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dyno05
05-08-2010, 10:21 PM
Does anyone know if there is a formula for figuring out boost drop in relation to intake charge temperature. I normally see about 11 psi on the cool November days that I normally race and I've never raced on a hot day until Thursday. I was only seeing maybe 8 psi on the top end. Im almost certain it is heat related because I noticed that in the warmer months my truck always gets sluggish on the street after the intercooler heats up. I dont think belt slip is an issue because the boost is rising and not fluctuating.

Duner
05-08-2010, 11:20 PM
Does anyone know if there is a formula for figuring out boost drop in relation to intake charge temperature. I normally see about 11 psi on the cool November days that I normally race and I've never raced on a hot day until Thursday. I was only seeing maybe 8 psi on the top end. Im almost certain it is heat related because I noticed that in the warmer months my truck always gets sluggish on the street after the intercooler heats up. I dont think belt slip is an issue because the boost is rising and not fluctuating.

Yep. Heat hurts everything. That would basically be why us desert dwellers whine and complain about our high DAs. When it's 110° outside our stuff wants to run slow. Hot air take up more room and is less dense than cooler air. You have a tougher time getting it into the blower and the blower has a tougher time getting enough of it to compress into boost.

dyno05
05-08-2010, 11:26 PM
Thanks for the response Duner.

Im really looking for some type of formula to see if the increase in IAT equates to the 3 psi drop. Or maybe I have another issue. My IAT was about 180 Thursday. When I normally race it is probably about 60.

Do you run into this problem also? Or do you have a boost controller where you can raise the boost when the temp climbs? On another note, It was a DA of 1800 feet Thursday, and -1080 in November. Yes that is a negative 1080...lol

White Turbo
05-08-2010, 11:40 PM
Yep. Heat hurts everything. That would basically be why us desert dwellers whine and complain about our high DAs. When it's 110° outside our stuff wants to run slow. Hot air take up more room and is less dense than cooler air. You have a tougher time getting it into the blower and the blower has a tougher time getting enough of it to compress into boost.

Yep... It's not only the ambient temps that hurt, but also air pressure too.
Hot air = less dense.

That's why it's important to try and offset high intake charge temps with a method of intercooling.
The more efficient the intercooler, the less your boost will be affected.
Air to Air I/C's are the least efficient. Meth injection and air to water I/C's are more efficient.
I'm assuming from the drastic rise in IAT, that you run A/A.
I'm running A/W on my set up and don't see much of a boost drop at all on a hot day. My IAT's range from around 74* to a max. of 93* on the hottest day (with ice).
Here's a good read on the subject:

http://www.autospeed.com/cms/A_109789/printArticle.html

dyno05
05-08-2010, 11:44 PM
Thanks, I will read the article.

I run the puny intercooler that came with the Procharger. I knew it was too small. It works awesome when its cold, but terrible when its hot. Im starting to think about meth injection, or an air to water intercooler. I like the idea of the air to water, but Im curious as to how well does it work without ice in it and just water? Would be a pain if I needed to buy an industrial ice machine to keep up with the demand for ice every time I drive it...lol

White Turbo
05-09-2010, 12:04 AM
Thanks, I will read the article.

I run the puny intercooler that came with the Procharger. I knew it was too small. It works awesome when its cold, but terrible when its hot. Im starting to think about meth injection, or an air to water intercooler. I like the idea of the air to water, bIm curious as to how well does it work without ice in it and just water? Would be a pain if I needed to buy an industrial ice machine to keep up with the demand for ice every time I drive it...lol

Yeah that small I/C will not cut it on a hot day, specially with the power you are making.
Meth injection is the cheaper route between the two.

I've really never compared an A/W I/C (with and without ice)as far as IAT's go. I know that my I/C works very well without ice. I just don't have any data to back that claim up.
My A/W set up has what amounts to a tranny cooler/w fan plumbed into it.
So even on a hot day, the water is being cooled somewhat on it's way back to the tank.

I have, however, measured the water temp in the I/C tank with ice. It usually be at or near 34* before the run. And depending on how hot the day is, it feels like about 45- 70* when it comes back around to the tank after a run.
I get my ice from a buddy that owns a store up the street. As much as i can stuff in 2 coolers for $2.

dyno05
05-09-2010, 02:34 AM
I actually have a friend that has an HVAC company and has an ice machine in his garage. Now I have to decide what I want to do next.

stevenz1inoc
05-09-2010, 04:49 AM
My A/W set up has what amounts to a tranny cooler/w fan plumbed into it.
So even on a hot day, the water is being cooled somewhat on it's way back to the tank.


