DanaT

Car and me were 3305lbs on the scale at the track.

I was trying to tune and run.

Trap speed was 110mph. To put that in perspective, a ZR1 vette did 115mph. I have to look at the videos I took to see what other cars were doing. I did remember an STi running 97mph. A turbo 240SX with a big FMIC ran 95ish right next to me.

The supercharged vettes (after market..built) were 110 to 120mph

DanaT

19 above 14.7 (reference voltage for the MAP) That 19.9 is nothing. There is nothing being logged on that channel. That requires a Zeitronix boost sensor which I dont have. I am reading the Vitesse MAP sensor on user 2. You need to look at user input 2 that is just a voltage. Then I reference to the lookup chart to that MAP voltage (I got stupid and didn't put the correction table into the zeitronix when I bought a new laptop..it will make the output in psi)

95ONE

But, you said that your 19.9 psi was already calculated in using sea level atmospheric as a base pressure, therefore, it would be exactly the same pressure as someone seeing 19.9 psi on their gauge who is at or close to sea level.

ergo. Boost would not need to be lowered 2.5psi to match yours.

95ONE

So then you had absolutely no boost gauge? just voltage to estimate boost? That explains the negative sign in front of the boost number. I just read your post below. You had a map sensor that read 33.7psia. GOT IT>> 19PSI it is. NOT 19.9

DanaT

This just confused me. There is the gauge vs absolute boost.

I had 19+14.7 (the MAP reference) = 33.7psia

However, for me to get 33.7, my boost gauge (not the logged MAP but the typical boost gauge someone installs) references to my atmosphere. This means my boost gauge will show 19+ (14.7-12) = 19+2.7 = 21.7

If you are sea level (or lets say "standard atmospheric conditions) you can compare (ballpark..ignoring the losses talked about above) my 21.7psi of boost with your 19psi of boost. Basically think I need 3 psi more boost to make similar power.

DanaT

No, i have a boost gauge, but I really don't watch it. The MAP sensor is much more accurate, and I can log it.


-Dana

DanaT

Correct, with the exception that that 19.9 psi is not a valid number. The MAP voltage (user input 2 is a valid number). I was about 19psi (3.60V = 19psi, 3.70V = 20 psi) above 14.7psi.

When talking about pressures, reference point is very important. A MAP sensor references against a vacuum so it never changes.

DanaT

I have a stock intercooler and pipes.

But even if I improve the cooling efficiency, if I move it down to sea level I still get 20% more air mass flowing over it so no matter what I do the same air-air intercooler between high and low altitude is more efficient at low altitude.

What happens if that I can tune for high altitude, but it is a compromise. IF you do the same things at sea level you typically see bigger results.

DanaT

To get to part of the meat of the subject, what works well on a dyno doesnt always work well on the street. What works well on the street doesn't always work well on the strip. What works on a road course is different than what works on the strip.

Dynos don;t get wheel spinning with big boost spikes (i tried tuning those out tonight with varying degrees of success)

DanaT

Regardless of what anyone thinks about high altitude, my uncorrected number was 355rwhp on an eddy current dyno. Those typically read somewhat lower than a dynojet.

This is why I like uncorrected numbers. IF you want to outrun my 951 in acceleration, as this altitude I don't care how you make the power, you will need to be able to have more than 3305/355 = 9.31 lb/hp uncorrected at this altitude. Races are not won by correction factors. How you do it (turbo, nitrous, NA, blower) doesn't matter, that would be the target that is needed.

95ONE

Here is a quote I followed earlier in the thread.




You kept saying "19psi above 14.7psi." last 3 parts of the sentence above. That would mean you have the same absolute pressure as I do in Houston if my boost gauge referenced straight from my atmosphere.

The same would hold for Patrick if he lives at sea level. Therefore, no boost adjustment would be needed to keep things equal.


Very well said. End of story.

Not exactly true. Diminishing returns the closer you get to Ambient no matter what altitude. An intercooler better and more more efficient than anything in the world and bigger than your car will never get you less than outside temps. Therefore, a very strong one that is 95% efficient at altitude (and actually fits in your car) will still net you a after intercooler temp within say 10 degrees of one running around in Houston with the same outside / ambient temps. That 10 degrees isn't doing much. It all certainly adds up though, which is clearly why altitude cars, even if boosted, still lose horsepower. It's just not nearly as much as so many correction factors I've seen floating around .

Well, that works out fairly well. Using this online calculator and inputting 3305lbs at 355whp gives you an estimate trap speed of 111. CLICK HERE That is fantastically close to what actually happened. Well done.

LOL DANAT slow down

Did you have fun? Did you get to meet Sid? I'm truly jealous.



.

DanaT

Yes. I have 19psi above 14.7. That means you can mostly compare my 19psi to a sea level 19psi (again with the caveat that I have different pressure ratios, intercooler cooling, etc).

Gauge psi (on a boost gauge) would have been about 3 psi higher (not many people can read 0.3psi on a boost gauge).

The MAF values are referenced to 14.7psi (0 psi boost = 1.52V on the MAP) but is REALLY 14.7psi absolute. (actually they are referenced to vacuum = 0 but use the transfer function below and you can calculate absolute)

Here is MAP voltage vs ABSOLUTE pressure



Notice that the first dot is 14.7psi (1.52V). But the MAP can read below that.

As an example with the car off and the MAP powered at Bandimere tonight, I logged 1.23V or 12.001psi absolute atmospheric condition.

DanaT

Racing is always fun (as long as stuff doesn't break). Sid lives about 6.3 minutes from me...

There were 5 rennlisters there....

95ONE

DanaT, It is sincerely amazing and dizzying to no end how two people can say the same thing in so many different ways. It is this reason that debates can get so frustrating because half the time they are arguing the same point and don't even know it Agreed with all of the post above. (oops, post #42, you posted again before I hit enter. )


The 951 Rennlist is STRONG in Colorado. Sounds like you guys had a fun night none the less. Believe it or not, I don't talk like this in person!

DANAT.... You, Sid, and whoever else can dyno their cars with uncorrected numbers need to get your butts down here and Dyno. I will pay one nights hotel for all of you and 3 dyno runs each. I kid you not. I think this will shut ALL of us up, because there will be nothing but smiles and good times to be had by all. And most likely Dyno numbers that will be split right down the middle of all our estimates. Even if not, and I'm completely wrong, It will have been worth it to see everyone and hear all the stories and see all the faces and cars... besides, I'm cheating a little. I didn't say you wouldn't have to share a room, and that I know the Dyno owner personally, and probably won't have to pay much for the time. >

333pg333

Ok, so let me get this straight. You have a Stage 2 turbo, 80lb injs, stock i/c, 2.5" exhaust and that's kinda it. You run 355whp @ 19 or 20psi at 5000' on a hot day?

I have GT3076 .82, bigger cam, fmic rated to 600hp, bigger hard pipes, 3.5" dpipe into larger exhaust, Motec M400, full sequential cdi, 1000cc injs, 3x044s running race E85 at approx 500' and display this chart with a 24psi peak leveling down to 23psi. Oh and this is with a brand new wastegate.

I am not bashing anyone here, but I just don't get it. The guys tuning my car are not shade tree mechanics either. Here's my ign map also. May I deduce that if we brought your car to my dyno at a significantly lower altitude and ran 23psi that you'd be up near 450whp. What am I missing??