1.) Less RPM – This is the number one killer of an engine. If you can make enough power at a lower RPM you should do it. Don’t forget missed shifts, now that’s a real killer.
2.) Optimal Coolant Temp – Both running an engine under power with too much water temp and too little temp can be harmful. High temps are the worst, with blown head gaskets one of the first signs of trouble. I’d say between 160′ and 210′ is best, never over 240′.
3.) Optimal Oil Temp – Low oil temp lowers oil flow. Higher oil temp breaks down the oil and gives way to the chance of metal parts coming into contact. Drag Racers usually race with the oil temp too low and stock car racers too high. Try to get near 200′.
4.) Less Compression – I’m a real fan of less compression. If you don’t need the extra power then there’s no need having the engine on melt down. If you’re in a competitive class then you have no choice. I’d keep it under 12 if you don’t need the power.
5.) Proper Ignition Timing – Too much timing leads to pre-ignition, which is like hitting the piston with a sledge hammer. Too little timing can lead to extremely hot exhaust valves. What happens if an exhaust gets too hot? The head eventually falls off. The only way to know the right timing is by dyno testing, track testing or reading the spark plugs.
6.) Tighter Lash – The weakest link in most engines today is the valvetrain and nothing kills it faster than too much lash. Just adding .010″ of lash can double the force on the valves. The only negatives to tight lash is usually less torque and the chance of holding the valve open if you go too far. Consult your cam maker for a usable range.
7.) Optimal Oil Level – You probably think I’m going to say too low is the problem, well if someone is going to make a mistake on oil level, 90% of the time it’s going to be too high. Too much oil can lead to the crank and rods whipping it up and adding air — not good. Most applications are very safe at 6qts.
8.) Proper A/F Ratio – Too rich a mixture can cause problems, for example carbon build up and washing the cylinders down. The real risk is from too lean a mixture. Just like ignition timing the only way to know the right mixture is by dyno testing, track testing or reading the spark plugs.
9.) Proper Clearances – Rod bearing clearance, main bearing clearance, piston to wall clearance, lash, etc., all are extremely important. You’d be shocked to know how few engine builders know exactly what these specs are. My advice, buy the tools and learn how to assemble your own engine.
10.) Proper Startup – I can’t tell you how many times I’ve seen this, someone starts their racecar completely cold and proceeds to rev the engine between idle and 7000 RPM. All engines need time to warm up. Better yet, how about oil and coolant heaters?
Sometimes when you are tuning an engine that is already in a vehicle on a chassis dyno, a lot of strange things can happen that you should be aware of.
First of all, it is important to keep a perspective on all the things that are happening. It can be very difficult to keep track of engine temperature, manifold pressure, air/fuel ratios, engine torque and horsepower readings all at the same time. It will take some practice to get comfortable with all of this while the wheels are spinning.
Try to pay attention to things like traction of the tires on the rollers. Many cars that produce big power can easily overpower the amount of tire adhesion to the roller, and this will dramatically affect the amount of power the dyno records. If you aren’t applying all the power to the roller, it can’t tell how much power you are making. On a dyno chart, this can normally be seen as an abnormal spike in engine speed and a corresponding drop in power and torque readings.
It is also important to remember that if you are recording Air/Fuel ratios with anything but the most high-speed exhaust analyzers that it is very common to get false readings when the engine accelerates too quickly. This happens because the engine speed changes so rapidly that the exhaust meter cannot update its sampling rate quick enough. By the time it processes a sample and displays it, the engine can be well beyond that operating range and be dangerously lean, or grossly over fueled. This makes it nearly impossible to record data and make accurate changes to the calibration.
Soft compound racing slicks and/or too little tire pressure can cause the tire to deform on the roller and actually decrease surface contact! Use a good radial street compound tire and strap the vehicle down tightly against the rollers.
2. Tuning Ignition Timing Tables
Whether you are tuning an engine on an engine dyno or a chassis dyno, you should always make sure that it gets tuned to the proper amount of ignition timing.
