Technical Articles
Transmission Coolers
Why do you need an external transmission cooler? Many "performance" websites these days are telling everyone it is unnecessary to run an external transmission cooler. Their reasoning for this is the assumption that external coolers are a source for leaks. If installed incorrectly and with inferior hardware, this can be true. However, none of these websites bother to state the benefits of having a transmission fluid cooler on your vehicle.
Transmission builders and aftermarket part manufacturers have known for years the benefits of maintaining "lower" transmission fluid operating temps. Automatic trans fluid temps in most cars and trucks run between 195° F and 230° F. Most aftermarket builders agree that 170° F - 180° F is preferred for the best balance of durability, consistency, and performance. You also don't want your transmission fluid temps too cold because at those lower temps, problems with consistency and lubrication can result. Of course higher temps can cause fluid breakdown and eventually transmission failure.
When do you need an external transmission fluid cooler? Well we all know that if you are doing any towing you should have one. But if you have increased the performance of your engine or installed a higher stall torque converter, it would be a good idea to have a cooler. Even when using a stock torque converter, increased engine power output will cause the stock torque converter to stall higher which heats the fluid more than normal. Most aftermarket converters stall higher which in itself, causes higher fluid temperatures due to the increased fluid sheer forces and pressures in within the torque converter.
So how do you install one on your vehicle to insure against leaks? Very Simple. First, use only the correct size and type hose for the size fittings or lines you are working with. DO NOT USE FUEL HOSE. Transmission fluid specific hose is rated for the pressure and chemical properties of transmission fluid. I also recommend using high-quality clamps, the type that use a fine-threaded bolt and nut to tighten them with. If you can not find these high-quality clamps, you can use the cheaper design screw/slotted band type clamps. MAKE SURE you check and re-tighten all clamps as the seasons change. Wild temperature swings can cause the hoses to shrink/expand which can lead to leaks. Also if you have to cut the OEM metal trans cooler lines in order to accommodate the trans cooler hose connections, it would be a wise practice to put a slight barb on the end of those metal lines using a flaring/barbing tool so the hose cannot blow off of it when properly clamped. Most brake line flaring tools do the trick and are cheap and easy to find.
Fuel Pumps
Like the transmission cooler, the fuel pump seems to be a hotly contested topic. Here again there are many opinions out there about what pump is needed for a particular application. Many of the opinions that tend to surface on the various automotive message boards seem to suggest that OE-replacement pumps designed for a specific application can be used in other, higher-performance applications. In some cases, this may be true. But you need to understand how the typical fuel injected electric fuel pump works so you don't potentially put your engine's health at risk.
The typical electric fuel pump puts out a specific flow rate (volume) at a specific pressure level (PSI), assuming it gets all the electrical power (amps + voltage) it needs to do the job. Most, if not all electric pumps decrease volume of output when pressure increases. Below is a chart constructed using flow test data from an AC Delco EP376 fuel pump calculated to show how much crank horsepower this pump will support...
In the above chart, you will notice two lines. The blue line (top) represents the amount of Crank Horsepower the EP376 pump will support on a naturally aspirated engine that consumes 0.50 lbs of fuel per HP it makes (also known as Brake Specific Fuel Consumption, or BSFC). The EP376 fuel pump was used on the Corvette LT1 V8 engine, and this engine had a maximum rated fuel pressure of 47psi. As you can see in the above chart, this pump is quite capable of supporting over 400hp on a naturally aspirated engine operating at less than 50psi of fuel pressure. Based on this data, it is reasonable to assume that the 300hp LT1 V8 Vette engine was in no danger of exceeding the flow capacity of this pump at the fuel pressures it operates at.
Supercharged and turbocharged engines consume more fuel per HP they produce compared to naturally aspirated engines. The accepted "industry standard" for fuel consumption of these types of engines is 0.65 lbs of fuel per HP produced (BSFC=0.65). This data is represented in the red (bottom) line in the above chart. As you can clearly see, the EP376 fuel pump cannot support nearly as much horsepower on a super/turbocharged engine as it could on a naturally aspirated engine because of the increased fuel demands of the boosted engine per HP made. To further complicate matters, super/turbocharged engines typically run higher fuel pressures in order to overcome manifold boost pressure to maintain a consistent flow rate of the injectors (the 3800 Series II SC engine's fuel pressure is 60psi at 10psi of manifold boost pressure). As demonstrated in the above chart, the EP376 fuel pump cannot even support 300 crank HP when fuel pressures rise to 60psi or beyond.
