Aftermarket Exhausts?

[serialk11r]

Okay yea I guess that's about right, completely closed perhaps 10 degrees ATDC, starts to open something like 30 degrees BBDC.

[Dimman]

For a rough estimate of a 68" total exhaust length (from the valve, not the head) will return a negative pulse in ~272 degrees @ 6000 rpm. So its max effective range may be ~4500 rpm. At 78" it would max out ~4000 rpm.

Edit: And that's not specifically targeting the overlap period, just how long for the wave to return, before exhaust closes.

[serialk11r]

Wait a minute Dimman, didn't you say, exhaust cams are 200 degrees? :P
Remember, the intake cams are likely just long enough to get max VE at 6000rpm or so with no valve overlap! If you want to have the negative pulse do anything, you first need longer duration intake cams to even be able to give it overlap without killing power.

Also what are you using as the speed of sound? I got >600m/s with 800C exhaust...just eyeballing your numbers makes me feel like they're not right.

[WingsofWar]

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.

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...

So your pretty confident that regardless of what happened in the past or happens with other automakers doesn't really matter now in this application. Especially pertaining only to heated gas temps at the header.

Ok! just wondering,

also ..doesn't lowering AFR do the opposite of what you described? aka lower egt, increase fuel consumption, incease HC. I think you ment raise AFRs eg..lean it.

[serialk11r]

Originally Posted by WingsofWar

So your pretty confident that regardless of what happened in the past or happens with other automakers doesn't really matter now in this application. Especially pertaining only to heated gas temps at the header.

Ok! just wondering,

also ..doesn't lowering AFR do the opposite of what you described? aka lower egt, increase fuel consumption, incease HC. I think you ment raise AFRs eg..lean it.

lol sorry, I think in terms of fuel quantity yes higher AFR is correct.

[Dimman]

Originally Posted by serialk11r

Wait a minute Dimman, didn't you say, exhaust cams are 200 degrees? :P
Remember, the intake cams are likely just long enough to get max VE at 6000rpm or so with no valve overlap! If you want to have the negative pulse do anything, you first need longer duration intake cams to even be able to give it overlap without killing power.

Also what are you using as the speed of sound? I got >600m/s with 800C exhaust...just eyeballing your numbers makes me feel like they're not right.

I'm using 1500 feet/sec, so a bit slower. Also keep in mind that the negative pulse can still enhance scavenging even with no overlap as it reduces the force that the piston has to exert pushing out gas.

[serialk11r]

So sorry if I'm wrong, but you'd want the exhaust pulse to hit quite a while before the next exhaust valve opens right? Usually cylinders (for a 4 cylinder engine at least) are paired up separated by 360 degrees, and the length between them is relatively short. Now for cylinders that fire right after each other, you could get that sort of total length that the exhaust pressure wave travels. Now at full load the exhaust temp is closer to 800C than whatever would give 1500ft/s, and 800C gives something like 650m/s speed, which is about 2150ft/s.

Sorry, I don't trust your calculations. Lemme try this out :P
72"/2100ft/s (let's make this simple) is 1/350 seconds. 6000rpm would be 1 rotation every 1/100 of a second, so the exhaust wave takes about 100 degrees to hit the next cylinder. What is the usual "wavelength"? I'm not sure of it...I remember arghx7's neat little chart showed that pressure went negative something like 90 degrees after. I guess that's in line with your calculation.

[Dimman]

Originally Posted by serialk11r

So sorry if I'm wrong, but you'd want the exhaust pulse to hit quite a while before the next exhaust valve opens right? Usually cylinders (for a 4 cylinder engine at least) are paired up separated by 360 degrees, and the length between them is relatively short. Now for cylinders that fire right after each other, you could get that sort of total length that the exhaust pressure wave travels. Now at full load the exhaust temp is closer to 800C than whatever would give 1500ft/s, and 800C gives something like 650m/s speed, which is about 2150ft/s.

Sorry, I don't trust your calculations. Lemme try this out :P
72"/2100ft/s (let's make this simple) is 1/350 seconds. 6000rpm would be 1 rotation every 1/100 of a second, so the exhaust wave takes about 100 degrees to hit the next cylinder. What is the usual "wavelength"? I'm not sure of it...I remember arghx7's neat little chart showed that pressure went negative something like 90 degrees after. I guess that's in line with your calculation.

I don't always either. Math isn't my strong point, and given a couple screw-ups on here, neither is double checking the formulas on my spreadsheet. But I'll take public errors if it means I get corrected and learn.

As for the wavelength, in one of the books I have they show it's length and amplitude change with rpm, which sort of makes sense. (Shows stronger and shorter as rpm increase.)

[Homemade WRX]

Originally Posted by Dimman

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

Oh, I agree. You also have to think of how many people won't want to pay for a 321, Ti or Inc 625 manifold

[Dimman]

Originally Posted by weirtech

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.

I'm not seeing the special part.

