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Photo of Worn Out Wastegate Diaphragm

Photo of Worn Out Wastegate Diaphragm.
When this slowly fails you develope boost creep and your over boost.

Old 08-14-2011, 04:26 PM
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Old 08-14-2011, 04:27 PM
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sudo apt-get purge 930
 
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So I should buy a boost gauge with a tell tale huh?
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Old 08-14-2011, 04:29 PM
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Dude, what's a little boost creep when you're running 1.5 bar of boost. The bottom line: every little thing had better be perfect. Living on the edge is a wonderful thing.
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Mark H. 1987 930, GP White, Wevo shifter, Borla exhaust, stock everything else. The result of a massive Pelicanite good will fire recovery effort. Truely an open book, ready for the slippery slopes to modification.
Old 08-14-2011, 05:22 PM
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What is your compression ratio and fuel to be running 1.5Bar?
Old 08-14-2011, 05:32 PM
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NY:

Let's see here !!!!! 3.5L, 8:1 CR, and 1.5 bar of boost.

Can you say INSANE !!!!!!!!!!!!!

That's not an engine it's a $20,000 hand grenade !!!!!!!!!!!!!

Cole
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Cole - 80 930 "The Old Sled"
Mods: TurboKraft Custom IC, 934 Headers, GSX 61, Zork, Port Work, SC Cams, Air Mod Fuel Dist Relocated, Water Meth Injection, BL WUR, MSD 6530, Greddy EBC, Synapse Bov, Short 2nd & 3rd with 8:37 R&P, Wevo Shifter, Coupling, and Mounts, MTX-L SSI-4, Big Brakes, Rebel Coilovers, Bilstein Sports.
Old 08-16-2011, 06:58 AM
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Sounds like you need to buy one of my two wastegates for sale..
Old 08-16-2011, 08:11 AM
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NY:

From your previous post it is evident you need to do some self educating on 930's
before you go much further because this s=== gets real expensive real fast otherwise.

The 3.3 Turbo came stock with 7:! compression and under boost of .8 to 1.0 bar that compression ratio will easily become 11:1 to 13:1. Starting with an 8:1 compression ratio with no boost I can't even imagine what that compression ratio was at 1.5 bar, obviously enough to split a cylinder. At that compression ratio and 1.5 bar of boost there is no way you weren't also experiencing detonation unless you were running racing fuel and seriously retarded timing.

The factory put set specifications for these cars in the manuals, 26* of timing advance and timing retarded on boost, .8 bar wastegate springs, and a boost cutoff switch.They added those restrictions for one reason "they will blow up if you exceed them"

I did notice you have some of the needed mods to run a little more boost, larger IC. good exhaust, more fuel, etc. but 1 bar is still the most you should be attempting without race fuel, EFI, or WMI. And making sure the wastegate is working properly and the cutoff switch is hooked up are a must. Your biggest safety is your right foot, especially if you see the boost gage approaching 1 bar, if you see it going past 1.0 bar back off and if you wait to look at the telltale boost needle it's already too late.

Cole
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Cole - 80 930 "The Old Sled"
Mods: TurboKraft Custom IC, 934 Headers, GSX 61, Zork, Port Work, SC Cams, Air Mod Fuel Dist Relocated, Water Meth Injection, BL WUR, MSD 6530, Greddy EBC, Synapse Bov, Short 2nd & 3rd with 8:37 R&P, Wevo Shifter, Coupling, and Mounts, MTX-L SSI-4, Big Brakes, Rebel Coilovers, Bilstein Sports.

Last edited by cole930; 08-16-2011 at 09:17 AM..
Old 08-16-2011, 09:08 AM
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Hi Cole,
There was some cross info from another poster.
I have the following:
- 3.5L
- .8 Bar Spring
- K27 7200
- After Market Half Bay IC
- Headers
- 7.5 to 1 Malhe Pistons
- Raceware Studs, Nuts & Bolts.
After the single cracked cylinder and rings on two or three cylinders, the pistons looked great. So detonation was ruled out.
Old 08-16-2011, 09:23 AM
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Sorry guys, the mis-information was my fault. In a NY930 previous post on cracked cylinders (which I just re-read) Aussie Thunder had commented on someone's setup with 1.5 bar boost. My inattention and foggy memory linked that to NY930's actual situation.

Maybe I should be banned from the forum for 30 days for spreading falsehoods....or at least beaten severely upon the head.
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Last edited by mark houghton; 08-16-2011 at 10:31 AM..
Old 08-16-2011, 10:16 AM
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"So detonation was ruled out"
by who or what..?
Old 08-16-2011, 10:26 AM
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Someone told it to stay away !!!!!

