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Registered User
Join Date: Dec 2014
Posts: 16
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3.2ss on throttle bodys
Hi guys I'm back dating a 3.0sc to St, engine all fine but as is the usual with these things you set off the great self control and then you wake one morning a complete dribbling mess and weakness takes over so I have moved to marhle 3.2 pc, twin spark,964 oil pump crank triggered ignition and throttle bodies.
My problem is the selection of camshaft for electronic injection, as my history is with ford bdg engines and reading most of the posts it seems that the factory cams are well up to the job my issue is that an "s" cam is suited to mech injection would this suit electronic or should I be looking towards something a little more modern, I do have chance of a pair of 964rsr but unsure how savage these are. The car is not a completion car, street use and track days only. |
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07-25-2015, 11:52 AM
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Registered
Join Date: Jun 2003
Location: Camarillo, Ca.
Posts: 2,418
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Typically, the lobe center for EFI engines are wider than the early cams. 108-112 degrees. If you intend to run individual throttle bodies you may be able get a narrow lobe center to work well.
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07-25-2015, 12:27 PM
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non-whiner
Join Date: Aug 2012
Location: Slightly right of center
Posts: 5,235
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Check out Clewitt's web site. You can run a trigger on the pulley, cam, or flywheel and then use any cam that fits your needs.
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"Too much is just enough." |
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07-25-2015, 12:45 PM
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Any hot 3.2 cam or 964 cams would suit your setup just fine.
Last year I built an almost identical engine and it used o.e. 964 cams.
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1973 Porsche 911 RS 1981 Porsche 931 Euro-Intercooled-GT 1984 Porsche 911 Euro Carrera widebody 1987 Porsche 924s Rallye Spec Instagram: @soyracer |
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07-25-2015, 02:19 PM
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I would rather be driving
Join Date: Apr 2000
Location: Austin, TX
Posts: 9,108
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The cam choice will depend on many factors. As Aaron (Burn Bros.) mentioned the lobe center is a factor in EFI setups. The tolerance toward narrow lobe centers will depend on your choice of EFI systems. In general, there is Speed Density and alpha-n methods for determining engine load. Speed density relies on manifold pressure or a MAF. Alpha-n relies on throttle position. They each have advantages and disadvantages depending on the motor build. In simple terms, if you have narrow lobe center cams there will be considerable low speed reversion. This intake pulse can make it difficult to get a clean sensor signal to meter fuel. In this case, a wider lobe center will calm down the intake pulse, clean up the manifold pressure signal and allow for easy tuning. Alpha-n is tolerant of these reversion pulses but there are often cross-over points for load when you change gears meaning a low throttle input may need a little or a lot of fuel depending on gear and car speed.
So, figure out what EFI system you are going to run - how you are going to tune and then choose the best cam for the rpm range and power goals. Your EFI system should be chosen by the person that will tune the car. Use your tuner's favorite and familiar system. My 3.2SS runs a DC-40 cam on a 108 lobe center on TWM ITBs. I run pure speed-density and was right at about 300hp. Indeed a fun motor.
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Jamie - I can explain it to you. But I can not understand it for you. 71 911T SWT - Sun and Fun Mobile 72 911T project car. "Minne" - A tangy version of tangerine #projectminne classicautowerks.com - EFI conversion parts and suspension setups. IG Classicautowerks |
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07-26-2015, 07:07 PM
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Registered
Join Date: May 2008
Location: Austin, TX
Posts: 201
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My 3.3SS with Hargett ITBs runs mostly alpha-n but with a manifold pressure modification at the extremes. I too have a Daugherty cam with 108 love separation, but mine is the DC-60. It takes a little while to come on cam, but it is fun when it does.
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07-26-2015, 07:14 PM
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Registered User
Join Date: Dec 2014
Posts: 16
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Quote:
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07-27-2015, 07:51 AM
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Q-P
Flat Out
