GUIDE : Steps for modifying


SM Official Expert: Guide Author
SM Expert
May 26, 2009
Derbyshire, UK
A long time ago HKS released a series of stages for tuning. This is a bit of an update based on what we’ve learned and what has changed.

Power is estimates only and at the crank and there will always be someone out there claiming crazy figures, in reality you’ll often be disappointed if you expect the claimed power hikes from manufacturers.

Stage 1: 230bhp

Step 1 has to be getting the Supra back to the kind of shape it was in when it left the factory so make sure everything is in spec. Things to do include:

1. £60 New plugs (NGK coppers are fine) and leads
2. £0 Check/adjust your TPS
3. £0 Check/adjust your timing
4. £varies (depends what shims you need) Check all valve clearances
5. £0 Compression check (tells you about the condition of the engine)
6. £0 (unless you need a new one!) Inspect the turbo for play
7. £40 Coolant + stat change (always look after your coolant system)
8. £20 New air filter (unless you are going to do an induction kit straight away)
9. £30 Oil + filter change
10. £40 Fuel filter (yes there is one!)
11. £40 New water pump (the blades deteriorate)
12. £50 Diff oil and transmission fluid change
13. £0 Lose the EGR and air con (personal preference of course)
14. £50 New brake pads/discs as required

Basically an extensive service is needed and you should check everything for wear. Don’t expect a 100k smoker to make you good power, ground work is important if you want any kind of longevity to your fun and games.

Price: You’re looking at around £350 - £400 to get the car fully sorted with a good foundation for modifying. People will cut corners here inevitably but I’d recommend you get the fundamentals right before doing anything to increase power

Stage 2: 240bhp

Next on the list is the inlet and exhaust. The inlet is easy, grab an induction kit and throw it on instead of your standard restrictive (and quieter) airbox. The K&N 57i is popular and the Apexi unit is very good too. People have had good experiences with the cheap ebay style induction kits too and various universal items.

I’ve combined inlet with exhaust although the exhaust will give you bigger gains. Ideally replace the turbo elbow with a free flowing unit (suprasport do these) and then a full cat back exhaust. You can lose the cats and still get through an MOT and it will knock your boost up a small amount (1-2psi typically) too. Mongoose/blue flame exhausts can be had for about £200-£300 and have proven solid bits of kit although you can get a full stainless system made for about £500 if you prefer.

I’d recommend blow off valve / dump valve now, the old one is probably overdue for a change and you can go atmospheric if that’s your preference

Price: Varies considerably but approximately:
£30-150 for the induction kit
£150-600 for the exhaust
£100 dump valve

Stage 3: 250-280bhp

With your exhaust restriction reduced you can now enjoy the gains of a bit more boost by shimming the wastegate. Search for details but basically you can knock up to about 10-12 psi without any fuel cut issues. Note that a boost gauge is recommended here so that you can see what boost you actually hit. If you’re going for long term big power then now is the time to invest in an electronic boost controller. You can then have complete control over your boost settings and hi/low values etc. I’d recommend the Greddy Profec B Spec II for a nice simple controller

Increased boost = increased likelihood of a blown head gasket so start thinking about stage 4

Price: About £1!

Stage 4:

At this stage you need to decide your power goals. For a reliable 300bhp car I’d just do a straight metal head gasket and ARP studs then leave it at that. For 500+ bhp pull the engine and get some solid internals put in.

Make your decision now and save spending money twice.

Metal head gasket (HKS, Titan, Greddy, Cometic etc) in whatever size you need based on previous skims to the head etc. It’s possible the block will need to be machined as well as the head so be prepared to pull the whole engine.

ARP bolts or studs, I’d always go for studs myself.

As well as the metal head gasket, updating the cooling system is a good idea with something like a big Fluidyne/PWR radiator and some Flex a lite fans (if you don’t like electric fans then skip them but I recommend them). It’s worth bypassing the heater matrix valve to reduce heat build up at the back of the head too. Check and replace all coolant hoses as required

£150 for the head gasket and studs plus
£200 for the rad
(£150 Flex a Lites)

Stage 5: 300-400bhp

For those staying <= the 400bhp mark, Lexus/550s. Time to raise fuel cut an increase boost somewhat, you will need 550cc injectors a Lexus LS400 air flow meter, Walbro (or similar) fuel pump and preferably an adjustable fuel pressure regulator (AFPR). An SAFC fuel controller will be needed to set this up and some time on a dyno or with a wideband O2 sensor.

