Holly HP EFI book/ article on tuning timing and map preasure

[chpr1972]

On a vacuum control distributor, vacuum advance gives you fuel economy. All I can find on youtube and Holly is basic fuel tables and not tuning the timing advance. There are a lot of us out there do not care if my motor makes an extra 15 HP at 6000+RPM! I want to get 15+ MPG. These tuners around here are LS tuners and have no idea what/how the old vacuum advances work! They think 35 degrees is too much advance. Where an old vacuum units run 36/38 mechanical advance and 15 degrees of vacuum advance. I am ready to go to a old style distributor to see if I can get some fuel economy. Here is what I am running. A 66' Lemans conv with a 489 CI 10:1 compression, 230/236 510/520 roller cam, dual throttle bodies on a tunnel ram on iron closed chamber heads, TKO600 and 3:50 9". I built it to run on regular gas and at 1200 RPM in 5 gear at slow acceleration it does not spark knock! At this rpm I should sound like a model T!

[btmatt]

we programmed vacuum advance in our LS3 megasquirt spark tables. 500rwhp, 1800 rpm @ 75mph and ~20mpg

[ilikeike]

Are you using computer controlled timing now ?
In the HP software just change the timing curve in the high vacuum cruise rpm area of the timing table.

[parsonsj]

Does your system utilize a MAP sensor? If so, then spark tables for timing vs rpm vs MAP is all you need. Adding another variable via vacuum will make it much more difficult to tune without any benefit.

[chpr1972]

Yes, it is computer control stock GM distributor recommended to me when I bought the whole unit. Yes it has a green map sensor. All the parts are from Holly as far as I know. I bought it thru an X holly employee whom opened his own shop. Every tuner I talk to always want the car with 93 gas and not the regular gas that I run. When I mention 43/45 degrees of timing they look at me as I am nuts! I am 73, so I lived thru the muscle car years! Yes! I know, that gas is bad and the car will not run right. Just like unleaded gas will burn valve seats so you have to install new seats to run unleaded! NOT! The car may have hit 80/85 a couple of times passing and I do not recall hitting the rev limiter at 5800 RPM.

[ilikeike]

40~45 advance is pretty common at light load steady cruise rpm with a lean gas saving AFR.
I think most of the base tunes in the Holley software are like that.
If you’re not comfortable enough to make some basic changes in your timing, you might try a different tuner.
Or check out the Holley forum.

[andrewb70]

The Holley EFI systems are speed density, so the X axis is RPM and the Y acts is load (vacuum) measured by a MAP sensor.

What Holley system do you have, exactly?

Andrew

[chpr1972]

It is a HP EFI. I have dual throttle bodies on a tunnelram with 8 TPI injectors and stock GM computer distributor. With all the Holly systems out there, Holly should have fuel injection for dummy manuals. Every thing I find is piece mill so it is hard to put together. I bought this system before Nascar went to FI. So it has been out for a long time. If my understanding is right, HP is a smaller version of Dominator but runs on the same system. My computer "genius" son is too buzy playing games to help, after he agreed to help me. If Finnrgan's 55 Gasser can get 17 mpg I should be able to get close to that. I can tune a carb to get close to 15 mpg as I have done it on another engine I built years ago in a simular car so I understand AF /timing somewhat.

[andrewb70]

Go to my YouTube channel. I have videos explaining the Holley TerminatorX software, which is not that different from the regular software. If you need hands on help, send me a PM, we can discuss.

[chpr1972]

Andrewb 70 moderator What is name on your youtube channel. Sorry , thank you

[andrewb70]

Andrewb 70 moderator What is name on your youtube channel. Sorry , thank you

The link is in my signature.

[KacyZ28]

Andrewb 70 moderator What is name on your youtube channel. Sorry , thank you

Its been a month any update on your mpg?