Furthermore, stock OE-replacement pumps meant for naturally aspirated duty are usually not designed to operate at the higher pressures found in SC/turbo applications. Asking a pump like the EP376 to work in an environment with consistently higher pressures than what it was designed for is asking it to work harder than it was ever meant to. So the question is how long will it last? Well that depends on the quality of it's construction and the quality of the components used in it.
So what pump should you use? Well, you should use a fuel pump that is capable of supplying enough fuel volume at the pressure your application demands. Personally, I like to have a little bit of a safety net when it comes to things like this so I make sure I will never exceed the capabilities of my fuel pump. Enter the Walbro Fuel Pumps.
WALBRO makes several different models of pumps, some are re-badged and sold under other brand names such as Holley or even some OE-replacement units. Keeping on topic of this tech article, we are only concerned about the aftermarket high performance models. Of these, Walbro makes 4 high performance models: 190 lph (liters per hour), 190 lph-high pressure, 255lph, and 255lph-high pressure. Typically, the high pressure pumps are designed for use in forced induction applications where higher pressures are required of the fuel system. (The 255lpr walbro pumps will support over 550 crank HP on a turbo/supercharged engine @ 60psi of pressure.) Walbro offers several different designs of these pumps made for various vehicle applications. Below is a list of vendors who sell the Walbro line:
www.autoperformanceengineering.com
www.fullthrottlespeed.com
www.precisionturbo.net
If you are going to install one of these high-performance fuel pumps into your car, and your car still has the factory fuel pump wiring, then I also recommend either upgrading your vehicle's fuel pump wiring circuit or installing a "hot-wire" kit. (see below)
Hot Wire Fuel Pump Kits
What are "hot wire" fuel pump kits? A hot-wire kit is a wiring kit that routes power to the fuel pump from the highest voltage/amperage power source on the vehicle -- the alternator B+ terminal. When is a hot-wire kit required? Hot wire kits are required primarily in applications where high fuel pressures or stronger fuel pumps are required or installed. Higher fuel pressures than stock put a higher electrical load on the vehicle's fuel pump electrical circuit. Higher performance aftermarket fuel pumps typically require more current (amperage) to operate at peak performance. Most OEM vehicle fuel pump wiring circuits are insufficient for the task. The hot wire method of getting higher current and voltage to the fuel pump usually involves running a larger than OEM gauge fuel pump power wire directly from the alternator's B+ terminal, thru a properly rated fuse, back to the fuel tank where an additional relay is attached to the chassis and is activated by the vehicle's OEM fuel pump wiring circuit. When installing a hot wire kit, special care must be taken to protect the wiring from moving and hot parts, as well as road debris and pinching from vehicle frame movement. www.casperselectronics.com sells a hot-wire fuel pump kit for most popular vehicles or you can build one yourself from parts that can be purchased from any automotive parts store. If you have higher than stock fuel pressure or have installed a high-performance aftermarket fuel pump but have not upgraded the vehicle's fuel pump wiring circuit; chances are your modifications are putting great strain on the vehicle's fuel pump wiring circuit and starving your fuel pump of much needed current and voltage which can result in insufficient volume of flow and pressure output. Instructions on how to perform the "Hot Wire" upgrade on Fieros can be found here.
Which FWD Transmission Should You Use?
This topic applies to those who are contemplating engine swaps using automatic transmissions with overdrive. If you are interested in going with a non-electronic version, you have two choices: 440-T4 and 4T60. The 440-T4 was introduced around the mid 80's and had many changes and upgrades during its lifetime. In the early 90's, its name changed to 4T60 but its use was discontinued before the 1993 model year. Basically, the 4T60 contains all of the updates, upgrades, and fixes for problems that plagued the early 440-T4's. If you decide to go with a 440-T4 because of availability or price, I suggest you get the newest one you can. The 440-T4 and 4T60 are stronger than the 125-C 3-speed auto but slightly weaker than the 4T60-E.
If you plan on using an electronic OD automatic trans, then you have a couple of choices: 4T60-E or 4T65-E. The 4T60-E transmission was pressed into service in 1991 and was used until 1999. There was a Heavy-Duty version that was available ONLY in 1996 that came attached to 3800 Series II Supercharged (L67) engines. The 4T60-E transmissions will work with EITHER an OBDI or OBDII computer system, however they use a vacuum modulator to control line pressure. In my opinion, this feature is an advantage over the 4T65-E transmission when used in conjunction with turbocharged engines because the modulator can more accurately compensate for engine load based on what it senses from boost/vacuum of the intake manifold. The non-HD versions are slightly weaker than the HD versions of both the 4T60-E and 4T65-E but many people including myself have been using the regular 4T60-E's in high-HP applications without any failures. However, these transmissions are getting older and there are less and less people who are competent in building these up, so it might be easier to just go with a 4T65-E given the choice.
