ARH 1-7/8” LT w/hi flow catted x-pipe mod

So this is more of an informational post for folks looking at doing these mods and kinda wanting to know some details.

2008 GT500

Purchased:
ARH 2007-2010 Shelby GT500 1-7/8" Longtube Headers w/3"x2.5" Catted X-Pipe
https://www.lethalperformance.com/arh-2007-gt500-1-7-8-longtube-headers-w-3-x2-5-catted-x-pipe.html
$1,796 shipped

Installation - $900 (somehow i had a bolt sheered off in the head on one of the stock manifolds so they had to remove it.

Dyno Tune - $600

Install and Dyno tune done by same local shop that came highly recommended from JLT themselves.

Dyno Results:

APR 2018 - 556RWHP - 2.5 pulley, JLT cold air intake, JLT tune

May 2019 - 575RWHP@11psi - ARH LT headers and catted x pipe, Bassani axle backs, VMP hi flow elbow port matched with supercharger, VMP twin 72mm TB, REISCHE 170F thermostat, C&R heat exchanger, C&R radiator.

Dyno performed at same shop on same equipment both times. Notice i gained all of 20RWHP. Pretty much the stock supercharger is maxed out and by adding headers i dropped backpressure and thus boost. I COULD run a different lower and probably push up over 600 with the regained boost but ill hold off. I think the smarter choice is to go for larger injectors and a VMP Gen II-R or Gen III. Ive got all the supporting mods for it already so its not like i “wasted” money on the LT headers, i just dont hsve a setup to properly let them stretch their legs. So keep this in mind if you are thinking of doing this upgrade and still running a stock Supercharger.

Sound:

Bassani Axlebacks - FANTASTIC. Nice burble from the exhaust, can still hear the supercharger wine when romping on it. Great sound overall and not annoyingly loud

Bassani Axlebacks, LT Headers & Xpipe - More raspy but at around town speeds and interstate driving, barely louder than the Bassani alone. Totally reasonable to drive. No drone, not loud. Good to go. NOW ... put your foot to the floor and jesus christ, you cant hear the supercharger whine over the loud raspy bwaaaaaaaaaaa. Like, loud enough im probably going to try sticking the stock mufflers back on it to tone it down a bit.




Questions comments concerns welcome. Just wanted to put out some info i know i tried searching for when i was looking at this mod so hopefully this gives some of yall a better idea or more info on your mod plans.

Well written review.

einehund said:

Well written review.

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Thanks, im trying to find a good enough microphone to record the loudness so folks have an idea but regardless, hope this info helps others.

Great review and info.

Agree your maxed out and need more boost to really see the benefit of your LT's. Get a Gen2R and injectors to push 18-19 psi and she will really wake up!

I recently went through a similar modification addition. Was running a 2.40" upper and Posi ported Eaton. Generated 597 RWHP and 564 RWTQ at 14.78 lbs of boost on 18 degree street tune. Hit 609 and 578 on 20.5 degree race tune.

Added ARH LT's w/ catless X pipe and 10% lower. Resulted in 629 RWHP and 613 RWTQ at 17.27 lbs of boost on 18 degree street tune. Assuming 640+ on race tune.

The Eaton is capable of more performance than most give it credit for. Porting the blower and surrounding with sound cooling strategies can bring good results with modest expenditure. One thing that is definitely not modest is the price of adding long tubes! They really help with horsepower maintenance at high RPM levels with the Eaton. But hard to justify the cost when compared with the value and performance of a TVS.

If everything goes according to plan, by this fall Ill be running headers on a (nearly) stock M122 with aggressive cams and higher compression. lol

No, not staying that way. Just building in stages, but will be interested to see how the car responds to higher compression and cams and long tubes with a supercharger thats been largely thrown to the scrap heap.

lexustech48 said:

If everything goes according to plan, by this fall Ill be running headers on a (nearly) stock M122 with aggressive cams and higher compression. lol

No, not staying that way. Just building in stages, but will be interested to see how the car responds to higher compression and cams and long tubes with a supercharger thats been largely thrown to the scrap heap.

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Now that will be interesting to see. I'd imagine you'll see much better gains than I did lol.

Which Borla's do you have installed? S types or the Touring?

850SNCobra said:

Which Borla's do you have installed? S types or the Touring?

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So I screwed up on my post, they are Bassanni's. Editing the post now

lexustech48 said:

If everything goes according to plan, by this fall Ill be running headers on a (nearly) stock M122 with aggressive cams and higher compression. lol

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Looking forward to seeing results with the addition of cams and compression. I strongly considered the can route, but the long tubes used up all my money! I was figuring the cams would result in 40+/- RWHP with the Eaton and good tuning.

Smokinstang65 said:

Now that will be interesting to see. I'd imagine you'll see much better gains than I did lol.

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Possibly, though I question if the M122 has enough huff in it to deliver power with cams that have a lot more overlap that stock.

I do feel better running the M122 first, to make sure the engine mechanicals are happy before any kind of big boy supercharger gets put on there.

Thanks for the write up. It's always good to have real world numbers from the end user instead of numbers that have been "optimized" by the equipment manufacturer.