Subliminal
02-06-2010, 12:54 PM
Hey guys,
As you probably know (from the 6 or so posts on this page), I bought this guy a few months ago:
http://lh6.ggpht.com/_pjO6j2IMXk8/SxwZPdqcotI/AAAAAAAAIiI/76XSn-55_OU/s800/IMG_6633.JPG
It's a good, solid truck, but at factory settings, kind of sluggish. I mean, a powerhouse for sure, but just normally getting up to speed and driving around...kind of sluggish.
Anyway, I've been doing some research, and have made a couple of mods to the truck and here's what I've found (so far):
The early 12v trucks are pretty much all mechanical. I mean, they have wires here and there, but not in great amounts.
The first thing you want to do before you mess around too much with the stock setup is invest in a few gauges:
Pyrometer
Boost Gauge
Once you have these, you can pretty much fiddle with whatever you want, so long as you watch that EGT level.
So, gauges installed, there are a few things to play with.
These trucks have a Bosch fuel pump, known as the VE pump. It looks a little like this:
http://lh3.ggpht.com/_pjO6j2IMXk8/S22ZLiEbeeI/AAAAAAAAI2I/MIKRPGSOQoY/s800/ve_pump_adjustments.jpg
When you open the hood, the pump is right there on the driver's side of the engine. Easy to get to, although some of the adjustments are a real PITA...just because they're underneath something or you have to do the ol' reach-around.
Going from the top of the diagram, the first thing pointed out is the 'Smoke Screw'. There is a cap here with a set screw underneath it. This is plumbed to the intake manifold and restricts the amount of fuel injected until the manifold pressure is above atmospheric. This is said to give you a little extra juice under normal driving conditions by screwing it in a little. Not much gain to be had here, and this will raise your EGT...but a half turn or so puts the butt a little further in the seat.
Next down is the 'full load fuel delivery' dealy. Basically, you take off the top cap and there is a diaphram mounted to a fuel pin, which has a 'cut' in it at the bottom. There are many aftermarket pins that can be had, and many people have had luck just grinding theirs down a bit. The easiest way to gain a little here is to pull the pin out, and turn it 90-120 degrees clockwise. This allows the fuel pin inside the pump to extend a little further than stock...giving you more fuel and then more boost and a little more fun.
On the back side of the pump is the 'Power Adjustment Screw'. This is where the REAL gains are to be had (at least the free ones). As noted in the diagram above, there is a steel collar tacked to the screw. Stock, without removing the cover, you might be able to get 1/4 turn on the screw before it bottoms out on the collar. I was, at any rate, and my max boost went from about 17PSI to about 20PSI. Of course, EGTs also climbed a bit, and with such a small turn, it really shows the importance of monitoring those temperatures.
Note: A moderator on another forum told me that you really need the gauges, even if you're just turning the pump up a tiny bit, as you never know the state of your injectors and you could be running high EGTs before even messing with anything, based on even one of the injectors being a little clogged up.
Another fun mod that can be done fairly simply and inexpensively is the '3200 RPM Spring', or the Bosch 366 spring, as it's known at the parts store. ;)
Basically, these trucks are set up to start defueling at about 2800 RPMs from the factory. The spring swap changes this up to 3200 RPM, but it also changes the fueling across the RPM range.
Changing the spring is a bit of a tedious endevour...you have to take the entire top of the pump off, and the spring connects to the lid and to the bottom of the pump, so fingers need to be in tight spots and parts need to be carefully caught before they drop into oblivion.
However, it is an hour or two job (at the most) and the benefits are easily felt...and the spring costs ~$20 shipped from various online vendors (including eBay). I think mine was $16 plus $2 shipping.
And while you have the cover off, it's easy to rip that collar off the power screw on the back of the pump.
I've messed with the above set screws and springs, and I can tell you, the truck is like a totally different animal. Before messing with stuff, the truck had enough power to get out of its way, but to keep up with traffic leaving a red light, the pedal really had to be mashed. Now, I can get to 15 PSI with very little throttle and with the mild increase on the power screw, I top out at about 23 PSI.
As far as mileage, I'll have to edit this post in a few weeks. I've been getting ~ 15 MPG, entirely city (12 miles stop and go to work and back, and 12 miles stop and go to the gym and back). I fear the truck is so much more fun to push now, that It'll probably take a few tanks to get a true, average MPG...but I'll do my best...after all, fuel is expensive.
Please note, I did a lot of reading around before I messed with any of this. There are quite a few good diesel information sites out there, and there are many great walk-thrus on making any of these changes. I read through as many as I could find to see the various ways people tackle each of these things before I dove into my own. I would suggest that you do the same.
