Power wise; barely noticeable with ST’s.
Also 03-04 and 05+ have different manifolds and mid pipes.
Also 03-04 and 05+ have different manifolds and mid pipes.
Dorman Manifolds (2 Viewers)
- Thread starter eseel
- Start date
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I noticed significantly more power on my 2007 with LT headers. Made a very big difference in the "butt dyno". My GX has plenty of power with the LT's and an aFe cold air intake (with the vast majority of the gains coming from the LT headers). Not only do the OEM manifolds crack, they are crazy-restrictive when you compare them to the headers - they really choke up the 2UZ.
As mentioned previously - I'd only go with LT's if you are 100% sure you aren't going to have to deal with intrusive emissions inspections, either now or in the future. Living down here in the Ozarks I fall into that bucket, but many folks do not. Otherwise, get the ST's and keep you cats.
As mentioned previously - I'd only go with LT's if you are 100% sure you aren't going to have to deal with intrusive emissions inspections, either now or in the future. Living down here in the Ozarks I fall into that bucket, but many folks do not. Otherwise, get the ST's and keep you cats.
LT terminate in a flange which bolts up to stock flange upstream of 2nd cat. To retain 1st cats to LT headers (or welding a flange to cat and bolting up to LT) you'll end up doing custom downstream of header replacing the Y-pipe to get 2 cats on each side before the Y-junction going into the single exhaust. At that point, might as well go full custom with twin pipes, each side has its 2 cats, resonator and muffler, or aftermarket with appropriate cats and muffler(s).
The LT bolt up to the stock downstream flanges overriding the 1st cats.
LT are 4:2, 2:1 collectors
View attachment 3124263
The ST get stock 1st cats welded to them, but this is a fiddly process.
Unbolt engine from mounts and jack up, remove manifold and cut top of cats off per DT instructions, loosely fit header to block and lower onto mounts, mock cat to header and align downstream flange (repeat previous as needed to get proper alignment of cat to header in situ), tack cat to header, remove header and cat, fully weld cat to header, replace header with cat to block and bolt up, lower engine and bolt up mounts, bolt it all together.
ST are 4:1 collectors.
View attachment 3124264
Pics from DT instructions (linked above) showing location of cut to be made removing cat from manifold tube and cat welded to ST's open pipe
View attachment 3124312View attachment 3124308
View attachment 3124297View attachment 3124289
The flange downstream of the 1st cats downstream of the manifold bolt up to the flanges in pic above right.
Each side is: block, manifold, bend, cat, flange;
driver goes pipe/bend, cat, bend, tube, bend, flange to Y-pipe collector;
passenger goes pipe/bend, cat, tube with Y-collector from driver, then flange;
then pipe, muffler, bend, flange, pipe, bends, resonator, pipe, tip.
Sadly, I haven't been able to find a singular diagram showing all this as is laid out in the truck...
Not meaning to hijack this into a DT header convo. I just wanted to share my stock manifold experience, but we know how snowballing repairs-come-mods work.
The ST details here were eyeopening - much appreciated (what a headache!)....and my fault for the DT topic change as well but hopefully the OP also gets some value out of this extra detail from the DT side of things.
I’d still do the ST’s again to avoid the ticking sound that is so common. ST’s are a long term fix that work reliably with OBD. Don’t expect a big power bump. ~20 HP on 5,000 lbs of steel tires and flesh is nothing.
How about torque gains?
You said exactly what I'm aiming for, "long term fix" from restrictive stock manifold tube, prone to failure.
Tha ks for your experience with the ST. I'd kind of. Lime to see a mud call out in DT owners.
Maybe this'll spark a new thread to Collect those experiences and differing presentations/mods upstream and downstream of headers, and the stockers plus headers (me).
Like I said, power wasn’t that noticeable, 20 HP is a guess.
Plenty of threads out there already. I’ve only seen dyno work on LT’s though. LT’s seem like they would be more noticeable but neither is going to make it ‘fast’. If speed is a goal, the GX is the wrong platform.
