1UZ with single exhuast after cats what size

[deankdx]

hi guys, i am planning crown V8 into an aussie XF ford falcon, what i'd like to know is what size pipe to run afer the cats? in a similar car i had a 351 clevo running standard manifolds(look more effecient than crown ones though) and 2" from each manifold from there into cheap y pipe with a single sports muffler 2.5" no room for resonator after diff(one can fit before main muffler)
with this car i was happy with note and performance but due to gas cam only revved to about 4500-5000rpm. with the 4.0 i was thinking this size would be fine due to being a smaller motor and revving a bit higher sometimes, need to keep a fair amount of low end torque as i don't plan to rev its nut off too often.
any ideas or suggestions would be appreciated thanks
ps i looked through all exhaust theads and didn't find the answer

 

[JBrady]

So, you have dual 2" pipes feeding a Y pipe and then a single 2.5"... correct?

This should work fine with the 1UZFE. If you can post a picture of the Y pipe I will comment on if you should consider a better part.

Either way, you are going from nearly a 6 liter engine to a 4 liter engine so the low end torque is not going to impress you.

 

[deankdx]

So, you have dual 2" pipes feeding a Y pipe and then a single 2.5"... correct?

This should work fine with the 1UZFE. If you can post a picture of the Y pipe I will comment on if you should consider a better part.

Either way, you are going from nearly a 6 liter engine to a 4 liter engine so the low end torque is not going to impress you.

got a six cyl exhaust at the moment 2 1/4" sports system but a 2.5" is readily avail for this model even second hand from peole who go 3" as upgrade on 351.
i've seen a pic of the y peice you are talking about and its a work of art, not sure if its readily avail here yet.
351 motor was a big heavy lump that guzzles fuel($1.10litre in australia)$4gal?
hoping the lexus donk will make the car handle as or better than the 6 cyl which is good but doesn't sound like an 8cyl

would a 3" single exhaust be better or would it affect bottom end grunt too much on a 4.0?

 

[JBrady]

If the 6 cyl is all iron is probably weighs more than the Lexus V8.

I would go with the 2.5 single.

You can have a competent shop make a good Y pipe out of mild steel or stainless. Take 2 sections of primary size (in your case 2") and slash/angle cut them at 15 degrees. Weld them together in a "V" shape and cut the end to SLIGHTLY under your outlet pipe diameter (in your case 2.5") you can swage the ends to accept your primarys or weld them in place. The bottom of the V can sit inside your secondary pipe and be welded in place.

Of course you can get fancier if you wish but the above will work very nicely. Here is a picture:

Of course building 2 of them and welding them together makes an excellent X pipe.

 

[deankdx]

If the 6 cyl is all iron is probably weighs more than the Lexus V8.

I would go with the 2.5 single.

You can have a competent shop make a good Y pipe out of mild steel or stainless. .

thank you for your valued advice, i read that you are well regarded as a specialist in exhausts on this forum the motor thats currently in this car is cast iron block alloy head combo of 4.1 litres with pushrods and single cam redlines at4,700 although most dont see any higher than 4000rpm even when thrashed.

while we're on the topic of exhaust pipe size how do you think the sports system already fitted of 2 1/4" would go after the y pipe it has a resonator(hotdog)and rpobably a straight through sports muffler.? i'll probably hook it up in this way first just cos its there, may even run down the 1/4mile to see the difference and note bottem end torque response?

 

[hi-lex]

Im running standard 2 1/4 ex that was on my 98 hilux with 2 mufflers, an had to make y piece very restrictive an mine still goes like the clappers (spins wheels 1st and into 2nd) I got a set of cheapo headers off ebay so one day might fit up with twin 2 1/5,s but the car is so smooth and quiet its almost a crime to change it

 

[deankdx]

Im running standard 2 1/4 ex that was on my 98 hilux still goes like the clappers

thanx hi-lex i was thinking this would probably be ok considereing the 302 clevo motors(usa never got these) but probably same for 302 windsor came with 2" press bent exhaust with crap y piece and still went good enough and revved to around 5000rpm ok and the antitquated motor is 1litre bigger and revves nearly as high as i'd be happy with from 1UZ

just wondering hi lex what revs you have at 100km/h i'm guessing over2100 with you're setup.
i'm hoping the 1UZ has as much torque down low as a 250 crossflow falcon motor, as i want to use diff ratio of 3.23 thats also already there with manual and 5th gear .7 should be around 1900@ 100km/h

 

[JBrady]

The stock center pipe on LS400s and SC400s necks down to 50mm (1.96") then back to 60mm (2.36") and the 1998-2000 models make 290hp/300tq. A single 2.25 will be enough and should make good torque while a 2.5 will also work especially if you construct the Y pipe as I described. I would even experiment with a 2.25 outlet from the Y pipe expanding into a 2.5 main pipe.

