Blown06

iTrader: (32)

I've got a question, or rather observation that has me scratching my head a bit. This is going to apply to the guys especially with A2A set ups, but I do want to make a comment about the LJMS/417 Motorsports A2W that fits on the Holley High rise.

Before I get into my own personal data, I'd like to point out a few observations of others peoples struggles with the issues that get plastered here on the forums.

First, most of the guys with A2A setups will see some significant rise in a 1/4 pass, which can be expected. I've seen anywhere from 20 to 100+ degree temp rises depending on boost and core.

Second, the A2W guys that run real (not knock off) Precision Brand units and the like can keep temps way down. On my race truck pushing 26 psi with the F2, my IAT's where the same at the starting line as they were at the finish line. For example, my best pass to date, my IAT's on the starting line were 91* and 91* at the finish line on a 154 mph pass. In the middle of the run, temps dropped to around 70* and then came back up. I considered this a very efficient set up. Even the cheaper knock off Chiseled units can still see very good results with good pumps, high capacity tanks and big lines.

Third, for those who have paid attention to the debacle and ultimate failure of the 417 Motorsports unit, temps get out of control on even short street hits.

Where am I going with this.

Correct me if I'm wrong, but most consider this heat as a byproduct of compressing air. It is not black magic. Compressing air heats the air, that is no secret. Turbo cars probably have it worse as the turbine side is blazing hot and only a few inches away not helping the situation.

Now here is where my mind shuts down. Lets take my 2012 Dodge Cummins. It has the stock A2A up front and I run a stock turbo. Only mods to the truck are full deletes, 5" turbo back exhaust and an H&S Minimax tuner. This is my daily drive and tow truck. I keep the tuner turned all the way up, all the time even when I tow. The truck makes 36 psi boost almost instantly (not a lot in the diesel world, but thats a good number in the gasoline world). Because we are in the middle of summer heat, I have been paying attention to trans temps and IAT temps lately and I'm baffled about what I'm seeing.

Basically, I can be driving the truck on around the city and on the highway for hours at a time so everything is really good and heat soaked. Driving my truck down the highway at a normal pace, IAT's are always about 16-18 degrees above ambient. They will be typically 25-30 degrees above ambient in stop and go traffic. After everything is heat soaked real good. I can make a 0-100 mph pull at 36 psi and the IAT's will barely budge. Typically less than 3-5 degrees to the end of the pull (which probably takes 14 - 15 seconds), and then will return to normal within a couple minutes after the pull.

So, if the assumption above that most IAT heat comes from compressed air, how the hell am I not seeing an IAT increase that is even remotely close to someone with an A2W 417 unit or very large A2A unit on a car that is pulling less than 20 lbs. of boost?

The A2A on my truck is large with a big surface area, but we are talking about cars with bigger units on less boost and some even with ice water A2W units that are fighting a battle that doesn't even remotely resemble anything my truck faces.

Aside from the basic physics that compressing air creates heat, what am I missing that my stock A2A set up on a factory truck out performs just about every aftermarket A2A unit on the market and especially the 417 unit?

I'll probably post this up on some other forums too to see what others say, cause I just don't get it.

smokeshow

iTrader: (16)

That's a complex question to answer - aren't they all - but I'd say it basically boils down to three things. One...the stock intercooler on a Cummins truck is pretty massive. A diesel needs the turbo to do what the engine is rated to do, so the IC needs to be able to handle full tilt turbo heat production at steady state. You could be over 20psi for hours on end in one of those trucks, so the intercooler needs to be large enough to get rid of that heat. Second, and related to that, is compressor sizing. Cummins doesn't just slap an oversized or undersized turbo on the engine and hope for the best, as anyone could guess. It is carefully sized to minimize heat delivered to the intake air via poor compressor efficiency. This mitigates temperature rise in boost. Third and probably most important is the amount of power the Cummins is making. It's much lower than any turbo v8 gas engine. Power is an energy rate and an increase in temperature is a result of an accumulation of heat energy. At lower power levels, there is less heat produced per unit time from the compressor and thus less heat available to increase air temperature. At high power levels that race cars and trucks run combined with less than perfectly sized compressors and undersized intercooler capacity, there is plenty of opportunity for air temperature rise.

