Crash course for a base map - '98 Grand Cherokee 4.0 Turbo

[Mr4btTahoe]

Hey alls...

Completely new to HP Tuners... have done some work with SCT 10+ years ago so that info is long gone.

I'm trying to get my ducks in a row to get a base tune on my '98 Grand Cherokee. Its a 4.0/auto that is now turbocharged. I'm currently babying it around and staying out of boost until I can get something going on it.

A friend of mine is loaning me his MPVI2 for a few weeks to see what I can do. I don't have it in my possession yet.. it'll be a week or so.

Another friend is hooking me up with a 2 bar MAP sensor and 36lb injectors.

My first goal is to get it running with the 2 bar MAP and get it to take boost without freaking out and dumping fuel.

From doing some reading, It looks like I need to change the "MAP Scale Multi" from 244 to 122 to take full advantage of the 2 bar sensor. I don't plan on running anywhere near 14psi.. likely only 6-8psi.. so I may not need to take it down that far.

Now I've located the main fuel and spark maps.. and have read that I need to re-scale them for the new multiplier. Anyone want to give me a basic run down on how I would accomplish that?

I've also read that I'll need to "1" out the "Altitude Correction" table. That's simple enough.

2nd goal will be to get the bigger injectors swapped in as I doubt the stockers will be up to the task. Without any information other than the injectors I'm getting are from a stock supercharged 3800 (late 90s GTP).. how would I go about doing that?

Once I get the tables scaled, I think I can manage dialing it in as everything looks pretty basic from what I'm seeing. I downloaded the software and pulled up a member posted tune just to get a feel for where things are.

So... who feels like teaching the new guy?

I appreciate any help/pointers/direction you guys can offer. I'm hoping to dive in head first come middle of next week.

Thanks!
-Chris

[spoolboy]

There's not a lot of info on the JTEC yet as HPT tuning for these was released very recently. The Dodge world keeps info close to the vest. Folks that tuned JTECs up until now were using SCT and they also are not sharing info.

When you get your MPVI2, share a tune and log and maybe someone will be able to help.

[Mr4btTahoe]

Will do. After figuring that I may need more time than a couple weeks, I went on and ordered one.

It will be here friday. I'll pull the stock tune and post it up.

If anyone has any pointers before then, please post them up.

[Mr4btTahoe]

OK.. Here is the stock file.

Plan is to start out by shutting off the rear o2 since it's gone.

Then Adjust the MAP multi to 122-180 range. I wont be seeing anywhere near 14psi.. MAYBE 6.. so I want to scale it to get the most usable range out of the map.

My question is how to scale the base fuel and spark maps accordingly. I assume that it'll move key on kPa to the 50-80ish range (haven't checked with the scanner yet).

So would I just manually move the 105 line up to 80.. so on and so fourth? Then the 80-105 part of the map.. add a bit to get started for in boost fuel?

Or is there an automatic way to "scale" the map?

Thanks!

[Mr4btTahoe]

Stock.hpt

[Mr4btTahoe]

Messed around most of the evening and not getting anywhere.

Here is the current file and a warm idle/rev log.

Fuel trims are all over. Will not rev past 3k (acts like a rev limiter)

Keep in mind.. I am completely new and wanting to learn.

Please point in the right direction.

Current changes to this file are as follows

MapMulti set at 190 (using GM 2bar map - shows 2.75v KOEO)

-5 degrees from entire base timing map (just to be safe)

+7% fuel entire base map just to be safe.

It will sorta idle.. and free rev to 3k.

If anyone can point me in the right direction to help me start dialing this in.. I'd be grateful.
Map Scale 190+7 -5 timing.hpt

Idle Rev 7% 190 -5t.hpl

[spoolboy]

OK.. Here is the stock file.

Plan is to start out by shutting off the rear o2 since it's gone.

Then Adjust the MAP multi to 122-180 range. I wont be seeing anywhere near 14psi.. MAYBE 6.. so I want to scale it to get the most usable range out of the map.

My question is how to scale the base fuel and spark maps accordingly. I assume that it'll move key on kPa to the 50-80ish range (haven't checked with the scanner yet).

So would I just manually move the 105 line up to 80.. so on and so fourth? Then the 80-105 part of the map.. add a bit to get started for in boost fuel?

Or is there an automatic way to "scale" the map?

Thanks!

I'm taking a look. But ultimately you can't set your tables based on what you'd like for resolution. You have to set the table to match the scale of the map sensor.
Also, the numbers are just for you - the PCM doesn't care what they say and the fuel and spark tables can't go higher than 105kpa.

