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Smart quod bastardus
 
fredmeister's Avatar
 
Join Date: Oct 2002
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I leave the boost hose connected during the timing as it is teed off the same line as the vacuum line. The reason this works is that I did some testing on my distributor and it seems that applying vacuum to the boost pot has no effect and applying boost to the vacuum pot has no effect. It appears each can or pot only moves in one direction...so that allows running both lines from a common source.
Thus, to answer your question......YES -----boost hose stays connected because timing at 4000rpm in the driveway sees no boost only vacuum and this has no effect on the boost can.
Does that make it more clear?
You know what bugs me is that tuning experts like Steve at ImAuto and such don't ever chime in on these posts leaving us all hanging for answers......frustrating and disappointing.

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1979 930 Turbo....3.4L, 7.5to1 comp, SC cams, B&B intercooler, Snow Perf water/meth injection, Rarlyl8 headers, Garret GTX turbo, 36mm ported intakes, Innovate Auxbox/LM-1, custom Manually Adjustable wastegate housing (0.8-1.1bar),--running 0.7bar max
---"When you're racing it's life! Anything else either before or after, is just waiting"

Last edited by fredmeister; 02-12-2009 at 03:23 PM..
Old 02-12-2009, 03:18 PM
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Quote:
Originally Posted by fredmeister View Post
You know what bugs me is that tuning experts like Steve at ImAuto and such don't ever chime in on these posts leaving us all hanging for answers......frustrating and disappointing.
Tuners do not give up their timing data because it makes no sense to do this in general terms, especially on an open forum. I've mapped many standalone ecu's and would find it near impossible to express the many variables between each and every load point. There's just too many variables to imply a standard. I can gather the hard data for the engine: bore, stroke, valves, cam, turbo, fuel....and write a "base" map to get the motor running. But that is just crude generalizations secondary to experience, the experience from other systems. From there, it can take a long time to duplicate all conditions in all ranges perfectly on that engine, even though it may be similar to other engines. And I do understand the frustration because we all want those perfect slopes for our boosted motors.
Old 02-12-2009, 04:47 PM
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Ok whats confusing is I see you have a 79 I have an 87 US I guess those dizzys are different. Do you have vacuum advance, or is it just mechanical? Mine is tapped from both sides of the TB. The top port will advance timing on vacuum and retard on boost pressure. Also I thought I was reading that you set your timing further advanced than the factory specs by the number of degrees of retard that you get at full boost. I have always set mine dead nuts on 26 degrees btdc 4000 rpm top hose disconnected and plugged. I personally don't have the guts to advance it more than factory spec especially with the **** gas we get around here. Did you ever get the turbo bracket mounted?
Eric
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87 930 Coupe Red, K27S, Kokeln IC, Rarlyl8 Headers system, Tial 46MM, .9 Bar. "Lola"

81 911SC Coupe Guards Red, Stock. "Zippy"

