All I changed on the diagram was delta T heat transfer efficiency, and I guessed the percentage.

Like you, I'm just trying to show everyone that there is more too it.

Unlike you, I feel that the difference on a low boost setup like most here run, is negligible.
I was using heat transfer efficiency with increased delta t as my main reason for this opinion (outside of dyno results).

Dann

http://https://www.miataturbo.net/pi...269695&thumb=1Update: The filter did not survive track usage... it "vibrated off" on the third test session and I ran over it! Damn, I just wasted $110. It seemed scetchy to me that there was no rolled flange to capture the filter base.https://www.miataturbo.net/members/s...t-filter-4077/

The next revision will likely involve moving the oil catch can and routing as large of pipe as possible alongside the intercooler and mounting a "securely mounted" filter accessing the side of my radiator inlet shrouding.

It has been interesting reviewing the math. Thx! http://https://www.miataturbo.net/me...ilter-4077.jpghttps://www.miataturbo.net/members/s...0105-4078t.jpg

I didnt take physics in HS, I took it it college, and my extent on heat transfer was dropping ice into coffee and measuring the temps vs. time.

how about this caveat: assume the IC is working at full efficiency throughout the rpms--and that's 90% regardless.

because there's still a lot more to it than that: Front Mount Intercooler Efficency Test Data

No you can't assume that, not even close with 90* differences thats a 20% odd difference

Dann

you can assume anything you want.

108°F to 102.6°F is a 5% difference in my favor.

still outside of the entire point of this thread.

Its not a 5% difference because 100f is around 550f absolute.

Get your head around some of the basic principals, please.

Assuming a constant intercooler efficiency is the only way to tackle this problem. Intercooler efficiency should not change with a change in inlet temperature so it should not change from 90% to 93% in your example. The ambient vs ambient temperature in the denominator corrects for variations in inlet temp.

To me, this is the best way to tackle this problem.


If the density ratio calcs are correct from the earlier picture, it takes into consideration the F to Rankin conversion. So 1.38 to 1.34 is a 2.9% density gain due to the CAI. If you were making 200 whp with the hot air intake the CAI will give you 5.8 HP (200*1.029) more ,in theory.


....


As far is pre turbo inlet pipe and any losses there, I think the main thing you can do is have a short and smooth transition to the inducer inlet. Smooth bends and gentle transitions in diameter. If you turbo inlet is say 2.5 inch, make sure all cross sectional areas up stream are at least 2.5 in.

102.6F = 562.2R
108F = 567.67R
90F = 549.67R

that's less than a 20% difference between any of those...

You are really lost, you dont know which way is up right now.

Im done.

This whole thread is kinda a mess...

Let's just leave it at colder air is better than hotter. Everyone can agree on that. How much better is debatable.

/thread.

Ok...

Up is relative. up to you might literally be down for me.

Probably helps to clarify, just a thought. Because the difference is 38%.

100% Agreed. We can sit here and argue about thermodynamics and heat transfer all day long. Arguing about this between engineers is dumb enough, but trying to teach someone thermodynamics and heat transfer while trying to prove a stubborn person wrong at the same time is damn near impossible.

Pretty much everyone in this thread has posted incorrect information about thermodynamics and heat transfer. Makes sense, not everyone here is formally educated in these subjects.

Rather than getting in a pissing match, why don't you guys grab a beer or something? Find a noob to rip a new one...anything is more productive than this thread.

18psi's post #5 sums things up effectively. Without data, everything else is just a shot in the dark anyways.

Patrick: Your math completely checks out. What your missing is what Scott is trying to tell you. Your boost control setup equalizes out the large differences you are speaking of. If your wastegate is referenced after the intercooler, and your intercooler isn't undersized, your motor doesn't give a shit what happened at the compressor outlet. It just has air at your target boost, at a temperature not much higher than ambient. With P and T, your equation of state for the air is basically fixed, and your power level will be slightly less than the CAI, but decently close.

The biggest assumption here is the post-intercooler wastegate reference. If your reference is between the compressor outlet and intercooler, you will see much larger power drops when not running a CAI.

I can tell you, without a doubt, that a CAI turbo car will reach target boost at a lower RPM than a non-CAI car, with all else being equal. Before that wastegate opens, the CAI car has the advantage for sure. How much earlier will you see target boost? I have no idea. My guess would be a few hundred RPM.

Dann: You need to chill out, there is no need to be so damn insulting. Scott has the big picture here, even if some details aren't spot on, but he admitted that, so I see no reason to act like this. Yes, you understand heat exchanger efficiency a little better. But then you linked some page that just talks about conduction. An intercooler's predominant heat transfer comes from convection, then from radiation, and absolutely last comes conduction.

