20VT Tuning Workshop - The Knowledge

Today I decided to write a 20VT tuning workshop guide aka ‘The Knowledge’. I hope this helps people out with any questions about tuning this baby. This is knowledge I have gathered over the years from building my 20VT engine myself and what has been posted by members on this very forum by searching. I am not going to go into great technical depth as I would like to keep it simple for all to benefit if you want technical details then put up a post that’s what the forums for. If I have misinformed or missed anything anywhere please let me know. Flywheel BHP & FT/LB figures is my conservative view and not to be taken 100% accurately. This is my view on tuning the 20VT so if you disagree then too bad write you own ‘knowledge’. laugh

Before you even think to tune your engine a health check and service is a must have. You should never tune an unhealthy engine as that can result in disaster.

Stage 0 – Health Check (220BHP)

Compression Check, Oil & Filter, Air Filter, Spark Plugs & Coolant

Stage 1 – (240-255BHP) – Bolt on Parts
GTEC1 Chip
Air Filter
Boost Gauge
NGK Spark Plugs
Exhaust (Don’t Decat)

Stage 2 – (250-360BHP) – Bolt on Parts
Stage 1 Plus
Turbo Upgrade
Walbro Fuel Pump
Boost Controller
Uprated Engine Mounts (Optional)
3.8 FPR (Optional)
Downpipe (Optional)
Decat (Optional)
Aquamist (Optional)
GTEC 2 with fuelling check or Unichip or Live Map

Stage 3 – (320-450BHP) – Engine out Job
Stage 2 Plus
Fully Balanced Bottom End
Forged Pistons
Forged Rods
Bigger Turbo
Uprated Water Pump
Uprated Engine Mounts
AUX guard
Tubular Exhaust Manifold (Optional)
Camshafts (Optional)
Uprated Cooling Fan (Optional)
3” Downpipe
3” Exhaust System (Optional)
Aquamist (Optional)
NOS (Optional)
Unichip or Live Map
Standalone ECU (Optional)

Stage 4 – (430BHP+) – Engine Out Job 2.4/2.5 Conversion
Stage 3 Plus
2.4 Stilo Crankshaft
Custom Forged Pistons/Rods
Huge Turbo
Tubular Manifold
External Wastegate
Full Headwork
Big Brake Kit
Standalone ECU
Uprated Gearbox
Paddle Clutch or Twin Plate Clutch (Optional)
Aquamist (Optional)
NOS (Optional)

Stage 5 – 4WD/RWD with 650BHP+
Somebody build one please. laugh

Now that you have read all of the recommended stage work I will try and explain as best as I can as to what all this stuff means.


Air Filters:
This allows the engine to breathe more easily and adds a bit of grunt to the induction noise. Apexi, Green Cotton, K&N & RAM AIR are proven brands. Some air filter can be restrictive and are rated to a MAX HP so bear this in mind when choosing your filter.

This means Straight Induction Pipe and it replaces the standard turbo intake pipe with a metal upgrade. It improves turbo spool up and cool air feed, it can only be fitted in conjunction with an FMIC.

This means Front Mounted Intercooler and it replaces the standard intercooler and sits in front of the water radiator, it further reduces intake temperatures thus increasing power. There are Side Mounted Intercoolers and Charge Cooler but these are inefficient and restrictive the FMIC is the only way to go. Pro alloy is the one that is highly recommended, Pace are rubbish and there are a lot of ‘e-bay’ ones too so be careful.

Water Injection:
This brings down the intake charge and increases engine safety by spraying water/methanol into the induction system. As a result of this more power can be made however it needs constant attention and not everyone would be happy running it. A popular brand used is Aquamist.

Dump Valves:
There are two types of dump valves, one is BOV the other is a recirc. BOV or blow off valve releases the pressure to atmosphere and makes a “phsst” sound. The recirc dumps the air back into the airflow and is pretty much discreet depending on your induction system pipe work. Popular brands use are Forge, Blitz & HKS. Cheap dump valves often leak and can cause problems.