Compare with Chinese 'Brand X':

Yours Brand X
1. Not built in US Check Check
2. 304SS mandrel bent Check Check
3. TIG welded Check Check
4. Questionable marketing Check Check
5. Warrantied for life ? Nope
6. Dyno tested Check Depends on importer
7. Tip option Check There will be countless
8. In it for the money 1st post was promoting this Definately

In detail:
1. Why dance around the fact that you are in Canada with the North American part? Are you at least sourcing your tooling or materials from there to have some justification to patriotic American buyers? If that's the case, at least say 'Made in Canada with American-sourced materials.'

2. Everything on the market will be.

3. Most will be. Saw a GT-R exhaust from a brand-name company that was flux-cored with TIG a $ option. But most Chinese stuff is robotic TIG, exhaust anyways, headers not so much.

4. Any details on this? V-bands? Secret sauce? At least tell us what will make your product different.

5. Warrantied for life. A plus for people thinking of keeping it a long time. This is the only thing I see as somewhat special, but there are importers of Chinese systems that are offering this, too.

6. I've known enough tuners to know that these are not 100% reliable or repeatable. Would you be willing to tie in a guarantee of gains with your warranty. +X hp minimum on Dyno Dynamics, +Y hp minimum on Dynojet?

7. Tip option is hardly a big deal, there is going to be a ton of competition making exhausts for this car, with tons of available options.

8. This response is mainly because the 'North American made' part irked me as misleading (despite me being Canadian), and that your first posts were trying to solicit business. No introduction, not engaging in the theory, just 'I want to sell you guys exhaust.'

[weirtech]

first let me apologize for not having almost as many posts as there are members here. i'm just a very small shop trying to offer help to a newly developing community of bright guys like you. i'm no engineer, i'm just a guy who likes to fabricate. i will take my first hand experience over anything i can read in a book. if it is an interesting idea or theory, i'd much rather apply it than philosophize about it.

1. i will be building it in canada with canadian supplied materials.
2. i agree, this isn't all that special, it was more to be open and state my material of choice.
3. i suppose this puts me in with the "most" category... still a catagory i'd rather be in nonetheless.
4. i'd rather not disclose what i plan to include in my design for the best interest of my own business. i'd think v-bands are considered a standard now, aren't they?
5. for life. i'm not saying my stuff is perfect. nothing is. but i will always repair or replace what i build at my own expense. if you cannot stand behind what you do for a living, then you have to ask yourself: is it worth doing? i wish you well getting something repaired that was made offshore and could be bought on ebay. when a customer wants to contact me, the only need send me a text and i respond. or make a call and i answer, not some schmuck sitting at a desk sending emails all day and taking orders.
6. i do a base pull that is on video, then i intend to do a direct bolt on with nothing else done and another video on the dyno. a dynajet will be used, but i'd think the increase would be able to be measured to the same ratio on any other dyno. #5 will also cover this if you do the same test i do and are not satisfied with the results. i will gladly make a refund once the product is returned.
7. yes there will be tip options available from other manfacturers, but how many will be offered by the same manufacturer- 2 at most?
8. i think my first paragraph covers that.

[Dimman]

Originally Posted by serialk11r

So sorry if I'm wrong, but you'd want the exhaust pulse to hit quite a while before the next exhaust valve opens right? Usually cylinders (for a 4 cylinder engine at least) are paired up separated by 360 degrees, and the length between them is relatively short. Now for cylinders that fire right after each other, you could get that sort of total length that the exhaust pressure wave travels. Now at full load the exhaust temp is closer to 800C than whatever would give 1500ft/s, and 800C gives something like 650m/s speed, which is about 2150ft/s.

Sorry, I don't trust your calculations. Lemme try this out :P
72"/2100ft/s (let's make this simple) is 1/350 seconds. 6000rpm would be 1 rotation every 1/100 of a second, so the exhaust wave takes about 100 degrees to hit the next cylinder. What is the usual "wavelength"? I'm not sure of it...I remember arghx7's neat little chart showed that pressure went negative something like 90 degrees after. I guess that's in line with your calculation.

I had to go back and check where my velocity number came from since I didn't calculate it.

The issue is temperature along the entire length of the exhaust. It doesn't stay constant. The source I have measured the wave at ~2000 ft/sec just off the port but the measured average ranged from 1300-1700 ft/sec based on return timing. Plus the velocity changes with rpm/throttle. So I just picked the middle as my starting point.

[GT3076rBRZ]

Meh, none of these options are worth it to me. I'm gonna build my own, using 42dd 4.5" tips, full stainless tubing with one borla muffler and delete the cats and just use test pipes. V-banded all the way back. I can make a better if not just equal exhaust that will sound better for half the cash.

[Subaruwrxfan]

I sent Password JDM an email today asking if they will develop an exhaust. I love what they did with the GT-R, turned a rather boring exhaust tone into something completely insane. I really hope they come up with another innovative design that actually makes this car sound like a sports car with a semi-exotic sound rather than having it sound like a toyota 4 banger or subaru boxer.