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Re: how much boost should a 68mm pulley on a good charger produce? (88mk2g60)

This depends on a few different factors.
Do you have a P&P head?
What crank pulley? (what year is your car?)
Any charger porting?
Cam?
Cam gear?
piston size stock?
If its a stock 1990 Corrado with a stock charger in good shape then you should see 15-16psi at redline (16.5 while bouncing of the revlimiter but this is not good for the charger)
P&P head will decrease the psi
1991&1992 larger crank pulleys will see anywhere from 1-3 psi increase
Porting on the charger "should" increase your psi
a cam will change your psi as will a cam gear's various settings
pistons being larger then stock will cause a drop also
 

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Re: how much boost should a 68mm pulley on a good charger produce? (G60ING)

How much boost should the 68 mm pulley produce in a good P&P head ( mfa ) in a stock 90' G60 (stock piston, cams, crank pulley, etc...)?
 

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Re: how much boost should a 68mm pulley on a good charger produce? (88mk2g60)

I have a stock head and cam and see 17-19 PSI on any given day with my 68MM pulley.....just before 6500 RPM and no bouncing off of the rev limeter.
 

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Re: how much boost should a 68mm pulley on a good charger produce? (88mk2g60)

I hit 15 psi with a 68mm before I got a rebuild, afterwards with a RS port I hit 13 psi. I have been trying to find if there is a leak, but I can't find any.
 

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Re: how much boost should a 68mm pulley on a good charger produce? (TexasCorradoG60)

Quote, originally posted by TexasCorradoG60 »
I have a stock head and cam and see 17-19 PSI on any given day with my 68MM pulley.....just before 6500 RPM and no bouncing off of the rev limeter.

crank pulley?
is your boost above 255 on the mfa?
 

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Re: how much boost should a 68mm pulley on a good charger produce? (G60ING)

Quote, originally posted by G60ING »

boost leaks are the enemy

Tell me about it! I didn't have one before I got the rebuild, but I can't understand why I would get less boost with a port unless there was a leak somewhere. It's very frustrating, I need more boost!
 

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Re: how much boost should a 68mm pulley on a good charger produce? (RockHarder)

pretty much all stock with a 68 mm .. she is seein about 8psi at 3k and 13-14 psi at 6200 rpm .. once in a while she wil see 15psi
 

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Re: how much boost should a 68mm pulley on a good charger produce? (G60ING)

Quote, originally posted by G60ING »
some times when you port you loose psi but gain cfm

this is correct...PSI is a way to measure resistance. porting with increase CFM but lower PSI
 

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Re: how much boost should a 68mm pulley on a good charger produce? (IMNOBUG)

Quote, originally posted by IMNOBUG »
this is correct...PSI is a way to measure resistance. porting with increase CFM but lower PSI

I've been wondering the past few days, after reading a few topics involving airflow, is pressure the true measure of how much "boost" you get, or should CFM (amount of air flowing, correct?) be taken into account? I figure that both would matter, because if you have bigger ports (anywhere) more air will be able to flow, and the whole point is to get more air into the compression chamber to burn at once. At least that's my understanding of it

Someone want to clarify this a bit?
Dave
 

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Re: how much boost should a 68mm pulley on a good charger produce? (G60ING)

Before raise the c/r(8.7:1 aprox.) and a P&P head I hit 255 mfa (17 psi), after that job I hit only 232 mfa. Too much ported ? bad job ?
 

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Re: how much boost should a 68mm pulley on a good charger produce? (blakeyez)

I'm still a bit confused by the whole psi/cfm/port thing, but you're right, the goal is to get more air into the system. To paraphrase what someone else said in a different thread, when dealing in psi you have to be sure you're talking apples to apples. A ported charger (or head) pushing 15 psi vs a stock charger pushing 15 psi are two way different things.
Brian
 

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Re: how much boost should a 68mm pulley on a good charger produce? (ButchHusky)

My motor had 80k and was running top notch with all the basics replaced. The charger was rebuilt to stock specs not too long before I put a 68 on it, 3.5 bar fpr, stage 4 chip and I only saw 11 psi max at redline. I searched and searched for any contributors but everything looked fine. A buddy of mine has the exact setup on his rado but his charger was just built be jabbasport and ported and he only sees 13 max...what gives???
 

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Re: how much boost should a 68mm pulley on a good charger produce? (GTiG6O)

well if you kept the silecer box you probabley didn't get a good seal and they normally leak when taken apart and reassembled. ditch it and get a rallye outlet 3 or 6 fin it doesn't matter, with a dremel and half an hour you can make a 6 fin a 3 fin and there is really no difference in them they just eliminate a leaky silencer box. http://****************.com/smile/emthup.gif
 

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Re: how much boost should a 68mm pulley on a good charger produce? (IMNOBUG)

I have a BBM rebuilt charger (stock spec) and a Neuspeed 68 mm. Correct size belt and the tensioner seems strong, I get 10 psi at 3200 rpm, but only like 10.5 psi at 6000 rpm. I've retightened all connections except the un-reachable ones by the intercooler. I'm hoping to find a boost leak down there.
 
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