Ever thought about running a small radiator in the bed with a spal fan? I've designed a few in the past for other people but so far nothing for our trucks yet. We use to build all kinds of custom radiators for odd applications at our radiator shops.

dyno05
05-09-2010, 02:47 PM
I did think about that, but that would only bring the water temperature to ambient temperature, so if it is 90 degrees outside then that is as cool as it would get. Thats still a lot better than what I am getting now though. I was actually thinking about mounting a water tank in the bed, and a radiator in the return line under the truck somewhere like White Turbo did, that way it cools the water somewhat before it returns to the ice water.

White Turbo
05-09-2010, 04:36 PM
Ever thought about running a small radiator in the bed with a spal fan? I've designed a few in the past for other people but so far nothing for our trucks yet. We use to build all kinds of custom radiators for odd applications at our radiator shops.

Yes, it's an option to run a small rad. w/fan.

Basically that's what I have now. Except instead of a rad, it's a tranny cooler.
It's easier to mount under the truck on the frame that way. A rad would have to be modified somewhat to connect the hoses.

Personally, I wouldn't want to mount a rad/fan set up in my bed, because I already have a 5 gal water tank and battery in there now. Not much room.
Plus I have to carry tires, tools, ice, jack, etc. in the bed when I go racing.

But if someone wanted to do a rad/fan set up, it certainly would work every bit as well as what I am using.

If I had to do it all over again... I probly would've gone with meth injection.
Cheaper, and easier to install. Just as effective at cooling IAT's from what I hear, (although I don't have any data on that either).

SB440R/T
05-09-2010, 04:45 PM
I will try to get some data one I get the lm2 in.

White Turbo
05-09-2010, 04:46 PM
It would be interesting to do comparisons of Meth versus A/W I/C's, Ice versus no ice, as it relates to IAT's.

Duners set up with the A/C would be interesting to compare as well.

I could do the ice versus no ice comparison with my set up. One of these days I should go out and do that.

I think Ken Walker has meth and A/W IIRC.... Not sure though.

stevenz1inoc
05-09-2010, 06:00 PM
Yes, it's an option to run a small rad. w/fan.

Basically that's what I have now. Except instead of a rad, it's a tranny cooler.
It's easier to mount under the truck on the frame that way. A rad would have to be modified somewhat to connect the hoses.

Personally, I wouldn't want to mount a rad/fan set up in my bed, because I already have a 5 gal water tank and battery in there now. Not much room.
Plus I have to carry tires, tools, ice, jack, etc. in the bed when I go racing.

But if someone wanted to do a rad/fan set up, it certainly would work every bit as well as what I am using.

If I had to do it all over again... I probly would've gone with meth injection.
Cheaper, and easier to install. Just as effective at cooling IAT's from what I hear, (although I don't have any data on that either).

A 5 gallon water tank is BIG! lol The thing is with a small radiator you would onlu need a 2- 2.5 gallong water tank. All in all I think you'd end up with the same space used as now so unless you really need to drop temps more there is no need to change anything or spend more money so I see your point on space for sure!

The adapter to the hose size change should be simple using AN fittings if anyone ever wants to try it.

BluRT00
05-09-2010, 07:39 PM
A 5 gallon water tank is BIG! lol The thing is with a small radiator you would onlu need a 2- 2.5 gallong water tank. All in all I think you'd end up with the same space used as now so unless you really need to drop temps more there is no need to change anything or spend more money so I see your point on space for sure!

The adapter to the hose size change should be simple using AN fittings if anyone ever wants to try it.

Interesting idea!

stevenz1inoc
05-09-2010, 07:50 PM
Interesting idea!

It's just one idea, there are so many options.

Duner
05-09-2010, 08:36 PM
I realize that not everyone tries to race their truck on the surface of the sun (or in similar conditions), but during a "normal" single pass down the track - my truck will turn a 5-gallon tank with water and a full 20 lb bag of ice into 5 gallons of warm water. IAT at the beginning of the run is about 55° and will approach 100° by the traps - on a 10-second pass on a 105°+ day. Granted, that's with the sensor mounted in the intake manifold - so the temp of the intake manifold could influence it some.

I also want to pass on an interesting statement I heard about the difference in cooling ability of air to air vs air to water. Take a piece of metal and heat it with a torch. Hold that piece of hot metal in front of a fan for 5 seconds then touch it with your finger. Once you assess the blister on THAT finger.... heat up the metal with a torch again and then stick the heated end into a bucket of water for 5 seconds, then touch THAT with a not previously damaged finger.

Which method was more effective? LOL

dyno05
05-09-2010, 08:38 PM
"Duners set up with the A/C would be interesting to compare as well."



