Limits of stock exhaust and current injectors

crim5.0n

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I'm currently running the following mods:

-VMP Gen 2 Stage 2 kit (56# injectors, bap, 82mm pulley)
-Initial tune that shipped with the kit from VMP
-Billet OPG and crank gear
-Whiteline LCAs
-GT500 axleback

I don't have a boost gauge but I am assuming by car is roughly 10psi. I'm wondering at what point the stock exhaust is going to be a major restriction or if it is dangerous to run the stock exhaust at a certain point if there is too much pressure and at what point I'd need to upgrade injectors. I run 93 octane (E10), will never do E85 or full on race gas (octane booster MAYBE but doubtful)

When the supercharger was installed Rev Auto ran it on the dyno for me and it made 562/485. I'm thinking I can pay for a re-tune and make close to if not more than 600/500, but I am considering other upgrades to keep the car safe on the stock engine.

I don't have any plans to go over 650rwhp, I want this thing to last on the stock engine for a long time.
 

Sky Render

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Others with more forced induction knowledge can chime in here, but I do know that:

1. LT headers will produce gains on a FI car.
2. Chambered mufflers will balloon and fail with FI (I'm surprised yours have still held up).
3. Off road pipes will show a gain with FI, and cats will often clog/fail.
 

Gruca

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Others with more forced induction knowledge can chime in here, but I do know that:

1. LT headers will produce gains on a FI car.
2. Chambered mufflers will balloon and fail with FI (I'm surprised yours have still held up).
3. Off road pipes will show a gain with FI, and cats will often clog/fail.

I've never heard #2 before. Seems odd since GT500s are FI and have...GT500 mufflers on them.

Not disagreeing, just wondering as I have them on my car and my Paxton install finished up yesterday.
 

travelers

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I've had the GT500 mufflers on mine for 3 years and with my 2.3 whipple for 2 years and they are fine. I'm not in boost a lot.
 

noldevin

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I've also never heard of any mufflers failing on a coyote due to power, ever.
There are gains to be had from exhaust mods, your efficiency will improve (more power per psi, which is healthier for the engine that trying to cram more boost in)
You may eventually cook the stock cats.

As for injectors, I would ask your tuner what they would prefer to use for your goals. Always use the injector your tuner prefers.
 

Sky Render

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There are some threads over in chit chat about chambered mufflers expanding at higher boost levels. I'm not sure which brands they were, though.

EDIT:

http://www.s197forum.com/forum/showthread.php?t=88407

The issue might have been using a WOT box with a chambered muffler, not simply boost.

temporary-47.jpg
 
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46addict

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The DOB recipe for 700whp on a Coyote called for 3" catless exhaust with straight through mufflers. Longtubes were also required but it didn't state what size. I would guess at least 1 7/8".

I can see the stock exhaust being a bottle neck beyond 600wheel but I can't imagine it making things unsafe for the engine. The point of opening up the exhaust is to reduce boost pressure so you can achieve a certain power goal without overspinning the blower. The stock cats will survive if there are protection strategies in the tune to keep them from getting too hot, passing too much fuel, etc.
 

skaarlaj

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I've had the GT500 mufflers on mine for 3 years and with my 2.3 whipple for 2 years and they are fine. I'm not in boost a lot.
Are GT500 mufflers chambered? I'd guess they aren't.
 

skaarlaj

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I'm currently running the following mods:

-VMP Gen 2 Stage 2 kit (56# injectors, bap, 82mm pulley)
-Initial tune that shipped with the kit from VMP
-Billet OPG and crank gear
-Whiteline LCAs
-GT500 axleback

I don't have a boost gauge but I am assuming by car is roughly 10psi. I'm wondering at what point the stock exhaust is going to be a major restriction or if it is dangerous to run the stock exhaust at a certain point if there is too much pressure and at what point I'd need to upgrade injectors. I run 93 octane (E10), will never do E85 or full on race gas (octane booster MAYBE but doubtful)

When the supercharger was installed Rev Auto ran it on the dyno for me and it made 562/485. I'm thinking I can pay for a re-tune and make close to if not more than 600/500, but I am considering other upgrades to keep the car safe on the stock engine.

I don't have any plans to go over 650rwhp, I want this thing to last on the stock engine for a long time.

I'd say long-tubes and a cat-less set-up would be alot easier on a stock bottom Coyote engine that you're trying to get 650rwhp from rather than adding boost, and tuning to try for the same number with stock manifolds, and factory "catted" mid-pipe. I'd also venture to say this becoming more and more relevant as the HP numbers increase with most or nearly any engine.
 

07gts197

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There are some threads over in chit chat about chambered mufflers expanding at higher boost levels. I'm not sure which brands they were, though.

EDIT:

http://www.s197forum.com/forum/showthread.php?t=88407

The issue might have been using a WOT box with a chambered muffler, not simply boost.

temporary-47.jpg

Theres a thread on another forum of a member that blew a hole in his mufflers from using a wot box. I dont remember if he was boosted but I assume so. Also this was a stock block 2v so he couldnt have been pushing too much boost.
 

noldevin

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Yeah I could see a 2step or excessive backfiring causing the muffler damage, but not just pure power.
 

crim5.0n

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I am looking to stay within the 600-635rwhp range, right on the initial. I *think* it's possible to hit that on my current setup with a tune revision and maybe fuel injectors if necessary. Definitely want to keep it safe though. I messed around with the exhaust on my LS1 T/A a bunch and I'd like to avoid that on this build.
 

07gts197

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Yea thats what I think the problem was. But I think the baffles will go too in certain mufflers because of back pressure.
 

RED09GT

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With boost, I would just do the mid pipe.
You get 90% of the power of switching to longtubes with 10% of the headaches and a lot lower cost.
 

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