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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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#2 ·
I have thought about this a little bit. So you advanced your magnums cam by 6* so its actually 10* because of the "built in" adv and that kills it before 6k. So, where do you think an actual 6* adv would fall off ? I understand the stock cam will be different (smaller),so it would probably fall off sooner,right?
About the crower kit- does it have tensioners comprable to the 6.1? everything ive seen about 5.7 camming says to get the 6.1 tensioner. is it true that it takes special tools to remove/install the balancer? I'm about to change out my weepie waterpump,so it would be about the right time to get in there :brows:
 
#4 ·
4.whoa, you're right, the Maggie is now at a total of 10 degrees. The Jeep only has 2 degrees (total of 6 degrees) on it. Next time I get into the Jeep, it'll get 6 degrees too. The Maggie will rev to 6200 RPM, but power starts falling off fast above ~5800 RPM. The Jeep will pull hard all the way up to ~6200 RPM. It's hard to tell what the stock cam advanced 6-7 degrees would do, but I would think it would start falling off at ~5000-5400 RPM. If I had another Hemi, I'd try it, LOL!! Who cares though? You've got 5 forward gears. On the Maggie, I've lowered the WOT upshift points back to stock, which is ~5600-5800 RPM. It's got enough torque to keep pulling hard, even though it has lower RPM shiftpoints.

The Crower kit comes with a 5.7 tensioner. I have two new ones if anyone needs one. The 5.7 tensioner comes with two tensioning springs and the 6.1 has four. Also, the 6.1 tensioner (part the rides on the chain) appears to be made of a different material than the 5.7 one. A new 6.1 tensioner runs about $25, so it's well worth the $$$.

To remove the crank pulley, you'll need a standard crank pulley removing tool. To reinstall, you can start it with a 2X4 and dead blow hammer, and then pull it on the rest of the way with the old crank pulley bolt. You'll need a new bolt anyway, in addition to front cover gasket (o-ring type), crank pulley seal, and some RTV. It is a good time to change the other stuff too. I changed the water pump, cam sensor and drive belt at the same time.

What's your plan....advance the stock cam or go aftermarket?
 
#5 · (Edited)
05wkguy, thanks! I didn't talk to anyone that supported my plan. That's why the first one I did (Jeep) I only advanced it 2 degrees. With the Maggie I got brave and went all the way. As I said above, I'll go to 6 on the Jeep if I ever have to get in there again. I won't make a special trip though. Here's some good reading that gives one an idea of what different cam specs., and the effect of advancing and retarding does for power and torque: http://www.compcams.com/technical/FAQ/LSAproperties.asp


Kind of interesting for sure.
 
#6 ·
For now, just adv the stock one. like every good gearhead, I'd like to "go big" but it will have to wait. if I dig into one more engine with all the ones i still have apart my GF will
(cuz ya know,since its apart i should do this too...and this ..and....:p).
I need to get that 6.1 tensioner and make up my mind on the "skipping" a stock tooth or getting the crower kit .Hmm.
 
#7 ·
With the Crower kit, unless your existing timing set is excessively worn, you'll only be able to use the cam gear with the adjustable offsets. That's what I did. To get the crank gear off you'd have to remove the oil pan and oil pump. Oil pump come off easy on the Maggie, but pan has to come off on the Jeep.
 
#8 ·
Good info here...

I advanced my cam 6*, but it was ground a couple of degrees retarded. I just got 17.5mpg on a recent highway trip from western NY to northern VA. Around town, I average 8.5-9mpg...MDS deactivated and lifters removed. I tried a tune that had the injector timing advanced and noticed a fuel smell at idle and it ran a little rough. I'd like to try retarding the injectors a bit to see what that does. Idealy, this should be done on a dyno, but I, nor my tuner thought of it during my tuning session.
 
#9 · (Edited)
This is an interesting thread. Subscribing....

If you can find ethanol-free fuel, this in itself is probably worth 1 MPG. I found a station here in FL with ethanol-free 90 octane, and while I didn't need the extra octane, I noticed an immediate difference in how it ran (was on fumes). You wouldn't think adding 10% ethanol would make a difference, but it does in a variety of ways.

I've recently tried a different strategy than Jeepgcoman has as far as tuning is concerned, with good results (+2 MPG on 91 octane). There's more than one way to go about it, you can either go a little lean (lean cruise, etc), or tune for best torque.

Jeepgcoman- what kind of differences in load/MAP (Pratio) are you seeing as a result of your various mods?
 
#11 ·
Agree - this is a LOT of great info and from experience, which is awesome! I'm looking into getting SRT headers for my 5.7. I would start with this MOD and expand on it - would you say that it was worth it, alone AND can you stick with a single cat-back or would you suggest duals?
 
