NAXJA Forums -::- North American XJ Association  

Go Back   NAXJA Forums -::- North American XJ Association > NAXJA Unibody Jeep Technical Forums > Jeep Cherokee XJ (1984 - 2001) > Modified Tech Discussion
HOME Member FAQ Sponsor Info Rules Bylaws E-Mail

Modified Tech Discussion Forum for Tech related discussion for Modified XJ's and MJ's.

Reply
 
Thread Tools Display Modes
  #511  
Old April 15th, 2019, 15:00
ShoeterMcgav's Avatar
ShoeterMcgav ShoeterMcgav is offline
NAXJA Member
 
Join Date: Mar 2019
Location: Colorado
Posts: 247
Re: Project Unicorn - a light duty trail rig

On 91 octane fuel?
__________________
98xj lift 35s mid arms locked 9"/hp30 locked w warn hubs wj brakes hi steer etc work in progress..
93zj BEAST 35s Claytons LAs 44/hp30 lockers bumpers headers etc $old

Last edited by ShoeterMcgav; April 15th, 2019 at 15:04.
Reply With Quote
  #512  
Old April 15th, 2019, 15:01
ShoeterMcgav's Avatar
ShoeterMcgav ShoeterMcgav is offline
NAXJA Member
 
Join Date: Mar 2019
Location: Colorado
Posts: 247
Re: Project Unicorn - a light duty trail rig

9.35.1 if on regualr pump gas
__________________
98xj lift 35s mid arms locked 9"/hp30 locked w warn hubs wj brakes hi steer etc work in progress..
93zj BEAST 35s Claytons LAs 44/hp30 lockers bumpers headers etc $old
Reply With Quote
  #513  
Old April 15th, 2019, 15:03
cal's Avatar
cal cal is offline
NAXJA Warranty Voider
 
Join Date: Nov 2004
Location: Hammertown, USA
Posts: 17,393
Re: Project Unicorn - a light duty trail rig

Cranking compression.

The static and dynamic compression are in listed in the engine build thread
__________________
I'm not a complete idiot - there are parts missing.
Reply With Quote
  #514  
Old April 15th, 2019, 15:04
cal's Avatar
cal cal is offline
NAXJA Warranty Voider
 
Join Date: Nov 2004
Location: Hammertown, USA
Posts: 17,393
Re: Project Unicorn - a light duty trail rig

Quote:
Originally Posted by ShoeterMcgav View Post
9.35.1 if on regualr pump gas
And no, it's 11.4:1 running on 91.
__________________
I'm not a complete idiot - there are parts missing.
Reply With Quote
  #515  
Old April 15th, 2019, 15:05
ShoeterMcgav's Avatar
ShoeterMcgav ShoeterMcgav is offline
NAXJA Member
 
Join Date: Mar 2019
Location: Colorado
Posts: 247
Re: Project Unicorn - a light duty trail rig

Sooooo... I win? LMAO
__________________
98xj lift 35s mid arms locked 9"/hp30 locked w warn hubs wj brakes hi steer etc work in progress..
93zj BEAST 35s Claytons LAs 44/hp30 lockers bumpers headers etc $old
Reply With Quote
  #516  
Old April 15th, 2019, 15:06
ShoeterMcgav's Avatar
ShoeterMcgav ShoeterMcgav is offline
NAXJA Member
 
Join Date: Mar 2019
Location: Colorado
Posts: 247
Re: Project Unicorn - a light duty trail rig

#fail
__________________
98xj lift 35s mid arms locked 9"/hp30 locked w warn hubs wj brakes hi steer etc work in progress..
93zj BEAST 35s Claytons LAs 44/hp30 lockers bumpers headers etc $old
Reply With Quote
  #517  
Old April 15th, 2019, 19:02
trippled trippled is offline
NAXJA Member
 
Join Date: Apr 2006
Location: colorado springs, co
Posts: 2,231
Re: Project Unicorn - a light duty trail rig

Gonna say 183psi.

