 x 35.5mm. If the larger valves are going to be a huge issue, I'm not opposed to running stock heads. I was going to keep the runners stock, and maybe polished, but I plan on increasing the plenum size. I'm hoping to get some weekend access to my buddy's CNC machine so I can make a new back plate that will increase the plenum volume. There isn't much room back there, but is it possible to go too big? How many cc's would you think would be sufficient?
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raygreenwood
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PostPosted: Sun Jun 05, 2011 9:12 am    Post subject: Reply with quote

voeltzwagen wrote:
I'm also going to be bumping up to a 1776. Right now I plan on using a stock cam, but possibly running some larger valves, maybe something that is 40 x 35.5mm. If the larger valves are going to be a huge issue, I'm not opposed to running stock heads. I was going to keep the runners stock, and maybe polished, but I plan on increasing the plenum size. I'm hoping to get some weekend access to my buddy's CNC machine so I can make a new back plate that will increase the plenum volume. There isn't much room back there, but is it possible to go too big? How many cc's would you think would be sufficient?


Before you go too far.....measure what you have. The two greatest points of rectriction are going to be the runners and TB. You are effectivelt building a 1.8L. The 1.8L type 4 engine (which came with L jet)...I have run with D-jet as well. Its plenum was taken from the 1.7L (1679 cc). It is right at 1 liter. It ran well but was slightly restricted...partly due to the runners being slightly smaller than the 1.7L....with basically 42 x 36 valves.

The valve size you are planning is fine.....especially since you cannpt do anything about the skinny type 3 runners. To offset that with a larger plenum....a good starting point is roughly 2.5 cylinder volumes (444 x 3= 1.1L) You could do fine with a 1 liter plenum.
Actually...more precisely...in most systems the runner volume is typically about 1 cylinder and chamber volume....so really the plenum should be 2.5 runner volumes. I do not know what type 3 runner volume is.
If you can do that with the plenum (2.5 runner volumes)....and have it be slightly undersized with reference to cylinder volume....you will get high velocity ...maybe to high.....but you wil definately need a larger TB to control that.
The trick is going to be making a slight;y larger TB to replenish that larger plenum. It should all still run OK...but I;m not sure if it will run or tune better. Ray
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voeltzwagen
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PostPosted: Sun Jun 05, 2011 2:58 pm    Post subject: Reply with quote

A couple pages back, there was some pretty good discussion on plenum and runner volume. I think the runners clocked in at 250cc each, and the plenum was 550-580cc (someone had been drinking Wink ).

Pending these numbers were accurate, it was determined that the 1776 is going to be the absolute max the stock intake could run.

I was thinking I could get away with a 15-20% increase in plenum size by building a new end cap that could accomplish this, but trying to get 1L out of a 550cc plenum may get a little fugly, and sourcing a 1.7 T4 plenum may be the way to go.
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raygreenwood
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PostPosted: Sun Jun 05, 2011 3:14 pm    Post subject: Reply with quote

Nope! no one had been drinking! The original plenum is sized about right for the stock runners.....but the runners themselves were always a little skinny on the type 3. It kept the velocity up high. Bear in mind that the port areas in the heads count as well.

The problem with sourcing type 4 plenem is that it does not fit the runner spacing and diameter. I think your idea for expanding the stock plenum would really help. You couls...also get some more plenum...if you have room....by removing the throttle shaft and plate...install a tube of a few inches...and putting a new TB on the end of the tube.

I think it will work with a 1776.....but I'm betting you will need to retune the MPS. If you are doing all of this...do yourself a favor and build a new harness now so that any gremlins you end up chasing are from new changes...not old issues. Ray
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voeltzwagen
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PostPosted: Mon Jun 06, 2011 7:45 pm    Post subject: Reply with quote

Ok did some preliminary measuring and depending on the machining I should be able to fudge 125cc out of a new end cap on the plenum, which could expand the stock plenum to 2.5x runner volume(stock runners 250cc x 2.5=625cc) , or somewhere between 625cc and 655cc depending on whether the stock plenum is 550 or 580cc or somewhere in between.

