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  #1  
Old August 28th, 2015, 09:14
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Spark and fuel maps

Anyone have a good fuel and spark map for a 4.0?
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Old August 31st, 2015, 22:14
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Re: Spark and fuel maps

Wow, that many?
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Old September 8th, 2015, 12:47
hexdmy hexdmy is offline
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Re: Spark and fuel maps

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Originally Posted by DieselSJ View Post
Anyone have a good fuel and spark map for a 4.0?
I think anyone who would be capable of answering a question along those lines would be hesitant about answering it seeing as you have put zero effort/thought into asking the question.
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Old September 9th, 2015, 00:17
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Re: Spark and fuel maps

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Originally Posted by hexdmy View Post
I think anyone who would be capable of answering a question along those lines would be hesitant about answering it seeing as you have put zero effort/thought into asking the question.
And exactly how much effort/thought have I put into it? Now go away child and let the adults talk.
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Old September 9th, 2015, 09:31
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Re: Spark and fuel maps

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Originally Posted by DieselSJ View Post
Anyone have a good fuel and spark map for a 4.0?
Yes
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Quote:
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99 4.0/AW4/231 8.25/D30 ARB's 4.56's 33's deavers and a few other things.

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Old September 9th, 2015, 17:39
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Re: Spark and fuel maps

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Originally Posted by sidewaysstarion View Post
Yes
What do you like for AFR at full load? And what do you like for timing? Assuming 4.0 with 214 degree cam (at 050) and 9:1 with head work? The cam mfg wasn't much help. There are plenty of maps out there for SBF/SBC, but haven't found anyone willing to share any 4.0 maps. Right now I'm at about 13.0:1 AFR at full load, with about 32 degrees total timing, all in by about 2800 rpm. Any more timing even at higher RPM and she doesn't pull as hard. I know every engine will be different, so I'm just looking for general numbers - what do you like for AFR, total timing and in by what RPM, etc. I guess I just want to see if I'm in the ballpark on stuff or if I'm way off on AFR and timing.
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Old September 10th, 2015, 13:59
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Spark and fuel maps

12.5-13.0:1 is a good target afr range @WOT for n/a engines. I don't know what timing to shoot for, but once you have the right amount of fuel there, add timing until it pings, then back it off(if you have a way to adjust it--most piggy-backs can just retard timing). Have you read the thread of slotting the ckp to add or subtract a few degrees of base timing?
P.S. hexdmy: You are the expert, and someone that is on my short list to potentially tune the pcm for my stroker. . . why the above comment? I didn't mind you flexing your muscles on the other proclaimer(who's also on the list).

Last edited by gradon; September 10th, 2015 at 14:16.
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Old September 10th, 2015, 15:13
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Re: Spark and fuel maps

Thanks. If I go richer than that, it doesn't gain anything. If anything, it slows it down and the plugs come out all sooty when I read them. I do have full control over timing and AFR so I can advance or retard and rich or lean wherever I need to on the map.

This would be so much easier if I had access to a dyno, which I don't.
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Old September 10th, 2015, 18:40
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Re: Spark and fuel maps

Are you running a standalone? Typically, you won't see any gains messing around with fuel. Shoot for consistency and then tune timing.
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Old September 11th, 2015, 12:23
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Re: Spark and fuel maps

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Originally Posted by Boostwerks.com View Post
Are you running a standalone? Typically, you won't see any gains messing around with fuel. Shoot for consistency and then tune timing.
FAST ECU. I've got the VE table dialed to where my 02 correction is basically a flat line. Without a dyno it is very hard to know if I'm bringing timing in too fast or too slow, and what it would truly like for total timing. And not having any published tables to compare to makes this all a shot in the dark.
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Old September 12th, 2015, 15:31
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Re: Spark and fuel maps

Quote:
Originally Posted by DieselSJ View Post
FAST ECU. I've got the VE table dialed to where my 02 correction is basically a flat line. Without a dyno it is very hard to know if I'm bringing timing in too fast or too slow, and what it would truly like for total timing. And not having any published tables to compare to makes this all a shot in the dark.
Depending on your fuel and how much compression you're running I've found the 4.0 to reach peak torque well before you hit the peak knock limit on timing. Did you degree your cam in at all? what are the specs on the cam? We know you have 214* of running duration at 0.50, but what is the LSA of the cam? Lift? etc? We need more info!
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Quote:
Originally Posted by cracker
I seem to have run out of self tapping washers
99 4.0/AW4/231 8.25/D30 ARB's 4.56's 33's deavers and a few other things.

Click here to join the red team
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  #12  
Old September 12th, 2015, 17:27
hexdmy hexdmy is offline
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Re: Spark and fuel maps

Quote:
Originally Posted by gradon View Post
12.5-13.0:1 is a good target afr range @WOT for n/a engines. I don't know what timing to shoot for, but once you have the right amount of fuel there, add timing until it pings, then back it off(if you have a way to adjust it--most piggy-backs can just retard timing). Have you read the thread of slotting the ckp to add or subtract a few degrees of base timing?
P.S. hexdmy: You are the expert, and someone that is on my short list to potentially tune the pcm for my stroker. . . why the above comment? I didn't mind you flexing your muscles on the other proclaimer(who's also on the list).
I believe that when people ask questions, especially ones that requires some thought, that they should put in at least as much effort as those who my be offering some help or advice. Half of this thread has been spent trying to get all the details out of this guy. If he had just put some effort into his initial post, it would have helped everyone out, including himself. Something like this:

Hello, I'm looking for some tuning advice. I have a 4.0 Jeep with a FAST engine management system. The specs of the motor are :

camshaft: 214 degrees of duration @ .050, I don't have any other specs on the cam.