I didn't know that you already had a 2.25 single on the car. Most people go too large and loose torque. Try it as is and let us know. Exhaust is science and art of construction. Suggested sizes are dependent on execution.

 

[deankdx]

The stock center pipe on LS400s and SC400s necks down to 50mm (1.96") then back to 60mm (2.36") and the 1998-2000 models make 290hp/300tq. A single 2.25 will be enough and should make good torque 2.25 outlet from the Y pipe expanding into a 2.5 main pipe.
2.25 single on the car. Most people go too large and loose torque. Exhaust is science and art of construction. Suggested sizes are dependent on execution.

thanx JBrady i am still in the planning stage at the moment as i don't want a bomb taking up space that isn't able to move for a year, i hope to complete the job within 3 months from when i start(hoping to start about feb)(i usually stay within these time frames with my other projects) i priced a y piece as you suggested in 409 stainless and was $70 au($6.50 us J/k) which i reckon is worthwhile, pipes from cats maybe another $100 depends on whether stainless or mild
only reason i was thinking of 2.5" in the first place is cos the 1UZ revs to six grand whereas old pushrod bombs only go about 5grand

 

[Peewee]

I'm not as much as an expert as JBrady on this, but I tell you what I've got.

Mine has 2.5" after the headers, through twin 2.5" cats, into a single 3" all the way out.
I only have one resonator, and one 16" (I think) Lukey 3" muffler, and its a tad too loud for my likings.
I want twin 3" mufflers, but until I get a custom fuel tank (tank takes up 3/4 of the rear of the car) I have no chance of twin outlets.

I have set my exhaust up to be as free flowing as possible, as I plan to have this motor revving all the way to 9grand after some cams.
Motor still pulls better than the 3.0L I had in there before, even when I accelerate from 50kph in 5th gear, it still pulls nicely.

 

[deankdx]

I'm not as much as an expert as JBrady on thisMine has 2.5" after the headers, through twin 2.5" cats, into a single 3" all the way out.
I plan to have this motor revving all the way to 9grand after some cams.
Motor still pulls better than the 3.0L I had in there before, even when I accelerate from 50kph in 5th gear, it still pulls nicely.

i have a couple of questions for you PEEWEE, what diff ratio do you have now?(you're 5th gear if its a toyota box is prob .85 mine is .7) seeing that you had a 3.0 i assume you have a VL(which is very light, i once had a VH) is the diff ratio the same as when it was a 3.0? (i remeber a stock manual VL going close to keeping up with my old 351) so you're pulling power is appealing i'm hoping it (1UZ)has as much torque through the lower rev range as a 4.1/4.0 ford six?????
i expect my car in 5th would be doing 950rpm @50kmh which i don't recommend i would be in 4th @ 1300rpm at 50kmh

9000rpm WOW 8 throttle bodies and lumpyas cams and aftermarket computer in my dreams, i'd rather turbo for similar cost and fatter torque better fuel economy then i may need bigger exhaust as you have.
thanx for you're input still and i hope you get there 9000rpm WOW

 

[Peewee]

5th gear is 0.861 from memory, diff is 4.1:1 at the moment.
Its a Cressida, not a VL.

car does about 1400-1500rpm @ 50kph in 5th, due to the diff ratio.

Already got the aftermarket ecu, and a twin intake manifold, and custom extractors.
Lumpy cams are next on the shopping list, but a few months away for sure.

 

[deankdx]

5th gear is 0.861 from memory, diff is 4.1:1 at the moment.
Its a Cressida, not a VL.

car does about 1400-1500rpm @ 50kph in 5th, due to the diff ratio.