Fuel Pump:
More power needs more fuel thus a fuel pump upgrade is needed. The Walbro 255 pump is what is used with and additional wiring mod to be performed whilst fitting. This pump should see you to 500BHP. For those seeking more power you need to add more pumps.

Also know as a fuel pressure regulator, this determines how much fuel pressure is in the fuel rail. The standard FPR is 3Bar the upgrade pushes it upto 3.8Bar. This upgrade is only recommended if your engine is going to be mapped and is running power levels of 300BHP+ and with a Walbro pump.

Any change of the fuel injectors would really require mapping so it is only recommended for high powered Stage 2 & Stage 3+. If you need more fuel also consider a 3.8Bar FPR. Make sure you get your fuelling checked when messing around with this system.

The standard 330cc 20VT injectors @ 3Bar/3.8Bar can fuel upto 330BHP.
The standard 384cc 16VT injectors @ 3.8Bar can fuel upto 360BHP
The Bosch 440 injectors @ 3.8Bar can fuel upto 410BHP
The Siemens 630cc @ 3.8Bar can fuel upto 580BHP


Spark Plugs:
The only plugs to use are NGK iridium IX. They are 7’s for stage 1 and low power Stage 2 and 8’s for high power Stage 2+. NGK non-resistor v-power racing can also be used for high boost applications.

Fully Balanced Bottom End:
Whilst the engine is out get it balanced that removes most unbalanced forces taking strain off vital components and means smoother running.

Forged Pistons:
Looking for some real power? There is much debate about this but I’m not going there my opinion is that if your aiming for more that 320BHP+ and your taking your engine apart then these are a must have. Basically the standard pistons crack at the ringlands over time so if you take the engine out you must go forged. Forged pistons allow you to run proper power when getting the engine mapped. Piston brands used are Accralite, CP, JE & Wossner. They come in 82mm, 82.5mm & 83mm. The CR varies from 8.0-9.0:1, the choice is yours. Please note that for the 2.4/2.5 conversion a different piston design is needed.

Forged Rods:
Looking for some real power? There is much debate about this but I’m not going there my opinion is that if your aiming for more that 320ft/lb+ and your taking your engine apart these are a must have. Basically the standard rod bolts can break or the rods bend at this torque level so if you take the engine out you must go forged. Forged rods allow you to run proper power when getting the engine mapped. Rod brands used are Arrow, Cunningham, Farndon & Pauter. These all come with ARP rod bolts so the choice is yours. Please note that for the 2.4/2.5 conversion a different rod design is needed.

“All the power is in the cylinder head” – Guy Croft. How much headwork you do is completely dependent on your spec and the power level you’re aiming for. There is so much detail here I am just going to list the basics.

Stage 1 – Port & Polish
Stage 2 – Port & Polish, 3 Angle valve seats
Stage 3 – Port & Polish, 3 Angle valve seats, Bigger Intake valves
Stage 4 - Port & Polish, 3 Angle valve seats, Bigger Intake valves, Bronze valve guides + more

2.4 Stilo Crankshaft:
This is needed for Stage 4 as it provides the stroke for the 2.4/2.5 conversion. You need customs pistons & rods to work with this crank.

Very few camshafts are available for the 20VT and not everybody is a fan of them including myself. To take full benefit of cams you need to have some decent headwork. A popular brand is C&B.

Uprated Water Pump:
The standard plastic impeller can break so a brass upgrade is available. For Stage 3+ as the engine is already out.


The standard turbo is a Garrett TB28 and in terms of tuning it’s useless. There are many other cheap and cheerful turbo upgrades to choose from Ultraspool, Superspool, GTiR & TD04. I’m not going to discuss these because firstly I personally don’t know much about their behaviour and secondly they are journal bearing which is outdated now. I’m not saying there crap as they have been proven and each good in their own way but with today’s technology it’s not the route I would go recommending to go down if you’re going change the turbo. Now here is a short review for the Garrett GT series. I’m not going to go into detail here about A/R, Trim, Lag, Boost etc as it’s your job to research which turbo will suit your setup best.

