I just installed a 4.6l stroker in my brothers jeep. All of the info I see out there says the computer will adjust. I knew better than that it is a speed density program it doesn't know it is 16% larger engine. Needless to say the engine pings and is needing 20% more fuel according to the fuel adaptation on the scan tool. I have larger injectors ordered. I would like to know does anybody know of any companies that would program a computer for this specific motor.
there's a company in northern illinois near rockford called "Irish's Offroad" that claims to do all needed work to upgrade to the 4.6L. I know nothing about them or even if they're legit (craigslist) but the ad looks like they know what they're talking about. their #
815 355 1652
let me know if they are legit; i was tempted....
I have not been able to find anything concrete on stock injector size, But what I have found they came stock with 24# injectors. If you multiply 24 * 1.20 (add 20% to the injector size) you come up with 28.8. If You use the formula (expected hp * .5) / (# of cylinders *.8) I came up with correct me if you think i am wrong (260 * .5) / (6 * .8) = (130) / (4.8) = 27.0833. So what it comes down to is I ordered 28 # injectors. The octane of fuel I am running 91 is the best we can get here with out going to $7.00 gallon race fuel. I am open to any suggestion even if they are way out in left field. Maybe i missed something.
with the kit you bought, was there mention of the compression ratio?
newer naturally aspirated 5.0/4.6 cobras came with 24# injectors. they are light blue and a very common upgrade for h/c/i 5.0 cars, so i'm sure you can find a set for cheap. 30# are red or green and are also pretty common.
Just got off the phone with the guy from Irish Offroad. He tells me he doesn't think the computer needs to be flashed. He gave me some info on timing that I was unaware of. I am going to restab the distributor and I will post more after I do that. If anybody can give me definite on what # injector was in a stock in a 98 4.0l wrangler engine i would greatly appreciate it.
I rather doubt bigger injectors will do anything - except maybe at WOT and high R's.
The computer will just shorten the open time on a bigger injector, cutting back the fuel to maintain the correct air to fuel ratio. Picture a coke bottle - it can only hold so much water no matter how big the filler hose is.
The way it works - the O2 sensor senses the Oxygen content in the exhaust, the computer "reads" it, determines if it's too rich or too lean, then adjusts injector open time to get the correct A/F ratio. The correct A/F ratio has nothing to do with displacement. All engines, from the tiniest to the biggest are most efficient when the air to fuel ratio is correct.
In the old days (carbs) we used to richen it super rich to stop the pinging - we weren't addressing the real problem, but it stopped the ping. We were simply flooding it with the cooling effect of lots of fuel. Water worked too.
I really doubt it's a lack of fuel.
Timing is controlled by the computer, it is pre-determined the correct timing - again, timing has nothing to do with displacement. Notice the timing curve for a 454 is about the same curve as a 4.0.
But - the plugs you used - are they the stock ones? If you are using so called "trick" plugs try stock plugs. No splits, duals, triples, rings, yellows, blues, red etc. Plain old cheapie stock ones the factory used - I prefer Champs, but others will work well too - except Bosch! (They use "one size fits all" - ask your wife how "one size fits all" fits her.)
When you stroked it, did you also shave the head or modify the combustion chamber - like change the shape of it? If you took that step, then surely you CC'd it too.
What I'm thinking is hot spots in the combustion chamber causing the pre-ignition (likely the plugs). If you relieved the combustion chamber by grinding, the plug shell may be hanging down too far - glowing.
Using non-standard "trick" plugs is another problem. Just because it "fits the hole" doesn't mean it dissipates the right amount of heat throughout the entire RPM range.
And - another thought - there are several head gasket configurations for 4.0's around - many will plug off the water jackets in such a way the head runs too hot, or makes hot spots. I found out the hard way fitting an 00 head to a 90 4.0.
It's no wonder the country is falling apart - stupidity abounds!
This motor is not a kit. It was built by the machinist here in my home town. Who is responsible for a good portion of the hot rod motors you see in the boats on the southern colorado river and at the sand dunes just over the border in california. The compression ratio is close to 10 to 1 I know that. I also know that the computer is adding 20% more fuel. I am not saying the toiming is the problem I am saying the problem is a combination between the amount of fuel and the amount of timing at any giving time. The computer maps this out so to speak. This engine does not have a stock cam. So the amount of vacuum it creates at any givin time compared to throttle position and RPM,s is different than a 4.0l. With this being said the computer does not know it does not have a 4.0l at the end of its wires so it is doing what it thinks the 4.0l needs. At any givin time is probably a little bit different than the high compression mild cam 4.6l.