What did Duner do with his A/C? Wouldnt the A/C compressor have to be running to get any benefit from it? There would be parasitic losses from that, but I guess the gains from chilling the intake charge would still be there.

Duner
05-09-2010, 08:43 PM
[QUOTE=White Turbo;110446]It would be interesting to do comparisons of Meth versus A/W I/C's, Ice versus no ice, as it relates to IAT's.

Duners set up with the A/C would be interesting to compare as well.



What did Duner do with his A/C? Wouldnt the A/C compressor have to be running to get any benefit from it? There would be parasitic losses from that, but I guess the gains from chilling the intake charge would still be there.

I use the AC system to blow cold air thru the heater core to chill the water for the intercooler. Once you have all of the water in the reservoir chilled, you have what you need for a blast at WOT. In my case, that's 5 gallons of 50° water. It's not as cold as the tank full of ice, but for street driving it's as good as it's gonna get. The AC compressor gets turned off at WOT by the PCM anyway - so there isn't any additional parasitic loss at WOT.

mtlcafan79
05-09-2010, 09:03 PM
..and the track loves it when you're dripping a/c water all the way down the lane. hah

Duner
05-09-2010, 10:31 PM
..and the track loves it when you're dripping a/c water all the way down the lane. hah

Two different scenarios.
The AC is street use.
20 lb bags of ice are track use.

The "ricer" guys that spray water on their intercoolers during a pass are hunted down and killed.

dyno05
05-09-2010, 11:30 PM
[QUOTE=dyno05;110502]

I use the AC system to blow cold air thru the heater core to chill the water for the intercooler. Once you have all of the water in the reservoir chilled, you have what you need for a blast at WOT. In my case, that's 5 gallons of 50° water. It's not as cold as the tank full of ice, but for street driving it's as good as it's gonna get. The AC compressor gets turned off at WOT by the PCM anyway - so there isn't any additional parasitic loss at WOT.

Thats a great idea. How did you plumb it? Run the coolant tank to the heater core and back out? I assume you bypassed the coolant from the heatercore because you are in the desert and dont need the heat anyways.

Duner
05-09-2010, 11:42 PM
[QUOTE=Duner;110503]

Thats a great idea. How did you plumb it? Run the coolant tank to the heater core and back out? I assume you bypassed the coolant from the heatercore because you are in the desert and dont need the heat anyways.

Exactly correct. No heat required. Only the intercooler system water goes thru the heater core. The AC chilled air blows thru the heater core if you turn the heat selector to hot (opens the heater door inside duct) before the chilled air blows out of the vents. The only down side to it is that in the summer time - the air isn't "cool" coming out of the vents until the intercooler system is cool also. That could take 15 minutes worth of driving if the priority was to chill the water first. Usually I cool the air in the cab with the heat controls to cool - then slowly chill the water by gradually turning the heat selector to hot. It just depends on what I have "planned". If I know I will need cool water very soon - (as in getting ready to floor it), I will chill the water first.

Reservoir to electric pump
to heater core
to intercooler
out of intercooler then back to reservoir.

White Turbo
05-09-2010, 11:43 PM
A 5 gallon water tank is BIG! lol The thing is with a small radiator you would onlu need a 2- 2.5 gallong water tank. All in all I think you'd end up with the same space used as now so unless you really need to drop temps more there is no need to change anything or spend more money so I see your point on space for sure!

The adapter to the hose size change should be simple using AN fittings if anyone ever wants to try it.

The 5 gal water tank I have measures 13" x 13" x 8"...

5 gals. at 34* will cool twice as long as 2.5 gals. of 34* ice water.

I'm only running a single core I/C, and a 2.5 gal. tank would not be sufficient to keep the IAT down through an entire run, regardless of what method is used to cool the water down on the way back to the tank.
No matter whether you use a rad/fan set up, or a tranny cooler/fan set up, the water will always be hotter when it comes back to the tank, and it can never be cooler than the ambient temp. at that point.

dyno05
05-10-2010, 01:08 AM
[QUOTE=dyno05;110527]

Exactly correct. No heat required. Only the intercooler system water goes thru the heater core. The AC chilled air blows thru the heater core if you turn the heat selector to hot (opens the heater door inside duct) before the chilled air blows out of the vents. The only down side to it is that in the summer time - the air isn't "cool" coming out of the vents until the intercooler system is cool also. That could take 15 minutes worth of driving if the priority was to chill the water first. Usually I cool the air in the cab with the heat controls to cool - then slowly chill the water by gradually turning the heat selector to hot. It just depends on what I have "planned". If I know I will need cool water very soon - (as in getting ready to floor it), I will chill the water first.

