This site contains car modification and auto upgrade information specifically for the turbo import Toyota JZX90 MarkII TourerV, however the principles applied here can be mostly utilised regardless of the make or model of motor vehicle.
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1JZ Dump Pipe 26/3/2004
One of the most restrictive parts of the 1JZ exhaust system is the turbo dump which is a Y-Piece that combines the exhaust gases from each of the turbos. The stock piece is a cast iron unit, and due to the style of casting has a lot of flow restricting bulges that impede the gases from being extracted as efficiently as the otherwise could be. On top of this the flow of each turbo is badly angled and undoubtedly produces a lot of turbulence.
The item that I purchased to replace the stock restrictive item is a HPC coated Y-piece that has been custom made to provide better flow. I got this from Unique Autosports in Castle Hill.
At the time it was the only replacement item that I was aware of. Later I discovered a number of other dump pipes were being produced by other people and which provided an even better flow. There is alsways good info about this on the Australian Lexus Soarer Club site.
As you can see from the pictures the pipe looks the goods, and I was told that it would bolt straight up to the existing system. That way I could upgrade the exhaust at a later stage to get the best benefit. Unfortunately upon getting the dump home and unbolting the turbos and existing pipe, I discovered it was anything but a direct bolt on. (Arrrgh, should have known it was not like the Japanese parts).
So anyhow the dump certainly imporves the flow over the stock system, but there are better ones to get that have seperate pipes that run right down the car and can run into a full twin exhaust system, and others that seperate the wastegate gases to reduce power-robbing turbulence even more.
At least with this dump pipe, the exhaust gases are coaxed into the same direction and have allowed a small power improvement. I have heard up to 25kW improvements with some dumps (including full exhaust), and that is certainly nothing to scoff at. I have no idea what benefit these dumps have in reality as I did not do a back to back dyno comparison.
You can see that this pipe has the provision for the O2 sensor and at least bolts directly onto the outlets of the two turbos without any problems.
Before we can fit the new dump pipe, we need to remove the turbos of course. This is not an easy task as the bolts are not exactly in the most accessible places.
First the aluminium pipe from the outlet of the turbos is removed (not shown in pic). This is a matter of unbolting the two bolts on the compressor outlet of the front turboo, and loosing a hose clamp where the aluminium piping runs behind to the rear turbo. The intake pipe from the filter is then removed by loosening the clamps at the airbox and also at the aluminium intake pipe. The pipe is relatively flexible so it is not too difficult to remove.
The aluminium intake pipes are removed next and this requires unbolting from the compressor outlet flanges at both turbos as well as the pipe connecting the blow off valve and the breather pipe. It is best to loosen the four clamps holding the middle section also and any other small bits and pieces that are connected to the inlet piping. The rear turbo is particularly difficult to get to and requires a little patience and preferably rubber arms if you own then. (Small children are sometimes helpful in this situation)
You may also need to disconnect the water lines that are shown in this pic with the rag blocking them. This shot also reveals the turbo compressor wheel after the piping is removed. I was pleased to not that the compressor blades were in perfect condition.
The next step is to remove the heat shielding that surrounds the turbine housings of the turbos. This is simply a matter of removing a couple of bolts and delicately manipulating the shield to the right angle to allow you to extract it from the engine bay.
Here you can see the heat shielding lowered out of the way to reveal the turbine housings and the Y-Pipe. The far upper left pipe is the intake pipe to the rear compressor which has not yet been removed.
The second upper left pipe is the outlet from the rear turbo. At this point it is relatively clear where the bolts are to disconnect the trubos and manifolds from the motor. The lower bolts below the exhaust manifold are not visible and are rather difficult to get to. This will provide the majority of the heartache on this upgrade.
The first shot here shows you the front most lower manifold bolt. Unfoltunately it is necessary to remove all of the nuts holding this manifold on and completely extract the front turbo in order to enable removal of the Y-pipe. There are also the water lines and oil lines to disconnect before the turbo will come out.
The second shot shows the turbo assembly with all of the intake piping removed. It is advisable to place a clean rag into the outlets of each of the turbos so that no debris is accidently dropped into them. This is a saftey measure so as to not damage the turbos, and also will prevent you from needing to dismantle them completely (to get out that bloody little bolt that fell in! It has happened to people.)
Now we can go about removing the front turbo. It may be necessary to get under the car to see the bolt holding the turbo on near the underside of the manifold. This can be reached from the top, but locating it is a little diffcult. Again, patience and perseverence pays of in this task. It is not necessary to unbolt everything from the turbo. There is quite a bit of plumbing and bits an pieces that can remain on the turbo as you remove it.
These shot shows the front turbo when removed from the motor, and you can see the peripherals are all still attached.
This includes the water and oil lines and the wastegate actuator. Looking at the size of the port that enters into the turbo it seems obvious to me that a custom manifold would do wonders in improving the performance of the turbos. Unfortunately there are no such manifolds that I know of that are available to bolt on so a custom manifold would have to be made. Of course the stock turbos only have so much potential so a turbo upgrade is the logical step to take when seeking more power.
