Doug Thorley shorty performance gains.

[sidneyhop]

Curious what kind of sincere performance gains can be realized by installing the DT shorty headers?

My exhaust manifold is loud as hell with a crack and Ill be needing to install these asap. Close to 2k is a hard pill just because of an annoying exhaust so needing to justify them with torque and HP gains as well

 

[MADUFF3]

Sorry, there may be small gains but there are no giant gains in exhaust as a rule (generally). I know the overlord shaped his and did an extensive high flow cats custom everything and did not gain anything notable. I would like to change mine out too, more for avoidance of the manifold crack and weight really but it is as you said tough to justify... I'd do it for the lasting durability and fix to a known failure... if you replace the manifold with stock likely you will have a failure again in te to the same issue,cracks...

 

[Rednexus]

DT headers are the best performance mod you can do for a 2UZ (short of supercharging it....). I have LT's and the performance gains in the midrange were immediate and noticeable. It "felt" like a 20-30 HP increase and my GX "put me back in the seat" a lot more after the upgrade. Note that I'm not sure the "peak" horsepower or torque changed that much, it was mainly the difference when punching the throttle from 3,000-4,500 RPM or so. I left the rest of the exhaust 100% stock (Y-pipe and catback), but may eventually put on an aFe catback. The OEM manifolds on these engines are really restrictive. I could not believe how poorly-designed they were in regards to flow and size when I took them off (and cut off the cats to sell). It's sad that Toyota designed such a crummy exhaust manifold for an engine that is otherwise a work of art.

There are some dyno runs out there for these headers and they seem to support the +20 HP gains, and both show the midrange gains as well:

DT Headers Dyno Result Thread

DT Headers Dyno Result Thread (Numbers are in) This is the baseline dyno run for the DT headers Install. We are scheduled to make the followup run 9/8. Headers will be installed 9/2 and I will attempt to put some break in mileage on them before the second run. The Mileage figures represent...

forum.ih8mud.com

Toyota-4Runner.org

The Largest 4Runner Community in the World

www.toyota-4runner.org

 

[sidneyhop]

DT headers are the best performance mod you can do for a 2UZ (short of supercharging it....). I have LT's and the performance gains in the midrange were immediate and noticeable. It "felt" like a 20-30 HP increase and my GX "put me back in the seat" a lot more after the upgrade. Note that I'm not sure the "peak" horsepower or torque changed that much, it was mainly the difference when punching the throttle from 3,000-4,500 RPM or so. I left the rest of the exhaust 100% stock (Y-pipe and catback), but may eventually put on an aFe catback. The OEM manifolds on these engines are really restrictive. I could not believe how poorly-designed they were in regards to flow and size when I took them off (and cut off the cats to sell). It's sad that Toyota designed such a crummy exhaust manifold for an engine that is otherwise a work of art.

There are some dyno runs out there for these headers and they seem to support the +20 HP gains, and both show the midrange gains as well:

DT Headers Dyno Result Thread

DT Headers Dyno Result Thread (Numbers are in) This is the baseline dyno run for the DT headers Install. We are scheduled to make the followup run 9/8. Headers will be installed 9/2 and I will attempt to put some break in mileage on them before the second run. The Mileage figures represent...

forum.ih8mud.com

Toyota-4Runner.org

The Largest 4Runner Community in the World

www.toyota-4runner.org

Thanks for the linked info. Ive read LT headers will generate the most return. I wanted to keep the cats so went with the ST. Curious how much of a difference there is between the two.

 

[MADUFF3]

I see that and hear the it "feels like" I get it, especially when something is upgraded everything seems to work better. Here is a thread from GX OR where the Overlord himself spared no expence with DT headers, race, high flow cats and full exhaust ment to give the most....he had it dyno'd before and after...

Just my .02, I I tend to do them at some point t but ease your disappointment it will not revolutionize power production, but they will solve your Crack and sound great.

 

[Rednexus]

I see that and hear the it "feels like" I get it, especially when something is upgraded everything seems to work better. Here is a thread from GX OR where the Overlord himself spared no expence with DT headers, race, high flow cats and full exhaust ment to give the most....he had it dyno'd before and after...

Just my .02, I I tend to do them at some point t but ease your disappointment it will not revolutionize power production, but they will solve your Crack and sound great.

