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[How to] Custom fit the turbo of your choice

Wed Dec 19, 2007 4:35 am

Hopefully this can be a newbie resource for all those “can I put this turbo on my car” turbo questions. Maybe it can be stickied if it is good enough. This will give a basic outline of what is involved in fitting any turbo to the gen 2 3SGTE. If you want the most reliable car possible stick with the ct26 (stock turbo), ct27 (by ATSracing) or ct20b (st205 or late model mr2 sw20’s). These are the only turbos which are fully bolt on and reliable. Everything else can only come close. I urge anyone to consider the commercially available kits from ATSracing, KOracing, Berk technology etc before constructing a kit themselves. Unless you have a good knowledge and access to good fabrication skills you will most likely spend much more than the cost of a readily available kit or it will take you much more time, effort and you will have something much less reliable than you would like. Do not look at the price of the turbo itself and think that you are already half way there.

With the correct tools, design, plan you can easily make a very good, cost effective, reliable and well performing turbo kit. Here are some of the areas which need to be addressed.

1. Get the turbo you plan to use. I wont discuss how to decide on a turbo other than recommending you- firstly decide your power goals by riding in other peoples cars, studying their dyno’s and learning to read turbine and compressor maps. I would recommend a T3 flanged turbo as these tend to be the most common flange design- many Nissan cars come stock with this flange, Garrett, Turbonetics and many other turbo manufacturers have a huge range in this form. This makes later swapping a simple bolt on process.

2. Once you have your turbo you will somehow need to attach it to the stock exhaust manifold. Options include buying a new manifold. Unfortunately most manifolds are only available with the ct26 twin entry turbo flange / pattern and will not help in the fitment of another turbo flange at all. Also all of them are tubular which frequently cracks. If you have chosen a T3 flanged turbo you can get a tubular “Fullrace” manifold which has a T3 or T4 (I think) flange and lifetime warrantee against cracking. These are very expensive and half the cost of a commercial kit. SSAC also make a T3 tubular manifold but this is likely to be poorly constructed but can always be reinforced and or redesigned slightly.

Here are some adaptors and fitment pics. They are all for a T3 flange, mostly undivided.
The Ebay special- doesn't fit.

ATS racing

Ebay special from Ebay Australia - no wastegate port so it can be added properly

From somewhere in Canada. Divided design.

Custom 1 off from a mr2 owner. 90 degree bend- kind of a top mount design.

ATS design fitted. Hole provided for own wastegate fabrication.

And again fitted to stock manifold

The stock exhaust manifold is cast log style. It is very very reliable and has shown to flow the exact same as any tubular manifold at the 500whp level so it makes sense to use it. This can be done by constructing an adaptor plate to bolt to the original manifold and provide the flange for your chosen turbo. These can be purchased from ATSracing or on ebay. The ebay ones are designed with the gen 3 engine in mind and place the wastegate flange into the oil filter on gen 2’s and the compressor housing very close to or fouling on the clutch lines. They will require work to fit despite claiming they are for gen2’s. The other option is to make one. You will need to have the ct26 flange and the new flange for your turbo water or laser cut and welded together.

If using an external wastegate it will be necessary to factor this into the design of your adaptor. Flanges can be welded to the cast iron exhaust manifold however they will eventually crack off due to the different co-efficient’s of expansion of the two different metals. The best way is to have the flange welded to your adaptor. The closer the wastegate to the exhaust gas path the better your boost control will be. Internally gated turbo's are generally simpler to work with in this respect however external wastegate’s are often but not always superior in boost control.

3. The next issue is the downpipe. The ct26 downpipe stock or otherwise is only compatible within this Toyota subfamily of turbo’s. You will need to have the flange changed or make a whole new downpipe from scratch as you will not be able to purchase one. 3” is usually best. A support bracket for the downpipe should be made to prevent cracking and help support the turbo. A flange for the O2 sensor needs to be fabricated, drilled, tapped and welded onto the downpipe. Any external wastegate can be routed into the downpipe keeping noise levels low while at full boost and exiting exhaust gases properly. This will add cost. Any exhaust shop can make a new downpipe but will most likely require you provide a gasket for your turbo so the downpipe flange can be custom cut.

O2 sensor flange required.

4. The next problem is routing the compressor housing to the intercooler. If you have already done a front mount intercooler this will be nothing new. If using some sort of top mount stock (air to air- unadvisable) or otherwise simple silicon joiners and short stainless sections can be used in combination. Mild steel should not be used as rust is not your engines best friend.

Turbo's can be clocked (rotated) to point in the direction required. This T3/T4 can have its compressor housing turned by undoing the blue circled bolts turning it and doing them up again. Similarly for the green bolts for the turbine housing- this should be altered first as it changes the compressor orientation.

