awoo
Posted a lot
Posts: 1,506
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Sept 25, 2006 12:33:17 GMT
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ok don't shoot me down in a ball of flames here. I'm just trynig to educate myself a little so i don't talk rubbish.
i understand how a turbo works and no that on more modern cars with fuel injection you need to get the mapping etc done.
but on older more basic cars that use carbs would i be right in assuming that mapping wouldnt need to be done as theres nowt electronic going on?
and if so - do you have to swap carbs over to something more hench when you turbo a normal engine or do they compensate themselves to throw in more fuel when its on boost.
please set me along the right way of thinking if you know about this cause I'm only basing this on what i assume (and thats normally wrong)
cheers! ;D
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Sept 25, 2006 12:42:18 GMT
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No ECU, no need for mapping. Carbs only see airflow so you'll need to have them set up for the application. Most carbs can't work with a turbo - you either need to build a sealed box around them or use a carb that is designed for a blow-through application. Or just fit some constant-velocity bike carbs *n
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Top grammar tips! Bought = purchased. Brought = relocated Lose = misplace/opposite of win. Loose = your mum
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Sept 25, 2006 12:51:12 GMT
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So can bike carbs work with a turbo?
Adam
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1997 TVR Chimaera 2009 Westfield Megabusa
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Sept 25, 2006 12:52:33 GMT
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the fueling may well need to be adjusted too.
i don't see why pretty much any carb cant be used, just run with draw through instead of blow through.
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Sept 25, 2006 12:52:45 GMT
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I am led to belive from a sertian drag racing friend that any carb can be modified to forced induction they just need to be rebuilt to withstand presurised air flow.
I am in the process of putting R1 bike carbs on me V8 merc fed by a supercharger.
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Sept 25, 2006 12:56:56 GMT
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i thought any carb could be used for draw through too. The carb just needs to be converted to work as a boost sensitive carb. that way as boost increases so does fuel
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LowStandards
Club Retro Rides Member
Bigging Up The Sum Sum Man Since '99
Posts: 2,665
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Sept 25, 2006 13:02:02 GMT
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Turning this round a littel (sorry) If i supercharged my Impreza Sport, would the ECU be able to cope with fueling on low boost (7psi) without having to do owt? Surely, all its doing is increasing the air so the ecu would just add more fuel? Someone point me in the right direction, i know nothing about this new fangled technology
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Sept 25, 2006 13:05:44 GMT
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hmm, sounds like a recipe for a popped engine to me!
I doubt the ECU is going to be able to measure the extra air, certainly you will take it outside the range it can measure, thus it will not compensate and you'll have an over-lean mixture -> inevitable kaboom.
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1972 Fiat 130 1985 Talbot Alpine 1974 Lancia Beta Saloon 1975 + 1986 Mazda 929 Koop + Wagon 1982 Fiat Argenta 2.0 iniezione elettronica 1977 Toyota Carina TA14 BEST CAR EVER!!!!!!!! 1979 Datsun B310 Sunny 4-dr 1984 Audi 200 Quattro Turbo 1983 Honda Accord 1.6 DX GONE1989 Alfa 75 2.0 TS Mr T says: TREAT YO MOTHER RIGHT!
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Sept 25, 2006 13:10:58 GMT
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Sept 25, 2006 13:21:39 GMT
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A carb for a draw through application need not be modified, as that is isnt any more dense than atmospheric pressure, it may need tuning a little for the higher air flow though. To get a turbo to work for a draw through application it must have a positive compressor seal, this is becuase when the throttle is closed the turbo is under almost total vacuum and the oil will be drawn past normal seals into the intake.
To get a carb to work as a blow through application various bits need to be changed such as a reference line to the float chamber and a float capable of with standing the pressure. A small ring can be placed before the butterfly, if the pressure line to the float chamber is taken before this and the jet is after it, the carb will richen up as the engine comes on boost.
if the carb is used in a blow through application then a boost regulated fuel pressure regulator and injection fuel pump will be needed, this will maintain the 3psi fuel pressure that the car needs above any extra pressure supplied by the blower / turbo etc. Make sure the fuel lines can take the extra pressure as 10psi of boost will mean up to 15psi of fuel pressure.
The best way to do it with carbs is to get somthing like a metro turbo / R5GTt / Daihatsu turbo carb to start with, they are all capable of taking boost and fuelling accordingly. I think that the CV bike carbs will work in a similar fashion to an SU carb, although i have no experience of this i have seen bikes with turbos and the stock carb setups. They will again need re jetting to application.
As for putting forced induction on an injection car, its depends on the set up, if its air flow meter based then this can be put before the turbo / blower so the engine knows how much air is going into the engine. It will then try to supply the extra fuel needed to make the mixture stoich, if it can! 7psi means around an extra 40% fuel, arethe injectors up to suppling this? If the engine works on a MAP system then the pressure that the map is calibrated up to needs to be known, it may work it may not.
Also if the turbo is fitted then extra fuelling on boost may be needed to keep the pistons cool, this cannot be provided by the stock engine management as it will always try to be around 14:1 a/f ratio.
