Maximizing Predator performance on an SRT-8

[Mike_Levy]

OKay, I just did this. Seeing 4.5-5.0° of KR in the 4000-4800 rpm band. Do I cut back the spark or add more fuel to get rid of it?

[WA 2 FST]

My honest opinion (which is not from direct experience with the 300C mind you, but from 15+ years of tuning EFI hot-rods) is to add some fuel first. After that, if it doesn't alleviate the problem, I would take out 2^ of timing, leaving the changes in the fuel table intact.

Most likely one or both of these in conjunction will eliminate that amount of knock.

[fionn]

Here in Reno most of the stations use oxygenated fuel, I believe we only use e10 in the winter months. Oxygenated fuel should react to the suggested changes in a similar fashion don't you think? Were you getting KR stock? I get KR stock and with the tuner. I’m a little uneasy about adding timing, if I keep my eye on the KR I should see increased KR before anything blows though shouldn’t I??????

[WA 2 FST]

IMHO, a little pinging on a N/A motor (meaning no forced induction) is not going to kill the engine. What kills engines are excessive rpms and massive detonation under extreme cylinder pressures. A 6500rpm N/A motor is not going to create these types of extreme cylinder pressures... but that's just my opinion.

Hopefully the PCM is pulling some timing anyway once KR is detected, and I would also assume that after a number of WOT runs where KR is detected that the PCM may also default to a lower ignition timing table. Please understand I'm making an educated guess based on years of tuning brand X vehicles. I'd be shocked if DCM's engine management contols are any less sophisticated, however.

I would certainly _not_ add timing when you're experiencing KR.

[immo]

Originally Posted by 300C_Chris

In virginia do you have the 10% ethanol fuel or no ethanol fuel.

It depends on the county. Most places do have the 10% ethanol fuel.

[NeverToFast]

I live in FL.

I added 4% fuel across the board and only running the CAI 91 tune when using 93 octane (trying to reduce timing) and still getting 5 degrees KR!

I'm lost. Nothing seem to help on my car. Only mods are CAI, cats, catback.

[fionn]

I've added as much as 20 % fuel and pulled 15 degrees of timing and still get some KR, as much as 6 degrees. funny thing is my car runs strong stock even with as much as 5 kr (stock). either there is something wrong with my car or the tuner does not like my car and the adjustments don't work properly.

Originally Posted by NeverToFast

I live in FL.

I added 4% fuel across the board and only running the CAI 91 tune when using 93 octane (trying to reduce timing) and still getting 5 degrees KR!

I'm lost. Nothing seem to help on my car. Only mods are CAI, cats, catback.

[DaveW68]

Originally Posted by 300C_Chris

Hey Dave, I'm going to be getting high flow cats, cai and catback exhaust soon, do you know of any good dyno tuner shops around Chicago. Also were these SRT's running the cai performance tune from predator or the performance tune from predator.

I just heard from Firemedic about his adjustments. He has the exact same mods that you are planning and had his car dyno tuned at the same place that Brute SRT did. Apparantly, the higher flowing cats require a tad more fuel to be optimal. There are his adjustments:

Add 4% fuel to all RPM ranges
Add 2% spark to the first 2 ranges and nothing to the 5-7k range.

According to Diablo's website, these guys show up as the only Chrysler CMR tuner in our area:

Hahn Racecraft
1981-D Wiesbrook Dr
Oswego IL, 60543
630-801-1417

[Brute SRT]

Great write up Dave! Happy to be one of your test subjects. You never got back to me on how your car took the adjustments. Hope it helped a little.

I filled up my tank @ Costco yesterday ($3.439 for "Premium" 91 Oct) and i just could not find anywhere anything on the ethanol mix. Where the hell does it says it?

Sorry to hear about your Gramps Dave.

[Mike_Levy]

Originally Posted by Mike_Levy

OKay, I just did this. Seeing 4.5-5.0° of KR in the 4000-4800 rpm band. Do I cut back the spark or add more fuel to get rid of it?

Just got a response from Diablo on this. They're saying to pull the advance. Heres the thread if anybody wants to add to it.... View topic - KR in the midrange :: DiabloSport :: Gas and Diesel Tuning Systems