5. The stock intake is unlikely to work with any aftermarket turbo. If you already have a custom intake then altering it should be quick and easy. Otherewise a custom bracket to mount the air flow meter, a pipe with nipples for the PCV and throttle body, a pod filter of some description and various joiners will be required.

A new intake is needed

6. The next problem is oil. The stock oil feed and drain are incompatible with everything. The oil feed is high pressure, the oil drain low pressure and both high temperature. The oil drain can see oil temperatures over 120 degrees Celsius. Any poor design in the feed can see burning hot oil spraying everywhere catching fire and burning you car down. Any drain inadequacy can see oil loss leading to run (destroyed) bearings etc and the need for a rebuilt or new engine.

Oil feeds can be made either using stainless steel braided teflon hose with proper flare or otherwise fittings. “Earls” fittings are very good, very expensive and reliable. Hardline can also be used, also requiring proper flare fittings but considerably cheaper. Flare fittings come as 45 degree and 37.5 degree- they must be matched. I am using 45 but 37.5 is more common in the US apparently. You will need the tools to flare any hardline properly. The stock banjo bolt for the oil feed happens to have the same thread and pitch as the transmission fill and drain bolts. Therefore the cheapest option is to have a transmission bolt tapped and drilled for the flare fitting you will be using- 1/8 NPT is a good choice (NPT is an American? standard of tapered thread; BSP-T is British standard pipe taper and is another option). Many aftermarket turbos have been tapped for 1/8 NPT oil feeds. You will need a flare fitting for this end also.

Oil drains can be constructed in exactly the same way however since they are low pressure a third option of rubber hose is available. This must be oil proof as normal rubbers will be dissolved and must be able to withstand very high temperatures. I personally am using a tar hose suitable up to 177 degrees C. The oil drain needs to be as large as possible. Preferably 3/4” (12- or 12AN) internal diameter or bigger. It should never go lower than the sump, can be as vertical as necessary but must be slightly angled down at all times along its path. An adaptor for the sump will be needed if any size other than the stock 22mm (7/8”) is used. The thread is M28 x 1.5 and anyone with a lathe should be able to make one. The CHRA should be vertical so that oil flows in through the top and out the bottom. A slightly angle will not matter if it is unavoidable.

Turbos need 1.6-2.0L of oil per minute if they are sleeve (journal) bearing. Ball bearing turbos require less oil- around 1.0L per minute. Any more and you may blow your turbo seals prematurely and smoke. Any less and you risk destroying the CHRA (core / internal cartridge / bearings) and the turbo will require rebuilding. The oil flow is dependent on the oil feed. 3AN (3/16th’s or ~5mm) is a good size to start. Some use 4AN but can provide too much oil. To measure it, prevent the turbo from spinning so as to not cause damage, remove the feed line and put it into a measuring jug, start the engine and measure how much you get after 10-15 seconds and multiply it by 6 or 4 respectively. If it is too great a restrictor can be placed in the line. Some people have found that a restriction as small as 1.4mm is required to get the flow down to an acceptable level.

7. Many aftermarket turbo’s do not require water lines. Water jacketed turbo’s don’t require cooling down and are at a much lower risk of coking up with oil. Stock water lines can be removed, capped at the bypass line and a new straight radiator hose used without the stock metal bend in it. If water lines are to be used then high temp water hose can be used and a custom pipe in the radiator hose will need to be made.

Custom water lines... yes its a ct26 still.

8. Any turbo should be adequately braced. It is probably not necessary but can not do any harm. A bracket can be made to incorporate the stock turbo brace or a completely new one can be made either using its holes on the block or the holes used for the stock downpipe support.

Designing a kit is much more involved than this but this is a general idea what is required. I in the process of doing this myself with a 50 trim t3/t4 and will post pics of the parts I make after I have finished it in a few months. Any corrections let me know and I will change it.
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Wed Dec 19, 2007 1:36 pm

Good info.
After the mistake I made with my current turbo kit, I know the down side of a DIY turbokit.
I had the kit made by a tuning shop here.

The EVOIII Big 16G is not a bad turbo. It is about the same as the CT20b, but new. I have had this kit on my car for 1 year now(20 000 km). In this time I needed to have the adapter fixed 2 times from cracking. Actualy It is cracked now for the 3rd time, but I expect my new kit in Januari. It is not pretty.
Other than that, this current turbo is not getting me to my goal(300fly hp) at the boostpressure I want(15psi).

So after having the turbo off the car several times in one year, and it looking like crap, I decided to spend some cash and bought an KO SB kit.
It looks awesome, the turbo has newer technologie than the EVOIII and It should not crap out on me.

Wed Dec 19, 2007 6:25 pm

Good buy, I imagine you will be very happy. I personally think their kits are the nicest in terms of quality from what I have seen. I am essentially making myself the equivalent of a SB50 kit.

I saw the thread on mr2oc with the ct and evo side by side and they definitely aren't 100hp apart in terms of size.
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