Aftermarket Exhausts?

[weirtech]

i intend to develop an exhaust for this car asap. keep your eyes open for a dyno tested system at the time the car is released.

aaron

[Homemade WRX]

^^and what would be special about it?

[weirtech]

Originally Posted by Homemade WRX

^^and what would be special about it?

1. it will be hand built in north america.
2. it will be built from 304ss mandrel bent 16g tubing.
3. it will be 100% tig welded.
4. it will incorporate unique design features that other manufacturers do not include.
5. it will be warrantied for life.
6. it will be built and dyno tested with videos and documented proof before it is offered for sale.
7. it will have options available for the tips to allow the consumer a choice.

[WingsofWar]

Question for engine tuners; Homemade WRX, argx7, dimman ....ect

so my experience with Flat-4 N/As (EJ20E & EJ25D & EJ251) have led me to believe that much of the power gains from exhaust tuning happen at the header. Also seeing that TWE and OBX EL headers seeing the biggest dyno gains iv encountered personally. While witnessing cat-backs exhausts had very little performance gains on the same engines.

Do you believe this will also be the case this time around for the FA20? Or do you think that the new catalytic system built for direct injection may restrict more power than headers do? Also, are you concerned with higher EGTs due to DI?

Just wondering what you think just off the top of your head.

[Homemade WRX]

Originally Posted by WingsofWar

Question for engine tuners; Homemade WRX, argx7, dimman ....ect

so my experience with Flat-4 N/As (EJ20E & EJ25D & EJ251) have led me to believe that much of the power gains from exhaust tuning happen at the header. Also seeing that TWE and OBX EL headers seeing the biggest dyno gains iv encountered personally. While witnessing cat-backs exhausts had very little performance gains on the same engines.

Do you believe this will also be the case this time around for the FA20? Or do you think that the new catalytic system built for direct injection may restrict more power than headers do? Also, are you concerned with higher EGTs due to DI?

Just wondering what you think just off the top of your head.

Well the exhaust manifold does far more for power than the cat-back section on any engine UNLESS the engine has some really bad design or compromise that hinders it.

As for EGT, I'll have to see what they end up being. May force something a bit nicer than 304 stainless for the manifold. The cat section is my bigger concern. It'll really have to wait until I have hands on one, as it's nothing but guessing and speculation now.

[serialk11r]

Why would EGT be higher with DI? Higher thermal efficiency=lower EGT.
Why would catalytic converter "built for DI" be worse? Toyota claims reduced emissions due to just the DI system alone.

[WingsofWar]

Originally Posted by serialk11r

Why would EGT be higher with DI? Higher thermal efficiency=lower EGT.
Why would catalytic converter "built for DI" be worse? Toyota claims reduced emissions due to just the DI system alone.

Hmmm Im thinking that EGTs would be higher because air mixtures should burn be leaner (cleaner), but result of cleaner tailpipe emissions is super heated NoX. Or so i saw on those Lexus tech articles with the use of new proprietary DI o2 and catalytic technologies.

And they built a catalytic converter to strip down that NoX...but Iv never seen inside of it...so i really don't know how restrictive they are over normal cats.

But anway...higher thermal efficiency for air is usually richer mixture..or at least thats what iv witnessed with my rx7.

So that said...i dont think that the Direct injection is aiding thermal efficieny for tailpipe gases.

[serialk11r]

Thermal efficiency is amount of energy you get out of a certain amount of fuel, but thanks for bringing up AFR, I sorta forgot about that.

In theory, raising compression ratio from say, 10 to 12.5 improves efficiency somewhere around 6% or something like that (but it may be more, as the exhaust opens before the bottom of the power stroke, and on a higher compression motor the exhaust opening blows less pressure out), so the temperature of the exhaust gas should be a little bit cooler (not 6% though, lower exhaust temperature means the cooling system absorbs heat a little slower).

If you need excessive amounts of fuel to cool the cylinder, I guess EGT will be lower for a less efficient engine without DI. I suppose DI reduces knock by strategically cooling the charge instead of just dumping a lot of fuel in and hoping it works, so the exhaust temperature could be higher. But it's not like they are changing any components downstream of the exhaust port, so they must try to achieve the same exhaust temperatures, if exhaust temperature is the limiting factor. Aka, valves burn up at high temperature = need lower temps, regardless of DI or not. I'm not sure what materials most of this stuff is made of but it seems to me that most steels are good to go at typical exhaust temperatures.

[Homemade WRX]

Originally Posted by serialk11r

Why would EGT be higher with DI? Higher thermal efficiency=lower EGT.
Why would catalytic converter "built for DI" be worse? Toyota claims reduced emissions due to just the DI system alone.

which are my thoughts as well. Also what I now of cold start emissions control issues for DI, I'd suspect colder EGT is what we will actually find. This is where my concern of the cat/exhaust manifold configuration comes into play...for those that actually get cold smog tests.

[WingsofWar]

Originally Posted by serialk11r

Thermal efficiency is amount of energy you get out of a certain amount of fuel, but thanks for bringing up AFR, I sorta forgot about that.

