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jeepgcoman 04-30-2012 04:08 PM

Mods for the Adventurous Experimenters
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: 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 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.

4.whoa 05-01-2012 03:35 AM

Re: Mods for the Adventurous Experimenters
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:

05wkguy 05-01-2012 07:34 PM

Re: Mods for the Adventurous Experimenters
Some awesome information there! Although it doesn't apply to me I think it's great to see someone try something noone else has.

jeepgcoman 05-01-2012 09:07 PM

Re: Mods for the Adventurous Experimenters
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?

jeepgcoman 05-01-2012 09:13 PM

Re: Mods for the Adventurous Experimenters
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:

Kind of interesting for sure.

4.whoa 05-02-2012 03:36 AM

Re: Mods for the Adventurous Experimenters
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.

jeepgcoman 05-02-2012 11:16 AM

Re: Mods for the Adventurous Experimenters
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.

amw5 05-02-2012 12:08 PM

Re: Mods for the Adventurous Experimenters
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.

FlyinRyan 05-02-2012 12:16 PM

Re: Mods for the Adventurous Experimenters
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?

JeepCoop 05-02-2012 12:22 PM

Great thread!!!

jlewissystem 05-02-2012 12:47 PM

Re: Mods for the Adventurous Experimenters
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?

4.whoa 05-02-2012 04:33 PM

Re: Mods for the Adventurous Experimenters

Originally Posted by jeepgcoman (Post 623058)
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.

Do you happen to know if the stock cam has any adv/ret ground into it? if i skip a tooth, for about 7* where will it actually be? i dont want to go too far, as i do like to run it down the track :D

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