Noob question

jko · Postby **jko** » Sat Aug 15, 2015 7:02 pm

Would there be any issues in terms of performance loss or any bottlenecking if I replace my stock extractors with 2" ones if the rest of my exhaust system is 2.25"?

I would have gone for 2.25" extractors but Empire performance are the only ones I could find that come in 2.25", and they're not that great from what I've heard. So I went with Genie Performance extractors instead as I've read many good things about them!

jko · Postby **jko** » Sun Aug 16, 2015 11:54 pm

Magpie · Postby **Magpie** » Mon Aug 17, 2015 8:43 am

Have you done any other mods to the car?

Quick and dirty solution - the exhaust system needs to flow 2.2 CFM per engine horsepower therefore a 2¼" pipe would allow about 185 hp.

To calculate header look here http://www.wallaceracing.com/header_length.php

jko · Postby **jko** » Mon Aug 17, 2015 8:53 am

Magpie wrote:Have you done any other mods to the car?

Quick and dirty solution - the exhaust system needs to flow 2.2 CFM per engine horsepower therefore a 2¼" pipe would allow about 185 hp.

To calculate header look here http://www.wallaceracing.com/header_length.php

I've only got a mania intake and the rest of the engine has been left untouched. For the exhaust, I've got a 2.25" muffler and resonator. I have purchased a 2.25" Cat and 2" extractors that are on the way to me now.

project.r.racing · Postby **project.r.racing** » Mon Aug 17, 2015 8:49 pm

should be fine. not all exhausts a tuned perfect.

what car/engine?

jko · Postby **jko** » Tue Aug 18, 2015 1:24 am

project.r.racing wrote:should be fine. not all exhausts a tuned perfect.

what car/engine?

1991 MX5 NA 1.6L

mx589 · Postby **mx589** » Tue Aug 18, 2015 6:33 pm

For a 1.6 2 inch is ok

jko · Postby **jko** » Tue Aug 18, 2015 9:50 pm

so there wouldnt be any issues in terms of affecting performance output in this case if my catback system is a 2.25" and headers are 2"? awesome!

speed · Postby **speed** » Wed Aug 19, 2015 6:47 pm

jko wrote:so there wouldnt be any issues in terms of affecting performance output in this case if my catback system is a 2.25" and headers are 2"? awesome!

That's normal.
I have hurricanes and from memory they have an inside diameter of 52mm (which is 2 inches). stock cat is around 45mm I think, so the cat could be a bottleneck but not in a N/A 1.6; )

jko · Postby **jko** » Thu Aug 20, 2015 12:36 am

speed wrote:
jko wrote:so there wouldnt be any issues in terms of affecting performance output in this case if my catback system is a 2.25" and headers are 2"? awesome!

That's normal.
I have hurricanes and from memory they have an inside diameter of 52mm (which is 2 inches). stock cat is around 45mm I think, so the cat could be a bottleneck but not in a N/A 1.6; )

did you notice any increase in terms of torque? hmm I just got mine installed, can barely feel the difference LOL

speed · Postby **speed** » Thu Aug 20, 2015 9:42 am

When I think about it now, the difference is minimal.
My first impressions were that it spins more freely and was a bit smoother. Power opened up a little but certainly nothing to rave about.

Magpie · Postby **Magpie** » Thu Aug 20, 2015 9:49 am

Butt Dyno = placebo effect or the conformation bias

Hub/Roller dyno before and after tests = real results

What fuel do you run? For example before the headers you used 91 then after the header change you went to 98 then you could be feeling the fuel difference. This is just an example. I can feel the difference in the car when running E85 as opposed to 98.

jko · Postby **jko** » Thu Aug 20, 2015 7:10 pm

Magpie wrote:Butt Dyno = placebo effect or the conformation bias

Hub/Roller dyno before and after tests = real results

What fuel do you run? For example before the headers you used 91 then after the header change you went to 98 then you could be feeling the fuel difference. This is just an example. I can feel the difference in the car when running E85 as opposed to 98.

I've always put 95 or 98 ever since I've owned it

madjak · Postby **madjak** » Thu Aug 20, 2015 7:42 pm

Magpie wrote:Butt Dyno = placebo effect or the conformation bias

Hub/Roller dyno before and after tests = real results

What fuel do you run? For example before the headers you used 91 then after the header change you went to 98 then you could be feeling the fuel difference. This is just an example. I can feel the difference in the car when running E85 as opposed to 98.

Its a common misconception but 91 vs 95 vs 98 makes very little difference to power output unless you have an ecu that can automatically advance timing. The octane rating is the rating of the fuel's resistance to detonation from compression and not a value of the embedded energy. 98 octane does have some extra energy but it's not more than a few percent if that. You only really need to run 98 if you've manually pushed the timing up to 14 from 10 degrees and intend to drive the car on hot days.

Modern cars with smart ecu's will advance timing over time to increase power. In these cars you can run 98 and get power benefits, but one tank of 91 and it will drop timing back down. Also with most cars you need to run 98 for a few tanks to get any benefit.