turbo newbie guide

[weltall]

BEFORE Turbo Modifications
TO MODIFY or NOT,
THAT is the Question! From discussions with many Turbo owners, I have found that some want to retain the factory performance, while others want to make major modifications for the full power potential of their Turbo Vehicle.

( typed car but changed it, because you may have a Van or 4WD as some of our RTO's do.)

In between these two extremes are many that are trying to increase power to a reasonable ( for them ) level, while not spending a lot of money and retaining reliability. ( forget fuel consumption because to make power you have to burn the required amount of fuel.) ( at least while under boost!!! )

There are many ways to save money while doing modifications and power ups, and that is what the this info is all about. I would be one of the most cost conscious rev heads around but some (most) times you have to spend money (wisely) to make power. Obviously the more you can do yourself, the cheaper any modification becomes. If you know exactly what needs to be done, paying someone else to do just that also saves money. It's when you are unsure of what is required to be done to achieve your goals that leaves you open to exploitation. This is usually by persons who may or may not know how and what to do to meet your expectations. To this goal of doing what requires to be done to meet your needs, we will endeavour to advise you on the best way to proceed.


Detonation

PINGING, PINKING ( or DEATH RATTLES )

These are names for two conditions that can cause loss of power or pistons. You have probably heard them under the bonnet your self.

Detonation and Pre-ignition are two separate effects with different causes, but can occur at the same time. Detonation of the fuel air mixture under boost conditions is the number one enemy of any turbo engine. Detonation is defined as it says as a detonating effect in the combustion chamber on the compression stroke as the piston progresses on to its downward power producing travel under normal operation. The power caused by combustion is meant to be produced in a smooth (relatively) expanding of various gases as a product of burning the fuel air mixture.

Detonation is similar to hitting the top of the piston with a gelignite charge instead of a mighty push. I have not read any statistics on this but I suspect that the flame front on normal combustion travels throughout the chamber at up to three thousand feet per second similar to a rifle cartridge being fired. This produces the fast push to the piston from the rapidly expanding gasses, while the speed of the flame front on detonation could be up to ten thousand feet per second, similar to an explosive initiating detonator.

From experience this is similar to the known fact that under loading ( less powder than air at the right ratio) in a rifle cartridge can cause the effect of the whole breech block exploding instead of just pushing the projectile down the barrel. My early career was RAAF Armourer with extensive weapons and advanced explosives training and experience, so I have drawn my own conclusions above. Irrespective of cause,

Detonation is to be avoided at any cost.



PRE - IGNITION

Pre-ignition is the effect of the fuel air mixture in the combustion chamber igniting before the optimum point of the piston coming up on the compression stroke before Top Dead Centre (TDC).

Normally the ignition is usually started by the spark from the spark plug at the correct time allowing for the speed of piston travel and flame propagation time, the expanding gases should be happening just on TDC to push the piston down again.

Pre-ignition can be caused by the incorrect timing of the spark to the plug or some other means of ignition that does not require the spark from a plug. This means that if ignition is caused by some other means prior to normal spark, then the gasses will be expanding while the piston is travelling up toward TDC. A good way to reverse the rotation of the crank!!!

Well maybe not but it is a sure way to loose power! Considering that fuel and air are the two most important reasons that you can make power from some metal objects working in various relationships, not forgetting the spark or ignition that makes it all happen, lets explore this relationship.

FUEL

Fuel can be categorised into a few types that are relevant to octane rating and lead content. We know these as STANDARD, SUPER, UNLEADED, & PREMIUM UNLEADED (PULP). Obviously UNLEADED means no lead added to the fuel for what was originally to lubricate and cushion valves, and to raise octane ratings.

For the serious production of power in a turbo forget UNLEADED, as the octane rating is not high enough to prevent detonation at high boost. As STANDARD (Leaded Low Octane) is no longer available that I know of, (at least in Melbourne Australia.) we will disregard it and concentrate on SUPER & PULP.

SUPER is what us owners of older model turbo cars run, as it is the only option, and I suspect of various octane ratings dependent on the Garage (old word now will use SS - Service station from now on) has put in the underground tank recently. I was under the impression that all SUPER was supposed to adhere to a government standard on octane rating but real world driving on high boost after filling at different SS's says otherwise, if detonation has anything to do with it. Has anyone else noticed this?. After trying SHELL half lead SUPER a few times, I suspect what they say about its still high octane rating could be true.

