How Do I Choose A Hybrid Turbo?
The simple question you need to ask yourself is, what do you really want out of your Hybrid Turbocharger?
It’s very easy to be convinced into buying a turbocharger that guarantees an increase in power but how long will it last? How do you know what parts are genuine and which parts are not?
At Turbo Dynamics, we pride ourselves with the quality of every single hybrid turbo we manufacture. Designed and made with precision under ISO quality control systems. We are the market leaders and have the vast, specialist experience needed to create the reliable turbo you want and need.
We have been supplying Turbochargers for a range of customers, from professional rally teams and drag racers to current F1 teams since 1991. Why settle for second when you could be first?
Over the last three decades, we have been constantly adding new models and applications to our Hybrid Turbos range which is already topping 500 plus models. Within these new models we are always testing the latest innovations in turbocharger design, and after rigorous testing, incorporating them so you the customer have the very best and latest technology that is available.
Some of the options available:
- CNC Machined compressor covers with “Ported Shroud” technology
- Designed and flow tested for maximum airflow
- Special compressor wheel design and sizing
- Precise blueprinting of each modified component for optimum performance and reliability
- CNC Machined 360 degree thrust bearing assemblies
- Special one-off turbo design to suit the most demanding applications “Road or Race”
- Modifications and machining carried out in-house for maximum quality control
- Garrett GT “Ballistic Concepts” roller bearing conversions
- Uprated actuators & brackets available for exacting boost control
- Hi-temperature and ‘Total Seal’ piston rings seals available
- Up-rated wastegate poppet valves and bushes
- Cutback or ‘Clipped’ turbine blades
Other things to consider that are contributing factors to the performance of a turbocharger system
Cylinder Head Porting
Cylinder head porting is one of the most important factors to consider (along with camshafts) when turbo matching your engine and it can have one of the biggest impacts on your turbocharger performance.
Many people believe (incorrectly) that bigger is better when it comes to port size and design when modifying a cylinder head, this could not be further from the truth when fitted to a turbo car.
A turbocharger relies on exhaust gas speed and expansion to operate correctly so if the exhaust ports are too big the gas expands too quickly, cools and slows down. The same can be said (to a lesser extent) on the intake side. A big port needs more air and time to fill so the net result can be more lag.
It is common knowledge these days that the manufacturers are getting better and better when it comes to cylinder head design and manufacturer, so much so that some tuners have actually lost power from “porting” a cylinder head. The biggest gains are usually made from carefully tidying, matching and blue-printing of the ports.
Most modern engines are now fitted with at least one knock sensor; some even have one per cylinder. The device can sense internal pinking (not always audible to the human ear and relay this information back to the ECU, which in turn can then immediately adjust the ignition timing to eliminate it. A must on any high-performance engine.
This is again one of the most important factors to consider (along with cylinder head porting) when turbo matching your engine as it can have one of the biggest impacts on turbocharger performance. Again, many people believe (incorrectly) that bigger is better when it comes to camshaft size and design when modifying an engine, but this could not be further from the truth when fitted to a turbocharged car.
Camshaft Valve Timing
The bottom line is, big camshafts with wild lift and overlap work very well on naturally aspirated engines, but they don’t work so well on forced induction engines, if you want good response and no lag, they simply don’t work! Sure, you will get power increases, but mostly at the very top end of the rev scale, the bottom end response will be very poor.
This sort of cam design can also have a more serious side effect on the turbo as it can increase the chances of inducing compressor surge from the turbo, again due to the gas speed. We have many situations where we have had to down spec a hybrid turbo to fit an engine with a “Ported & Polished Head” and “Fast Road Cams” to gain the same response as a larger turbo on a standard engine.
This is not as critical as the porting and camshaft design but again it can have a big influence on the matching and performance of the turbocharger you select. Cam timing will not have much of an effect on overall performance but there are gains and losses to be had, for instance, retarding the cam timing can often help with response and lag, just the same advancing the cam timing will give more top end power.
Most of the time we find the manufacturers have got it pretty well sorted from the factory (not allowing for mass-production variance). Obviously, you can’t beat adjustable cam timing to set it to the optimum position.
