I get asked alot so I think I'll share what I know from my experience and others before us who posted back when.

The one that made the largest change was switching to E85 fuel. But of course many of my previous mods supported it. All of the others were just small gains that added up. The Volant with a home made fresh air duct is worth quite a bit. The Volant has a hook up on the bottom of the box for a 4 5/8 air duct. I bought two 36"ers from the auto parts and route fresh air from in front of my radiator in the bumper to it. Once my ducts came apart and I lost the cold high pressure air on a trip. I thought I was having engine trouble the power loss was so great. The plugs in my sig at 0.45"-0.050" gap will work as described in the easy mods post #100. If you have a return fuel system (it has a replacable fuel filter) made from '01 through ('03-I believe) you can use the factory adjustable fuel pressure regulator to bump the PSI a few pounds. It helps due to the 15% alcohol they blend into gasoline now dilluting it more than your PCM was calibrated for. The 8.1 (and moreso the 6.0) is quick to knock when the throttle is opened fast because of this. The extra PSI increases fuel delivery at WOT thereby maintaining a better and safer air/fuel ratio for performance. The O2 sensors maintain the part throttle ratio so mileage effect is minimal unless you are always WOT. We discussed this in detail a while back so you can search it for more info.

If you want the biggest gains on the 8.1 install PCM programming that allows the removal of torque managment and install a aftermarket camshaft in the engine. Comp has 6 grinds in thier catalog from mild to modest. Crane has about 5 more from modest to wild. You have to look for them but they are there, even online.
The only bolt on that will beat those two is a supercharger and it costs more.
Search through posts on www.performancetrucks.net (http://www.performancetrucks.net) by 8100Hammer, Whippled496, and TieRod.

There's no need for the marine injectors unless you're going to install a forced induction or run alcohol.
Vernon

Thanks Vernon!

Already did sparkplug gapping but can you please eloborate a little more on the fuel pressure tip. Such as where it is, how you know how much to turn up, ect.. I can definetly say the biggest increase I have felt is the K&N FIPK. Im also in the works with getting a EFI Live tune with a local fella around town (Columbus, Ohio). Correct me if Im wrong but Im pretty sure these engines are very "corked" up from the factory. I think its not to compete with the diesels so they get their $8000 markup. :)

I too would like to know more about this fuel pressure adjustment. I just did the plug gap and wires and notices a little more response in her. Next move will be the custom tune, after that I will have to open the motor up (cam) to get any more.

I remember it being discussed here but I can't find it either so try this:
http://www.gm-trucks.com/forums/index.php?showtopic=39982

Vernon

Vernon,
Okay, I read that link and have some questions. On an 8.1 do you need to boost fuel pressure, or lower it? The 6.0 looks like it needs more pressure. Is that the case? What tools do you need to check this?
Thanks.

Duromax04, at the time I wrote that post I was more concerned with getting the highest MPG I could out of the truck. Since my long term fuel trim averages showed I was running rich I hoped I could gain some mileage by reducing the pressure. I dropped it until my trims stayed around zero but it created too much knock and spark timing retard thereby reducing stop and go mileage. Also there wasn't any significant effect on highway MPG. The O2 sensors are the main MPG factor. I think I edited that post at the end later.

The fuel rail is the metal plumbing that runs a loop around the upper intake and sits on top of each fuel injector. If you have a early style return system like discussed it has a fuel inlet line coming from the pump and a return line starting at the fuel pressure regulator on the LH side of the rail and going back to the tank at the LH rear. Any fuel in excess of maintaining the set pressure goes through the regulator into the return line and back to the tank. If you remove your engines decorative cover (mines been in the shed since the 2nd week) and look on the RH side of the fuel rail you'll find a fitting with a black plastic screw on cap like an HVAC freon fitting or a double sized tire air valve. Under the cap is a schrader valve that commonly availiable fuel pressure gauges can attach to and read the rail's internal fuel pressure. You may have to goto a mechanics tool supplyer to find one or perhaps "rent" one from an auto supply.