As you probably know (from the 6 or so posts on this page), I bought this guy a few months ago:
http://lh6.ggpht.com/_pjO6j2IMXk8/SxwZPdqcotI/AAAAAAAAIiI/76XSn-55_OU/s800/IMG_6633.JPG
It's a good, solid truck, but at factory settings, kind of sluggish. I mean, a powerhouse for sure, but just normally getting up to speed and driving around...kind of sluggish.
Anyway, I've been doing some research, and have made a couple of mods to the truck and here's what I've found (so far):
The early 12v trucks are pretty much all mechanical. I mean, they have wires here and there, but not in great amounts.
The first thing you want to do before you mess around too much with the stock setup is invest in a few gauges:
Pyrometer
Boost Gauge
Once you have these, you can pretty much fiddle with whatever you want, so long as you watch that EGT level.
So, gauges installed, there are a few things to play with.
These trucks have a Bosch fuel pump, known as the VE pump. It looks a little like this:
http://lh3.ggpht.com/_pjO6j2IMXk8/S22ZLiEbeeI/AAAAAAAAI2I/MIKRPGSOQoY/s800/ve_pump_adjustments.jpg
When you open the hood, the pump is right there on the driver's side of the engine. Easy to get to, although some of the adjustments are a real PITA...just because they're underneath something or you have to do the ol' reach-around.
Going from the top of the diagram, the first thing pointed out is the 'Smoke Screw'. There is a cap here with a set screw underneath it. This is plumbed to the intake manifold and restricts the amount of fuel injected until the manifold pressure is above atmospheric. This is said to give you a little extra juice under normal driving conditions by screwing it in a little. Not much gain to be had here, and this will raise your EGT...but a half turn or so puts the butt a little further in the seat.
Next down is the 'full load fuel delivery' dealy. Basically, you take off the top cap and there is a diaphram mounted to a fuel pin, which has a 'cut' in it at the bottom. There are many aftermarket pins that can be had, and many people have had luck just grinding theirs down a bit. The easiest way to gain a little here is to pull the pin out, and turn it 90-120 degrees clockwise. This allows the fuel pin inside the pump to extend a little further than stock...giving you more fuel and then more boost and a little more fun.
On the back side of the pump is the 'Power Adjustment Screw'. This is where the REAL gains are to be had (at least the free ones). As noted in the diagram above, there is a steel collar tacked to the screw. Stock, without removing the cover, you might be able to get 1/4 turn on the screw before it bottoms out on the collar. I was, at any rate, and my max boost went from about 17PSI to about 20PSI. Of course, EGTs also climbed a bit, and with such a small turn, it really shows the importance of monitoring those temperatures.
Note: A moderator on another forum told me that you really need the gauges, even if you're just turning the pump up a tiny bit, as you never know the state of your injectors and you could be running high EGTs before even messing with anything, based on even one of the injectors being a little clogged up.
Another fun mod that can be done fairly simply and inexpensively is the '3200 RPM Spring', or the Bosch 366 spring, as it's known at the parts store. ;)
Basically, these trucks are set up to start defueling at about 2800 RPMs from the factory. The spring swap changes this up to 3200 RPM, but it also changes the fueling across the RPM range.
Changing the spring is a bit of a tedious endevour...you have to take the entire top of the pump off, and the spring connects to the lid and to the bottom of the pump, so fingers need to be in tight spots and parts need to be carefully caught before they drop into oblivion.
However, it is an hour or two job (at the most) and the benefits are easily felt...and the spring costs ~$20 shipped from various online vendors (including eBay). I think mine was $16 plus $2 shipping.
And while you have the cover off, it's easy to rip that collar off the power screw on the back of the pump.
I've messed with the above set screws and springs, and I can tell you, the truck is like a totally different animal. Before messing with stuff, the truck had enough power to get out of its way, but to keep up with traffic leaving a red light, the pedal really had to be mashed. Now, I can get to 15 PSI with very little throttle and with the mild increase on the power screw, I top out at about 23 PSI.
As far as mileage, I'll have to edit this post in a few weeks. I've been getting ~ 15 MPG, entirely city (12 miles stop and go to work and back, and 12 miles stop and go to the gym and back). I fear the truck is so much more fun to push now, that It'll probably take a few tanks to get a true, average MPG...but I'll do my best...after all, fuel is expensive.
Please note, I did a lot of reading around before I messed with any of this. There are quite a few good diesel information sites out there, and there are many great walk-thrus on making any of these changes. I read through as many as I could find to see the various ways people tackle each of these things before I dove into my own. I would suggest that you do the same.