billindenver

Where do you guys get this info? I've been running 22psi on pump for a decade without going through head gaskets (on the street, race gas on the track). No crazy stand alone system, just an ARC2 (old huntley) piggyback over APE chips in the stock computer.

So much misinformation out there, one guy says 18psi is the max and all of a sudden it's the gospel. It's cool I guess, some people still believe in the easter bunny, santa claus, GWB and the catholic church. To each his own, but 20 psi is NOT going to grenade a headgasket...ON THE STREET with pump gas. I would look for the real cause or you will be back in there replacing it again.

IMHO of course (backed up by a decade of doing the impossible).

Ski

max boost is where and what you have it tuned for.

I hope there was a WBO2 in the car - I can't see where we spend all the money for performance and then leave a $300 to $550 part out of the car to check the tune.

Like David said, find out why it blew then correct the problem. You'll be lucky if the coolant didn't do a cylinder wash, then get ready for the $$ to start spinning out of control

gvr4111

off topic but

what kind of a/f ratio are you running? I'm setting mine's at right around 11.5:1 at wot. I'm using mafterburner and max chip. I did have to fine tune it bit on both idle/cruise and wot.

KuHL 951

You have to admit though at your altitude you can get by on marginal gas. I've felt the limits of our local 91 octane on a hot day and 17psi but the car still pulled strong at 8300' on the same gas. That tells me that the altitude gives you a better knock cushion than us flat landers. Your 22 might be his 18....maybe not.

billindenver

8 of those years were in florida...running a dozen track events a year. 80k of the 100k on this engine set up were in florida. Can't get much more sea level than that. Watch your heat, keep an eye on A/F ratio and all is well. I still am shocked to see how many people perpetuate the myths started by people like Huntley a dozen years ago....it is nothing short of amazing to me to see how many people will come on a forum like this and shout at the top of their lungs that what they KNOW to be true is fact....without question. When you really look into it, what they KNOW to be true...is something they read on here back when this used to be called Porschefans.com. Ah, the good ole days.

It was BS then....its BS now.

Loquat15

Any bets if the headgasket has been breached on the #4 cylinder?

pole position

Not all pump gas is equal. There is a distinct difference from the east coast 93/94 to the west coast 90/91. If you have the ability to monitor/log knockcount and timing you will get teary eyes with how bad the 91 oct is in comparison to the 93/94.

gvr4111

what kind of knock counts are you getting on 91 oct gas? what boost and a/f ratio? nobody really says what they are running other than it'll knock or blow up.
JBrown is in NY so I'm guessing he was pumping 93...I'm just trying to figure out what's everybody setting thier a/f at. or does anybody care enough to wideband thier cars at all?

billindenver

I don't know about the west coast (who could ever explain why california does anything), but the reason there is 93 in florida and 91 in areas like denver, is for every 1000 feet you go up in altitude you need roughly 1 less octane. In other words at 6000 feet you need far less octane than at sea level. In florida if I put low octane in and then got into the boost for any time at all the knock sensor pulled my timing. Here in denver, I can run 91 all day long without that happening.

So the reason 91 is all you can get is likely 91 is all you could ever need.

billindenver

Wide open I'm at one blue on my in car A/F meter. As I recall from dyno testing that was rougly 12:1...but then that is from a long time ago so I could be mistaken. I only recall that one blue was where the dyno showed I wanted to be..so that is where I have left it. I'm going to the dyno again in the next couple weeks so will update you then.

toddk911

+1

toddk911

Love to have you back on the forums!!

eclou

Fresh motors might be capable of >18# but most of these cars are 140k miles on the original or 2nd HG with spotty states of tune and marginally complete maintenance. I certainly would not advocate cranking the dial to 20+ pounds and dropping the hammer.

billindenver

I have to say it again, where do you get this info? Based on your experience from 20#'s doing damage to a motor you attempted it on? How many 951 motors have you built that have had a problem with 20# of boost?

My car had 75k or so on it when I bought it. I then changed the turbo, put in a maf, removed all boost control, vented the nose and ran it at 22psi where the stock WG would let go. That was 10 years ago, 100k miles and pushing 100 track weekends both in DE and club race. This past fall I finally spun the original #2 rod bearing (because I ran it low on oil on the track) so I pulled the motor. The pistons are still in spec, the bores are still in spec...I replaced the rings and bearings and fully expect another 100k miles without problem. I also put in a tial 46 so needed a boost controller to keep it from severly overboosting.

My pistons have 180k+ miles on them, along with the stock bore. Leakdown was under 4% (as low as my guage would read) on all four cylinders before tear down. If you have experience with 20# killing a properly tuned 951 motor I would love to hear it. In my decade running this one...I have not seen anything to lead me to believe that this wives tale has any basis in fact.

billthe3

You were able to run 22psi with the stock wg? Oh, were there any changes in the design between the 86 and 89 cars? I've been fearing mine is going to crap out once I get above 15psi.