Quote:
Originally Posted by Mark S
The issue with a vnt big enough to provide good top end without crudely overspinning it (like one french manufacturer whose cars suffered lots of turbo failures before it was revealed their map overspun the turbo) is getting it going whilst keeping it clean.
The mappers (word used loosely) tend to chuck in more fuel to get it to spool, and they often smoke a little (or a lot) whilst they build boost.
A twin turbo setup on the other hand usually has the small turbo boosting at 1100rpm, crossover around 2500rpm depending on setup and still good strong boost at the high end of the rev band without excessive emp and or emt.
The twin turbo setup typically produces more power for longer with higher ve .
In view of this I struggle to see how a turbo with a smaller window 'is easier to keep emissions down', tyhe manufacturers work hard on emissions regardless of single, twin or triple turbo setup.
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Ok I'll concede you are right in terms of pure performance where space is not an issue - but on most smaller cars, a twin turbo setup is just not practically viable, thus it is easier to keep the emissions down + keep lag free spooling with a VNT rather than a single big turbo or trying to package twin turbos.
Topic for another day, but compound charging offers a lot of benefits as well, but is a nightmare to actually package.
G-series development had stopped before MGR went bust, they never had anything other than development mules in operation in a couple of 75's, and a ZR/25 iirc - I believe they sold the engine plans off as part of the administration actions during the collapse. I believe they went to Tata or another indian company.
SAIC then were no allowed to use it as a result - My memory might be hazy but I think that is how it went down
