WHP Vs Temp

[psychbiker1966]

Does anyone have a formula or an educated estimate on the effect of ambient Temps on WHP? I have a fully built GSX that is running on 93 pump currently. I had it on a Mustang Dyno in Jan after my rebuild and it put out 377 awhp/ 361 TQ at only 20.5 lbs boost with an FP Green. its a (2.4 bottom end with a 6 bolt head btw). Now I know this Dyno in Houston is a heartbreaker and reads notoriously low numbers. (EVO X read 220 awhp stock on the same dyno). Plus the temp was 75 degrees that day. My car feels very quick now on cold days like 40 degrees but when temps get up to 75 plus it is significantly slower. My boost on cold days hit 22 lbs which my Tuner says is fine as we are running speed density and have a conservative tune. (Till we go over to E-85). So my question is how much more power am I pushing on cold days? It honestly feels like from 75 down to 35 degrees I get around 40hp with the extra boost and denser cold air. Almost like 1 deg =1whp. Does anybody actually have real numbers or experience that they could offer?
Thanks.

 

[ErikTande]

10 degrees cooler (intake temp) will gain you about 1% horse power. So yes, the difference between 70 and 30 degrees is significant, you would definitely feel it.

Source:

Assuming the pressure stays the same...
Correction factor (Cf)
Temperute in Celsius(Tc)

Cf=1.18((Tc+273/298)^0.5)-0.18

So at 25 degrees C, the CF is 1 (STP or around room temp)
http://wahiduddin.net/calc/cf.htm


http://forums.corvetteforum.com/1545285908-post12.html

 

[psychbiker1966]

I can buy that for a NA car but..I am positive the effect will be MUCH more power increase /decrease for a TURBO or Forced Induction car. With the addition of increased boost AND cold dense air I bet we see close to 1 whp per 1 Degree F.
So between 85 and 35 degrees we might see up to 50 hp better or worse. With our motors pulling timing due to heat soak or knock.

 

[Benjyc32]

You also have to think about many more things than just temp.. you have to think about altitude, humidity.. there are many math formulas out there that I unfortunatley don't know how to work them. best bet is to dino it twice, once when its warm and once when it's cold.. but every day is different.

 

[ExtremeTurboSystems]

A good read if you want to put some science behind it.

 

[boost97gst]

You are most likely correct about the 40hp gain. Especially since you are on pump gas. Heat is a killer, even more so with pump. I have no dyno numbers but i can definitely say there is a very big difference in power when its 90* vs 40*.

 

[LandSpeed-DSM]

It is going to be very much setup specific.

 

[psychbiker1966]

Thanks ExtremeTurboSystems for that confirmation link on what my butt Dyno was noticing!

 

[LandSpeed-DSM]

We should also consider that with this much of a change in air density, you may well have to tune the higher load cells to take advantage and yield an actual gain.

Unless you have persistent knock retard, you otherwise won't necessarily see an increase in power.. it's more that the atmospheric conditions have provided the potential to run a more aggressive spark/fuel scheme as well as potentially increase boost (if your particular turbo has the room to grow) and your fuel is stable enough to handle these changes.

 

[Benjyc32]

I really want to see the outcome of this, any dino days coming up soon for comparison?

 

[boost97gst]

I think if you're running a large frame turbo you wont notice such a huge increase in power. Or if you're already running e85, you wont notice a massive jump. On pump gas though? With a small or mid sized turbo? Go try it. See for yourself.

The thing to remember, like the article ETS posted: No matter HOW good your IC is, it can not drop the charge temp below ambient. Simple as that. That should wrap it all up right there.

 

[LandSpeed-DSM]

I think if you're running a large frame turbo you wont notice such a huge increase in power. Or if you're already running e85, you wont notice a massive jump. On pump gas though? With a small or mid sized turbo? Go try it. See for yourself.

The thing to remember, like the article ETS posted: No matter HOW good your IC is, it can not drop the charge temp below ambient. Simple as that. That should wrap it all up right there.

Well, if you are starting with a large, efficient turbo and IC to begin with.. you'll still make more power at the same boost level than the same setup on a smaller turbo and the same IC with the temperature change if neither setup is fuel limited.

You may just pick up a greater proportion with the smaller inefficient setup. For example on something like a 14B with a massive temperature change, going from say 12.5whp/psi boost to 14whp/psi boost. Which would be about ~12% gain. This about jives with the numbers on my last 14B setup when it was really cold on late night tuning sessions.

Where on something like my 67mm turbo that would be akin going from 24whp/psi boost (actual) to almost 27whp/psi. Which at my current boost level would be picking up >75whp, which seems more than a little unrealistic from just ambient temp.

 

[nismoz]

Op your close by your guess, from my experience. The na side of your engine is prob adding 35-40hp at that drop,on the boost side a little more. Someone mentioned altitudes,from sea level to say 6000ft a retune would yield significant gains because air thins and moisture increases most of the time.
That being said i argue that the air charge cant be dropped below outside temp cause the ic splits the air coming through it. I have seen 40* temps and an ic frost on the cold side of the ic i assume because of the splitting affect plus relative humidity.
Can anyone chime in on this theory?

