Budget Turbo Hayabusa Build

[horndog]

Hi Guys, I have finally finished building up my own turbo kit for my 2003 Hayabusa.

A bit of history on the driving factors of the build;

I bought the Busa about halfway through the last drag race season as I knew I was hooked on the 1/4 mile and the 03 R1 wasnt going to be the best base to work from. I put about 50 runs on the Busa and ran my fastest time of 10.124 after putting an intake cam on the exhaust side of the engine. At the end of the season I was planning to put a set of high comp pistons in the bike but knew I wasnt going to be happy with that so decided to build my own turbo kit up to get the bike boosted for the lowest cost possible.

Where to Start?

PLENUM
I did not have the money for the turbo yet so started off with designing the plenum and getting a mate to make it out of aluminium for me. I asked around the Aussie Hayabusa forum and found some plans for various turbo plenums but nothing really that I was happy with so I decided to go from scratch and mock up my own out of tin first.

The first attempt was a write off and number two was looking better. The third attempt was more like what I was after and so then looked at being able to make it from 2 pieces to need less welding. I had the advantage of getting my hands on CAD and taught myself the basics of creating a 3D design then flattened it out to 2 pieces for bending up and welding up. I would print out the designs in 1:1 scale on paper and sit them together to make sure the angles were all good and also the holes lined up with the throttle bodies.

Once I was happy with that I mocked it up in tin agakn to make sure it was right and then handed it off to Tony for welding up. Once the build was nearing completion I tapped a thead into the underside of the plenum where Tony had welded in an extra bit of plate and mounted an air fitting for the wastegate and boost controller feed. I sourced some silicone pipe from a local auto shop and bought some T-Bar clamps off the net to secure the plenum to the throttle bodies.

The plenum was made from 3mm aluminium plate.

Plenum Complete

[horndog]

This is a critical factor (Duh!) but also the most difficult decision to make on what turbo to get. Once you start looking at whats out there you will quickly learn that there is alot to learn and a lot of opinions out there on what is best.

After many weeks of going in circles and studying compressor maps and learning A/R housing sizes etc. I was almost about to buy a Mitsubishi turbo or a cheaper knock off but thought better of it and deffered my purchase until I had enough coin to buy a Garrett turbo.

Speaking to some of the guys who are racing and street riding with turbo Busa's it became clear to me that my limiting factors in the short term was going to be the bikes injectors and the gearbox and engine internals ability to deal with the horsepower I threw at it. The injectors are only good for about 260hp and alot of opinions said that once you go past 300hp you need to throw alot more coin at the engine in terms of rods, pistons, undercut dogs, intercooler and water injection so I figured that a max of 300hp was my target. This would help me refine the turbo search down and also let me keep the lag down for the 1/4 mile.

The final decision was a Garrett GT2860R with a 0.60 A/R compressor housing and a 0.60 A/R Turbine housing. These turbos come with an internal wastegate which is too small to prevent boost creep so once I got it I would have to port the wastegate on the turbine housing. THe turbo is supposed to be good for 300HP and is a ball bearing unit to give a better spool up. I searched around and found that the best deal I could get was from MTQ engine services so once the money was together the call went in and the turbo was delivered.

[horndog]

Now Ive got a turbo, its time to make the headers. The critical factor here is to make sure that the turbo is mounted high enough to allow for the oil to drain away from the turbo without the need for a scavenge pump. Basically where the oil exits the turbo, the turbo needs to be higher than the oil level of the sump.

If you put a levelled straight edge from the sight glass level to the front of the engine and make a mark and thats your absolute lowest level of the oil exit from the turbo. It is so close that you cant sit the bike on a rear race stand as oil will make its way into the housings and make a great smoke screen, foul plugs and spray oil everywhere out of the exhaust.

I made a jig negative which was some plate to mount across the exhaust flanges on the head and then welded on some threaded rod. I then welded some threaded rod onto a nut and put that onto the first bit of rod of the head flanges so I could adjust the turbo height while it hung off my jig negative. This was to ensure the right height and clearances before locking it all up and making up the header jig and finally the headers. (confused yet?) Look at the pic and it will make more sense.