Cole
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Cole - 80 930 "The Old Sled"
Mods: TurboKraft Custom IC, 934 Headers, GSX 61, Zork, Port Work, SC Cams, Air Mod Fuel Dist Relocated, Water Meth Injection, BL WUR, MSD 6530, Greddy EBC, Synapse Bov, Short 2nd & 3rd with 8:37 R&P, Wevo Shifter, Coupling, and Mounts, MTX-L SSI-4, Big Brakes, Rebel Coilovers, Bilstein Sports.
Old 08-16-2011, 10:38 AM
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Again, here is the basic chart from Porsche Engineering for this engine. On this board members with built engines and twin plugging have run at 12.5:1 effective compression with limited success.




Old 08-16-2011, 11:01 AM
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Hi Guys,
Thanks so much for your input. I would love to get to the cause of the cracked cylinder for two reasons.
1- Because I'm scared $hitless that it will repeat a $econd time.
2- So others may be spared a similar very disheartening experience.
If I had become more knowledgeable then as I am becoming now, because of this valuable exchange of Pelican experiences, I may have prevented this very costly failure.
The inspection of the pistons were made by my shop and the non heat damaged condition, seemed to suggest that the pistons were unaffected by the events that caused the broken rings and cracked cylinder. It did not seem like a heat generated detonation.
What was evident, even after the rebuild, was the distributor advance and retard were non functional and required a new separate advance/retard pod that simply attaches to the side of the distributor.
When the car was droping off the torque curve before 4,000 rpm, I did research on this forum and many members suggested to check the advance/retard.
When I suggested this to my mechanic he said "many 930's he services are running fine without advance/retard.
Then, I insisted on installing this very easy $150 part.
Then the car pulled hard into the upper rpm range like the difference between night and day.
So, what do you boys think?
What may have contributed to the broken rings and cracked cylinder?

Last edited by NY930; 08-16-2011 at 02:59 PM..
Old 08-16-2011, 02:46 PM
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Look I'm going to catch hell about this one but the way I see it you have 3.5L and 8:1 compression ratio. Both of these should produce adequate off boost torque to overcome the miserable 4 speed.

If you are going to drive around using any gas station pump premium I change my recommendation down to .6Bar. This is 9psi boost....and have another shop check your timing.

There is nothing mysterious about why many built TURBO engines spend most of their time in the shop - too much boost.

Last edited by copbait73; 08-16-2011 at 04:16 PM..
Old 08-16-2011, 03:36 PM
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7.0:1 > 11.3:1
 
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Quote:
Originally Posted by NY930 View Post
he said "many 930's he services are running fine without advance/retard.
"running fine",..... as long as you don't put your foot into it! The boost retard is there for a reason, that reason is called "pump gas".

Detonation = broken rings. Most commonly results from boost being increased above factory setting.

edit: solid advice provided above by copbait. This will bring longevity to your engine.

Last edited by Jim2; 08-16-2011 at 05:07 PM..
Old 08-16-2011, 04:59 PM
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If we had any sense we would all follow Marty's advice. But then again I never did learn not push the envelope. Always remember knowledge is power, know the risks, prepare the best you can, and have at it.

Cole
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Cole - 80 930 "The Old Sled"
Mods: TurboKraft Custom IC, 934 Headers, GSX 61, Zork, Port Work, SC Cams, Air Mod Fuel Dist Relocated, Water Meth Injection, BL WUR, MSD 6530, Greddy EBC, Synapse Bov, Short 2nd & 3rd with 8:37 R&P, Wevo Shifter, Coupling, and Mounts, MTX-L SSI-4, Big Brakes, Rebel Coilovers, Bilstein Sports.
Old 08-16-2011, 06:38 PM
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The only time its cool to run big boost is on a built motor ready for it, usually a twin turbo application. My motor can run 1.6 bar but not for long, and it has over $80k in goodies...and it still would blow if run for too long. It is a 8.5:1 and wait for it, designed with running this boost in mind. Unless your heads are seriously modded, flame ringed with full Ti valve train and motorsport triple springs, a $10-20k engine management system more advanced than the space shuttle and about a billion other things - you'll be rebuilding the damn thing every weekend.

Unless you're trying to do something insane like a standing mile etc. dial it back and put the penis measuring stick away.
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Old 08-17-2011, 03:54 AM
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Quote:
Originally Posted by cole930 View Post
If we had any sense we would all follow Marty's advice. But then again I never did learn not push the envelope. Always remember knowledge is power, know the risks, prepare the best you can, and have at it.

Cole
Agreed, my cars are toys and if I push too far I just put them into my shop and as I tell my sons "fix what breaks". Still, most of us have limits on how much fun we can afford.

Following the related posting it is obvious he wants availability and high performance without the issues relating to pushing the limits. This is the reason I keep coming back to fixed compression vs. boost standards published by Porsche Engineering for everyday use, which included sustained Autobahn runs.


My point about fuels is valid, as this data is over 33 years old and they couldn't imagine how pump premium gas would become more akin to goat piss than fuel.
Old 08-17-2011, 07:06 AM
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