Why run so little boost?
30 August 2007, 09:38 PM
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Why run so little boost?
I'm told that the Subaru rally cars run with about 1.8 boost, but the road cars only run .8, so why is this, is it simply a case of reliability?
31 August 2007, 12:06 PM
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Subaru rally cars can run 1.8 bar because they cost a fortune to build 
more than say an STI costs to buy new and they are rebuilt every 1000 miles.
On road going cars its for reliability, though you will find some smaller engined turbocharged cars run 1.6bar standard to the .8 bar that some subaru's run standard.
Tony
more than say an STI costs to buy new and they are rebuilt every 1000 miles.On road going cars its for reliability, though you will find some smaller engined turbocharged cars run 1.6bar standard to the .8 bar that some subaru's run standard.
Tony
31 August 2007, 12:08 PM
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Subaru rally cars also run about 300bhp, but people on here run less boost and get higher bhp than that. The cars may look similar but component wise there is no comparison so you dont get a Subaru rally engine in your car. MAy be the same block, but the internals are a different story.
Just look on the RCM website at cranks for an idea of what I mean
Just look on the RCM website at cranks for an idea of what I mean
31 August 2007, 12:43 PM
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I thought the standard car was something like 15psi or 1.1bar ?
Im sure thats what PSi3 was reading.
Its a fair whop of boost for a standard road car is it not?
Im pretty sure its "average" to most road going turbo performance cars.
As has been said rally car engines cost a whole lot more to build.
Reliablility is the manufacturers interest. With just enough to make you gron and buy it.
Im sure thats what PSi3 was reading.
Its a fair whop of boost for a standard road car is it not?
Im pretty sure its "average" to most road going turbo performance cars.
As has been said rally car engines cost a whole lot more to build.
Reliablility is the manufacturers interest. With just enough to make you gron and buy it.
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31 August 2007, 12:44 PM
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to give you a rough idea a subaru rally engine will cost you 15,000 and a gearbox 45,000 there is so much work envolved in the engine and have been told if it was not for the FIA restrictor it could run around 500bhp
31 August 2007, 03:10 PM
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Just looking around and most people say that their's runs with 0.8, 0.9 that type of thing. I'm trying to figure out what would happen if I ran a standard turbo engine at say 1.5?
31 August 2007, 03:39 PM
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I would say you would be heading towards the limits of your turbo's ability and pushing it all a bit too hard.
31 August 2007, 03:57 PM
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It's a real easy question to answer. The more $$$ you have the more Psi you can run. Think about it, (most) Rally teams have a large amounts of $$$ so they can afford to run highly tuned engines, spend money on testing and research and have access to spare engines if something goes wrong.
If you have access to all of that, then by all means turn you boost up as high as you want.
If you have access to all of that, then by all means turn you boost up as high as you want.
31 August 2007, 04:13 PM
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It isn't just a case of turning up the boost. The air/fuel ratio needs to be sorted aswell as the timing.
Then you have increased heat so you need to look at upgrading the intercooler. Then, due to increased boost pressure, to make the most of it, you need to ugrade the exhaust system.
Excellent, you have more speed potential........bollocks, you now have to upgrade your braking and maybe suspension.
As someone has already said, the £££ you have, the faster you can go!
Then you have increased heat so you need to look at upgrading the intercooler. Then, due to increased boost pressure, to make the most of it, you need to ugrade the exhaust system.
Excellent, you have more speed potential........bollocks, you now have to upgrade your braking and maybe suspension.
As someone has already said, the £££ you have, the faster you can go!
31 August 2007, 04:33 PM
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Safe boost figures = less recalls
If they sent out standard scoobs running there turbo's at peak boost,Fair enough they'd be quicker (and sup more juice) but they'd never reach there desired lifetime mileage without having to be replaced/repaired.
If this were to happen no one would buy them as they'd have a bad reputation for NOT being reliable, Hence safe boost of 0.8 that still reaches the desired power output for that said model.
Hope that helped
31 August 2007, 04:46 PM
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what would be a safe boost to run on an sti ra with a fmic and bigger turbo dont know wot else has been done to it i fiddled with the boost controler wen i bought the car and dont know wot it was at i currantly have been running it at 1.40is this ok?
31 August 2007, 04:50 PM
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Sounds about right, My mate runs 1.5 in his WRX RA but he knows the history of it.
31 August 2007, 04:52 PM
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If you dropped teh compression ratio to oo, say 1.8:1 then you probably could run 10bar boost safetly all day long.
Would drive like an invalid scooter off-boost though
Would drive like an invalid scooter off-boost though
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