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Oh the Lag is Killing Me!!

I know this may be tough to answer but any idea why I am not seeing boost until 3800? I have 993 HEs, MK Y pipe, and 7200?
Thought it might be timing related but it didn't change after setting. The one thing I havent done yet is reconnected the vac advance pot to my SC distributor. But did t want to do this until I rechecked my AFRs.
Discuss, Out.

Old 09-02-2011, 07:42 AM
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You're not seeing anything until 3800? And at what RPM are you seeing full boost?
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Old 09-02-2011, 07:50 AM
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Well, I may have jumped the gun with this post Because I do not have my gauge installed yet. IT is only 0.5 bar, so could it be possible full boost is at 3800? To me that still seems late.
Anyway, when it does hit 3800, she flys, but lag to that point seems like an eternity.
I suppose I really should have waited until I received and installed my gauge. It just shipped, So hopefully next week!
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Jeremy C.
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Old 09-02-2011, 07:59 AM
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Don't recall, is your motor a 3.0L SC with turbo added?
Old 09-02-2011, 08:28 AM
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I'm not sure how different it will be with SC compression, you'd expect it to be even quicker..... I honestly don't know.
What i would say, and happy to be corrected, but for you running 0.5bar that 7200 is too big a turbo. You want something that spools instantly, a little Garrett maybe? Or a K16/24 type hybrid?
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87 930, 993 turbo engine, RS Tuning 520PS/515lbf-ft, Arrow Rods, ARP hardware, Solid lifters, G50-50, RS Flywheel, 890nm Sachs clutch, RSR coil overs all round, 993 C4 calipers front, 930 fronts on the rear, Ruf Speedlines.....
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Old 09-02-2011, 08:30 AM
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Yes it is a 3.0 SC with Turbo added.
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Jeremy C.
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-2008 550i M-Sport
Old 09-02-2011, 09:13 AM
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You'll need to know your A/F ratio to know if it's fuel or timing related.. Both can affect spool up
Old 09-02-2011, 09:29 AM
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Don't I recall you have a Precision BB unit vs a 3K -7200?
Old 09-02-2011, 10:18 AM
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AFRs were 12.9 Idle, 14.3 at 3 K and 10.8 WOT.

No, K27 7200 11.11

Could be possible there is a leak?
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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!----
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-2008 550i M-Sport
Old 09-02-2011, 10:26 AM
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so when you floor the throttle at 3000rpm your a/f is in the 14's?
Old 09-02-2011, 10:43 AM
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I will have to double check again. But the 13.9-14.3 was notied when cruising at ~3K.
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-2008 550i M-Sport
Old 09-02-2011, 10:47 AM
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ok, that will be good to watch because if it drops down into the 10's when you floor it that could cause slow spool up for sure. 2 things can be done, advance the timing or lean it out.... Or both
Old 09-02-2011, 10:51 AM
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Interesting. I thought I was suposed to be in the high 10s when on boost.

Do you think having the vac pot disconnected would have anything to do with it?
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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 09-02-2011, 10:58 AM
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it's ok to be in the 10's at full boost but if it's in the 10's before boost hits you're going to get lag
Old 09-02-2011, 02:31 PM
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if you are loosing some ignition advance by leaving that disconnected I would say yes
Old 09-02-2011, 02:32 PM
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Still getting some info. Isn't your engine a pressurized CIS system? On my turbo conversion I protected all my vac lines with check valves. Is you WUR straight vac driven?
Old 09-02-2011, 02:43 PM
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Yes wur is straight vac driven. I took a very low mile complete 930 cis and put it on my SC engine. Added 993 hes, mk y pipe, 7200 and viola!
Old 09-02-2011, 06:16 PM
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The 7200 hits 1bar @ 3K rpm with Euro exchangers and my muffler. With the 993 setup you should knock 200-300 rpm off that number so you're about 1000rpm out.
> Is the charged air getting too hot?
> Check ignition timing.
> Boost Leaks.
> Turbo worn out?
> AFR's too rich? (check your plug type as you have an SC)
> Ignition weak?
> Exhaust occluded?
> Waste Gate(s) functioning properly? (check boost line & vent)
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Old 09-02-2011, 06:49 PM
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Quote:
Originally Posted by jcc911 View Post
Yes wur is straight vac driven. I took a very low mile complete 930 cis and put it on my SC engine. Added 993 hes, mk y pipe, 7200 and viola!
What's a vacuum driven WUR? Yeah, there's a "vacuum line" attached to it, but it has nothing to do with vacuum and everything to do with transmitting a boost signal to the WUR to enrichen during boost.
Am I missing some cool mod here or is it just my narrow minded 930 view of things?
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Old 09-02-2011, 06:57 PM
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Your ignition timing would cause this. If you dont have the vacuum retard hooked up you will not get the car to accelerate worth a dam until 3500rpm or so when the mechanical advance has come in.
Try hooking it back up and making a run to see what I mean. You wont be able to generate a significant amount of boost until higher gears and heavy load so you should not damage the engine by this little test.

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Old 09-02-2011, 07:33 PM
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