I would say no, it was a pig off the line before, and now it will spin a tire a bit from a dig. I know that's less than scientific, and I did a lot more than just the cam.
Dyno Testing Bolt-ons On The 4.0
- Thread starter Jezza
- Start date
I would say no, it was a pig off the line before, and now it will spin a tire a bit from a dig. I know that's less than scientific, and I did a lot more than just the cam.
I covered it little in the video, but the tune dyno session had some of it's thunder stolen by the 4 hole injectors. The baseline runs were overly rich and the tune would have corrected that and added power, however the 4 hole injectors were slightly smaller than the stock ones and leaned out the mixture before the tune session. That made it seem as though the 4 hole injectors made more power and the tune less. When in reality the tune could have done all of the corrections on its own. I think reasonable without the injectors the tune could have net about 5%-7%. You may call it DIY if you choose, but I have tuned hundreds of JTEC PCMs and thousands of other systems. There is only so much "magic" that can be done on a NA 4.0. Anyone who tries to tell you different is selling you something.
Apologies, bad word choice on my part. Your one of those folks that has the knowledge and experience to hand create a tune and you know it is right. I am barely a shade tree mechanic that would have to buy a tune and hope it is right. The rest of the bolt-ons I could accomplish outside the cam work and the tune. So I sit and over-think if it is worth it to send my ECM to FRP.
The big gain from the FRP tune is the timing table re-map. It adds as much as 30 degrees of timing over stock in a few places, at least for the 05-06 version.
I noticed a fairly substantial torque jump in closed loop (part-throttle) fueling. Open loop seemed to have modest gains as well. No quantitative data to back it up though.
Not sure how aggressive @Jezza was with his spark map.
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With the stock 4.0, in my 2000 XJ, and the HP tuners software I've not been able to run much more than stock timing at WOT loads without it pinging. I've tried de-carbon treatments etc to no avail. Even at 26 degrees at WOT it will ping, so i set it back to stock 23 or so. This is at sea level and running standard and mid grade fuel.
I would expect with proper quench and no hot-spot inducing sharp edges in the combustion chambers I will be able to run a lot more. The factory 4.0 heads I've seen leave a bit to be desired in this area.
Was any valve seat (ie 3 angle seats) or port work done to the head that was put on along with the cam in Jezza's video? I know the spring seats were machined and it, and the deck, were faced to increase the compression. If not, I wonder how much it would have bumped up the final hp figure.
Matt
I would expect with proper quench and no hot-spot inducing sharp edges in the combustion chambers I will be able to run a lot more. The factory 4.0 heads I've seen leave a bit to be desired in this area.
Was any valve seat (ie 3 angle seats) or port work done to the head that was put on along with the cam in Jezza's video? I know the spring seats were machined and it, and the deck, were faced to increase the compression. If not, I wonder how much it would have bumped up the final hp figure.
Matt
Have you tried colder range spark plugs? Under high loads, the OEM spark plugs can get too hot and pre-ignite the fuel. The Autolite XP5405 are identical to the XP985 except they are one level colder.
The caveat is that they also can be more prone to carbon fouling at extended low loads.
Note in this case “load” correlates with throttle position, not RPM. Someone who drives 1,500 RPM with a near wide open throttle may be better off with a colder plug than someone who drives 3,000 RPM with a barely cracked open throttle.
Yes, I fitted colder heat range plugs to see if it helped, but no bueno unfortunately. I used NGK plugs that don't protrude as far into the combustion chamber as the standard style ones. I'm not sure if that would be a pro or con. They protrude in approximately 1/4" as opposed to the 1/2" of the stock style ones.
I have a manifold vacuum gauge mounted to the dash, so understand what you mean about load. I like to use the term effective WOT - in that under lower rpms but high load you can reach zero vacuum on the gauge with only half throttle etc
Protrusion could definitely have an effect on combustion. Little minute changes like that can have a surprising impact. That said it's almost impossible to know if it would be positive or negative without actually testing it in a laboratory.
Going to a cowl intake actually made quite a difference in power and in pinging resistance. Colder intake air = less pre-ignition. Perhaps give that a shot. Certainly Windstar junkyard intakes are cheap. Bonus if you insulate it, and double bonus if you cerakote the intake and exhaust manifolds with low IR coating.
Then there's the hack method: just tune the Power Enrichment mode to run it stupid rich at WOT. I don't really care for this method as the power gains are tiny and it wastes fuel and can damage the catalytic converters, but it will stop pinging.
I actually dialed my PE back and set it to only come on if my foot is fully on the floor. Even just a hair off and it backs out into closed loop/stoich. This way I can run basically WOT at stoich and then if I hear pinging I can just press harder and stop the pinging immediately.
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I have an 04, so the same JTEC+ PCM as your 00 XJ. I live at 6000ft above sea level (~2000m) so can't say for sure whether it pings at sea level as my WOT manifold pressure is around 80kpa. But the 04 TJ main spark is between 12 at 1500 and 24.5 at 4992 in my tables and I don't believe I've edited them as I have to drive more than 600km in any direction to get to near sea level and don't want to find out it pings when I get there and by chance not have my tuning laptop and MPVI3 with me.
The 4.0L does not have a good quench with the stock pistons in spite of the low compression. They have a full circular dish and as I understand it most came off assembly with the piston .017"-.022" in the hole and a ~.040" head gasket. That doesn't make for a good quench pad against the head. The bathtub head is also pretty poor for inducing tumble and swirl. The low timing kinda compensates for that poor compression and quench design, but they are prone to detonation.
