Competition Corrected or Uncorrected H.P. Numbers?

[J.Davy]

When you guys are listing your h. p. #'s are they corrected using the standard correction factor for non turbo engines or is there another method for theses engines?

 

[Jim Fulmer]

Most numbers are corrected that people post (most numbers) it's aactually better to always find out what the correction factor is.



My experience is that in the higher altitudes you will always loose raw power, like at M/M (2000 ft) I lost 30 uncorrected hp over Dallas Tx. (500 ft) the two events were 2 weeks apart and I did not make one change.



Jim

 

[J.Davy]

The problem is you can,t use that correction factor for a turbo charged engine at least not as far as i can see. In a different thread Moolie had wrote in that he dynoed in at 492 h. p and 951 tq which corrected to 592h. p. 1143tq. as he lives in Colorado at 5000' elevation. So being that at Sea level the air is 14. 7 psi and at 5000' you are sitting at 12. 2 psi all you have to do is add 2. 5 pounds boost and you are back to dynoing at sea level. The observed number is the only one that counts,because you can simpley add more boost to compensate. As for between to events loosing H. P. Was everything done on the Exact same dyno?Same batch of fuel? Same operator?Lots of variables between two events. Maybe this does not make sense,but that is the way I look at it. Please correct me if I am wrong.

 

[DavidTD]

I'll add some observations from the various places I have had my dyno.



I've seen a largest correction of 1. 06 in the mountains of West Virginia. Most other places are well below that.



SAE correction I feel makes good use for equalizing air quality, even for diesels, except for elevation. I think it's not entirely accurate for forced induction engines at elevation but that doesn't mean you shouldn't use SAE at elevation. If you are at 5000 feet always when tuning, that constant will remain and the variances will be temp, humidity which will be corrected. This is important when comparing between an August run and a December run.



Just like Gas engines, the heat and humidity have big impact on HP. But I can see first hand on my dyno how trucks will be consistant corrected throughout the year, but uncorrected hp follow the season's air qualities.



And yes, things like Fuel filters (seen 20hp) can rob power and other factors can too. Do I believe 15 - 20 % correction factors are valid? No, at least not in the majority of cases anyway.



In dyno competitions, SAE can be used. That way those that run in cooler morning or evening air don't have an advantage over the midday and afternoon hotter air. But that is really just my opinion.



And to answer your original question of which number do most use? The bigger one. :-laf

 

[J.Davy]

Basically thats what I was getting at,there should be a little bit of correction for humidity, and cold air is going to have a big effect on the intercooler and therefore have a effect on h. p. but the sae correction equalizing everything back to 60 f and 29. 92 ' of mercury should not apply to a engine that can make up for it by simply adding the missing air. Stoichiometric is Stoichiometric ,you add enough air to burn the fuel you have. It does not make any difference how you do it. The end result is the same H. P.

 

[J.Davy]

I thought some of you dyno guys might have some more input?Or does this seem right?

 

[jetenginedoctor]

Basically thats what I was getting at,there should be a little bit of correction for humidity, and cold air is going to have a big effect on the intercooler and therefore have a effect on h. p. but the sae correction equalizing everything back to 60 f and 29. 92 ' of mercury should not apply to a engine that can make up for it by simply adding the missing air. Stoichiometric is Stoichiometric ,you add enough air to burn the fuel you have. It does not make any difference how you do it. The end result is the same H. P.

Evidently your theory does not hold true, or Jim wouldn't have tested less at the higher elevation as he mentioned.



I'll have your answer tomorrow and we can settle this question once and for all.

 

[J.Davy]

I stated the possible reasons fore Jim's results ,read all of it not justs the parts that benifit you. How come you are waiting till tommorow,if you are really as smart as you say you are then why don,t you know this stuff off the top of your head?If you do get the correction factor for a turbocharged diesel like you say and post it you will have confirmed everything we have been debating so far. The correction factor for turbocharged diesels is not the same as the S. A. E. correction factor for naturally aspirated four stroke engines.