GT28R – Quick Spool up and can deliver upto about 310BHP
GT28RS – Good Spool up and can deliver upto about 360BHP
GT28RSR – Mixture of the two above and can deliver about 340BHP
GT2871R – Average spool up and can deliver about 350BHP-460BHP (Recommended for stage 3)
GT2876R – Not recommended but would be interesting if somebody tried it
GT3071R – Average spool up and can deliver about 350BHP-460BHP (Recommended for stage 3)
GT3076R - Average spool up and for the 2.4/2.5 Stage 4 conversions upto about 525BHP
GT3271 – Not recommended twin entry journal bearing, avoid this turbo.
GT3582R - Late spool up and for the 2.4/2.5 Stage 4 conversions upto about 600BHP
GT3788R - Late spool up twin entry for the 2.4/2.5 Stage 4 conversions upto about 675BHP

For Information on Hybrid Turbos and their Stages please follow this link:
Hybrid Turbos & Stages

External Wastegate:
This provides better boost control and eliminates boost creep. This will always be the way forward and if you are looking at a GT3XXXR+ you should really consider this option. A screamer pipe can also be plumbed in if you like some real noise.

Boost Control:
The standard boost controller is only really for the standard turbo. A decent electronic boost controller will allow you to change the boost as you drive and display many other settings etc. This device is highly for recommended for all levels of tuning. There are many brands of EBC so look around for one that suits you.


This joins the turbo to the exhaust system. The standard one is OKish but it’s a good idea to change it if upgrading to a GT series turbo. If you’re on a budget with a GT series turbo you can buy a 5stud to v-band adaptor they work but are a tad restrictive. Blueflame do a decent downpipe v-band or 5stud but for ultimate performance (Stage 3+) the H&S 3” downpipe is the dogs.

There are many exhaust companies out there but the most basic bolt on one that seems to be popular is Blue Flame. If your car is running the standard turbo do not remove the cat as this can damage the turbo seals. For higher power levels it is recommended that the bore size gets bigger however not everybody is happy with the drone it makes. A 2.75” should be fine for up to 350BHP but I recommend a full custom 3” system with mandrel bends which keeps back pressure down if you’re planning to run more than 360BHP.

This removes the catalytic convertor from the car thus increasing power. Do not do this if you have the standard turbo as it WILL blow the seals. Removing the cat will make sure your car will fail an MOT however if you’re not happy to do that then a decent high flowing sports cat be brought instead.

Tubular Exhaust Manifold:
The standard manifold is still dyno proven for upto 400BHP when ported. Tubular ones at 38mm are really for external wastegates and bigger turbo options however these are still being developed so there maybe ones to benefit the Stage 3 owners soon.... Getting the manifold right is key to unlocking the big BHP figures that can be achieved from this engine.


More power means more chance of the clutch slipping so below are the upgrade options.

Standard Clutch upto 260ft/lb
GTA Upgrade upto 280ft/lb
Walkers GTA Combo upto 300ft/lb
Helix Organic rated to 320ft/lb but will take more like 380ft/lb+
Helix 4 Point Paddle rated to 350ft/lb but will take more like 440ft/lb+
Helix 6 Point Paddle rated to 350ft/lb but will take more like 440ft/lb+
Helix Twin Clutch 500ft/lb+

Uprated Gearbox:
This can only be performed on the 5 speed early box as an extra strengthening plated is added to stop the gearbox from flexing. With the gearbox off and apart the gear oil can be tapped through a cooling system with a standalone pump to help stop the oil from overheating.

Most people seem to forget that the more power you add the more stopping power you need. The standard coupe brakes have 4 pot Brembos and with only a change for decent discs and pads should see you through to 450BHP. A Big brake upgrade is highly recommended for those considering 450BHP+ with conversions from Ferrari, Porsche & TAROX available.


