Question for Renix gurus

[1988JeepXj]

I have an '88 XJ I just threw a HO engine setup into, and I was curious if anybody had any pointers to tweak a few extra ponies from a stock(ish) setup.

Its a '91 HO 7120 head, no porting (yet), stock cam (for now) 99+ intake, straight bore TB, Renix injectors (which I think is where its held back).

I do have a MAP adjuster hooked up, and having read that thread about adjustable timing, I'll probably pick up one of those sweet brackets discussed in there, if nothing else to have it for my soon-to-be stroker build.

I should clarify that from my research I was to understand that HO injectors in a Renix setup would result in ~10mpg (maybe I interpreted wrong, or maybe that was HO injectors in a Non-HO motor setup). It doesn't ping or lean-pop anything, it just seems like power output is low.

Other issue (possibly unrelated); I had the Jeep on a Snap-On scan tool yesterday, and my O2 voltage would fluctuate between ~4.8-4.9v, which should indicate a lean condition. Maybe my o2 is bad? Or is the HO setup really running that lean with the Renix injectors? I'm not sure where to go from here, should I swap in my extra set of 21lb/hr injectors?

It purrs like a kitten, and drives amazing, throttle response is out of this world, at least compared to the stock setup. It just seems a little low on power for what I would think it should be being a (theoretical) ~20hp increase over "stock".

Tips, pointers? Thanks in advance.

 

[eflores]

remember that a renix motor makes more torque down low so seat of your pants dyno is gonna say this thing doesnt romp off the line any more.....id run 19# ford injectors...you shouldnt need a map adjuster....and get the high altitude CKP sensor i was talking about in that thread....and your 14hp over stock comes in at 3500ish RPM....so you never notice it

 

[old_man]

Your MAP adjuster can make it run lean. That is what it is for, adjusting the mixture. Be careful, running too lean can burn up an engine.

By the way, the HP difference between Renix and HO is more in how they measured it than what the engines really put out.

 

[1988JeepXj]

remember that a renix motor makes more torque down low so seat of your pants dyno is gonna say this thing doesnt romp off the line any more.....id run 19# ford injectors...you shouldnt need a map adjuster....and get the high altitude CKP sensor i was talking about in that thread....and your 14hp over stock comes in at 3500ish RPM....so you never notice it

My old Renix engine was poop, I can feel a difference off the line, but thats the only difference I can detect. Probably because of the increase in TB size, but my concern is on the express way, and upper RPM range. It pretty much runs out of oomph at 70mph, which is all well and good, its not a racecar, but it should definitely have more than that.

I'll surely pick up one of those high altitude crank sensors.

Your MAP adjuster can make it run lean. That is what it is for, adjusting the mixture. Be careful, running too lean can burn up an engine.

By the way, the HP difference between Renix and HO is more in how they measured it than what the engines really put out.

I mainly threw the MAP adjuster in for kicks, I built one for the heck of it and popped it in with the new engine. I experimented with it a little, I never set it below 5v to the MAP, but its normally just in "bypass" mode.


The Jeep will eventually see a stroker, possibly by the end of this year.
I just figured if anybody had any advice say, to better tune the Renix computer to the HO engine, this would be the place to ask. My main goal would be to manually replicate what one with a SBEC or JTEC XJ would get out of a chip, if possible.

 

[Dr. Dyno]

I have an '88 XJ I just threw a HO engine setup into, and I was curious if anybody had any pointers to tweak a few extra ponies from a stock(ish) setup.

Its a '91 HO 7120 head, no porting (yet), stock cam (for now) 99+ intake, straight bore TB, Renix injectors (which I think is where its held back).

I do have a MAP adjuster hooked up, and having read that thread about adjustable timing, I'll probably pick up one of those sweet brackets discussed in there, if nothing else to have it for my soon-to-be stroker build.

I should clarify that from my research I was to understand that HO injectors in a Renix setup would result in ~10mpg (maybe I interpreted wrong, or maybe that was HO injectors in a Non-HO motor setup). It doesn't ping or lean-pop anything, it just seems like power output is low.

Other issue (possibly unrelated); I had the Jeep on a Snap-On scan tool yesterday, and my O2 voltage would fluctuate between ~4.8-4.9v, which should indicate a lean condition. Maybe my o2 is bad? Or is the HO setup really running that lean with the Renix injectors? I'm not sure where to go from here, should I swap in my extra set of 21lb/hr injectors?

It purrs like a kitten, and drives amazing, throttle response is out of this world, at least compared to the stock setup. It just seems a little low on power for what I would think it should be being a (theoretical) ~20hp increase over "stock".

Tips, pointers? Thanks in advance.

I think your HO set-up is running too lean with the Renix injectors, so I suggest you throw in your spare HO injectors with new o-rings and feel the extra power. With those in place you might not need to set your MAP adjuster any higher than the stock 5.0v.
If you live at a high elevation, you could try the HA crank position sensor but it would be easier just to slot the bolt holes in your existing sensor and move it against the axis of crank rotation (i.e. counterclockwise when facing from the front) to advance the ignition timing.
Finally, port that 7120 head of yours and shave a few thou from the surface to raise the CR. You'll only feel the difference from 3000+rpm but there's an easy 15hp hidden in there.