Last edited by e170drvr; 02-12-2009 at 07:31 PM..
Old 02-12-2009, 07:21 PM
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Quote:
Originally Posted by e170drvr View Post
Ok whats confusing is I see you have a 79 I have an 87 US I guess those dizzys are different. Do you have vacuum advance, or is it just mechanical? Mine is tapped from both sides of the TB. The top port will advance timing on vacuum and retard on boost pressure. Also I thought I was reading that you set your timing further advanced than the factory specs by the number of degrees of retard that you get at full boost. I have always set mine dead nuts on 26 degrees btdc 4000 rpm top hose disconnected and plugged. I personally don't have the guts to advance it more than factory spec especially with the **** gas we get around here. Did you ever get the turbo bracket mounted?
Eric
I thought my post was pretty clear. I have a vacuum retard on one side of the dizzy, boost retard on the other side via another can. They both function independently of each other and seem to only move in response to either boost or vacuum respectively.
Teeing off a common connector hose to one point on the throttle body below the throttle plate since this port will see vacuum at idle (closed throttle) conditions
as well as boost under open throttle.
I set the timing at 4000rpm which is under vacuum at this point with the retard hose connected. Knowing the value in degrees of boost retard that I will see I set the timing value so that under boost it reaches 26-29 degrees max. This means doing a little math depending on the boost retard for your particular dizzy. That winds up to be about 4 degrees BTDC at idle for me from memory.
I don't see the car running worth a hill of beans at factory spec of 5-10 degree ATDC. I tried it at only 0 degrees and it ran like crap so badly it was dangerous. Plus the car exhaust runs extremely hot at retarded timing like that. Since we don't have emissions testing in MI all my emissions crap is gone and no inspection to worry about.
I am running a big intercooler and 0.8 boost to be conservative, but think this may be ok for 1.0 bar as long as I run super premium gas (91-93octane). The final value of 29 degrees is what worries me as I don't have consensus from others if this is dangerous under the above stated condition (1.0bar).
__________________
1979 930 Turbo....3.4L, 7.5to1 comp, SC cams, B&B intercooler, Snow Perf water/meth injection, Rarlyl8 headers, Garret GTX turbo, 36mm ported intakes, Innovate Auxbox/LM-1, custom Manually Adjustable wastegate housing (0.8-1.1bar),--running 0.7bar max
---"When you're racing it's life! Anything else either before or after, is just waiting"

Last edited by fredmeister; 02-13-2009 at 04:54 AM..
Old 02-13-2009, 04:48 AM
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Quote:
Originally Posted by e170drvr View Post
Ok whats confusing is I see you have a 79 I have an 87 US I guess those dizzys are different. Do you have vacuum advance, or is it just mechanical? Mine is tapped from both sides of the TB. The top port will advance timing on vacuum and retard on boost pressure. Also I thought I was reading that you set your timing further advanced than the factory specs by the number of degrees of retard that you get at full boost. I have always set mine dead nuts on 26 degrees btdc 4000 rpm top hose disconnected and plugged. I personally don't have the guts to advance it more than factory spec especially with the **** gas we get around here. Did you ever get the turbo bracket mounted?
Eric
I mounted a bracket I made from steel bar stock that goes from 1 engine mounting bracket bolt to the header collector flange. Not as rigid as factory 3 point mount but better than nothing. I did not want to start cutting my factory bracket and rewelding it since I have not the tools or ability to weld. Plus once done there is no going back to OEM.....(but who would do that now?)
Also made a zork tube that I just installed...lots lighter weight off the turbo now should help.

-----With regards to factory spec didn't the euro version specify 29 degrees versus US at 26 this is my basis for runnig as high as 29?....tell me if I am wrong so that I can change it.....don't wanna do more damage.
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1979 930 Turbo....3.4L, 7.5to1 comp, SC cams, B&B intercooler, Snow Perf water/meth injection, Rarlyl8 headers, Garret GTX turbo, 36mm ported intakes, Innovate Auxbox/LM-1, custom Manually Adjustable wastegate housing (0.8-1.1bar),--running 0.7bar max
---"When you're racing it's life! Anything else either before or after, is just waiting"

Last edited by fredmeister; 02-13-2009 at 05:02 AM..
Old 02-13-2009, 04:59 AM
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Fred, Yes your post was clear on how you set up with the hoses. I'm guessing you have a 930/66 motor. If that is the case the ignition timing according to the factory workshop manual for 930/66 is 29 degrees +/- 1 degee BTDC vacuum hose disconnected. and then for checking again 930/66 2 degrees +/- 2 degrees BTDC at 900 +/- 50 rpm. What I was unclear on is say you measured 6 degrees retard with the hand pump you talked about. are you setting the timing at 35 degrees BTDC at 4000 rpm, with the knowledge that the boost pressure retard will pull it back to 29 degrees BTDC. I just think that might be a bit too much advance. But again the idle timing is supposed to be at 2 BTDC 900 RPM I think you said you are happy with that for off boost response. If you need any of this stuff from the workshop manual, I would be happy to send whatever you need.
Eric
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87 930 Coupe Red, K27S, Kokeln IC, Rarlyl8 Headers system, Tial 46MM, .9 Bar. "Lola"