PULP is what the owners of new turbo cars get stitched up at the SS pumps by a margin of 10 cents a litre over SUPER price.(Think I'll keep the old STARION.) Disregarding the octane rating in SUPER & PULP and praying its still over 96RON ( I think ), lets explore the other two factors that govern the control of detonation where fuel is involved.


Detonation is to be avoided at any cost.




FUEL VOLUME & PRESSURE

To some degree related, volume of flow and pressure are important factors in peak power with out detonation, the killer of high compression, or high boost engines. Every time your pistons compress the FUEL/AIR mixture on the upwards compression stroke (ok, Subaru/Porscheand Mazda Rotary owners you know what I mean!) the AF ratio must be right to promote combustion of the mixture in an even and constantly progressive manner. We wont get into exact technical terms and descriptions here . Suffice to say that if the mixture is LEAN (more air than fuel at the correct ratio) the chances of detonation are increased dramatically due to much higher temperatures of combustion and speed of flame front.

This means that we need the right amount of fuel to be delivered to the combustion chamber considering the amount of air under boost and its volume and temperature. As you can see all these things are interrelated and are managed by your computer and sensors in the case of fuel injected cars, and in the others running carburettors, good luck! (Sorry about that.) What I am trying to get at here is the fact that fuel delivery is most important and if you want more power out of your standard turbo car you have to address the issue of ensuring enough fuel for the mixture.

Most turbo cars management systems will deliver correct mixtures up to the factory set boost limit and beyond to a few pounds more but must be helped in some way if serious boost ( 14.7 PSI / 1 BAR ) and more is needed. With the previous information in mind it is a good idea to check and possibly replace some components of your fuel system for optimum operation. As an example here I will detail some things I have done on my Starion but apply to most turbos with Electronic Fuel Injection. -

Replaced conical strainer in entry to rear fuel pump on top of tank, -Replaced pump with higher flow unit ( VL Turbo Commodore), -Replaced fuel filter larger flow unit, -Replaced boost air sensor line from throttle body to fuel pressure regulating canister (most important - more boost needs more fuel to keep the fuel / air mixture right!!)


Detonation is to be avoided at any cost.




AIR SUPPLY

BEFORE & AFTER TURBO FUEL / AIR mixture is critical, and your air supply is as important as fuel, and can be vastly improved to not only make power, but be more fuel efficient in most cases. Most factory intake set-ups can be improved to some degree dependent on your ingenuity and skills.

The most effective immediate change is to a Foam Type FINER Filter or similar that uses washable foam element with a very sticky special liquid that traps dirt etc but allows high clean air flow. Another effective trick is to get cold outside air to the air box, as under bonnet air can be 50 degrees hotter after coming through the radiator and intercooler if fitted, as well as the heat generated by the turbo. All pipes and hoses should be as large a diameter as possible with smooth bends and interior surfaces going as direct or short path as allows. AIR TEMPERATURES.

The cooler the air when it enters the combustion chamber the better. Ever noticed how well your turbo goes on cool crisp evenings? This is the job of the must vaunted INTERCOOLER. This much misunderstood item acts just like your radiator does to hot engine water that hazs done its job of cooling the combustion process on its way circulating in your motor and possibly water cooled turbo.

Simply, hot compressed air from your turbo is routed through the INTERCOOLER (usually mounted in front of the radiator in the oncoming air stream to benefit from maximum cooling effect from the air forced through.) As the boost air flows through the INTERCOOLER it looses its heat to the cool alloy of the core as it passes through on its way to the throttle and intake to the cylinders probably 50 - 70 degrees Celsius cooler than when it exited the turbo compressor.

Detonation is once again defeated by this cool and denser packed mixture that allows more power on ignition. Another trick is to fit what most factory turbo cars now have, the TURBO BY-PASS VALVE. This valve is operated by manifold vacuum and opens to allow boost pressure that has built up on acceleration to be recirculated when the throttle is closed between gear changes. This valve allows the air to return back into the intake to the turbo for recirculating so the blades of the turbo are not stalled when the throttle is closed and the air in the intake pipes keeps moving instead of stopping momentary.


Detonation is to be avoided at any cost.




EXHAUST HEAT

The turbo charger on your car is driven by exhaust gasses as they exit the combustion chamber at the end of the power stroke. Flowing at high temperature and speed through the head ports and into the exhaust manifold, the gasses are then routed into the exhaust snail of the turbo. The temperature being dependent on various factors including fuel/air mixture ratio, sustained RPM, cooling efficiency, charge air temperature and others.