#13 ·
Sorry, I am really not sure about the stock cam specs. You can probably do a internet search and come up with the specs. though. I am sure it is "straight up", and one tooth (~7 degrees) should bring some results. I am not sure about going 2 teeth, but I am sure it would work on the stock cam. It just may be a little too much advance though. Would be fun to experiment, again if I had another Hemi laying around. As a guide or reference, I think I'd bump the stock specs up against a mild aftermarket cam (like the Sidewinder) and see how the timing compares. Remember, earlier opening (to a point) will deliver more low end torque. You could back the Sidewinder specs. up ~10 degrees and that's where mine is on the Maggie. Then see how many degrees it would take to get the stocker to a similar position. Not very scientific, but it should give you a good idea of how far to go.
 
#14 ·
Well, i did some googling and found that the stock (05at least) hemi cams have:
196/196 dur @.050
113 lsa
.477/.462 lift
124 - int centerline
also found -valve timing:
int -open BTDC 5.0* closes ATDC 255.0*
exh- BTDC 236* 32*

When looking up "05 hemi stock cam timing".... this thread popped up 3X's:lol:
everything else kept going to that damn vvt or aftermarket install articles.

anyone know a good (free) place/program to play around with this to see what it does?
 
#15 ·
I would think advancing the stock cam may provide superior low end to stock, but top end would drop off like a brick due to the short duration. Might not be good for those who have intentions of racing. For those that just drive around town, it'd probably be a beast.

Even a small cam like a 6.1 OEM grind advanced would work well (this is a proven setup in the Rams) while providing at least stock or greater gains at higher rpms too.

I'd also like to see someone try to use a short-duration, tighter LSA cam like a KRC 210X in a Jeep to see how it does on mileage. The lower LSA would bring on the tq peak earlier and stronger.
 
#16 ·
I agree with Ryan, especially the shorter duration somewhat killing what little top end the stock 5.7 has. I do think the bottom end, say ~0-80-85 mph would be a killer though. A guess is that the revs. would begin to flatten out slightly above 5000 RPM but, IMO with the WK gearing, there wouldn't be too many so-called factory hot rods that would be able to keep up. (Caveat: must do cam and complete exhaust) How much driving does anyone (except maybe me) do that's above 5000 RPM. Dang, I love to have my foot in it. Only two 6200 RPM first gear runs today though.
 
#17 ·
Well,now that my balloon is popped..... :lol:

What can the stock 5.7 valve train handle? I see several cams where it says they can be used with stock springs, but they only showed duration, not lift #'s ...except from good ol ma mopar # P5153325AB 204/210.5 dur and .500/.488 lift with 116lsa I really would like to NOT have to change the springs n stuff @ this time,but now the bug bit me so i'd like to do something while i'm in there :p
I found this article where they swapped several comp cams, but didnt seem to change springs.....what do you think? with the longer dur. they could be advanced and have the best of both worlds,right?
http://www.popularhotrodding.com/enginemasters/articles/smallblockshootout/0602phr_hemi/viewall.html


Oh, i love to romp on it, but i drive cross country several times a year, so i need a good balance
 
#19 ·
I'll concur with Ryan again on the use of stock vs. aftermarket/6.1 springs AND pushrods. While you can run stock springs on a longer duration, higher lift cam, it is certainly not recommended. I have heard of a few doing it, but only temporarily until they could change them. You'll end up with a high chance of valve float and/or p to v collision if you run the RPM up too high with the stock springs. Don't know if you could coil bind them or not though. It's not that big a deal to change the springs with the heads on. I did it to both my Hemi's, the Jeep actually being easier than the Magnum. At the same time I changed the valve seals and the pushrods.

I too do a lot of highway driving, mostly trips ranging from ~200-2000 miles...about 8-10 times a year. That's one of the main reasons I tackled this experiment.

4.whoa, your balloon is not popped. Just a small amount of air let out of it. All this can be done without a huge expediture. I did both my cams and complete kits, with the Crower advance kits for a little less than $1000. Gaskets, valve seals, etc. was about another $100. Doing this mod. with stock cam and leaving the springs alone shouldn't cost $200 if you use the Crower kit, or around $100 if you just advance the stock timing set. Changing water pumps and belts, etc. would be extra though.
 
#20 · (Edited)
what is the main difference in a 6.1 springs ? just the spring pressure ?
while $1k is not a huge amount , I have it earmarked for rims( 1st things 1st) :D
maybe I'll just advanced it 2* ,that shouldn't kill top end too much, right ?

I ran across something while searching that said a 6.1 damper on a 5.7 ,is 5% under driven however elsewhere I saw a damper listed for both the 5.7 and the 6.1 anyone know for sure ? I would imagine an underdrive pulley would help a little in the mileage department as well .
 
