This is precisely why I never dyno my car I just race people who've dynoed. If I'm faster or slower, then I know roughly where I am.

 

And in the end, you have no idea how your car really runs, because you rely solely on what the dyno tells you, and in corrected form, neither of which are a good idea. If it's really THAT important for you to know what the dyno calculates as your estimated before/after based on some random correction factor, then STD/SAE are for you. For me, though, I'm only concerned about what my car ACTUALLY DOES and not what some incorrectly formulated correction factor tells me. That really follows the saying "oblivion is bliss." (no, not ignorance)

 

^ no you dont, racing brings in so many other variables it's an even worse way of judging power.......

To the original poster of this thread, see what you started lol.......... And yes HP numbers matter to me, otherwise I would be driving something that looks nice and gets 50 mpg.

Scorke

 

Trap speeds don't lie.

 

What if the driver shifts into fourth instead of second?

I am sorry but if you are compairing setup to setup there is nothing better than two cars on the same dyno.

Scorke

 

HP numbers are important but so is track times and for some of us, real-life comparisons. I street race very often and I usually know who I race (and how much power they put down and also track times). Ive also been to the track and the dyno. I think my numbers I put down correlate very well with the outcome of all of my races. I was disappoined with my 116.xx trap speed on 93pump but Ill take it since it was 70* degrees out and I was dynoed at 55ish. I think I can hit 117 with maybe some more tries as I only have 4 actual track runs.

BTW my dyno numbers both before and after were at the same dyno facility, same temperature and uncorrected. I could careless about STD, SAE numbers.

 

You are a drag racer and the drag strip is your dyno. I do not like drag racing so I have to rely on a dyno. That is my only way to tell if my car made power from the mod that was done to it.

Let us say you DO NOT have access to a drag strip and you have access to a dyno and you have two sets of cams at the same price and you have no idea about their specs. You can test one set of cams this week and the other one the next month same day of the week. How would you make up your mind which set to buy? Are you going to use corrected or uncorrected numbers?

More to the point:

I looked at the conditions of my first dyno run and dyn run number 24 on the same day the same dyno:

------1st run-------run 24
press 29.1---------29.2
temp 77.1----------88.2
hum 10%----------8%

The first run had the Xede zeroed out. Run 24 fully tuned. Could you please tell me how I can tell how much power my car gained from the Xede tune w/o using corrected numbers? Please tell me

 

except in the many cases where the drivers don't shift as fast as god, or let the clutch out to quickly and bog, or over rev the engine and get locked out of a gear, or get tire slip off launch, or it is 30 degrees outside, or it is 126 degrees outside, or your clutch was slipping, or you are at high altitude, boost leak, bad tune, bad gas, etc etc etc...

there is a reason manufacturers don't give you 1/4 mile specs as the standard over BHP. one they can do in a controlled environment, repeatable, free of human error. the other depends on just about every aspect of the car functioning in a repeatable mannor, PLUS the driver being as consistant as a machine, which i know even you are not like.

 

I do not drag race. What other options do I have?

 

We haven't even listed the biggest advantage to using a dyno,

YOU DONT DESTROY YOUR CAR.

Destroy to me= substantial avoidable wear and tear.

Scorke

 

There is no issue at all citing uncoorected dyno numbers IF you are not comapring your before and after dyno sheets. However, if you want to know how much power your car made before and after modification, then you need to cite corrected numbers.

My first dyno run was on March 24, 2006 @ 12:43 PM. Run number 24 on the same day and same dyno was @ 2:01 pm. during that time barmoetric pressure went up 0.1, temp went up 11.1 degrees and humidity went dwon by 2%.

Given the above atmospheric changes, I have no other option but to use corrected numbers to find out how much hp I gain from the tune.

 

Cool but I think comparing my before and after dyno sheets is OK to do. If anything my 2nd dyno had the disadvantage since it was higher humidity. The temp was exactly the same (55*). I am unsure of the pressure however I do not think that is a huge factor. Not saying its not a factor, but definitely not a major one. Also, since it was at the same facility, I say that helps equal it out too. I did 4 mods to my 2nd dyno and gained substantial power in both butt and actual dyno and not to mention street comparisons.

 

NJ, come on man you just keep repeating the same thing. I've told you 2-3 times now that even with those corrections, the numbers aren't right. You take them as gospel without knowing the corrections are not accurate for the weather differences. It's all just a big ballpark comparison.

You also don't have to be a drag racer to go to the drag strip. It's a tool just like the dyno except that it gives you real world results instead of dyno results in one-gear while stationary with no road conditions. How hard is it to just go and get some runs to see how the car performs in 4 gears in a real environment while moving? Just relying on the dyno, especially corrected numbers, leaves you in the dark.

Scorke, unless you go see what you can trap, you'll never know how well your car is really running no matter what the dyno says.

 

You have not answered my questions. Let me repeat them:

1. How do I know the before and after hp gains from my xede tune given the change in atmospheric conditions cited above on the same day on the same dyno and my total aversion to drag racing.

2. How do you know which set of cams to buy; set A or set B under the following conditions: 1. You have no access to a drag strip 2. you have a dyno but your dyno runs with each set of cams are a month apart.

I DO NOT drag race. I do not like it and I WILL NOT like it. I have not done it ONCE in ANY of my cars. Infact in all of my life I have only been to the drag strip ONCE. It is not for me. I am a road racer and I need a dyno to tune my car. That is the only tool that I have.

 

1) The difference in atmospherics you listed would provide negligible differences in power. Uncorrected and corrected would both give you ballpark gains. As I've said multiple times, you can always look at both set of numbers!

2) You can use the false correction to look at peak numbers or just look at the total area under the curve regardless of the correction to make a more educated decision.

3) Who cares if you like it? I'm not asking you to like it - I'm saying you should use it as a tool, else you're cheating yourself. I never road raced, autocrossed, or rallycrossed until last year after 7 years of drag racing. I still tried them all, and as a result, I am now pursuing road racing more vigorously than I ever did with drag racing. I don't expect you to like drag racing, but it's a very useful tool that will give you far more data than a dyno. Using both in combination is the ultimate measure...

I am a road racer, but I certainly don't need a dyno to tune my car unless it's inclement weather when I get tuned. Not sure why you need one.