Need Factory Ignition Table

Turbo4.0

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Dec 1, 2023
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Johns Island, SC
Morning Gents,

I've been in search of finding factory ignition timing table for the Jeep 4.0 motor. It's something I haven't been able to come across thus far on line anywhere. I've got the '98 straight 6, Got her turbo'd and had to build a completely new fuel and ignition map from scratch. I've seen some signs of detonation issues and even lost a head gasket from it already which is much better than a ring land.

I'm kinda shooting in the dark here not knowing what the factory maps run for ignition timing. So for the time being we went mad retard on everything to save further damage. Any input in this or if you know a buddy that has the info or a link to an ignition timing table it'd be much appreciated. Likewise if anyone else is turbo'ing their Jeep I'm here for ya.
 
I presume you are using an aftermarket engine management system? I found stock 2005 and 2006 4.0L files in the HPTuners respository but can't look at them till I get home on my tuning laptop. I can take a screen shot or export later.
 
I presume you are using an aftermarket engine management system? I found stock 2005 and 2006 4.0L files in the HPTuners respository but can't look at them till I get home on my tuning laptop. I can take a screen shot or export later.

Correct. I'm running a MegaSquirt MS3X to run the entire system. I'm also using a Viper Coil ignition system instead of the factory distributor that came on '98s so the map from a '05-'06 would probably be extremely accurate as long as its a 4.0liter.

Is it a Modded HP Tuners map or is it the stock map?
 
The description of both state 'stock tune'. I will download both and compare when I get home this evening.
 
So the Jeep tune looks to use a part throttle and WOT base table with a lot of correction tables. The part throttle is same as WOT except for the 1200-3000rpm at 20&25KPA cells (circled in red) which are reduced to 20. I presume this is for engine braking or lean cruise on decel as that is the only time those cells will be hit.

05_40L_WOT_BaseTiming.png


The 2005 and 2006 are a bit different in the high load cells. The 2006 has a little less timing there with a hole in the 1-2K rpm cells (blue shaded cells).

06_40L_WOT_BaseTiming.png
 
The 101 row in HP would be the same as the 100 row in your MS. The tables are reversed. Top to bottom and bottom to top. Not uncommon in the tuning world. Ultimately your timing is going to depend on your setup. The stock is a place to start, but with a turbo it needs to be tuned.
 
The 101 row in HP would be the same as the 100 row in your MS. The tables are reversed. Top to bottom and bottom to top. Not uncommon in the tuning world. Ultimately your timing is going to depend on your setup. The stock is a place to start, but with a turbo it needs to be tuned.

Your right. I don’t need boost tables though. Just NA columns to begin with. It’s hard building your entirely new own base map when you have no idea what stock is. His maps help me get a starting point I can enter in non boost columns- and then apply the practices we already use on our 900 whp turbo setups to begin with and get it on a dyno to get things tweaked.

We’ve got a few Hondas in the deep 9’s in the 1/4 now knocking on the door of 8’s. First time toying with a Jeep though as a beach buggy- and not knowing what stock maps are as we’ve been building this one.
 
What kind of timing were you running when you knocked the head gasket out?
 
Looks like the Hp map is closer to 40° in that area. Are you sure it was timing that killed the gasket, or something else?

what we typically find is too much advance in the peak torque range is what leads to gasket or internal engine issues. We can run more advanced timing at higher rpm, and more advance at cruise, it's the torque rush that hurts the motor typically where the cylinder pressures are the highest. Again- having no idea where a stock jeep 4-0 ignition map is to begin with- we were shooting in the dark on it. A safe rule of thumb on 93' oct is to take roughly a degree per pound of timing out. Some of that depends on cast iron vs aluminum, spark plug heat range etc.. but it's a good starting point.

spackle on the plugs indicate detonation. Just again- having no idea what's stock is a tough start to build a map. Even some of the HP timing points seem like they're not totally stock. There's some holes in it that need interpolated. But it's a good start.

Fuel is on point around 11.8-12.2 AFR's and no boost spikes. Other than Ign- since we have fresh 93 oct it'd likely only be timing.
 
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You most likely have too much timing in boost. Your 134 kpa row has about 5 more degrees than mine does, not that we can really compare two different setups. I would find it difficult to believe that you could blow a head gasket in vacuum with a 4.0 and 93 regardless of timing values.
 
I would find it difficult to believe that you could blow a head gasket in vacuum with a 4.0 and 93 regardless of timing values.

Twenty year old engines and without knowing the complete history of previous ownership anything is possible.

I did a head gasket on a 4.0 2004 XJ a couple months ago. Fan tail of coolant out the back of the engine.

Looked the someone had been in there before... maybe used the bolts one too many times... probably and possibly didn't torque things down right or didn't use an accurate wrench.

New bolts, new head gasket...copper spray cause I can... cleaned the crap out of every..."checked" for flatness with a good straight edge...works great now.

-Mac
 
You most likely have too much timing in boost. Your 134 kpa row has about 5 more degrees than mine does, not that we can really compare two different setups. I would find it difficult to believe that you could blow a head gasket in vacuum with a 4.0 and 93 regardless of timing values.

I would agree with you. I never said timing in vacuum was the issue. I'm not sure how you tuned your setup or if you had someone else tune it. But in this case- the boost columns were what was in question. Never the vacuum columns. But remember- there's a relationship between where timing is in vacuum and when you enter into boost. Hence- That's why it's always valuable to know what stock non boost values are- because you then have a starting point for boost calculations.

Id like to see your ignition map and what your doing.
 
I would agree with you. I never said timing in vacuum was the issue. I'm not sure how you tuned your setup or if you had someone else tune it. But in this case- the boost columns were what was in question. Never the vacuum columns. But remember- there's a relationship between where timing is in vacuum and when you enter into boost. Hence- That's why it's always valuable to know what stock non boost values are- because you then have a starting point for boost calculations.

Id like to see your ignition map and what your doing.

I'm sorry, I thought somewhere I read that the problem was in vacuum. I guess maybe I inferred that as you were asking about stock maps. I tune my own stuff. I'm running AEM Infinty. My setup may be a bit different as I have a 4.7 stroker with an Edelbrock head. I'm also running 93, but with methanol injection. So, it may be apples and oranges. Does the MS have knock control? This is one of the base maps, however I am using flex fuel, boost and lambda to control spark timing as well, so these numbers get modified a bit more.

Timing Map AEM Infinty.JPG
 
I'm sorry, I thought somewhere I read that the problem was in vacuum. I guess maybe I inferred that as you were asking about stock maps. I tune my own stuff. I'm running AEM Infinty. My setup may be a bit different as I have a 4.7 stroker with an Edelbrock head. I'm also running 93, but with methanol injection. So, it may be apples and oranges. Does the MS have knock control? This is one of the base maps, however I am using flex fuel, boost and lambda to control spark timing as well, so these numbers get modified a bit more.

View attachment 479191

Some of your Timing your running hotter than I am even. Probably some of that liberty is from the A:W cooler and Meth. Definitely going to help you a lot. What's your Target AFR's?


How the final power numbers you're seeing with the boost you're running? I've been toying with doing a stroker in the future, just dont know if it's needed when I can turn up the psi so would def like to hear from someone who's done both