CIS to ITB EFI conversion

[2svnhvn]

I can’t thank you enough for your extremely detailed account of your journey from CIS to ITB EFI. I am about to make s similar journey from Webers to ITB EFI . Being more of a nut and bolt guy, your post has removed most of my “ oh ***** what am l in for “ to yeah maybe l can handle this. This forum has an incredible amount of knowledge on it, and l greatly appreciate your incredible contribution to it.
Thank you,
Pete

[dannichols1474]

Pete,
Thank you and good luck with your project!
Dan

[al lkosmal]

Dan,
thank you again for posting. You did such a great job spooling up on the install/tuning etc....and provided one of the best write-ups i've read. You set an example for others that are interested in this type of EFI system......... being open and committed to learning, combined with a very good DIY mindset and skillset, you were able to de-mystify the process and show others how to be successfull........you rock!!!
regards,
al

[dannichols1474]

Al,
Thank you. I wouldn't have even tried to do this conversion project if you (x-faktory.com) hadn't put together and offered the conversion kit along with excellent documentation and email support answering my many questions. Thank you. Dan

Part 10

Now for a tuning update:

In Part 9, I described how I had found some driving conditions on a run in the hills near where I live that were causing problems with balking and hesitation. Over the last 2 days, I have spent time with my PC connected to the ECU looking at the conditions in the tune file.

The first area I needed to address was the acceleration enrichment (think accelerator pump on a carburetor). The tuner at the dyno shop had used a feature called "TPSdot Uses %WOT" which enables a curve to model effective 100% TPS for a given RPM. This allows smaller throttle movements to be more responsive at lower RPM's and ignores changes in throttle above "wide open". The problem was the curve was set so tight that at idle the TPS Accel Enrich would kick on and off and caused the idle to be erratic / not steady. I played around with the values in the %WOT (percent wide open throttle) table, but I just couldn't get it to settle down - I think the root of the problem has to do with noise on the TPS signal. The TPS gauge on TunerStudio app also has a digital readout of the current value. I watched the TPS gauge with engine idling and TPS at 0% and the digital readout jumped around from -.5% to +.9%.

Given the environment in the engine bay (heat, vibration, etc), some variation in the sensor outputs seems normal, so I turned off the "TPSdot Uses %WOT" option and started playing around with the Time-Based Accel Enrichment settings. First, I added MAP based acceleration enrichment so now the acceleration enrichment is a 50% / 50% combination (this is adjustable with a sliding bar) of changes in the intake manifold pressure and the throttle position. I made this change so the acceleration enrichment wasn't relying solely on 1 sensor's inputs. Then I set the threshold values for MAPdot (kPa/sec) and TPSdot (%/sec) and the values in the "Added / MAPdot" and "Added / TPSdot" tables so that the TPS Accel Enrich and MAP Accel Enrich functions would momentarily become active (the injector pulse width jumps from 2.5ms to 10ms then returns to 2.5ms) when I whapped the throttle, but would not be active while idling and during warm up. If the engine hesitated when I whapped the throttle, then I adjusted values until the engine revved up smoothly with each whap of the throttle (Whap = sudden opening then closing of the ITB throttle butterfly valves).

Next, I got in the car with the PC on the passenger seat still connected to the ECU with the TunerStudio app running and started the Auto Tune function and began driving. I literally headed for the hills and started up some steep grades with revs in the 1800 to 3000 rpm range, accelerating then decelerating and all the while the Auto Tune program was updating the values in the VE table (volumetric efficiency table - tells ECU how much air is going into the engine for a given rpm and intake manifold pressure) so that the actual AFR (air fuel ratio) as measured by the O2 sensor matches the target AFR in the AFR table. And joyfully there was no more balking and hesitation, the car pulled strong each time I asked it to. I drove the hill loop twice and each time the car ran well. I captured a couple of screen shots from my PC:



I drove back home, burned the changes to the VE table on the ECU, and put the car away in the garage. I went back to my PC and from the TunerStudio app I used the compare tune feature to look at the values in the VE table before and after running Auto Tune.



What I found was most of the cells with changes had lower values after running Auto Tune which means the VE table was over estimating the air going to the engine so the AFR was too rich.

