CRG Racer24
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- '11 Mazda2 GX-Convenience Pkg.. Warranty Voiding Mods
Exactly what I was thinking ^^.
Dyno charts for my 2
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Exactly what I was thinking ^^.
Mazdamatic
Member
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- Mazda 2 Sport
im really anxious to dyno mine
i think with the 2.5 in exhaust ill see
20lbs ft (LOL) and over 100hp (or an opposite of what he saw) i know i lost tork but i feel a top gain.
this car is interesting.
Holy way too big exhaust! I'm willing to bet you will see a net loss in power with that exhaust size. Maybe a little HP gained at the very top end.
not necessarily. if you look at his torque curve, it still looks pretty healthy. a lot of modern engines really like to breath, and i'm sure the Mazda2 is no different.
No doubt there'll probably be some gains up top but I'm willing to bet they don't offset the loss in the low-mid range. 2.5" just seems so big for a little 1.5L, even if it has relatively high compression. IIRC, redline is like 6200 rev/min, which shouldn't be high enough to require 2.5". All I'm saying is you could probably go smaller and still have the same high-end gains with less low-end loss.
i'm going to content that his graph still looks great. but, we will never know without a companion graph showing the stock curve.
Just remember guys, I don't have the 2.5" exhaust. That's another poster in this thread. My exhaust is a single resonated 2" (well 2.25" non mandrel bend, so roughly 2" equiv).
So my curves are based on that, not 2.5".
So my curves are based on that, not 2.5".
like magnum says, you will have s*** for useable torque with an exhaust that wide on a 1.5L. People had s*** for useable torque on a 1.8L running a 2.5 inch exhaust and only got better with FI.
Honestly, i think with a 2.5 you'd be moving your torque curve way out of the usable fun range. You will definately see HP increases but it might not be more than you think because of once again...our Rev Limit.
Get a piggyback and raise the rev limiter and I can support you, but i think you'd have to raise it to at least 8k rpm for it to be useable...but then you have to get everything retuned for after our redline where the ecu has no pre-written tune at all.
I'd seriously think about this. I don't think you're going to be too happy with your results. I'm with magnum on this one...maybe 2.25 at the very very most...
Mazdamatic
Member
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- Mazda 2 Sport
so far i love it. since most my daily is freeway the top end is good. i actually didnt notice too much low end (at first i thought i did but that was low tire pressure) car tends to rev to 2500 so i never really see tork but anything over that and its quite nice =] and the sound.....hehehe....
but like i said gotta dyno it soon with my group.
CRG Racer24
Member
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- '11 Mazda2 GX-Convenience Pkg.. Warranty Voiding Mods
2.5 I think is too big, but I disagree with the 2.5" being "s***" for 1.8L engines.. Coming from a Honda background, especially on Type R's, 2.5" is the way to go. The more mods you put on it, the more beneficial it get's.
On the other hand, 2.25" is the biggest I'd go on our engine. Unless you're FI, it makes no sense to me.
On the other hand, 2.25" is the biggest I'd go on our engine. Unless you're FI, it makes no sense to me.
Mazdamatic
Member
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- Mazda 2 Sport
Just remember guys, I don't have the 2.5" exhaust. That's another poster in this thread. My exhaust is a single resonated 2" (well 2.25" non mandrel bend, so roughly 2" equiv).
So my curves are based on that, not 2.5".
well if you wanna go with non mandrel bend then mine is 2.25 equiv.
also im automagic so thatll be interesting to see the power curve.
Type-R revs higher, hence why i was talking about him raising his rev limiter to make better use of his power if he decides to do it.
Thats really it...
CRG Racer24
Member
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- '11 Mazda2 GX-Convenience Pkg.. Warranty Voiding Mods
"People had s*** for useable torque on a 1.8L running a 2.5 inch exhaust and only got better with FI." - I was purely referencing that. But yeah I agree with you though, though our engines will not support 8k rpm (unless modded so), which goes with both of our statements.. 2.5" is too big.
Racebrewer
Member
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- Mazda, Mazda 2 Touring MT
Yup. 2.5" was the way to go on a 1.8 Type R....... Until the first time somebody put on a 3" and picked up a little more (not FI), without losing low end.
There are a couple issues, such as the computer needs a little time to re-learn the change in A/F Ratio. Cam timing might also have to change to get the best out of it.
John
There are a couple issues, such as the computer needs a little time to re-learn the change in A/F Ratio. Cam timing might also have to change to get the best out of it.
John
hey guys check out my wheels font motorsports dot com
The moral of the story is "size your exhaust to your needs." Larger diameter exhausts will generate more power at higher engine speeds while lesser diameter exhausts promote low-end power. My layman's way of interpreting this is through exhaust velocity, which is what you want in a N/A engine. Low engine speeds mean less exhaust gases (mass flow) so you need a smaller exhaust to keep velocity up. However, that smaller exhaust restricts mass flow at higher engine speeds so a larger diameter is needed. This is simplifying everything as there are a number of other factors in exhaust tuning such as primary/secondary lengths and the use of merge collectors, megaphones, etc. but it gives the general idea: there's no sense in putting an exhaust tuned to 8000 RPM on a car with a 6200 RPM redline. Even on a car with a 8000+ RPM redline it all comes down to what you want. For example, my 9000 RPM redline RX-7 will have a 2.5 in. exhaust as I'm seeking peak power in the 8000 RPM range. Since it will see a lot of track duty above 4000 RPM I really don't care about low-end losses. However, for a "street car" I would think you'd want the "fattest" power/torque curves as possible.
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where did that horse go... (deadhorse
http://www.flyinmiata.com/tech/dyno.php
scroll down a little bit, and you'll see this entry:
"1.8, FM turbo exhaust
Robert Webb's stock, normally aspirated '96 with and without FM turbo single exhaust. Damn loud, but made a nice boost. So much for big (2.5") exhausts causing a loss of torque."
and, here is the dyno curve:
http://www.flyinmiata.com/tech/dyno_runs/Robert_Webb_082099.pdf
bone stock miata, comparison between stock exhaust and full 2.5" turbo exhaust, gains across the whole rev range.
http://www.flyinmiata.com/tech/dyno.php
scroll down a little bit, and you'll see this entry:
"1.8, FM turbo exhaust
Robert Webb's stock, normally aspirated '96 with and without FM turbo single exhaust. Damn loud, but made a nice boost. So much for big (2.5") exhausts causing a loss of torque."
and, here is the dyno curve:
http://www.flyinmiata.com/tech/dyno_runs/Robert_Webb_082099.pdf
bone stock miata, comparison between stock exhaust and full 2.5" turbo exhaust, gains across the whole rev range.
Yeah, I'll keep beating it...
In the same link, if you scroll down a little to the first entry in "Our 99" you'll see a number of curves with the 2.25" exhaust on a stock '99 Miata. Referencing "run 30," which appears to have everything set up as stock you'll see ~108 ft-lbs and ~110 HP with the 2.25" exhaust. With the 2.5" exhaust you posted the numbers are ~104 ft-lbs and ~108 HP respectively. I'm not that familar with Miatas so maybe there is a difference between the '96 and '99 model years and I know we're comparing two different cars with different engines, but those results would appear to show that the smaller exhaust does make a little more power and torque. Trivial? Sure, but given the +$96 cost of the turbo exhaust it makes more sense to me to stick with the 2.25".