Been enjoying this build. Any chance you'll be able to post some videos of running and driving when tuning is done?
Reply With Quote
  #518  
Old April 15th, 2019, 19:06
cal's Avatar
cal cal is offline
NAXJA Warranty Voider
 
Join Date: Nov 2004
Location: Hammertown, USA
Posts: 17,393
Re: Project Unicorn - a light duty trail rig

Tuning is done. Now I'm looking for energy to do an oil change.
__________________
I'm not a complete idiot - there are parts missing.
Reply With Quote
  #519  
Old April 15th, 2019, 19:56
SlowXj SlowXj is offline
NAXJA Forum User
 
Join Date: Nov 2017
Location: East Tn
Posts: 64
Project Unicorn - a light duty trail rig

I'm guessing 200 even! Haha that is an insanely sweet build, and a gorgeous DD!

Sent from my SM-G950U using Tapatalk
Reply With Quote
  #520  
Old April 16th, 2019, 06:29
Ronbo's Avatar
Ronbo Ronbo is offline
NAXJA Member
 
Join Date: Apr 2003
Location: San Marcos, CA
Posts: 1,423
Re: Project Unicorn - a light duty trail rig

215 psi is my guess..
__________________
98 4.0, AX15, 241OR, RJ44/RJ60, Poly 3-link, Nationals, 35s.
Reply With Quote
  #521  
Old April 16th, 2019, 06:43
Anak's Avatar
Anak Anak is offline
Stranger
 
Join Date: Sep 2013
Location: In a strange land
Posts: 3,081
Re: Project Unicorn - a light duty trail rig

I will go 209.
__________________
Project "Scope Creep": 1996 4wd 4.0L, AX15
....

Baby it's cold outside.
Reply With Quote
  #522  
Old April 16th, 2019, 06:45
ShoeterMcgav's Avatar
ShoeterMcgav ShoeterMcgav is offline
NAXJA Member
 
Join Date: Mar 2019
Location: Colorado
Posts: 247
Re: Project Unicorn - a light duty trail rig

Quote:
Originally Posted by cal View Post
Cranking compression.

The static and dynamic compression are in listed in the engine build thread
Idk how I missed "cranking" the first Go around... How much miles have you put on her to seat the rings and valves? Numbers might get better after a couple K miles right?

Idk if stupid gets me another guess...

I'll take the over and say 222 psi
__________________
98xj lift 35s mid arms locked 9"/hp30 locked w warn hubs wj brakes hi steer etc work in progress..
93zj BEAST 35s Claytons LAs 44/hp30 lockers bumpers headers etc $old

Last edited by ShoeterMcgav; April 16th, 2019 at 07:22.
Reply With Quote
  #523  
Old April 16th, 2019, 06:55
sidewaysstarion's Avatar
sidewaysstarion sidewaysstarion is offline
Coffee Drinker
 
Join Date: Jan 2012
Location: Torrance, CA
Posts: 2,864
Re: Project Unicorn - a light duty trail rig

I'm going to say "$1 Bob."
__________________
Quote:
Originally Posted by cracker
I seem to have run out of self tapping washers
99 4.0/AW4/231, with a few basic bolt ons.

Click here to support
Reply With Quote
  #524  
Old April 16th, 2019, 07:31
Rockwood Rockwood is offline
NAXJA Forum User
 
Join Date: Sep 2011
Location: San Diego
Posts: 139
Re: Project Unicorn - a light duty trail rig

232psi.
Reply With Quote
  #525  
Old April 16th, 2019, 08:12
cal's Avatar
cal cal is offline
NAXJA Warranty Voider
 
Join Date: Nov 2004
Location: Hammertown, USA
Posts: 17,393
Re: Project Unicorn - a light duty trail rig

So when we last left off, I had the car running, and home, but had fuel pressure issues still and some pinging under low RPM load.

After replacing the fuel pump relay, I was getting super erratic fuel pressure readings. As it turns out, that was a combination of gauge problems, and the schrader in the NRT fuel rail being just a hair too deep in the fitting. If I pull the schrader out before hooked up a gauge each gauge gets a consistent reading, but I get very different readings on my HF and OTC gauges, which are different again from Chris Jenson's snap on gauge. I'm going to say the snap on is probably the most accurate, giving me 56 PSI. Inexplicably higher than the 49 PSI the new FPR should be giving me, but we're going to roll with it.



Chris Jensen from Christuned and our own Mark Nelson came by and wired the jeep up for diagnostics on Sunday. A digital fuel pressure gauge, a wide band o2 sensor, and OBD2 readings, all going into a data logger tied to Chris's laptop.