[zaphodtheprez]

Great write up Dan. I'm finding my experience similar to yours in many ways and learned a few things from your experience.
I also owe a lot to Al and Rama, I just couldn't have done it myself without their setup and support.
I made some changes to Al's package to be more in tune with my long term goals.

After a full summer of road tuning and adjusting it's running well on the road. I'll get to a dyno eventually.

[dannichols1474]

Part 11

More tuning. I made a second longer tuning run in the Santa Cruz mountains above Felton and got the VE table tuned in for higher revs at mid to higher, but not full loads. I have also spent a few more sessions in the garage adjusting the acceleration enrichment.

I have found the dyno tuning did a very good job of dialing in the VE table at full load especially up near red line (6500 rpm). See comparison of current VE table versus the final VE table from the dyno tune:



As for the acceleration enrichment, I overcomplicated my life by trying to blend the MAPdot (kPa/sec) enrichment with the TPSdot (%/sec) enrichment. When I lowered the MAPdot threshold to kick in right off idle with sufficient fuel added, the MAP Accel Enrich would trigger during warm up and the engine sounded way off song. So, I went back to TPSdot enrichment only and then varied the fuel add pulse width and the TPSdot table until I got a good response when I whap the throttle. I need to check this set up with my next test drive.



I have found I need to be patient and continue driving the car in varied conditions with Auto Tune to get good all around driveability while maintaining the WFO performance from the dyno tune session.

[dannichols1474]

Part 12

Important note: On my ITB EFI set up, I am using a Pertronix Ignitor instead of the original contact points. The Pertronix Ignitor, which prior to the conversion used to trigger the factory CDI module to fire the ignition coil, is now serving as the crankshaft position sensor (CPS) for the ECU. In order to ensure a clean CPS signal the ECU uses a shielded single twisted pair cable with the shielding internally grounded to the ECU ground connections (which are connected to the ground terminals of the ECU power panel) and the CPS wire connected to pin#2 of the left EFI connector block.

In order to ensure a clean CPS signal from the Pertronix Ignitor in the distributor, a shielded single twisted pair (20 gauge) cable was used with a bullet connector to the Pertronix Ignitor signal wire (the black wire) at the distributor and the other end of the shielded single twisted pair cable was connected to pin#2 of the left EFI connector block. The shielding for this cable was grounded to the engine at the left camshaft chain cover.

Now more about tuning: This afternoon I made another 90 minute run in the hills with my PC running the TunerStudio app while connected to the ECU. I used the Auto Tune program to tune the VE table and made more adjustments to the acceleration enrichment to get better tip-in response when I whap the throttle from idle with no load.

Important note: from the online help for Auto Tune, it is suggested that you run Auto Tune with the acceleration enrichment active as you would while normally driving the car. So when I made changes to the acceleration enrichment parameters, the optimum value of a given cell in the VE table to achieve the target AFR could change, so I ran a pass of my hill course with Auto Tune running after each adjustment of the acceleration enrichment parameters.

Then once I was satisfied with the car's performance on the hill course, I saved (burned) the Auto Tune corrections to the ECU's non volatile memory and turned off the Auto Tune program and drove around town and on the freeway observing the car's performance while monitoring the TunerStudio gauge cluster.

This is an iterative process of making tuning adjustments and testing the resulting behavior of the car using as many driving situations as possible to ensure the best overall combination of driveability and performance. The following are screen shots of my current tune:

[dannichols1474]

Part 13
It has been 2 months since my last post. My car with ITB EFI starts easily and runs great without further tuning.

In the 16 years I have owned my 75 911 Carrera I have focused on more power and better handling but I have left the brake system stock. So I got to thinking, more go power needs more stop power and I began looking into brake system upgrades. After some research, I chose to upgrade my brakes with 4 piston units from Wilwood Engineering.

