anonymousagain

a bit OT for NA cars... my '80 is timed by ear to slight detonation, then backed off a tad --> for 87 octane. Should I be considering 89 octane w/slightly more advance?

Considering 87/89/91 cost -vs- performance increase from further advanced, but it seems there's a threashold where gain is more TQ/HP movement in rpm range than overall improvment (similar to MK's experience). Or just simply trying to run cheapER gas than premium as a balance.

You guys sound like you're at 89, yes? Should NA cars "like" 89 or 91 significantly more? or just stick with the 87 where I'm at?

Thanks for the insight !!

hacker-pschorr

My friend has an 84 auto with headers. He runs high octain no matter what, so we cranked up his timing (not 100% sure where, need to check with my new timing light).

Performance increase? 100% new car after that. It used to be a total pooch off the line at stock timing.

hacker-pschorr

Why? Search around a few turbo forums. Step 1 to adding more (or any boost) is closing the gap, not making it wider. Todd who built the 6.0 with 15psi is running .020 on his S4.

This is a good thread on the topic:
http://www.innovatemotorsports.com/f...ead.php?t=3356

Todd also has a 400+ hp supercharged motorcycle he built from scratch (frame, engine, pretty much everything). He was telling me it would off / on miss at the high end until he brought his spark plug gap down to less than .020. On the dyno he lost like 4hp. With these old ignition systems, a tighter gap takes some of the pressure off the system - takes less energy to jump the gap & less of a chance the flame will be blown out.

Not sure - I'll be taking notes tonight at the dyno once it's all dialed in.

anonymousagain

Thanks Hacker!! btw, looking forward to your dyno results... good luck!!

hacker-pschorr

I plan on doing one last run with the A/C on just for the hell of it.

Petza914

Hacker, do I win something for bumping the oldest thread that is the most pertinent to my question ?

In the next couple of weeks, I'll be putting the motor back into my car and will need to set the timing.

The motor is now a mix of motors:

It's now an M28/19 4.7L with the cams from my '79 4.5L and I'll be using the K-Jet fueling setup from the '79. As you k I have Carl's Stage 2 supercharger setup I'll be running too and it now has the upgraded billet impeller, vented case, and upgraded bearings in it.

I'll be running 85/86 round tube SS headers, no cats (Y-pipe instead), to a Borla exhaust.

I'm going to go 1 colder on the spark plug than the standard WR7C that NA 928s run to a WR6C, which should be the same heat range as the NGK BR8ES that I had been running in the 4.5. I'm going to Bosch since I have a bunch of them on-hand.

I always run 93 Octane in the car. So, based on your experience with your car and the dyno testing you did, what do you think I should set the timing to when I install and setup the distributor and do I do that with the vacuum line attached or detached?

Also, do you have a picture of the vacuum line you were referring to that will retard the timing as boost builds so I can make sure I have that line connected if running in the higher timing range? Is this the same vacuum line you disconnect when setting the timing at a certain number or a different vacuum line?

Thanks for the help.

hacker-pschorr

My car is using a completely different supercharger setup than yours. I suggest you talk to Carl and do whatever he suggests.

My testing results may not apply and I'd rather you not damage anything copying just one tiny part of my tuning. I shared that information with Carl many years ago and he didn't find it necessary for his kits.

As far as photos, no I don't. That setup was short lived before I ditched L-Jet and went with LH / EZF from a EuroS which has all electronic ignition control. I was never happy with the overall results with the L-Jet setup and stock ignition.

I never played with CIS with regards to boost either.

j.kenzie@sbcglobal.net

Hi Pete,
I went through timing my 84 L-jet supercharged engine. I was properly schooled to be cautious, then got some help from Hacker on how he set up a retard signal on positive manifold pressure using an older distributor. It's a 4 page thread, but some of it is enlightening.:

https://rennlist.com/forums/928-foru...ercharged.html

Good luck,
Dave

Petza914

Thanks much Dave. Now I have some light reading for tonight

What does the distributor from an 80-82 that has both advance and retard capability look like? Want to see if maybe I have that updated one before considering buying a different one.

Wish 123ignitions made an electronic, fully programmable one like they do for the 914s and early 911s, as that would be ideal.