Now for the throttle body. I couldn't quite tell for sure what size it is, 38 or 39mm (lost my calipers). There seems to be enough room in the neck of the plenum to bore out a couple millimeters and then have a custom butterfly built to attach to all of hardware (modified hardware) already there. The hardest part seems to be the idle adjustment port, which needs to be in front of the TB, there isn't much room. I suppose one could tap or press in a tube that could seal against the TB, but I'm not sure if that port diameter has significant effects on idle adjustment (it only needs air, right?).

Anywho, I'm learning a helluva lot and I apologize in advance if I ask a stupid question or miss something. I love this thread and I'm getting more and more addicted to learning how to take d-jet to the limits. This is way more fun than messing with my SC300 back in the day. After this...I guess its MS. Twisted Evil
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rosevillain
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PostPosted: Sun Jul 24, 2011 5:42 pm    Post subject: Reply with quote

rosevillain wrote:
Here it goes…

I wanted a smooth running, torquier than stock, easy to build, possible to tune, engine for my daily driven ‘68 square with factory d-jet. I drive 64 mostly freeway miles round trip 5 days a week. I also wanted to test the tunability of the factory d-jet, and perhaps find work arounds to its limitations.

1776(?), built on a dual relief case, oil filter take off from the side, DPR C/W 69mm crank, Mahle 90.5’s, stock 034 heads (step machined off, rebuilt locally, fluffed and buffed by me following Wilson book but maintaining the round port, single springs, stock rockers), 7.8 c/r, custom grind cam, reground stock lifters (the red ones).

Cam was built locally by DR Camshafts in Single Springs, CA. He listed 914 d-jet cams on his website, and was interested and engaging on the phone regarding my build. We discussed my expectations and my application. I took him a couple of cores, and he reground a cam similar to one of his 914 d-jet cams. 254’ advertised duration, .426” lift with 1.4 rockers (.334” with 1.1’s), 109’ lobe centers. By widening the lobe centers, it allowed more duration without changing the intake valve opening point at all. Wider lobe centers also allow a smoother idle (more vacuum), and lowers the peak torque RPM as compared to narrower lobe centers ( I read too much).

The biggest issue that I am having is the early (B-ECU) d-jet does not allow for adjustability of the full load enrichening (mentioned by Ray G. a while ago, but not taken to heart). I think that the full load enrichening is not activating, as when I accelerate at highway speeds, I get a ping. The switch does not engage in the driveway (I do understand that there is no load to speak of in this configuration).

I have run a 50 ohm resistor at temp sensor 1, and unplugged temp sensor 2, and jacked the fuel pressure up to 35. I have tried timing it at -5’, 0’, and +5’. It is rich at idle, there is much carbon in the exhaust, and nothing feels hot. I think that I have too much vacuum in the plenum, that is not allowing the switch to move.

I had the same ping under full load issue with the 1600 (fluffed and buffed heads), but only when really trying to kick its ass. I am in the middle of trying something really dumb to make this work.


Just for the sake of continuity, the above mentioned engine now resides comfortably in my '70 westy. The limitation of the early full load system is my excuse for not running it in the squareback.
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ddare
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PostPosted: Sun Sep 30, 2012 7:06 am    Post subject: Reply with quote

I have a 1776 currently using stock Type 3 fuel injectors that I am changing out to 30lb/min injectors. I purchased and rebuilt some injectors, Bosch P/N 0 280 150 357 after reading the Woreign's earlier thread on the subject, but I'm now noticing the end on the new injector looks different than the end on the old fuel injector. It looks as if it's designed for a fuel rail of sorts to snap on rather than 5/16" fuel line. The stock yellow top injector is on the right and the green replacement injector is on the left. Can these be connected to our fuel lines or do I need to get different injectors?

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Bobnotch
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PostPosted: Sun Sep 30, 2012 9:08 am    Post subject: Reply with quote

ddare wrote:
I have a 1776 currently using stock Type 3 fuel injectors that I am changing out to 30lb/min injectors. I purchased and rebuilt some injectors, Bosch P/N 0 280 150 357 after reading the Woreign's earlier thread on the subject, but I'm now noticing the end on the new injector looks different than the end on the old fuel injector. It looks as if it's designed for a fuel rail of sorts to snap on rather than 5/16" fuel line. The stock yellow top injector is on the right and the green replacement injector is on the left. Can these be connected to our fuel lines or do I need to get different injectors?