The best way to do this is to use a steady state holding pattern on the dyno and hold the engine to a specific RPM. Then load the engine to whatever site you wish to tune and record the instantaneous power readings.
When you make a change to add or subtract ignition timing, you will normally see a corresponding change in power output.
Using an onboard or aftermarket Knock sensor to check for detonation is the easiest way to find the maximum allowable ignition advance. However, if you do not have access to one, here is another way to get pretty close.
Advance the timing until maximum power is reached and begins to fall off when more timing is added. From there, back off the ignition advance one or two degrees and set it there.
Once you have made a few hard pulls on the engine at this setting, shut it off and remove the spark plugs. Inspect them for obvious signs of detonation or erosion. Pay careful attention to the J-shaped ground strap. You will notice that somewhere on the strap it begins to change color.
Ideally, when the proper timing is set, there will be enough heat in the combustion chamber to make the color change at about the center of the strap. If it changes more out towards the end of the strap, then there is not enough heat, and more advance is needed. Conversely, if the color change is near the bottom where the strap joins the plug, then take some ignition advance out in order to start the burn later and transfer more heat out the exhaust!
3. Using Ignition Timing to Stabilize Idle
When tuning a small displacement engine with very large injectors, you may have trouble establishing a good solid idle. This occurs because some ECUs do not have the injector driver strength to open and close these injectors for a short enough period of time and remain consistent enough to control the fuel.
Other than using a better quality fuel injection computer than what you already have, {assuming you’ve already purchased one}, there are a few tricks to help you along.
First, always make sure that your ECU is getting full battery voltage, if not more from the alternator. The ECU will have a much harder time staying consistent if the supply voltage is not up to par.
Second, use a little more ignition advance at idle than normal to help the engine produce slightly more torque and keep itself running a little better.
Lastly, try lowering the base fuel pressure just slightly to take the pressure off of the magnet coil inside of it. The less pressure it has to open the valve against, the easier time the injector driver will have when trying to open it. You don’t want to go down too low though, or poor fuel atomization can occur and make the poor idle situation even worse!
I have found that some of the better brand ECUs such as Motec, Autronic, and EFI Technology have very little problems controlling very large injectors on even the smallest engines. If you are looking at purchasing a fuel injection system for your project and idle quality is a concern, these might be good systems to look into. It is often beneficial to look at all the pros and cons of owning a particular brand of fuel injection system other than initial cost alone.
4. Using Oxygen Sensors
Tuning a modern fuel injected engine is nearly impossible without the use of an oxygen sensor. There are a few points to consider when finding a suitable place to mount the sensor in the exhaust manifold.
First, always try to mount the sensor so that it collects mixture data from as many cylinders as possible. Try to avoid having the sensor only get one cylinder’s exhaust whenever possible. On an with the cylinders laid out in a V configuration such as a V6 or V8 it is most desirable to place the sensor in the exhaust collector where at least half the cylinders come together.
On a small four-cylinder engine using a turbocharger, it is common to place the sensor just before the inlet of the turbo. This a good place to collect exhaust mixture information, however it is possible to overheat the sensor in this location. Most exhaust gas oxygen sensors can withstand up to about 800 degrees Celsius, but at times a turbocharged engine can easily exceed these temperatures.
Also be sure that there are no openings or cracks in the exhaust system ahead of the oxygen sensor. This can introduce fresh air into the exhaust stream and cause the air/fuel ratios to seem leaner than they are.
Lastly, some modern cars are now using air injection pumps to introduce fresh air into the exhaust stream in order to reduce exhaust emissions. This fresh air can also easily fool the oxygen sensor into thinking the engine’s actual air/fuel ratio is leaner than it really is. Be sure to disable any such devices before you begin your tuning.
Always protect your sensor from chemicals such as sealants, and remember that using leaded fuel will drastically shorten the life of your sensor.
5. Back to the Basics
When I was young and just starting out tuning engines an old man said to me “ninety percent of all your carburetor problems will be found in the distributor”. At the time, I thought he was just a kooky old man. After years of tuning, my own experience seems to have proven him right. Many tuning issues with both carburetors, and modern fuel injection systems are mistakenly blamed on the fuel system.
