MPG optimised header ideas

[kafer65]

Haven't they used thermal imaging to see hot spots developed from the harmonics to choose where to put the crosspipes? That might help confirm if you're on to a good setup.

[gone-ot]

Maybe "trombone" exhaust header pipes, using sliding joints? At least for prototype testing?

Earlier postings:

• http://ecomodder.com/forum/showthrea...tml#post210603

• http://ecomodder.com/forum/showthrea...tml#post279467

• http://ecomodder.com/forum/showthrea...tml#post155270

• http://ecomodder.com/forum/showthrea...tml#post160892

• http://ecomodder.com/forum/showthrea...tml#post161499

[ever_green]

I switched from a 4-2-1 catted equal length header to 4-2-1 unequal shorter headers and my mileage actually increased. This might be because i could run hella lot more timing at lower RPMs than before. Im talking about 6-10* of further timing advance. I'm not sure why, but i used to get much more bottom end knock with equal lengths.

Stock EL headers Catted:
Opening dimension: 1.378" ID
Primaries on the cat side are 25", 21" & 20" on driver side
1.772" ID collector
20" collector to first cat

New UEL Headers Catless
Opening dimension: 1.56" ID
Cross pipe length: 17"
Driver side collector length: 7"
Passenger collector to uppipe length: 13.5"
Header to uppipe opening: 1.75"

My cruising mileage was much improved at lower RPMs however at higher RPMs it seemed that for some reason my car liked to run richer. Even in closed loop the ratios were always a tad richer than target. about 0.2:1 AFR richer. this was nothing crazy but it did affect fuel economy. note the new headers have much higher flow rate and lack a catalyst converter.

[Madact]

Originally Posted by Old Tele man

Maybe "trombone" exhaust header pipes, using sliding joints? At least for prototype testing?

Well, I've been thinking about layout and I have one setup in mind where it would be feasible change the secondary lengths by about 6" without too much trouble, just using clamps...

Thanks for the links, should make some good 'light' reading tonight

Originally Posted by ever_green

I switched from a 4-2-1 catted equal length header to 4-2-1 unequal shorter headers and my mileage actually increased. This might be because i could run hella lot more timing at lower RPMs than before. Im talking about 6-10* of further timing advance. I'm not sure why, but i used to get much more bottom end knock with equal lengths.

That's exactly what I'd expect from the reading I've done, if the EL header was reasonably well tuned for high RPM - the reflected pulses would arrive at precisely the wrong time at lower RPMS, pushing gas back into the cylinder instead of sucking it out, which would explain both lack of torque and extra knock (as per the autozine article on the Mazda SkyActiv manifold linked earlier):



Conversely if there's a bit of valve overlap and new header is scavenging less at high RPM, the ECU could be expecting a slightly larger larger air charge, and adding the right amount of fuel for the expected intake mass... though I'd expect closed loop control to correct that? It would depend on how closed 'closed loop' is, there may be saturation values in there which keep either internal or control parameters within predefined ranges - this is a common control systems 'hack' to stop a closed loop system from going unstable if some physical parameters change in an unexpected way ... depends on whether the person programming the ECS paid attention when they covered finding poles of a z-transform, and how much they expect the - and how much they trust the physical parameters of the system to not change. Of course, I'm no expert in ECS specifically, so I don't know whether that applies in this case.

When people talk about installing headers for performance, it's often mentioned that ECU tuning is required to get the best out of it... but I'm not sure if that's because they take it out of the closed loop parameter envelope, or

[ever_green]

Originally Posted by Madact

Well, I've been thinking about layout and I have one setup in mind where it would be feasible change the secondary lengths by about 6" without too much trouble, just using clamps...

Thanks for the links, should make some good 'light' reading tonight



That's exactly what I'd expect from the reading I've done, if the EL header was reasonably well tuned for high RPM - the reflected pulses would arrive at precisely the wrong time at lower RPMS, pushing gas back into the cylinder instead of sucking it out, which would explain both lack of torque and extra knock (as per the autozine article on the Mazda SkyActiv manifold linked earlier):



Conversely if there's a bit of valve overlap and new header is scavenging less at high RPM, the ECU could be expecting a slightly larger larger air charge, and adding the right amount of fuel for the expected intake mass... though I'd expect closed loop control to correct that? It would depend on how closed 'closed loop' is, there may be saturation values in there which keep either internal or control parameters within predefined ranges - this is a common control systems 'hack' to stop a closed loop system from going unstable if some physical parameters change in an unexpected way ... depends on whether the person programming the ECS paid attention when they covered finding poles of a z-transform, and how much they expect the - and how much they trust the physical parameters of the system to not change. Of course, I'm no expert in ECS specifically, so I don't know whether that applies in this case.

When people talk about installing headers for performance, it's often mentioned that ECU tuning is required to get the best out of it... but I'm not sure if that's because they take it out of the closed loop parameter envelope, or

Yeah I consistently self tune my ECU . the header did not give me much trouble with exception of slightly richer AFR under load or high rpm. Most of this was fixed with MAF and o2 sensor rescaling. However under closed loop it is still too rich off the target and for some reason the ECU does not seem to compensate for it. I'm just not sure why. When I target 14.5 its actually at 14.3-14.4.