Note if you are going for an aftermarket ECU then try and avoid getting piggy backs like the SAFC, fuel cut defenders etc because they will become redundant for you (although you’ll probably have no trouble selling them off if you do change your mind).

I’d be looking for a hybrid at this stage but nothing too crazy, just a modified CT26 will have you knocking out these sort of figures all day long.

You really need to be thinking about brakes and suspension mods from here on in so check out the nightpager kit using 300ZX bits or maybe hi spec for their big calipers. As for suspension, anything from KYB/Koni/Fensport etc shocks + springs to Tein/HKS etc coilovers

The stock clutch is going to be struggling here so invest in something like a Spec clutch. Pick one to suit your power goals now and in the future but keep in mind that it will wear out so don’t get a clutch capable of 800bhp if you aren’t going to do anything for two years!

While going the clutch it might be worth considering a lightened flywheel. You can modify the stock unit but with aftermarket units from the likes of RPS and Fidanza readily available I’d recommend just grabbing one of them.

I’d be thinking about a bigger oil cooler (Mocal are worth looking at) now and if you’re getting a massive one then it would be worth thermostatically controlling it.

£100–250 SAFC (depending on where you get it and whether it’s new)
£150 for the aeromotive AFPR from the states which is very good
£100-250 Injectors - depending on condition and source
£80 AFM (second hand)
£60 Walbro fuel pump
£200 (roughly) for a second hand hybrid turbo (depends on specs) or about £300 to have one modified
£200-£400 Clutch
£150 Flywheel
£100-£150 Oil cooler
£400 - £2000 Brakes
£600-£1000 Coilovers

Stage 6: 500bhp

For 500bhp you should really be looking at something like an SP61 or similar bolt on turbo. You can probably squeeze it out of the Lexus and 550s but you’re pretty soon going to approach 680 territory and start thinking about aftermarket ECUs such as MAFT pro, AEM, Link etc.

To go with your bolt-on turbo a bigger intercooler is going to be beneficial and preferably some nice large hard pipes to go with it. You can use standard routing in which case you need an in/out on the same side of the intercooler or you can upgrade to the more standard style with the inlet/outlet on opposite sides of the IC but you’ll need to come up with some custom pipework.

You’re really going to need forged pistons (Ross, JE, Wiseco etc) now and preferably thinking about rods (Eagle are nice and cheap but Crower are nice) too. Oil pump might as well be changed with the engine out.

£500-750 Turbo
£250 Intercooler + pipework (~£100)
£350 Pistons
£110 Oil pump
£250 Rods

Stage 7: 600+bhp

At this stage you’ve got a lot of money to invest to have a vaguely reliable system. You need to be thinking about mods form previous stages as well as:

- A further Walbro fuel pump
- Maybe worth thinking about cryo treating the thrust washer in the R154 for a manual. If you’re still on an A340 then think about a manual conversion or invest a lot of cash
- T4 turbo, you’ve got such a wide selection here with variables including lag, boost, max power, boost characteristics etc so you need to size this for your own application. You should think about a tubular manifold and external wastegate to go with this
- Engine rebuild, as well as pistons you really need rods at this stage. ARP crank studs & rod bolts, Clevite bearings
- Standalone, it’s time to ditch the piggy backs now and pick a full aftermarket ECU. It will probably cost about £800-£1000 in tuning to have it set up. Wideband O2 sensor and maybe EGT would be beneficial here too.
- Injectors are going to need to go to at least 680/720 and possibly up to 1000cc+ depending on your goals
- Oversize valves, ideally valves, locators, seals, springs, locks, retainers and guides might be worth considering at this stage and possibly cam changes to move the power band around
- Look into head port matching maybe polishing too, baffled sumps, knife-edged cranks etc

£400-£1000 T4 + manifold + wastegate
£120 ARP rod bolts and crank studs
£50 Clevite bearings
£1000 Tuning
£300 Injectors
£250 Oversize valves (£750 for all the kit)
£200 Head work
£150 Wideband
£100 EGT


Nov 14, 2008
Great guide. Make that 2 fans. I think I have everything for 6 or 700 but I will detune it to 500whp for longevity. Again thanks for the guide. And where are you leaving to? I might have missed that in your post since I skiped straight to the higher numbers.


SM Official Expert: Guide Author
SM Expert
May 26, 2009
Derbyshire, UK
Thanks for the feedback Bomberillo, glad you like it - there were supposed to be a load of pictures in this guide but my new baby came along. I'm leaving because there's another baby so I've left the Supra fold! I drop in when I can though

Anyway, best of luck with your 500rwhp