This high exhaust temp can have a detrimental effect on certain early Mitsubishi Starion and Cordia (and probably other makes) exhaust manifolds, causing extreme cracking and leaking. Apparently the metal casting mixture was not correct to withstand the high temp's involved and was rectified on post '84 models with an upgraded metal composition. So this means check yours now! (Sometimes its hard to get to your manifold under all that plumbing, but its worth it to know everything ok before modifying for more boost.)

Look for obvious cracks or signs like white markings and check with a hose held near the crack and the other end to your ear. You can hear the exhaust leaking with the car idling. Obviously the only proper fix is a new (JB/JD in the case of the Mits. STARION) manifold. Check with your Factory Parts Dealer. Any manifold leaks before the turbo contribute to a loss of power as the full exhaust charge is not available to help turn the turbo exducer blades, therefore the turbo shaft and compressor wheel is not spinning to it's max RPM.

EXHAUST TIPS Check and replace Exhaust Manifold and Gasket if leaking. Wrap exhaust manifold in thermal tape to contain heat and improve thermal efficiency, also reducing under hood temperatures. Fit more metal heat deflectors reducing radiated heat damage to under hood components.


Detonation is to be avoided at any cost.




LUBRICATION - OIL

OIL's AIN'T OIL's Oil is the life blood of any engine, but more so for an early turbo car without water cooling to the turbo centre bearing housing. The later turbo's tend to have water recirculated thorough them as part of the normal engine cooling system. On early turbo's, the oil is expected to do the job of lubricating and suspending the centre bearings as well as cooling the whole turbo before draining back under gravity into the motor sump.

The oil is fed usually to the top of the turbo centre housing from the back of the motor oil pump at high pressure. On water cooled turbo's the oil has an easier job as some heat is dissipated into the water flowing through the jacket and this prolongs the life of the turbo generally. The main benefit is to prevent heat soak back coaking of the oil sitting in the stationary turbo after turning off the motor. Under normal driving the oil is pumped into the top of the centre bearing housing already hot from circulating through the engine and then flows down into the sump hotter than before the turbo.

This is why the STARION has a large oil cooler mounted at the front of the radiator in the air stream. When the engine is turned off, the turbo spins down and the oil sits there and cooks from the heat that soaks back from the turbo exhaust housing as the oil has now stopped transporting a lot of the heat away into the sump. The oil then begins to turn into a thick cooked sludge that can seize the turbine bearings and shaft.

OIL TIPS Check your oil, is it turbo quality, can it handle high temperatures. Do you change it every 5000 Klm's or sooner. Have you considered synthetic oils such as Mobil 1, etc. Do you have an efficient oil cooler or an extra one fitted. ( writing this I have just thought that it may be good value to have one on the oil line to the turbo or even after it, making sure there is no restriction as its a gravity drain back into the sump.)


Detonation is to be avoided at any cost.




COOLING - WATER

The engine water cooling system on a late model turbo car is probably running at the limit of operation with the added heat of the turbo cooling water included. As mentioned above the main function is to dissipate heat from the turbo housing to prolong the life of the bearings and stop heat soak back.

This is the reason that some cars have "turbo timers". The timer is there to allow the turbo temperature to stabilise and cool while the engine is idling prior to turn off. This is especially important after high speed operation or spirited driving prior to turning off the motor as the turbo exhaust temperature could be in excess of 800 Degrees. If you don't have a turbo timer you can do as I do, which is take it easy when you know you are going to be turning off soon and after stopping just let the car idle for thirty ( 30) seconds before turning off.

WATER TIPS Change your cooling system fluid with high quality coolant to prevent corrosion and effectively remove heat from the motor and turbo. Ensure your radiator is not internally or externally blocked, preventing either water or air flow through the core. If your system is running hotter than usual then many reasons can contribute to this, including incorrect timing, lean air/fuel mixtures and other obvious reasons. These might include low water level, leaking system, incorrect or faulty thermostat, faulty radiator cap, worn or loose fan/water pump belt, or even the unobvious rusted and broken water pump blades.




BREATHING

On most factory turbo cars, the air for the motor is generally drawn in through the air filter, metered for the computer to control the air/fuel mixtures, drawn into the turbo, compressed and ducted to the intake manifold. The intake manifold usually has either a multi point or throttle body fuel injection system.

The air compressing part of the turbo at the front of the centre housing that sucks in the air and blows it out the exit of the snail is extremely hot from both the action of compressing the air creating boost pressure and transmitted heat from the exhaust snail. The purpose of the turbo intercooler is to reduce the air temperature going into the motor contrary to the belief of certain motoring writers you may have come across. See the other explanation on detonation for more detail on the intercooler's function.