J
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Sept 25, 2006 13:24:24 GMT
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So it has to be modified?
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LowStandards
Club Retro Rides Member
Bigging Up The Sum Sum Man Since '99
Posts: 2,665
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Sept 25, 2006 13:31:13 GMT
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Its def airflow based on the Impreza. I can fit injectors from the Turbo, so getting fuel there wouldn't be an issue, guess i need to do some research on how the ecu will cope with it... Ho hum!
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Sept 25, 2006 13:31:23 GMT
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what has to be modified?
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Sept 25, 2006 13:31:38 GMT
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come on man, thats about as good/clear a response as you'll find anywhere, if you read it you will get your answer.
PS soz, that was to usedabused.
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Last Edit: Sept 25, 2006 13:32:32 GMT by Mr_Bo11ox
1972 Fiat 130 1985 Talbot Alpine 1974 Lancia Beta Saloon 1975 + 1986 Mazda 929 Koop + Wagon 1982 Fiat Argenta 2.0 iniezione elettronica 1977 Toyota Carina TA14 BEST CAR EVER!!!!!!!! 1979 Datsun B310 Sunny 4-dr 1984 Audi 200 Quattro Turbo 1983 Honda Accord 1.6 DX GONE1989 Alfa 75 2.0 TS Mr T says: TREAT YO MOTHER RIGHT!
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Sept 25, 2006 13:33:53 GMT
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I meant to write "so it has to be modified"
I'm not bieng a curse word on pawpose.............be happy I am.
I'l check back when sober
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Sept 25, 2006 13:34:58 GMT
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good idea! Try to get here about 7am LOL
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1972 Fiat 130 1985 Talbot Alpine 1974 Lancia Beta Saloon 1975 + 1986 Mazda 929 Koop + Wagon 1982 Fiat Argenta 2.0 iniezione elettronica 1977 Toyota Carina TA14 BEST CAR EVER!!!!!!!! 1979 Datsun B310 Sunny 4-dr 1984 Audi 200 Quattro Turbo 1983 Honda Accord 1.6 DX GONE1989 Alfa 75 2.0 TS Mr T says: TREAT YO MOTHER RIGHT!
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Sept 25, 2006 13:38:51 GMT
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even i understood blownimp's post and I'm dense! to paraphrase.... if you're blowing through the carb (air -> turbo -> carb -> engine) then you need a specially sealed carb otherwise the compressed air will blow it apart. or put it in a box which will equalise the pressure i guess? so yes it needs modifying in that you can't use a standard carb. if you're drawing through (air -> carb -> turbo -> engine) you also need to modify it as when your throttle butterfly closes in the carb, your turbo will be sucking on nothing and create a vacuum. which sounds like it'll just pull whatever it can in instead of air, like oil. so modified again. does this sound right? i'm also on a learning curve, just thought if i put down the way i read what was happening it might help usedabused understand too.....
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Never trust a man Who names himself Trevor. Or one day you might find He's not a real drug dealer.
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Sept 25, 2006 13:39:08 GMT
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holy moly, its the middle of the day! For a student i could possibly forgive, but next time get to pizza hut for a buffet to soak it up a bit ok?
As for the carb under pressure, the real problem is stopping the fuel curse word out everywhere, usually when the float has collapsed. That or not using a pressure regulator so the engine "wont rev over 4500rpm" this is usually the point where the fuel gets pushed back down the fuel line. If that happens then you will melt pistons pretty quick.
J
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Last Edit: Sept 25, 2006 13:42:10 GMT by Blown_Imp
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Sept 26, 2006 9:43:44 GMT
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Hey I work nights you wouldnt think twice about coming home at six and slurping a cold one or two??
Yeah I read threw again and it all makes snce now,As for pizzas chicargo town all the way !!
PAHH to pizza slut............
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turbosRobinxr4i
@robinxr4i
Club Retro Rides Member 143
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Sept 26, 2006 12:00:53 GMT
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if you're drawing through (air -> carb -> turbo -> engine) you also need to modify it as when your throttle butterfly closes in the carb, your turbo will be sucking on nothing and create a vacuum. which sounds like it'll just pull whatever it can in instead of air, like oil. so modified again. As soon as the throttle is closed, exhaust gas pressure would be reduced and the turbo would stop spinning at a rate where positive boost is created. So I can't imagine you would need to modify the carb (as the vacuum/low pressure created would be no greater than that created by the piston). Anyway when the throttle is closed air still gets though odviously otherwise the engine would stall, so i am not convinced. But if anyone has more info please say! What production cars run the turbo (not supercharger) after the throttle body? As for the superchager on the impreza sport engine the standard ecu left to its own devices could not handle 7 psi of boost. I would imagine the engine management could be altered to handle that amount of boost, but you would need extra sensors like a 2-bar map sensor to know whats going on in the inlet manifold (as the n/a one cant record boost!) Even if the managment was sorted I don't know what the CR. of the standard sport pistons is? Probably easier to get a turbo engine instead!
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Sierra - here we go again! He has an illness, it's not his fault.
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