Hey all,

I managed to lay my hands on some 4-1 headers and before I go slapping them on I wanted to know if its worth it.

Seeing as it's 5AT, it could really do with the lower end boost that a set of 4-2-1 headers would give.

Has anyone got an N.A. Tez running 4-1 headers? (either tansmission)

Are the gains noticeable from mid to upper or just upper revs?

Cheers

ive just put on a set of fgk 4-1 headers and yeah they work well when its at higher rpm but have way less bottom end power. i run a 2.5" strait thru exhaust with only a trust can at the back tho so that probly doesnt help my low end power output.

..and I'm interested because I bought a pair of twin SUs for the daughter's KE70 and they came with a 4 into 1 extractor set.

I want more power under 5000rpm, so I'm be looking at a high-lift short duration cam, and I was wondering if there was much difference in the headers...

Cheers Macca,

So are you saying you've lost power in the low end with the 4-1 compared to stock?

yes ive lost low end power. :( but i also have other factors aswell that might be adding to my [f**k] all low end power output. ive got a blitz pod setup and my exhaust is totally strait thru 2.5" :wacko: unrestrictive so i have no back pressure pretty much. ive got a apexi power fc that im puttn in and getting it tuned in the next few weeks , that should solve the problem and give me the power gain. :lol: hope this may help.


mines a 6 speed manual, dunno how or if it will affect a auto one.

Ah right - possibly the pod setup in your case but all info is valid :) Cheers for the feedback dude.

I've recently gone back to the factory airbox and there was a definite improvement at lower revs

Alimac, are you running headers? If so what type?

What did those headers set you back, and where did you get them from?

they are Fujitsubo Giken (FGK) stainless headers, they cost me 6 hundy (the higher end of what they are worth) and i got them off another member. whys that? there is a aftermarket set of 4-2-1 headers on trademe for a sxe10 altezza for $550. dunno what brand, if you were looking for a set.

I was running HKS 4-1 headers on my white tezza, didn't lose any low or mid range (also didn't gain much, if any) but gained a hell of a lot more top end. That and my 2.5" exhaust were the only engine/exhaust mods so factory air box etc. Gave me a 20-25kw gain over standard at 8000rpm.

If you want more low and mid range you're better of with 4-2-1's

Legend thanks senza, exactly the type of info I was after.

It's very tempting just to whack these ones in and be done seeing as they are there and all but at the same time I only want to do it once and do it right.

I had a garage booked to chuck the headers in tomorrow too :(

On that note, I'm curious to know if anyone on the forums has a set of 4-2-1 headers they'd consider swapping for an HKS 4-1 set?

or get a aftermarket ecu and tune it for mid range.

haha, affordability is key at the moment. One mod at a time.

Also remember the 5AT has 2 O2 sensors grouped to pairs of ports, does your set of 4-1 Headers have 2 O2 sensor bungs or just one?

Just the one on the HKS headers. Is there a work around?

Didn't know about it until you mentioned it, appreciate the heads up - tis a new roadblock though :)

I'm guessing this is usually an issue when putting headers on a 5AT?

Could you splice in a second set off the first sensor plug - would that work?

Does this differ at all if it were a 4-2-1 set - do they come with 2 sensors?

You could just get a 2nd bung welded on but remember on the stock headers each O2 sensor does a group of 2 cylinders. Not sure if you'd run into any issues with them just reading the same exhaust gas from all the cylinders, unfortunately without 4-2-1 headers there is no way to group them properly, you could try welding in balance pipes (to simlulate 4-2-1 grouping) and installing the O2 sensors on the balance pipes.

Food for thought anyway :D

Oops edited the post above - so 4-2-1 headers have 2 sensors?

They all say that they're only made for the 6 speed models, as the manual versions only have one oxy sensor, which is down stream from the 4-2-1 section of the standard pipe.

If you got an aftermarket set of 4-2-1, it would be unlikely that it would have oxy sensor fittings for the auto version of the car, as their oxy sensor setup is different.

Cheers roman, spot on - just the one unfortunately.

Surely I can't be the only person to want headers in an auto?

Anyone else worked a solution!?

Even with 4-2-1 setup, aftermarket manifolds are generally aimed at higher rpm band, which isnt overly going to suit an auto in my opinion.

If you want to retain low/medium rpm power then factory setup is probably your best bet.

Looking at dyno results registry, there's a good 10-20wkw to be made just by switching to a manual gearbox, no point in spending $$$$ on an exhaust manifold to gain back 5kw, and still be 15kw behind a manual setup.

I'd wager that this is why not many people have overly modifed the auto cars, better at cruisers than zinging out loads of performance.

Supercharge it! hahaha.

You dont compromise fuel/ignition in one area to suit another, when running an ECU...

Ideally you tune it well for every rpm range!

It's the physical parts that alter what rpm range things start happening in.

