Fastest928

Andy,
I think that you, Mark R and a few others are using realistic boost levels of 5-7 psi.....and most liklely to preserve the integrity of the engine over time.

We have a 928 here making 10+ psi of manifold pressure whcih blew a head gasket, and other report of blowing headgaskets 10-11 lbs also. It makes perfect sense considering the BEMP levels and the level of fuel and ign management of the 928 vs, say a 951. Boost enrichment and ign retard vs, engine temp/air temp is an important part of any boost kit design and one that we are looking into carefully to help solve some of these problems.

I appreciate all the info from folks, and it appears that a "potential" reliable limit, using stock "stuff" is around 7-8 psi manifold pressure with IC. I still think that is is less, more like 5-7 psi, but time, miles and usage will tell.

Andy, how much for autorotor 2300 with manifold? Any chance of a using a wastegate with the autorotor?

Thanks again,
Marc
DEVEK

John..

I totally agree on the boost levels. It is about having a well tuned good running car, not just about posting dyno runs. If you look at the ignition mapping on a 951, you will see at the peak torque, the Motronic pulls out timing, quite substantially, down to about 18-20 degrees I think. Compare this to the 928s 30 degrees max on the early cars and you have a recipe for disaster at anything over about 10 lbs.

GoRideSno

Marc,
The manifold is $880, the Big IC is $835, and the Autorotor 2.2 with the drive and pulley is $1725 ($1725 is the group purchase price and it will be more like $1900 afterwards).
I will be making the GP on the autorotor this morning.
I don't think it would be hard at all to use a wastegate. It could attach to the plumbing that goes to the by-pass valve.

10pis with the Autorotor would make a very fast 928.

You can e-mail me at andy@928supermodel.com

Thank you for your interest.

Andy K

heinrich

very intereting ... things to ponder

Tony

Some, well, a lot, of this stuff is new to me but how would a waste gate be utilized? What purpose would it be used for on an postive displacement SC?

Delaying the onset of boost?
Bleeding it off at a certain point?

Educate me. Thanx

GoRideSno

Tony,
It could probably do both of the things you mentioned but neither are necessary......just more toys. Some smart person could probably figure out a way to use a wastegate instead of a by-pass valve. I haven't tried it yet but I think it would be possible to lower boost w/ the by-pass valve I am using to have a "valet mode".

Andy K

SteveM928

Were they the original head gaskets, and what kind of condition were they in when they blew? Since completely stock 928s have blown head gaskets, and have shown gaskets in poor condition, how much would just be the result of that in those cases of the blown gaskets that have occurred on the supercharged cars? I mean a supercharger would help cause gasket failure more easily on a car that's got gaskets in bad shape already, but you couldn't really blame just the supercharger if those blown gaskets were half rotted away anyway. Is there any information on blown head gaskets from anyone on any supercharged cars that had new head gaskets and proper tuning?

Jim bailey - 928 International

Yes Andy the Ford Lightning opens the bypass somewhat at wide open throttle to reduce boost by about 3 lbs , since there is no manifold vacuum it uses a reservoir to hold vacuum . The Bypass valve is a vastly better way to control boost since it recycles the air back through the blower to avoid cavitation and excessive heat . The "Tuners" sell a simple kit to over ride the wide open reduce boost of the Lightning ( once one experiences boost you want MORE ). Waste gates as the name implies are literally a waste . Why spend the energy horsepower compressing air (and heating it) only blow it off to the atmosphere ! One of the big advantages of the Eaton, whipple , autorotor positive displacement design is the built in bypass valve which lets the car run "normally aspirated " MOST of the time . Then on demand (no vacuum) the engine sees BOOST . I know very little about superchargers but at least I know that I know little ........

GoRideSno

Hey Jim,
I'm coming over this afternoon to get the slicks and wheels. I'll call first.

Andy

2V4V

Marc,

I would be curious as to the post-mortem on that 10PSI blown head gasket.

Was it a fresh gasket set?
Was it properly torqued?
When were the heads last shaved?
What was the finish put on the head surfaces?
How true to 90 deg. (and flat and parallel) were the cylinder wall tops?
How old were the headstuds/bolts and nuts (if applicable)?
Were there any ignition misfire events on the o-scope before the blowout?
What the last reading on the wideband O2 d/a?

That kinda stuff. I ask because the OEM gasket is far sturdier than is used by many guys I know running way more boost than 10 PSI in other apps. And unless you have eliminated all those as causality, tagging it to the "whopping" 10 PSI boost is seems very unscientific. So what was the failure mode?

Curious,

Greg

Fastest928

Greg,
Stock engine do not "blow" head gaskets. In fact, rarely does a S4 engine "blow" a head gasket....you know how they blow right? Drive it hard, laying down some big black stripes, climb the boost curve, and bamo, white smoke....

I have yet to find one person who has experienced this "blown" had gasket scenerio in a stock 928. Mostly, they just leak ...a little bit more every time you start the car......

Sure, there are factors, but I am just trying to understand the existing data and conditions that contribute to reliability and allow a stock engine with boost to acheive long term reliability.

The stock 928 does not have the designed in safety factors of a 951, or MB, Jag or ford, etc. Its ecus are primitive compared to the crop os SC engines today...

Anyway, we have some data from this thread, and I thank everyone who participated.

Let the good time roll!

Regards,
Marc
DEVEK

Lagavulin

Which cylinder? Did the fire ring push out, if so, how much, and which o'clock position using between the intake valves as 12 o'clock?

Or, did the fire ring not push out, but instead split like pushing a soda straw in between two halves of a sandwich? Which cylinder, and what position?

You never did comment on the condition of the blown gasket and you were asked directly twice.

Which by the way, you never answered my questions regarding 32v camshafts. Perhaps if you were more willing to share information, I think it's reasonable that others would be more than happy to reciprocate when in need; otherwise, the opposite can/will occur.

Old & New

Marc,

It was my impression that there needed to be a failure in the combustion process, e.g. detonation, or deterioration of the gaskets. Simply running the car hard at a safe boost level? How to figure what is safe...

Old & New

Marc,

Would you say those engines were adequately intercooled?

2V4V

Marc,

I'm well aware that stock engines generally don't "blow" headgaskets. Neither do force-inducted engines, if they are properly set-up. I learned that about 25 years ago. I used "blown" because last time I checked, it was the standard accepted nomenclature for a failed head gasket of any sort. You gave absolutely zero details on how it failed, so why would I call it other than blown?

So Marc, are you going to perform a scientific test, using d/a to actually see what happens before the gaskets fail? Are you going to just put one engine together right, with all the mechanical stuff validated so that you have a solid test platform to work with and can actually trace it to specifically a gasket issue?

I know the ECU package on a 928 is at best, primitive, and the LH2 is a pain to work with, but one can d/a it, and at least determine what's going on before something breaks/leaks/whatever. Otherwise, you just looking at fire rings and making (educated) guesses.

The way it sounded from your post, you were doing dyno runs or at least "right-foot testing", so I assumed you would've had at least the WBO2 going, and maybe a simple 4 channel d/a running on a laptop on the passenger seat. That's why I asked the questions. I'm not sure if not answering means you're not telling, or you don't do do any standard d/a.

Greg