Rockyhud

Well, since installing the 3K gsk I've been a bad boy and ground my stock fuel plate to replicate a TST #10. When I installed it I put it in the stock plate's position so I'm not fueling it as hard as it could slid forward - playing it safe somewhat. I've "played" with it just a little and I can definitely say I''ve been bit good by the bombing bug. I know, I know I need gauges - these are on order and I've restrained myself by not getting into the throttle very deep or very long (maybe 3-5 secs at most) until the gauges are in, but man, what a kick in the pants this combo is. I've also installed a NAPA 542790 BHAF and over-sized heat shield to help with the air in and now I'm working on the exhaust side.

Recently I was reading in one of the topics here about what size the exhaust needs to be with respect to where in the system you're refering to and the impression I got is that the larger diameter exhaust needs to be closest to the heat source in order to let the gases flow out with the least restriction and as the gases get further away the diameter requirements aren't as great. Now, with that in mind and since I'm having to do my mods really on-the-cheap, at least for now, I was thinking that I could achieve a better flowing exhaust, to help control EGTs somewhat, if I installed a 4" downpipe and integrated it into the remained of the stock system. Once I'm financially able to do so I will install the rest of the 4" exhaust.

So, what do you guys think about my logic? Is my exhaust system workup worth doing or would it not gain me much or possibly anything at all? Keep in mind that I'm not towing anything at this time and most of the time driving like I have the proverbial egg between my foot and the throttle to get the best mpg I can. However, in the hopefully not too distant future I will be towing some - I'll be hooking up our 18ft car hauler trailer and using it to move some of our belongings and eventually our far-from-stock CJ-7 from the rental we're in now to somewhere else better, whether that's back to Colorado or elsewhere. The trailer weighs 2K and the loads will be in the 4-6K range. I'll be doing this at least a couple of trips, possibly 3 or more with some of the terrain possibly or even likely being in the Rocky Mountains.

As always, I really appreciate getting any and all feedback from you all. So, if you have any suggestions or comments please let 'em flow.

Steve

BoostdCTD

If you're looking to do a cheap mod on the exhaust just straight pipe the stock exhaust, I think that'd be more effective than a 4" downpipe with a stock exhaust.

mkrenn

YOU MUST get rid of the resinator at least. I had a 96, first thing I did was the exhaust. I went straight ALL the way. Sound is good!
Diffinetly watch your foot untill you get gauges.
Mine would temp out very easily. Especially in 5th gear.
If you dont like too much sound, cut off the reinator and muffler, then install a straight through muffler.
I have more ideas you you want them.

vssman

"Controlling" EGTs is one of those mythical things.... Just as they seem like they aren't getting too high, you end up doing another mod adding more fuel...

Rockyhud

Thanks for the ideas guys. I thought about running a straight pipe but I've read several folks comments here that this often causes the dreaded droning at hi-way speeds and increases the overall noise, both of which I've rather avoid if possible.
One downside to this though is spending money for a muffler replacement pipe that would eventually be discarded when I go to the 4" system. Part of my thinking of using a 4" downpipe with the rest of the stock system is that it would not be replaced later on, only added to with the rest of the 4" system.

Another thing I'll likely have to contend with are the emissions laws if I move to the front range area of Colorado. This means I can't get rid of the cat, or at least the appearance of having one. The last time I lived there they checked my truck for exhaust opacity but I'm not so sure they would know the difference if the guts of the cat were gone or if it was replaced with a resonator/small muffler of maybe even care. Here again, if I replaced the cat with a small resonator I'd want it to be a 4" so I could continue to use it when the whole system is in place.

I've thought about gutting the cat and reinstalling it, but if the emissions testers are real sticklers for OEM cats and checking for certain levels of emissions I might be forced to buy another one which I'm sure wouldn't be cheap. Anyone from the Denver area (the most stringent test area) know if emissions test stations are checking for OEM appearing cats and for emission levels, especially for 97 or older diesels?

Here again if anyone has any knowledge or suggestions to pass along it will all be appreciated and considered.

Steve

Haulin_in_Dixie

A '96 does not have a resonator, it has a cat.

Rare1

Rocky, at annual emmisions testing here they eyeball the cat and test exhaust opacity in direct gear up to 60 MPH under load. That's all. The cat must be present for a diesel built with a cat. These guys are not stupid and they know what the cat looks like (on the outside). Probably could not convince them that a muffler or resonator was a cat.