#27 ·
what is the main difference in a 6.1 springs ? just the spring pressure ?
while $1k is not a huge amount , I have it earmarked for rims( 1st things 1st) :D
maybe I'll just advanced it 2* ,that shouldn't kill top end too much, right ?

I ran across something while searching that said a 6.1 damper on a 5.7 ,is 5% under driven however elsewhere I saw a damper listed for both the 5.7 and the 6.1 anyone know for sure ? I would imagine an underdrive pulley would help a little in the mileage department as well .
I had the SLP underdrive pulley and it definately made a difference...don't waste your time messing with the stock cam. As Ryan stated previously, going with the 6.1 cam and advancing it a bit would produce the results you're looking for. I almost went with the KRC 210x cam, but went with a Super Spartan custom grind from Stu at Inertia...advanced a bit, that cam would have been great down low...slight lope to it and great street manners.
 
#21 ·
If you're going to go through the trouble, I'd go get a ATI damper. Quality piece, balanced well, and more of a underdrive.

I would open the exhaust further before attempting to work on the cam timing.
 
#22 · (Edited)
X2 on the exhaust before the cam timing. Also, at 2 degrees you probably wouldn't notice much difference at all on either end. I'd go a minimum of 6, or not at all. Remember, my cam had 4 degrees ground into it by the mfg., so 2 degrees gave it a total of 6 degrees. The Maggie at 10 degrees total is way better, IMO, but you can't get there easily with the stock cam. I considered the underdrive pulley, and maybe I'll do it later. I'd like to know if anyone has measured the benefits as far as performance and FE?? It's a fairly easy swap if/when the time comes.

Edit: Oh, sorry, the 6.1 springs have more spring pressure and have bigger diameter coil material. The $1000 was for both vehicles, so one would be a lot less. My wheels are going to be the last thing I do. I screwed up when I bought it and bought new tires almost immediately. Now I have to wait until I wear them out. Bummer!!
 
#23 ·
I've been refreshing my memory by rereading some cam stuff.

If a cam has an LSA of 113* (stock) and is installed with the int centerline @113* then it's "straight up"
But, the stock cam is installed @124* ,so it's already advanced 9* as it is.

I havent been driving my baby since it has a water leak, so i'm gonna take her out today and play around-see where she pulls. I'm thinking that i might give it another 4* (we'll see)
I know you have bigger/different cams,but the 4* diff in your 2 gave the power band a 400 rpm shift lower, not that it will be a match,but thinking it should be similar.

I have done a cat back already and ,while i have plans for srt mani's, I dont see how advancing the cam will need that 1st, without changing to a bigger cam, the airflow wont really change, so while it's no doubt benificial , i think i'll do this while im working on it ,and get that on the short list.

I have a bad habit of " while this is apart,thats the next part,so..." and one thing leads to another,so I'm gonna draw myself a line:giveup: at advancing the stock cam and save the cam/lifters/springs/porting for another time.
 
#25 ·
#26 ·
LOL, 4.whoa, you sound like me. I don't blame you, I was tentative at first when I did the WK, not being sure how far to go, if it would work, or if I'd have problems, etc. Best thing to do, is like you're doing, lots of research, until you're "kind of comfortable"!

I think, on my Jeep, the power band is not low enough yet. I feel like it's just at the bottom of the torque range at ~2000 RPM. I took the Maggie for a ~125 mile run today and did what you are doing.....checking torque/power ranges. With the true autostick in it, I can lock in any gear so it won't upshift or downshift until I move the lever. I drove it about 90 miles in 4th gear, at speeds from ~60-75 mph. It pulls good from ~60/1800 RPM, but it's a whole bunch stronger from ~70/2400 RPM on up. It's also a lot quicker from a start than it used to be. I'd be real interested to see how and where the stock cam comes on, as I never did that kind of testing. I'll also try to do similar testing with the Jeep, but I don't think I can keep it from downshifting.
 
#28 ·
OK,well i took her out a bit today on the bypass and it really seems to start pulling about 3200 rpms & didnt seem to drop off much up top *disclaimer: I dont have a true autostick, or any hills around to help load 'er up so this an approximate butt dynoing :worried: *

I have one of Ryans trans tunes
and it pulls solidly to 6k and while it MAY be tapering off it shifts to hard (in a GOOD way :thumbsup:) to notice it.

I am going to advance the stocker for now and see what happens, and i'm going to do some looking around @ dampers. i think, for now, thats it.

Well I do REALLY need a custom tune too..... Ryan, are you going to be getting back into the DS stuff ? I really want one! :D I wanna see how quick the stock hemi can run
 
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