[al lkosmal]

Dan,
Thanks for posting your experience with EFI/ITBs. Opinions differ, but you present facts/data clearly showing that decent power increases can be made on a stock engines with no other changes made..... and EFI/ITBs, combined with modern engine management offers superior tuning and....they are very cool

Originally Posted by dannichols1474

I have a 75 Carrera that I bought in 2006 and ran with CIS on the original 2.7 engine for 16 1/2 years without trouble other than a little hard starting on cold early spring mornings. The car ran good, but I grew up around my uncle's 64 356C and I really liked the dual carburetor look so I decided to explore a CIS to ITB EFI conversion.

I looked around to see if anyone had already worked out the conversion process and was selling a conversion kit. I found Al Kosmal and x-faktory.com on an internet search and made contact. Long story short, I bought one of Al's conversion kits with RHD ITB's and a MegaSquirt 2 ECM plus an MSD Streetfire CDI box to control the fuel injection and the ignition timing (I am still running my original Bosch distributor with a Pertronix ignitor and the mechanical advance locked).

From the beginning of the project I decided to use a dyno tuning shop to tune and quantify the results of my conversion. I ran a baseline pull to see what the CIS 2.7 was running to start. Then I removed the CIS and installed the ITB EFI system and started up the motor set the ignition timing offset and balanced the ITB's followed by dyno tuning. At this point the car ran great at WOT and max power at the wheels went from 175 with CIS to 192 with ITB EFI (9.7% gain). I soon found the tune was not quite right at part throttle / moderate load, but I was able to improve this situation by making a couple of tuning runs using Tune Analyze Now! the VE table auto-tuning feature in the Tuner Studio MS Ultra app.

In January of this year I decided to rebuild my 2.7 into a 2.8 with bigger cams, etc, so I repeated the process above with the rebuilt engine. Because I am using bigger cams with more overlap and less vacuum signal, I had to modify the MegaSquirt ECU program to use throttle position instead of intake vacuum for the load sensing signal, but the rest of the start up process was the same: set timing offset, balance the ITB's, and dyno tune and test followed by auto-tuning on the street.

Since I installed the ITB EFI in June 2023, I have logged over 3700 miles. During that time, I have not had to re-adjust the ignition timing nor re-balance the ITB's (I have checked the air flow at idle before auto-tune test runs).

The RHD units are high build quality, but the ITB balance fine adjust screw and locking nut on the cylinder #1 / #4 ITB are very close to the idle speed adjust screw on the cylinder #2 / #5 ITB, so close I couldn't get a wrench in to tighten the locking nuts. I remedied the situation by replacing the locking nut with a spring on the #2 and #5 idle speed adjustment screws (think idle speed or idle air / fuel mixture screws on carburetors).

For more details see the thread I reference in my signature block below.