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Registered User
Join Date: Oct 2011
Posts: 12
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Loss of Horsepower
Hi Folks,
New to the forum - found some great stuff here but my searches hasn't revealed a cause of my loss of horsepower. Here's the background. My car is an '87 911 Carrera w/ 3.2 sitting at 93K miles. I just installed a Fabspeed pre-muffler and dual outlet muffler. Valves were recently adjusted and new plugs and wires installed. I haven't done a compression check but the car doesn't smoke and has normal oil consumption. I could feel some sloppy throttle response up to 4K rpm and then it smooths out and pulls pretty good but it just felt down on power. I put it on a chassis dyno today and it was confirmed - peak hp was just 138. The A/F mixture was showing all over the place - rich at the beginning and leaning throughout the mid and upper range 14 - 15. I did a check on the sensors and everything was showing correct voltage and correct continuity/ohms. I did a check on the flow meter and it seemed to be functioning ok but when I checked the ohms through the range of its operation it showed from ~550 to ~1100 up to about halfway open and then dropped back down to ~600 as it went to full open. Anyone know if this is normal? Anyone got any ideas on where the hp has gone? Thanks |
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11-18-2011, 04:47 PM
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Registered
Join Date: Jan 2007
Posts: 11,758
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Do a compression check ? What if your valves are bleeding off compression ?
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11-18-2011, 04:59 PM
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Member 911 Anonymous
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If you can swap out a known good AFM if it clears up then there is a thread from the 944 forum how to re-fresh the AFM potentiometer.
Oh yeah, Welcome Home 
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'85 Carrera Targa Factory Marble Grey/Black * Turbo Tail * 930 Steering Wheel* Sport Seats * 17" Fuchs (r) * 3.4 * 964 Cams * 915 * LSD * Factory SS * Turbo Tie Rods * Bilsteins * Euro Pre-Muff * SW Chip on 4K DME * NGK * Sienes GSK * Targa Body Brace PCA/POC |
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11-18-2011, 05:07 PM
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Registered
Join Date: Aug 2008
Location: sectors R&N, SE Pa
Posts: 3,117
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Here's the link Jim mentions - the potentiometer wiper wears the material away, so your readings weren't normal. I had to hunt as the URL changed. Welcome and good luck. Air Flow Meter (AFM) - from "The 944 Motronic DME" by FR Wilk* ©2001 www.the944.com
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Dan '87 Targa Carrera 3.2 - Fabspeed Cat Bypass, M&K Muffler, SW Chip Venetian Blue |
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11-18-2011, 07:37 PM
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Registered
Join Date: Jul 2001
Location: Portland Oregon
Posts: 7,007
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Did you change software???
If not, that's the first major issue as your exhaust changes really affect AFR's.
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Steve Weiner Rennsport Systems Portland Oregon (503) 244-0990 porsche@rennsportsystems.com www.rennsportsystems.com |
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11-18-2011, 11:46 PM
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Registered User
Join Date: Oct 2011
Posts: 12
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Thanks for the welcome and for the ideas. I did not update the software, next thing to change. I suspect a bad/worn AFM due to the erratic readings. Thanks for the link. I will delve into that this weekend.
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11-19-2011, 05:51 AM
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Registered
Join Date: Mar 2006
Posts: 1,107
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Have someone sit in the car and floor the throttle pedal while you check to see if the throttle can be opened further at the throttle body. Many 911's that are down on power have worn out linkages and it is a nice surprise when you actually get full throttle.
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Paul |
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11-19-2011, 07:26 AM
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Registered User
Join Date: Oct 2011
Posts: 12
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Thanks I'll check the throttle linkage as well. Did take the DME apart and found it had been chipped with an older ('95) Autothority chip. Thinking maybe a Wong chip replacement would help?
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11-19-2011, 09:21 AM
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Northern Motorhead
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Wong chip is definitely a "need to install" thing ... plus you get all the necessary, and more
outstanding customer support from Steve ! Cheers ! Phil
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Cheers Phil 89 Coupe,Black,95 3.6 engine and the list goes on ... 1983 944 SP2 race car PCA #96 |
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11-19-2011, 10:34 AM
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Marble Grey
