408 small block mopar (similar architecture to 406 SB Chevy), 175-180 kPa (~10.5-11 psi) of boost on 93 pump gas, 10.5:1 or so CR. How far is too far on timing?

Graph and current timing table below. Wondering how much further we can push it.

You can see in the jagged light blue where I added 2-3 degrees in the (3000-6000, 118-140 kPa) range and the lighter green/darker yellows where I added 2 degrees in the (3750-5500, 161-168 kPa) range. This overall picked up 2 tenths and 3.5 MPH in the 1/8 mile.

Converter is very tight and doing no favors also.

steve you know how this works spark plug reading is key lol

quote:

Originally posted by rusty:
steve you know how this works spark plug reading is key lol

I sent a PM about a half hour ago to Magnethead stating the same.

2BKING

Air intake temp is a big factor. What are you seeing there?

is this a combo that would be 35-38* if it was NA?

To simplify this he is looking for a target max safe timing at 10lbs of boost with a ProCharger. His 408 10:1 compression Mopar would closely relate to a 23* head SBC. This is a drag-n-drive truck on 93 octane pump gas with Holley EFI

I provided my inputs in PM. The only thing I want to see is a picture of the spark plugs ground straps. It has been well over a year since I saw the last couple of plug pics. They had plenty of timing in them. The mark was around the bend, heading for the weld with heat 1-2 threads down.

IMO, the best thing you could do is show the plugs ground straps. Using pump gas, you have a very narrow tuning window.

2BKING

Yea he needs to put a new set in first, he said he cant remember how old they are other than they from way before his last 1200 mile drag n drive event

This is just a suggestion with the graphs you’re posting to make it easier to follow. First, zero the time table to launch. Second, place a curser at max rpm prior to shift or somewhere that has some relevance in your posting. When you place the cursor in the graph, it’ll generate a “marker” on the “table” in relationship to the cursor position.

Here's the most basic/generic rule of thumb for boost vs. timing. 1lb. = -1* of timing; this is from its baseline NA timing for peak power. This is a general rule of thumb.

My engine made peak power with 36* - 38* of total timing. I use 36* as a safety factor! That being said, my bracket tune makes a peak of 15lbs. of boost. My timing is at 18.7* at that level. According to the rule of thumb, I should be at 21*. I would not want to go there! I'm using 100 UL pump gas with a small amount of water/methanol injection in the blower inlet.

My hotter tune with the same boost, but with better fuel (VP MS109 UL). We are at 22* & need about another 2* - 4*, we'll creep up on it in 1* increments. This tune is a good bit quicker/faster than the bracket tune with the same boost. All we are doing is adding a better fuel, more fuel & more timing.

Pretty sure some of this was where Greg Kelley was going with his question.

2BKING

Bryan, do you maintain that 18.7 all the way down the track or does it fluctuate with the level of boost?

quote:

Originally posted by Big Steve:
Bryan, do you maintain that 18.7 all the way down the track or does it fluctuate with the level of boost?

That's my timing at peak boost.

Here's a data log overlay on the timing map from this past weekend. I was leaving around 4,200 instead of 3,400 with the bracket tune. It will give you an idea of boost vs. timing.

2BKING

Looks super conservative unless iats are sky high. I’m more familiar with LS turbos, but this combo should be even less sensitive. General rule of thumb for 93 octane is NA timing until 2 or 3 lbs then down to 14 degrees at 14 psi.

I like Brians posted Base Spark Table that displays MAP as PSIG not kPa. He also has the Overlay feature enabled in Data Log that displays the trace of the run.

To switch MAP from kPa to PSIG in the GCF select “Toolbox” , Preferences, Display MAP as PSIG. To enable Overlay feature, select “Datalog”, Activate Overlay.