Image may have been reduced in size. Click image to view fullscreen.


You'll need different injectors, as those are for a manifold rail set up. I think Tram said Mercedees and Volvo use simlar (but larger capacity) injectors than the VW did. You could also try and hunt up some green 2.0L D-jet t-4 injectors. I had a set of these, but sold them to Keith Park.
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Woreign
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PostPosted: Sun Sep 30, 2012 11:49 am    Post subject: Reply with quote

The part number of the injectors I bought from Tram is 0280 150 036.
Image may have been reduced in size. Click image to view fullscreen.

They worked well with my 1776 and fit the D-Jet system. But due to some other tuning issues, I went with MegaSquirt instead. However, those injectors ended up being too big for MS to handle (very low VE table numbers) so I swapped back to the stock injectors which work just fine with my MS setup.

Looking back, I suspect that my tuning issues with D-Jet were due to voltage fluctuations. After installing an alternator, I had to make major changes to the MS settings. At times, I'm tempted to go back to D-Jet just to see if it would perform better with the alternator. Also so I could get the quick starting that I enjoyed with D-Jet but have not yet been able to get with MS...
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raygreenwood
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PostPosted: Sun Sep 30, 2012 2:13 pm    Post subject: Reply with quote

Bobnotch wrote:
ddare wrote:
I have a 1776 currently using stock Type 3 fuel injectors that I am changing out to 30lb/min injectors. I purchased and rebuilt some injectors, Bosch P/N 0 280 150 357 after reading the Woreign's earlier thread on the subject, but I'm now noticing the end on the new injector looks different than the end on the old fuel injector. It looks as if it's designed for a fuel rail of sorts to snap on rather than 5/16" fuel line. The stock yellow top injector is on the right and the green replacement injector is on the left. Can these be connected to our fuel lines or do I need to get different injectors?

Image may have been reduced in size. Click image to view fullscreen.


You'll need different injectors, as those are for a manifold rail set up. I think Tram said Mercedees and Volvo use simlar (but larger capacity) injectors than the VW did. You could also try and hunt up some green 2.0L D-jet t-4 injectors. I had a set of these, but sold them to Keith Park.



Yes..they are made for a fuel rail but can be modified to fit D-jet perfectly in minutes. The protector cap (thats all it is...no injector function)...and o-ring guide can be snapped off with pliers. be careful and do not bump the pintle.

The rear section of the injector where it bayonets to the rail....you can plug the opening with tape and grind or cut the green plastic back to the housing face. remove both ribs. It leaves a very nice tube with a rolled end for attaching fuel line.

the bigger issue is whether those injectors have the proper impedance to work with D-jet. D-jet is a low impedance system. Otherwise...that type of injector can be made to fit D-jet about as good as factory. Ray
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ddare
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PostPosted: Mon Oct 01, 2012 4:52 am    Post subject: Reply with quote

Since I've already got these injectors and gone to the trouble of rebuilding (and the price for four of 'em was less than the price for one 0 280 150 036 injector) I'll try modifying them and see how it goes.
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PostPosted: Mon Oct 01, 2012 12:30 pm    Post subject: Reply with quote

ddare wrote:
Since I've already got these injectors and gone to the trouble of rebuilding (and the price for four of 'em was less than the price for one 0 280 150 036 injector) I'll try modifying them and see how it goes.


check first if they are high or low impedance.
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ddare
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PostPosted: Mon Feb 18, 2013 8:59 pm    Post subject: Reply with quote

I was able to modify those injectors to fit and checked the impedance and yes they are low impedance. I've now got them installed but the car is backfiring and dies out pretty much whenever I give it gas, in addition to being a pain in the ass to start (like 10 tries, up from 3).

