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ZXR750 turbo conversion


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I've wanted to turbo something for yonks and since I only managed one track day last year I thought I'd strap one in the ZXR.


Here's what I started with:

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The handling is great on this thing, the brakes are alright and I don't particularly like the fairings so I'll go naked and maybe do something about the brakes if needed.


I'd already spent a load of time tuning the engine - it's got a snazzy exhaust, the clean air system went in the bin and I've fiddled plenty with the fuelling to give me a respectable 109bhp.

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My aim is to keep the engine internals standard and lower the compression ratio slightly so I can run low boost and retain road usability. I'm aiming to run 7 or 8 psi which should give me around the 160bhp mark.


I started off by stripping the bike down: IMAG0550_1.thumb.jpg.20a651c527c456247f6347ecbb00c473.jpg

I already prefer the way it looks!

Engine out:

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I did some basic checks on the engine - compression and stuff and all looked well. There was some gank on the back of the inlet valves which needed a scrape and the valve stem seals probably needed replacing so I ordered a good full gasket set and started stripping down.

 

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The combustion chambers looked alright but I gave them a good clean up anyway. I noticed one of the inlet valves was slightly corroded around the rim so I replaced it and lapped the rest in.


I realise now that I failed to take any more pictures of the rebuild so slappy wrists for me. Anyway, everything was disassembled, cleaned, checked, measured and repaired/replaced where necessary. I even went so far as to balance up the piston/conrod combos (because I'm sad like that). :-) I also turned down some aluminium rod and hammered it down the exhaust emission tubes to fully block them off.


The standard compression ratio is 10.8:1 which is a bit high for turbo stuff. I've done loads of reading around this (highly recommend Maximum Boost by Corky Bell) and that's a bit high so I doubled up the base gasket to lower me to 9.8:1 which is better.


Running boost is all about the balance of a number of variables to avoid detonation which is where the air/fuel mixture in the chamber is ignited too early and maximum cylinder pressure occurs before TDC. This causes "pinking" and motor knackerage.


As boost levels rise, the ignition timing must be retarded to avoid detonation so I bought a ritzy programmable ignition unit from Ignitech along with a lambda sensor module and MAP sensor. All in this lot cost me about £360. From anyone else it would be the thick end of a grand and so far it's been very easy to use - even for a computer idiot like me!


Because I'm running carbs I also needed a boost referenced fuel system that would supply fuel to the bowls at x PSI above boost pressure so fuel would always be able to get in to the bowls so I got a Malpassi regulator and a generic EFI fuel pump. I measured the pressure of the OEM pump at 3PSI so set the base pressure on the Malpassi unit to that.


I hindsight, now that I've had a test run of the pump, I wish I'd got a pump from an EFI tank and welded it in to my current tank. It would have been a bit of a pain but would have tidied everything up and the generic one I have is a bit noisy.


I had to do some wiring stuff anyway so took the opportunity to go through the loom and remove bits I didn't need such as the lights and chose to hard-wire in the connections for the new ECU - it came with a converter for the original loom but I want to keep everything to a minimum.


I spent ages looking for a place for the fuel pump and finally decided the only good place for it would be where the starter relay was and the rest of the relays used to be. This meant undoing some of the wiring I'd just done and shifting the starter relay:


It's only a test fit but it had to be far enough back to avoid shit being thrown up from the road:

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You can also see the new regulator hanging off the carb rail - again, the product of much head scratching. The new ECU is top right too.


Now that's all sorted, I "just" need to figure out where the turbo is going to go and fabricate some headers, sort the oil feed/return and make up a plenum and connect it all up.


I'll try and keep this updated as I go along and feel free to give me a shout of anything I've missed or if you've got any hints or solutions to stuff.


Cheers,

Fro

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After watching the worlds fastest indian recently, I now imagine Mr Fro as the modern day Burt Munro :mrgreen:.


Quality stuff this mate, really interesting!


