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Discussion Starter #21
thing is my main concern of doing this as short of possible is not 3-5 hp gain.. (even if), its the 50 lbs weight hanging of the back end..... and I want to loose that, as long as it is not TOO loud.
 

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Discussion Starter #23
I have the 2.5" catpipe, but I need to fit it to something...... I didn't get ppe muffler for the swap, so now trying to figure out a way around it. I don't mind sticking original muffler for emission purposes, but definitly want it off along with ppe cat pipe once emission passed.
 

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The PPE cat pipe and muffler doesn't way anything close to 50lb.
A listing of the OEM exhaust system weights:
muffler 27.6
catalytic converter (3rd & final) 16.8
exhaust manifold cover 2.4
exhaust manifold (w/ cats) 16.2
exhaust splash shield 1.2
heat shield -small 0.2
heat shield -exhaust (black) 1.2
hardware (total of removed) 3.4
total 69 lbs.

My current system; header/decat/muffler is just over 23 lbs.
I have the OEM heatshields fitted to the heather.

The power gains are, within n.a. terms, considerable.
 

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I said PPE, not OEM, and we are only talking about the system from the header outlet to the tailpipe, not the header itself. HP gain from a muffler and header back exhaust is minimal. Mostly in your head as it is louder.
 

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Discussion Starter #28
A listing of the OEM exhaust system weights:
muffler 27.6
catalytic converter (3rd & final) 16.8
exhaust manifold cover 2.4
exhaust manifold (w/ cats) 16.2
exhaust splash shield 1.2
heat shield -small 0.2
heat shield -exhaust (black) 1.2
hardware (total of removed) 3.4
total 69 lbs.

My current system; header/decat/muffler is just over 23 lbs.
I have the OEM heatshields fitted to the heather.

The power gains are, within n.a. terms, considerable.
What exactly did you do post header setup
 

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I'm not from the USA? Here if you get caught with a car that has been deleted there is a fine. Not nearly a big enough one IMO.
 

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I'm not from the USA? Here if you get caught with a car that has been deleted there is a fine. Not nearly a big enough one IMO.
From a climate and emissions standpoint the US rejoin is mainly already being met with renewables. I highly doubt you will see stricter limitations on existing vehicles in most states. Likely we will just start mandating more EV's. Here in Colorado even in the most strict counties its an OBDII inspection on a rolling road. If you fail HC or NOX you need to fix it but as far as modifications they don't open the hood unless the car is on fire.
 

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From a climate and emissions standpoint the US rejoin is mainly already being met with renewables. I highly doubt you will see stricter limitations on existing vehicles in most states. Likely we will just start mandating more EV's. Here in Colorado even in the most strict counties its an OBDII inspection on a rolling road. If you fail HC or NOX you need to fix it but as far as modifications they don't open the hood unless the car is on fire.
While this is true the power that California holds over the auto industry is incredible. Major manufacturers have to meet California standards, not Federal standards in many cases. While I think this is admirable in theory a lot of the harassment of modified cars in California is way over the top IMHO. That said, running a cat on a daily driven car is the only way to go.
 

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I used an stainless 'ADJUSTIBLE" muffler for 15 years.

Yes, I said adjustable.

By adding more "baffles" to the end of the unit the plasma flow is increased.

BTW ya'll got the hot exhaust wrong, wrong wrong.
The hotter the exhaust walls the faster the flow.
You wrap headers to keep heat in.
SuperTrapp.jpg
 

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I used an stainless 'ADJUSTIBLE" muffler for 15 years.

Yes, I said adjustable.

By adding more "baffles" to the end of the unit the plasma flow is increased.

BTW ya'll got the hot exhaust wrong, wrong wrong.
The hotter the exhaust walls the faster the flow.
You wrap headers to keep heat in. View attachment 80635
Exhaust is not plasma, it is just hot gas. And while theoretically, yes keeping more of the heat in will increase the average velocity in the pipes, it does this at the expense of increased back-pressure. The effect is roughly the same as using smaller diameter pipes. If you want to get better scavenging, get a better designed exhaust manifold. And as for the main reason not to wrap headers, see this: Why you should not wrap headers – Roth Automotive Science
 

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Discussion Starter #35
Exhaust is not plasma, it is just hot gas. And while theoretically, yes keeping more of the heat in will increase the average velocity in the pipes, it does this at the expense of increased back-pressure. The effect is roughly the same as using smaller diameter pipes. If you want to get better scavenging, get a better designed exhaust manifold. And as for the main reason not to wrap headers, see this: Why you should not wrap headers – Roth Automotive Science
Kinda knew that. Theoretically wrapped headers will also be louder due to more hot gas (not sure if human ear can tell the difference) --- But yeah, never planned to wrap them tbh.
 

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It’s an interesting response in the link, especially considering the number of professional racing applications that do use wrapped headers. Of course they have the liberty of being sponsored so stressing the manifold isn’t really an issue. I find it more curious that supposedly this would have detrimental effects on engine performance...leads me to believe there is more to the story. If I had more enthusiasm I would look for an actual SAE study but such is life for now.
 

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It’s an interesting response in the link, especially considering the number of professional racing applications that do use wrapped headers. Of course they have the liberty of being sponsored so stressing the manifold isn’t really an issue. I find it more curious that supposedly this would have detrimental effects on engine performance...leads me to believe there is more to the story. If I had more enthusiasm I would look for an actual SAE study but such is life for now.
I have not seen a top-level professional race car with wrapped headers. Also, the effect on performance (+ or -) is miniscule and this tiny effect is overshadowed by the different choices you may have in headers design.
 

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Discussion Starter #38
same regarding race cars. also looked up in google some le-mans prototype engine bay and they also had pretty much straight pipe headers without any wrapping. I think wrapping probably caught on from Japanese market.
 

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I had a Magnaflow muffler immediately after the header. It was loud but I didn't need ear plugs. I'm not sure how many track hours I put on it, but I don't recall its sound-dampening performance degrading.

80795
 

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The exhaust and intake are similar in the engineering stand point of keeping the engine breathing. The pulsations of the exhaust gases exiting the head are used to help tune the gases leave and assist in reducing pumping losses. There are calculations to determine the right length, size, etc. Based on the length needed, the twists and turns are needed due to the space constraints the MR2 has. You could definitely just connect the muffler to the headers, but the flow and performance will go down in theory as well as increase in noise and other things.
This is important to consider.

I did a compression test on my 1zz before I moved on to a 2zz and found compression to be fine. As far as I could tell, the motor was healthy, with about 110,000 miles and 24 racing hours. The last dyno on it revealed it to make 119 whp, which is less than a stock 1zz (usually about 125 whp), despite the fact I was using the PPE header, cold air intake, and the magnaflow straight through muffler. I can't say why the motor was down on power, but my exhaust setup may have resulted in a reduction of power. Were I to do it again, I'd do more research.


Another thing to consider. Losing weight is good, but its worth considering where the weight is. The Spyder has a 45/55 weight distribution. A nominal weight distribution is closer to 40/60. Removing weight from the back could hurt you overall (or help, if you want to make the car easier to drive at the expense of overall performance).

I'm with Funkycheese on this one. I'd go with the PPE system if cost isn't an issue. It weighs far less than stock, and is probably engineered to make power versus losing it.
 
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