Isn’t FI without cooling kinda worthless?
I mean, I know there will be gains, but without cooling the air charge you will never get the true potential of the system.
If I’m spending $10k to get a supercharger, I’m certainly not going to “skimp” on another $2-3K worth of cooling… That would be like buying the best supercharger kit out there and then having your 8 year old sister write your tune. (yes I’m exaggerating)
if the blower is well sized and the motor makes use of its air well N/A then no cooling isnt a huge concern. The blower is mostly just making up for the air the motor cant vacuum in on its own. The issue comes from undersized, inefficient compressors blowing into a motor that can’t handle the extra air.
But don’t you want a more dense air charge so that you can increase your fuel and gain even more power?
you do, and you will with the more expensive setups. Both amd and jhm are offering a version of their kits with modest power levels and with various cooling options as well as fuelling options. I think it’s a great idea, because both of them are using good sized superchargers that will be very efficient (sleeping almost) at the power levels they’re being tuned for in the base kit
For example, the JHM B6/7 S4 tuned cars run high 12s @ 107-110 MPH…and when you add a supercharger to them, they tend to pick up 5-10 tenths and 5-8 MPH over already e fficient and fast cars…using no intercooler/heat exchanger.
re: your point about ‘if I’m paying XXX I am not going to skimp on XXX’
what if it was $8250 vs. $12,500? i.e. maybe once you start pushing the car into levels that require cooling, you also start requiring other modifications (maybe fuel related etc.) that were otherwise not required on the base kit?
What if you could also just upgrade at a later date if you felt the need?
air mass is what matters for power; the cooling allows for the motor to handle more air mass (cylinder pressure)… pressure and velocity are fluid with flowing gases but are both related to the ultimate cylinder pressure when the valves close, the density that matters is that of the air charge in the cylinder when the valves close
Yes, I can understand that thinking.
For me, I would not add any kind of forced induction without charge cooling and wouldn’t purchase a system if it wasn’t offered. But that is just me.
When you look at a motor top roots app. You should always cool it. So going cheaper on a motor top blower is a waste as the blower might be more efficient but the heat absorption negates all that out plus creates a new issue that requires you to cool the unit. . Having a relocated blower (JHM) or even a unit more free standing (TTS) not absorbing the motor heat the efficiency of the unit on its own isn’t getting off set by heat absorption.
Air under pressure has a relatively predictable pattern if you know enough of the other factors in the equation.
so if you have a roots style that is intake mounted and a C-fuge unit relocated not close to a heat source. Both units can be running at say 70% efficiency and due to the absence of heat the C-fuge unit will be unit that fairs better.
While there are many many factors that need to come into play. The C-fuge units are… Or should I say have been known to be much better at running without a intercooler due to there efficiency and over all design. So in short the point I’m looking to make is there is a threshold on when you would require a cooling unit or additive to any FI system. Putting a IC on a car in some cases is doing more harm then good. If the unit is efficient enough and the system is with in its needed limits there is no gain.
So you agree? Isn’t that saying you want a more dense air charge since density is mass per unit volume?
What I am saying is a high pressure/high temperature air charge is not going to be as dense (not as much mass) as a high pressure/low temperature charge, which means you can’t combust as much fuel.
Also, a cooler air charge will help reduce the heat added throughout the entire engine overall which will help with efficiency and extend service life.
At least those would be my reasons to want the cooling and be willing to spend more to get it. ;D
Ok. So you are saying that these centrifugal units are efficient enough that they don’t add a significant amount of heat to the air charge despite the pressure change? Is this because we are only dealing with a few psi of boost?
good point on the heat transfer to the blower… and with a positive displacement pump the pockets of air are going to have fairly small cross sections and should have lots of contact with the impellers… lots of heat transfer
a high temperature/pressure air flow will be flowing faster though (especially without the pressure drop from going through an intercooler), the mass flow rate of air through a cross section per time will be the same… think of what dictates the flow of air into the engine, how much air the blower is pumping. Assuming constant volumetric efficiency of the blower, mass air flow becomes dependent on impeller speed (engine speed and pulley ratio). Regardless of the cooling the same air is entering the system, once at steady state you cant accumulate anything so that air has to move out (through the cylinder). In fact the hot/high pressure charge will have more energy which results in a higher stagnation pressure when it gets trapped in the cylinder. The problem is the heat causes issues with pinging, if that effect didn’t limit things, thermodynamics tells us the motor would actually make more power with a hotter intake charge (work is directly related to dT)
Ill be honest. It would take a very long explanation to cover all the points that back this up. Let me say this.