81 911SC Coupe Guards Red, Stock. "Zippy"
Old 02-13-2009, 06:34 AM
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Looking at this again. If you have a 930/63, 62, or 65. the spec is 31 degrees +/- 4 dgrees BTDC @ 4000 RPM. Vacuum disconnected for checking, and for adjustment it is 5 degrees +/- 1 degree ATDC @ 1000RPM +/- 50 rpm Vacuum hose connected. OK if that is your engine I see what you are talking about 5d ATDC would suck!
Eric
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87 930 Coupe Red, K27S, Kokeln IC, Rarlyl8 Headers system, Tial 46MM, .9 Bar. "Lola"

81 911SC Coupe Guards Red, Stock. "Zippy"
Old 02-13-2009, 06:44 AM
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Smart quod bastardus
 
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Quote:
Originally Posted by e170drvr View Post
Fred, Yes your post was clear on how you set up with the hoses. I'm guessing you have a 930/66 motor. If that is the case the ignition timing according to the factory workshop manual for 930/66 is 29 degrees +/- 1 degee BTDC vacuum hose disconnected. and then for checking again 930/66 2 degrees +/- 2 degrees BTDC at 900 +/- 50 rpm. What I was unclear on is say you measured 6 degrees retard with the hand pump you talked about. are you setting the timing at 35 degrees BTDC at 4000 rpm, with the knowledge that the boost pressure retard will pull it back to 29 degrees BTDC. I just think that might be a bit too much advance. But again the idle timing is supposed to be at 2 BTDC 900 RPM I think you said you are happy with that for off boost response. If you need any of this stuff from the workshop manual, I would be happy to send whatever you need.
Eric
What you described exactly. Those values are pretty close to what I remember now timing to.
I am not sure that 35 degree is too much at no boost conditions because I figure with the low cpmpression motor of 7 to 1 without boost pressure is probably ok. Dynamic compression is still lower than a normally aspirated 911SC wich I have heard run best power at around 35-36degrees advance. Once boost starts building then it retards back to be safe. So far I have been running this way for a year or so now and never detected knock. Though I am not sure I would be able to hear it anyway, and they say damage can be done without audible warning. I have removed plugs and never noticed burning or damage to them so I feel about 90% confident I am ok. The other 10% is what bothers me and I would like some more opinions from gurus off this site.
Appreciate the offer on manuals but I have the complete factory set already and have used it to check against what I could find among the 3 or 4 different factory curves for boost and dizzy advance.
You know my goal is to max hp against a non emission restricted car and without running on dyno and measuring everything to tune to the ragged edge (since I am just a working slob without major fundage) I just wanna get as close as I can myself out of my garage and not hurt my engine.
Fred
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1979 930 Turbo....3.4L, 7.5to1 comp, SC cams, B&B intercooler, Snow Perf water/meth injection, Rarlyl8 headers, Garret GTX turbo, 36mm ported intakes, Innovate Auxbox/LM-1, custom Manually Adjustable wastegate housing (0.8-1.1bar),--running 0.7bar max
---"When you're racing it's life! Anything else either before or after, is just waiting"
Old 02-13-2009, 08:12 AM
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In cars with boost *retard* instead of vacuum *advance*, it's extremely important that retard mechanism works. If it gets stuck, you end up with more advance that you want and possible knock.

I regard boost retard devices a design error. Things should be fail-safe. Thus, vacuum advance with stuck mechanism will only give you less advance (=less power) but never go above pre-set total advance. Thus it's fail-safe.
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Old 02-13-2009, 09:49 AM
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Yeah, would be nice to know if a couple more degrees advance could be used without damaging the motor. like I said mine is set at 26 btdc and I am hesitant to advance it any more than that. at idle I am at 2btdc and when you step on the gas the vac retard goes away and end up with around 5btdc not too bad I guess
Eric

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87 930 Coupe Red, K27S, Kokeln IC, Rarlyl8 Headers system, Tial 46MM, .9 Bar. "Lola"

81 911SC Coupe Guards Red, Stock. "Zippy"
Old 02-13-2009, 09:53 AM
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