Im trying to settle a debate with a friend who is going S/C with his Sunfire Ecotec. The S/C has been opened, ported and polished and running a 2.9 or so pully.
He wants to run 2.25 mandrel exhaust, I told him he should be running 2.5. What would be the best exhaust size to use for the best torque and / or horsepower?
lsj pacesetter armor coated header, into 2.5in piping.
I am the one that this debate is about...the setup i will be running was dynoed at 248 HP and 218 ft/lbs of torque with teh lsj header, and 2.5 inch all the way back
when i asked about the torque and why it was so low in comparison, I was told be Alan (californiadomestics) that it was because of the 2.5 inch exhaust and that 2.25 would raise the torque values.
if this is wrong, prove it....i dont wanna hear about a turboed car, or an n/a car. lets hear from the guys with the m62, teh lsj header, with the h/e setup and running meth and see what they say. oh yeah, and otherwise bone stock motor...i also run a AEM cold air.
Edited 1 time(s). Last edited Sunday, January 25, 2009 1:34 AM
You have an PD blower pumping air into your engine -even 3" would be suitable. Anything that can increase the efficiency of the system will cause a pressure drop on the manifold and reduce the temperature of the charge. Remember the blower moves a fixed VOLUME (per unit time of air), and the pressure is dependent on the restriction in the system. Less pressure for the same volume is a good thing in this case.
As far as your numbers - they are very respectable. 248hp is that at the wheels? If so that is great for the M62 IMO. Check out what some of the LSJ guys are making on stock exhausts, 2.5" and 3". Your doing fine...
All I can tell you is what I have which is a 2.25 exhaust with a pacesetter header. I make about equal whp and wtq.
some food for thought though if you look in the GM build book the Grand am cup car they made was using 3" exhaust.
2.5 will work and probably be quieter and I was able to run some decent times with that. This winter I'll be upgrading to a 3" w/ the LJS header vs the L61 header that I currently have. The LSJ has larger primaries and a larger collector.
As oldskool said most of the cobalt guys are running at least 2.5, mostly 3" from what I could find before.
12.770 @ 111.99 Intercooled Eaton M62
I was running a 2.5" exhaust and put out low tq numbers as well.
2.5" sounds about perfect for your setup. Going to a 2.25 would be a waste of money. I don't think you would pick up much if any tq and if you do it might be at a loss to peak hp. Your numbers sound right inline with what I would expect from your setup.
FORGET GIRLS GONE WILD WE HAVE GOVERNMENT SPENDING GONE WILD!
i already have a full 2.25 exhaust setup...thats the thing. I dont wanna HAVE to change it. so I think i will run it for a bit, and then maybe swap everything out for 2.5
With a supercharger you are effectively increasing the displacement of the motor. In-other-words, you are moving the volume of air that a larger motor would move, so you would need more capacity from the exhaust.
The other thing to consider is that a boosted motor doesn't use savaging to draw the next air/fuel charge into the cylinder, because it is being pushed in by the supercharger (or turbocharger). You would want a larger system to allow freer flowing exhaust, the motor doesn't work as hard to push the spent charge out.
If you ever look at the duration figures of a supercharger cam (or nitrous cam, for that matter), you'll notice that there is about 10-12 degrees more exhaust duration than intake duration. This is done to give the exhaust more time to evacuate the combustion chamber, so it can be filled with a cleaner intake charge.
To maximize the supercharger's capabilities, I would use the LSJ header, 3" exhaust, a supercharger cam (Comp Cams Ecotec Supercharger Cam), a P&Ped head with the largest valves available and HPT tuning.
Edited 1 time(s). Last edited Sunday, January 25, 2009 10:38 AM
Of forgot to say this WILL NOT be HPtuned. i will be using the gm reflash,and taking it to it fullest capabilities with meth, heat exchange, and a 2.9 pulley. That is what this is really about. Im not trying to tune the car for 300 HP or anything like that. I am hoping for around 235 (less then the previous owner with the exact same set up), and will be very very happy with that until a motor build comes in a year or so.
Edited 1 time(s). Last edited Sunday, January 25, 2009 10:48 AM
2.5" minimum, or 3" would be adequate. id be ok with 2.5" your call. id say 2.25 is too small though.
3" with a perforated core type glasspack turbo muffler. (Dynomax UltraFlo, or a Magnaflow, ect..)
11.92 @ 122.69 MPH Rotrex Blower / Intercooled / Water-Meth / 100% Daily Driver / 381 WHP
so what you guys are saying is 3" for set ups like what ecocav and myself are running?
i have 2.5" on mine and am at 225 hp with low boost. on 6.5 psi
Oyyyyyyyyyyyyy. Just 6 months ago everyone was saying 2.25 with a supercharger was the way to go now i'm hearing 2.5-3 or higher.
I feel your pain. The only reason I would consider 3" is again b/c of the GM build guide and as conservative as GM tends to be for them to recommend a 3" makes me think I should also....so much spent on borla cat back
go with atleast 2.5" and if u really want about 235hp u dont need much. mine dynoed 231whp and bout 215wtq. all i have is tr6 plugs, aem intake, 3.1 pulley, lsj pacesetter header, 2.5" exhaust, magnaflow muffler and cat. bosch he pump and a cobra he. all on the gm reflash. stock everything else.
not sure if the meth will actually help you on the gm reflash since it runs you super rich already, when i tested that on the dyno, i lost around 6-8hp when i turned the meth on, i was running the gm calibration at that time, well i still am but hopefully not for long..
12.33 @ 111.67 mph [Oct 2009]
Dyno'd on 08/02/09 - Mustang Dyno:
327.6 WHP 333.6 WTQ [10.1 AFR]
I make more whp and tq and run a 2.25 but I also have hp tune...so it is hard for me to gauge if it is really a gain to go to a larger exhaust
I would go hptuned if i could find a nice baseline file to start with, but i dont know what it takes to tune, and the person i know that does suggests the GM flash
OK, also to go on top of this, if i were to stay with the 2.25 setup, what ressy would everyone suggest?
EcoCav (DesertTuners) wrote:http://www.allmagnaflow.com/product.php?productid=440&cat=0&page=1
Thats the only one you want Chris (just in the 2.25 size). Dont make the mistake I made with a Cherry bomb... mine is toast after 2 months.
i have this one or similar looking one from magna flow. i have 2.25" exhaust.
not sure why someone would recommend the gm calibration over a good tune with hpt. if you dont know how to tune, then i suppose he just said use the gm one, but if you can do it or are willing to learn, why not use hpt
12.33 @ 111.67 mph [Oct 2009]
Dyno'd on 08/02/09 - Mustang Dyno:
327.6 WHP 333.6 WTQ [10.1 AFR]
evilmonkitar wrote:EcoCav (DesertTuners) wrote:http://www.allmagnaflow.com/product.php?productid=440&cat=0&page=1
Thats the only one you want Chris (just in the 2.25 size). Dont make the mistake I made with a Cherry bomb... mine is toast after 2 months.
i have this one or similar looking one from magna flow. i have 2.25" exhaust.
not sure why someone would recommend the gm calibration over a good tune with hpt. if you dont know how to tune, then i suppose he just said use the gm one, but if you can do it or are willing to learn, why not use hpt
Evil, do you mind if I ask what your putting down? I have 3 pulleys, the 2.0, the 3.0 and the stock. I eventually someday will HP tune depending on how long i keep the car and so forth, but to start, the gm reflash will work fine i have been told. Alan had it on his car with the cobra h/e and meth, and everythign otherwise stock. o if he can pull it off, I'm pretty sure he will help me pull it off.