Hmm sombre reality really.

So header-wise, there's no way to play with the headers/sensors to suit an auto?

Just because I'm behind the curve being auto, I still want to do what I can to eek some performance out of it.

Also manual conversions run roughly $2k+ right?

I think you'll find the manual engine makes 10hp more than the auto from factory so that'll account for most of the difference you're seeing between the two.
Converting an auto to manual will gain you power at the wheels especially using a solid lightened flywheel but you'll always be 10hp behind a factory manual.

Cheers E910,

I'm fine with it being an auto at this stage. I want to look at other initial options before going down the manual conversion road.

If I lay my hands on some 4-2-1s, and depending on where the O2 sensor is, have another drilled & tapped for the stock sensors..

Can anyone see why this wouldn't work?

Yep, but my 200hp single VVTI beams motor when running through a 5 speed transaxle was making more HP at the wheels than the 210hp 6 speed Altezzas on the same dyno, same day...

Transmission losses through a front/rear setup and an auto box are a bit of a killer, as the dyno results show. 6 speed box with front engine RWD setup has more transmission losses than a transaxle, but still a noticable amount less than an automatic transmission.

Does the auto altezza have the cat converters in the exhaust manifold?

You could convert to the 4-2-1 from a 6 speed version and weld in a bolt for oxy sensors, might give a bit more punch for cheap?

Hmmm anyone got a pic of the 4-2-1 from the auto?

Might be more midrange oriented...

It's more critical to have a good spread of torque for an auto, because as a general rule the gaps between gear ratios are larger. 5 speed trans might be alright though I guess, I've never driven one.

It has 2 pre-cats as part of the y-pipe with the sensors in front of the pre-cats, then flows into a cat from there as far as I can tell. Could be wrong though :huh:

From the get go, I didn't realize the manual/auto differed in the headers/O2 sensors so it's a bit of a curve ball, obviously didn't talk to enough people before I bought em :/

Do you mean the stock ones? Or ones someone out there has modified?

I think the idea with twin oxy sensors in auto, is just to get them before the cat converters...

And cat converters closer to the head, for better emissions.

If you put the twin oxy sensors after the 4-1 section of your manifold, I reckon it would be sweet so long as the wires reach.

Otherwise, could/should be gains going to standard 4-2-1 from 6 speed, and welding oxy sensor mounting bolts in.

It might just be the Y pipe that's different, between auto/manual, will check EPC later...

Appreciate the input, cheers roman!

Currently the HKS 4-1 headers I have, the current sensor lead is about 1m long.. and its about 20mm after the 4-1 condenser, past the slight bend in the pipe.

Its a toss up whether I sell the 4-1's and grab some 4-2-1's or just go with the 4-1's.

After that, I'll see what I can jig with the O2 sensors.

Hey,

Not sure if you have seen it but there is a group buy and some information on headers for the 3sge auto as well as the manual (link below). It has a diagram and some pics of the headers. Maybe you can use the info to mod yours or sell em and join the GB? :D

http://z4.invisionfree.com/lexusaltezzaclu...?showtopic=8973

Cheers

Legend thanks Mica, dunno how I missed that!

What about just splicing the two O2 sensor wiring looms together so they read from the same sensor?

Yea that's what I thought about too but I don't know what the downstream affects are for the auto. There must be a reason why the auto's have 2 and the Manual has one... probably linked to the 2 cats or Pre-cats that the autos have vs the manuals having only one (I think)

Probably not the best idea, because soldering/crimping the wire to oxy sensors isnt good if you can help it, and makes it harder to return to stock, if you need to at some point.

Would be better off making twin holes for the oxy sensors, in my opinion.

Cheers for all the input guys, much appreciated!

Am going a different route now and buying a set of headers with the holes/taps already there for the sensors.

HKS 4-1 headers anyone?

Hi there silent one

I have been following this for a while and finally had a look under the bonet last night of our 5AT (forgot to take a photo :( )
We have a set of unwraped 4-2-1's . The sensors are mounted in the top of the joint of each where 4 becomes 2. Will try to remember to take a photo tonight.
If you make it over this way give me a call an you can hae a look/test ride.
Obviously a dyno sheet trying all options would give you the best/most accurate answer...... but your still welcome to have a look / feel before shelling out any more money

Many thanks for that caveman, very generous. It's nice to know it can be done :)

Have a few options now after actually researching a bit but next time I'm headin your way, might swing by for a nosey and put a face to the name :D

I just fitted a copy set of HKS 4-2-1 to mine, so have a spare set of standard 4-2-1.

If you want, can sell you standard manifold with oxy sensor nuts fitted to suit auto, for $100.

Can install it for ya too for a bit extra if need be.

By standard do you mean the stock 4-2-1 setup? If so, that's what I'm currently running and want to move to an after market set - have looked into a few options now but appreciate the offer dude!