I am with rrich and tailhole on this one. You need to find what your DCR is. I have seen people mention that any higher than 8.5 DCR, you will need race fuel. Also, it depends on where you live like altitude, air density etc.
Another thing that helps reduce pinging is good quench. 0.040 to 0.050 is very good. Do you happen to know yours?
If your DCR and quench are okay then what rrich recommended will apply to you.
98 TJ 4.7 Stroker!!! Unichip tuner, HPD30/D44, 4.56, Detroit Locker in rear axle, 3.25RC SL, 1.25BL, 1MML, 35x12.50x15, Cager Softs 15x8, XRC10 winch, Rancho 9000XL shocks with wireless remote
The computer doesn't care what the displacement is - all it wants is to keep the A/F ratio in line.
Notice there is not any input or programming for the computer to know what the displacement is.
The computer's ultimate and most influential sensor is the O2 sensor. It tells the ECM WHERE it is as far as A/F ratio. All the other sensors inputs, like TPS, MAP etc are only inputs to help the ECM "predict" the needed A/F ratio to prevent stumbling, sag etc. Remember the O2 reads it "after", - it reads the results. Without the other inputs it will sag.
You didn't answer about plugs you are using.
The new cam - your engine builder should know this - the intake manifold vacuum always pulsates (you don't see it on a regular vacuum gauge, the gauge is dampened and the pulses are very fast. You need a vacuum transducer to see it. In stock form that pulsation is fairly minor. The MAP sensor reads that vacuum and is designed to smooth or "average out" the pulsations to get what it needs. But it can only do so much.
When you change the cam you are treading on thin ice. You can increase valve lift a little without increasing those pulsations by much, but if you change duration or overlap by much, the pulsations radically increase. (Look at the "big" cammed (rumpity rump) race engines trying to idle with a carb - they drive the carb's circuits crazy - but they don't care about idle, only WOT.)
Those pulsations drive the MAP sensor nuts! Those pulsations may be cutting the fuel down to the point it's running lean and pinging. The MAP "averages" the readings, where a carb switches between circuits - idle, tranfer, main, then back to idle. The reactions between carbs and MAPs are different, yet still upsetting.
Try 4 things -
1. Try artificially enrichening the mixture with propane. Get a cheapie propane torch - remove the tiny restriction orifice - or drill it out - remove the torch tip and slip a long hose over the tube. Screw it on a small propane canister.
Tape or attach the end of the hose in the intake airstream, take the bottle with the valve in the cab with you.
Run it up to speed, make it ping - then holding the bottle valve down, add some propane. If it is running lean the R's will increase (it likes it) and the ping will stop.
If the mixture is correct, adding a small amount of propane (fuel) will not change the R's. Adding more will cause the R's to drop. That means the A/F ratio is already correct.
If adding the R's go way up, then it was too lean.
But - remember the ECM monitors the O2 - so whatever you do will only be temporary for 2 or 3 seconds, then the ECM compensates for your enrichment.
Way too rich should stop the ping - by the cooling effect of being too rich, but performance and mileage will suffer.
2. Remote mount the MAP Sensor (get creative) - use a very long and large hose for the vacuum - the long large hose will dampen the pulsations - or use some kind of canister - like a fuel filter to act as a dampener. See if that helps.
3. But still - the plugs - you should by now be able to see if they are creating "hot spots." Try stock plugs or even 1 or 2 clicks colder.
4. Use an infra-red thermometer from underneath - see if one exhaust temp is way hotter than the rest, indicating cooling troubles - head gasket etc. Try it right after you run it at 2500 for at least 2 minutes.
Larger injectors - there were enterprising 2 guys that took their truck to the market to buy watermelons. They paid $.50 a pound for them.
They found a street corner and set up to sell them. They sold them all for $.50 a pound, they sold them all by noon.
One said to the other - why didn't we make a profit, we sold them all?
The other said "because we ran out of them too fast, we need a bigger truck!"
Let us know.
It's no wonder the country is falling apart - stupidity abounds!