UEL Headers let me improve BOTH performance and economy by running richer with more timing until MBT is achieved. This was done using dyno. Under 2800 rpm which is pretty reasonable for city driving the engine does not go any richer than 14.0:1 (under heavy load) and timing is about 10* higher wthan before hich is very significant. Stock it was 14.5:1 with 10* retard. You might argue that richer AFR demolishes BSFC. Yes it does but the slight sacrifice in BSFC is made up for by shorter acceleration times and more power from extra timing. The acceleration with UEL headers is very linear and controllable. The drivebywire has been tuned to keep the throttle nearly wide open at low rpms and we have the TCU short shift. This way an inexperienced driver can accelerate nearly at best efficiency while keeping up with traffic yet never exceeding 2000 rpm. This I found was not possible with EL headers. The engine would shudder and sometimes detonate and it just was too slow. It just felt like lugging and now it feels smooth and 'torquey'. My peak torque also moved lower slightly from 4600 rpm to 4100 rpm and peak power was raised to 5800 from 5600. There is a secondary peak torque from this resonance yoy were mentioning at 2200 rpm but its not substantial like the one with EL headers (that was at 2800 rpm). Its a very flat curve now from 1800-5200 rpm vs 2800-5200 rpm as before with lots of dips and peaks. I'm surprised how much difference in the curve was made just by changing exhaust manifolds.

You know hotter headers flow better and shorter uel manifolds have a tendency to run hot.

[Daox]

If your header is creating more low end torque, wouldn't it make sense that it also creates more knock? Higher charge density = more knock, right?

Higher charge density at the same ignition timing should always mean better efficiency (assuming everything else is constant). However, if your engine must retard timing for a higher charge density, then you can obviously lower efficiency. It sounds like this is what is happening to you ever_green.

[adam728]

Originally Posted by Daox

If your header is creating more low end torque, wouldn't it make sense that it also creates more knock? Higher charge density = more knock, right?

Higher charge density at the same ignition timing should always mean better efficiency (assuming everything else is constant). However, if your engine must retard timing for a higher charge density, then you can obviously lower efficiency. It sounds like this is what is happening to you ever_green.

If the new header lessened reversion and therefor the amount of (hot) residual exhaust gases in the cylinder the more power could be made as well as reducing the chances of detonation.

[Nigel_S]

Originally Posted by Madact

When people talk about installing headers for performance, it's often mentioned that ECU tuning is required to get the best out of it... but I'm not sure if that's because they take it out of the closed loop parameter envelope, or

That is because most engines don't run closed loop at full throttle, they use open loop and guess the amount of fuel to inject based on the throttle position sensor and either a manifold pressure sensor or air flow sensor.

A good manifold will create a higher vacuum in the cylinder which will pull the fuel/air mixture into the cylinder faster thus using more air/fuel mixture at any given throttle position so the throttle position sensor will be telling the ECU to put too little fuel in. A MAP sensor will show lower pressure in the manifold which the ECU will interpret as the throttle being closed more than it is thus requiring even less fuel. An air flow sensor should tell the correct story, but being slow to respond to changes the ECU will also look at the throttle position sensor which is telling the wrong story - You do need to change the mapping of the sensors for open loop running. Closed loop should be correct although any change in throttle position may cause temporary inaccuracy until the effect has been measured and corrected. Turning the fuel pressure up a touch should sort it unless the ECU has a fuel pressure sensor.

[ever_green]

Originally Posted by Daox

If your header is creating more low end torque, wouldn't it make sense that it also creates more knock? Higher charge density = more knock, right?

Higher charge density at the same ignition timing should always mean better efficiency (assuming everything else is constant). However, if your engine must retard timing for a higher charge density, then you can obviously lower efficiency. It sounds like this is what is happening to you ever_green.

any non-detonating engine would make more power than a detonating one. plus sometimes its good to reduce VE a little to run more timing. hot rodders sometimes run less compression pistons to run more timing. there is a balance.

i did still get knock in closed loop at lower rpms...like 1600. this was addressed with slightly more closed loop fueling. it was not as horrid as stock where 10* of retard was needed.

[Madact]

Thanks Nigel_S, ever_green.

Unfortunately I don't have a lot of tuning options available to me - the ECUs supplied with Australian 6th gen Civics are either too primitive to update maps on, or just too small a market for tuning companies to make chips / add-on modules for. Whichever it is, as far as I can find out from internet forums and tuning kit manufacturer websites, the stock ECU is a black box as far as that's concerned. Now, one thing which I do have planned is a head swap using a D15Z7 head and ECU - same applies, it's an OBD2a ECU with no flashable memory, and I want to keep the stock ECU to correctly handle the 3-stage VTEC.

What I was planning there, given an ECU from a 1.5L engine on a 1.6L, was to carefully compare injector flow specs, and use an aftermarket adjustable fuel pressure regulator to increase the pressure 5-10% to keep the ECU within its parameters (especially in open loop mode) and keep the engine happy. On a side note, I went and spent money on parts before checking that theory - am I on the right track there?

Do you think the same would work (i.e. with no ECU tuning per se) in terms of tuning open-loop fuel flow for a non-stock header (assuming the ECU can handle closed-loop conditions correctly in my case)? I presume doing this properly would require use of a dyno and appropriate exhaust gas measurement? It works in my head, just not sure how it will go in practice