32 degrees of timing total advance from 2800 rpm up, I found that the power drops off above 32 degrees

air fuel ratio is 13:1, if I tune it any richer I find that the plugs foul out

I'm just looking to see if anyone would share their tuning experience with a similar setup to what I'm running. I do understand that it would be best if I tuned this on a dyno, but unfortunately I don't have access to one.



Your plugs should not be fouling out if you run a little richer than 13:1 at full load. The stock Jeep was tuned to run as rich as 11:1 (.75 lambda) in order to protect the catalytic converter. I have found that there is almost immeasurable differences in power between 12.8 - 13.2 afr (.87 - .90) lambda on these motors, however I tend to stay towards the rich side, and it depends on the build, if it's a race engine running one pump 91, for example, I would run it even richer, just depends on the setup.

These motors will knock, if you are running that much timing, and assuming you are nowhere near sea level, I say that timing curve, from my experience, is too aggressive. Along the lines of what sidewaystarion said, verify the cam timing by putting a degree wheel on the engine, and checking the cam manufacture to see what the ICL should be. You should also do a cranking compression test if you have not already. Seems like a lot of Jeep people have been trouble with the cam timing. If the cylinder pressure is low / cam timing is off, the Jeep will run poorly.

STOCK 1999 XJ WOT TIMING 500 FEET ABOVE SEA LEVEL (APROX)
512 3.3
704 3.3
800 4.3
896 4.3
992 5.5
1120 8.8
1248 9.3
1504 14.8
1760 16.3
1984 17.3
2240 21.0
2496 22.0
3008 22.3
3488 20.5
4000 18.3
4480 18.3
4992 25.0
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Old September 14th, 2015, 09:56
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Re: Spark and fuel maps

Quote:
Originally Posted by sidewaysstarion View Post
Depending on your fuel and how much compression you're running I've found the 4.0 to reach peak torque well before you hit the peak knock limit on timing. Did you degree your cam in at all? what are the specs on the cam? We know you have 214* of running duration at 0.50, but what is the LSA of the cam? Lift? etc? We need more info!
Well, I can't really share more about the cam specs. This was a custom grind that we worked on with Clay Smith. It has been degreed - they machined a cam sprocket that allows us to install offset bushings so we can make adjustments from -6 to +6 in 1 degree increments. LSA is 109. Lift is more than .490. That is about as specific as I can get. CR is right around 9.2. Being as we are running in a limited class, we tend not to share specifics.
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  #14  
Old September 14th, 2015, 10:03
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Re: Spark and fuel maps

Quote:
Originally Posted by hexdmy View Post
I believe that when people ask questions, especially ones that requires some thought, that they should put in at least as much effort as those who my be offering some help or advice. Half of this thread has been spent trying to get all the details out of this guy. If he had just put some effort into his initial post, it would have helped everyone out, including himself. Something like this:

Hello, I'm looking for some tuning advice. I have a 4.0 Jeep with a FAST engine management system. The specs of the motor are :

camshaft: 214 degrees of duration @ .050, I don't have any other specs on the cam.

32 degrees of timing total advance from 2800 rpm up, I found that the power drops off above 32 degrees

air fuel ratio is 13:1, if I tune it any richer I find that the plugs foul out

I'm just looking to see if anyone would share their tuning experience with a similar setup to what I'm running. I do understand that it would be best if I tuned this on a dyno, but unfortunately I don't have access to one.



Your plugs should not be fouling out if you run a little richer than 13:1 at full load. The stock Jeep was tuned to run as rich as 11:1 (.75 lambda) in order to protect the catalytic converter. I have found that there is almost immeasurable differences in power between 12.8 - 13.2 afr (.87 - .90) lambda on these motors, however I tend to stay towards the rich side, and it depends on the build, if it's a race engine running one pump 91, for example, I would run it even richer, just depends on the setup.

These motors will knock, if you are running that much timing, and assuming you are nowhere near sea level, I say that timing curve, from my experience, is too aggressive. Along the lines of what sidewaystarion said, verify the cam timing by putting a degree wheel on the engine, and checking the cam manufacture to see what the ICL should be. You should also do a cranking compression test if you have not already. Seems like a lot of Jeep people have been trouble with the cam timing. If the cylinder pressure is low / cam timing is off, the Jeep will run poorly.

STOCK 1999 XJ WOT TIMING 500 FEET ABOVE SEA LEVEL (APROX)
512 3.3
704 3.3
800 4.3
896 4.3
992 5.5
1120 8.8
1248 9.3
1504 14.8
1760 16.3
1984 17.3
2240 21.0
2496 22.0
3008 22.3
3488 20.5
4000 18.3
4480 18.3
4992 25.0
Great info...thanks!

Wow, that timing curve seems incredibly conservative. This makes me wonder if I'm on the back side of where it needs to be. Most of our races are 2000-3000 above sea level. We do have 2 races in Parker where it is 500 feet.

Plugs don't foul per se - we don't ever get any misfires - but the definitely come out reading very rich. We are running a MSD6 with a Blaster series coil. Plugs are Champion, stock heat range.

Well, seeing as how I am potentially pretty far off, I think we need to find a dyno and schedule some time.
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