996 turbo questions
Discussion
Having experienced the jap car scene for myself I find it strange that people get hung up on boost pressure.
It's just a number and not a particularly glamourous one. All it really tells you is resistance to flow.
Big turbos running 0.8 bar can give you more power than small ones running 2+ bar (assuming both turbos are on their efficiency islands).
The volume of air is the big player.
It's just a number and not a particularly glamourous one. All it really tells you is resistance to flow.
Big turbos running 0.8 bar can give you more power than small ones running 2+ bar (assuming both turbos are on their efficiency islands).
The volume of air is the big player.
Gazboy said:
I am, but not to compete with Dazren at Brunters (yet), I was just interested in what makes the 911TT tick.
Remeber the underlying engine though - its fundamentally the same 3.6L GT1 derived unit as in the GT3 which manages to shove out 381bhp without turbos and propel the GT3 to recorded 0.60 times of 3.9s and 1/4 mile of 12.07s clicky linky
my 996 TT has been tuned by Revo and is running 0.9 bar, they have also changed the timing so it boosts at a higher pressure lower down the rev range. The car is very reliable and estimated at running 480 bhp as it has sports cats as well. It is definately fast enough the problem is finding anywhere to use all the power. Track days it is then..
I'm getting mine DMS tunned this weekend. They tell me that the standard turbos on the TT are rated up to 1.6 bar for use.
Anyway, here's a link on a older posting I started on this subject a while ago:
www.pistonheads.com/gassing/topic.asp?f=48&h=&t=91642
Anyway, here's a link on a older posting I started on this subject a while ago:
www.pistonheads.com/gassing/topic.asp?f=48&h=&t=91642
glenn mcmenamin said:
I regularly see 0.7-0.8 in my standard turbo, i have seen 1.0 on one very cold night aswell.
G.
I still don't understand this. A charge of nice cold, damp air is great for power because of the increased density/mass air flow so more oxygen into the cylinder - the DME increases fuelling accordingly, but why should cold air give higher boost? The boost pressure is regulated by the waste gate setting, so anything above the maximum allowed by the DME should be dumped off anyway?
The only explanation that I could come up with was that the cooler charge would allow higher boost pressure before detonation. IF the DME then allowed higher boost pressures because of a cooler charge then it would make sense, but Paul Frere's book makes no reference to this increased boost function. He talks of maximum boost pressures of 0.85 and 1.0 bar respectively for the 996tt and the GT2, with the electronically controlled wastegates being used to vary boost across the rev range and reduce it in the event of detonation that can't be solved by backing off the ignition timing.
Marquis Rex or anyone else who can explain this to me where are you?
Gazboy said:
Having said that, a chap on the Supra forum showed impressive gains by changing from the factory intercooler to a large FMIC- surely that's the same as summer day vs winter night?
Not really - presumably he was reducing inlet charge temperatures with a better intercooler, so the ECU would react to the lower charge temperature and increase the fuelling to suit, hence more power. But changing the intercooler alone will not have increased his turbo boost pressure output, though improved flow through a better intercooler would reduce flow losses downstream of the turbo.
I still don't see what gets you around the wastegate setting limiting the boost pressure whatever the inlet temperature, unless there's a very clever adaptive ECU that allows higher boost with lower charge temperature.
Roshambo said:
911 Habit - will be interested on your feedback on this conversion.
I'll show this tread to DMS when they tune my 996TT on Sat. and get some comments from them, which I'll post up.
As far as I know the std. turbos fitted are rated to 1.6 bar, Porsche only allow upto 0.8 on a std. 420 bhpTT - prolong the life of the turbos & engines.
The x50 has bigger turbos and inter-coolers.
May I suggest you pose this question on Scoobynet or lancerregister.com?
I know you may think these cars 'below' the Porsche but there is alot of knowledge there about turbos in general as all Scoobs/Evos are turbocharged. There are literally thousands upon thousands of these cars compared to a 'handful' of 911tt. So experience/knowledge of turbos is extensive
I know you may think these cars 'below' the Porsche but there is alot of knowledge there about turbos in general as all Scoobs/Evos are turbocharged. There are literally thousands upon thousands of these cars compared to a 'handful' of 911tt. So experience/knowledge of turbos is extensive
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