This is not high school level physics we are talking about. What's funny is that when you say the low boost setups will not benefit a ton from a CAI, you and Scott are basically agreeing.

Leafy: Props given for stating that you need to go to metric units for thermodynamic or fluid dynamics problems. While technically equivalent, metric seems to be less confusing for some reason. If you are dealing with Temperature in the Rankine scale, you have already lost the battle. This is a personal opinion, but I have broken many test curves because I always convert these type of problems to metric first.

Ive been a lot nicer to him while hes being wrong and arrogant here than he was to me when he was wrong and arrogant in the last pissing match.
;)

Dann

"But he hit me first" LOL

And I don't even have kids...

made my point.

Dann

I have not missed what Scott said. I am well aware of how this stuff works. ;) Just pointed out his error and kindly explained why a CAI is important and not trivial. Apparently the word trivial has different meanings or nobody understands what I write.

Here's a funny things I'll just point out. You guys can read it and just think about it. I'm not going to explain the same thing 20 times and be told I'm wrong when I'm not.

Like you said dustin, a CAI will make the turbo spool faster. Why?

Answer: For the reasons I have explained. When the turbo is "spooling" it doesn't' have enough HP from the turbine yet. So if it's spooling faster with a CAI, that's because the compressor is more efficient. Notice I never said a word about intercooler?

Also regarding data, yes, it's needed to be exact. I said that in my first post! But math (real math, with all the variables accounted for, not just some) is still correct, and you can work some examples and see how changing one things affects a temp or pressure, etc.

To be fair to Dann, I have been an ass to him. But I did politely bow out and admit I was wrong in our TQ discussion. I was thinking about total load, but not distinguishing between compressive and tensile, which was a mistake.


I don't doubt this at all. I've suggested the same. But I believe it's going to look more like this between the two plots:

https://www.miataturbo.net/attachmen...1&d=1426589681

The turbo will have to spin faster and at a higher PR to provide the same amount of oxygen after IC. So it might spool up a tiny bit slower, plus the extra time it takes to reach boost threshold, but ultimately it's still in the same heat efficiency.

FWIW, using the math formula on the compressor map, we can correct the airflow for temperature. This makes me assume (sorry Dan) that the heat efficiency island does not change, but the flow rates around it do.

for example on the above compressor map:

it's been measured at at 85°F inlet temps and 13.949psi. So for my 90° day, lets just call that one close enough.

but we can correct the airflow for the 180°F inlet temps.

So say we need 15 lb/min then:

corrected flow = required airflow x (new temp/545R)^0.5 / (new / old pressure)

corrected flow = 15 x (640/545)^0.5 / 1

corrected flow = 16.5 lb/min

which looks more like this:

https://www.miataturbo.net/attachmen...1&d=1426590555

yes, like you said, there will be greater airflow requirements, but I still don't believe it's anywhere near where you're suggesting. There will be less area under curve, for sure, and less peak numbers, but I thinking if you plotted the two conditions on a dyno the difference wouldn't be that extreme. Which would be the better of the two? cold air, hands down, without a doubt.

But this thread was to discuss if a CAI is necessary and I honestly wanted to discuss that. I absolutely willing to concede if I find I'm wrong, but I'm still unable to at this point.

I agree with all of that.

Dann

:friday:

So, the take away answer from my original question is: If I can't get air from a cold source, then at least have an appropriately sized, and properly ducted high efficiency intercooler to deal with the heating issues. Expect to be down on power due to heatsoak issues at the end of your rungroup session, especially on hot days.

And expect to have more coolant temp issues because the average air temp of the air going across your radiator will be higher. Assuming you're normal and your IC is in front of your radiator.

Thats what I would take away from this. Also, like Leafy mentioned, this extra heat generated is not ideal. You are adding heat in multiple locations in the engine bay.

If I were you, I would want to find a way to get some cold air, but if it's simply not possible without a lot of expensive routing changes, then don't freak out about it. Keep an eye on all temps, this will likely put larger thermal loads on just about everything.

If you can't CAI, make sure your boost control reference is post-IC!
Trust me, I know exactly what you are saying. Without a CAI, you are just making a bunch of entropy, and destroying a ton of exergy. I agree a CAI is not trivial, but it's not huge either. I wouldn't be surprised to see 5+HP increase from adding a CAI to a 220HP car. Expect more if you can safely add timing because the intake charge is a bit cooler. In my opinion, 5 HP in a Miata isn't trivial, but it's not the end of the world either.