In theory, raising compression ratio from say, 10 to 12.5 improves efficiency somewhere around 6% or something like that (but it may be more, as the exhaust opens before the bottom of the power stroke, and on a higher compression motor the exhaust opening blows less pressure out), so the temperature of the exhaust gas should be a little bit cooler (not 6% though, lower exhaust temperature means the cooling system absorbs heat a little slower).

If you need excessive amounts of fuel to cool the cylinder, I guess EGT will be lower for a less efficient engine without DI. I suppose DI reduces knock by strategically cooling the charge instead of just dumping a lot of fuel in and hoping it works, so the exhaust temperature could be higher. But it's not like they are changing any components downstream of the exhaust port, so they must try to achieve the same exhaust temperatures, if exhaust temperature is the limiting factor. Aka, valves burn up at high temperature = need lower temps, regardless of DI or not. I'm not sure what materials most of this stuff is made of but it seems to me that most steels are good to go at typical exhaust temperatures.

in the early engine thread i gave pictures of the IS250 & RS4 exhaust valves all burned and fucked up. + oil and carbon accumulating everywhere because of sealing failure heat. i don't know hoe much cooler port injection is going to make egts and what what loads/rpms are we going to see issues. because of this heat during ultra lean burning.

[Homemade WRX]

though valves are burning because of oil/carbon accumulation keeping them from sealing and that caused them to burn up. The port injection should help to keep it clean. As for lean burn, at light load, there will be less heat (less energy)...I doubt that we'll be seeing a 'lean' burn under load at RPM. I know the port injection is used for higher load at lower speed in conjunction with the DI.

[Dimman]

I all honesty 304 doesn't belong in headers, and is just acceptable for exhausts. 321 is the right way to go.

As for exhausts not getting huge gains, it could be that they are not matched up well to the cam/valve events for their length. To get stronger negative wave returns from the whole exhaust, it looks like they will need to be shorter (given stock cam duration estimate of ~200 effective degrees). Will need to test this, though...

[serialk11r]

Originally Posted by WingsofWar

in the early engine thread i gave pictures of the IS250 & RS4 exhaust valves all burned and fucked up. + oil and carbon accumulating everywhere because of sealing failure heat. i don't know hoe much cooler port injection is going to make egts and what what loads/rpms are we going to see issues. because of this heat during ultra lean burning.

The only people doing lean burn these days are the Germans; Their cars have high enough MSRP to throw in a NOx absorbing catalyst into the exhaust. True lean burn (like 20:1 AFR for low pumping losses) does not burn hotter, in theory a flame burns hottest at stoichiometric, but at stoichiometric it's hard to get an efficient burn. Slightly lean gives the hottest burn because more of the fuel is burned, and air is easier to heat up than liquid fuel. Hottest temp happens at around 1.1 equivalence, about 16:1 AFR. Then after that, the lower proportion of fuel means the temperature decreases. At 18:1, the flame temperature is about the same as stoichiometric. Coincidentally, this is where hydrocarbon emissions are lowest, as there is excess oxygen to consume nearly all the HCs, and temperatures are high enough to promote the combustion reaction.

People who "tune" for fuel economy by lowering AFR only a tiny bit don't know what they're doing. All that does is massively increase NOx, increase peak temperatures, and barely decrease fuel consumption. If it were me, I would go 18:1 or so, because hydrocarbon emissions from low combustion temperature are much worse when you get to 20:1 while NOx only goes down a little. 18:1 is cutting 20% of the fuel energy, but then exhaust temperature is lower so you are looking at somewhere between 15-20% drop in power. This means you can reduce manifold vacuum by up to 25%, which could be very useful for fuel economy.

Dimman 200 degrees for the exhaust? Previous Toyota dual VVT-i fixed lift have been more like 220-230 I think...

[Dimman]

Originally Posted by serialk11r

The only people doing lean burn these days are the Germans; Their cars have high enough MSRP to throw in a NOx absorbing catalyst into the exhaust. True lean burn (like 20:1 AFR for low pumping losses) does not burn hotter, in theory a flame burns hottest at stoichiometric, but at stoichiometric it's hard to get an efficient burn. Slightly lean gives the hottest burn because more of the fuel is burned, and air is easier to heat up than liquid fuel. Hottest temp happens at around 1.1 equivalence, about 16:1 AFR. Then after that, the lower proportion of fuel means the temperature decreases. At 18:1, the flame temperature is about the same as stoichiometric. Coincidentally, this is where hydrocarbon emissions are lowest, as there is excess oxygen to consume nearly all the HCs, and temperatures are high enough to promote the combustion reaction.

Dimman 200 degrees for the exhaust? Previous Toyota dual VVT-i fixed lift have been more like 220-230 I think...

Effective. A lot seem to hover around ~200ish at .050" lift. This one will probably be a bit more but not much, but that's what I'm starting with guess-wise. It will probably be reasonably conservative cam-wise, as that matches their apparent goal of a good, long powerband.