Turbo upgrade (project!)

so at what turbo psi would you need a different fuel regulator, bearing in mind, stage 2 turbo for more boost and chip.

incidently, what is the max boost the chip will allow and also what is the max boost the PRV will allow with what i want to do??

16psi is the safe limit before the boost temps get too high, and the injectors start to run out of juice.

Squeezing lots of fuel pressure reaps less rewards the higher pressure you go, and for instance at 17psi, you may want an extra 10psi of fuel pressure for safety, on top of the current factory ratio, which would involve a new regulator.

Doing it properly requires fuel pressure, bigger injectors and management.

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am i wise??

or should i just leave it alone??[/quote]

If you were wise you wouldn't have bought a GTA!

David G keeps reminding me that £ per bhp, the chip is the first priority, every time!
£105 for at least 30 bhp, maybe upto 35-40ish. This is £3 per bhp, fantastic value.
If only it were possibele to get 300BHP out of a turbo GTA for £300 ???

Er add a nought for that extra power!

The power youre looking for is about the same as my car had before the 3 litre lump went in. I've always roliing roaded my cars whenever mods were made to find out what works so listed below is what my car made with what mods on a low mileage car.

Chip and 3 psi boost increase over standard 225 bhp
+ Devil Group N Exhaust 228 bhp
+ K+N Replacement filter 230 bhp
+ Chargecooler & Hybrid turbo (similar spec to ART stage 2) 258bhp at 1.1 bar and now running lean.
+ Adjustable Fuel pressure regulator and HKS EVC4 boost controller - never tested but it felt substantially quicker with the mapped boost and extra fuel - at least 15-20bhp extra I would estimate.

Add a bit of advise - buy a high quality FPR - the diaphram split in the one I had and sprayed petrol all over a hot engine - very lucky not to have a major fire. Not long after that the 3 litre lump was purchased and I never got around to putting a new FPR on.

If I was doing this with the benefit of hindsight this is how I would do things

1. ECU Mod and run 15 PSI
2. Straight exit exhaust and one of those carbon fibre air-boxes David sells - fitted in a treat.
3. Uprated intercooler or chargecooler and another pound of boost.
4. Hybrid turbo set at whatever boost the car will fuel for when checked on a rolling road. Probably around 15 psi.
5. Extra mapped injector kit (these are around £275) which just adds extra fuel as you require straight into the plenum and is fully mappable. This should fuel enough to make 280-290bhp with the right boost.

I reckon any head work on a turbo car is expensive for the gains you get in comparison to running a bit more boost or cooler inlet charge. Any cam changes should really have a remapped ignition and fuel map which isn't possible on non-cat cars so you won't get the full benefit anyway.

280-290bhp without cams??? That seems optimistic given how lame the standard cams are and how important the cams are in gaining power.

I said it would have enough fuel to make 280-290 bhp not that it would produce that much power. The kits typically come with an injector capaple of fueling another 50 BHP or so which on top of the GTAs 230-240 makes the figures I suggested.

Its an interesting idea.....is it worth it on the GTA once the programmable ECU is up and running (assuming bigger injectors too)? Ive come across the idea with water or methanol, just not petrol.....could be a cheap way to extra horses. Speaking of which...hows the wiring going?

On the RR, you can see the chargecooler made the biggest gain, though it will help with the car being stationary on the rollers.

Its a pointless exercise if you have a programmable ecu and big injectors as this is the optimum arrangement, but for a budget mod (probably £1000 cheaper once fitted and mapped) it has the fueling aspect on a medium spec engine well and truly sorted.

If you work it out, the standard injectors are maxed at 260bhp.

The standard ones are 185cc/min at 3 bar fuel pressure. If you run a bar of turbo boost, the flow rate goes up to 218cc/min.

The rule of thumb of injector sizing is take the flow rate, divide it by 5 and multiply it by the number of cylinders, and you have your max bhp.

..so 218/5 x 6 = 261bhp...pretty close to what Tony had.

A way round it is to use an adjustable regulator and run a bit more fuel pressure (say 10psi extra on boost) which equates to 236cc/min and thus 283bhp.

Or switch to slightly larger R25 V6 2.9 injectors (198cc/min @ 3 bar, or 231 at 1 bar of turbo boost and a standard regulator so 277bhp

..or with an extra 10psi fuel pressure, 249cc/min and 298bhp.

The Lemans model ran the later R25 2.9 198cc injectors, and thus why 284bhp was available on cams and remapped management and just over a bar of boost.

Obviously, more power is available with the same amount of air and fuel, if you get the timing spot on, or efficiency up, so for instance on Tony's engine, 258bhp may have been acheivable with slightly less boost (so not running in a lean state) but advancing the ignition timing, or having the larger turbine housing as on my Stage 2 turbo.

As I'm sure David will confirm injectors shouldn't be run close to there maximum duty cycle as injector failure becomes far more likely - I think they say 80% is about the safe limit

after putting a hole in the black gta turbo's gearbox i have decided to have another winter rebuild project!!


brakes will be the next thing and ART adjustable suspension is currently fitted.

or should i just leave it alone??

Better start with the brakes - or you are in for a nasty surprise. If you have ever tried the car at a track, you will know. Standard brakes fade the second time you use them hard.

Regards from Denmark
Alpine V6 Turbo Le Mans (1990) - with big brakes Not even Nürburg Ring can make them fade.

Sorry to hijack the thread for a moment!

Can we see pictures of your Le Mans (with big brakes!) anywhere?

lol, they can't be that big, the Lemans have 16" front wheels