One thing to watch out for when tuning an engine using a modern fuel injection system is false information from an oxygen sensor when an engine misfires.
When an ignition event fails to happen, or the engine “misfires”, the oxygen sensor will want to read a leaner mixture than what really exists. This is due to the fact that the oxygen sensor can only read burned hydrocarbons. When the engine misfires, the unburned fuel doesn’t get recognized by the sensor, so it seems that there is a large excess of oxygen in the exhaust system.
Many novice tuners immediately begin to add fuel to the base fuel tables in an attempt to correct a lean mixture induced misfire. Not only does this usually not correct the problem, it often serves to make matters worse. Having too much fuel can also induce a misfire.
Always be sure that the ignition system is in good working order. Visually inspect spark plug gaps and set them according to the manufacturer’s recommendations. Also check that the spark plug wires are not burned or melted by the hot exhaust manifolds and check them for signs of wear.
It’s also a good idea to check all the power and ground supply wires to the ignition system and the high voltage leads to the ignition coils.
I have found that going back to the basics and thoroughly inspecting the ignition system will almost always rectify the problem!
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A. With the exception of forced induction systems (centrifugal supercharger, or turbocharger – where air is forced through the carburetor), air is drawn through the carburetor (sucked) by the engine’s vacuum signal. The amount of air is determined by the strength of the vacuum signal.
2) Q. What is the difference between the straight-leg venturi booster, the down-leg booster, and the annular-discharge booster? Also, when should one be used in preference to another, and how does it affect jetting?
A. A straight-leg booster has, as its name implies, a straight leg, which protrudes from the body of the carburetor into the main venturi. Its discharge ring is situated slightly above the venturi’s most effective zone. Its discharge ring is slightly above the venturi’s most effective zone. The color red indicates the main fuel circuits, which connect with the main jets, the emulsion holes (blue) and the high-speed air bleeds located in the air entry on top of carburetor. The color yellow indicates the idle-fuel circuits, which connect with main-fuel wells, the idle-feed restrictors, the idle-air bleeds (also located in air entry on top of carb), and the idle-discharge ports and transfer slots in the baseplate.
B. A down-leg or drop-leg venturi booster drops the discharge ring lower in the carburetor’s main venturi where it operates in air of higher velocity, which draws more fuel than the straight-leg style of booster.
C. The annular-discharge venturi booster has a larger ring with multiple discharge holes rather than the single outlet hole of the straight-leg or down-leg style of booster. This has the effect of creating a venturi within the main venturi that produces greater vacuum than either the straight- or down-leg varieties and draws even more fuel.
D. In conclusion, the pros and cons of each type of booster are based largely upon its application. However, if each style is tested in the same carburetor with all else being equal, the down-leg booster will require smaller jets to flow the same amount of fuel than a straight-leg booster. And the annular-discharge booster will require even smaller jets to flow the same amount of fuel as the down-leg type.
3) Q. Mechanical secondary or vacuum secondary, which style of carburetor should I use and why?
A. Generally speaking, a mechanical secondary carburetor is preferred on vehicles with manual transmissions and on automatic transmissions with 3000+ RPM stall-speed converters. For automatics with less than 3000-RPM stall-speed converters, the vacuum-secondary carburetor is usually the better choice.
4) Q. How do I set the float levels and what effect do they have?
A. On Demon carburetors in street-driven applications, begin by setting the float levels at _ distance of the sight window. On race applications, increase the levels by setting them between _ and _ distance in the sight window. On Holley carburetors, remove the level plug and adjust the float level until fuel trickles from the open port. Changing the float levels alters the amount of fuel in the bowl (reservoir) and the carburetor’s ability to feed the main jets. By raising the float level the engine’s response is quickened. This is an adjustment frequently used to eradicate a lean stumble. By lowering the float levels, the activation of the main metering circuit is delayed and consequently produces a leaner mixture coming off idle. For street applications the latter condition is more economical.