To put it into perspective, the big frac pump trucks I used to work with at Halliburton had quad T6 turbo 12 cylinder diesel engines rated at a max of 2000hp. The intercooler for these was remote mounted away from the radiator with a dedicated PTO shaft driven fan and a core thickness of no less than 12 inches with a surface area in excess of 40 sq ft. It sounds massive by our standards for 'only' 2000 horsepower, but realistically, that's what you need.

01ssreda4

iTrader: (87)

^^^yep, all that is on point.

TrickTurbo

iTrader: (12)

I'm
Gonna say. The stock truck ic is huge and designed for maximum surface area.

Not familiar with debacle you speak of.

But all the water/air I know in Fords. Air temps can be close to 200+. Add a good ic drops to 140 or less.

Blown06

iTrader: (32)

I can agree with the size of the intercooler and the comment above about the entire system being engineered to do exactly what it does. Last year I spent probably 350 days at home and only 15 or so days working. This year is finally blessing me with some income so in the last month or so, I've driven across Texas (East to West and back) probably 5 times I've been so busy. Having an A-pillar mounted H&S Minimax in my face for that many miles and you start looking at different parameters logging away.

Also, I believe it was Smokeshow that made a comment above about running extended periods in boost and it was something I didn't really bring into the conversation. Once I was out in West Texas my cruise control would be set anywhere from 85-95 mph sometimes for an hour or two at a time. I wasn't really thinking about it then, but on flat ground the truck cruises at 8-10 lbs of boost. Doing that for an hour with IAT's never getting more than 16-18* above ambient is pretty cool. Then there are the big hills (small mountains) out there where it would easily pull 25-30 lbs of boost to clear the top. Still with maybe on 1-2* in temp rise.

Anyway, I agree with all you guys are saying above and was wondering if there was anything we could take away from all of it. Blasting 36 lbs. of boost for extended periods of time with very little change in IAT's is a cool thing (no pun intended) when you consider the amount of threads on the internet of people bitching about rising iat's in cars that go WOT for less than 10 seconds at a time.

smokeshow

iTrader: (16)

I think the only takeaway would be to run the largest and most efficient intercooler you can get away with. For air to water setups, a larger reservoir is beneficial in drag racing because there is more water to heat up which helps hold temperatures lower during short periods of boost. Its a wash for long periods of boost though because it just comes down again to how fast the heat exchanger can reject the heat. Properly sizing the compressor is also something that shouldn't be overlooked.

Vortec350ss

iTrader: (20)

The other issue is RPM. A diesel is moving half the RPM most gas motors are... on an equivalently sized engine that means air is literally moving through the intercooler at half the speed and spending twice the time in the intercooler.

A 6.7 liter engine moves a very specific volume of air (obviously outside of doing mods that change its VE ie heads and cam etc) per RPM. Just because you're at 36PSI does not mean the volume is increasing, it means the mass is increasing. You're moving more CFM of ambient air, but not moving more volume of compressed air. The compressed air still hangs out in the intercooler for a long time

Here's a crude example, a 6.0 diesel at 30 psi and 3k will have air dwelling twice as long in an intercooler as a 6.0 gas engine at 15psi and 6k rpm even if CFM is exactly the same. They both may make 600 horsepower, but the intercooler has twice the time on the diesel to cool as it does on the gas engine.

MikeGyver

iTrader: (5)

Your example is only a repeat of what you said earlier in the post, so I feel compelled to present an analogy.
Maybe it will be easier for people to envision what you are saying if we make 15 psi air and 30 psi air two different things. If both engines are making the same power, they will need the same air mass to do it. So let's represent 30 psi as unpopped popcorn, and 15 psi air as popped corn.
The engines will require the same mass of corn in a given time, but the popcorn has so much less mass per volume, it will have to be put into the engine much faster than the kernels, so that the engines get the same mass at the same time. If the popcorn flows through the intercooler at the same speed that the kernels flow, the popcorn engine would make much less power. -In memory of Professor Irwin Corey

Vortec350ss

iTrader: (20)

Yes I did.

Sometimes I find people need to hear the same thing said multiple different ways to understand it.

smokeshow

iTrader: (16)

Lol @ the popcorn analogy. Reminds me of the time someone dropped a can's worth of orville redenbacher's kernels into the exhaust stack on my buddy's old Cummins truck. Fired his truck up and as soon as he started cruising down the road and EGTs went up, clouds of popcorn came billowing out of his exhaust.