Advance Timing - 18 Silverado cam/boltons/e85

[plebevac]

Hello,

A friend of mine has a 2018 Silverado 5.3l with aftermarket (medium-size) cam, full boltons, e85/93, and a supporting mail order tune.

We think the mail order tune is conservative on timing advancement & would like to bump the high octane & e85 adder tables by a degree or two in the high load rpm range. Curious to what you guys think...

The high octane table currently shows maximum 22 degrees advance in WOT range (compared to 15.5 in stock tune). The E85 table shows max advance of 3 degrees in WOT range. There is also an advance multiplier table specifically for E85 that was slightly modified by the mail tune...

Looking at various scans, there is 0KR throughout every full throttle run regardless of fuel type (e85 and 93).

Going from 22 to 23 degrees should be fine assuming the KR stays at zero? Was also thinking of one extra degree to the e85 timing adder (from 3 to 4) which I assume would effectively allow the truck to pull a max 27 degrees of timing on e85? When KR shows up just knock down the timing a bit like any other car?

If I were to increase the e85 WOT cells advance from 3 to 4, do I also need to modify the e85 timing multiplier table? Anything else I should keep in mind when adding timing like AFR/e85, direct injected preferences, low octane tables?

Thanks & I look forward to hearing from you guys!

[TriPinTaZ]

You can't tune based on knock response when tuning with E85. It wont knock before it beats the bearing out of the crankshaft. 25 degrees of total timing is a pretty good amount for a heavy truck.

What percentage of E are you planning to run?

[plebevac]

My friend who owns the truck fills with E85 locally. Its the common (51-85%) blend most people get.

I noticed the Flex Fuel Multiplier is strictly for % of ethanol so I left it alone (tuner had already increased these values slightly.

I brought the Flex Fuel timing adder to a total of 4.5 degrees (+1.5) vs. the original 3 degrees. Then + 1.0 / + 0.5 degree in the cells below the middle of the table. Left the part throttle at the default 0 & the ramp up towards the middle default. Left the low/high octane tables the same as before (22 degrees WOT).

I scanned it and yeah no KR anywhere... are you saying you can?t use KR to tune for E85 because when it does knock... you?re boned because the advancement is so high? I?m assuming 1 extra degree isn?t going to do anything crazy. I do know on 93 octane, pulling 22 degrees, it also never showed any KR whatsoever on WOT runs. Was thinking maybe next time they go to the track we could try +1 across the board on the High Octane table (23 WOT) then +1 max on the Flex table (27 WOT/max), that way if they ever fill with 93 again they can still get a slight benefit. Would also be able to see if it even makes a difference.

They had just installed a ported L86 throttle body, ported L86 intake manifold, & a full CAI - so it was hard to tell if +1.5 made a difference. The new intake setup woke this truck up big time... seems to really compliment the cam and other bolt ons. Pulls really hard in the top end now compared to before.

The scans before and after adding timing seemed to show the correct WOT timing in the 26-27 range, up from its previous 25 maximum. I was reading a bit and it seems other people have increased the E85 timing on these trucks with no KR issues at all, but noticed when they went to the track they were actually slightly slower running higher timing. Those trucks were not cammed though so it?s hard to compare. If I get some data from the next track visit I?ll share the results of (25,26.5,27) timing on E85 and if lower is actually better.

The multiplier decimal values seem like they can adjust automatically between what % E is being pumped in. So if it was E51, instead of the 4.5 WOT advance, it would be about a 2 WOT advance on timing.

Thanks for your reply!

Ps: not sure why my apostrophes turn to question marks lol.

[TriPinTaZ]

You can increase the timing until it actually looses power and there still wont be any KR. E85 makes it very difficult to detonate which is one of the great things it does. When tuning with E, its not the same as tuning pump gas. At some point you will not make any more power, then you will start to lose power, and then you will beat the bearings out of the crank all before it knocks.

I'm not saying 27 degrees is an issue, only commenting on why you cannot rely on knock to tell you when you've gone too far on Ethanol. You need a way to measure performance changes to really know the answers to the questions you are asking. Draggy is one way if you don't have easy access to a dyno or drag strip, but the only real way to see how much timing it likes is on the dyno.

[plebevac]

Got it. Thanks again for your help. Much appreciated.