The pipe from the rear of the stock Y-Piece is removed, and you can see the comparison between the diameters here. This new piece was supposed to bolt on to the existing pipe shown, but it is clear that the holes do not line up. It would be disadvantageous to use mismatching sizes, however I was counting on them joining so that I could drive the car until I got a full exhaust system. As it turns out they were not going to match so I would need to get at least a custom pipe to the CAT.
The original Y-piece is removed by unbolting it from the rear turbo, and disconnecting the O2 sensor. You can see that the stock Y-piece and the custom Y-piece are considerably different not only in diameter size but in length and internal shape.
The stock pipe is extremely restrictive and has many interal bulges. These bulges were not unfortunately captured in the photos, but looking at this pair of pipes in the flesh it is obvious there are dramatic differences.
The outlet from the rear turbo is seen in this shot. You will notice that it was necessary to loosen the rear turbo in order to remove the cast Y-piece. Complete removal was not necessary however. Looking at the outlet of the turbo you can see the turbine wheel and the wastegate above it. The better of the dump pipes I discovered later have seperate pipes for these two outlets, and they are joing much further down the dump to reduce turbulence and increase flow.
We are now ready to install the new dump pipe. First ensure that all gasket surfaces are clean. I used a solvent called Cleansol which is usually used for cleaning a surface before painting. I then applied an even film of copper sealant to the faces of the gaskets. If the gaskets are in good condition like mine they can be re-used. If they are not in very good condition then it is worthwhile to replace them. It is much harder to replace them the next day after everything is bolted in and you realise there is a manifold leak!
Righto! So now the new dump is in place and beginning to be bolted up.
Refitting everything is as they say, a reversal of the dismantling process. Once the dump is in place and bolted to the rear turbo, bolt up the fron turbo and insert the O2 sensor and bolt it up too. I tend to attach eveything finger tight first and only tighten everything after it is all in place. That way eveything falls easily into place and requires less cursing and screaming.
I probably took too many photos of this but it looked so good (the shiny bit at least) that I wanted to get it at every angle. Unfortunately the heat shield covers it so it can't be seen when the bonnet is lifted, but that is also a good thing as everything keeps a stock look, even though performance is increased.
Here is a view from underneath the car looking up at the outlet of the new dump pipe. It was critical to ensure that there was nothing in the path of the outlet as I needed to drive the car to an exhaust shop.
Thats right, I drove the car some considerable distance with no exhaust system whatsoever. The car was surprisingly quiet. Not legal-quiet probably, but at idle and low throttle openings it was not at all offensive. Compared to the time I started my 13B RX7 with no exhaust (imagine 1000 giant sized, extremely angry bumblebees playing through a 5000W stereo and you get the idea) this volume was very docile. Surprisingly I even passed a highway patrol car who was parked on the opposite side of the road and he didn't turn to follow. (of course I passed him at 1/64th throttle!)
Anyhow, back to the topic at hand. Here I have reinstalled the heat shielding and am about to re-attach the intake pipes.
The second shot show the intake pipes re-attached and the only thing left to do is to connect the intake from the airbox, and the outlet pipe from the turbo outlet to the downpipe to the intercooler.
Unfortunately, even though there seemed to be no leaks when I started the car, it soon became evident that exhaust gasees were seeping out somewhere.
The next day I realised that I hadn't tightened one of the manifold flange bolts properly, and of course it had to be the most inaccessible bolt of all. Getting to this bolt was bot easy and even after I got a spanner to it I could not get any decent leverage.
Here you can see the measures I went to to make sure it was tight enough. A bit of rope attached to the appropriately sized spanner gave me surprisingly good leverage and enabled me to tighten the bolt very effectively.
Now the next time I remove these turbos it will definitely be to install a bigger single. Bring it on!
site
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RECENT MODS CHRONOLOGY
5-Jan-2007
Turbo pages and Headlights
I have recently added a new page about my single turbo conversion. There is a second page yet to come, but page one outlines some of the supporting components needed as well as the turbo itself.
Page 2 will be forthcoming where I detail the fitment of the turbo, manifold and wastegate.
I have also added a page for modifications to my headlights that should be very useful for owners of import vehicles.
25-Jan-2007
Site Revamp
Wow, it has been a very long time since I worked on the site, but now I
am in the process of redesigning it so stay tuned as I add some more content
and attempt to bring this project up to date.
18-Mar-2006
Car Changes
Lots has happened since my last update on upgrades to the car. For instance
the car is now running a 2JZ bottom end and the gearbox has been completely
rebuilt with a stage 1.5 shift kit, beefier clutches and a 2800 rpm stall convertor.
To say that this has transformed the car is an understatement. The car is now
torque heaven, and is an absolute pleasure to drive. The lag that was sadly
felt with the 2.5L motor is now completely gone with the 3L and the stally.
When I can find time to update the site with the process I went through I will
do so. I have many hundreds of pictures to add.
Whatever your vehicle is, whether it is a turbo car or NA or a Toyota or other manufacturer, I hope that the automotive information on this page is of benefit to you as you take the path of modification and upgrade on your car.
Toyota JZX90 MarkII TourerV.