Nice work getting rid of that 3700rpm dip! A lot of us with ITBs have experienced this dip. In my case, i was able to see the root cause was the timing dropping below my target. Played with some noise cancelling settings for the signal from the cam/crank pickup and then added a few more degrees timing and got it to flatten out.
I think there is some inherent resonance with the crankshaft or something at that RPM.

Table of Contents
 

This forum thread is long. Below is a table of contents to help you navigate thru it.



CIS to ITB EFI conversion: pg1 post 1-20, pg2 post 21-27

Brake conversion / weight reduction: pg2 post 28-30

Wiring improvements: pg3 post 41-42

Crankcase tear down: pg4 post 62-66

Heads tear down: pg4 post 68

Head stud removal: pg4 post 69

Engine wiring harness: pg4 post 72, 76

Parts cleaning / refinishing: pg5 post 81, 90, 96-99, pg6 post 100-105

Distributor modifications: pg6 post 106-107

Engine compartment seals: pg6 post 109-110

Engine lid seal: pg6 post 115

Rod and chain holder tools: pg7 post 126

Convert to moisture resistant connectors: pg7 post 129-132

Ground connections: pg7 post 136

Updated wiring diagrams: pg7 post 139-140

Piston weight: pg8 post 141

Engine air baffle modification: pg8 post 142

Updated sprocket supports: pg8 post 146-147

Piston / cylinder assembly: pg8 post 148-150

Fan, fan housing, alternator assembly: pg8 post 151-152

Deck height and compression ratio: pg8 post 153

Ignition timing set up - more info: pg8 post 154-155

Rod weight and piston/cylinder assignment: pg8 post 160

Crankcase clean and assembly: pg9 post 161-178

Valve train mock up: pg9 post 179

Piston to valve clearance: pg10 post 181

Engine assembly: pg10 post 182-194

Engine / transaxle installation: pg11 post 202-207

Camshaft break-in: pg11 post 209

O2 sensor controller calibration: pg14 post 263-266

Camshaft replacement: pg14 post 267-275

Final headers / exhaust fabrication: pg14 post 276, pg15 post 287, 292

Dyno tune / test results: pg15 post 295-296



Hope you find this thread to be helpful.

Good luck with your DIY project!

Hi Dan,

I have found your thread very useful and interesting.

Could you by chance post a picture of your acceleration enrichment tables?

Thanks,
Rutager

http://forums.pelicanparts.com/uploa...1727709552.jpg

Awesome stuff, Dan!
Ive also been watching with great interest ( I'm in the researching phase for my own EFI).
Question - If you are using Alpha N ie throttle position as your main load axis, and could you also post your latetst VE table Please? Also, what fuel injectors did you end up with?
Thanks so much!
Doug

Hi Doug,

With the stock 2.7 CIS motor on the original CIS to ITB EFI conversion, the vacuum signal was good (55 kPa at idle) and I used speed density (MAP sensor) for the load monitoring signal (see pg1 & pg2 of this thread for the details including the tune maps).

The rebuilt 2.8 motor with high lift / high duration cams had poor vacuum signal (72 kPa at idle) so I had to convert to alpha-n (TPS) for the load monitoring signal.

As you can see on the tune tables below the vertical (Y) axis is labeled "xxx load % TPS".

I am using Bosch 62672 (0280155831) fuel injectors (31.4 lbs/hr @ 3 bar, 329.8 cc/min, 12 ohm). The injectors are originally for Volvo 4/5/6 cyl turbo applications.

http://forums.pelicanparts.com/uploa...1727726042.jpg

http://forums.pelicanparts.com/uploa...1727726042.jpg

Thank you so much Dan! it’s a great reference. Its interesting that your max VE is 200. Is that a typical AlphaN / ITB thing to use more of the table resolution? Still learning :)
Doug

Hi Doug,

I know the VE in VE Table stands for volumetric efficiency and a naturally aspirated engine should operate up to 100% volumetric efficiency, but in TunerStudio, the numbers in the VE table cells are really a percentage of the "Required Fuel" value you set in the "Engine and Sequential Settings" page.

http://forums.pelicanparts.com/uploa...1727733994.jpg

For my set up, I have the "Required Fuel" value set to 6.00 ms. If I use TunerStudio's Required Fuel calculator that takes into account the engine displacement and the fuel injector flow rate, the Required Fuel calculator will set the "Required Fuel" value to 9.60 ms. Which is a problem with my engine because at idle with % TPS at or near 0.0 the values in the VE table cells along the bottom two rows would be in the range of 10-20 for the AFR target (from the AFR Table) of 14.0 to 14.2. VE table cell values less than about 30 make too big a shift in the injector pulse width going from say 12 to 13 for example to hit an AFR target of 14.0. A change in the VE table cell value from 12 to 13 will shift the AFR by 0.5 or more (and you can only make whole value changes, 12 to 13, not 12 to 12.5 for example).

So, I lower the "Required Fuel" value from the calculated value of 9.6 ms to 6.0 ms which means in ALL of the cell values in the VE table need to be increased by 70% to hit the AFR target values in the AFR table. My idle / no load values are 36 so my max rpm / full load values go to 202.

Long story short: in TunerStudio, the VE table cell values are very dependent upon the "Required Fuel" setting. The cell values are only indicative of the volumetric efficiency, not a measure of the engine's actual volumetric efficiency for a given engine speed and load condition.

