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Mods for the Adventurous Experimenters

11K views 59 replies 11 participants last post by  jeepgcoman 
#1 · (Edited)
A while back on the "Official mpg" thread I indicated I'd do a thread for the more adventurous experimenters among us. I'll start by saying that, of all the mods. I've done to both of my Hemi vehicles (they're both modded almost identically), a good exhaust system, including tubular or SRT (for the 5.7's) headers and some sort of 3 in. straight through muffler(s), and an aftermarket cam that I advanced (against everyone's recommendations) are the mods. that made, by far, the most difference. So far, at best, I am up ~100 RWHP and ~5 mpg on each. I just got back from a 2000 mile (actually 1956 miles) with my 5.7 LX and averaged, for the whole trip, 27.01 mpg, including in town, mountain climbing (over 7000 ft. once and over 6000 ft. 3 times) and high headwinds on the last leg (only got 25.047 mpg on that leg) of the trip. A little over 4 tanks of fuel (72.4 gallons to be exact) to go that distance. IMO, not bad for a 4500+ lb. vehicle, when loaded. Best distance (but not best mpg) per tank was, 514 miles on 18.35 gallons. I did the best on the first leg (465 miles on 16.55 gallons of 87 non-ethanol fuel, with 8 oz. of acetone added. Almost all driving (~75-80%) was between ~3000-5000 elevation.

Enough of that. Now on to the mods. Aside from a good tuner (either DS or SC), a good exhaust and intake (not as important), experimenting with valve timing, i.e. cam advance, I feel makes, by far, the biggest difference against money spent on other mods. If you can do all the labor yourself, you will be way ahead of the game too, but it is not for the faint of heart, and you must have some pretty good mechanical ability. As far as the tuner goes, for folks with the 545RFE transmission, I would highly recommend the SC tuner, only because it has a complete trans. tuning application that allows you to set it up any way you want. I have mine set up for maximum MDS on time, both in town and on the highway. The DS tuner offers more flexibility in engine tuning and allows for custom tunes, if needed. It does not, however, allow for complete control of the transmission. Again, against everyone's recommendations, I am running canned tunes with my custom transmission up/down shift schedules and torque management. I get no knock retard, and I get 13:1 A/F commanded at WOT. At light throttle, the O2 Sensors dictate a 14.7:1 commanded A/F ratio, no matter what.....assuming your O2 Sensors are in good working order. For this discussion, my main objective is fuel economy (FE), more than performance.

It is possible to get considerably improved FE along with modestly increased horsepower and torque. If one goes too far, you end up with more power and less FE. Essentially, the goal is to improve the Volumetric Efficiency (VE) of the engine, which allows it to process air and fuel more efficiently. The higher the VE, the better, but it is difficult to achieve, due to many factors. Also, for Hemi owners, increasing MDS on time is a plus. On the highway, it makes a 2-3 mpg difference on either of mine.

Most stock exhaust systems are relatively inefficient. They have restrictive log type exhaust manifolds and usually triple pass (flows rear, forward, rear) mufflers. The 5.7 WK manifolds are particularly poor, especially compared to the 5.7 LX's or the SRT-8 headers. See the difference between the LX and WK's here: http://www.jeepgarage.org/showthread.php?t=19490. IMO, this should be the first order of business. On the 5.7's, a good manifold and straight through 3 inch mufflered/resonated system is a must to help bring the beast to life.

Now to the cam. Because of good deals, I chose to use the FRI Engineering Sidewinder cams in both my Hemi vehicles, They have been well proven as a "torquer cam" in the LX community, and it has been around for probably 6-7 years. When installed "straight up", dyno tests have shown about a 50 RWHP increase, with no other mods. Unfortunately, like almost all aftermarket performance cams, they develop their torque and horsepower above 3000 and 5000 RPM, respectively. How much of your driving is done in these RPM ranges? I know since I did the cam installs, it's a lot more than it should be on mine. I love it!! Most of our "normal" driving, whether it be in town or on the highway is done well below 3000 RPM.