Reservoir to electric pump
to heater core
to intercooler
out of intercooler then back to reservoir.

Man thats a great idea. On another note, Im not sure if the PCM monitors IAT at WOT and pulls timing if things get too hot, so Thursday, I mounted a new IAT with a small balloon over the element, into a Crystal Light container filled with ice and wrapped it with header wrap. It told the PCM my IAT was a steady 75. I dont know if it helped, but im sure it didnt hurt either...lol

Five9Dak
05-11-2010, 01:51 AM
First- the density of your local air is inversely proportional to temperature on an absolute scale. (add 460* to local temp in F to get absolute) So you're taking less dense air before compressing it through your pressure ratio. But there is more to the situation than just boost above atmoshperic.

Second-Ideal temperature gain. This is the temperature rise from compression in your supercharger if it was perfectly efficient. Take 1psi of boost above 550F absolute ambiant temp for example....

Temperature gain={[(14.7psi+1psi)/14.7psi]^.28-1}*550=10.2* F gain

Notice that your temperature gain is multipled by your original temperature in absolute units. So the hotter it is, the more charge heating you get.

To correct for thermal efficiency of the supercharger divide this gain by .75 for a centrifugal. (.55 for roots, .70 for twin screw, .75 for turbo)

So take 10.2/.75= 13.6* F gain Things are looking worse aren't they?

Now to find the density ratio take the original temperature in absolute units and divide it by final absolute temperature. In our case use 550* and 563.6*
(460+90)/(460+90+13.6)=550/563.6=.975

Notice the density ratio will decrease with temperature gain (therefore higher ambiant temperature)

Let's put it all together:

Power=original power*pressure ratio*density ratio*volumetric efficiencies ratio*drive power efficiency.

You can take the ones I haven't explained to be held constant for now. Your original engine power is going down with temperature- even NA guys feel this one. Your pressure ratio is staying the same, your density ratio is falling. The the higher the ambiant temperature gets, the quicker the density ratio falls, while your original power is also falling.

Your measured pressured above ambiant (boost) is lower because your PR is applied to a lower local pressure.


For kicks here are a few of the calcs plus a colum for PR*DR*DE, which should be closer to your actual power gain than PR alone. Drive efficiency is taken at .97 in this case.


psi ideal gain *F centri gain *F density ratio PR*DR*DE
1 10.22919648 13.63892864 0.975802011 1.010917607
2 19.99946453 26.66595271 0.953758406 1.051015811
3 29.35712234 39.14282979 0.933559694 1.090359618
4 38.34150296 51.12200394 0.914955694 1.129005532
5 46.98631965 62.6484262 0.897741635 1.167003055
6 55.32070957 73.76094609 0.881748053 1.204395861
7 63.37004304 84.49339071 0.8668333 1.241222731
8 71.15655948 94.87541264 0.852877919 1.277518293
9 78.69987304 104.9331641 0.839780347 1.313313633
10 86.01737884 114.6898385 0.8274536 1.34863679
11 93.12458268 124.1661102 0.815822676 1.383513162
12 100.035371 133.3804946 0.804822503 1.41796585
13 106.7622335 142.3496446 0.794396306 1.452015942
14 113.3164486 151.0885981 0.784494287 1.485682752
15 119.7082386 159.6109848 0.775072556 1.518984032


51% gain at 15psi when you would have hoped for 100%. Now charge cooling helps recover lost density ratio reasonably well, but that's another discussion.

mtlcafan79
05-11-2010, 01:54 AM
Stop confusing them with Science!

sunike32
05-11-2010, 02:09 AM
Stop confusing them with Science!

That was intense!

SB440R/T
05-11-2010, 02:09 AM
Wow, you are an engineer, haha.

PeteRT
05-11-2010, 04:32 AM
don't read that stoned

Duner
05-11-2010, 04:42 AM
51% gain at 15psi when you would have hoped for 100%. Now charge cooling helps recover lost density ratio reasonably well, but that's another discussion.

If you can get that charge cooled to below ambient - then you will get LOTS closer to that 100%. The air you are sucking into the compressor still suffers from the density ratio change - but at least it isn't compounded that much with the cooled charge. I just remember how badly my Vortech slowed down on a hot summer race track outing without any sort of charge cooling at all. It might as well have been NA after you also subtracted the parasitic losses of turning the blower.

Five9Dak
05-11-2010, 07:09 PM
Conclusion- spray lots of nitrous on that shit and only race in the fall.

Oh and don't let RAW see this- I don't want him to get the wrong idea about us rednecks.