Here's something to take note of: On return style fuel systems like these fuel pressure is a maintained setting above intake manifold internal air pressure and constantly varies to maintain the same difference. When the engine is off the air pressure inside the intake is the same as ambient. When the engine is running with the throttle shut the air pressure inside the intake is lower than outside, this is vacuum. When the engine is running and the throttle is open the air pressure inside the intake will be as high as possible within the variables of engine speed, air intake design, throttle size, cylinder head flow, and camshaft design, etc. If you look closely at the fuel pressure regulator on the LH side of the fuel rail you'll notice a small vacuum line attaching it to a nipple on the intake manifold itself. This is the internal intake vacuum reference that acts upon the regulator diaphram to maintain the set pressure difference betweel the fuel coming out of the injectors and the air pressure they discharge into. In other words the regulator drops fuel pressure when the injectors are shooting into a vacuum and raises it when not to keep up with the higher pressure in the manifold working against them. This way fuel flow is always consistant to injector opening time (pulse).

When checking or setting fuel pressure we are concerned with the fuel pressure above ambient with the pump running. The easiest way to do this is to hook up a gauge then with the engine running disconnect the vacuum line between the intake manifold and fuel pressure regulator. The regulator diaphram will see ambient air pressure and raise the fuel PSI to match. With the pump running and the engine idleing the regulator will be sending back excess fuel. Now using the special tool bit twist slowly clockwise to raise pressure and counter clockwise to lower it. It would be wise to get some good penetrating oil like Penetrating Blaster and spray the screw and internals(through the vacuum fitting) of the regulator ahead of time as they are usually stiff and have a drop of threadlocker applied when new. With a good tight bit fit and turning in a twisting motion only start applying pressure and keep increasing until it finnally pops loose. After that it should turn easily but never be loose. If somebody should happen to strip it (not likely if you're careful), it's not the end of the world they are readily availible and easier to replace than adjust.

The thing to do to increase performance output of these engines would be to increase the PSI a little to compensate for the leaning out of 15% ethanol mixed into gasoline now. I like to run back to back WOT runs from 20 upto 60-70 MPH, increasing fuel pressure a little twist at a time until it no longer helps then go back a step where it was best without excess pressure. It's usually near 5-7 PSI but that's not a universal figure, every tune, MAF, brand, of fuel, etc. are different. Don't be lazy as it probably won't work as well.

The stock setting is 55-62 PSI above ambient in case you loose track and need to start over. Sometimes if yours is on the low side going upto the highest spec makes all the difference.

Let me know I something isn't clear and I'll explain it better. I know it seems complicated but after a while of thinking about it and working with it things all become clear.

Vernon

Am I missing something? I didn't think 8.1's could run E85??

Am I missing something? I didn't think 8.1's could run E85??

Did you miss the part where I'm a automotive technical genious? :p: jk

The fuel system doesn't know what type of fuel is in it, only if it is rich or lean, misfiring, etc. E85 is about 25% leaner air/fuel wise than current pump Gasoline. I've installed 8.1 Marine Engine fuel injectors that flow more gallons per hour at the same pressure than the automotive 8.1 fuel injectors. That and some fine tuning of the fuel pressure as just described got my target air/fuel ratios are within tolerances and maintained by the PCM. I split the difference on fuel trims so I can run E85 or Gasoline without setting a check engine light or any long term driveability issues. Since there isn't a sensor in the tank or programming to go along with it when switching fuels (if I did again) it takes a few minutes for the PCM to recalibrate fuel trims. It does this with the O2 sensors. With the marine injectors at the proper pressure, E85 the PCM sees as lean, and Gas the PCM sees as rich. The octane and cooling effect with E85 is so great that I get zero knock retard on it even though fuel trims are lean. Gas likes to be rich anyways so that's not a problem. I CAN'T just switch back and forth and drive off at WOT or expect it to idle smootly when pulling away from the gas pumps BUT when given time (less than a minute at warm idle) and driven gingerly for the first 5 miles it does fine. I haven't ran Gasoline since the day I switched to E85 though, about 3-4 months ago at least. I did monitor what was happening with a scan tool when I did it. That helps set the proper fuel pressure so it's an even split between lean and rich limits.

