Omi Posted January 31, 2006 Report Share Posted January 31, 2006 Posting from the PDA so I'll be brief... I need to work out the best turbo for a specific application - I've already checked the Ray Hall calculator, but that only shows turbos he sells and I'm hoping to avoid £400+ for a ball-bearing custom GT if there's a £150 solution in the local scrapyard. I'm converting my NA BMW to FI, with the cunning use of mirrors and magic... Before you call me nuts, it's perfectly reasonable and a good way to essentially double power while keeping the same great car and handling and without dropping another unsuited engine in there. Engine is a BMW M42. 1796cc originally, slight overbore for pistons. Going 8:1 compression with custom JE forged pistons. Forged crank as standard. Forged rods as standard. Solid lifters off M3 S52 engine. Cosworth/Mercedes intercooler. Custom tubular manifold. Megasquirt n Spark Extra ECU, with MAP, TPS, Knock and Wideband O2 sensors. Custom Blue Flame exhaust. Uprated fuel pump and 50lb injectors. According to my calculations I'm looking at reliable boost of 14-17psi, which translates to 260+bhp. Looking for the best turbo to handle that boost all the way to the ~7000rpm limit, with lowest boost threshold possible. Might need my head examined too. Thoughts please gentlefolks? Omi Link to comment Share on other sites More sharing options...
Insurance Jon Posted January 31, 2006 Report Share Posted January 31, 2006 [ QUOTE ] Posting from the PDA so I'll be brief... [/ QUOTE ] PMSL Link to comment Share on other sites More sharing options...
Soapsuds Posted January 31, 2006 Report Share Posted January 31, 2006 not well-up on custom fit turbos, but whem people pop different units on Starions, they go for anything Garret! The smaller T3 and T4's are fairly cheap and good performance, but T28's are the dogs danglies. My standard starion one is now running 14psi (originally 10), but is known to be good for 18 before it pops seals!!! Apparently, some of the rally / amateur racing mags are the best places to find them, in the classifieds.... not much help really was it!!! Link to comment Share on other sites More sharing options...
Tobes49 Posted February 1, 2006 Report Share Posted February 1, 2006 The main thing is to get the compressor map for the turbo and make sure you dont cross the surge line, For this you will need to work out the Pressure ratio of the compressor housing, PR=(Boost pressure+Air pressure)/Air pressure, Example you want to run 14.7PSI of boost, PR=(14.7+14.7(saying the air pressure is about 1000MB))/14.7 PR=29.4/14.7 PR=2 This is the pressure ratio for the compressor map, But in looking for a compressor map found this site with it all on! Have a read here! I think for the boost your looking to run, your going to need a T3 or T4 turbo, But these will be a bit laggy cause of the really low C/R. Link to comment Share on other sites More sharing options...
Tobes49 Posted February 2, 2006 Report Share Posted February 2, 2006 Just wondering, have you built the megasquirt yourself, I'm looking to run one of them on a supercharged rover V8 engine i'm building. Would be intrested in any feedback. Link to comment Share on other sites More sharing options...
BenjaminTDI Posted February 7, 2006 Report Share Posted February 7, 2006 Just seen this thread. Friend of mine uses a garrett VNT20 hybrid @ 2BAR boost. Might be worth looking at a VNT20. I doubt you'll get a turbo to give you full boost all the way to the 7000rpm redline, they usually back off the boost after 4k or so in a petrol. Link to comment Share on other sites More sharing options...
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