I wanted a conversion kit for both front and rear brakes that would allow me to retain the original 15 inch Fuchs wheels. From the Wilwood website (wilwood.com), I searched for brake kits by vehicle and started reading through the documentation for the front brake kit and the rear brake kit for my 75 Carrera. During this process of reading specifications and wheel clearance diagrams and then going out to the garage and taking measurements of my wheels and existing brake system, I discovered that my October 1974 build 1975 Carrera is fitted with "M" front struts and not the "S" front struts that the Wilwood vehicle selector guide assumed (M struts have 3 inch spacing for the caliper mounting bolts while S struts have 3.5 inch spacing). Fortunately, if I searched for a 1974 911, Wilwood's selector guide gave me the opportunity to select the M strut or the S strut and I was able to find the correct front brake conversion kit for my car. The rear brake kit selection was more straight forward as there is only one type (which uses 3 inch spacing).

Once I figured out what brakes I had, next was to choose either the 11.10 inch diameter rotor kit (stock size rotor) or the 12.19 inch diameter rotor kit for the front. Both kits were specified for a minimum 15 inch wheel so I carefully measured the inner diameter of the front and rear wheels, then compared those measurements with wheel clearance diagrams for each kit (11.10 inch front, 12.19 inch front and 11.4 inch rear). It turned out that the 12.19 inch big brakes would technically fit inside my 15 inch Fuchs front wheels but I would have just .090 inch clearance between the caliper and the wheel (Wilwood specifies .080 inch minimum clearance) which wouldn't leave room for the stick-on wheel balancing weights on the wheels so 12.19 inch rotors were out. I selected the 11.10 inch front kit and opted for slotted and cross drilled rotors front and rear.

I called Wilwood and placed my order. Boths kits were in stock and I received them 2 days after I placed the order (I live near San Jose, CA and Wilwood is in Camarillo, CA (near LA) so fairly short shipment). Both front and rear brake kits with tax and shipping cost just shy of $2500.

Wilwood provides clear and easy to understand assembly instructions, but just as with the CIS to ITB EFI conversion kit, you need a good understanding of the job and prior experience installing and working on brake systems is very desirable if not a must. I won't go into the same level of detail on the installation as I did with the ITB EFI, but be prepared to do several rounds to mock ups - put it together, check the fit and clearances, disassemble, adjust the shims and repeat until you have the caliper centered left to right over the rotor and the outer edge of the brake pads are flush with the outer diameter of the rotor.

A couple of more thoughts: Wilwood specifies red Loctite (highest strength thread lock) for the caliper mounting bolts which is great if you don't plan on having to remove them but I prefer to use the blue Loctite (medium strength).

The lower mounting bolt on the rear calipers is in a tight spot with minimum clearance from the cast aluminum hollow rear control arm and I had to use a 19 mm standard depth socket and a 3/8 inch drive non rachet bar to loosen the lower bolt (ratchet won't fit and a box / end wrench doesn't have enough clearance to move). Then after removing the upper mounting bolt and rocking the caliper away from the rotor then back to the rotor as I unthreaded the bolt with my fingers, I was able to finally remove the lower mounting bolt and remove the rear caliper. Then removing the rear rotor (by unscrewing the pair of flat blade screws - used a hand impact tool and hammer to get them loose) and removing (and discarding) the dust shield and you then have enough room to use an box / end wrench to install the new caliper mounting bracket.

I find it easier to work on one wheel at a time from disassembly, mock-ups, assembly, brake bleed and pressure / leak test. So I jacked up and secured with jack stands the right side of the car and did the right rear followed by the right front, then repeated the process of the left side of the car.

Original brakes




New brakes




Brake bleed set-up for one person brake bleeding



Repainted the wheel centers with black semi-gloss for freshened look



New brakes after two test drives with light and moderate brake cycles and begin brake pad / rotor bedding process

[al lkosmal]

Good write up Dan. I am considering WilWood for my current project and it would be great to hear your review after bed-in and some driving time.

regards,
al

[dannichols1474]

Part 14
Some additional info about the brakes upgrade: The original brakes were equipped with brake pads measuring 2.25 x 1.5 inches for an area of 3.375 square inches (one pad). The Wilwood front brakes (part number 140-16946-DR) have brake pads with an area of 4.875 square inches (one pad) and the Wilwood rear brakes (part number 140-16680-DR) have brake pads with an area of 5.5 square inches (one pad). That is a increase over stock of 44% in the front and 63% in the rear. More brake pad area means more braking power.

The final two items I addressed in the makeover of my 75 Carrera was weight reduction and replacing the stock steering wheel with a MOMO steering wheel (which also took off 3 lbs).