5) Q. Does a bigger carb make more power? What’s the limit?
A. A larger carburetor can produce more power on a dynamometer, but under normal operating conditions can result in slower acceleration and lower efficiency of fuel atomization. Select the smaller carburetor, especially if you’re undecided about sizes. The smaller diameter venturii increase the velocity of the air/fuel mixture. As a consequence, it usually provides better acceleration and proves to be more efficient.
6) Q. Where should the fuel-pressure regulator be located and what type should I use?
A. The pressure regulator should be mounted close to the object (carburetor, nitrous system, etc.) that’s being fed with fuel. The further away the regulator is placed the greater the delay in its response (its opening and closing). A slower response causes fluctuations (spikes) in the fuel pressure. Regarding the selection of a regulator, specific vehicle requirements, but especially the type of fuel pump already in use dictates the type of fuel-pressure regulator required. For example, combine a block-mounted 15-psi pump with a throttle bypass; a belt-driven pump with a diaphragm bypass; a BG280 electric pump with a two-port regulator and a BG400 with a four-port regulator.
7) Q. How does weather and altitude affect carb jetting?
A. The more oxygen there is in the air the more fuel the engine will demand. For example, as the weather becomes colder (winter) or the altitude lower (closer to sea level), the air will contain more oxygen and the engine will require a larger jet size. In contrast, as the weather becomes warmer (summer) or the altitude higher (mountainous) the jet size needs to be reduced.
1.) You will not go fast by reading the rulebook – You need to get into the pits and see what other racers are doing to go fast. If you build to the letter of the rulebook, you’ll be bringing up the rear at every racing event.
2.) Cheating exists in all types of racing – Some want to sweep it under the rug for the integrity of the sport, but non the less, it’s there. I personally hate cheating, but when your competitors are allowed to get away with murder, what are you supposed to do?
3.) 5% of people will dominate – This doesn’t just apply to racing, but our entire society. I know this may offend, but 95% of the people in the world are just along for the ride. Only 5% actually do anything of value.
4.) You can’t Bolt-On your way to #1 – You can’t order a number one qualifier out of a catalog. Fast racers will modify or design from scratch just about every important part on their cars.
5.) A full-time racer will outperform a part-time racer – I’m amazed how many part-time racers think full-time racers are cheating. I know it may be hard to admit, but they’re just better. Not because they cheat, but because of their experience.
6.) More money does not directly equal more wins – Stop thinking you’re losing because of money. I’ve seen world champs crowned with a tenth of the budget of their competitors. My advice, focus on what you spend your money on. Look at performance per dollar.
7.) Complaining about a competitor or his car will not make yours faster – Worry about you and your car, they’re the only things you truly control. There is no such thing as a perfect car or driver, both can be improved.
8.) The difference between good and great is tuning – I feel like I’ve said this a thousand times, give the same engine to 10 different racers, you’ll have 10 different results. The top tuners will always come out on top.
9.) You can make too much power – Unless you run the Bonneville Salt Flats, there’s a good chance you can over power the track. I see it all the time with short track stockcars — they almost all have too much low end power and spend half their track time at part throttle.
10.) An engineer with commonsense will rise to the top – It’s only a theory because the combination doesn’t exist Alright, I’m kidding, but you have to admit it’s rare. The easiest way to get the same thing is having an engineer team up with someone with commonsense.
1.) More RPM – I’ve found that it’s just about impossible to have too much (higher number) gear in your car if your goal is the lowest ETs. Just keep adding gear ratio until you stop gaining ET, even if the MPH falls off. Remember: racing is usually ET not MPH.
2.) Jetting – If I had to guess I’d say that 80% of all race engines are jetted too rich. Some of the signs of a rich setting are an engine that misses or surges. Try jetting down two sizes and see what happens. Learning how to read spark plugs is my best advice.
3.) Ignition Timing – Go up or down two degrees and make a test. I’ve seen engines tuned with just a couple of degrees too much timing lose 30hp, so don’t think you can’t have too much.