Regarding the head work, In the US, those trying to get the most out of the stock head are going to larger LS valves plus doing work on the ports and intake runners. The typical springs for those LS valves become an issue with flat tappet cams. Too high a spring rate for a cast flat tappet and they seem to often be either contributing to the lobes being wiped on initial break-in or squishing out the cam bearings a little ways down the road. You need a bit more than the stock spring pressure to go up above 0.500 lift, but not too much. You might also look into cutting Somender Singh grooves in the head.
There is alot of power on the top end to be gained in these modifications with a 4.0, but alot of time as well. They provide even more when increasing stroke for a 4.6L or 4.8L.
NAXJA and Jeep Strokers forums have more tech info from people pushing these 4.0L platforms if you want to find out what's working.
Also working on rebuilding a block for my TJ.
S and J engines has basic stroker for $3600.
Just adding up parts...granted slightly better parts...and machine work...I hit that number quickly...and that's not assembled, tested, etc.
-Mac
S and J engines has basic stroker for $3600.
Just adding up parts...granted slightly better parts...and machine work...I hit that number quickly...and that's not assembled, tested, etc.
-Mac
The pictures in that thread aren't working for me, but that's a new term for me, so I looked it up. Do you have a quick and dirty explanation so I can try avoiding the rabbit hole right now?
I'm not sure even Somender Singh could explain it, but the general idea is that these grooves on the quench pad side of the head direct the air with a bit more velocity into the combustion chamber increasing mixing at that very last "slap" part of the stroke. Unfortunately the air-fuel mixture is never completely homogenous, even in Port+Direct-injection engines.
With timing advanced, you'll already have a flame front in the combustion chamber and these grooves supposedly help accelerate mixing unburned air-fuel into that flame front, resulting in a faster and more complete burn inside the combustion chamber of the head at the top of the stroke. As I understand the theory, a faster and more even burn means more even distribution of the heat throughout the cylinder and thus no hot spots up in the quench pad area where most problematic pre-detonation issues begin. The higher the gas pressure at the top of the stroke, the more efficiently you generate power. But you also benefit from not having a lean or slow burning pocket up in the quench pad area.
But I'm not sure how effective that was in practice reducing detonation as he mentioned that it pinged on 91 octane. Keep in mind that's a 95 ODBI ZJ and there are no options to tune ignition or fueling directly with them and he may be running a bit lean trying to optimize fuel efficiency and power. The 4.0L generally gets an ridiculous amount of advance. The stock tune peaks above 50 degrees advance, but drops to 2 degrees at WOT and low rpms. Often strokers with higher than stock compression can benefit from a bit less advance.
With timing advanced, you'll already have a flame front in the combustion chamber and these grooves supposedly help accelerate mixing unburned air-fuel into that flame front, resulting in a faster and more complete burn inside the combustion chamber of the head at the top of the stroke. As I understand the theory, a faster and more even burn means more even distribution of the heat throughout the cylinder and thus no hot spots up in the quench pad area where most problematic pre-detonation issues begin. The higher the gas pressure at the top of the stroke, the more efficiently you generate power. But you also benefit from not having a lean or slow burning pocket up in the quench pad area.
But I'm not sure how effective that was in practice reducing detonation as he mentioned that it pinged on 91 octane. Keep in mind that's a 95 ODBI ZJ and there are no options to tune ignition or fueling directly with them and he may be running a bit lean trying to optimize fuel efficiency and power. The 4.0L generally gets an ridiculous amount of advance. The stock tune peaks above 50 degrees advance, but drops to 2 degrees at WOT and low rpms. Often strokers with higher than stock compression can benefit from a bit less advance.
I'm currently working on a cowl induction setup to draw in cooler air from outside. I've wanted to do one for ages but found it difficult to route from the stock airbox and fit under the bonnet (hood) of the XJ. Being a right hand drive means the abs pump and a/c accumulator is directly behind the airbox.
My current idea is one I've not seen before on a 4.0 Jeep. I'm using a carby style round air filter that mounts directly to the throttle body. This will be enclosed then have ducting straight back into to the firewall/cowl. It should be a fairly neat and compact setup. Because of space limitations Ive had to use a fairly small air filter (6x3") in a 9" enclosure. I would have preferred bigger but this size filter will still support the power. I will see how it goes.
After seeing the stark difference a cowl intake makes on Jezza's video it has motivated me further.
My current idea is one I've not seen before on a 4.0 Jeep. I'm using a carby style round air filter that mounts directly to the throttle body. This will be enclosed then have ducting straight back into to the firewall/cowl. It should be a fairly neat and compact setup. Because of space limitations Ive had to use a fairly small air filter (6x3") in a 9" enclosure. I would have preferred bigger but this size filter will still support the power. I will see how it goes.
After seeing the stark difference a cowl intake makes on Jezza's video it has motivated me further.
I use it primarily for towing behind my RV when I camp, however lately I have been driving it everyday. I have been getting 15ish MPG pretty consistently. I wanted to make a turbo kit for the 97-99 model TJs as well using the Boostwerks cast manifold, but I have temporarily suspended that project due to availability and packaging concerns. I may pick it back up in the future if I get some other projects caught up.
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