To rectify this, advancing the cam timing, whether it be stock or aftermarket, lowers the maximum torque/horsepower RPM ranges somewhat, depending on how much you advance it. Advancing the cam will also "kill" the top end performance to some degree, again depending on how far you advance it. On my Jeep, I advanced it only 2 degrees (using a Crower kit), mainly because I wasn't sure how much difference it would make. On my Hemi Magnum I got braver and advanced it a full 6 degrees. Cutting to the chase, IMO, the 6 degree advance delivered the best results by a noticeable difference. Next time I am into the Jeep engine, I'll be advancing it to 6 degrees also. It does start to flatten out above ~5800 RPM, or so though, but down low, it torques almost like a diesel now.

For those who want to give it a try, and don't want to spend a ton of $$$, I would recommend trying the advance trick with the stock cam. The Hemi cam timing gear has 52 teeth, so advancing it one tooth would be moving it 6.923 degrees ahead...my LX, with the 4 degrees already ground in by the mfg'er. is at ~10 degrees. If you don't want to go that far, do a search for the Crower Kit. Everyone (manufacturer, seller, and some forum members) told me not to advance the aftermarket cam because the additional lift and duration may cause piston to valve clearance issues, plus adversely affect the power curve. It hasn't! It's moved it down to where it is more useable for my purposes. Advancing the stock cam should be less of a P to V concern with the lower lift and duration. I know if I hadn't gotten the aftermarket cams, I'd have for sure advanced the stock cams. Bet an advanced stock cam would even outperform the advanced aftermarket cam.....on the bottom end anyway. Any takers?? For 5.7 owners that may want to try this, I'd be glad to provide any assistance I can.....FWIW.
 
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#30 ·
^ got your message,sent one back.

while I think some more about cam stuff, i was searching dampers. the slp looks good, then a ran across this:
http://www.buyracingparts.com/57-61l-hemi-25-ud.html
Is this the same tci that makes trannys? , if so thats a great deal! Oh, does antone know if there are any differences in the hemi dampers as in belts -ribbs,depth from block,......?
 
#32 ·
^ got your message,sent one back.

while I think some more about cam stuff, i was searching dampers. the slp looks good, then a ran across this:
http://www.buyracingparts.com/57-61l-hemi-25-ud.html
Is this the same tci that makes trannys? , if so thats a great deal! Oh, does antone know if there are any differences in the hemi dampers as in belts -ribbs,depth from block,......?
Never heard of the TCI unit on a 5.7L...doesn't mean it isn't good, just don't know anyone running one. The chevy guys like to run them, so they're probably well made. The SLP/Powerbond pulley is a proven performer on the hemis. However, you should give the TCI a try and let us know how you like it, IMO. As long as it has the lip on the back to keep the belt from slipping off, you're good to go.

Regarding the cam...save yourself the trouble of advancing the stocker, only to find that the gain is minimal, get yourself a Sidewinder, advance it a couple degrees, and be happy. You'll be able to chirp the tires with that cam and some advancement. Disable ESP and you may even get some fishtail action for a couple of seconds.
 
#31 ·
OK, someone please check my math-

The stock cam has a LSA of 113*, if it had a installed int centerline of 113* it would be straight up.
since its installed @124* is it advanced ,or retarded? I've been reading lots of different stuff, I thought it was advanced already, but now I'm not so sure.
 
#33 ·
By the way, the other night a couple of ricers were dualing it out from stop sign to stop sign here on Connecticut avenue in DC and I pulled up to the outside lane with my girlfriend in the Jeep. I wasn't going to race 'em, but the guy next to me had his windows down and could hear the Hemi loping away and shook his head as if it wasn't worthy of being in the same company as them (from what I could tell they had some engine work done and the typical coffee can exhaust). At that point, I told my girlfriend to hold on and when the light turned green, I punched it...she burned some rubber and I was instantly a length and a half from the guy next to me, who clearly had a faster car than the guy he had been challenging. It's been a while since I have done that (punched it from a dead stop) and have never burned rubber like that either...I must give kudos to Ryan and David, for I believe the trans tune they provided me with is responsible for getting the extra power to the wheels. I haven't gotten to the track yet and am looking forward to it now. Needless to say, those guys tried thier hardest to catch me (picture the sound of super high reving engines, one of which was hitting it's limiter...not sure which one) and were not able to. When we got to the stop light, the guy rolled up his window, ha ha!

