Exhaust Back Pressure Vs Turbocharging For Car Nerds
ฝัง
- เผยแพร่เมื่อ 2 มิ.ย. 2024
- The back pressure in the exhaust system is something that’s usually completely ignored, however, it can be a useful input when it comes to analysing turbo sizing and turbo performance. In this webinar, we’ll cover how you can log turbine inlet pressure (TIP) or exhaust manifold pressure (EMAP) data and how it can be incorporated into your tune.
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TIME STAMPS:
0:00 - Introduction
1:16 - Back pressure and forced induction
2:03 - What does the TIP/EMAP data tell us?
4:16 - Data overview
7:36 - EMAP to IMAP ratio
11:53 - Drag racing example
12:36 - Technology is moving the ratio goalposts
13:47 - How do we get this data into our ECU?
21:35 - Using data as a load input
31:39 - Questions
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TRANSCRIPT BEGINNING
It's Andre from High Performance Academy, welcome along to another one of our webinars.
Now today we're going to be talking about a topic which a lot of people completely overlook or don't even give any consideration to and this is our exhaust manifold back pressure.
There's a few ways of shortening that down, eMAP is one of the common ways you'll see that expressed, exhaust manifold absolute pressure.
Turbine inlet pressure or TIP is another way but basically what we're looking at or talking about here is the back pressure that is between the exhaust ports on the cylinder head and the inlet to the turbine housing or turbine wheel on the turbocharger.
So while yes we will have some level of exhaust manifold back pressure on a naturally aspirated engine, generally when we are referring to eMAP or turbine inlet pressure, it is as a result of some analysis that we want to do for a high end turbocharged engine.
So today we're going to talk about why we want to do this, what advantages this gives us and then we're going to talk about some of the intricacies involved in actually getting that data into your ECU or data logger and then how we can interpret or even use it as a load axis or a load input for our ECUs.
So this doesn't necessarily mean that you can't use everything that we're going to be talking about here on a naturally aspirated engine but obviously the sort of back pressure level that we're going to see on a naturally aspirated engine is much much lower so less significant and there's a little bit less to learn.
Particularly it's probably not going to help you on your naturally aspirated engine to learn too much about your turbo sizing which is where it comes in, particularly with our high end turbocharged engines.
As usual, we will have a chance for you to ask any questions so if there's anything that I talk about today that you'd like me to explain in a bit more detail or just anything generally related to this specific topic, please ask those questions in the chat and we'll jump into those at the end of the lesson.
Alright so the first thing is what are we going to be using this data for, what's it actually telling us? Well particularly when it comes to sizing a turbocharger, what we're trying to do is size the turbocharger so that first of all, we have the ability to flow enough inlet air into the engine to support the sort of power levels that we're wanting to get.
Now if you've looked at any compressor maps, they're relatively straightforward, we've got some other webinars which you can look at on turbo performance that will dive in a little bit deeper and explain what the axes in the islands on those compressor maps are so choosing a compressor that's suitable for your particular engine in terms of the capacity of your engine as well as your power aims is not particularly difficult these days and there's some nice tools from the likes of Borgwarner with their Matchbot that will go a long way to helping you with that.
General rule of thumb there is that you're going to need around about 10 pounds of airflow per minute, give or take, for around about 100 horsepower.
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TAGS:
#highperformanceacademy #buildtunedrive #emap #tip #backpressure #exhaust #learndriveoptimise #motorsport #learntotune - ยานยนต์และพาหนะ
A HPA vid a day keeps the blown engine away.
Yaaaay, just what I needed on my day off! HP Academy coming through, as usual.
Enjoy your day off mate! What have you got planned?
Interesting episode !
I gained nearly 100 hp when changing manifolds and Turbos, on the same boost pressure.
The new compressors probably works at higher efficiency, but the largest portion of the gain was undoubtedly the lower back pressure.
And I had to pay with slightly reduced transient response sub 3500 rpm.
And the threshold where boost build up is possible were moved up about 350 rpm.
Change was from Garrett GT1752s to Mitsubishi TD04 18T, on my BMW 635 csi. (3,5 liter I6)
"I don't wanna just sit here and talk for 45 minuties", video duration: 42:58, Yre goood!!! very good!
Link easily handles EMAP. In fact, using a couple Math Blocks - you could set any axis you want to MAP/EMAP*wheelspeed^2 + Pi * Log(fuel pressure).....not that you'd want to....
That's an extra clean set of overalls on Andre...
Might have missed, as this is running in the background, but...but
Depending on the application, it may also be useful to measure the post-turbine pressure, too, so the actual drop across it cn be known, and whether the rest of the exhaust system, if used, is also a factor that needs to be addressed?
The material used for the pressure transducer stand-off is also important, one with a low thermal transfer should be used, eg. a SS, rather than a copper based tube, and thermal sleeving/shielding would be a good idea close to the manifold, to reduce radiant heat absorption. Not something I've tried, but perhaps a heat-sensitive paint, such as used for brake temperature checking, may be an option for monitoring the temperature of the transducer or, at least, estimate if from the temperature gradient from the manifold to the transducer?
