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Old 04-04-2004, 08:11 PM   #1
My02Focus
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Turbo airflow theory

Ok guys I need a little help with something. My brother has a 92 mitsubishis eclipse. On the stock turbo he is running about 19 psi on pump gas and that maxes out his stock 370cc injectors. He upgraded his turbo and now he can max out his injectors with about 14-15 psi and makes a ton more power than 19 psi with the old turbo. the stock turbo was in excellent condition, no shaft play seals area all still good. So I'm assuming that it maxes out sooner because of the larger turbo's ability to flow more air. So does this mean that the amount of boost we can run on our foci varies depending on the size and efficiency of the turbo we are using? Also does anybody know of any datalogging software for the foci, and what is the limiting factor on the zetec engine in relation to boost? Is it the engine internals, tuning, fuel system, or just crappy gas?


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Old 04-05-2004, 01:53 PM   #2
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The reason he has to run less boost with the bigger turbo is becuase he is leaning out sooner.

Bigger turbo (more air) + same fuel = leaner (which means he has to run less boost)

Also i hope he's not maxing out the injectors to anything more than 90% duty cycle. Anything more than that and there is a possibility that the injectors will get stuck closed / open...BOOM!
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Old 04-06-2004, 10:17 PM   #3
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Maxing out the injectors at about 85% and he's not running lean. He has a datalogger and a wideband o2 sensor, so we can monitor all of the engine vitals. Everything is tuned near perfect (running a little on the rich side for safety). So theoreticaly if we are using a smaller turbo than toms gt30 on our foci we could turn the boost up a bit past 9 to 10psi to compensate for the difference in airflow?
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Old 04-06-2004, 10:58 PM   #4
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So certain turbos will move different amounts of air (CFM I think is the rating) at the same Lbs of boost, I though a PSI was a PSI?
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Old 04-07-2004, 12:00 AM   #5
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I simplified my post up there, there are a LOT more variables to take into consideration.

With Toms kit i'm sure he has done all the R&D needed to run his kit with his specific components on one specific car. Change any of these variables and you throw all his R&D and tuning out the window.

PSI is PSI, but the same PSI with a different turbo can give you very different results.
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Old 04-07-2004, 07:11 PM   #6
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Thanks for the info...anybody have any answers for my other questions?
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Old 04-08-2004, 10:01 PM   #7
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well, to some questions, I think the first thing to give out would be fuel system, with internals running very very close behind that, N/A is built to be N/A expecially from the factory. Going past 8-10 PSI on any N/A engine is not a good idea. Further more, MAD hit the nail on the head, PSI is PSI, but different turbos with produce different results. As for datalog software???? But you can get a haltech and hit up a dyno for some logs.
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