Just thought I'd share...if you go with the SW cam, no one will know your Jeep's cammed and you'll totally surprise them.
 
#34 ·
^ sweet! I've only "played" on the highway so far -some knucklehead ran up on my rear in a const. zone in the middle of the nite-1 lane and was riding about 3' off my bumper....... in a challenger no less! i was already goin 5 over when he caught me,and he started doin the side to side crap.... I gave him about 2 seconds to move next to me when we got out of the const, then stomped on it... i hope it was a 6 cuz i smoked that fool,I looked down n i was almost double the speed limit with only real itty bitty lights in my mirror :cool: ah i do love this truck! I also have one of Ryans trans tunes :thumbsup: but the most ive gotten (with dry tires) was a chirp
But leaving the car wash....



i dont think i'm gonna change the cam for now, i'd like to do more at the same time, and cant do all that right now. from what i read ,I thought the stock cam was advanced,but now i think i read it too fast and its retarded, IDK :mad:
 
#36 · (Edited)
Verminator, I ended up spending $1500 for ceramic coated headers and modifying my existing 3 in. cat. back a couple times so the MDS drone was "wife" friendly. IMO, it's perfect now. As far as headers go, I think the best game in town, for the least $$$, is probably the SRT's. Problem is, if you can't find used, new ones run ~$1200 or so, and then you'd have to mate to the "Y" pipe, and cut a little off the trans. case for clearance. You'd also have to modify the passenger side one for the EGR to operate, or spend more $$$ and get it shut off through a custom tune by the DS folks. That means you'd need to have a DS tuner too.

When I started this thread, in addition to wanting to be adventurous and experiment, I probably should have added that this mod. (advancing the stock cam) is generally for the folks that don't want to, or can't currently afford to install an aftermarket cam. Although I haven't tried advancing the stock Hemi cam, I still maintain it would make a fair amount of favorable difference in lowering the torque/power curve to an RPM range that the vehicle is most driven in. Had I not done the aftermarket cams, I would be on here telling how advancing worked on the stock cam. I have, in the past, advanced a stock cam, and it did make a considerable difference too. Before doing it, I did check the specs, and determined one tooth would be fine.....and it was. That vehicle was a '74 Chevy Nova, 250 C.I. six (cam advanced one tooth), close ratio 4-speed, headers and a 500 CFM Holley 4 bbl. carb. It had no problem beating most relatively stock small block V-8 Chevy's.

As far as one other option for the exhaust, again for those who don't want to, or can't currently afford to, I recommend trying to fit the stock LX exhaust manifolds in place of the stock WK logs. I did a thread on it, and there is a considerable difference in the two, and I, personally, think some gains can be made with this mod. Again, it is for the person who wants to do a little experimenting. Here's the thread:

http://www.jeepgarage.org/showthread.php?t=19490
 
#41 ·
^^^....an almost LX motor. The pulleys are the same though.
 
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#43 ·
Did it come with a new crank bolt? If not, it should be changed.
 
#45 ·
Well,i finally got this done! I changed to a 6.1 tensioner (just to be safe) new waterpump,changed the oil,and THE PULLEY.For the sake of comparison, I did NOT clean the TB, air filter,seafoam it etc...
I live about an hour from wichita,ks . the last time we went,with a 75 mph hwy avg and a bit of town driving the evic showed 15.4 mpg. last nite we went with the same 75 mph cruising, and a bit more in town driving (and yes i hit it a little bit) but this time the evic showed 15.8 mpg!
I know thats not much, but it IS better. My plugs are due for replacement, but i wanted to get a good idea of what just this pulley did,before changing them. Oh and it revs quicker too :thumbsup: MUCHO BEDDA!

some pics: 5.7 tensioner- note the 2 "springs"


and the 6.1 has 4

the pulley was a pain,had a problem with the bolt threads, but big difference

if anyones gonna do this here's the belt you need
 
#46 ·
I didn't realize you were going to pull the front cover too. I would have recommended you advance the cam while it was apart. Would have been easy to do and, I still say, it would make a fair difference on an otherwise stock engine, especially in the low/mid ranges where it's driven most of the time.
 
