'69E Tuning Input Requested.

[jluetjen]

Since I resolved the electrics dieing problem, I've put a few hundred miles on my car and it runs like a charm, always starts, pulls to 7000 RPM and got 24 MPG on the last tank of gas. Everything is great....

...except the engine feels a little flat and sounds a little flatulent or buzzy between 1200 RPM and 1800 RPM under load. I'm concerned that it might be some detonation. Maybe it's just a result of the MSD's multiple sparks and I shouldnt' be concerned. Here are the details just to recap:

- The engine is a 2.0E with S pistons (per the PO)
- It has the original MFI and the TB's were refurb'd and set-up up by Matt at Eurometrix
- The ignition system is an MSD6AL with a crane optical sensor in the distributor
- The ignition timing is set to 5 degrees ATDC at idle, and advances up to about 28 or 29 degrees at 6000 RPM
- The car idles smoothly at about 1000 RPM +/- 100 RPM
- From 2000 RPM on up the engine runs strongly and smoothly.
- I only run the car with 93 octane fuel

Does anyone else's car do this?
Should I be concerned?

I'm thinking that now's the time to find someone with a chassis dyno in the area to have the car set-up.

Any thoughts?

[RSBob]

You may want to try posting this on the Early 911 S Registry Technical Forum. Many early car experts, and cars of all types, not just S's.

[jluetjen]

I just noticed that a shop about 2 miles from here has a chassis dyno. I'm going to give them a call to see if I can schedule a session.

[boba]

Have you checked AFR thru the RPM range?

I have a '69 E MFI still running Bosch CDI and had Ed Mayo set up the MFI. We did a complete check of throttle linkage to ensure full throttle and found a cracked bushing at the bell crank which looked fine on visual inspection but would slightly separate under load. We then did a complete CMA, adjusted the richness 6 clicks and got it running very well. We then started to check AFR. The primary reason for the adjustment was not due to it not running well before but due to the change to a sport muffler. After setting the AFR taking readings on each bank we found that the right bank was running leaner that the left. Using a digital pyrometer and checking the exhaust port temps we isolated the two cylinders which were a bit lean. Ed was able to open the side of the pump and adjust the pistons for those two cylinders to increase the volume and get all exhaust port temps in the same range. A check ot the AFR showed that the two banks were now equal. It runs great now, set just a touch rich for safety.

Good luck to you on getting yours set. I would do the CMA before going to the dyno, that way you know you are now doing the final fine tuning.

[Grady Clay]

John,

A 2.0E never was designed to run between “1200 RPM and 1800 RPM” except on its way to really pulling from 3500 to 7000 rpm.

Your ‘symptom’ may be an indication of something else (like sitting during your electrical issue) or be nothing to worry about.
Your dyno pull will be good for a data baseline (as will a cranking compression test and repeated cylinder leak tests.)

Go drive!
(Not at 1200 RPM to 1800 RPM.)

Best,
Grady