Yes but this is dependent on several things. On Average C-fuge units run much more efficient and massively more efficiently Per RPM over 5000rpm. So I laugh every time someone makes a roots style kit for a car that revs to 8000. There is a threshold of boost to heat ratio on a C-fuge you can keep adding boost as long as you keep reducing the pressure. Say for example you can port the intake and drop the pressure. You can keep yourself in a good window and continue to make more power. (this is obviously within limits) ______next point.
When you hit a threshold of say 8lbs.___________ now lets know the 8lbs on a Rs4 with a C-fuge and 8lbs of boost on the APR or PES kit is going to be different as the intakes are the first point of restriction. Then you start to do the math on win loss per cooling Per hp per boost. While its obvious other companys don’t do this. Its how we do this in the OEM sector and there are many units that SVT has made that don’t use a cooling component.
This is nothing more then food for thought. I can’t say I know all the dynamics on every unit or every situation. Many of these are rules of thumb meant to help answer your question
Deleted. Thanks for the insight!
I was speaking about heat engines in general, not an internal combustion engine. Greater heat differential inlet to outlet does more work. I mentioned that because it shows the necessity of cooling. IF (big IF) you didnt have pinging, the higher your inlet heat and energy the more work done everything else the same, you dont waste energy on heating the intake charge after combustion if its already preheated.
On the flow rate, consider the amount of time the valve is open. A dense slow moving charge can pack in the same amount of air as a sparse fast moving charge, hence why I mentioned flowrate through a cross section being the same. If mass flux is the same and the valve is open the same amount of time, you have the same air mass. When the air stagnates in the cylinder all of the velocity is converted to static pressure (total pressure=stagnation pressure= static pressure + dynamic pressure).
Thanks for explaining more. Luckily you guys are around to remind me how much I of my engineering knowledge I have forgotten. haha
I had this whole post written up above and even posted it, and then it hit me what you were saying and I realized I was completely wrong which is why I deleted it. Not only did I miss your point, but I was using engineering chem instead of thermo in my thought process. In case you guys saw the post, thanks for being kind and not lighting me up on it.
Back to searching for my thermo books, and saving for a sub-zero cooled supercharger. hahaha :
Again, keep in mind: Nobody is saying that you don’t need cooling on a supercharger application.
What they are saying is that the space these units are operating in with the entry level kit (stock fuel pumps etc.) the level of boost they’re running before the fuelling system is out of capacity (i.e. the $$$ items that distinguish base kit from the next stage) is not enough to require cooling to deliver good results. You can however always opt for cooling by stepping up to the next level.
Have a look at this video…you can see the JHM car which was being tested with pulls and dyno rips. They installed before/after temp gauages to get a feel for air temps. There wasn’t a massive change that needed cooling, again because of how the unit was being utilised. Push it a bit more and certainly , it would become a concern. On the B6/7 S4 though that cfuge JHM kit is barely working since the engine’s cast internals can’t handle much more power anyway (our RS4 is a different story, forged internals from the factory). The stage II and III JHM S4 kits will involve heat exchange for sure as they’ll be built motors making big power.
Cheapest way to supercharge an rs4 with over 7 psi is to add a thicker head gasket . And the timing chain allow for such a gasket that compression drops to 10:1 which the 2 l tfsi uses and can get 350 hp (per bank).
This is all calculus from 2 years ago but it’s pretty close .
Picture of the AMD SC posted on QW…apparently being installed in SoCal area as the first “production” unit:
Needs smaller driven pulley ;D
I don’t get why it is a production unit that is being installed, and they say stuff like this…
" They should have it up and running in about a month if everything goes right"
???