Plenty of threads out there already. I’ve only seen dyno work on LT’s though. LT’s seem like they would be more noticeable but neither is going to make it ‘fast’. If speed is a goal, the GX is the wrong platform.
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yeah copy that. HP and speed isn't the forte, that's why I'm curious about torque gains.
And you're right. I'll just need to do some of the legwork in summarizing dyno threads, though i hear you, most are likely LT also where the gains are maximized.
My perspective remains: fix the cracking problem for le$$ than OE and dealer co$t, and if there's another positive in the form of power/torque or -gasp- MPG, any of that is just bonus for rectifying a least common denominator design.
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The big benefit I saw from the LT's was midrange torque - like 2,500 RPM to 4,000 RPM or so. It made a pretty noticeable difference for my GX. Given that mine spends more time towing our camper than off-roading, the midrange torque gains are quite helpful.
I agree that HP gains are not that meaningful - my GX spends very little time at 4,500 RPM and higher.
I agree that HP gains are not that meaningful - my GX spends very little time at 4,500 RPM and higher.
Did anyone have to do a tune once they installed the ST or LT headers? Is it needed? Recommended? If so, what's the easiest way going about getting a solid tune without spending $1000 on a dyno run and custom tune?
There is no way to tune an 03-04 without a piggy back ECU presently. VFTuner does offer tunes to vvti 05-09. Tuning with a long tube and full exhaust would be worth it.
I have an 03 with LT, GESi HO cats (vibrant), a full pie cut SS exhaust that is 3" all the way and a performance muffler (vibrant) with a J-tube for highway drone reduction.
I also dyno'd the GX before and after the change. My results:
- You get more awhp and awtq with the headers
- You get WAY more with an open exhaust. The OEM exhaust Y pipe and other restrictions are criminal.
- You also get everyone thinking they know more than what you have in your own garage which is funny.
Directly from the dyno tech: torque gain at 3000rpm went from 229ftlbs to 274ftlbs, and at 3500rpm went from 234 to 275
I'd love to tune mine, or find someone who has actual experience tuning the VVTI 2UZ. The VFTuner site looks a bit sketchy to me. One guy over on the 100-series Land Cruiser forum installed a MAPECU piggyback on his VVTI 2UZ with promising results, but it would still require a dyno run to fully tune.
Did you lose any low-end torque, like 2,500 rpm and below, with the exhaust and Y-pipe? My Y-pipe is getting a bit ragged despite my efforts to patch it - a DT Y-pipe with some cats grafted in would be nice to complement my headers, but I've read other threads indicating a loss of low-end torque when the exhaust is opened up.
No losses at all...pulls like a tractor.
A little bummed to hear how choked the stock Y is, but it is what it is.
My driver side exhaust gave up the ghost this weekend, so my issue is forced.
(Looking down @ manifold- cat-mani weld fail from engine bay,. Driver a side)
Going for basic DT install: remove bits, cut top of cats, fit to headers, tack, bench weld, install.
Need more tools, flange studs are external torx, need e-torx socket (8mm?)
My driver side exhaust gave up the ghost this weekend, so my issue is forced.
(Looking down @ manifold- cat-mani weld fail from engine bay,. Driver a side)
Going for basic DT install: remove bits, cut top of cats, fit to headers, tack, bench weld, install.
Need more tools, flange studs are external torx, need e-torx socket (8mm?)
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I have pre and post OEM O2 sensors and a 90 defouler on the downstream O2s. That's it. I pop an occasional O2 code but just reset it on the move with my OBD fusion app. If I run ethanol free I don't get codes.
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Most of your studs will probably come out as more of a bolt. If a stud does stay in I would probably re-use it. The etorx fastener is kind os small/weak and stripped whem I tried to use it to pull mine.
I really think you have a broken powertrain mount somewhere. The OEM manifolds really shouldn't beeak like that unless there is flex in the system that is not supposed to be there.
I agree. Having seen my motor mounts when I did the RCLT and 200 series rack upgrade and having to replace them you should for sure suspect them haha.
