Forced Induction, Overview of the whys behind it all. Options

[Micky_lovescelic...]

I decided rather then reply to each individual question here, it is far easier for me to help some of you out. Please understand I do this for a living, and contribute information
merely at my own free will and ( technically it is my day off. ) Some of what I have seen on here is disturbing, and scary. Not to insult, but I feel bad seeing people who really
spend probably a lot of hard earned cash and well un-knowingly pop engines, most of you should get 40,000 to 80,000 miles on a average tuned engine. And about 80 to 300 life
hours on a motorsport race engine.

There are a number of parameters when one discusses the right approach for forced induction. We have to consider the pre-exist vehicle architecture and potential
of the ancilary hardware and mechanical to establish basic parameters. The approach on a factory forced induction application is very different then a vehicle that was
not equiped from the factory with a forced-induction system.


Fuel System : Typically the in-bound or feed line is one AN size larger then the return line. Even when using the proper injector and fuel pump sizing, a fuel system will not flow adequately unless the hoses that deliver the fuel to the fuel rail are of sufficient size and are routed properly. ( aprox ) most of you will use a - 5 ~to~ -8 AN hose / line. Of course
this all depends on the specific set up and ( individual user requirements. ) Depending on how you select your lines you could support 300 ~ 500 + hp. Few here are rocking 700hp
machines.

Typically there is no need to replace the fuel delivery hoses unless the engine is heavily modified. It is never a good idea route fuel hoses through the interior of a car. Put bluntly, this is a dumb & dangerous thing to do.

If applicable or possible, use a delivery tube to make the connection from the pump discharge to the filter in the front of the car. The lines should be rated to withstand at least double the maximum pressure of the EFI system. This is especially true when discussing forced induction applications as fuel pressures in such systems can be much higher then NA or factory applications.

For example a engine with moderate boost, with expected fuel pressures at around 65-70 psi range. This will require a line with at least 140-psi rating (most AN hoses exceed this by a large margin). Double Check, Triple Check that the margin exceeds by at least double and consider how much pressure the lines can withstand at extreme tempretures!

When deciding on routing of the fuel lines, it is absolutly important that they are protected from road hazards, contact with objects and the exhaust system. The fuel line should NEVER be routed near battery cables. Use clamps to secure AN hose every 8~12 inches, or 24 inches if a rigid tube is used ( Technically speaking I prefer bracing more then 24 inches. )

Often overlooked in EFI installations, the fuel filter must have the capacity, filtering efficiency and burst strength to withstand the pressures of an EFI system. It must be able to flow the amount of fuel that matches the maximum fuel pump output. The filter is always located after the fuel pump, however it does not matter if it is positioned in the front or rear of the vehicle (we prefer to put it toward the front for easy serviceability).

high flow fuel filters for high-powered engines are a must, often these have design in mind and are of a high volume, replaceable filter element.
It is also important that a pre-filter be mounted to the fuel pick up in the tank. Such filters are designed with high high volume in mind and create very little / mild pressure drop.
The use of a pre-filter ensures long fuel pump life and can eliminate low flow conditions caused by debris entering the pump inlet and thus damage.

The fuel rail. The fuel rail should be consistent with, or larger than, the hose size. Additional capacity of a large-diameter fuel rail helps to ocillate / dampen the pulsations created by the fuel injectors and ensures even fuel delivery under all conditions. ( Remember to always have injectors secured! )

Boost controller : There are a number of different boost controllers out there on the market. Manual controllers aren't bad, because they tend to keep individuals away from
the temptation of ( increasing boost ) to a possibly risky level. All of the units I have used have been reliable. There are a number of different units, electronic or pneumatic you
can select. Most high end engine-management systems can actually control both boost / waste-gates.

Waste Gate Internal : These are typically common on most factory OEM units, you can identify such units as they are integrated into the turbo-charger-housing itself.
Usually smaller turbochargers low to medium pressure applications perfectly fine.

External Waste-Gates : External Waste Gates are physically not mounted to the turbo-charger itself. Furthermore these are mounted typically to a cast or tubular constructed
turbo-manifold. Depending on the application and mostly on high pressure systems I tend to prefer the external units. You don't ever want to question the units ability to control
pressure.

Waste Gate Size : This is a generic chart, if I recollect the first chart is what turbosmart recommends.
However, in reality there are a number of aspects specific to individual systems. These are helpful for
those who might have issues selecting a properly sized waste-gate.

big turbo/low boost = bigger wastegate

big turbo/high boost = smaller wastegate

small turbo/low boost = bigger wastegate

small turbo/high boost = smaller wastegate


One must consider , the flow of exhaust and the effect on how power is achieved. So, one could technically use a different chart.

big turbo/small engine/small power = small wastegate

big turbo/big engine/ small power = medium wastegate

big turbo/small engine/big power = big wastegate

small turbo/small engine/small power = small wastegate

small turbo/big engine/any power level = big wastegate " The concept behind this is that the small-esq turbine will attempt to overspin from excess exhaus gas volumes.

( Both charts are generalized slightly )


Atomespheric BOV : Location of blow off valves are very important. The most ideal location is as close as possible to the throttle. ( Especially on units that are non adjustable. )
In some applications, or if installed or placed or adjusted incorrectly you can encounter, poor throttle response, rich or lean Air fuel mixtures. In some application / situations a surge.
If venting to atomespher then I prefer at least a tunable / adjustable BOV. Still as close as possible to the throttle.

Re-Circulating System : Most highend modern machines, use such systems. Again location is still as close as possible to the throttle, and thus re-circulated / re-introduced into the
stream. Both boost is not wasted.

Regards,
Mick -

( I'll address intercoolers and so on later ) Sorry for the lag in editorial of my own posting.

This post has been edited by Micky_lovescelica_noise: Apr 14, 2012 - 5:09 PM