X-Pipe, No Cats, RMB, NO GAIN!!!
10-21-2005, 06:32 AM
#17
What I mean to say is my car was running fine, seemed a little sluggish, so I replaced the MAF at 60 K. Picked up 10 HP off the bat and more low end throttle response. O2 sensor had already been swapped. YMMV
10-21-2005, 07:50 AM
#18
Rennlist Member
Aged MAFs tend to run weak, rather than rich...S4s are well known for running too rich at the top end.
The X pipe should have helped weaken it out a bit, though.
The X pipe should have helped weaken it out a bit, though.
10-21-2005, 01:01 PM
#19
Drifting
Methinks that something else is afoot...
I don't run supercharged engines that rich, there is a system failure causing Ernest's GT to run that fat. I believe there is more horsepower to be found there or maybe it's the dyno's O2 sensor system? At 10/1 you would be blowing an easily visible amount of black smoke out the pipes.
I also did not see in any of my development runs where the system with cats performed as well as the one without. The system was designed with maximum horsepower in mind, without cats. The restriction of the cats actually disrupts the scavenging effect of the X a small amount. If Ernest's GT ran the same numbers without cats, something else is the limiting factor.
Just drop it by the shop for a couple of weeks Ernest, we'll figure it out...
But you need to find your own ride home. We can't drop you off and be back by lunch.
I don't run supercharged engines that rich, there is a system failure causing Ernest's GT to run that fat. I believe there is more horsepower to be found there or maybe it's the dyno's O2 sensor system? At 10/1 you would be blowing an easily visible amount of black smoke out the pipes.
I also did not see in any of my development runs where the system with cats performed as well as the one without. The system was designed with maximum horsepower in mind, without cats. The restriction of the cats actually disrupts the scavenging effect of the X a small amount. If Ernest's GT ran the same numbers without cats, something else is the limiting factor.
Just drop it by the shop for a couple of weeks Ernest, we'll figure it out...
But you need to find your own ride home. We can't drop you off and be back by lunch.
10-21-2005, 01:48 PM
#20
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Hey Dave,
No visible black smoke and the various runs were with two different O2 sensors on the same dyno. (Unrelated problem necessitated a new sensor). According to John Speake a weak MAF will usually result in a lean condition.
Any ideas as to possible causes?
You gonna let a few miles get in the way of customer service??
BTW, Roger's back and I told him there was a recall on the X-pipe so we sent it back to you.
No visible black smoke and the various runs were with two different O2 sensors on the same dyno. (Unrelated problem necessitated a new sensor). According to John Speake a weak MAF will usually result in a lean condition.
Any ideas as to possible causes?
You gonna let a few miles get in the way of customer service??
BTW, Roger's back and I told him there was a recall on the X-pipe so we sent it back to you.
10-21-2005, 02:46 PM
#22
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If you look at all my dyno runs (about 15 of them), Roger's runs and Jim's runs you'll see that all of the runs end up in the 11:1 range. I understand that the S4 and GTS cars tend to run rich and that's the SAME curve I'm seeing stock, with cats, without cats, with anchovies and without pickles. There's NO DIFFERENCE in the air fuel curves under ANY conditions. I'm not seeing ANY leaning out with reduced restriction.
Any thoughts on what might cause this other than a bad dyno?
Any thoughts on what might cause this other than a bad dyno?
10-21-2005, 02:52 PM
#23
Drifting
Hey John,
I think we were both talking about the O2 sensor used by the dyno system, not the one installed in the car. They use an air supplied external one that slides up the tailpipe. (I wonder how many hits that will get on a **** search?)
A faulty fuel pressure regulator or dampner can cause an excessivly rich condition depending on how it failed. I have had dampners fail in the bellows and rupture pumping raw fuel into the vacuum system and thusly straight into the intake.
Roger's new-updated/repaired...better X-pipe will ship today. I'm just glad he didn't see the reason for the recall...that thing couldn't have functioned well! It was made for a GT, not a GTS...
I think we were both talking about the O2 sensor used by the dyno system, not the one installed in the car. They use an air supplied external one that slides up the tailpipe. (I wonder how many hits that will get on a **** search?)
A faulty fuel pressure regulator or dampner can cause an excessivly rich condition depending on how it failed. I have had dampners fail in the bellows and rupture pumping raw fuel into the vacuum system and thusly straight into the intake.
Roger's new-updated/repaired...better X-pipe will ship today. I'm just glad he didn't see the reason for the recall...that thing couldn't have functioned well! It was made for a GT, not a GTS...
10-21-2005, 03:42 PM
#24
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AHA!!!! So I saved Roger from a potentially serious problem!! Whew, that was close!!
So, I have even MORE reason to spend the $$$$$$$$$ for the RRFPR.
So, I have even MORE reason to spend the $$$$$$$$$ for the RRFPR.
10-21-2005, 04:55 PM
#25
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Hi Dave
Yes sorry for the confusion. First part of sentence referred to the car's O2 sensor, second part to the dyno's O2 kit.
But every S4 Gt curve I've seen tends to run well on the rich side ? What's your experience ? You imply that they don't normally run THAT rich...
Yes sorry for the confusion. First part of sentence referred to the car's O2 sensor, second part to the dyno's O2 kit.
But every S4 Gt curve I've seen tends to run well on the rich side ? What's your experience ? You imply that they don't normally run THAT rich...
10-21-2005, 05:06 PM
#26
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Anyone seen an X pipe?????
__________________
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
