-------------------------------------------------------------------------------- What are guys recommending you tweak your A/Fwith the diablo on a lightly modded car?? My buddy Is running a Cai, 180t-stat and the 93 canned tune and I reme,mber reading that people found it better to go in annd manually add some fuel with that caned tune. Anyone know what a good a/f for these cars with those mods should be??
12.5-12.7 is optimal, I have the exact same mods on the Jeep and checked the A/F against the canned 93CAIPERF tune and it was dead on 12.4 so leave it alone. Make sure he is running the lates CROM from Diablo and he choses the 93CAIPERF tune. Without a wideband A/F guage installed it would be wrong for anyone to advise you on adding or removing fuel
Why? How does one determine that? Is it most power on a dyno? I've been wondering about this. Diablo said they saw good power down in the 11.8-12.2 a/f range with our engines. I guess 12.2 is the "old school" (at least that's how some refer to it) general rule of thumb optimal a/f? I *think* with our engines, if you're only tweaking a/f and timing you pick an a/f and then advance the timing as much as possible without getting knock retard. If you do get some knock retard the pcm will pull timing to get rid of it. So do the dynos show more power at 12.5-12.7 with less timing than 12.0-12.2 with more timing? Could you shift the power curve picking one or the other? Is 12.0 with more timing going to give you more power/response at higher rpms and 12.7 with less timing going to give you more power/response at lower rpms? Reason I ask is that I ended up tuning for about 12.0 - 12.2 with about 17* timing. My 1/4 times seemed to improve but it feels a bit sluggish out of the hole.
12.7 optimum power 14.7 stoichiometric (best for environment) 16.0 max fuel economy (CAUTION - very lean and too hot for most engines) supercharged or NOS I would use around 10.8-11.0 to 1.
Dave, Anyone who thinks they can retune the canned tunes from Diablo is asking for disaster. Look around the forums and you will find several who did this and had serious issues. If your buddy wants to have something other than the Diablo Canned Tune, then they MUST have an authorized CMR tuner do their thing.
Just curious why you say that Ron? I have been running a modified 91CAI tune for a while and my A/F is great with no KR. I dont see a problem with modifying any tune as long as you have a wideband to monitor your progress.
Agreed plus I was told by Dave @ B&G that our engines produce the most power at 12.6 A/F. I think A/F is just part of an equation to monitor when tuning, some mods may need to run a little richer to keep knock down so in theory their richer A/F reading say like 11.8(nitrous tunes for example) my show more HP opposed to leaning it out to 12.5 but getting KR and pull power.
The guys from Diablosport say otherwise if done properly. Make a "minor" change and then go out and log it. And if need be do it again. They've said countless times that you're not going to hurt anything if you just take baby steps and have a clue.
I have one for ya, EVERY car will be different. One might like 12.0 and another might like 12.4. If I kept the canned tune the way it came I would be getting a crap load of KNK retard. I HAD to modify it. I added fuel and all is well. I think one of the reasons some have to modify the tune and some dont is the quality of the fuel. Where I am in FL it seems the fuel sucks ass and it has 10% ethonal. I had to go to the 91CAI tune from the 93CAI Because I had to end up pulling about 3 degrees of timing and adding 15% fuel to stop KNK. With the 91CAI tune Ive added 9,14,14.5 fuel and added 1 degree of timing accross the board with little to no KNK. I can tell you that the car runs alot better the way I have it compared to the canned 91CAI. Thats just the way things are. Every car is different.
Ask the countless guys who threw a ring or sucked a valve. Mine is merely a word of caution and that the responsibility will be on the end user if things go to melt down. If someone is unexperienced, such as myself, in the tuning area, then it is my opinion to leave it to the experts.
There have been 4 engine meltdowns that I have heard about. All 4 had there KNK sensors turned OFF and were heavily modified.