Once the jig negative was done I made the positive and bored the holes for the header pipes. I then got some mandrel bends and started working out angles and where to cut the bends to make them all collect in nicely to a water cut flange which I bought off ebay. This was a real mission and although I am sure there are smarter ways to do it, I manged to fumble my way through it to something that resembled some headers. I welded it all up with a mig using 1.1mm flux core wire.

I then had a bit of an idea and decided to cut the tapered spigots off the original headers and reused them and the 2 bolt flanges on my new headers which saved me a few bucks.

[horndog]

Oil Feed and Drain

The oil feed and drain set up is relatively straight forward only you must know that if you are using a ball bearing turbo you will need to restrict the oil flow to the turbo as they require much less oil than a plain bearing turbo. To do this I silver soldered the hole up on one of the adapters from the oil supply t-piece to the turbo and re-drilled it to a 2mm hole.

I tapped my oil supply to the turbo by fitting in the aforementioned t-piece where the oil pressure sender screws into the engine from there you screw an adapter into the t-piece to convert it to a tapered seat oil fitting which the supply hose screws onto. I found there was very little information about thread sizes for the Garret turbo oil lines but eventually found an e-bay seller who manufactured my feed line to my desired length and also supplied a banjo fitting to screw on to the turbo end which makes it a lot easier and neater to fit. Alternatively you can go to someone like Enzed to make a hose for you but you will pay more.

The oil return line is a 5/8 id hydraulic hose which has a flange that bolts to the turbo and the other end needs to be mated into the sump. I think I went the wrong way here and bolted the flange to the sump and drilled a hole in the side of the sump. What I should have done was used a bulkhead type fitting from speedflow or earls or similar. My flange fit up has worked but the bulk head fitting is much easier to fit. The oil return can go anywhere on the sump and does not have to be above the oil level of the sump. I also made sure it wasn’t going to stick out lower than the lowest part of the sump to be vulnerable to a ground strike if I backed off a wheelie too hard.

Exhaust

Because I am only drag racing the bike, the exhaust is only going to be long enough to have a spot to mount up the wastegate and to get the exhaust away from the bike. All up the full length is in the ball park of 300 – 400mm. I stuffed around for a while measuring from the turbo dump flange to the fairing and tried to get an idea of angle of bend required and called up Tony to supply me with some stainless pipe for the dump and exhaust pipes. The exhaust is 52mm OD and the dump is around 25mm OD I think.

Once I got my hands on the pipe (already bent up for me) I worked out the exhaust section first and tacked welded it the flange I picked up off ebay. Now comes the hard bit(for me anyway) I had to work out how to get the waste gate mounted up without interfering with any other part of the bike and also so the dump pipe coming off the waste gate ran out on top of the exhaust and looked nice and neat. It took a bit of stuffing around and measuring but I managed to work out the angles so it all lined up nicely.

Whilst doing this, something dawned on me about working with pipe and cutting angles and having them all line up nicely without gaps and over or under hang. I might be stating the obvious here but it was a new thing to me. If you want to have a piece of pipe cut and welded to a 45-degree angle, then you cut a 22.5-degree angle and rotate on piece around the other until the desired angle is achieved. Because the 2 pieces originated from the one cut, they will always mate up perfectly. If you cut a 22.5 degree angle and then later on try to cut another piece to the same angle, chances are you wont be exactly right on the next cut and the bits wont line up as good.

Anyway the exhaust was now finished and I tacked the bits together from the inside with my mig using steel wire and then sent it off to Tony for Tigging up properly with stainless rod.

[chief wiggum]

fuck yeah! this looks good, nice effort

[chee]

sweet dude!

[Hewie]

Good work .. keep the info coming.

[Cam]

Groovy thread, nice work mate.

[Xuaxace]

That is really impressive stuff! good write up so far .

[horndog]

I posted the Oil Feed and Drain & Exhaust up above after the headers post. I will probably do the fuel system next.

[horndog]

I reflashed my stock ECU last night, I programmed in a 2 step launch control by lowering the neutral rev limit. Makes 1psi of boost at 5k rpm on the limiter and 100% throttle due to the extra fuel driving the turbo like a jet. I will richen the neutral fuel map up more and try to get around 3psi of boost at launch.

Also removed 6th gear speed limit, extended geared rev limit and remapped fuel maps for turbo.

This is all on a stock ECU, no expensive add ons!

I can remove 6th gear speed limits on gen1 busas and more now for anyone who is interested. Just need the ECU to reflash it.