My MG ZS Turbo....

[Dan1971]

Originally Posted by Quadcam24

update as promised.
my car made well under the expected power at just 246 bhp and similar torque, but the boost gauge showed boost was very low, nowhere near what it should have been.
Today i took it have it checked out, then have it custom remapped and re rollered.
It made 306 bhp and 330ftlb.
285-290 is the expected number with a 2.5 inch turbo back exhaust, the tech guy said it wouldnt have made the power without the 3 inch downpipe.

Blimey - that's a hellofalot of power -

[Quadcam24]

cheers

[carmadbaker]

Impressive results bet your well chuffed

Im still reserved about the limits of a 2.5" zorst, your limited by the oulet of the turbine housing anyway which isnt oversized to the exhaust.
Supporting mods and engine characteristics play the main role in which exhaust is better suited, not to mention what turbo is being used.
I will just have to wait and see, im not going number hunting im heading for driveability,
but i have no doubt a 2.5" system is more than adequate.

[fastmike]

We found going from 275 to 300 BHP on Saabs required a 3in downpipe to keep exhaust gas temps at sensable levels....

[Eddie]

With the Honda’s anything approaching 300hp needs 3” down pipe and system, and 600hp + requires 4” down pipe running into no less than 3 ½” system. We done some back to back testing, exactly the same set-up other than 3” down pipe into 2 ½” system then a 3” system, it gained 30hp at the same boost, that said, it was an ITR head and the volumetric efficiency (flow) is very good so you need a free flowing exhaust.

That’s incredible power from the Vauxhall lump what boost was it running and what turbo? good usable torque curve.

[Quadcam24]

Hi Ed and thanks, its only running 17 psi peak boost, holding 14-15 at the top end. Ive learnt recently theres a lot more to making power than just boost pressures.
Its just running an astra vxr turbo, so its at its comfortable limits as far as im concerned, some run them at 20 or even 21 psi but im happy with how it drives, i didnt want an agressive map with loads of boost and a huge torque spike and massive power tail off higher up like a diesel, and its worked, on a dry warm road it can still just about lay 2nd gear.
The vaux lumps are quite good for tuning, infact the guy who helped me fit my injectors has a zlet in his tigra running 700 bhp, i believe hes one of the very few to crack a 9 second run in a front drive car.
I cant see me going for a lot more power as it means doing rods and pistons, then it gets costly. I might fit a high flow inlet manifold at some point, that only adds about 10-15 bhp to the peak power but it will hold that power then to the redline instead of it tailing off.
Im enjoying it now its mapped properly( therein lies another long tale that ill tell you sometime), its fun driving a bus that can give e46 m3 drivers red cheeks,lol

[Eddie]

Dave

I know the guy that help you, Specky, he runs in the same drag series as Any N (ESC) I was supporting Andy last year. That’s very good power for work done and for a FWD road car that’s enough in my opinion. And I agree there is more to tuning than throwing more boost at an engine, delivery and power under the curve is paramount. Maximising the mechanical tuning is far more beneficial make more power at less boost. Was involved in a tuning session back in March, 1800cc running a Precision S372 at 2.5 bar, first runs it made 494hp at 2.0 bar, dial in the cams and at same boost it made 70hp, went on to make 700hp and 500ft/lb at 2.5 bar. Dialled out the cam overlap, which is great for NASP but not so clever on a forced induction set-up. Always good to reduce boost to control heat management and lower peak cylinder pressure, makes for a happy engine.

[Quadcam24]

ha ha ha...specky thats him, right joker he is, dont think he spoke a serious word the whole time i was there, good mechanic though!

[andy-81]

wow just read the whole thread as i only looked at it today a lot of blood, sweat, tears and bad language i'll bet but it all looks worth it well done on building such a fantastic piece of machinery i am proper jealous mate

[carmadbaker]

Well.... After gettin well and truely fed up with chasing faults i've had enough.... Ive decided to fit my omex management, so the long slog begins... Wish me luck!!