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Frequently Asked Questions Back

General Questions
Camshaft Questions
General Top

Q. My new turbo is installed, now what?
A. Before starting the motor, it is important to get an adequate supply of oil through the turbo. To do this, disable the ignition or injectors (different for various cars) so the car is able to crank without firing. Crank the motor over for 30-45 seconds in 10 second intervals. This will pre-oil the turbo, and prevent premature thrust bearing failure.
Q. What's the difference between 6cm2, 7cm2, and 8cm2 turbine housings?
A. Contrary to what your friend told you, a 7cm2 turbine housing does not have an inlet that is 7cm across. The 6cm2, 7cm2, and 8cm2 designations given to Mitsubishi turbine housings refer to the area of the cross section of the housing, known as the nozle area. In unported form, the 6cm2 and 8cm2 turbine housings have a 54mm "step bore" inlet, and the 7cm2 housing has a 60mm step bore inlet. When porting any of these housings, the step is removed, and the turbine housing is matched to a standard 7cm gasket, which has an opening that is 60mm in diameter. When porting your turbine housing, it is a good idea to port your exhaust manifold to 60mm as well.
Q. What's the difference between internal and external wastegates?
A. Internal wastegates are comprised of a flapper door which is built in the turbine housing, usually operated pneumatically by a mechanical actuator. These flapper doors are limited in size, but work well in certain applications. Usually found in smaller turbos, internal wastegates are relatively inexpensive, simple in design, and very durable. Larger turbo can be fitted with internal wastegates, but boost control can be tricky. If you are looking to run high boost (20+ psi) all the time, then an internal gate may be fine. If you are looking to run lower boost levels, you will need an external wastegate.

External wastegates are generally mounted to the exhaust manifold or to the O2 housing, and are self contained units. External wastegates have the ability to bypass large amounts of air, and can provide steady boost control at any pressure level. A common myth is that in order to run higher boost pressures, you need a larger wastegate. This is incorrect. Larger wastegates are necessary to run low boost levels on large turbos.
Q. I just bought Turbo-X, how much boost can I run?
A. This is a question we cannot answer for you. The amount of boost your car can handle is dependant on the rest of your setup, as every car has different flow properties and fuel capabilites. The best advice is to start low (10-15psi) and work your way up, paying close attention to your air/fuel and EGT gauges (you DO have these, right?).
Q. What are twin scroll or divided inlet turbine housings? What are the benefits of using a twin scroll turbo?
A. A "twin scroll" or "divided inlet" means that there are two separate volutes within the turbine housing. The main reason for doing this is to isolate the pulses coming from each exhaust port and maintain more of the pulse energy from each cylinder all the way down to the turbine wheel. There are no differences between the turbine wheels used in open or single inlet turbines compared to those used in twin or divided inlet turbines.

Generally speaking, a divided inlet turbine setup will respond faster and produce boost quicker than single or open design of the same nozzle area, of course this is dependent upon proper execution. The simple fact that a divided housing is used does not guarantee these results.

While it does not cause any problems or harm to run a divided inlet turbine housing on a manifold that is an "open" design, none of the benefits of the twin inlet will be seen.

Q. Why do people say it's not good to get oil feed for the turbo off the cylinder head? Should I use a filter on my oil supply line to my turbo?
A. There are plenty of people who have oiled their turbo off the head and not had any problems, there are just as many if not more that have done it and had recurring turbo failure that was only vaguely described by the repair shop as "poor lubrication".

Oil pressure in the cylinder head on a stock 4G63 engine can be less than 5psi at times, while this may be enough oil for a factory 14b, T25 or even 20g it isn't enough to feed the high volume oil passages of the modified thrust setup in your FPGreen or FPRed model turbo. The Garrett severe duty 360 thrust setups also have an increased appetite for lubrication. Think twice before feeding either of these type turbos from the head.

Remember that you aren't just trying to keep some oil on the bearing, you are trying to float one piece of metal above another piece of metal on a pressurized film of oil, and at the same time keep the whole mess cool enough not to melt. A constant high volume stream of oil does just that, a measly trickle will send you back to the turbo shop.

One exception to this is the Ballistic Concepts Ball Bearing CHRA from Garrett. These turbochargers are totally different internally. Their operation is actually impeded by too much oil. It is fine to supply these turbos with oil from the head. In fact the oil line we offer comes from the head and features a .8mm orifice to restrict the oil flow to the turbo . These turbos require water cooling in the absence of the typical high volume of oil that would normally provide stable temperatures.

