So what is rxheven gauge showing? Is the odb2 port just outputting the reading from a random pressure sensor? Where is this sensor?
Yea, I know 100% the S4 has no boost measurement sensor. However, the S4’s manifold had a tap accessible that is perfect for adding a line to measure boost from. It was at the back side of the manifold somewhat near the oil housing. That’s how I measured boost with my JHM kit and used a P3 gauge from a BMW (long before they made one for Audi, I tried for 2yrs to get them to make one for the Audi, I even bought and sent those fuckers an oem vent per there request. I have tons of emails about “2weeks and we’ll have a prototype well send ya”).
Turns out…he doesn’t know. Ironically. 
Maybe he’ll stop arguing now.
Weird, I wasn’t trying to start a pissing match. I was truly curious how this gauge works and I knew that the B6/7 S4 did not have a “boost” sensor.
I definitely don’t know everything and I learn shit everyday, but some people are way to quick to point out how “wrong” someone is based off of website jargon for that product.
RXHeaven, maybe you should inquire how exactly this reading is measured via OBD like we are implying or actually buy the tap that will be more of an “actual” boost reading.
^^ Yep me too. I am really curious as to what is actually being measured.
I wasn’t arguing. I clearly stated my gauge simply plugs into the port and displays a vacuum and boost measurement. Some of you were arguing that I am wrong about what I bought, installed, and can see with my own eyes. Don’t try to turn it around on me Saki.
Originally I assumed the reading comes from a MAP sensor but that clearly seems not to be the case. I have no experience with these Audi ECU’s, its control systems, or for that matter, MAF’s. The only MAF experiences I have are removing them to toss in the trash or sell on e-bay to replace with 3-Bar MAP sensors for aftermarket ECU’s like Microtechs, Haltechs, a Motech and an AEM. I have wired up many cars with ecu’s over the years and understand how systems work, in general… now if I could only learn to tune them.
I have no problem admitting when I am wrong but something else is going on as my gauge does read vacuum and boost up to 2 psi. In my defense, after reading the product description I was sure, and then referencing it here where it seems to have swayed others, that the gauge did not need the boost tap for these platforms. All that said, I did e-mail the the guys at P3 yesterday and they got back to me this morning. Here is the exchange.
ME
Hi,
The B7 S4 is naturally aspirated and now mine has a supercharger on it. Will your gauge read the boost from the ecu as claimed on the page or does it need a separate boost sensor? Does it end up reading boost from the ecu and if so, how does it do so if the car was not equipped with a sensor originally.
P3
David,
For cars that are not factory boosted, you will need the analog boost sensor option.
Thanks!
ME
I ordered your gauge without the analog sensor because according to the product description, I didn’t need to. The gauge is installed and it is reading vacuum and boost by just plugging into the port??? Audi B7 S4.
P3
David,
If it reads, then your tuner is a smart guy! The gauge will read from the factory sensor if it is able.
So, I don’t know what the fuck is going on. I was never informed how much boost my car is running during this break-in procedure, nor did I ask. I only new it was lower and there were other limiting factors within the tune. I have ordered P3’s boost tap this morning and will show video of the gauges reading with and without the boost sensor to see if they are the same.
He’s contradicting himself. He said you need a sensor if it doesn’t come with one and then says it’ll read it from the sensor if it is able to. Huh? Sounds fishy to me
That is fantastic. That will absolutely compare the two, on the same car and either, the numbers will be slightly different because one is not actual boost and uses different sensors and has to use an algorithm or they’ll be identical, in which case, these other sensors and the algorithm used is spot on which will be a huge help to anyone down the road looking into adding a supercharger as this means they’ll be able to use OBD software (such as P3) to read the blocks.
So your research will help people down the road. Great stuff. Looking forward to the results.
[quote]P3
David,
If it reads, then your tuner is a smart guy! The gauge will read from the factory sensor if it is able.
[/quote]
This
David I would suggest getting a proper boost tap. You are reading a signal from the car for boost. It was for my use only in detuning your car. I generally turn it off before the customers get their cars back.
Sorry guys, I should have said something sooner. Maybe make a new thread on just the reading boost via the port or split this one? I’d rather not post in threads that concern other companies, even if part of that thread includes a JHM customer. If we can split the thread that would be great, if not once everyone has seen this I’ll delete it.
Ok, but which sensors is it reading and how accurate is it? By recommending an actual tap, I’m inferring that it’s not all that accurate but still gives a ballpark figure? Would that be accurate?
My brain just done blowed up :o
I didn’t hear anything? Must have been a small explosion. Like one small bubble wrap pop.
clochner or beem can split out the P3 boost gauge discussion maybe?
Perhaps you should clean out the bullshit your head is full of so you can hear better.
This
David I would suggest getting a proper boost tap. You are reading a signal from the car for boost. It was for my use only in detuning your car. I generally turn it off before the customers get their cars back.
Sorry guys, I should have said something sooner. Maybe make a new thread on just the reading boost via the port or split this one? I’d rather not post in threads that concern other companies, even if part of that thread includes a JHM customer. If we can split the thread that would be great, if not once everyone has seen this I’ll delete it.
[/quote]
cool stuff, if I make it out that way in a few weeks it’d be cool to review the math with you
So…back to my original estimation that somehow this thing is reading so high because AMD has attempted to read boost from OBD II port???
no I think that they have said 15 PSI already publicly…and in very cold conditions that could turn into 16 quite easily due to density.
they advertised 13.5 PSI and then were throwing around accusations about all the other kits. That was their tell…why would anyone lie about boost on a kit where the first customer who puts a gauge on will out them? Well, great question. People wouldn’t do that. Normal people anyway. Appears AMD did lol
unlikely, in the picture I posted above the MAF (which would provide airflow information) on the AMD kit is before the supercharger. If they were using this data to estimate pressure it would be reading in vacuum.
additionally, CV has indicated that he added capabilities in his supercharger tune to allow for estimation of manifold pressure to provide a safety to cars during break-in. This is not present from the factory apparently.
that is not to say that the reading is accurate, but I would not suspect this is the issue if inaccurate.
Damn tuning wizard…
Exactly. The big issue turned out to be that nobody was actually wrong but JHM was way smarter than we thought possible. I’d say that’s a good thing.
Gotta love’em!!