deezel Posted November 3, 2003 Report Share Posted November 3, 2003 Ok, I caved in and decided to try the DirectHits ignition system. Got it from our local "dealer" tbyrne. BenKey asked about this in another thread, but I figured I'd start a new one for a new topic. I like 2 things about this system - 1. In theory, the capacitor produces a much faster ignition pulse, which should be good for high RPM's and better timing control. 2. Its just as easy as changing your plugs and wires, no extra boxes or wiring to install. In the pic you can see the directhits capacitors with the plug wires attached (little black cylinders with white 12-point heads). After I first installed them, I thought I noticed a little more "pep" at low RPM's. Perhaps "more responsive throttle control" is a better description. Now that I'm used to it I don't notice any more. I tried doing some EFILive logs before and after the install to compare, but can't determine a difference. I don't think I logged enough WOT runs before the install. Since the install I have tried to get a few comparison runs, but I keep getting knock retard about 3 out of 4 times I go to WOT. The KR ranges anywhere from less than 1* to a worst value of about 7*. I'm running 93 octane...? I'm no tuning expert, so these questions may seem ignorant... Does vehicle state affect likelihood of knock? In other words, if I'm driving at 10mph then floor it, will I get the same knock as WOT from 0mph? Does anyone think that the DirectHits could be causing knock or artificial knock? I may have to switch back to the OEM plugs and wires to get a better comparison. Link to comment Share on other sites More sharing options...
Farmtruc Posted November 3, 2003 Report Share Posted November 3, 2003 How long are those things supposed to last, do they go bad after say 100K miles? Is the life expectantcy comparable to a plug? I've seen KR under all conditions. From a stop, then punching it (then it usually goes away), going up a hill in OD (lots of load and low rpms), just through the mid range, and like most see it, at high rpms at wot. It'll pretty much shows up when it wants, lol. Whoever you decide on to do your tuning should be able to get rid of it for you. KR is usually a symptom of running too lean. Check your ltrims and o2's. Your ltrims should be negative, around -5 or so, and your o2's should be about 850mv (that o2 volt reading is with autotap and efilive, they aren't accurate). Good luck with your truck, allen Link to comment Share on other sites More sharing options...
deezel Posted November 3, 2003 Author Report Share Posted November 3, 2003 How long are those things supposed to last, do they go bad after say 100K miles? Is the life expectantcy comparable to a plug? They don't list mileage, but they claim lifespan of the vehicle. Basically you replace the factory "resistor" type plug with a non-resistor plug that has a capacitor screwed on top of it. If the capacitors are well made, they should last a long time. Allen, thanks for the input on KR. I'm running about 880-890 on the o2s and my ltrims are positive around 3 to 5. I don't have a tuning/programming tool yet, so there's not much I can do about advance or AFR right now. Link to comment Share on other sites More sharing options...
SuperSport Posted November 4, 2003 Report Share Posted November 4, 2003 Hey deezel, I had a set on my 8.1L, and still have them can you tell me what kind of plug and what the part# is for the 6.0L. Let me know if you find out if they really help or not. Link to comment Share on other sites More sharing options...
deezel Posted November 4, 2003 Author Report Share Posted November 4, 2003 The directhits part# is the same for GenIII V8's (4.8L to 8.1L). The plugs that came with my set were NGK tr55's. As far as ignition upgrades go, I was just taking a chance with this product and trying to avoid installing a much more complicated system. I can't complain about it at this point. Some folks will tell you that our stock ignition system is just fine for mildly modded engines... Link to comment Share on other sites More sharing options...
marc_w Posted November 10, 2003 Report Share Posted November 10, 2003 A technical member of the Avalanche site was having problems with KR with DH's. He suggested that it was possible the DH's were producing such a hot, fast spark, that it was triggering KR. I don't know what to think of that. The DH's were a fairly quick fad over there. Many people were just as happy buying a good set of plug wires. Link to comment Share on other sites More sharing options...
deezel Posted November 25, 2003 Author Report Share Posted November 25, 2003 Update on DirectHits ignition... I have tried several things to combat the sporadic KR I am seeing - PCV catch can, checked all the plug wires for good connections, checked for loose tranny lines that might be rattling. No change so far, although I remember 1 post where a guy said it took almost 2000mi to clear up after he added the PCV catch can. Next I tried some 105 octane unleaded - ran the tank down to empty then added 5 gals of 105. I drove around for a while to allow the gas to mix well with the gallon of 93 still in there, then did some logging. My peak KR went down from 7-8* to about 3*. Still get KR sometimes and no KR other times. Next step was to remove the DirectHits and replace with new plugs and stock wires. The plugs that came out didn't look too bad - no fouling, no obvious signs of detonation, look slightly lean if I understand how to read the fuel film line correctly. Still get sporadic KR usually starting around 3500rpm in 1st gear. Peak KR still around 7-8*. The KR usually only shows up when I go quickly from low throttle position to WOT. I don't hear any pinging, even with the 8* of KR kicking in. I'm thinking tip-in knock (?), or maybe I just need tuning. CONCLUSIONS: - The DirectHits capacitors are not causing my KR. - I did not observe any huge gains with the DH system. I suspect the initial "perk up" that I noticed was mainly caused by resetting the PCM during the DH install. This would have zeroed the fuel trims and made me a bit richer for the first few drive cycles until the LTFT's readjusted. - If I can get a better tune running I may try the DH again. Maybe the slight improvements they claim (2-3mpg and +10ftlb trq) will be noticable when the tuning is dialed in. Link to comment Share on other sites More sharing options...
zippy Posted November 25, 2003 Report Share Posted November 25, 2003 what was wrong with the stock ignition? Link to comment Share on other sites More sharing options...
deezel Posted November 25, 2003 Author Report Share Posted November 25, 2003 hi zippy, I really didn't think there was anything wrong with the stock ignition. I was just hoping that the DH would be a slight step up - I liked their claims about burning cleaner and more spark energy. This seemed like a good compromise - no extra control boxes or big caps like "major" ignition upgrades. I figured that I would be getting plugs and wires anyway, so the DH system was plugs+wires+about $160 extra for the capacitors that fit onto the plugs (about $20/cylinder for the caps). Link to comment Share on other sites More sharing options...
BluHawk141 Posted November 27, 2003 Report Share Posted November 27, 2003 When you are seeing 8 degrees of knock retard remember that the computer over compensates for any detonation detected. It usually pulls twice as much timing out. How long is the knock retard lasting, how long of an rpm band? Link to comment Share on other sites More sharing options...
marc_w Posted November 27, 2003 Report Share Posted November 27, 2003 Excellent detective work, deezel. Link to comment Share on other sites More sharing options...
deezel Posted November 27, 2003 Author Report Share Posted November 27, 2003 Answering BluHawk's question about KR. When I get KR I almost always get a single hit - one peak that decays with time (I have seen a double hit once or twice). The decay seems really long, and usually lasts until I release the throttle. So, the KR comes in at ~3500rpm, peaks ~4000rpm, then decays through the 1-2 and 2-3 shifts until I release the throttle. Link to comment Share on other sites More sharing options...
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