As far as filters go, you're damned if you do and you're damned if you don't. You shouldn't need one in your oil line. Failures occur due to dirt/grit in the oil making it into the turbocharger. Failures also occur due to plugged filters. We have seen it both ways. If you are going to use a filter, check it often. The most important thing you can do to avoid oil contamination of you turbo is to THUROUGHLY wash everything more than once before assembling your engine. Avoid sandblasting anything that goes inside or onto the engine. Specifically avoid sandblasting your valve cover. If you suspect that the machine shop that did your valve job sandblasted your head then make sure you remove the 4 plugs from each end of the head that cover the ends of the oil gallies and wash the gallies out with HOT SOAPY WATER. If you do this you will be amazed at what comes out of your beautifully machined freshly rebuilt head.

If you think all that is a bunch of crap, at least spin the engine over to prime the oil system without the turbo attached so that anything in the gallies has a chance to flush out instead of flush into your new turbo.

Q. The shaft in my turbo feels loose. How much freeplay should I have?
A. While this specification does vary from one brand to another and rule of thumb is less than .030" radial freeplay and less that .002" axial freeplay.

This amount of freeplay is required to allow the bearings to "float" in a pressurized film of oil while the engine is running. The flow of oil through the clearance around the bearings is what helps the bearings stay cool. This oil film around the bearings also help dampen vibrations that occur to the rotating assembly as it moves through it range of RPM. Ball bearing turbochargers do not have this pressurized film of oil around the bearings; this is why they are somewhat more noisy than floating journal bearing turbos.

Q. My turbo is smoking and it's brand new. The shaft has normal play in it so is one of my seals blown?
A. The term "blown seal" is widely used to describe a turbo that has oil coming out of it. In reality a turbocharger seal cannot become damaged until the freeplay of the shaft has increased to the point where the blades of the turbocharger have been rubbing against the housings. Blade contact usually requires more than .035" of side to side movement of the shaft. In some cases it is even possible to rub the blades and still not damage the seals.

If the turbo is new and the shaft isn't loose and bouncing off the housings, but oil is coming out of it chances are you can correct the problem without even taking the turbo back off the car.

The seals within the turbo are not meant to hold back a bearing housing that has become full of oil. They are designed to sling the oil mist and spray within the bearing housing away from the point where the shaft comes out each end. If the bearing housing becomes full of oil it will ooze out past even brand new seal rings.

The oil should freely drain out of the bearing housing as quickly as the engine supplies it. This is why the drain tube is so much larger than the supply tube. Gravity is the only force moving the oil out of the turbocharger. Any slight restriction in the oil drain tube, even a small silicone dingle berry, can slightly impede the draining of the oil and cause oil to back up into the bearing housing.

The crankcase vents are the second largest cause of oil loss from a good condition turbocharger. The seals in the turbocharger were designed with expectation that the pressure inside the compressor and turbine housing will always be greater than the pressure in the bearing housing. If this is ever not the case then oil will come out pass the seals. A restricted crankcase vent will cause this to happen. If the amount of ring blowby exceeds the ability of the crank vents to release the pressure positive pressure will build within the crankcase. This pressure within the crankcase can exceed the pressure inside the compressor and turbine housings under some operating conditions resulting in oil being driven pass the seals by the improperly biased pressure gradient across the seal rings. In severe cases it may be necessary to introduce vacuum pumps to deal with crankcase pressure, but these would be very severe high boost applications where even low percentages of blowby produce a high volume of crankcase vent flow.

