Translate this graph

[gotmeaT-5]

Can someone translate/explain the graph please ? it shows Turbocharger pressure maps from 15 to 19T Turbos. The two I'm selecting are the 16T and 18T but cant really understand it enough to make a good choice on increasing the bhp on my T-5

[t5_monkey]

That graph basically tells you the performance 'envelope' of a turbo... i.e. can it shift loads of air at a lower pressure, or generate higher pressures, and what amount of air it can shift blowing at what pressure and RPM.

Since a turbo will typically blow at 1-2 bar under most applications, you'd be looking for peak flow in that area on the graph.

In essence... the bigger the envelope (especially to the right of the graph) the better - so you can see from that graph the 19T is a clear winner - can't see the pressure units on the left, but if it's atmospheres you'll see the 19T is way ahead at 1 to 1.5 which is what you'll be using in your car more than likely.

One point to bear in mind... that doesn't take account of lag - so if you're wanting torquey and responsive as oppose to a fire breathing monster over 3000 once your spooled up.... smaller may be the way to go.

If you're gonna go daft... get the 19T ... you know you want to :)

Just out of interesting... why are you considering the 18T instead?

Another point.... bigger turbos can sometimes blow at lower pressures (and lower RPM) which means a well configured system might have pretty decent lag and driveability characteristics compared to a smaller turbo performing at the 'edge' of its envelope, as they tend to make the air get hot and expand when doing this.

You'll see people running 10psi on a big turbo, getting the same results as 15psi on a smaller one due to the heating effect.

Just my opinion but if you're thinking about a turbo swap you may as well go as big as you can manage, given the costs involved - and you'll get used to the lag (it'll just enhance that punch in the spine feel when it kicks in.) and if its set up right, prob won't be much worse than a smaller turbo driveability wise anyway.

:jaw: It'll be even better than... VTEC :D

[gotmeaT-5]

I am considering the 18T following advice that the 19T may be too harsh for a modified 850 T-5 with an automatic transmission, although I'm only looking for 300-400 bhp so nothing dramatic the 15G is said not to be too good for going much above 270bhp. I have been suggested that a Garratt turbo may be better suited to my requirements, however, the numbers for the engine rebuild alone are fast becoming out of realistic approach so I'm bringing my plans down to 270-350 closer to 300 bhp seems to be far more attainable.

I've got hold of a set of White injectors believed to be 345-350cc @ 3 bar and along with a good ECU remap and K&N Filter 270-300bhp should be easily obtained and the 18T, I've been offered one for around £100 with 3 months warranty, seems to be the way for me to go until I've got a short/long block rebuilt for 400 bhp which will take the rest of this year.

[t5_monkey]

Cool... well a new turbo is going to be very pricey so if you can do it with 2nd hand parts you're sorted - much better bang for buck than forking out for a Garrett.

At the end of the day... how it drives isn't all about the power anyways so your best to get some proper work on the suspension too I reckon.

you could always get an MBC with the 19T and not run it too high (10psi or so)... so it can go straight into your rebuild when you get silly.

Is your short block going into the same car... or you got another project on the go?

[Rnash2002]

I would rip the chaps hand off for the 18T at £100 lol

[gotmeaT-5]

The rebuilt motor will be going straight in. 18T on its way couldnt find anything that good on Ebay for half the money with or without a warranty and if it doesnt do what I want then I will sell it on here and stick a Garrett on.

Got plenty of suspension work to do as I'm replacing all the bushes throughout done the shocks waiting for postie to drop off some Pi springs today so will be fitting those over the weekend should improve the ride or that's what I've been told.

[t5_monkey]

Cool sounds good - will look forward to seeing the build thread and associated epic dyno figures and 1/4 mile times :)

[Wobbly Dave]

you might also consider putting in a second in line cooler for your ATF. Volvo make OEM kits for towing and it is easy to fit.