Let me try to explain what I mean when I say the difference won't be huge. Assume a non-CAI car and a CAI car are both on side-by-side dynos. Also assume that the non-CAI car owner isn't a complete failure at life and referenced their boost controller after the IC. This is very important. Before the WG opens on both cars, the CAI car will spank the non-CAI car. After both cars are operating at an RPM where the WG is open, the differences will be less apparent. This extra compressor work requirement you are mentioning manifests itself as hotter, less dense air. We both know that. But for a car with an effectively sized IC, then this will just be a larger pressure drop in the IC. If you are speaking of a car that has a boost controller referenced pre-IC, then the power differences will be larger because the extra pressure drop from the IC will not be accounted for. But a post-IC boost control reference will mostly make up for this extra pressure drop, that is the advantage of a post IC boost reference.

Also, if you are speaking of a car with an IC that is optimally sized for an ideal system with a CAI, then the IC would not be able to extract enough heat in the non-CAI system, and what your saying would be true in that case as well. I personally think that more people run an oversized IC than an undersized one, so this isn't super applicable here.

I know that your not mentioning the IC, but the IC and boost control system will very much be masking this effect on a car thats referenced after the IC. Just another reason not to be a fialure and reference your boost controller right after the compressor.

Like Brain mentioned, you'll just be operating on a different path on the turbine map. Not as efficient.

If I were to build a turbo car, I would absolutely run a CAI. People go through a lot of trouble and spend a lot of money to get better spool, it would be stupid to throw some of it away by feeding the compressor hot air.

I realize that this post is entirely too long.

For turbo intake length, is shorter better and does having a intake diameter bigger than let's say my 2" t25 inlet make a difference?

Intake at least 2x capacity of engine works well in most cases.

Dann

Sorry my brain no understand

Calculate the capacity of the intake between the filter and the turbo, if its smaller than double the engines capacity, make it longer or rounder until it is.

Dann

So the diameter of the pipe does not affect performance? So in an ideal world with the same capacity, a t25 with a 2" inlet will flow the same as with a 2" or 3" pipe?

Come on...

I haven't any idea how and to what degree tube diameter and length plays a roll in turbo intake performance.

Ive made STUPID power on GT2560's using 2" intake tubes fed by a 3" filter with a venturi moulded into its inside and a 3>2" low angle reducer. But with 2 feet of 2" pipe and >300whp..

I've never seen any measureable difference on the dyno with or without an intake tube on 4 differents miatas/setups.

one being an old BEGi Aerodyne setup that had an airbox that uses the stock air filter and litterally a slit for an air source:

https://www.miataturbo.net/attachmen...ine=1426855433

There is .5 or better percent in power there.. How many times does one need to make a 1% improvement to have a real barn burner?

The intake losses are proportional to velocity (diameter) squared, the length to the first power, the section change from filter to tube and the element losses.

Put a vac gauge in the inlet as close to the compressor as possible. Every inch of vac loss is about 3%.

Measure a stock MSM sometime for a real shocker. Why would they do that?

corky

This thread is like a merry-go-round.

http://www.motorsportreg.com/index.c...9#.VQyNXuFMDT8

Hey Corky; have you got a better solution for the air intake on my MSM set-up? Would your MSM CAI box work in combination with the MSM BEIG kit I purchased from you?

I'm leaving tonight for the first Or region SCCA race of the season, running in SPM. So far my rungroup consists of a porsche gt3, a viper, a couple of bimmers and a camaro... I'll be pedaling as fast as I can... so any help with extra power will be appreciated!

Thx for all of your MSM upgrades, they have kept me racing reliably now for many years. craig

Every inch added to a turbo intake is a 3% loss in what? Flow? How does that translate into actual hp? These maths are way over my head.:facepalm:

Damn son. I dont know where to begin.

Inches of Mercury is a measurement of pressure. In this case a pressure that is lower relative to atmospheric pressure. We call this vacuum. Restriction causes a pressure drop, creating vacuum, which can be measured in inches of Hg using a gauge or MAP sensor.

I think it is reasonable to assume that the intake tube on the inlet of the compressor is isolated from the rest of the system from the effects of resonance, so the length of the tube probably does not matter in that sense. It only matters in that a longer tube may create more restriction. In the same way the volume or diameter of the tube does not matter. All that matters is the flow.

Obviously cold air has some benefit, thats why you see drag cars with turbo inlet in the bumper of the car. Cold, high pressure air going into the turbo is better than hot air in the bay. But does colder air make up for having the turbo breathe through a couple feet of pipe, the way it would have to on a Miata? Thats what this debate really comes down to.

Hey thanks man :D

One question,

how does pressure drop affect performance for a turbo intake? It's not the case that 3% drop = 3% less power is it?

@hiano,

measure the diameter of the inlet of your turbo. Your intake pipe should be equal to or greater than that diameter. It should as short and straight as possible (use logic here, longer and more bends = more pressure drop). Cold air source is better than hot air.

That's all the info you need to know. Forget the math stuff if you don't understand it. Just don't choke your turbo before the compressor inlet.