[umm, Dave, if you would rather I open up another thread with this, just let me know. I don't have any problem with that. I actually have a couple of threads already on parts of this. See "Let's Talk About Knock Retard" and "Help Me Tune My Engine"] Ok. I would LOVE to have this discussion go further than it has done many times in the past. I'm not sure if it's a national secret or there are a lot more factors people don't want to talk about but this always seems to end up with a few differing claims based on some unsubstantiated assumptions (doesn't meant they're wrong) and then it dies. Here are a few. First let's start with some definitions so everyone is using the same point of reference. "Runs best" - I assume this to mean "produces the most power" in WOT open loop mode. Surely one can tune for all modes but the Predator only address WOT fuel and timing and this has the most interest here. Let's go with that. "Knock and Knock Retard" - Knock/detonation/ping/etc. is bad and can do serious damage in a hurry (almost instantly in some cases). Knock Retard is what the PCM does to avoid damage due to knock. The PCM detects knock and pulls timing to prevent it. We all know circumventing the knock sensors is risky at best. Let's assume the PCM is doing Knock Retard as designed. I'm sure there are a boat load of parameters that go into a tune. The Predator mainly addresses fuel and timing in WOT open loop mode. Let's assume we have a base tune suitable for our engine and just look at these two factors. Question 1 (eliminating knock retard): People often say they "had" to tune to remove the knock (knock retard). Or running with a few degrees of knock retard is ok but running with more degrees of knock retard is not so ok and running with a lot more degrees of knock retard is bad. Is running with the PCM doing knock retard any different than when it's not? How? Obviously it's "different" but is the difference significant? Assumably the knock avoidance mechanism we have has some limitations? That is to say it can only handle the situation within a certain range. Anybody know what that is? Let's keep it in terms of degrees of knock retard. People see 2* KnR. People see 9* of KnR. People see 13* of KnR. What's the max? Is timing pulled to eliminate all of the above knock? Is the PCM capable of pulling an infinite amount of timing and just pulls more and more until it's resolved? I don't think so but I don't know. I observed this when tweaking my canned tune. I ended up going with an a/f of about 12.2 across the board. I had about 21* of timing across the board. I was seeing KnR that brought the timing down to about 17*. I used the Predator to pull 1* of timing at a time. The KnR would be less each adjustment. The KnR was zero when I got down to 17* of timing. So what exactly was the difference when I was running 21* of timing with 4* of KnR compared to when I was running 17* of timing with 0* KnR?? Question 2: (does Knock Retard reduce power?) The answer to the above may be the same. People often say that you are losing power if you see Knock Retard. Is this true? Sure you can get more power with actual knock but you're going to do damage so let's assume we stay with no actual knock. If I pick an a/f and then advance timing as far as I can without seeing knock retard will I get more power than advancing the timing further and see some knock retard? I guess the question here is when the PCM detects knock, does it over correct by pulling more timing than necessary? This is not what I've observed on my car. I've got more questions related to this but they're off in different areas. ...and Ron, you DO have experience in this area...:crying:
Dave had mine tuned at 11.3 yeah i know really fat but when I pulled a percent(yes 1) i went to 11.56 and had more knock...he said leave it and she pulled hard...yes all past tense due to having to pull out the b&g since she is getting a new tune here shortly.
Dang it. That ended pretty quickly. I did happen to just run across the following on Diablo's forum. Some member posted what someone else had posted on some other forum. It explains how it works for a GM 3800. Ours could work basically the same way but the values could be different. If ours does work the same way then it wouldn't make a difference if you have constant KnR. If you have bumps of KnR then it could be better to tune it out. Reason is the "recovery rate". It appears that the PCM reacts very quickly to knock detection and then tapers off after the "event". Let's assume you have a knock that's strong enough to warrant pulling 4* timing and then it goes back to normal. The PCM will pull 4* and then start adding it back. The GM adds it back at the rate of 0.8* every second. It would take 3.2 seconds to get back to your base timing. Flip side is that you might not want to adjust across the board for just this spike if it always occurs at the same rpm or something. This is where I think the CMR software gives you better granularity to pinpoint smaller rpm ranges instead of just 3 large bands. He sort of implies that real knock does not occur all at once but ramps up to some point each time it happens. I am guessing that the PCM reacts very quickly and so it probably is pulling 1* at a time but very quickly until the knock trend starts going down rather than up. For example if you see 6* of KnR that doesn't mean you had a knock of 6* "magnitude". It means that maybe the PCM pulled 1* of timing in response to a 1* knock and then maybe pulled another degree in response to another 1* knock, on up to 6*. I'm not sure about this. Here it is. Don't forget the numbers are for a GM and may not be the same for us.
Well these r all good points indeed. Lets consider this though... false knock. Many engines have it and I know in at least my case she has it BAD. When I tuned my car she pulles 10degrees of timing.. NO MATTER WHAT. I can set my A/f to 10-1 and timing at 12 degrees and she pulles 10 for some reason. A/f of 11.4-1 and 26 degrees and she still pulls 10. Now I know that 10 is the most the engine can pull but the reason it is doing it is a mix of the cam/blower grind and headers. It all creates vibrations in the block that the CPU missinterprits as knock. SO be aware.
I was told,,, and so was everyone on dodgetalk. By (sn) dodge3471, If you rev the motor close to red line without passing 50kpa map value you can re-learn the knock sensors for what is normal engine noise. The computer knows it's imposible to see knock at that map value. So it's a re-learn function in the computer. dodge3471 is a dyno cell operator for chrysler. I have not tried this my self. I'd like to see someone with a knock problem to try this