Rockyhud

So Rare1, in looking at your signature, I don't see any mention of exhaust changes which I'm presuming means you still have your cat intact and are still using the original system from turbo on back. Since my engine mods - 10 plate, 3K gsk - and the fact that it has the same 215 pump makes ours very similar, have you experienced any EGT problems with your setup? If not it makes me wonder if maybe just changing the muffler to a more free-flowing design might be enough to deal with EGTs that might otherwise get a little high under towing loads and a little hot-rodding.

Steve

Tiny

Summit Racing has a 4" exhaust system for $300, give them a call.

Rare1

Rocky, yes I have the original pipe and cat, and a replacement low-restriction muffler (original muffler went noisy on a trip and had to get what was available). My #10 is not forward enough to overfuel beause I don't have my EGT gauge yet. I tend to do changes slowly and deliberately, maybe one item per year, so I can assess the results. BTW, I have the automatic so it's a 180 pump. I don't know what my EGT is but I've detected no problems. In general I drive like my grandmother, for economy and long life (and to avoid high EGT), and only 60-65 MPH with the camper/boat. The loaded truck will climb any interstate grade in overdrive and cruise control, so I have sufficient power now, but sometimes I slow down and use direct gear on a grade just to ease the engine. My current project is to get an EGT gauge and bump up the timing a little and then I can start to move the #10 and hopefully gain both power and economy. Eventually I want (1) better injectors, not more fuel but better design for more complete combustion and (2) 4" exhaust if and when they change the emmissions testing.

I'm not the typical guy here who spends a lot on bombs so he can spend more on fuel. My goal is efficiency, economy, and dependability. That's why I don't have a 24-V

Haulin_in_Dixie

duhhhh I guess I am doing it all wrong

Rare1

(said with a smile and great respect) No Haulin, you appear to be doing it all right, but it's not easy to get to where you are with a 24v is it? Overall economy
has to include the path taken to the desired power level, dependability approaching 100%, and good milage. A 12v CTD was the logical starting place to reach my goals.

Forrest Nearing

gut the cat and tighten the snot out of the AFC come inspection time

Forrest

Rockyhud

Thanks for the feedback guys. As usual it's all been well worth reading and has provided me several thoughts on how to deal with my exhausting questions.

Rare1, it sounds like you and I are much alike in how we approach things with respect to mods like I'm working on here. It also sounds like we tend to drive our trucks very similarly. I like the extra power - who wouldn't - but I do tend to drive it somewhat conservatively as far as not trying to be the first one out in front after a traffic signal changes to green or passing someone just cause I can, although the extra power has come in handy several times when needing to pass some slow-poke on a 2-lane hi-way around here. BTW, do you have any details on the low-restriction replacement muffler you installed, such as what brand, cost, is it much or any louder than the OEM unit? I may want to go that route too.

One other thought crossed my mind on this topic that I don't recall reading anyone has ever done or tried and that is to open up the inlet and outlet of the OEM cat and weld 4" pipe to it so it can be used with a 4" system. I have an oxy-acetylene torch, as well as Sawz-all, I could use to cut the cat and a mig welder (in storage at this time) that I could use to weld up the new in/outlet pipes. That way, if it worked out, I could continue to be in compliance with emissions inspections and still run a 4" system. I think the inlet wouldn't be too difficult to do but I haven't looked at the outlet recently to see if it's feasible on that end. I've done some sheet metal replacement on our CJ-7 body and did a pretty decent job on the thin stuff, if I say so myself, so I'm not afraid to try welding to the cat. Any thoughts on this idea?

Forrest, when you say tighten the snot out of the AFC, can you give me some more details on what you're suggesting? When I installed the newly ground fuel plate I put it in the same position as before but I did slide the AFC housing a little forward, not much but some, and I didn't do anything to the starwheel. I get some smoke at low RPMs when I step on it harder than usual but it clears up to a haze fairly quickly. Should I slide it back toward the firewall for inspections? Should I turn the starwheel and if so, how much and which direction?

Thanks again for all you help. It's all very much appreciated.

Steve

BoostdCTD

Yea, there are quite a few around here with a cat like that for their test only setup.

Moving the housing is the huge adjustment, the starwheel is just a fine tune.