Already got the aftermarket ecu, and a twin intake manifold, and custom extractors.
Lumpy cams are next on the shopping list, but a few months away for sure.

ah yes thanx for that peewee, my plans are different to yours, ha even in forth i'd be revving less, with that diff ratio i'm supprised you son't wheel spin right through first and second on full throttle rolling starts.
cressida hay? thought these would have a bit of torque and not rev high too more interesting stuff... thanx again

 

[Peewee]

You'd be surprised how quickly I can take off, and without giving it a fair amount of herbs, she won't spin.
Forget spinning in 2nd gear too, its all grip.
And this is with cheapish 205 width tyres.

The 1uz is not a tyre frying motor.

 

[deankdx]

You'd be surprised how quickly I can take off, and without giving it a fair amount of herbs, she won't spin.
Forget spinning in 2nd gear too, its all grip.
And this is with cheapish 205 width tyres.

The 1uz is not a tyre frying motor.

here's why the question is regarding exhaust sizes, with too big a pipe as JBrady has mentioned you can lose bottom end torque, no doubt a bigger pipe will help if revving to 6 grand or so but i value all opinions and experiences as you never know down the track bigger cams 3.9 diff and computer are not out of my reach if i need a bit more go

 

[Peewee]

Yes, too big an exhuast will reduce low down torque.
Those manifolds would be good for supercharging, as the supercharger would give you back the low down torque (depending on the type of supercharger), and the manifolds would help it breathe at higher revs.

I had the VERY restrictive stock manifolds to begin with.
Car seemed to rev freely all the way to 6500rpm.
But after getting the extractors, I realised that they were beginning to choke at upper revs, as my power from 5000-6500 didnt drop off as quickly with the extractors.

The stock cast manifolds will rev to 6000 quite happily, the stock log stainless manifolds rev to about 5500 happily.
They both will go to 6500 easy, but they will rob power up there.

 

[JBrady]

I'm not as much as an expert as JBrady on this, but I tell you what I've got.

Mine has 2.5" after the headers, through twin 2.5" cats, into a single 3" all the way out.
I only have one resonator, and one 16" (I think) Lukey 3" muffler, and its a tad too loud for my likings.
I want twin 3" mufflers, but until I get a custom fuel tank (tank takes up 3/4 of the rear of the car) I have no chance of twin outlets.

I have set my exhaust up to be as free flowing as possible, as I plan to have this motor revving all the way to 9grand after some cams.
Motor still pulls better than the 3.0L I had in there before, even when I accelerate from 50kph in 5th gear, it still pulls nicely.

Peewee, from you original extractor post you stated 1.5" primaries, 2.0" secondaries and 2.25" collectors. From the picture the collectors join into a single pipe. I take it the single pipe is the 2.5" you state and then you split this into twin catalysts and then rejoin them into a single 3.0" pipe... is this correct?

Post some pictures if you have them. Your system is certainly unique and it is great that you have both subjective and test data to compare the results.

 

[Peewee]

Peewee, from you original extractor post you stated 1.5" primaries, 2.0" secondaries and 2.25" collectors. From the picture the collectors join into a single pipe. I take it the single pipe is the 2.5" you state and then you split this into twin catalysts and then rejoin them into a single 3.0" pipe... is this correct?

Sorry, it is 2.25" collectors each side, then either into twin 2.5" into twin 2.5" cats, or it goes straight into twin 2.5" cats from the 2.25" collectors.

After the cats it continues as twin 2.5", into a single 3", through a single 3" resonator, and then a 3" muffler.

I'll try and get some photos as the car is on stands at the moment.
But its all painted matt black for a stock looking effect, so its hard to see.

 

[JBrady]

Sorry, it is 2.25" collectors each side, then either into twin 2.5" into twin 2.5" cats, or it goes straight into twin 2.5" cats from the 2.25" collectors.

After the cats it continues as twin 2.5", into a single 3", through a single 3" resonator, and then a 3" muffler.

I'll try and get some photos as the car is on stands at the moment.
But its all painted matt black for a stock looking effect, so its hard to see.

So I take it that you changed from a single to duals off the extractors. The picture below that you posted is definitely a single.

 

[Peewee]

Yeah, I'll post a new pic when I take one