Will This Exhaust Support 750rwhp On A Boosted Motor?

killer5.0 · Jan 28, 2018

Currently at 500rwhp...my current motor combo will push 600 but not pushing the stock block...waiting until i can build my dart and then push that up to 750-800rwhp. Current exhaust is 1 5/8 mac ceramic unequal shorties, mac offroad prochamber, and spintech ss super pro st 9000 dumps.

New setup plan is 1 5/8 mac shorties (already installed) spintech ss x pipe, ss electric cutouts, and spintech super pro st 9000 dumps ...i may install tails when i get my cobra bumper painted but if i did id probably do 3".

Street only car.

Davedacarpainter · Jan 28, 2018

What do I know, just a marginally improved parrot from another thread. Here's this though.

Or this calculator: http://www.mk5cortinaestate.co.uk/calculator5.php

@mikestang63 ?

RangerJoe · Jan 28, 2018

Can you make 800hp on a small tube shorty header? Probably, but I think your exhaust is designed for half that at best. I think you can get away with a 2.5" exhaust, but the shorties are really going to hold you back.

If you decide to keep them, let your cam designer know so he can try to bandaid the situation.

Joe

FastDriver · Jan 28, 2018

Turbo or blower?

I think you're going to want bigger headers. The exhaust that supports my 900+ rwhp setup is 1 3/4" primaries, 3" crossover to the turbo, 3.5" down pipe. 3.5" to dual 3" through a y-pipe. I used to run a 3" "straight-through" dynomax ultra-flo muffler. It was too loud for my liking. So, I installed another reverse y-pipe with a 3.5" electric cutout and now run 2.5" super-turbo mufflers (didn't work as much as I wanted). I have not dyno'd since the cutout, but I can only imagine that will help a bit with backpressure and maybe help the turbo spool a little earlier.

I don't know what's up with that chart, but if I'm reading it right, I think it's way off.

killer5.0 · Jan 28, 2018

When i build the dart im not opposed to upgrading my headers to longtubes and modifying the x pipe to fit with the longtubes, but on my current setup im not going to bother. That being said is the 2.5" full system adequate (if i upgraded to longtubes)?
I got a good deal on the spintech ss x pipe and already have the ss spintech mufflers (which werent cheap). Adding the cutouts is another cost and hate to do that on the 2.5" only to have to go to 3" later.

FastDriver · Jan 28, 2018

I have no experience trying to run those mufflers or 2.5" duals with that much power. I wouldn't as I believe it is likely to cost some power.

killer5.0 · Jan 28, 2018

Im learning as i go (this car ive built myself and its my first big build)...so if the exhaust is undersized, is the only con that you cant access all available hp or can the added exhaust resistance/backpressure also cause potential issues for the engine (longevity, wear etc)

FastDriver · Jan 28, 2018

There will be additional backpressure, which will be harder on the exhaust valves, but I can't imagine it would be anything like what my turbo does to the valves. So, I'd guess you'd be fine in terms of reliability. You might need stouter valve springs if the pressure is high enough, but you'd need to talk with someone like @EDC about that.

Chuckman · Jan 28, 2018

if it were me i'd start working towards 1 7/8 or 2" longtubes and full 3" from the collectors back. a 3" catback on a 500rwhp car wont hurt, so why do it twice if youre going to up the power later?

FastDriver · Jan 28, 2018

That's exactly what I'd be aiming at, @Chuckman

killer5.0 · Jan 29, 2018

I assume a 2" is tough to fit in the engine bay? 1 7/8? Ill be running a MM steering shaft (for 03 04 cobra rack) MM Kmember and energy susp motor mounts (which i believe are abt the same height as conv mounts)

I want stainless longtubes. Suggestions? Cost?

Reddevil91 · Jan 29, 2018

What are these spintech mufflers? I’ve seen posts with this brand and another called black widow.

killer5.0 · Jan 29, 2018

Reddevil91 said:
What are these spintech mufflers? I’ve seen posts with this brand and another called black widow.

https://spintechmufflers.com

General karthief · Jan 29, 2018

killer5.0 said:
I want stainless longtubes. Suggestions? Cost?

You want ceramic coated, my stainless headers are rusty looking, 15 years old but rust developed after just a couple years.

Chuckman · Jan 29, 2018

killer5.0 said:
I assume a 2" is tough to fit in the engine bay? 1 7/8? Ill be running a MM steering shaft (for 03 04 cobra rack) MM Kmember and energy susp motor mounts (which i believe are abt the same height as conv mounts)

I want stainless longtubes. Suggestions? Cost?

I've got 2" tubes for the my 427, other than the fact that's its a tall Windsor with raised exhaust ports (nothing a kmember spacer can't fix) they fit pretty well. Check my build thread for pics.

killer5.0 · Jan 29, 2018

karthief said:
You want ceramic coated, my stainless headers are rusty looking, 15 years old but rust developed after just a couple years.

Really? Ceramic like jet hot or generic factory coatings...i had a set of mac ceramics that looked crappy within a few yrs

TOOLOW91 · Jan 29, 2018

Made 740 through 13/4 bbk into 2.5 x pipe and cat back .

I’m sure there was something left
On the table though . This time around it will be 1 7/8 to 3inch collectors and a 3 inch x pipe

cleanLX · Jan 29, 2018

When I was looking at doing a 525ish hp n/a 306 build, someone very knowledgeable(and well known) was recommending 1-3/4" headers min. (1-7/8" if top end was more important) and full 3" exhaust. You're looking to make over 200hp's more, and "forcing" even more atmosphere into the equation.
So, 750-800hp with 1-5/8" headers and 2-1/2" exhaust... doable? Probably. Optimal? Guessing not.

Heard AccuFab is the route to go these days for headers.

General karthief · Jan 29, 2018

killer5.0 said:
Really? Ceramic like jet hot or generic factory coatings...i had a set of mac ceramics that looked crappy within a few yrs

Some coaters do better job than others, I know an old chevy with ceramic headers by jet hot coatings and they look good after 8 years.

Gear grabber · Jan 29, 2018

What size exhaust valve ?

Will This Exhaust Support 750rwhp On A Boosted Motor?

killer5.0

Davedacarpainter

Chicks can make things hard if they’re inspired...

RangerJoe

I leave the horn on while driving

FastDriver

I was uncomfortably high & wearing a helmet

killer5.0

FastDriver

I was uncomfortably high & wearing a helmet

killer5.0

FastDriver

I was uncomfortably high & wearing a helmet

Chuckman

GTFO you fat, heavy bastard

FastDriver

I was uncomfortably high & wearing a helmet

killer5.0

Reddevil91

killer5.0

General karthief

wonder how much it would cost to ship you a pair

Chuckman

GTFO you fat, heavy bastard

killer5.0

TOOLOW91

If you're the village idiot what's that make me?

cleanLX

General karthief

wonder how much it would cost to ship you a pair

Gear grabber

Well-Known Member

Similar threads

Will This Exhaust Support 750rwhp On A Boosted Motor?

Chicks can make things hard if they’re inspired...

I leave the horn on while driving

I was uncomfortably high & wearing a helmet

I was uncomfortably high & wearing a helmet

I was uncomfortably high & wearing a helmet

GTFO you fat, heavy bastard

I was uncomfortably high & wearing a helmet

wonder how much it would cost to ship you a pair

GTFO you fat, heavy bastard

If you're the village idiot what's that make me?

wonder how much it would cost to ship you a pair

Well-Known Member

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