Most people are scared of E85 because "alcohol" has a reputation of being extremely corrosive and that it will destroy the fuel system unless it's made of different materials. Well Ethanol, and Methanol are two different alcohols and have very different properties. Ethanol is fine, Methanol or Top Fuel dragster fuel is harsh. Do some reasearch and you'll see modern fuel systems are more than capabile of running Ethanol. To avoid any liability issues nobody who manufactures is going to tell you that (and I don't blame them) but it's being done by me and a lot of others all around the world where E85 is availible. I woudn't put it into an older car without reasearching it though.

Vernon

Go to you tube,and type in....tierodkll...thats "KLL" not kill,That guy has 1 hell of a modded 2001 chevy 8.1.beats a ford lighting.

He had it, it's the truck that's burning down in his avatar on this site (TieRod). He still has the engine though and will eventually get another 8.1 truck to start over with.

Vernon

We might someday ALL be stuck with using E85..:(

But, in the meantime, I will not use it. Not even in
my lawn tractor..ya gotta get out onto the Marine
Website Groups and see what the hi-dollar boat guys
are saying about alcohol-blended fuels....
JMHO!!

Steady Eddie
from where fuel
draws moisture...

At least E85 is made here and not by people who want to kill us. I will run it every chance I get to help support the people who produce it here in the US. Besides, all gas is blended with some alcohol in it now.

Thanks Vernon for all your insight.

"...At least E85 is made here and not by people who want to kill us...." I don't know that..I buy real gasoline from Shell, Texaco, and Chevron, all are called "Top Tier" Producers. The little blonde that works at our closest
Chevron dealer, now, she IS killer, though...:D

"...I will run it every chance I get to help support the people who produce it here in the US..." Yes, but at what cost to your wallet and your rig?

"...Besides, all gas is blended with some alcohol in it now..." Not in my state. If the fuel has alcohol in it,
our state laws say it must be tagged at the pump as
an alcohol blended fuel. Also, the manager or attendant
is required by law to tell you if the fuel they sell has
any alcohol in it. You can still buy the 10% alcohol blend. And it is the only alcohol-added fuel that GM
says I can use. But I use 100% pure gasoline..:cool:

Steady Eddie
1998 Chevy P12
L21 Vortec 7400
Allison
4.78 rear 13,500# axle

Eddie it seems a growing trend that most of what I mention does not applie to you. If so at least you're intelligent enough to know it so I don't mislead you but for many of us it's a reality we deal with. See this page from the Federal Government: http://www.eere.energy.gov/cleancities/blends/ethanol.html

Also, how is E85 hurting my rig? Any moisture that gets into my fuel system is quickly absorbed by the fuel and sent out the tailpipe as steam. Unlike with gas where it just collects in the low spots causing corrosion. And I've done the math, with the difference in costs and efficiency it hurts my pocketbook about 10-11 dollars a week. I relize I haven't made a post here proclaiming all the benefits in performance and comfort I'm getting on E85 but lets just say it's worth it to me considering my driving style and traffic conditions.

I'll list some of my E85 benefits just so it's not a mystery:

Torque was increased by about 20 lbs./ft. across the entire engine range, from idle to redline. It's effect on horsepower is mathmatical. It's very congested around here and some people drive aggressively slow if you know what I mean. It's nice to have all the power I need to pass in tight spots even though they also go WOT as soon as I do. It's like I installed a supercharger at all times. Downshifting to muscle through cut-throat traffic on the multi-lane Houston highways is no longer as necessary resulting in increased passenger comfort and less anxiety. I have no knock and it's associated timing retard.