#49 · (Edited)
Kevman, thanks for bringing it back up. I am at it again, and this reminded me of a few things.

4.whoa, I am starting to look at UD pulleys now and need some of your experience. The SLP, 847-100235 shows it needs a 6PK2025 belt. I see you used a 6PK2020 on yours. Is your pulley the same 25% UD as the one above? Also, since you changed your tensioner, did you pull the radiator (the worst part of the cam swap), or were you able to do it with everything (pull the front cover) in place. I am thinking that if I do the UD pulley I may as well advance the cam to 6 degrees while I am at it.....but I don't relish pulling the radiator/AC condenser again.

Also, since you've had the UD on for awhile now, what are your final assessments? Any improvement in fuel economy? Any battery/electrical/cooling issues because of the slower turning accessories? Thanks for your help.
 
#52 ·
4.whoa, I am starting to look at UD pulleys now and need some of your experience. The SLP, 847-100235 shows it needs a 6PK2025 belt. I see you used a 6PK2020 on yours. Is your pulley the same 25% UD as the one above? Also, since you changed your tensioner, did you pull the radiator (the worst part of the cam swap), or were you able to do it with everything (pull the front cover) in place. I am thinking that if I do the UD pulley I may as well advance the cam to 6 degrees while I am at it.....but I don't relish pulling the radiator/AC condenser again.

Also, since you've had the UD on for awhile now, what are your final assessments? Any improvement in fuel economy? Any battery/electrical/cooling issues because of the slower turning accessories? Thanks for your help.
I used the summit C2515 it's 20% UD. with the belt i used my tensioner was just on the tight side of the center of the range


the only reason I pulled the radiator is cause i had trouble with the damper bolt threads.I had the tensioner and water pump done & the engine painted with it in.

Well, lets just say I REALLY enjoy driving this thing :p on the highway OMG! this thing is a beast! It is so easy to not realize how fast it is. I was bypass'n town on the hwy with it in 3rd (I keep it down in town)I hit it to get around traffic, and when i looked down it was @110!:eek:

I have not noticed my mpg's going up, BUT my 22's have short tires on them. I have had to change my batt this winter, but it was in the jeep when i got it and ive had it for 2+yrs. I have not had any cooling issues and we had alot of 100+* days this summer. I've driven it to NJ twice and also to MI in all types of weather.
I think that once I get some taller tires for my 22's (closer to stock height) , some taylor shorties (still have stock crap wires) & service the trans (a little past due) my mpgs should pick up (as long as my foot stays light :D
 
#50 ·
im curious into this too, so what will happen if i were to advance the cams in the 3.7 one tooth? i can post the cam specs later on.
 
#51 ·
First, let me say that I've successfully advanced cams on 3 different vehicles, so I think (I hope) I can help a little in this regard. Before you do anything you should research the stock cam timing and see where it would be after you advanced it. You could compare it to a similar six cylinder vehicle that is a little more powerful. As an example, the unscientific way I did my first cam advance was when I did it on my 74 Nova six (see my post No. 36, this thread) I compared the timing to a Jaguar XKE, as both were in-line sixes, with the XKE putting out more power than the six cylinder "smog" motor. Advancing the Nova cam one tooth (count the number of teeth on the cam timing gear and divide by 360 degrees to find out how much one tooth is worth) made the timing nearly the same as the XKE, although the lift, durations, and other specs. were a little different. It worked out fine, and I think most would, since the manufacturers are fairly conservative. Also be sure to review this info. Technical Specs & Information to be sure you're going to accomplish what you plan to do. Remember, you'll also lose some top end power, but it should run quite a bit better on the low/mid RPM ranges if you advance it ~6-8 degrees. This is really just the "poor man's" way of getting a little more low end power, especially if no one makes a cam for your application.
 
#53 ·
Thanks for the info. I have a couple more questions....is the Summit pulley aluminum or metal? How do you think the 25% UD would work, since your's is a 20%?
 
#57 ·
Its about leverage. the smaller pulley is easier to spin- takes less effort/power. engine revs quicker due to less drag, but accesories spin slower. its fine on the street,but if you have a MONSTER system or do alot of crawlin or low speed 4wheelin , it might not be the best.
pic to compare:
 
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