What are the 36 pound injectors exactly? Where did they come from as far as application? What pressure are they rated at?

[Mr4btTahoe]

They are stock injectors from a supercharged 3800.

The injectors have not been changed though.

Right now, I'm just trying to get it to idle/run properly with the 2 bar map. It just doesn't want to cooperate.

It also hits this 3krpm wall.

Right now, I've got the mapmulti set at 190 which puts WOT kPa @ ~65 on the fuel map. That gives me decent head room for boost. I've added fuel.. I've pulled fuel.. doesn't seem to matter. Fuel trims are all over.

I went as far as returning it to stock and logging a short drive with the stock map sensor... then going in and replicating those cells in the range of the 2 bar @ 190. Got it to idle better... but LTFT and STFT are still all over the place..

I'm going to take a break and revisit it this evening.

[spoolboy]

OK.. Here is the stock file.

Plan is to start out by shutting off the rear o2 since it's gone.

Then Adjust the MAP multi to 122-180 range. I wont be seeing anywhere near 14psi.. MAYBE 6.. so I want to scale it to get the most usable range out of the map.

My question is how to scale the base fuel and spark maps accordingly. I assume that it'll move key on kPa to the 50-80ish range (haven't checked with the scanner yet).

So would I just manually move the 105 line up to 80.. so on and so fourth? Then the 80-105 part of the map.. add a bit to get started for in boost fuel?

Or is there an automatic way to "scale" the map?

Thanks!

Are you running a manifold referenced fuel pressure regulator?

Also, you need to send a ticket in to HPT to have them give you table 34042 altitude compensation for this calibration.

[spoolboy]

Do these 4 things and tell me what the scanner logs as MAP kpa with KOEO:
Flash in stock tune with stock map sensor.
Flash in a stock tune with only map scale mult as 122 but leave the stock map sensor installed.
Change to the 2 bar map with mult at 122.
Flash back in the stock tune with the 2 bar sensor.

That should give us an idea of what's going on with that multiplier. Ultimately, you may not even need/want to change this parameter.

[Mr4btTahoe]

Do these 4 things and tell me what the scanner logs as MAP kpa with KOEO:
Flash in stock tune with stock map sensor.
Flash in a stock tune with only map scale mult as 122 but leave the stock map sensor installed.
Change to the 2 bar map with mult at 122.
Flash back in the stock tune with the 2 bar sensor.

That should give us an idea of what's going on with that multiplier. Ultimately, you may not even need/want to change this parameter.

Here we are..

2 bar 122.hpl

2 bar Stock.hpl

Stock Idle.hpl

Stock Map 122.hpl

With the 2 bar on stock tune or 122, neither wanted to idle at all. Pig rich. I got the stock tune to idle longer but had to pedal it a bit at first to keep it going.. then it was idling at 10.5 on the wideband.

Thoughts?

[Mr4btTahoe]

I will say that when I logged the stock tune and stock map, it hit nearly every cell on the fuel map.

With the 2 bar map and Multi at 190, it would idle at a similar kPa but would only reach 65kPa at WOT rev.

Also, no fuel pressure regulator. I wanted to do everything via tuning instead of piggy backs and fuel units.

The Cherokee is bone stock other than the turbo. It runs really well out of boost on the stock tune. Just wish I could get it to do the same while using the 2 bar so it wouldn't freak out at positive pressure.

[spoolboy]

Ok, try 488 with the 2 bar and log KOEO.

We'll still need to figure out the offset, but that should get us n the neighborhood.

[Mr4btTahoe]

Ok, try 488 with the 2 bar and log KOEO.

We'll still need to figure out the offset, but that should get us n the neighborhood.

Ok.. seems to be getting closer to the factory 1 bar sensor reading. The stock sensor/tune showed 14kPa KOEO. With the 2 bar sensor in and set to 488, I'm seeing 19kPa KOEO.

So.. why doesn't it read atmospheric pressure (or ~100 kPa) when KOEO? I would have thought that it would read the same as if the engine was at WOT. This was throwing me off the first night I messed with it because those numbers didn't make sense.

So if we set the multi to a point where it reads like the stock sensor... will it not go off map when in boost and freak out like the stock 1 bar sensor... Or.. Will it just move through the map slower (if that makes sense)?

Just trying to wrap my head around why each one is different.. one guy says he dropped his to 122 to make it happy with boost... one guy says 190.. another said he had to go to 260. What exactly is the multiplier doing?

I appreciate you taking the time to point me in the right direction.