Thanks for the explanation Dan. I knew the VE numbers are relative rather than absolute for your Volumetric efficency, but now i see why you did what you did..I’m leaning towards using a Haltech 750 Elite and they do all that differently from what i can see in the software... Been playing with the software on every system i can to make my final decision. I’m using PMO TB’s btw. Thanks :)
Doug

Interesting information Dan,

I did notice that your fueling tables were much higher than mine and I’m less than 20 in my bottom two rows of my tables. I am using MAP as my cams are mild and I get a good signal.

So if I set my required fuel 70% less and then do a whole VE table increase of 70%, that would be basically what you did to get better resolution?

Thanks so much for your sharing of info, you clearly have a very good grasp of the software.

Rutager

Hi Rutager,

I was just trying to explain how the VE table works in concert with the Required Fuel setting. If your tune is working well for you, LEAVE IT BE.

If you change the Required Fuel setting, you basically have to re-tune the VE table as a simple % change applied to the entire VE table won’t be correct. You’ll end up either making repeated tuning runs on the street while running auto tune and recording datalogs on your laptop to ensure you're running at your target AFR's or spending $$ at the dyno shop to do the same on the dyno.

CIS to ITB EFI conversion
 

Just to chime in and add more signal… or noise…

The required fuel setting is also relative to the injectors you have and how they perform/work…

FWIW, when looking at someone’s VE table in TunerStudio, basically just ignore the cell values and look at the 3D map to see how and where they’re adding or removing fuel.

Rutager- if you’re looking for more resolution there are a few TunerStudio hacks that I was playing with to effectively turn a 16x16 table into a 16x32 table with either the x axis (rpm) or y axis (load) doubling. This is very helpful if you are running speed density or %baro and spend most of your driving time above 80kpa or 80% baro which is pretty much a given with ITBs and want more resolution to really refine your tune.

If I can get to it this week I’ll post a thread about it. I think I posted in another thread somewhere a few months ago (July?) how to do it.

Rutager,

You are running speed density (MAP sensor) so your VE table is going to be different from my current VE table as your idle / no load conditions are probably not in the bottom two rows of the VE table.

Shown above is the VE table from my car before I rebuilt the engine. I was running speed density (MAP sensor) and my idle / no load condition was 50 - 55 kPa which is in the middle of the VE table.

And as Showdown points out the values in the VE table depend on not only the Required Fuel setting, but also the injector size and performance. And when looking at someone else's VE table look for trends like fueling increases with rpm and load, etc.

The VE table above was used with the MAP sensor for load with a Required Fuel value of 8.0 and 25 lb/hr injectors.

My current VE table in post 306 is using %TPS for load with a Required Fuel value of 6.0 and 31 lb/hr injectors on an engine that is making 20% more power.

Julian,

Yes, you did post how to enlarge the table on another thread- very clever!

Dan,

Thanks for the great explanations, as always, that makes sense, I only dip down to the lowest few cells on deceleration. My car is running pretty good right now, just a few minor drivability issues when doing slight throttle corrections like in traffic.

Best,
Rutager

Thank you Dan. So much great information that is sure to help other navigate these upgrades.

The car is running good. I have driven about 2000 miles on the rebuilt engine and after retightening valve cover nuts, oil feed fittings, etc the engine is oil leak free.

I drove the car over to Don's Autowerks in Campbell, CA last week to show my work to Don Wise. Don is my Porsche go-to guy, I have known him for 20 years now and he is a friend and mentor that has always encouraged me to get in and work on my old Porsche.

Anyway, I asked Don to take the car for a test drive - I have been the only person to drive the car since the engine rebuild. After he got back, he said the engine ran smoothly, sounded good and had plenty of power which was nice to hear from a Porsche person I trust.

After all the engine work, the rear decklid gas-filled strut was getting weak - it would still hold the lid open, but when I pulled the release handle the decklid would not longer open slightly so I fashioned a tool to keep the release handle pulled while I walked around back and opened the decklid.

http://forums.pelicanparts.com/uploa...1730309067.jpg

http://forums.pelicanparts.com/uploa...1730309067.jpg

I also bought a new strut, but instead of buying the gas-filled strut, I bought the Rennline mechanical strut which will lock the decklid open but offers no spring assist to help lift the decklid. It works as advertised just fine, but again as with the weak gas-filled strut, I have to use my release handle tool to hold the release open while I walk around to the back of the car and open the decklid.

http://forums.pelicanparts.com/uploa...1730309473.jpg

After more thought, I decided to just go back to the gas-filled strut. In fact, I ordered new struts for the front trunk as well.

Copying the Table of Contacts to end of the thread.

It's not the strut that opens the lid. It's the rubber bumpers.

I talk about it in my thread: https://forums.pelicanparts.com/porsche-911-technical-forum/1126971-zoidberg-my-1978-911sc-10.html#post12270585

Thank you sharing the link to your thread, I did not know about the rubber bumper adjustments. On my car the right side bumper is stuck, but I was able to unwind the left side bumper and decklid latch released when I pulled the release handle.

I am going to replace the decklid rubber bumpers with new ones. Thank you, jrwilson!

On Pelican Parts, the rubber bumpers are called "Hood Stop Buffer"s, part number 9P1-823-499-OEM (I ordered the Porsche part, there are other OEM brands available).