Performance gains from headers are well-documented for the 2UZ engine across multiple platforms (Tundra, 100 series, T4R, etc). Others on this forum have also had a similar experience as myself. Headers are also one of the oldest hot-rodding tricks in the books for V8 engines in general and Toyotas are no exception. The log-style OEM manifolds are just a really poor design, are very restrictive, and don't allow for any sort of scavenging of exhaust gasses like a set of tri-Y headers will. I can only presume they are an emissions-related design to get heat to the cats ASAP.

Will headers "revolutionize" your engine - absolutely not - but 20-30 HP is a bolt-on 10% gain for these engines and can easily be felt/noticed. Short of adding a supercharger, there is no other mod for these engines that can be bolted on and provide these power gains.

 

[sidneyhop]

Got the GX back and notice a little more pep. Nothing crazy or tire squawking but still theres something. Also the exhaust leak sound is gone....which is the other main reason for getting them.

 

[sidneyhop]

Follow up on gas mileage. Appears to have gone down 2 mpg.

 

[NCgamecock]

Let me start by saying: I'm not an exhaust expert! But I do work for a global auto OEM.
So, for those that say what was Toyota thinking when they designed these sucky headers?! I wanted to add: Toyota (& all OEMs) have many different goals/targets to meet for their products. They have to take into account global emissions & fuel economy standards, noise requirements, cost, ease of assembly, & many more. Clearly, they missed the mark on durability of our headers (mine are currently clicking lightly...)! But they weren't designing a race car...so, horsepower is only one piece of the puzzle, & I'd imagine they decided to focus on other areas.

 

[jiggletits]

Let me start by saying: I'm not an exhaust expert! But I do work for a global auto OEM.
So, for those that say what was Toyota thinking when they designed these sucky headers?! I wanted to add: Toyota (& all OEMs) have many different goals/targets to meet for their products. They have to take into account global emissions & fuel economy standards, noise requirements, cost, ease of assembly, & many more. Clearly, they missed the mark on durability of our headers (mine are currently clicking lightly...)! But they weren't designing a race car...so, horsepower is only one piece of the puzzle, & I'd imagine they decided to focus on other areas.

+1

Also, replacing an exhaust manifold here and there is nothing compared to the crap I have dealt with on American trucks. When people complain about fixing Toyotas I just want to laugh at them. On average, Toyotas have very few, if any major problems..... sit in your Toyota and hold my beer while I go crack a transmission in half 3 times in 30k miles on a stock, unloaded Superduty due to how f'n poorly the drivetrain was designed. One bad u-joint or slip yoke and about 30 seconds of highway driving after that "thump" starts... Been there done that f'ck that.

 

[Rednexus]

Let me start by saying: I'm not an exhaust expert! But I do work for a global auto OEM.
So, for those that say what was Toyota thinking when they designed these sucky headers?! I wanted to add: Toyota (& all OEMs) have many different goals/targets to meet for their products. They have to take into account global emissions & fuel economy standards, noise requirements, cost, ease of assembly, & many more. Clearly, they missed the mark on durability of our headers (mine are currently clicking lightly...)! But they weren't designing a race car...so, horsepower is only one piece of the puzzle, & I'd imagine they decided to focus on other areas.

I'm a design engineer by trade . The 2UZ is brilliant in many ways, other than the starter under the intake and the exhaust manifolds. All designs are limited by design budget and schedule, as well as the talent of the design team. For whatever reason, the 2UZ manifolds came out half baked, and it's unfortunately a expensive and difficult fix for us GX owners 15 years later. It seems that this could have been avoided with some thicker steel at a nominal extra cost. Regardless of the constraints that led Toyota to that particular manifold design, it is still a bad design in terms of reliability and power. However, it does provide an opportunity to greatly improve the 2UZ by adding aftermarket headers.

To put the headers in further perspective, it took me less time and the same amount of money to replace the head gaskets and piston rings in my previous Subaru than to get a pair of headers on my GX. I love the mod and knew I'd be doing headers when i bought the GX, but the difficultly eclipses more major repairs on other vehicles. Luckily it just needs to be done once.

 

[GXO]

I got around 20 awhp and 40awtq from long tubes and the exhaust I did.

 

[DRANGED]

Reviving this as I'm midway through my ST install.
@sidneyhop Did you do the wrenching yourself or go to a shop. If self, did you retain studs and nuts or install with bolts? If shop did they give you any of the story of their install experience? Did you have any clearance issues with the steering to the driver's side header? Did you reuse motor mounts or go new there 'while you're in there'?

THanks,
-MW-