Not having ready access to a dyno on a Sunday, we used a local freeway on ramp to do hard WOT pulls, and then cruised to the next exit on light throttle to get more readings. Pretty fascinating stuff actually. I didn't take a lot of photos of Chris's work, but he built fuel and air maps to visualize what it is doing and made adjustments. This is the only map I photo'd, which was after the 1st adjustment.




I have no more photos of the process, but I'll talk about it.

At first the jeep at WOT was running so rich that it wouldn't register on the wideband o2. It took 3 tunes of trimming fuel before we could get good readings. With each adjustment the jeep got A LOT faster. About the 5th adjustment we started getting a good base, the low RPM pinging stopped but we started to get new pinging under WOT. I want to say we did 5 more ECU revisions, with each adding more pinging but did make us a lot faster, then Chris stepped us back a tune or two and added some more fuel under load, which stopped the pinging completely (but did take some power away). At the end of the day we ended up with near stock ignition timing and a lot less than stock fuel, but a bit more than Chris wanted to see.

He was able to tune the engine to running very well (and i'm super happy with it) but we did determine that maybe 11.4 is too much compression for a customer car. Russ and I are still talking about what to try next.

I'm sure I am forgetting things, but:
* Air/fuel map customized for my engine
* Timing adjusted to get the most bottom end and cut out pinging
* Aux fan set to come on at 180 so that it runs most of the time (my request)
* Idle bumped from 550 to 700 to smooth out idle vibration
* Threshold for misfire raised to limit the JTEC random misfire codes that haunt us
* Fast idle bumped from 1100 to 1300 (for future high idle switch addition)

Mark provided me with an SCT 9550 tuner which Chris loaded up with this tune, the factory tune, and a limp mode tune (-4 timing and add fuel) just in case I hurt the motor or get crappy gas while traveling.


Working with Chris was fascinating, and I learned a ton - mostly about how little I actually know. We discussed how he works with other customers, and his frustration that customers often want a magical tune but won't spend a couple hundred bucks on the equipment required to do data logging, and expect him to dial it in based on engine specs. Why spend $4000 on a motor if you won't spend $300 to see what it is doing and tune it? He doesn't understand, (I do, XJ guys are cheap).

After going through this process, I can tell you that there is no way you could do this just off of engine specs, and anyone who is selling a tune that way is doing you a disservice. If you have a custom motor and want to get the most out of it, i HIGHLY suggest you contact Chris for a list of what diagnostic gear to buy (you'll spend about $350) and get him some data logging, and talk about doing a tune (i can't say what his services will cost, you have to ask him).


After they left I took a cranking compression reading off of the engine, and went back over everything. I have a slight trans cooler leak that I'm going to have to pull the airbox and aux fan to find, and I clocked the exhaust away from the oil pan and have a slight exhaust leak to adjust now.


I am super happy with how the car drives now. Now that I have it in the final config I'm debating regearing to 4.56, and I certainly need to install a shift kit in the trans.

A couple of other things of note:

* Chris suggested I try a 180* thermostat. Village wisdom tells us that the ECU won't like that, but I've been told it won't be a problem and may help combat pinging if I get crappy fuel.
* My intake air temp was MUCH lower than Chris expected and sees with most other jeep engines. He attributed that to the aFe intake, and suggests that becomes something we recommend to people going forward.
__________________
I'm not a complete idiot - there are parts missing.

Last edited by cal; April 16th, 2019 at 08:16.
Reply With Quote
Reply


Currently Active Users Viewing This Thread: 2 (1 members and 1 guests)
xjspyder
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
New Project 89 XJ Unicorn zachxj01 North Atlantic Chapter 9 May 26th, 2016 16:39
Anyone use OME LIGHT DUTY leafs? djlarroc Modified Tech Discussion 19 August 10th, 2013 18:39
Project:Unicorn SAMSET Midwest Chapter 27 September 28th, 2012 10:58
WTB light duty truck tires XJwheelman NAC Classifieds 0 June 5th, 2011 14:41
Some light duty mods for a camping XJ terryd Modified Tech Discussion 10 January 11th, 2008 16:50


All times are GMT -7. The time now is 20:38.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
NAXJA and NAXJA logo's Copyright NAXJA. All content/images Copyright NAXJA 1999-2014