Continue with CIS or EFI

[outlaw912]

Hey All-
I'm trying to figure out if I should continue struggling with my CIS system or make the leap to EFI. I'd probably end up with the Bitz kit which seems like the best choice and I would be doing the work myself. The problem is I cant seem to get the CIS tuned properly and I never get good throttle response. I've done my fair share of backyard mixture adjustment and can get the car running well but I probably am not taking advantage of all the power the motor can offer. I could bring it to the shop but only get one tune for half the cost of the kit. Any thoughts?

My car is a mix of parts which I'm sure contributes to my problems

71T Motor 2.2L
S Cams
74CIS (No AAR)
915 Trans
Electronic Ignition with Bosch CDI

Any suggestions or horror stories are welcome.

[K Sykes]

I made exactly that switch and have never regretted it. Many folks swear by CIS and can get it to run well, it just wasn't me. It is a lot of work to get it (EFI) right and you can find that you have issues that have nothing to do with EFI that become more obvious once you switch. I have become much more knowledgeable about my car from going through it and there is a ton more room to do regular maintenance without all the CIS hardware.

At the end of it all, I could have gotten to be CIS fluent with all the time invested in EFI, but I am very happy with how reliable my car is now vs under CIS and the flexibility I have to do more - better tuning, adding crank ignition etc..

[Scott R]

Maybe given your circumstances with all the mixed parts I would. But for me when I had EFI I pretty much drove around with a laptop on my passenger seat all of the time. Functioning CIS is really a set it and forget it type thing.

This was the height of my EFI experience it took months of tinkering to get to.

1980 911 SC Tbitz EFI on a new motor - YouTube

[tirwin]

I wondered about the same thing. Last year Franz Blam had an open house for the local PCA at his shop. I asked him his opinion on going to EFI and he was adamant that it was a bad idea. Now we were discussing 3.0L engines and he suggested that the stock pistons were not optimal for EFI if I remember correctly. His advice was to get the CIS working. I also asked about carbs and he wasn't big on that idea either. He basically said that for the cost of making a 3.0 work with EFI, I could buy a 3.6.

Arguably it could be different for a 2.2. I'm certainly not qualified to answer. Just passing on the advice that was shared with me...

[timmy2]

I took a perfectly functioning CIS system off my car and installed a Bitz EFI kit 2 months ago. It takes a while to tune, but now it runs much better and seems to have more bottom and top end power.
I don't know where the piston concern comes from, it is still fuel injection.

[timmy2]

On second thought, if your mechanic will install a 3.6 in my car for $2400 send me his contact info ASAP!

[911SauCy]

Originally Posted by Scott R

Maybe given your circumstances with all the mixed parts I would. But for me when I had EFI I pretty much drove around with a laptop on my passenger seat all of the time. Functioning CIS is really a set it and forget it type thing.

This was the height of my EFI experience it took months of tinkering to get to.

1980 911 SC Tbitz EFI on a new motor - YouTube

~drum roll~

And the @ the wheels #s are...

[Scott R]

Originally Posted by 911SauCy

~drum roll~

And the @ the wheels #s are...

It's in the comments, but 143 was all the Megasquirt guy was able to eeek out of it on the dyno.

[jpnovak]

There is more to EFI that peak numbers. In most cases CIS cars can produce good peak numbers if they are tuned properly at that RPM range.

In fact, most of the numbers reporting improvement are due to non-optimal CIS systems.

When faced with worn out components, out of adjustment WURs, aging fuel heads and leaky injectors it can make sense to convert to EFI.

I can tell you from experience that the throttle response off-idle and presumed power through the mid-range is vastly improved with a well tuned EFI setup.

to the OP... Which S cams do you have? Are these CIS "S" cams or early "911S" cams? Big difference between the two. If the later you are probably experiencing issues with metering plate flutter and confusion due to intake reversion. Yes, you can run EFI with these cams but you will have to take some precautions during the install to get a clean vacuum signal (speed density).

Additionally, the tuning part of the EFI is the most important aspect. Just like jetting carbs, setting the mixture on the CIS or any other system - It has to be setup correctly to get the most benefit.

If it were me, I would ditch the CIS. Especially on your hybrid engine. The Bitz kit makes an excellent choice. I have installed a few and they are very well setup.

[balleta]

If still interested, I have a complete Bitz Racing kit for sale. I bought it for my 3.0 but change my mind and going other route. (Will be installing a 3.3 Turbo WITH EFI).
The Bitz kit is not designed for the 3.3 T and although some parts can be used I prefer to sell it complete and look for a new set of parts for the new engine.
It includes all the parts of the original Bitz kit plus the injectors, the fuel pressure regulator, the gaskets and the manifold rubbers.

Have invested $1,925.00 in parts plus shipping
Will do it for $1,625.00 shipped anywhere in the US and Puerto Rico

[911SauCy]

My car is basically stock CIS with exhaust and intake...and it rips...unbelievable how these little cars go with such little muscle.

Magnus Walker, "You can use all the power...all the time."

[balleta]

CIS is good if everything is working as it was designed 35 years ago. Tuning is limited to few mechanical adjustments. There's no way to fine tune it as with EFI.

Sent from my GT-I9100 using Tapatalk 2

[timmy2]

If you go with any EFI system be sure to get a good wideband O2 sensor. You really can't tune very well without one.