Wanted to push the envelope a bit this week racing so put in the 150 N2O jet from Zex (.067) per their chart. I have been successfully running a 54 N20/26 Fuel setup with a/f running around 10.8 - 11.8 on 50/50 mix of 93/98 octane gas. Never a problem of any kind. So, when I drop in the .067 jet I up the fuel jet to a .030 and make some runs on the same gas mixture and it pulls hard but my a/f is down around 9.8-10.2 so I say what the hell and drop the .026 fuel jet back in and make a few more runs. Holy cow, batman!!! Pulls like never before and my a/f is 11.8-12.2, so I figure I'm spot on. Go to the pit lane drags at Nashville Superspeedway last night and make 2 practice passes that are just hard and fast. Guy in big turbo mustang is still shaking his head. I am so pumped to race. I actually get lucky lining up and get one of the slower cars so I know I should win. Cut a great light pull 2 cars fast and then... Spit, sputter, spit , jerk, pop, pop, jerk...oh crap...get out and get back in starts pulling again and then spit, sputter, jerk, pop, sputter...get out and stay out. Guy beats me by a fender as I coast across the line but I really don't care as this has never happened before. I have a lean shut down switch set at 15 and it never kicked in and cut the N20. I was not recording a/f on that run because the two test runs were 11.8 - 12.2 range. I probably had 2 gallons of 93 when I got to the track and added 4 gallons of 98 when I arrived. N20 pressure was good at between 950-1000psi. Two test runs were perfect...what the heck happened? On the drive home I got a "misfire" CEL that it the one I used to get when I first installed my 268 cam. Jeep ran strong on the way home. Any ideas on what happened? I'm going to go pull some spark plugs and might put my new Thermalators on today, so is there anything specific I should look for while I taking things apart today? Thanks!
That chart is not for the Jeep due to fuel pressure(from my understanding) I was running the 62N2o and 26fuel..which is supposed to be the 150shot..Most Jeeps are making a true 125HP to the wheels with the 62N2o jet...I ran the 62N2o and 26fuel and my A/F was 11.5 range.with low bottle pressre..I think the 67N2o jet is more than a 150shot...My opinion only Now for your issues I would think maybe a fouled plug from when you was running so rich with the previous jets...I am not a N20 genius just an avid do it yourselfer..Thanks Link to jet calculator http://www.dynotunenitrous.com/store/Scripts/Jet_calculator/nitrousjetcalc.asp
Here is a pic of the plugs from the back cylinder passenger side. It almost looks like tar all around the electrode. I figure this can not be good. The plugs I can see thru the open valves since the intake is off just have white residue all over the electrodes. If there is was good news. My GSM Spacers had not leaked a single drop. They looked great and my intake was very clean hardly any oil residue at all. So the catch can is working also. How much deeper should I did? I'll order replacement plugs today, probably time anyway. I'm running the B&G NOS tune and I pulled 3# of timing in each range becasue of the amount of knock I get with the headers. Thanks for the link as I was just going by what Zex had posted and it did not mention difference in fuel pressure.
If all your plugs arent in one piece then Id say you didnt suffer any damage. I wonder if you exceeded the flow rate of your nozzle or plate? Doesnt look lean, more fat than anything.
Id run a higher octane as well, I try to get as close to 100 octane as I can. Usually 2 gallons or less in the tank of 93 and add 3 or 4 gallons of 100. Not much different than what you are doing, but detonation is not so forgiving
OK. All plugs are out and all but the ones above look fine. What happens that "fouls" a plug? The two in the pic really look as if they have tar or burnt oil sluge on them. Could that mean oil got passed the piston rings into the chamber? Do I need to pull that head off to check that piston? Just want some advice before I dig any further into the engine. Should I just put new plugs in a keep an eye on those back two to see if it happens again under "normal" driving conditions? Thanks again!
Here is a link to plugs http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html The pic does not show me enough to tell but I am guessing from your earlier jets the plugs may be getting fouled (just a guess) ...The link really has some good pics to reference your plugs...Thanks for the heads up...Keep us posted
Damn Jimmy, be careful with such a big shot. Thats about a 180 shot. I would check your AF again running that much spray. It kind of sounds like you pulled so much timing out of it that its not burning the excess fuel. Talk to Dave and get his opinion. I would slap some new plugs in there and drive it around to make sure there are no more misfires. I would hate to see a cracked piston but since your plugs are not damaged or flattened on the tips I think you are ok. Just be careful man. I would run pure 100 octane unleaded if I was gonna spray that big.
Hey Chris, Yeah, I had no intention on running that big a shot. Novice playing with fire and got burned. I was just going by the Zex charts but did not know you had to factor in fuel pressure, so stupid move on my part. I did not want to go any higher than 150, but so much for that plan. I am worred about the piston rings or valve seals in that one cylinder because it does look like burnt oil on those plugs. New plugs should be here tomorrow, so we'll see. Gotta put everything back together now.
Well on a brighter side, what did that beast run? I can only imagine a heads/cam/headers jeep on a 180 shot:censored:
Wish I knew...this was a street drap event on pit road at NSS, so there is a starting tree but no timing lights, so all I know is a beat a mustang with a lightning engine where the blower was so big the hood was cut open on one of my practice runs. Just afer the finish line he passed me like I had dropped anchor but it was after the finish line... Gong to try to find a scope to borrow...
I ran the 150 but I only had about 850psi of bottle pressure...Now running 125shot with 950psi bottle pressure...A big difference even without bottle pressure from the 125 to the 150...
Looks like I might have survived the scare. I got everything put back together, now with the Thermalators in place of the GSM insulators. New NGK's gapped at .040 and put about 50 miles on with a good portion being hard driving with lots of WOT. Checked the plugs in the cylinder where they were fouled and they are clean as a whistle. I'll keep pushing and check closely but let's hope they stay clean.
Hmm that might have been your problem right there. Is that what they were gapped at before too? You need to run them a little tighter at about .035 for nitrous to prevent spark blowout and fouling.