I am going to dial the fuel pressure back just a bit, double check wires and hoses, and also fiddle with the timing, any other suggestions? I may have switched the wiring for the #1 & #2 injectors as well as the #3 & #4 injectors, I don't expect that helps but will double check next chance I get.
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PostPosted: Tue Feb 19, 2013 11:59 am    Post subject: Reply with quote

ddare wrote:
I was able to modify those injectors to fit and checked the impedance and yes they are low impedance. I've now got them installed but the car is backfiring and dies out pretty much whenever I give it gas, in addition to being a pain in the ass to start (like 10 tries, up from 3).

I am going to dial the fuel pressure back just a bit, double check wires and hoses, and also fiddle with the timing, any other suggestions? I may have switched the wiring for the #1 & #2 injectors as well as the #3 & #4 injectors, I don't expect that helps but will double check next chance I get.


By low impedance...what ohm reading are you getting? Also what is their advertised flow rate in lbs per hour? Ray
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ddare
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PostPosted: Tue Feb 19, 2013 9:23 pm    Post subject: Reply with quote

It's been a few months since I measured but it was either 2 or 4 ohms or something like that. They are 30 lb injectors. I am going to test the MAP, TPS, and check a bunch of leads on the ecu to make sure they're within spec soon, hopefully this weekend.
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PostPosted: Wed Aug 21, 2013 9:56 pm    Post subject: Excellent D-Jet Resource Reply with quote

I'm not sure how many people are still stirring around on this thread but I thought I'd share a link to an excellent wealth of info about D-Jet. Maybe some of you have already stumbled across this...

This guy Paul 'Brad' Anders dissected his 914 D-Jet system and has developed some great tests and analyses of the system and what it's doing under various conditions. It's all centered around Type-4 based ECUs and whatnot, so the exact measurements may differ for the Type-3 set up but the essentials are the same. It gets a bit heavy at times but it's really good reading and has helped me better understand the system and think about ways to modify it.

http://members.rennlist.com/pbanders/index.html

I'm currently debating a 1776 for my squareback but want to use my stock D-Jet components, so I'm digging around for ways to do it. This thread has given good info so far!
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PostPosted: Wed Aug 21, 2013 10:24 pm    Post subject: Re: Excellent D-Jet Resource Reply with quote

JJM86 wrote:
I'm not sure how many people are still stirring around on this thread but I thought I'd share a link to an excellent wealth of info about D-Jet. Maybe some of you have already stumbled across this...

This guy Paul 'Brad' Anders dissected his 914 D-Jet system and has developed some great tests and analyses of the system and what it's doing under various conditions. It's all centered around Type-4 based ECUs and whatnot, so the exact measurements may differ for the Type-3 set up but the essentials are the same. It gets a bit heavy at times but it's really good reading and has helped me better understand the system and think about ways to modify it.

http://members.rennlist.com/pbanders/index.html

I'm currently debating a 1776 for my squareback but want to use my stock D-Jet components, so I'm digging around for ways to do it. This thread has given good info so far!


For a 1776 with a stock cam you can run your stock D-Jet system but you'll need the Mercedes blue tip D- Jet injectors to give you the correct fuel volume. They're a bolt in swap.

http://www.ebay.com/itm/MERCEDES-BENZ-BOSCH-FUEL-I...mp;vxp=mtr

That's for reference only- they're out there cheaper.
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PostPosted: Thu Aug 29, 2013 1:57 pm    Post subject: L-jet connectors Reply with quote

raygreenwood wrote:
I work by a differnt book. Connectivity is everything. To me....preserving correct plugs has no usefulness. In that respect...until I find a fix to use D-jet plugs....I am using the drill and ring terminal method for multiple prong connectors...with L-jet style sub-pig tails....at least thats the plan. I have to get the engine finished before I move much further.


What is the "drill and ring terminal method"? I have re-done all of my connectors on my harness, but would like to improve them. Ray, you've convinced me that a different type of connector is needed. My car is a '71, but I have a butchered '69 harness that I can use the pieces from to build a new '71 harness. Where can I get some of those dual-cantilever connectors, and how do I use them with my existing d-jet parts?

Thanks,
Jacob
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