titan 4.6L PINGING

[tl1r]

i quess i should have added that my distrib at this point is only backed off like an eighth of an inch I had it further b4 but i moved it back this weekend. If its lined up on the stock line i painted on it does what i described b4 it'll idle but anything more and it runs like ****. I cleared the pcm this weekend after i got the nitro box and put the dist as close to stock as i possibly could. My hopes are since I bought a brand new pcm that maybe it had to learn itself in stock settings and then i can mess with it a little after say a tanks worth of driving. Just at that point where i'm trying it all! With the distrib where i have it i'm sitting at 12-14 degrees at idle roughly 850 rpm. Got my compression #'s tonight 185 #1/ 195 # 2,3,&6/ 190 #4&5. I'll talk to them tommorow and hopefully they'll have me some other anwser b4 the holiday weekend.

 

[JJacobs]

Again.. rotating the distributor does NOT change the ignition timing on that engine.

 

[MudDawg]

Crash made an excellent point about the camshaft. If the selection is poor, the effective CR can be thru the roof under part throttle load conditions. This is as opposed to theoretical compression numbers based on swept volume,quench height and combustion chamber volume.

 

[tl1r]

is it possible to change the timing by moving the cps?? Its been my past experience that they work in one position or don't work at all. I would love a definite anwser on that. Yes i'm sorry i referenced it as timing on the distrib. You are very correct about the fuel sync and I didn't actually realize it until you said it a couple of posts ago I will try to stop using the wrong term.

 

[Dr. Dyno]

Not quite true, I live at 3,000 ft, and travel often to higher elevations. I run my 9.4 to 1 stroker on 87 octane and it runs like a champ. If I'm headed lower, I can run mid-grade or premium.

Also, don't forget cam selection can have a rather large effect on dynamic compression......

The reason you can run the engine on 87 octane at higher elevations is because the air density and the cylinder pressure is lower. You couldn't do that at sea level without the engine detonating unless you have a knock sensor to retard the timing.
Agree that cam selection can have a large effect on dynamic compression, which is why you must match the intake duration of the cam with the static compression ratio to avoid excessive cylinder pressures at low revs where detonation is most likely.

 

[Dr. Dyno]

Got my compression #'s tonight 185 #1/ 195 # 2,3,&6/ 190 #4&5.

Those are excellent compression numbers.
Which injectors are you running? They should be 24lb/hr injectors minimum.
You also said you have the plugs gapped at the stock 0.035" level. I find that my stroker runs better with the gap increased to 0.050" so you could do the same.

 

[tl1r]

running ford 24lbs injectors, bought them off a company called hyperjective. Great price 150 w/ shipping for all 6 and the guy guarnteed there flow rate better than anything you'll buy new off the shelf. i am running the .035 gap but i'll try spacing it out to .050 I have the same champion plugs that you do. For everybody waiting to do the i told u so dance:moon: I got a tank of 93 yesterday, alittle over 16 gallons and pinging was much much betterparty1: . Not gone yet maybe one more tank would get rid of it all? Titan did not have anything for me yet but they wanted me to try a injector swap to make sure I got the right ones. I'm pretty sure I have the right ones the guy i bought them from rebuilds them and the new bodies dont have #'s on them and I think the next tank of 91-93 will prove me one way or the other. I plan on putting about 10k a year on this between mainly street and a few offroad sessions a year. I figure I may get the heat shield for the bottom of the intake and I may see what portion of a tune-able controller i can get them to pay for to at least run 89. I plan on driving this from PA to AZ at the end of the month (moving) and I want to make sure I've got everything as right as it can be. I can't wait to see what it does to me at air temps of better than 100 dgrees w no humidity. Goes like hell, no neck snapping off the line but acceleration from whatever speed your at to wherever you want to be is awesome! doing 80 in 4th w/o breaking a sweat kept running out of room to see what my top speed is. Noticed alot of valve train noise in the higher rpms a little over 500 miles on the motor at this point from reading other stuff on the site it sounds like that will improve with time. I'm not ready to give up on the lower octane yet so i'll keep you informed. Still waiting on a definite reply on that cps question though. Who reccomends what as far as tuneable performance mods go if I wind up going that route?

 

[tl1r]

Still PINGING AHHHH!! Okay well got the second tank of 93 yesterday and the pinging has improved. Once in a while its no different then from before, sometimes the pinging just comes in at a later rpm. Its always the worst in 4th or 5th as early as 2,000 rpm but will kick in by 3,000 for sure if its going to ping. Other times I can drive it like I stole it and no problem. Starting to think about the adjustable map, the only inconsistent variable I have is the weather conditions. If anyone has a train of thought let me know I can go into a lot more detail if needed. New question that I've lowered my engine temp physicaly as well as how the pcm sees it through the IAT it will riching up the fuel mixture isn't it also advance my timing trying to warm the engine? Is this hurting me more than helping me???