4.) Oil – If you aren’t using synthetic oil already, try it, it’s worked every time for me. The other big thing is oil level, on a wet sump engine too much oil is a killer. No engine needs more than 6qts, no matter what the pan manufacturer says. In fact; too much oil is bad.
5.) Shift Points – If you’re going to miss your shift point, miss it early. A late shift is an ET killer, especially in the lower gears. Here’s a test: If you seem to really be knocked back into the seat after the shift, you’re late. The Reason? Your body went forward before the shift because of lack of acceleration.
6.) More Traction – Obvious subject I know, but here’s one I’ve seen missed more than any other traction aid: Weight. So many people are afraid to add weight to their car, but I would guess that 80% of cars could benefit from weight in the trunk. Don’t take my word for it, give it a try.
7.) Lower Coolant Temp – With all other variables being the same, lower coolant almost always makes more power. There are a lot of ways to lower the temp and I can’t mention them all here, but a problem I’ve seen more often than not is low coolant level. Make sure the radiator is full.
8.) Kill The Accessories – A water pump takes 10hp to drive, an oil pump takes 10hp and the alternator can take up as much as 35hp. Use a low drag water pump or electric drive and put a switch on the field of your alternator to turn off the drag during the run.
9.) Aerodynamics – Now I know changing aerodynamics of your car is not a simple thing to do, but there is one quick modification that I’ve seen work more than once; Lowering the front end of your car. I’ve seen drag cars pick up as much as .01 of a second in ET and 3 MPH in speed by just lowering the car two inches.
10.) Test Different Carbs – Carburetors all have their own personality and some just seem to work better than others. Buy two carbs that are exactly the same and you’ll have different results. My advice: test ever carb you can get your hands on and never get rid of a good one.
In this article we’re going to learn what is required to perfect the 5.0 Mustang’s launch from the starting line. In the first installment we covered the tires. For the second installment we’re going to talk about suspension modifications, you can make to get you down the quarter mile quicker and faster.
The 5.0 Mustang uses a non-parallel 4 link rear suspension. Unlike the parallel 4 link suspension used on Pro-Stock racecars and other full on racecars. Ford used the non-parallel design from the factory as a cost saving measure, because it requires less parts to function, saving production costs. But like any cost saving measure, compromises are involved.
A parallel 4 link suspension requires either a panhard bar or a watts link to keep the reared centered in the car body. The 5.0 Mustang’s angled suspension arms keep the reared centered, without using any additional hardware. By using a combination of short control arms, and long control arms, both with different angles, the potential for suspension binding is very high. Ford compensated (compromised) for this by making the control arm bushings out of a soft rubber compound, that has some give to it.
Anyone who has drag raced their 5.0 Mustang knows all about wheel hop and fishtailing that these cars are notorious for. So the first thing that needs changing is the rear control arms. Ideally the car should use a control arm like the Mega-Bite Sr. which has Heim joint rod ends, to eliminate suspension slop and prevent binding. They also have the added benefit of being adjustable for length, allowing you to center your tires in the wheel well openings. It also will allow you to adjust the pinion down angle, to further adapt launch characteristics. This one suspension modification alone should make a noticeable improvement in your cars starting line antics. No more wheel hop or fishtailing, and much easier to keep in a straight line down track.
The next suspension modification that needs to be remedied is a change to an adjustable shock absorber. If funds are low you could get by with a 50/50 rear shock, and either a 70/30 or 90/10 front strut. But if funds permit, you’ll be much better off in the long run with an adjustable shock/struts. Quality products are available from companies like Competition Engineering, AFCO, Koni and others. Having the ability to adjust your shock settings gives you the flexibility to adapt to future mods in the power department. If you’re like most 5.0 Mustang racers you’ll be adding more and more power to your car as time goes by. What works for your launch at one power level, may prove totally wrong with 50-100 more hp in your engine.