The 4T65-E came in two versions: HD and non-HD. The 4T65-E HD transmission is rated as the strongest 4-speed FWD transmission GM makes next to the Cadillac 4T80-E. However, the 4T65-E's had their share of issues as well. They rely on a computer controlled pressure solenoid to control line pressure. Some people have reported failures of this component which can lead to transmission burnup if not replaced immediately. There is one more thing to watch out for when using these transmissions; some years allegedly used an input shaft that was machined different than other years which actually made them weaker. I don't have exact info on this but I do know this issue doesn't seem to affect the 4T60-E transmissions. The 4T65-E transmissions also use a dual-chain drive which is weaker than the single, larger drive chain used in the 4T60-E's. But aftermarket conversion kits are available to upgrade to the stronger, single chain.
OBD1 or OBD2???
This discussion has come up quite a bit on the internet about which type of computer system you should run. Speaking about 3800 computers, if you are running a 4T65-E transmission, you have no choice but to run an OBD2 computer. However, if you are running any non-electronic auto trans, manual trans, or the 4T60-E trans; you can use the OBD1 computer. Besides the transmission issue, does the OBD2 computer have any advantages over the OBD1 systems? In my opinion: not really. From a performance standpoint, either computer system is capable of being tuned to support almost any power level conceivable. OBD1 computers generally require less wiring to install and operate; and tuning software is much less expensive compared to OBD2 systems. Furthermore, most of the OBD2 tuning software that is currently available does not go into as much depth in programming as does the currently available OBD1 tuning software. Of course, as time goes on, further development of OBD2 tuning software should provide future updates and increased in-depth tuning support for the OBD2 systems (at least we hope). Some OBD1 computers do have a slight limitation pertaining to the Engine RPM rev limiter. In some applications (ex: 3800), this value cannot be set any higher than 6400 rpm by program design. However, it some cases it can be completely disabled if your application calls for higher Engine RPM capability.
Does the OBD1-type system offer any advantages over OBD2? At this point in time, the OBD1 type computers have a few advantages over the OBD2 systems besides less wiring and cheaper tuning software. One BIG advantage is that most OBD1 type computers have a removable chip...This means that you don't have to ship an entire computer off to get reprogrammed. Another advantage this provides is the fact that if you are having someone else doing your programming, in many instances you can just have them send you another chip/mem-cal all the while your car suffers no down-time. For those of you who are do-it-yourselfers, there are devices out called EMULATORS that, when used in conjunction with the appropriate software and PC/Laptop computer, allow you to make real-time tuning changes to the programming while the engine is running! This can be extremely useful for dyno/track tuning sessions. Currently, most OBD2 PCMs do NOT offer this type of real-time tuning support; (although it is becoming available thru companies like moates.net).
3800 Series II Flexplates and Flywheels
Another somewhat debated topic is: can you run a 3800 Series II naturally aspirated flywheel or flexplate on a 3800 Series II Supercharged engine? Well before I answer that question, let me point out that while a Series 1 n/a or SC flexplate might bolt up to a Series 2 engine, the balance is different so you shouldn't try using it, otherwise you will get some bad vibrations that could lead to engine failure.
The next question that you might ask is WHY would you need to run a naturally aspirated flexplate or flywheel on a supercharged engine anyway? Well, quite simply if you want to bolt the SC engine to an auto transmission other than what came stock with it, the torque converter bolt pattern in the SC flexplate may not work with it. Or if you want to put a supercharged engine into a car with a manual transmission, you have no choice but to use the 95-up 3800 Camaro/Firebird flywheel. For front-wheel-drive applications, you will need to have the flywheel milled down to the same thickness as the flywheel that originally came equipped with that transmission. However, it will need to be rebalanced to SC specifications, and here is why:
Notice the Supercharged flexplate has a LARGER counterweight when compared to the Naturally Aspirated unit. While the N/A flexplate will bolt to the SC crank, the engine will exhibit slight vibrations and might experience some premature bearing wear after prolonged use. For those of you who are using an auto transmission with the smaller torque converter bolt pattern, you will need to have the SC flexplate redrilled for use with the smaller torque converter bolt pattern. These flexplates are made of mild steel so you can drill them yourself with correct measuring or you can have someone do it for you. There are a few 3800 performance companies on the internet that will perform this service for a modest price. The harmonic balancers also have different counterweights between the L36 and L67 so make sure you use the balancer that matchs your rotating assembly!
