LT-5 on a Holley EFI

[-=Jeff=-]

Sure but the external trigger wheel would be the more economical than the custom crank


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[XfireZ51]

The ideal would be to translate the 9 slot signal into something an LSx ECM could use to run a CnP setup.
You could also "shave" the balancer for placing the reluctor behind it. However, that may not be necessary depending on how thin the reluctor wheel is. And ATI builds balancers w integrated reluctor wheels.

[Hog]

Originally Posted by -=Jeff=-

Sure but the external trigger wheel would be the more economical than the custom crank


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Obviously, it would be a "while you are in there" building a stroker engine of course.


The 24x reluctor wheels are $24 using p/n- 12552480 and the senor to read is p/n 10456248. It should be noted that these part numbers work with each other. This 24x reluctor actually supplies 2 sets of info at once as there are 2 coded wheels clocked 15º apart, it requires the dual magneto type crank position sensor.
EFIConnection makes a single wheel 24x reluctor in both SNC and BBC crank snout diameters that allow the use of the less expensive single crank position sensors used on the L30/L31 SBC and L29 BBC engines which use the 280kb "Blackbox" PCMs with the 4x crank reluctor wheel arrangements.


or
use the thin GEN 3 24x reluctor which are much thinner or the GEN 4 58x reluctor. 58x requires a 4x cam position senor as well. Chev Performance sells a front timing cover assembly that uses the timing gear that drives the cam for the 4x signal while the 58x reluctor is located behind the balancer(under the timing cover) with both the cam sensor and crank position sensor located in the timing cover itself. Its a nice slick package for the GEN 6 BBC.
Its p/n 19260247


XFire,
yes a converter box would be ideal. Lingenfelter has a box that converts the GEN 4 58x signal destined for the 1 MB PCMs into a signal that's readable by the GEN 3 24x 512 kb PCMs. They also had a box that did the reverse, but it wasn't on the market long, or it was a beta/prototype, details were sketchy. I'm sure Mr. Behan would know more details, whether that info would be for public consumption would be another story.
A reliable signal converter box would be ideal.


The stock ignition is pretty decent though, better than the distributer based single coil based ignitions of the LT1, LT4, 94-96 4.3 V8 L99, 96-2000 L29 454 and 96-2002 Vortec 305-350 rpo L30/L31 that were replaced by the Coil Near Plug(CNP) ignitions og f the 1997 Y and 1998 F bodies, while the BBC 1st got the CNP and Electronic Throttle Control(ETC) on the rpo L21 454 engines used in medium duty trucks starting in 1998. The L21 was used the same year Y body PCM, it electronically was an LS1 Vette PCM driving a 454 GEN 6 BBC. The L21 was dropped for the GEN VII(7) BBC the 496 cube/Vortec 8100.


L21 BBC 454 notice the 4 coils on each valve cover Pictures are from an Ebay auction. The engine didn't sell, but Mike at EFIConnection got a hold of the owner and bought it as an adjunct for his reluctor wheel designs.







And the flat cap distributer which is only used to provide the 1x CMP CaMshaft Position sensor signal and to drive the oil pump.







From GM
Ignition System Overview

The electronic ignition system controls fuel combustion by providing a spark to ignite the compressed air/fuel mixture at the correct time. To provide optimum engine performance, fuel economy, and control of exhaust emissions, the PCM controls the spark advance of the ignition system. The Electronic ignition system has the following advantages over a mechanical distributor system:

• No moving parts
• Less maintenance
• Remote mounting capability
• No mechanical load on the engine
• More coil cool down time between firing events
• Elimination of mechanical timing adjustments
• Increased available ignition coil saturation time

The electronic ignition system does not use the conventional distributor and coil. The ignition system consists of the following components/circuits:

• Eight ignition coils/modules
• Eight ignition control (IC) circuits
• Camshaft position (CMP) sensor
• 1X Camshaft reluctor wheel
• Crankshaft position (CKP) sensor
• 24X crankshaft reluctor wheel
• Related connecting wires
• Powertrain control module (PCM)




The crankshaft position (CKP) sensor is located under the front engine cover. The CKP sensor is a dual magneto resistive type sensor. This sensor is not speed dependent. The dual micro switches monitor both notches of the reluctor wheel for more accuracy. The CKP sensor works in-conjunction with a 24X reluctor wheel. The reluctor wheel is mounted at the front of the snout of the crankshaft. The 24X reluctor wheel uses two different width notches that are 15 degrees apart. This Pulse Width Encoded pattern allows cylinder position identification within 90 degrees of crankshaft rotation. In some cases, cylinder identification can be located in 45 degrees of crankshaft rotation. This reluctor wheel also has dual track notches that are 180 degrees out of phase. The dual track design allows for quicker starts and accuracy.

The PCM also receives a 4X signal from the crankshaft position sensor. The PCM utilizes the 4X signal for the following:

• Tachometer output
• Spark control
• Fuel control
• Certain diagnostics

The CKP signal must be available for the engine to start. The CMP signal is not needed to start and operate the engine. The PCM can determine when a particular cylinder is on either a firing or exhaust stroke by the 24X signal. The CMP sensor is to determine what stroke the engine is on. The system will attempt synchronized and look for an increase in the MAF signal. An increase in the MAF signal indicates the engine has started. If the PCM does not detect an increase in the MAF signal, a re-sync will occur to the opposite cam position. A slightly longer cranking time may be a symptom of this condition.


The Camshaft Position (CMP) sensor is mounted through the top of the engine block at the rear of the valley cover. The CMP sensor works in-conjunction with a 1X reluctor wheel. The reluctor wheel is located under the cap of the camshaft. The CMP sensor is used to determine whether a cylinder is on the firing or the exhaust stroke. As the camshaft rotates, the reluctor wheel interrupts a magnetic field produced by a magnet within the sensor. The CMP sensor internal circuitry detects this and produces a signal which is used by the PCM. The PCM uses this signal in combination with the CKP 24X signal to determine crankshaft position and stroke.


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The stock LT5 wasted spark ignition is excellent, there isn't much powerwise to be gained by CNP inclusion on the LT5, stock or otherwise IMO.
However the upgrade to a flash based PCM is hugely attractive to calibrators of ECM/PCMs. No more chips.

[Route 66]

JUST my 2 CENTS. The LT5 is the best looking motor GM ever put in a Vette,

[spork2367]

Originally Posted by Route 66

JUST my 2 CENTS. The LT5 is the best looking motor GM ever put in a Vette,

You really thought this was the most appropriate thread for that comment? It has nothing to do with holley efi, or efi at all...

[XfireZ51]

Paul,

What’s the reasoning behind your statement regarding any power gains to be had by converting from the LT-5 DIS system?
When I look at CnP, you have:

1. Coils that put out significantly hotter spark than what stock LT5 coils are capable of doing.
2. Hotter spark means wider spark gaps, better AF mixture burn.
3. Utilizing twice as many coils as DIS, dwell times for the CnP coils can be twice as long as for DIS. For higher rpm operation, that provides hotter spark which is where our motors make power.
4. The hotter spark would also have positive implication for forced induction applications.