 

[Gojeep]

Best to set your mixtures just right. Cant remember if it was already said but I would fit a Apexi2.See here for more info on fitting a APEXI2 to a XJ.
http://www.naxja.org/forum/showthrea...t=46515&page=2

 

[Dr. Dyno]

The Apexi SAFC 2 would definitely correct the A/F ratios across the whole rev range and under all load conditions but you'll need to buy a wideband O2 sensor to dial in the fuel curves. As you can imagine, it ain't gonna be cheap but the results are excellent. You'll need to aim for ~13.0:1 air/fuel under heavy load and ~14.7:1 under light load.
I still think your engine's running lean so it's almost certain that you'll need to richen it up at some (if not all) rpm points. I managed to do that with a MAP adjuster but since that only affects heavy load operation and affects all rpm points to the same extent, it might not necessarily be the right solution for you. It's worth a try though if for no other reason that it'll cost you only ~$10 to make one. Start at a 5.2v input voltage and increase in 0.2v steps until the ping is gone, then back off in 0.05v steps until you're just above the threshold for pinging. Good luck.

 

[tl1r]

well as advised i'm going to start with the make my own map sensor. Just waiting for radio shack to deliver the one part they had to special order. Total was about $15 now some of the parts cost a touch more and the delivery charge is 2.50 on the special order. Not complaining just letting any1 else know how maybe ready to do the same.

 

[tl1r]

Well i built the adjustable map a week ago and found it runs good at 5.65 volts. As far as i can tell the pinging is completely gone, once I get my hard top painted i'll be able to hear the engine better w/o all the wind noise. My moving date has gotten a little backed up b/c of my little project so won't be driving to AZ for another month. I feel being that I have all the tools available to me now scanners, parts discounts, dyno, every tool know to man that i should just go for the apexi and set it up 100% correct. I'm interested in a real world figure from someone who has hooked up the apexii, o2, fuel/air guage you know which ever way you went about it where you found the parts at the best price and most importantly how long did it take you to tune it in correctly?? Also I want to thank everybody here for lending the help that you did it made a huge difference and I really appreciate it !!

 

[farna]

tl1r, I'm one of the first dozen or so people to build a stroker, built mine back in 98 BEFORE there was a "strokers" group (http://autos.groups.yahoo.com/group/strokers/ -- you may want to drop over there!).

I'm just going to go over a couple things that have mostly been mentioned.

1. Indexing the distributor is the same for all 4.0L engines. All it does is adjust the position of the cam position sensor and tip of the rotor to the cap towers. The rotor has a wide tip so when the computer tells the ignition to fire the tip will be in conatact with the proper tower. Move it to far off and you "lose fire" to early or have a short fire because the tip wasn't in position yet. Has nothing to do with timing. The only reason you have to index the distributor is because aftermarket cams (and even some factory replacements) don't have the drive gear in the exact same place on every cam. Same for the distro drive gear. The position of the gears can be off from the factory installed parts, so the distributor needs repositioning.

2. Sounds like you have a CPS relocating kit. You CAN change the timing by moving the CPS. Even if you have one in the stock location you can move it a little. Just pull the CPS then slot the holes. Moving it about 1/8" clockwise or coutner clockwise will change the timing a few degrees. If you need more than that you need some more engine work.

3. The Renix system is a bit more tolerant of compression changes, but will still ping on 87 if stock components are used to build a stroker. That's how I built mine -- stock 4.0L pistons, 258 crank and rods, NAPA "Econo-Power" 258 cam. It would ping under load with 87, only under heavy load with 89. I later machined the dish in the piston deeper to bring compression down to 9:1, and it doesn't ping on 87. I'm not sure if an HO engine would or not, but the knock sensor doesn't have the range to tune out ping at 9.5:1.

4. You can use a cam with a lot of overlap to bleed pressure. If building a "budget stroker" that's the easy way to do it. You "lose" 10 hp (+/- 2-3), but that extra 10 ponies will cost you $600 or so in custom pistons. You will still get a 50 hp increase even with the high overlap cam, and the only cost over a stock rebuild is for a used 258 crank and rods. I don't count machine work to those, you'd need the work on an old 4.0L crank and rods too.

5. To get the highest power you need to worry about quench and maybe use the 4.0L rods, but that will cost $2000 or so more than a build with stock components. You'll only get 15 or so extra ponies (5 more than custom pistons) for the extra dough. For a budget 250 hp engine, worry more about compression and forget quench height. Only when running over 9:1 compression does quench make any difference in the 4.0L.

6. The HO computer system is a little harder to fool. This is mainly due to the timing program modifications required to eliminate the knock sensor and EGR valve.

7. Looks like you hit on the main thing used to fine tune the engine -- the adjustable MAP sensor! Yes, it's only needed to correct tuning. But the tuning requirements changes when the engine was modified and the computer kept stock. The only other thing to do is use an aftermarket programmable computer such as the MegaSquirt or SDS (www.sdsefi.com).

Glad to see you have it under control! There's a bit of a learning curve to building strokers, as you found out! The strokers group will help as well as this link: http://www.jeep4.0performance.4mg.com/stroker.html.