Camshafts Top

Q. Forced Performance "X" grinds have been on the market for several months now, and I still haven't seen much posted about them.
A. I'm not sure what to say about them that isn't on the website. They are exactly like the normal cam with a cunt hair more valve acceleration and dwell time near max lift. They act pretty much just like the base cam, they just move more air with the same set of basic characteristic of the parent camshaft at the expense of using up a little more valve spring tension. Turbos spool earlier and torque is greater this way. Basically if you thought you wanted 1's, you probably want the 1x's and if you thought you wanted the 2's you probably want the 2x's. Just buck up and follow the spring recommendations.
Q. I see that for the 1x it lists only upgraded springs but for all the other X's it lists dual upgraded springs required. Are the single crowers enough to safely run FP1x's
A. Affirmative. Any upgraded single springs are strong enough for the 1x cams. Oh also, the website lists them higher price than the normal cams, but that isn’t correct. If you call and order them, they are all the same price. There is no extra charge for the extra acceleration.
Q. I see. Sounds like a no brainer, better spool and torque and no downside. I see 1x's in my future!
A. Pretty much, so long as you have the correct spring tension there is no downside. You ask yourself, "self, why are there 1 and 2 if the 1x and 2x are better?" then you realize, some people need to cam up engines with stock springs in them, and that is good. People with stock springs deserve to have some cam grinds too! Of course, people with better springs, deserve better lobes, so there you have it.
Q. Robert, I've got to say that so far, I'm impressed with the air flow numbers I'm getting with the FP3 cams in my 2.0L. The "X" cams weren't listed when I bought mine though. :( I'm right at 60 lbs/min, 8188rpm, 29 psi on the GT35r/header AMS kit and Magnus 2G head. What I haven't found is what redline I should go for. Marco put in the Supertech valves and springs with Ti hardware so I'm thinking at least 8500 but maybe higher??? Most people run these cams in strokers & I'm not finding much data when used in 2.0L. Am I safe to rev 9000 on these since they aren't the "X" grind?
A. If you have the Dual ST springs, then you are cool to 9krpm with all the cams thru the 4 and even the larger 3x. Keep in mind that installing the springs at a shorter height will get you extra nose pressure and extend RPM range. We recommend installing the springs at 1.500 or shorter.
Q. The "X" cams weren't listed when I bought mine though, what gives?
A. They (3X) have been a royal pain in the ass. Comp ate $10000 worth of cams because the lobe centers were screwy and the lobe profile didn't fit on the cam blanks as they had been previously made. All that is fixed now. The X lobes are all about getting the valve above .150"-.200" lift quicker than anything else commonly available out there. If you check the duration numbers at .200"-.400" there is nothing else out there even close, this is where the power picks up- low seat duration, high valve open duration. The 3x are now in stock, I dunno if the website will let you order them online, so call if you want them and can't grab them off the website.
Q. So I decided to go with FP1x's. I'm running Crower Ti pieces and SS valves. How high can I safely rev the engine? I have previously contacted someone at crower about which FP cams I could use with their springs. They stated that since their springs/retainers can handle 9500rpms on their 414's they see no reason why you could not go to the same RPM safely with a cam that is smaller.
A. The FP X series cams have extremely radical ramp rates. High ramp rates do not show up on cam cards. On a cam card the 414 looks like a more radical cam the FP3. If you were to make this assumption you would be very wrong. You should take the advice of the cam maker NOT the spring maker. Forced Performance has spring recommendations listed in the cam descriptions. I would be hesitant to rev an X series cam much above 9K, even with good springs, Crowers or any other single spring are not what I'd call 'good springs', spring rate and ability to shim for seat pressure and still have .450" lift before coil bind isn't as good as some others. The X are fucking brutal compared to the norm. If you want 10krpm then you need to set your spring pressure over the nose of the cam to 300lb, or pick a camshaft with a more conventional profile. The intended application is a broad torque curve 2.3/2.4L, but they work good on 2.0L too especially at higher RPM (5500+), but you better be on top of things in the valve train department. Stock rev limit isn't anything to worry about, valve train issues with this design predominately show up at the very high end of the rev range, well above factory rev limit, because everything is relatively stiff and high frequency.
Q. My cam cards came with a different center line and grind number than they have listed on the website. I've contacted them about what the difference means and will post up my cam card if anyone cares to see it.
A. Some of the cam cards were printed with early prototype specs on them. These incorrect cards made it into some of the first cams sold. The spec cards on the website are correct and match the actual profile of the camshaft.
Q. Do you have any dyno numbers on the FP3 cams in a 2.0l?
A. Major car specs:

36psi dropping to 32psi
'95 TSi AWD.
2.0L 6 bolt, Ross/Manley.
Magnus 2G head, SMIM, +1mm Supertech valve train, FP3 cams.
AMS GT35r kit w/ AMS header, Navistar FMIC.
DSMLink w/ 1600cc injectors, -6 AN fuel system.


Forced Performance Turbochargers, 671 New Hope Road West, McKinney, TX 75071 - Tel: (972) 984-1800
  © 2009 Forced Performance, Inc.
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