Setzer

Hi Folks,
I am at the preliminary stages of assembling a stroker to go into an l-jet car. Greg advises me that the AFM probably wont be able to handle the fueling which I fully believe. Since I already have a new l-jet harness and I'm inclined to not mess w/ the entire system, I went in search of other options and found a product from SplitSecond. Apparently this allows you to convert an AFM to MAF and has a programmable map. Has anyone tried running one of these? I called and they asked me to take voltage readings w/ door open/closed so they could provide the right unit but said it should otherwise work. Thoughts?

AFM to MAF: https://splitsec.com/product/psc1-004-programmable-signal-calibrator

GregBBRD

Good thought, Matt.
Lindsey Racing offers a conversion, similar to this, for the 951 engines and it works great.
The main problem, in the 951 application, is that everything is right out front and visible...so impossible to get through a smog inspection (if that applies to you.)
In a 928, seems like all of the pieces could be hidden and no one would ever know.

Setzer

For better or worse, smog is an issue. I moved from NY to LA county about a year ago. I figure that limits my choices to upgrading to LH/EZK or trying one of these units. I guess the downside to this unit is that there isnt any control of timing/spark and no knock sensor. Given the price, figured it was worth considering.

GregBBRD

Of course, with a L-jet engine, ignition timing is controlled by moving the distributor, instead of a computer deciding what you need, which can be both good and bad.

A tiny little bit too much ignition timing is really bad, in an early 928 engine that has higher compression ratio. The "Euro" cast pistons are renouned for breaking the ring lands, from just a few degrees too much timing.
With a stroker engine that has forged pistons, there's a much larger tolerance for small errors in ignition timing.That being said, knock sensors, with the ability to pull timing out, from day to day, are a really nice thing.
As I've discussed (some) the issue with pre-programmed knock sensor systems, in an engine with forged pistons, can be problematic. The knock sensors can be fooled by piston slap and end up pulling timing out when it is not necessary.
I've worked closely with CP Carrillo to develop a piston material and design which has reduced piston to wall clearance (compared to our older design forged pistons), to help with this issue.

Some will argue, that using an "added" on knock sensor system, so you can listen to and tune your own knock sensors, is an acceptable approach.

Personally, I've found listening to and figuring out knock sensors to be very tedious and very time consuming. And if the weather changes, knock detecting must be done again. Additionally, if you decide to drive the vehicle to a different location (where fuel may vary) knock sensing must be redone.
Most of the time, aftermarket knock sensor systems just sit unused and ignition timing is set very conservatively, leaving considerable performance "on the table".

This is why I prefer to use the Bosch knock sensor system, found in the '87-'95 cars, and work on reducing piston slap to a minimum.

Petza914

I put a knocklink kit into my supercharged K-Jet '79 with 4.7L block and 4.5 cams. I started at the factory timing settings and backed the timing off a few degrees at a time until under full boost and hard accelerstion I no longer get the flashing "knock detected" light. I am also using a newer distributor that has both advance and retard vacuum ports. By T-ing a line off the manifold (same connection that feeds the boost gauge) and connecting that to the advance port on the distributor, the positive pressure when under boost pushing on the advance side (rather than vacuum pulling on it) retards the timing a bit automatically when under boost, which is when detonation would be more likely. This let's me run a little more timing advance for regular driving when not in boost and still protects the motor under full load and fueling.

How I did the install is in my "Blown / Damaged Head Gasket?" thread.


Knocklink Kit

Knock sensor on block. Actually had to move it to the front hole position to clear the K-Jet fueling shoe.

Notification light in unused pod switch position (convertible)