ECU Chips:
There are various 20VT plugin chips out there but the one that everybody uses are the GTECs. These chips change the engine map to achieve more power.

GTEC 1 – Increases boost to 1.2 & advances timing slightly
GTEC 1 HF – Same as above but with a higher fuelling
GTEC 2 – Boost at 1.2 with more timing advance for FMIC & 98IRON+ fuel
GTEC 2 HF – Same as above but with a higher fuelling

Because the GTEC chip is generic it is very important that once it is fitted you get a fuelling check to make sure things are operating properly before blasting it, if you don’t do this you could damage your engine. This is a cheap and easy way to achieve good results and works well on engines upto 310BHP.

Unichip is a universal piggyback chip that allows the operator to map your engine more specific. The base chip would still be a GTEC chip however unichip allows control of injectors, timing, boost etc so that it can be tailored to your needs. This method is good and works well as there are many people out their able to map this system. It is recommended for high powered Stage 2 & 3 engines. The limit lies within the standard ECU which is about 380BHP, any more than this and mapping unichip becomes a real problem.

Live Mapping:
Very similar to unchip however there is no piggyback ECU the standard ECU is completely tailored to your car. No GTEC chip is required as the mapped chip becomes your own “personal GTEC”. This method is probably the best your going get out of the standard ECU, the only down point is that only one place in the country does it properly and for those not willing to travel then unichip is the very close equivalent. It is recommended for high powered Stage 2 & 3 engines. The limit on the standard ECU is very debateable but I think for those aiming for more than 450BHP should begin to consider standalone.

Standalone ECU:
Why what is wrong with Unichip/Live mapping? Two main reasons Injectors & AFM. For people aiming for 380BHP+ the standard ECU cannot cope with injectors bigger than 440cc so the unichip cannot fool this so it will run rich lower down the rev range also the AFM will run out of scope.

Live mapping is not the same for the injectors but the AFM is rescaled to give a wider range however there is still a limit to certain things you can do but thankfully the live mapping is able to raise this limit further to about the 450BHP mark.

Standalone doesn’t have these issues and do have many extra features such as launch control, traction control, map sensing, WI/NOS maps etc... Most places are able to map these systems. There are many brands with lots of different features out there but there are only two that I know are 100% tested coupe friendly which are Motec & Omex.


Boost Gauge:
Adds no power to the engine but allows you to see how much boost you turbo is running, it is a very important gauge and a must have. Most boost controllers have this gauge built so bear this in mind.

Uprated Engine Mounts:
The top and lower mounts suffer from wear but not only that the increased torque a tuned engine produces wants to rip the engine out of the bay causing the driveshafts to knock and in some cases it is known to crack the sump. These polyurethane and aluminium mounts stop this from happening.

Nitrous oxide, not my thing but completely up to you. I wouldn’t even consider this unless forged internals have been fitted.

AUX guard:
The AUX belt can slip off into the cambelt trashing the engine. This is a must have if rebuilding the engine.

Uprated Cooling Fan:
Not really needed however space can be an issue and because there is no decent upgrade radiator available a decent cooling fan will ensure you keep them temps down especially on a hot summers day.

What about?
ARP head bolts, ARP main bolts, Uprated Headgasket, Bigger Radiator, Bigger Oil cooler, LSD. Simple answer is they are not needed as the standard parts are fine.

For more details on part brands and pricing check here: http://www.fiatcoupeclub.org/forum/ubbthreads.php?ubb=showflat&Number=345016#Post345016

This was written by me but it only exists because of the forum being such a helpful place so really it belongs to everybody on here. TurboJ

This Knowledge was revised on the 20/6/2009
- Revised BHP figures & Stage work
- Added Dump Valves
- Revised Engine Management & Turbochargers
- Few Grammar/Spelling issues & other minor adjustments