For those interested in forced induction, I would strongly recommend Mr Gale Banks' videos, they're primarily on diesel engines, but all the basic points are directly transferrable to spark ignition engines. www.youtube.com/@bankspower
Did u guys get that laptop because it says hp
No, but we should have 😂 - Taz.
LMAO exactly what i thought when i saw HP on the laptop
Hypothetically can you use something like an electronically controlled straight gate running off a table to modulate EMAP while still keeping enough pressure to run the turbine and maintain a boost or torque target? Can this widen the effective range of a turbo or make it feel smoother or more N/A like for circuit style driving or in my case riding? This is what I'm planning on my bike along with a 32mm DBW Bosch anti surge. My thinking was that at high rpm and IMAP I didn't think all that back pressure was required to drive the compressor but rather was a limitation with the wastegates especially poppet style and the control limitations of using springs etc
turbine drive pressure is very important to keep an eye on.
Would you say that one would prefer to have absolutely no mechanical filtering on the emap signal considering you could potentially (I'm guessing) use the than visible exhaust pulses to identify missfires and maybe even inequality between cylinders combustion efficiency? How hard would it be to cross reference the "noisy" emap signal with a crank+cam signal to overlay and identify which exhaust pulse corresponds with which cylinder?
Awesome ❤
Very good info, i need to try it but dont have any extra outputs left on elite 1500
You need an input, not an output. You can get CAN based I/O expanders.
I am looking for a turbo for my 4g64 mitsi with a small port rvr turbo head. Im running it in my l200 and I am after a turbo that will deliver enough mass flow to make 250 hp at 3000 rpm so nothing crazy, i use this wagon to tow my race car. I want as fuel efficient setup as possible in the 2000 to 3000 rpm range. My goal is to have the map at least the same, or higher than the emap. I am not hugly concerned about turbo lag. Does emap have any influence on the brake specific fuel consumption? Is this even possible to achieve on small engine like this? I would imagine a setup like this would drive similar to a commercial truck where it takes a second or so to build boost.
Is there a relationship between manifold temperature and manifold backpressure ?
Absolutely. Guy Lussac’s law and then the ideal gas law. Basically, if volume is constant, relationship between pressure and heat are directly proportional. I’d dig in a bit more to Boyles Law, Charles Law, Guy Lussac, and Ideal gas law for more theoretical knowledge if you’re interested. Cheers.
Just got my car back up and running again. My question is are the calculations just as simple as EMAP/ Map (boost pressure) or is it EMAP/(MAP+14.7)?
Good practice would be to use absolute for both. MAP and "boost" are two different things, measured differently.
@@gordowg1wg145 That's how I did it and it make the most sense on the levels and power I recorded.
@@gordowg1wg145 I measured 42psi emap and 23psi boost pressure. 1.11 Drive pressure ratio. Right on the money. I go some more I can go. Twin turbo V6 so have two EMAP sensors.
Team,
Regarding the installation of sensor, what effect does temperature removal have on the EMAP. Presumably based on combined gas law, a decrease in temperature correlated with a decrease in pressure, ie, as measured vs MAP, there will be an error? Whilst in kpa as a unit, 5 percent or there abouts may not be a large error, it’s still a factor.
Also,
Regarding tuning, can you infill some information as to tuning against EMAP with respect to when the turbine housing/wheel becomes saturated….ie based on load, you can delay peak load later to keep map/EMAP in check to reach ‘power goals at high rpm’ (trade off being dogshit drive down low)?
Great episode as always!
Ta
One thing you completely forgot is that there's practically zero gas flow to the EMAP sensor. It's not that the coiled line would cool the exhaust gas, rather than it simply acts as a buffer between the sensor and the hot flowing exhaust. The gas in the line still would act as a spring, so yes, there's an increase in error, but it's not as significant as you think.
What’s inside those exhaust pressure sensor dampers? Curious how they work
Most of the ones I’ve seen are just steel wool
Adaptronic does not exist anymore ?
After it got bought out by Haltech, they took Andy’s IP and used in the Haltech and then Haltech was sold to a USA company and I guess they decided Adaptronic was redundant.
Diesel guys have been calling it drive pressure for years. How much energy it takes to drive the turbine wheel.
Very much on point - while using exhaust energy to drive the turbine "seems" like free energy to the ignorant, there is a definite cost to, at least partially, drive the turbine against the impellor loading.
Can we make a petition to stop calling referring to it as exhaust back pressure and call it turbine drive pressure (turbo) or exhaust restriction pressure (NA or post exhaust housing). It makes no sense to me because we dont refer to positive intake manifold pressures as intake back pressure.
In a way, it's better to call positive manifold pressures as intake back pressure, as that's what's actually happening in the engine. There's a common misconception that boost pressure equates to CFM, which quickly gets annoying when people compares two completely different engines by their target boost pressures, or equates boost pressures directly to power output.
No, the industry standard term is TIP. EMAP, and others, are internet terms.