This is actually off topic!!!

My reasoning to use a MSD 6al-2 is the 2-step and rev-limiter built into the ignition. I have run the MSD and the GM HEI ignitions on the same day, same track with only thousands of a second differences in ET's. The main issue with stock at least for an 85 is no rev limiter.

I actually have wireing set up that if the MSD dies I can easily hook up the stock HEI and continue on my way.

PS: I shift at 6200.

 

I wanted to keep my engine compartment tidy so I mounted mine in the drivers side rear storage compartment and used Weatherpak connectors, and ran the harness up the drivers side behind the rocker panel and ran the power wires to a small fuse block behind the battery, it's worked great ever since.

 

I would say that the first faulty assumption is that knock is the only limiting factor in how much timing you can run. Dig a little deeper ( think icreasing cylinder pressure and flame travel).

 

I'm with CFI on this one.

Increasing the advance makes it easier on the ignition, not harder, as the cylinder pressure is lower than it would be later in the compression cycle. If you fired the plugs later (near TDC), then the ignition kV requirements would higher.
Increasing the advance does not necessarily give you extra horsepower. As long as the peak combustion pressure is occuring at 15* ATDC, additional advance is counterproductive, no matter what ignition system you're running.

 

I'm still not sold

 

my basic point was that blanket statements about anything performance related is a faulty assumption. Blanket statements do not forward the discussion

 

CFI merely beat me to the punch in disageeing with the earlier poster's claims.
What, if anything, do you disagree about with CFI's and my comments?

(Not trying to be confrontational. I'm merely trying to get some detail and clarification from you and the earlier poster.)

 

you can't have an opinion that goes against the grain on corvette forum.. end of story..

 

Ah. My mistake. (I really need to read the forum user's manual one of these days. )

 

god forbid you have come across a problem with something or disagree.. you might get banned..

 

thats not it it at all.

First off, to the issue of relaibility. I have had MSD ignitions on 4 cars over the last 15 years. Ranging from my daily driver C4, to our NHRA Stocker. 6AL to 7AL3. I fried 1 in all that time, and it was heat related ( when i was 16 i mounted the 6AL on the inner fender of my 69 camaro, right next to the header. I think 90% of all MSD failures are either heat or vibration related (here's a hint: an MSD comes with vibration isolating mounts, and the case has fins for heat dissipation). The 7AL-3 on the race car is over 10 years old and has never been out of the car (its mounted inside the passenger compartment. Every MSD failure i have ever seen either the box was in the engine compartment, or was screwed to a solid metal surface, or both. the underhood area of a C4 is a very hot place. thats why my 6AL was mounted vertically where the battery used to be, next to the gill vents.

As to the ability to advance the timing with an MSD, thats kind of a trick question. An MSD 9 ( or other aftermarket ignition) allows you to add options that normally wont interface with a factory EFI system, and adjust parameters that would only be accessible to someone burning a chip. Things such as programmable timing curves, staged retards (you nitrous guys love that), boost referenced retard.

To directly address the "more timing" issue, lets look at a few things. "Knock" is a function of three things (without going into the internal dynamics of the engine): 1) load, 2) RPM, 3) spark advance. therefore it is safe to say that the engine can use significantly more timing in low gear, at lower RPM than in high gear at a higher RPM. Alot of this can be controlled in the computer, or it can be controlled in the ignition box. the ignition box ( or its add on component) is far more accessible or adjustable at the dragstrip for the average guy.

 

 

 

[QUOTE=vetteman9368;1571675551]thats not it it at all.

First off, to the issue of relaibility. I have had MSD ignitions on 4 cars over the last 15 years. Ranging from my daily driver C4, to our NHRA Stocker. 6AL to 7AL3. I fried 1 in all that time, and it was heat related ( when i was 16 i mounted the 6AL on the inner fender of my 69 camaro, right next to the header. I think 90% of all MSD failures are either heat or vibration related (here's a hint: an MSD comes with vibration isolating mounts, and the case has fins for heat dissipation). Have you ever noticed that the OEM ignition components aren't anywhere near this fragile? The 7AL-3 on the race car is over 10 years old and has never been out of the car (its mounted inside the passenger compartment. Every MSD failure i have ever seen either the box was in the engine compartment, or was screwed to a solid metal surface, or both. the underhood area of a C4 is a very hot place. thats why my 6AL was mounted vertically where the battery used to be, next to the gill vents.

As to the ability to advance the timing with an MSD, thats kind of a trick question. An MSD 9 ( or other aftermarket ignition) allows you to add options that normally wont interface with a factory EFI system, and adjust parameters that would only be accessible to someone burning a chip. Things such as programmable timing curves, staged retards (you nitrous guys love that), boost referenced retard.

To directly address the "more timing" issue, lets look at a few things. "Knock" is a function of three things (without going into the internal dynamics of the engine): 1) load, 2) RPM, 3) spark advance. therefore it is safe to say that the engine can use significantly more timing in low gear, at lower RPM than in high gear at a higher RPM. Alot of this can be controlled in the computer, or it can be controlled in the ignition box. the ignition box ( or its add on component) is far more accessible or adjustable at the dragstrip for the average guy.[/QUOTE]

I'm very familiar with knock issues. That's independent of the ignition source.
I'm still not seeing anything yet that supports the previous poster's claim that an MSD unit will permit more "engine friendly" advance than production inductive type ignition systems.

 

I would say that the failure rate of opti sparks debunks that theory. Also no factoy ignition is capacitive discharge, so it not an apples to apples comparison. If there is a Factory CD style ignition thY has exemplery reliability in that environment without a method to dissapate heat or isolate vibration, please show me.

 

I would say that the FIRST faulty assumption is that you ***-u-med I thought knock was the only possible limiting factor in how much timing you can run. Ignore the last sentence in the post you quoted, concerning knock. It was needless and counterproductive to the question. The question remains; "I would like an explanation on how the MSD will "allow more aggressive ignition timing".". If you have a less condescending response, then "Dig a little deeper", (think answering the question) and enlighten me.

RACE ON!!!

 

There's a reason you rarely ever see a CD ignition in a production vehicle. Reliability (or, more correctly, the lack thereof).
I don't have an LTx engine, so I don't have first hand experience with that engine. As an outside observer, it seems like the main weakness is the sensor setup, not the basic inductive ignition portion of that. (I am receptive to corrective information if I am wrong about this observation.)
In my cars I run an HEI setup in the '69 427 (stone reliable, with no heat or vibration concerns), along with the stock EST system on my '84 turbo 355. (No worries there either.)

 

i was not being condescending, and i explained my take on what RacerX probably meant in an earlier post

 

oh this is getting good

 

It frequently gets this way when someone makes a claim, and then disappears when someone asks for clarification or proof to back up that statement.

Just my experience.