The bulk of the weight reduction was in the front trunk where I removed the collapsing spare tire (48 year old rubber - never going to use it, 35 lbs) and the electric tire inflation pump (3 lbs). Next I replaced the Lead AGM battery with an Antigravity H6/Group 48 Lithium car battery (15 lbs versus 45 lbs - 30 lbs savings).

The CIS to ITB EFI conversion trimmed 10 lbs out back (heavy CIS fuel distributor versus billet Aluminum ITB's). The billet Aluminum Wilwood brake calipers versus the steel stock calipers saving 3.5 lbs at each corner for a total of 14 lbs.

In total, I was able to drop 95 lbs off the weight of the car (lighter is quicker).

Stock versus MOMO steering wheel



Lightened front trunk area

[scarceller]

I'm curious what the kpa manifold pressure reads in 4th gear 3000RPM on flat stretch of road? It's important to understand where in the ignition table this steady state driving lands. I think you may actually benefit from more timing ignition in that area of the ignition table.

Here's an excellent well written book on tuning, probably the best book ever written. The author Greg Banish was my tuning mentor when I developed my MAF system for the 84-89 3.2L
https://www.amazon.com/Engine-Management-Advanced-Greg-Banish/dp/1932494421
After all the work you have done so far you will really appreciate this book.
It goes into great details on dyno tuning part throttle maps on a load bearing dyno like a Mustang or DynoPak dyno.

Nice job so far on this project!

[mysocal911]

Originally Posted by scarceller

I'm curious what the kpa manifold pressure reads in 4th gear 3000RPM on flat stretch of road? It's important to understand where in the ignition table this steady state driving lands. I think you may actually benefit from more timing ignition in that area of the ignition table.

Here's an excellent well written book on tuning, probably the best book ever written. The author Greg Banish was my tuning mentor when I developed my MAF system for the 84-89 3.2L
https://www.amazon.com/Engine-Management-Advanced-Greg-Banish/dp/1932494421
After all the work you have done so far you will really appreciate this book.
It goes into great details on dyno tuning part throttle maps on a load bearing dyno like a Mustang or DynoPak dyno.

Nice job so far on this project!

Here's what the "Pro-Tuners" do to get that "new" HP; https://www.systemsc.com/tests.htm

Never knew that "tuning" a stock engine is basically that simple. Interesting what you can discover by an internet search!

[dannichols1474]

Hi Sal,
I don’t know the manifold pressure at 3k rpm 4th gear on flat road, will try and see. When the engine is warmed up, it idles at 45 kPa. Thanks for the book link. I ordered the book on Amazon and will get it Friday.

[jbscheff]

This is an amazingly detailed and easily followed write up! Well done.

I too wanted to convert my 3.0 CIS to EFI, but I didn’t have your patience. Fortunately Al was only a couple hours and a ferry ride away so I had him build me an ‘option 2’ system like yours, but with PMO stacks. Since I have a 73 RS clone, I wanted one that evoked the look and feel of an mfi 2.7, so I found an intake that would fit up with the PMOs. It’s not exactly like a 2.7, but it looks ‘right’, sounds fantastic, and goes like hell.

After fine tuning on a dyno the engine puts out a very respectable 190hp and 186ft-lb, with a nice flat torque curve.

[montauk]

Great write up. In all my searches about CIS conversions, I never saw this one. Thanks
Dave

[fanaudical]

Thanks, Dan, for the fabulous write-up and detail. I've somehow missed this thread until today. Like you in the beginning, I've been thinking about upgrading my CIS for years and this has helped tremendously to de-mystify the process.

[Tippy]

Vote to sticky the post.....

I too BTDT, got the T-shirt

[montauk]

Does anyone have any experience with this product?
https://www.ebay.com/itm/373963592035

It's got electronic throttles.

[Tom_in_NH]

Originally Posted by montauk

Does anyone have any experience with this product?
https://www.ebay.com/itm/373963592035

It's got electronic throttles.

Looks nicely done. The throttle bodies appear to be MV Agusta 800 triples. Not sure of the bore diameter.

[Tom_in_NH]

I reread the listing for the above throttle bodies and see that they are 47mm bore.