Cut-outs !

Captainsilverback · 03-17-2008, 07:41 PM

anyone ever did cut-outs on a FD? is it possible?

a7xh7 · 03-17-2008, 10:28 PM

are u talking about using a hole saw to cut the rear bumper and venting the front to get air flowing to different things

85rx-7gsl-se · 03-17-2008, 10:31 PM

I assumed he was referring to exhaust cutouts?

a7xh7 · 03-18-2008, 02:04 AM

or santa shapes

SLOASFK · 03-18-2008, 04:23 AM

given the tempermental nature of the FD, I don't think I'd want to risk instantly losing all back pressure in the exhaust at WOT.

ObliqueFD · 03-18-2008, 10:37 AM

Isn't back pressure a bad thing on turbocharged cars?

RXtacy · 03-18-2008, 11:05 AM

Quote:

Originally Posted by ObliqueFD

Isn't back pressure a bad thing on turbocharged cars?

In general yes, but if you have your boost at a set value with a given back pressure and all of a sudden that back pressure goes away... Well you overboost like crazy and your motor will probably not be in great shape afterwards.

busted7 · 03-18-2008, 12:02 PM

To add the the above comment: You would need to tune for open cut out and also closed cut out. I guess it could be done but the only reason i can imagin would be if your in a state were you have to maintain stock exhaust but want performance at the switch. If you state your goals it would help!

Signal 2 · 08-05-2011, 04:01 PM

Quote:

Originally Posted by busted7

....the only reason i can imagin would be if your in a state were you have to maintain stock exhaust but want performance at the switch....

^Agreed. Regardless, anyone comtemplating should understand that many States...probably most, have statutes outlawing exhaust cut-outs. In my State they aren't widely enforced anymore, especially with the Hot-rod's growth in popularity the last few years. But the statute is still there. And if a State has visual inspection, a cut-out is hard to hide.

ledgebmx · 08-06-2011, 07:28 AM

Here in NC one of the cars I used to work on had a 3" cutout on a 20b FD. The owner did it for performance, cost and noise reasons. It's expensive to purchase/fab a 4-5" exhaust that is quiet enough to pass noise laws but the 3" exhaust restricted the potential of the engine. He gained around 80rwhp with the cutout open at WOT. I think he dyno'd ~650rwhp @ 17psi all said and done.

I think the biggest factors are exhaust restriction and tuning issues. I would imagine you would tune with the cutout open and just deal with not racing with it closed very often. It's possible to tune for both if you're not running an exhaust that's too small (IE 3" on a 20B). You'd have to keep an eye on the tune but that's a given with these cars!

cewrx7r1 · 08-06-2011, 11:10 PM

Some production sports cars now come with some form of exhaust bypass that open at full throttle. Ferrari and Corvette are two that use them.

RXTASY · 08-07-2011, 05:15 PM

Have a 3" Quicktime cutout on my exhaust.
One of the best mods I have ever done.
Turbo spools quicker and boosts a little higher, plus it sounds wicked as hell!

03-17-2008, 07:41 PM	#1
Captainsilverback The Newbie Join Date: Feb 2008 Location: Tennessee Posts: 2 Rep Power: 0	Cut-outs ! anyone ever did cut-outs on a FD? is it possible?

03-17-2008, 10:28 PM	#2
a7xh7 Rotary Fan in Training Join Date: Mar 2008 Posts: 88 Rep Power: 0	are u talking about using a hole saw to cut the rear bumper and venting the front to get air flowing to different things __________________ "sevens_ix"

03-18-2008, 02:04 AM	#4
a7xh7 Rotary Fan in Training Join Date: Mar 2008 Posts: 88 Rep Power: 0	or santa shapes __________________ "sevens_ix"

08-06-2011, 07:28 AM	#10
ledgebmx The Newbie Join Date: Nov 2010 Posts: 10 Rep Power: 0	Here in NC one of the cars I used to work on had a 3" cutout on a 20b FD. The owner did it for performance, cost and noise reasons. It's expensive to purchase/fab a 4-5" exhaust that is quiet enough to pass noise laws but the 3" exhaust restricted the potential of the engine. He gained around 80rwhp with the cutout open at WOT. I think he dyno'd ~650rwhp @ 17psi all said and done. I think the biggest factors are exhaust restriction and tuning issues. I would imagine you would tune with the cutout open and just deal with not racing with it closed very often. It's possible to tune for both if you're not running an exhaust that's too small (IE 3" on a 20B). You'd have to keep an eye on the tune but that's a given with these cars! __________________ Aaron - Auto to manual conversion 93 w/ large streetport, RA Super Seals, GT35R, 1000/1680, AEM EMS, direct-fire AEM smartcoils, M2 Large, Aux inj, Tein Flex, Powerflex, CCW Classics - 18x10's, 99 spec and more. I'll make a build thread soon... Last edited by ledgebmx; 08-06-2011 at 08:56 AM.

08-07-2011, 05:15 PM	#12
RXTASY idahorotary.com Join Date: Mar 2010 Location: Idaho Posts: 135 Rep Power: 16	Have a 3" Quicktime cutout on my exhaust. One of the best mods I have ever done. Turbo spools quicker and boosts a little higher, plus it sounds wicked as hell! __________________ 87 TII-E85-600+ RWHP and climbing Life starts at 2 bar! Come visit my forum! idahorotary.com http://idahorotary.com/smf/index.php

03-18-2008, 04:23 AM	#5
SLOASFK Rotary Fanatic Join Date: Feb 2008 Location: Lancaster, PA Posts: 155 Rep Power: 18	given the tempermental nature of the FD, I don't think I'd want to risk instantly losing all back pressure in the exhaust at WOT.

03-18-2008, 10:37 AM	#6
ObliqueFD Rotary Fan in Training Join Date: Feb 2008 Location: Lancaster, Ohio Posts: 53 Rep Power: 18	Isn't back pressure a bad thing on turbocharged cars?

03-18-2008, 12:02 PM	#8
busted7 Rotary Fan in Training Join Date: Mar 2008 Posts: 55 Rep Power: 18	To add the the above comment: You would need to tune for open cut out and also closed cut out. I guess it could be done but the only reason i can imagin would be if your in a state were you have to maintain stock exhaust but want performance at the switch. If you state your goals it would help!

08-06-2011, 11:10 PM	#11
cewrx7r1 The Judge Join Date: Feb 2008 Posts: 196 Rep Power: 18	Some production sports cars now come with some form of exhaust bypass that open at full throttle. Ferrari and Corvette are two that use them.