The engine and transmission run significantly cooler at all times. The air conditioning system is a lot more effective in the Texas heat. Less underhood temperature and associated effects.

I no longer have residual fuel build up on my electronic throttle body that was so bad on gas I had to clean it every few months to maintain a smooth and strong idle. Nothing was more fustraiting than trying to back up a hill with an automatic gate behind me when everytime I got it up and put it into gear the engine stalled. By the time I got it restarted the gate would come back down. Regular stalling and surging idle was common. Since E85 it idles like a sewing machine without maintainence.

Exhaust noise was cut by 50% at least, inside you can barely tell it's running unless you're giving heavy throttle and then it's like a stock exhaust sound level even though I have a free flowing muffler. I've actually tried to start it running, that would have been impossible on Gasoline. I don't P.O. the nieghborhood when coming or going. At WOT and 115 MPH it sounds like somebodys running a table saw on the next block. Pulling a load is obviously easier.

The exhaust smells like Margaritas, lol.

I'm polluting like, not at all. Emmissions testing is commical to say the least.

My fuel system, internal engine, and exhaust system look brand new clean. No carbon build up for me. Even the tail pipes are steam cleaned. The oil comes out after 4,300 or so miles (I think more now, the computer monitors engine parameters) looking cleaner. Fuel injector cleanings are no longer necessary as they stay spotless. I did go through a few filters as the alcohol removed all the crud that gas had left over the years.

I'm not burning foreign oil to the tune of 10 MPG. And by being a consumer I'm helping to establish a customer base for E85 in my area. I've yet to see anyone else use the E85 nozzles though I recieved several puzzled looks. Most people who would use it don't realize it's there. But the $2.27 a gallon for corn cob sign probably gets more puzzled looks. lol

Cons:

Fuel efficiency goes down on a designed for gas engine and therefore costs go up. The small fuel tank becomes an even worse PITA.

It's not readily availible and you have to print out maps of where to find it when traveling around Texas although in other areas like the Mid-West it's common place.

In colder climates (not here) there could be some cold start issues on a mechanically adapted set up like mine where there's no programming changes.

The torque management eventually caught on and reduced 1st and early 2nd gear performance to near what it was before. It's still better though and after it's moving on it never lets up.

Vernon

Vernon--:)

You are right on all points mentioned.

Alcohol blended fuels just won't work in a moist climate
under the conditions of long term storage. Also, I am
worried about the GM plastic fuel lines and the GM
(mostly) plastic fuel pump. As well as any O-rings and
rubber-like parts in the fuel system.

Steady Eddie

I went over the fuel pressure adjustments a few months ago... My FP regulator adjustment screw was pretty tight... so I removed the snap ring and top cover to get it on the workbench. I got it freed-up in a few minutes and back on the truck in no time.

I've run my pressure at both ends of the spectrum... I had it up to 62psi and it ran like a beast.... but fuel economy was horrible as a result.
At 62psi, 8.3-8.5mpg was the average.
At 55psi, it ran "OK" but was noticeably more lazy...and felt like it went flat at higher RPM's.
Didn't check fuel economy at 55psi... but it was definitely better.

I've since gotten a tuned PCM from Nelson Performance, and set fuel pressure at 58psi.

It still runs like a beast, and now gets 12.5mpg around town and 13.9mpg on the highway.

Can you adjust the FP in our trucks as they sit, or do you have to buy an aftermarket fuel pressure reg.???

If it's a return style fuel system it's adjustable as is. Return style have the replaceable fuel filter under the cab.

Vernon

Yes, it's adjustable "as-is" but may take a bit of effort and a special torx driver with a hole in the center. I just used a standard torx driver and snapped the center "tit" off the adjustment screw.

With the engine running and vacuum line off, set the fuel pressure where you want it.
The fuel pressure will drop when the vac line is put back on. (this is normal)