AIR TIPS Make sure your air cleaner is not blocked with dirt or oil grime. Replace with a non factory foam or cotton type that gives better flow and filtration. Ensure the intake hose to the turbo is not cracked or split especially around the edges near the entry as the heat tends to harden the rubber and make it brittle (at least on Mitsubishi's anyway, but I suspect on others as well.) Check all intake hoses and pipes after the turbo for air leaks under boost.( Sometimes hard to find!)

Fit a MASSIVE intercooler if possible for max power. (And a bit more lag, so make pipes as short as possible.) Make sure it can stay cool as possible by mounting in the air stream and maybe assisting airflow with an electric fan under high boost conditions. Consider air to liquid intercooler which is more complex, but more efficient.




BOOST

Boost is power!! - The more, the cooler, the faster, the BETTER !!! Well maybe for some of us anyway. Myself for sure, but for some, the factory allocated portion is enough. Even these people need to consider the turbo boost controller or "WASTE GATE CONTROL CANISTER" .

This is the small round can that is attached to the turbo housing with the metal arm stretching across the side to the Exhaust snail. It usually has a small hose joining it to the front of the turbo compressor snail outlet. This is so the boost pressure can cause the waste gate to be actuated by the compressed air to open a small valve in the exhaust snail to by-pass some of the exhaust gas pressure to the exhaust pipe after the turbo. ( See illustration )

When the by-pass valve opens and lets some of the gasses escape to the exhaust, the turbine shaft slows down and this reduces the compressing action or boost.

TURBO BOOST TIPS

The spring in the wastegate canister will loose pressure after time allowing boost to take more time to build up as exhaust gas is leaking past the by-passing valve.

If the boost sensing hose to the canister is leaking, boost will go too high and detonation or fuel cut-out will occur. ( in Mits. STARIONS & CORDIAS anyway, others may be similar.) Indecently, this is how we modify the factory boost setting, but caution must be exercised as many factors must be considered before doing this.




MODIFICATION SEQUENCE

The person that wants to modify their Turbo over a period of time building up the mods in a progressive power and cost escalation should possibly follow the listed path to get the most benefits.Don't forget to also DYNO TUNE & GAS ANALYSE your modifications for correct mixtures between each step.

1. Check current state of engine and turbo, including exhaust manifold and wastegate operation.
2. Service standard motor first to Manufacturer specs. Change all fluids.
3. Check Brakes. ( You need to be able to stop as well!!) Check all HOSES, AIR & WATER.
4. Replace Air filter with Foam type.Duct cold air to Air Cleaner.
5. Replace Spark Plugs with NGK or Splitfire
6. Modify Boost to higher level. ( 3-4 PSI)
7. Alter Timing to suit.
8. Adjust fuel if req. for correct Air Fuel ratio
9. Turn down boost to lowest level.
10. Fit Larger Dia. Exhaust 2.5" to 3".
11. Re-adjust boost back to previous level.
12. Fit Intercooler - Larger the better in air flow.
13. Fit Turbo By-pass Valve
13. Increase boost now to limit of fuel cut out.
14. Fit fuel cut defender.
15. Adjust boost higher.
16. Increase fuel to keep Air /Fuel mixture correct.
17. Fit modified Camshaft for more exh. duration
18. Modify Turbo or Replace with high flow unit
19. Replace exhaust manifold for high flow
The easiest basic modification is to increase the boost moderately by a few pounds which should give approx 10 HP per Pound. you can feel 20-30 HP at the seat of your pants ok.




CONCLUSIONS

Conclusions on power up serviceability .

The implications of progressive or high boost mods to the engine are always present in the way of stress related engine failure or detonation because of lean air fuel ratios or heat or timing problems . High power mods always lead to increased chance of problems but if working from a position of knowledge, the chances are reduced.

I believe the best way to avoid detonation is to dyno tune your car on a gas analyser after mods to ensure the fuel air mixture at max boost is still not leaning out. If you use the same dyno each time you should have a valid comparison on power increases after each stage.

As figures across different dyno's tend to conflict, don't take much notice of the numbers except as a guide. The most important aspect is the fuel delivery at maximum injector duty cycle and boost pressure as measured by the exhaust gas analyzer.

Always ensure that the dyno operator has a large fan directed at your intercooler if fitted as well for more accurate results.

[weltall]

also remember

cheap
fast
realiable

you can only pick two and you will never have the one thats left