My first diesel, it's a 92 Auto with OD and 4x4. I'm trying to get a list of the tunning up the last owner did. Decent on speed, but I wish fuel mileage was better. I have't been able to go on a trip yet to get a good MPG yet but city driving seems to get around 250 miles per tank, and it is a SMALL tank, I think only 19 gal or something. Maybe the gauge is lying to me. Anyways I'm trying to find answers to questions that I have been coming up with. 1. Where should my boost and EGT be around when just driving on the interstate around 70 with no load besides the 35's on it? 2. I have a straight-pipe stock exhaust with no muffler, how much help would a 4" Magnaflow or Flowmaster exhaust help? How much does having a muffler in the system hurt performance, I hear the tickets for no muffler are spendy? Thanks for your help!
Your tank is much bigger than 19 gallons. Later trucks have 35 gallon tanks, I'd imagine yours is close to the same size. If you are going 250 miles on 19 gallons, thats about 13mpg. Not too good, but close if you are hotrodding around a fair amount. Boost should be low, 4-8 lbs I would say. EGT's are probably between 500 and 700*. Mine runs around 600*. A Flowmaster system will likely hinder performance. They are a joke. I was interested in their system before I knew anything about diesel pickups, but was plenty aware that a diesel needs a different type of muffler for the most part, if it's going to actually be a performance muffler. They use a 50 series gas engine muffler that happens to come in an optional 4" inlet/outlet. When I called their tech support and asked them about this, their employee that is supposed to know exhaust, "informed" me that exhaust is exhaust, regardless if it's gas or diesel and it doesn't really matter. I promptly said that no thanks and will never bother with another Flowmaster product for a diesel. They need to stick to gas.:stir: I wouldn't mess with Magnaflow either. Most of the exhaust systems out there are nearly the same, if not identical. Why pay more money for the name? Diamond Eye and MBRP have some good prices. Your mufflerless setup is just fine. Diesels don't even want back pressure. It likes the missing muffler. I wouldn't bother with a different system unless you want a deeper tone and if the drone is bothering you inside.
I'll have to do more research on my tank, but the MPG do suck if the tank is that big! I have been filling it back up when the guage hits before 1/4 tank and haven't wanted to push it to see when it actually runs out, heard that was expensive to fix when you do run it empty! Thanks for the advice on the mufflers and exhaust, I was looking at the diesel systems that I saw advertised in the Diesel Power magazine... I'm running about 800 on the EGT and about ten on the boost. The guy I bought it from says he switched out the exhaust housing to the 16 cm from the stock 21 cm to get better out of the hole power...maybe I should take it to Baker's for the exhaust, injectors, and have him set it all right! Said it would be around $1000....
The first gen 6BT's did have either an 18 or 21cm housing. The 12 didnt come to play until the 94's. The 16 is a great all around size for performance & overall driveability. Going with an aftermarket exhaust will just get the EGT's down unless you are trying for 400+ hp. Advancing the timing a smidge can also help the mpg's.
Thanks for your help fellas, I'll keep you informed on what I do with it. Just got married so I can't pump a lot of money into it right away...
I hope Ya'll don't mind a minor thread hi-jack ? I am interested in using a 12CM housing on my Blazer project and need to know what applications came with them ??? I should have a 21CM housing on my 93 VE pump donor motor and need to gather up the parts to convert to a smaller 12 CM housing . Any help/info that you can provide will be greatle appreciated ! Thanks , Tom
The 12's came on the 94-98 12 valve, and most 98.5-02 24 valves. Although, some 24V's had an HY35 with a 9cm housing, which would be a good one for a performance 4BT(3.9). You can pick up a 12cm housing for pretty cheap. It's also a wategated housing.
Mpg Bump up the timeing and add a lil more fuel through the pump and have the valvues adjusted. You will be amazed at the difference in power, black smoke and MPG after ya quit romping on it. I still mniss my 93 5-speed 350 duel wheel with 3;54 that would get 25 mpg on 2 lanes and 22 on 4 lanes if I kept to the speed limit. My 03 don't get near as good MPG. The values need to tightned up every 50,000 miles.
since it is an auto make sure it is shifting into overdrive. The sensors can be problematic (potentiometer on top of the injection pump) and keep them in drive. That could explain your poor milleage. The general tune up list includes: Check lift pump pressure change fuel filter make sure throttle is getting full travel Check the charge air system for leaks in boots and intercooler, don't forget the o-ring at the elbow on the TC and the intake bolts. Andy
