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The route to power by Lorcan
Many 750 turbo owners, along with owners of pretty much any other bike, find themselves thinking "a bit more power would be nice". This guide is intended to give a snapshot view of the modifications necessary to increase your bike's power for street and race use. More details and advice are available in the forum. You can also search the forum for more help. The parts lists for each stage are in addition to the earlier stages. There are, of course, many ways to skin a cat and the lists shown are by no means the only way to achieve these power levels, but they are the most popular methods followed by forum members. All power figures quoted are at the rear wheel. See the New Parts section of the forum for ideas on where to buy parts.
But first, a health warning.
The following is ONLY A GUIDE. You, and only you, are responsible for the consequences of modifying your bike, some of which can be serious. If in doubt, consult a professional. All modifications should be notified to your insurance company.
Ok, let's get started. I think it almost goes without saying that you should start with a healthy engine. If it's blowing smoke, has low compression or rattles consult the forum for advice before going any further.
Stage 1 - Race mode, 100-115hp
The stock bike is restricted to around 95hp (at the wheel) by Kawasaki. We know this because there is a document from Kawasaki showing how to de-restrict it. Kawasaki call this de-restriction race mode. Click here for how to enable race mode.
Stage 1 parts list
K&N air filter #RU-1080, Silencer removal/replacement/modification for reduced back pressure.
Resistors as per the race mode document, boost gauge.
Stage 2 - Race mode with boost control, 100-135hp
The next step is to start turning the boost up. You need to be careful at this point as it is possible you will encounter detonation if you go too far. Detonation is an uncontrolled burn in the cylinders and MUST be avoided at all costs, or you will have a molten lump of scrap for an engine. You can hear detonation - roll the bike on in 2nd or 3rd gear, wide open throttle, it sounds like a rattle "the death rattle". Also check the plugs to see if they have come loose and for specks of metal on the electrodes - both are signs of detonation. If you suspect detonation is occurring, turn the boost down. Stock boost is 7-10psi, 12psi gives a noticeable increase in power with 15psi being the limit we would recommend on pump fuel. 15psi should get you to around 135hp, approx 40% more power than stock. This is the limit of the stock turbocharger. A dyno run is recommended to check the fuelling throughout the rpm range. Make adjustments to the TPS/resistors as per the race mode document.
Stage 2 parts list
Boost controller, boost gauge.
Dyno run to check fuelling. Dump valve. Oil pan mod.Stage 3 - Upgrade turbocharger, engine and fuel system, 150-200hp
This is where it gets serious! While not essential, forged pistons are highly desirable, the most popular and proven kit by a long way being the Wiseco 810cc. There are two schools of thought regarding fuel control. The Old School method favoured by HPU is to use an adjustable fuel pressure regulator combined with TPS (Throttle Position Sensor) adjustments to control fuelling throughout the boost range. The New School method pioneered by 750turbo.com is to use a Powercommander 3 to map the fuelling at stock fuel pressure like a modern bike. Both methods need setting up on a dyno for performance and reliability.
Stage 3 parts list
Upgrade turbocharger (Garrett GT20, T25, T28, HPU Stage2), Upgrade fuel injectors (RC310cc, HPU 880). Upgrade fuel pump (Walbro GSL393 or 392 for HPU method). Adjustable fuel pressure regulator (SARD) OR Dynojet Powercommander 3. Heavy duty clutch springs. Dyno runs for fuel setup. Race fuel for high boost operation.
Wiseco 810cc piston kit P809B, Copper head gasket (o-ringed), Wideband air/fuel sensor kit. Dyno runs to map fuelling. Intercooler. Lockup clutch. 530 chain conversion. GPz1100 throttle bodies. Dyna grey ignition coils. Ported spider pipe or race headers.
Stage 4 - Further upgrades to turbocharger, engine and fuel system, 200-250hp
A lockup clutch is essential at this point as the stock clutch will slip, even with heavy springs. This combination is capable of over 190mph and low 9 second quarter miles (8 seconds with suitable chassis mods).
Stage 4 parts list
Wiseco 810cc piston kit P809B or HPU 880cc kit, intercooler, Upgrade fuel injectors (RC370cc or 410cc). Lockup clutch. Upgrade turbo (GT22, GT25, GT28, HPU Stage 5). GPz1100 throttle bodies. Dyna coils. Ported spider pipe or race headers.
Upgrade wheels, forks, swingarm, brakes and tyres highly recommended! 1mm oversize exhaust valves, increased lift (but not duration) camshafts. External wastegate. Datalogger.