The owner of the garage I used recently had a baby blade that he'd turbo'd, he stuck an intercooler in the tail I wasn't really sure how that works :scratch:. Will yours need an intercooler, if so where's that going? :lol:

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I think my budget might be sliiiightly lower than the Martek!


I want to use an intercooler so I can run higher boost but finding a place for one is really difficult. As it is I'm going to have to get a shorter radiator (anyone got the measurements for an R1 rad?).

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An Audi TT intercooler might work: http://assets.suredone.com/1517/media-photos/cp026000-lh-turbo-intercooler-audi-tt-mk1-18t-225-hp-genuine-oe-8l9-145-805-2.jpg

If I can make enough space I thought it might fit underneath the engine with a scoop to direct air in to it. Either that or run a long one up the side of the rad but I don't like that idea much.


I'm all ears if someone had a solution! :-)

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*adds Fro to the banned list*

Bovvad.


I'm thinking matte tank, mudguards and panels with gloss frame and lettering. That might be some way down the road...

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An Audi TT intercooler might work

 


Dont limit yourself to a TT intercooler


there is a lot of VAG cars that use the same or similar sized intercoolers :wink:


I have not long ago scrapped one off an A4 that you could have had :x

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Oh, right, I didn't realise - I thought they were TT specific. That's why they're only £15-20 a pop then. :-)


Before I settled on naked I was planning on putting it in the nose cone. I'll still offer it up but I reckon it'll look shit.

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yeah the audi a4 b6 is the same shape (2001-2004) also the b7 too (2005-2007)


The same year passats should be the same too also the bora and probably golf and audi a3 :)


but if you are seeing them for £15 - £20 thats a good price

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I noticed that when I was after one some years ago


there was loads darn sarf :lol:


usually chavs sticking bigger ones on and running 1.9 tdi's at close to 350 horses!

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Not a huge amount has happened in turbo land lately.


I rigged up the fuel system which as well as the referenced regulator needs a return line to the tank. Luckily I had two outlets on the tank to play with so I'm using the "on" feed as the regulator return and "reserve" as the pump feed. This of course means I won't have any warning before I run out of fuel. :shock:


I cut and bent up some aluminium sheet to form brackets for the ECU and fuel pump:

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Then I chopped up the ZX10 headers and started to loose fit them - slight problem was that the studs on the ZX10 are closer together than the ZXR so I had to machine the holes out a bit to make them fit:

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I'm a bit stuck now - I've ordered the stuff I need to TIG the titanium headers but to keep costs down I've had to get a few bits from China which could take a couple of weeks.


I need to measure up for the intake plenum too. I'm wondering if I can [strikeout]con[/strikeout] entice a BTEC bod at school in to machining out the carb block if I draw them up in CAD...

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  • 3 weeks later...

I got frustrated with nothing happening with this and bored waiting for stuff to come from China so started work on a set of headers.


I had a poke about my steel stock and magically turned up exactly the right diameter tube. So I started hacking some bits up:

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Here's some of the bits used to make it up - mainly 15 degree cuts to make the 90 degree bends.

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This is one side. I've welded up the head flanges and first set of bends then started tacking things together. I knocked up a bracing thing which bolts to the bench so I can get the tubing in the right position prior to welding.

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I did loads of trial fits on the bike and had to make some corrections. I finished up the main part and have made a start on the turbo flange. Forgot to take a pic of that though. :roll:

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Headers done!

 

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Looks like there's plenty of clearance all round the turbo which is a result.


Originally I was going to mount it the other way round to get the exhaust exiting on the right side like it is now. I'm glad I put it this way though, the headers were simpler to make and they should flow better.


Things still to do:

- Finesse the inside of the headers... with a grinder. :-)

- Sort out oil lines.

- Make up plenum.

- Make post turbo exhaust.

- Acquire intercooler and figure out piping.


So yeah, nearly done. :lol:

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