This is a difficult one to pinpoint for absolute power and torque gains. A low compression ratio will be of benefit when you are planning to run high boost, if the boost is too high for the compression ratio, this will lead to “Detonation” or “Pinging” when under load.
A low compression ratio – say 7.5:1 will be of benefit for big horsepower but again the trade-off is the response or lag (gas speed again). It is very important that we get back to the application and decide what the car is used for along with what you are trying to achieve.
In our experience a compression ratio of 8.5:1 is around the mark for the best compromise between response and power, it is also important to remember that you can always cheat a little here and use different fuels (super unleaded/octane booster) to overcome the problems of detonation associated with higher boost levels. The main manufacturers are actually going higher and higher with compression ratios to reduce lag and increase torque, this is mainly due to the very sophisticated management systems now available and the general improvement in the fuel we get from the pump.
There are many more factors that come into play when choosing a compression ratio and one type of engine can be quite different to another.
We have a particular component here which divides the tuning fraternity down the middle, some people believe a drain pipe exhaust system (3.5-4.5”) is the way to power nirvana, where as there is a camp that believes in a well-made average size (2.5-3.0”) with flowing mandrel bends will be of more benefit, we tend to sit in the later camp for a couple of reasons.
The engine/turbo combination on any vehicle was never designed to run with a 4” ‘drainpipe’ exhaust with one straight through box at the back.
These big exhausts often have very detrimental effects on the turbocharger, the turbo oil seal system is designed to run as a pressure differential seal and the lack of back pressure is one of the first reasons a turbocharger leaks oil (smokes at idle and on overrun). How many turbo cars do you see with 4” exhausts smoking at the traffic lights?
The other important factor is that the wastegate system (on integral wastegate units) are designed to have back pressure to equalise the gas pressure before & after the turbine, this differential can be so distorted by these exhausts that the waste gate can no longer control the boost which leads to boost spikes, boost creep and worst still, can cause an over speed of the turbine rotor which will cause premature failure of the turbo.
This one is really an open field as far as the many different methods available. The best system is obviously integrated into the vehicle electronics and controlled via the mapping.
We’ve seen some bodge jobs over the years, a common one being the over-adjustment of the wastegate actuator (too much pre-load), so much so that the wastegate can no longer control the boost which leads to boost spikes, boost creep and worst of all, over speeding of the turbine rotor which will cause premature failure of the turbo. We’ve also seen the drilling small holes in the actual waste gate actuator or sensing hose to bleed off pressure (actually wasting precious boost pressure).
At the very least you need a bleed valve (crude but better than drilling holes) which is at least adjustable, but ideally, you want one of the various aftermarket electronic bolt on kits if you have no other way to control your boost.
The intercooler part of the system is probably the least important in the majority of applications, unless you are running higher boost (1.4 bar and above), however, there are things to keep an eye out for, firstly pressure drop across the intercooler (pressure difference from the inlet to outlet side) and the charge air temperature difference again from the inlet to outlet.
The figures for pressure drop should be no more than 1-3psi, if you have more than that, there is a mismatch somewhere in the system. As for temperatures, it is important to keep an eye on the temperature going in to the cooler (this will vary according to boost levels) but on the outlet is where it is critical, and you should be aiming for a temp range of 30-40 degrees C, any more than that and the intercooler isn’t doing its job properly.
A word of warning here, this doesn’t mean you necessarily need a front mount intercooler, you may just need a more efficient standard size replacement intercooler.
The mapping is really what it is all about, get it wrong and at best you will have a thirsty handful to drive, at worst, a destroyed and melted engine! Get it right and the difference can be amazing. There are various methods employed to achieve the best map for the application, the best solution is a live map (all cars are different) on a rolling road with part load capability, at the other end of the scale you have mass produced “tuning chips” that are a fix all for all vehicles (not great).
There are some tuners who actually map on the road with wide band lambda sensors and associated test kit via a laptop, this is a great system as it involves real world driving and loads which a rolling road or engine dyno can sometimes lack, but it is a little risky as it’s hard to concentrate on a map parameter when you are doing 150mph on the open road, plus if something goes wrong, you can’t just stop and turn off the engine!
The best method again will be down to budget, but don’t let this final and most important part of the tuning process become the common “close enough is good enough” fix, after all you have spent a lot of money to get to this point why wreck all the good work with a poor state of tune!