If your street/strip car is more strip than street. More aggressive suspension mods can be performed. Items such as Eibach’s Drag spring set allow for much better weight transfer upon launch. Removing the front anti-sway bar is also another way to loosen up the front end for better launch at the drag strip. It’s also very heavy, and removing it will shave a few pounds off the front end weight of the already nose heavy 5.0 Mustang. Stock weight bias is typically around 57/43 stock, which means 57% of the cars weight is on the front wheels. Not exactly conducive to great traction, which is why I will be addressing redistributing some of that weight in a future article.
For now I would not recommend removing the rear anti sway bar from the car. It serves a purpose, that being to help keep the rear end of your 5.0 Mustang from torquing over to the passenger side when launching. As you add more power to the car a change to an aftermarket anti sway bar or even a double bar system may be in order. But the factory rear bar will take you deep into the 11 second range and perform admirably.
Aluminum Caster/Camber plates are another worthwhile suspension mod. Caster/Camber plates are made by Steeda and others. These devices replace the flimsy factory part, Replacing the rubber bushing upper strut mount, with a much more precise ball bearing, and allow you to add additional caster to the front end alignment. Adding caster to a drag race 5.0 Mustang helps you keep the car centered in your lane and adds stability at the top end. Adjusting your alignment to provide 5-7 degrees caster will help tremendously in keeping you going straight ahead.
Replacing the factory tie-rod ends with an aftermarket bump-steer kit is another trick that will work very well for keeping you from running off the racing surface. Bump steer is the change in toe-in that your 5.0 Mustang experiences when the front end rises and falls. From the factory the Ford Mustang usually has a bit of bump steer built in. Once you start changing things it only gets worse. These pieces will need to be installed at a chassis shop, but are well worth the expense, for the stability your car will receive from them.
Most drivers of high performance cars underestimate the benefit of roller rockers. They are a critical link between the camshaft and the valve. Connecting the pushrod and the valve, rocker arms endure tremendous strain and pressure. Friction forces are enormous at this juncture. Any effort to reduce friction in this area, will result in a definite gain in engine power.
The factory supplied parts basically rub metal against metal. With only a thing film of motor oil separating the two pieces. The roller rocker on the other hand uses needle bearings in the trunnion (pivot point) and the rocker tip. Having all these bearing surfaces in motion, results in a great reduction in friction and heat buildup.
The sliding pivot on the factory parts results in a inaccurate rocker arm ratio. As much as 10% of net valve lift may be lost due to this factor, plus flexing in the weaker design. Aftermarket aluminum or stainless steel arms are much stiffer and have a fixed rocker ratio increasing power. The high performance parts are also available in a higher than stock ratio.
Changing from a stock 1.5:1 ratio to a 1.6 or 1.65 ratio, can increase power by virtue of greater net lift at the valve head. Duration, which is the length of time in degrees (measured @ .050″ lift typically), that the valve is off the seat also increases with the larger ratio. Rate of acceleration of the valve off the seat increases as well, but that is usually not a problem with street/strip type camshafts. What can be a problem is piston to valve clearance. Which should always be checked whenever increasing valve lift, either by changing cams or installing high ratio rockers.
When changing to a aftermarket arm, its a good time to install pushrod guide plates and screw in rocker studs. Most engines do not come equiped from the factory with them and they are much stronger. Guide plates keep the rocker tip centered over the valve stem, preventing premature valve guide wear.
While the engines apart it wouldn’t be a bad idea to check your valve spring tension either. Worn springs can result in an engine that is lazy or slow to rev, also allows valve float at a much lower rpm. Install your new studs with Loc-Tite to prevent them from loosening and torque to recommended specs. Be sure to lube all needle bearings well with engine oil before installation.
Poly locks should be used to maintain valve adjustment. Stud girdles which lock all the studs together for support, should not be required on most engines. If you’re running a very high lift solid roller cam with a double or triple valve spring, then by all means use them. Without breaking into the engine too deep, we’ve managed to increase reliability and picked up a bit of HP too. So you see roller rockers really do increase power.
Alright, I’m kidding, but you have to admit it’s rare. The easiest way to get the same thing is having an engineer team up with someone with commonsense.