Here is the log showing KOEO with it set to 488.
2 bar - 488.hpl

[spoolboy]

Ok.. seems to be getting closer to the factory 1 bar sensor reading. The stock sensor/tune showed 14kPa KOEO. With the 2 bar sensor in and set to 488, I'm seeing 19kPa KOEO.

Then there's still some work to do. They should match when it's right.

So.. why doesn't it read atmospheric pressure (or ~100 kPa) when KOEO? I would have thought that it would read the same as if the engine was at WOT. This was throwing me off the first night I messed with it because those numbers didn't make sense.

I'm trying to figure it out with you. It appears that the scanner is actually reading vacuum, not absolute pressure since it increases when the engine starts. Change your parameter to inhg and it might make more sense. See if there are any other MAP channels available that read in the opposite (normal) direction. If not, you should be able to create a custom math to achieve the same.

So if we set the multi to a point where it reads like the stock sensor... will it not go off map when in boost and freak out like the stock 1 bar sensor... Or.. Will it just move through the map slower (if that makes sense)?

This is why I said we might want to leave the scale alone and disable the barometer correction. The table for which, by the way, is not showing up in your tune.

Just trying to wrap my head around why each one is different.. one guy says he dropped his to 122 to make it happy with boost... one guy says 190.. another said he had to go to 260. What exactly is the multiplier doing?

Those guys apparently did approach this the same way. It doesn't seem like those changes would work properly based on what we just tested.

I appreciate you taking the time to point me in the right direction.

No problem. I don't have a JTEC vehicle right now, but I have owned several before HPT tuning was available.

Here is the log showing KOEO with it set to 488.
2 bar - 488.hpl

[Mr4btTahoe]

I'm trying to figure it out with you. It appears that the scanner is actually reading vacuum, not absolute pressure since it increases when the engine starts. Change your parameter to inhg and it might make more sense. See if there are any other MAP channels available that read in the opposite (normal) direction. If not, you should be able to create a custom math to achieve the same.

That's what is odd. KOEO.. it doesn't read like atmospheric pressure.. when it starts, the number goes up.. but then, if you rev the engine (drop vacuum), the number moves towards the bottom of the map. Same while driving. It is as if KOEO isn't accurate. As vacuum drops while running, it moves towards 100kPa on the map which makes sense.. but KOEO doesn't read as no vacuum/full load which you'd think it would.

Anyways.. I decided to start it at 488 just to see what it was doing. The start-up is perfect... clean/stable.. but a couple seconds in and it's idling at the bottom of the map as if the sensor has been doubled (like it has been). It still is idling smoothly though.. just RICH on the wideband (10.5) and hazing.

I'm thinking I need to scale it up further until it reads the 14kPa KOEO, then half it. Am I thinking correctly?

Here is the startup log showing what Im talking about.
2 bar - 488 - Startup.hpl

[spoolboy]

The tables in the editor are opposite of what you're seeing on the scanner. Did you look for another MAP channel ?

The difference that's left between the two sensors should be the offset. And you still need to figure out what's going on with the WOT depression thing.

Do you have a normal OBDII scanner that can read datastream?
Do you own a Mityvac or similar vacuum pump?

[Mr4btTahoe]

The tables in the editor are opposite of what you're seeing on the scanner. Did you look for another MAP channel ?

The difference that's left between the two sensors should be the offset. And you still need to figure out what's going on with the WOT depression thing.

Do you have a normal OBDII scanner that can read datastream?
Yes but it's limited on what it can read

Do you own a Mityvac or similar vacuum pump?
Yes

Here are all the MAP related channels. Logged a startup and light rev set at 488. Also watched injector pulse width.

I'm not sure what you are saying as far as the tables in the editor and scanner are opposite. They look the same and seem to function the same. In the scanner, the lower part of the MAP corresponds with higher pulse width, lower overall timing, etc.. which is the same in the editor.
488 Startup.hpl

[Mr4btTahoe]

... this scanner or PIDs are screwy.

So I changed all of my charts and such to match exactly what the editor shows... and now my MAP reading stock/stock is reading 100kPa KOEO.

I decided to take some decent stock logs with all the charts now matching what the editor shows for scale on both axis. I'm a bit confused as to why the KOEO MAP reading is now different. It's showing what makes sense.

Here are a couple logs but I think I've got enough data to start dialing things in for idle. I'm going to play around with the multi until it matches the new stock numbers and see what happens.
Stock KOEO.hpl

Stock - Free Rev.hpl

[spoolboy]

It looks like manifold vacuum is actually the channel that follows in the same direction as the spark and fuel maps.

One more test. Stock map sensor and stock tune - log manifold vacuum.

Oops, looks like you're already doing that!