 

[psychbiker1966]

I have Dynolicious. Maybe i need to compare data on a hot vs cold day on a secluded "TEST" track!! This weekend its going up to 75. Next week the lows will be in the 40 Deg range.

 

[Benjyc32]

I have Dynolicious. Maybe i need to compare data on a hot vs cold day on a secluded "TEST" track!! This weekend its going up to 75. Next week the lows will be in the 40 Deg range.

Do it! ^^

 

[boost97gst]

Op your close by your guess, from my experience. The na side of your engine is prob adding 35-40hp at that drop,on the boost side a little more. Someone mentioned altitudes,from sea level to say 6000ft a retune would yield significant gains because air thins and moisture increases most of the time.
That being said i argue that the air charge cant be dropped below outside temp cause the ic splits the air coming through it. I have seen 40* temps and an ic frost on the cold side of the ic i assume because of the splitting affect plus relative humidity.
Can anyone chime in on this theory?

If you are spraying/wetting down the IC then it MIGHT be possible to drop below ambient temp. It would certainly pull heat off the IC faster. I still think the water you would use has to be colder than ambient as well though. They actually spray the shit out of ICs at some dynos.

 

[spin1r6]

I dont have any formulas to give and i see people are a bit split about picking up power or how much. i used to race snowmobiles and motocross and as a competitive racer it is very common to rejet the carbs every 10 degrees difference in temp so 40 degrees would certainly yield a noticeable power difference, and boost would amplify the difference over an NA engine. Bottom line is colder air is denser, more air means more power given your tune can compensate for the added fuel required.

 

[LandSpeed-DSM]

I dont have any formulas to give and i see people are a bit split about picking up power or how much. i used to race snowmobiles and motocross and as a competitive racer it is very common to rejet the carbs every 10 degrees difference in temp so 40 degrees would certainly yield a noticeable power difference, and boost would amplify the difference over an NA engine. Bottom line is colder air is denser, more air means more power given your tune can compensate for the added fuel required.

That last bit is what makes or breaks this. At WOT you will be in Open Loop running off your VE/Fueling/Timing tables. If this pushes you into cells that are not tuned it could just as easily hurt performance.

Better atmospheric conditions simply amount to increased potential.

 

[boost97gst]

^^^^Very true. If you're in a new cell thats not right, you could spike lean. No Bueno

 

[gofer]

Just this weekend I noticed a difference in my ECMLink HP/TQ estimates between two passes I made at the track, the only difference was the 12* intake temps. The tune was unchanged but my HP/TQ estimates dropped from ~480/430 to 440/390 with just a 12* IAT change.

Same lane at the track, same tune, just hotter IAT's. The car had been in the pits for 3 hours between passes too so the IC wasn't heat soaked.

 

[psychbiker1966]

So I captured 2 runs on two different days. On the Hot day 80 Degrees I made 386 WHP. The cold day 38 degrees I made 433 WHP. That's 43 degrees and 47 whp!!
I rest my case

 

[nismoz]

Exactlly this^^^

An it will never change
Cooler air =more power
Test the theory of air being split by an object(in this case,two ways.through the ic an across it.) and see doesnt it cool faster because of the spliting effect.
Molecules are molecules and we cant change science.

 

[LandSpeed-DSM]

You two have clearly out-science'd yourselves this time.

We desperately need to work on straightening out our education system.

Look at gofer's results, ~40hp gain per Link estimate from 12* IAT change. You saw 47whp from 43* temp differential on your even less reliable iPhone application. Do you really think this is some empirical study to hang your hat on?

There is no control here, and it's certainly not "rested." No one was questioning the potential to make more power from colder air at roughly the same ambient pressure. This is a well known function of density used in everything from finding efficient flight paths to tuning in almost every form of motorsport.

This is not only an established item, but purely obvious on paper as well.

That wasn't the question.

What is up for discussion, is how much power a given setup can gain. It's not going to be linear gains/losses either, something convenient you could just extrapolate out.

If you think you are gaining a literal full 1whp/degree (F) on a turbo as small as the FPGreen and only 2.0L displacement and anything other than a stratospheric redline.. amounting to more than 10% of your actual dyno run from a 40* temp change, I have a bridge to sell you.

 

[psychbiker1966]

LandSpeed.

I agree that there can't possibly be a formula that would work for every setup and tuning method regardless of temp/humidity/altitude, but this is my 3rd DSM and every one of them gained buttloads (BUttHP=Temp+/- 1Deg x Boost Sq) more power in cold dense/ dry air vs Houstons power sapping heat soaking Humid Hot summer days. From my big 16g to my 20G and now my FP green,(On my current car which is a 2.4 with FP4R cams and a Buschur stage 3 1G head,etc etc, )my boost has gone up 4-5 PSI on cold days as well so I am sure I am gaining 40 - 50 AWHP going from 20.5 to 25-26 PSI on a FPgreen on 93 pump, without knocking, at or before 6500-6750 RPM.

Your results may vary!

I don't need a bridge!