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top hat diaphragm


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#1 81zfan

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Posted 03 May 2019 - 11:18 AM

Anyone have a new one or know a place to get just this.
88 conquest, .30 over block,Bs eliminated, M28 head ,17c turbo,Ottowerks shifter bushing, Lower Shores Braided lines and TB parts, Boostinmini TPS conversion kit,Optional Methanol Kit "when hooked up",Custom 2.5 Intercooler Piping,3 inch Downpipe, Gasket Ported Intake and Exhaust Manifold, Manual steering conversion,ACT HD clutch, Ebay knock off GReedy BOV,put car on a diet "lost between 590-620 lbs", Super AFC, AEM wideband, Glowshift Boost,Fuel Pressure, and Coolant Temp gauges, ARP Head and Rod bolts/Studs, Walbro 255.... In the process of adding more !





#2 markhansenconquest

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Posted 03 May 2019 - 06:30 PM

buy the rebuild kit on rock auto........if the diaphram has a hole in it u need a rebuild anyway.............

Edited by markhansenconquest, 03 May 2019 - 06:32 PM.


#3 ucw458

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Posted 03 May 2019 - 09:41 PM

Not needed.  Many SQs, even mine ran without issue after removing that damper.
My 87
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#4 81zfan

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Posted 06 May 2019 - 07:36 AM

Tb is freshly rebuilt. This is for a separate tophat I purchased.
ucw, I was going to try that if I couldn't get the one out of the tophat I had on the car, but luckily I got it out without tearing it.
I've done some research and can't find a definite answer as why they put this damper in there.
88 conquest, .30 over block,Bs eliminated, M28 head ,17c turbo,Ottowerks shifter bushing, Lower Shores Braided lines and TB parts, Boostinmini TPS conversion kit,Optional Methanol Kit "when hooked up",Custom 2.5 Intercooler Piping,3 inch Downpipe, Gasket Ported Intake and Exhaust Manifold, Manual steering conversion,ACT HD clutch, Ebay knock off GReedy BOV,put car on a diet "lost between 590-620 lbs", Super AFC, AEM wideband, Glowshift Boost,Fuel Pressure, and Coolant Temp gauges, ARP Head and Rod bolts/Studs, Walbro 255.... In the process of adding more !

#5 markhansenconquest

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Posted 16 May 2019 - 09:14 PM

The purpose is to stop the pulsation of the gas pump.......When the gas pump is running its pressure varies as the gas is pumped up to the TOPHAT..(.remember regulator is after injectors ,,So injectors feel gas pump pulse !!!!.)..........Each stroke of the gas pump piston puts more pressure on system and the rubber diaphragm absorbs the pulsation between strokes of the  piston...........( to smooth the gas flow.).........................How can u get the car to IDLE SMOOTH without even gas flow ?.......u cant..........................When theirs a hole in diaphragm gas will flow to the spring side and it cant absorb the pulse from the gas pump.... It is locked up and cant move,,,,,,,,,, ,so gas pulsates to the injectors  (no good  how can u control AFRs that like?)......... it needs AIR on the spring side ,so Diaphragm can move back and forth   (freelee)........There not just rubber !!!!! there nilion fabric with rubber molded over.them.....they need to be very flexible to work right ......30 year old rubber parts are shrunk to small to seal..i have rebuild 6 TBIs and they all leaked at the lemon shaped O- ring.......
rebuild the whole thing......
not worth risking a fire from 30 year old seals.....IMO..........

Edited by markhansenconquest, 17 May 2019 - 01:58 AM.


#6 croquest87

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Posted 17 May 2019 - 04:26 AM

There is also fuel dampener right after the pump. Most people end up removing it because it rusts out and could possibly leak/cause fire. Mitsu engineers put it there for a reason but it's most likely NLA part. I removed mine long time ego w out any noticeable difference. I am sure it effects fuel delivery in one way or the other otherwise they wouldn't put it there in a first place.

#7 81zfan

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Posted 17 May 2019 - 07:09 AM

Thanks Mark for the details on how this works exactly.
When I say I removed the old damper out of the Top Hat that was on the car and put it in a different Top hat, the old damper and throttle body has 47 miles on it since I rebuilt it.

Edited by 81zfan, 17 May 2019 - 07:22 AM.

88 conquest, .30 over block,Bs eliminated, M28 head ,17c turbo,Ottowerks shifter bushing, Lower Shores Braided lines and TB parts, Boostinmini TPS conversion kit,Optional Methanol Kit "when hooked up",Custom 2.5 Intercooler Piping,3 inch Downpipe, Gasket Ported Intake and Exhaust Manifold, Manual steering conversion,ACT HD clutch, Ebay knock off GReedy BOV,put car on a diet "lost between 590-620 lbs", Super AFC, AEM wideband, Glowshift Boost,Fuel Pressure, and Coolant Temp gauges, ARP Head and Rod bolts/Studs, Walbro 255.... In the process of adding more !




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