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Discussion Starter · #1 ·
Hey whats up all? I am a newbiee and bought my 08 RS5.0 (auto) used in June. I have been doing alot of reading on hop up parts for these 2.4 motors and starting making mods to increase power and MPG. In stock trim mine was getting 26.5 avg MPG, never dropped below 24 city driving and got up to 32 hiway. Being an ex-pro mxer team wrench and crew chief for small race car team I did some basic's and wanted to share with others. I first modified the stock airbox, removed the long hose that exits out of the airbox and tossed it, used the snokel that was at the end and connected back to the airbox pointing down inside the fender. thats makes air flow into the airbox little faster and less restrictive. I saw .2 better gas mileage. Next i did a real catback exhaust system (stainless 2.25/2.5") that I paid $150 on ebay, it removes the second cat (AKA: scuba tank) which houses the #2 cat and a resonator. That alone I felt the difference in power, pulls harder with not that much exhaust noise and now I get 27-28 avg mpg and hit 34 mpg on the hiway. This weekend I'm insatalling the OBX Vortex Throttle Body Spacer, it should add more torque (2 HP), its states better MPG, possibly 1-2 or more? who knows but I paid $60 with shipping and if I get 1-2 more MPG. They do work, I have one on my 98 GMC Sub with a 454 I use for towing my race car, I went from 10 to 13 mpg towing, that also includes a K&N CIA and catback exhaust, non towing hiway MPG went to 16.5 from 14mpg if I kepted under 65mph as it crusies at 2k with 3.73 rear gears. I just bought a 4into1 header (ebay $45) ordered the CEL and waiting for that before I install the header. I'll post my findings after that. I'm also considering after market pullies for Alt and AC, anyone install those yet?

Anyone care to share what they have done for low cost to get max performance for little $$? I'm going for easy bolt on stuff.

Eric
 

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Discussion Starter · #2 ·
Update on OBX vortex spacer, it does work, I did notice a hint of more torque on the low end off idle to 1/4 throttle, but the end result after a week of driving is I'm getting solid 34 mpg hi way, with up to 35-36 depending on hi way conditions, like traffic, head winds or drafting a semi truck...hihi. OBX appears to be the lowest costing spacer I've found, but other name brands should work just as well, possibly a tad better but after looking at most of them they seem to be design all the same, its your call, spend approx $60 or others I've seen are around $85 on line.

info below on OBX....the TC fits the 08-10 XB as its same motor, no brackets or fitting issues to worry about, takes about 30 min with simple hand tools. Need to remove wipers, wiper motor, under tray cowling to make easier to access, R&R takes longer than installing spacer :eek:

OBX power flow throttle body spacer installs in between your intake piping and intake manifold. Adding this spacer allows for power increase in the low to midrange for both engine torque and horsepower. The spacer is CNC machined from billet aluminum for accurate fitments. The unique bore design creates a vortex to the air entering the engine. The kit includes everything needed for the install, this spacer is backed by a lifetime warranty against manufacturing defects.

This will fit all:
2004-2009 Scion Tc


http://www.obxracingsports.com/products.php?pk=1496
 

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where did you get it from ??????
 

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You got me thinking about doing some mods I wasn't thinking about doing before. Thanks for the info. Do you have any pics of what you did?
 

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Those throttle body spacers make good sense for engines that have either a carburetor or fuel injection located before the intake runners (our engines have the fuel injection located individually at the end of each runner). The idea of the swirl is to better mix the fuel with the air, however, when the swirled air is delivered into the intake plenum box and from there is split sideways into the individual runners to receive the fuel just as it enters the intake ports, is there really any swirl left to improve uniformity of atomization? A larger plenum can help low end torque and a spacer will probably provide a smidgeon of that effect, but I really wonder about the swirl function on our engines.

Also, an interesting and consistent characteristic of these air swirling spacers is a very audible whistle caused by the vortex forced rotation of the air. Many find that sound objectionable, but I gather others don't (I've read it's a popular sound among V-8 truck owners).
 

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Question

The catback exhaust you ordered from ebay, how does it sound? Is it loud? Is the tone high, or low and deep? I was hoping to get something lower/deeper toned that wasn't too loud. How was the setup as well? I am going to have to get a new down pipe as mine is bent. Long story short, there was a ceiling fan on the highway at night and I ran it over, no time to swerve. Messed up my exhaust components. Sorry, last question, with this catback system, will it still pass emissions tests?

Thanks very much for any feedback!
 

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Throttle body spacers are right up there with the chip you install and get 100 extra horsepower. Not going to happen.
 

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Discussion Starter · #11 ·
As for the catback system, it was Ebay Approx $150
SCION XB 08-09 CATBACK EXHAUST MUFFLER SYSTEM | eBay

that alone mad some mid to top power, maybe 3-5 HP as It did pull harder and the sounds is OK, little deep and not to loud inside the cab

Your XB's come with two cats, one in the stock header, one in the mid muffler under your butt, that uint is a combo of cat and resonator, so removing that resonator does make your exhaust louder, I left mine in. I tried it with stock exhaust and with aftermarket, there is more power going all after market but leave your resonator in unless you get a good muffler installed, like a 22" round 6". The exhaust note with stock rear muffler sounds kinda cool, like a Porsche stock boxer but lower. Yes my header from ebay is doing fine, its a strup copy, being in Calif, I'll have to swap out for stock when it comes time to getting a smog and you have to install the CEL or your throw your engine light, but it did help, you can feel it pull from mid to top RPM cuz its a 4 to 1. Not sure what you guys get for MPG, but I'm avg at 27/28, lowest I've had is 22mpg, best on hiway runs from 32-34mpg @ 65mph, of course this all depends on weather, like head wind, car load, etc. All I did was put the catback on, header, OBX intake spacer, stock AC. I did try a K&N for month, that makes 9hp, when your foot is into it you can feel it, but it's loud, some of you younger dudes may like it, if you roll on your throttle its OK. IWith all the mods I dragged race some stock XB2's, I pulled away but not run away from them. I am not using it, they cost $321, I'm selling for $200

email me at [email protected]

The OBX spacer does make little whistle sound, but its very lite. For you that doubt what I say, I'm auto teach for over 25 yrs, currently on a race team in SCCA for GT1 class. Prior was Factory Suzuki and Honda race tech for support riders.
 

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As already pointed out, don't expect any performance mod to assist MPG. Performance mods assist performance, but with ECU controlled engines, when exercised, you pay in terms of MPG. MPG depends on the driver, not the mods.
 
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