Turbo sizing for Engine Displacement

Just watched the Webinar on Turbo Performance and it was great. One point I didn't pick up on was what is the best way to match a compressor map to a particular engine displacement.

For example trying to select a turbo capable of 400 Hp for a 4.8 DOHC Nissan TB48 running around 8 PSI of boost.

Is there an equation I missed?

I'm pretty sure that the "Introduction to engine tuning" course explains how to calculate an engine's mass air flow. It may even have the information here on this forum.

Hey mack85n, apologies for the delay in replying - I actually wrote a reply to this but I think it timed out and I didn't notice when I went to post.

The webinar wasn't strictly 'how to choose the correct sized turbo', but rather I was focussing on how to analyse your turbo selection. That being said there was still a lot of relevant information in the webinar that applies when choosing a turbo. The key is to choose a compressor that will support the airflow you need while ensuring that you're operating within the compressor map (ie not beyond the choke line or surge lines). Remember that you're going to need around 9.5-10.5 lb/min airflow to make 100 hp (give or take), so in your application you'll need around 38-42 lb/min airflow. Typically I like to have a little headroom in there so you're not at the limit of the turbo from the get go.

What I'd suggest you do is spend some time playing around with Borg Warner's 'MatchBot' program which will let you enter all the relevant parameters for your engine and then see what compressor maps are the best fit for your aims. This application is obviously only suited to BW turbos, but it gives you a good idea of how the sizing will work. http://www.turbos.bwauto.com/aftermarket/matchbot.aspx

Thanks Andre,

I appreciate the reply. I've been reading up further on Garrett's website and I'll have a look at the BW site aswell. Garrett had some great calc's and info which, together with the webinar has helped a great deal.

As always the level of support that you guys give is fantastic. Bar far the best investment in my learning in a long time has been joining up with HP Academy.

Cheers