EGR and EVAP Emissions Systems nonsense
I am sure by now everyone has heard from the old racer down the street that you need to yank all of that emissions "crap" off of your car because it hurts performance and does not have any benefits. Nothing could be further from the truth. First off, when functioning properly, both the EGR and EVAP systems are SHUT OFF at Wide Open Throttle. So exactly how are these systems degrading performance? The short answer is they don't hurt performance and removing them can cause annoying or damaging results.
The EVAP system is designed to recycle or burn unused gasoline vapors instead of allowing them to escape into the atmosphere from the fuel system. Gasoline fuels vaporize at room temperature. At higher temperatures, more gasoline vaporizes and can build high pressures and in greater concentrations. This can occur even with the vehicle sitting in the hot sun on a summer day! On most fuel injected cars, the fuel is constantly circulated thru the fuel rails which are mounted on the top of the engine. As a direct result, engine heat is constantly transferred to the fuel system. This increased heat causes more fuel to vaporize in the tank which results in a pressure buildup. All of these vapors have to go somewhere. If allowed to escape to the atmosphere, at the very least they can present an annoying and smelly problem -- raw gas fumes. The charcoal canister is designed to store these gas vapors until the engine is operated. When the engine is operating at preset parameters, the canister is vented to the intake manifold and thus is "purged" of its stored vapors. Most 96-up OBD-2 equipped vehicles have what is known as an Advanced EVAP system. Here, a second canister is installed back by the gas tank and its function is to store gas vapors accumulated during refueling.
The EGR system is a little more involved in its function. The EGR valve and system are designed to introduce INERT exhaust gases into the intake manifold and engine during preset circumstances. The primary reason for doing this is to cool the combustion event which results in less NOx gas emissions from forming. There are a few side-effects to having a functioning EGR system present. First, because the EGR system is cooling the combustion event, less heat is transferred to the engine resulting in less cooling load on the cooling system. Second, the inert gas present takes up space that would otherwise need to be occupied by more fuel and air. Therefore, in affect, the engine effectively becomes "smaller" (breathing less) and more efficient using less fuel when the EGR is operating. A properly functioning EGR system has been shown to cause slightly better gas mileage compared to an identical engine and vehicle without a functioning EGR system. Now there is a potentially damaging drawback to removing or disabling an EGR system on a vehicle. If the computer does not know that the EGR is not functioning, it may be commanding more ignition timing (as it usually does when it commands the EGR system ON) which can result in hotter combustion temps and even detonation. If you remove or disable your EGR system, you should have the computer reprogrammed to disable the EGR spark advance parameters or significant engine damage could result. Shown below are some of the EGR adjusting tables from a 1987 Fiero 2.8L stock chip program that show the adjustments the ECM makes to fuel and spark when it thinks the EGR is operating...
As you can see in the left table above, the Fiero ECM will add as much as 9.5 degrees of spark advance to the existing timing advance when it thinks the EGR is operating at 43.75% Duty Cycle or more. The table on the right illustrates the amount of reduction in fuel delivery the ECM is giving the engine while it thinks the EGR is operating (the BPC number = base injector pulse constant; the lower the number, the leaner the fuel delivery). As with all GM ECMs, the ability to detect a fault with the EGR system is built in by the factory. However, in order for the ECM to detect a fault with the EGR system, the engine must be run for a predetermined amount of time and operated under certain conditions before these "self-checks" of the EGR system are run. Once a fault is detected, the ECM can set a trouble code for the EGR system which will suspend all EGR operating commands (including changes to the fuel and spark). The trouble is, if you have disabled your EGR without reprogramming the computer; until a fault is detected, the ECM could be giving your engine more timing and less fuel than it needs which can lead to damage. On most GM computers, once the engine is shut off, these self-checks may be run again by the ECM on the next key cycle. Some engines, such as the Fiero application being discussed, uses no knock (detonation) sensor. So damage occurring to the engine by disabling the EGR system without reprogramming the computer is a real threat. The CORRECT way of disabling your EGR system is to have the computer reprogrammed to disable it which will disable the adjustments made to the fuel and spark delivery.
Carburators vs Fuel Injection (click to read article)
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