My Demon 5.7 hemi carb swap

15 is 1 atmosphere or 100 pressure ratio on the map. I wish they would have left it in pressure ratio like the factory ecm
Stock Msd

KX450 - I've asked around and the general consensus is that your MAP should "flat line" at 11 PSIa (7.53 Hg") - not go under the line.

By plotting it under the line - it is retarding your RPM advance at WOT when intake pressure is highest (Vac is lowest).

Why MSD would "sell" this as a tune is beyond me!

The way I understand it - as Intake pressure increases (PSIa).....Vacuum drops ("Hg)

- but as Swifter pointed out - your timing is being retarded after Intake pressure peaks at 11 PSIa (Intake Vac drops below 7.53 Hg")
you have to transition from cruising timing which should be relatively high to WOT timing which is typically like 10 degrees less on the gen3 hemi's. Pressure ratio is that way is transitions in the stock tune.

The decrease in timing from 6 PSIa to 11 PSIa is understandable -

I can see that as Intake pressure increases - the MAP advance is reduced because the "mechanical" advance is increasing - just as Vac advance backs off as mechanical advance increases under WOT.

Here's what I see happening from 11 PSIa onwards - the MAP chart is actually pulling timing OUT of the total!

So even if the RPM chart is programmed for 28 degrees at WOT at 4000 - IF the intake pressure goes above 11 PSIa at's start taking timing away from that 28 degrees.

Thats the way it seems to me anyhow? :-k
Read this :

A warning about spark tables

The new Hemis neither need nor appreciate a lot of timing advance. We've found that 22 degrees at full throttle is all the advance one is likely to need on race gas, and can be too much on pump gas. The default MS3 timing table is for an older combustion chamber with a much lower flame front speed, and needs to be backed off before you start tuning. I'd start with no more than 18 to 20 degrees at full throttle (100 kPa). I've heard Mopar faithful comment "This engine isn't a real Hemi" - and they should not be tuned with the huge amounts of spark advance a classic 426 would have required. The newer head has a much faster burn rate and is considerably more efficient.

[ame=""]:happy1:[/ame] Demon swap 5.7 hemi drag 1/4

[ame=""]hemi swap drag - YouTube[/ame]

What do you know about that Hemi Demon? If it is a relatively stock 5.7L Hemi than the 13.04 quarter mile time is very respectable.


Joe Dokes
Very Nice. I hope my Dart ends up looking as good as your Demon!
very kool,, i would of thougth more rear wheel hp,, what rear gear are you running to get 21 MPG,,, nice job,,,love the intake,,,, u may want to consider making a few to sell,,,,
What did you do about the dust shield between the engine and the trans?
Do you have any pics or an explaination on the input shaft shortening?

I want to use an 833 in mine and this is my only worry. I saw somewhere it needed shortened and retapered? Who can do this and does it need removed from the transmission?

Thank you.
I did this and it is no big deal--Make good measurements-we used a piece of 1/2 electrical conduit because it fit in the crank bearing very nicely,we used a cut off wheel to cut the shaft and then chamfered the shaft with a grinder(to help the trany slid into the bearing,on ours we needed to remove only about a 1/4 inch--Steve
Well that makes me feel a little better. Haha.

But I guess I'll have to wait and bolt it together to see exactly what and why it needs done. I'm not even sure what I'm to be measuring. :/

But if it can be done at home with a grinder and cutoff wheel and doesn't need to be machined within microns, that's very good news.
Real S.U.V. :finga:


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what head light or bulbs are you running to have that nice blue glow? beautiful build, have a poutine for me i used to live in montreal for a few years
what head light or bulbs are you running to have that nice blue glow? beautiful build, have a poutine for me i used to live in montreal for a few years

My headlight kit:
Now, 10678 miles on this setup without problem
44 run 1/4 mile drag race
12 run 1/8 mile drag race


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