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Turbofrog
 
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Join Date: Aug 2009
Location: Europe
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Turbo spool vs. timing with CIS

What are your findings over this with different sized turbos?

It seems spark timing (heat) has a huge effect on turbo spool so turning the distributor a bit can make your car spool early and make wild boost (over your WG spring) or spool late and boost low (under your WG spring on lower gears) but still run pretty good in both cases. Advanced timing feels more like NA cars so I like the feel of it when not on boost. I'm not sure yet which setup is faster though. I could not pull any runs in my usual test spot so I could compare runs but this new setup feels faster but the atmo has been cooler now.

I dialed more advance in small increments and made some runs and the turbo spools now at about 4000rpms on lower gears and the car goes strong with about 0.8bar (3rd gear) and with much less boost on 1st and 2nd gears. Earlier it would spool already after 2000rpms and WG could not limit the boost so I had 1.1 to 1.2bar on 4th gear. It still starts to spool (slowly) after 2000rpms on 4th gear.

Earlier it would also spin the tires on 1st gear when the boost romped on wildly. Not anymore and I bet the engine temps are much lower now too.

I made some high speed wot runs too and the engine did not ping or give any signs of trouble and the max boost on 4th was 1bar so I might stick to this timing setting (you don't want to copy my timing values so I won't publish these!). Interesting to see if WMI will lower the boost too.

I just wanted to let you know that the 'norm' timing really does not work on my engine. It would suck donkeys balls to run with less than 10BTDC on idle on my engine, don't know why! I have 1mm~0.4 spark gap with superconductor wires, MSD6A , vacuum pot plugged on dist and single plugs so your setup/results can be different.
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Last edited by smurfbus; 08-25-2011 at 03:39 AM..
Old 08-25-2011, 02:23 AM
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You know this is a very interesting question, sorry I can answer, but am curious to know the same. The reason being is because I am running my stock distributor on my SC conversion and I swear my boost comes on later than it should.
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Jeremy C.
Why's he calling me meat? I'm the one driving a Porsche. (Bull Durham)
----Nothing is far away in this car!----
-1978 911 SC TURBO, Minerva Blue Targa 965 update.
-2008 550i M-Sport
Old 08-25-2011, 03:10 AM
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Crotchety Old Bastard
 
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Yes there is cause/affect. We use a custom curve on the distributors to increase throttle response, quicker spool, and more torque off boost.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
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Old 08-25-2011, 03:28 AM
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Turbofrog
 
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Brian: How do you cope with the curve vs. different loads in different situations. There is no load input so you lose some on cruise vs. good spool? I guess some retard at about 2000-3000 rpms would help my car too but that's the normal driving rpms where I also want some torqy advance.
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Old 08-25-2011, 03:32 AM
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Interesting, I guess I will not know how late my boost comes on until I install my boost gauge, but it seem like at least 4000 rpm at WOT. But at 4K with a 7200 11.11 is really late if in fact that is when it is.

I have taken of the vac advance line, but am thinking to retard a few degrees as well. I would hope to then start to see boost around 3K, maybe a little sooner. How many degrees should it be retarded for such an adjustment?
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Jeremy C.
Why's he calling me meat? I'm the one driving a Porsche. (Bull Durham)
----Nothing is far away in this car!----
-1978 911 SC TURBO, Minerva Blue Targa 965 update.
-2008 550i M-Sport
Old 08-25-2011, 04:27 AM
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My car starts to boost @ 2600. That's about .4 bar. I get full boost of 1.0 bar at 3200.
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Old 08-25-2011, 04:35 AM
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As Brian mentioned, the ultimate is a custom timing curve . I can't tell you how timing affects turbo spool-up, but advancing your timing does have a significant affect on low to mid range power. Just don't get carried away and have too much timing in place when on boost.

I run with 12 degrees advance (that's with the vacuum lines attached to the dizzy) and use a simple MSD boost timing retard module to progressively retard off the extra timing in response to boost as it builds. I do have better throttle response and more torque off-boost and don't seem to notice any negative impact on-boost, but that's all just seat of the pants dyno.
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Old 08-25-2011, 05:03 AM
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Do you guys know how an SC distributor differs from a 930 and how I should then set mine? Thanks.
Old 08-25-2011, 09:08 AM
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Smurf, any further findings?
Why do you have the vac pot plugged on the 930 distributor?

Thanks.
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Jeremy C.
Why's he calling me meat? I'm the one driving a Porsche. (Bull Durham)
----Nothing is far away in this car!----
-1978 911 SC TURBO, Minerva Blue Targa 965 update.
-2008 550i M-Sport
Old 08-29-2011, 01:05 PM
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Turbofrog
 
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Haven't driven the car after the first post. My oil pressure sender broke (gauge pegged)

I keep the vac pot capped for more advance on idle and vacuum. My car really does like more advance on idle. It runs like crap if less that 10 BTDC on idle.
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Old 08-29-2011, 07:47 PM
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Well I set the timing to 28 BTDC at 4500 and there was no noticeable difference. Boost still does not come on till 3600
Old 08-31-2011, 04:12 PM
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2011-08-31 7 PM Taiwan time, I took a STOCK 1992 965 turbo out to dial in 0.95 bar of boost and fuel ratio.
modification to 965 turbo is.....final muffler....it is a very quiet Porsche..
This is first time I drive a stock 930/965 turbo...

I install air intake kit ($90 USD) and a mini boost controller ($10 USD ).
I got 1 bar of boost at 3000 RPM. I thought 930/965 turbo full boost is at 4000RPM????

I remember some turbo builder told me, turbocahrger is good at blowing air not good at sucking air take. At dyno test my 1986 Carrera with EFI 965 turbo motor cannot pass 350 RWHP mark, after the dyno I took it out for road drive I took out cone shape air filter.
It is a beast after I took out the airfilter, I have to turn down the boost. ...
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Old 08-31-2011, 04:43 PM
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Do you think bc the advance pot being disconnected would have an effect? I did not want to reconnect til I checked my AFRs again.
Old 08-31-2011, 04:48 PM
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