Tuned lengths?

[2khamisj]

Hey I'm currently in the process of building extractors for my 1uz - vs commodore conversion, but am having trouble finding info on the tuned lengths etc. Is anyone able to assist me on this? Thanks

 

[LEXUSA]

I'm sure JBrady will be here to assist very soon. Depends on where you want the best power to be and if you are going to recognize OEM redline.

 

[2khamisj]

Ok thanks for that, the car will be a mild streeter... Im currently only looking at cams & ECU at the moment with some drivetrain mods. My current exhaust is a 2.5" mandrel bent single from the catback (I will possibly upgrade to 3" however I feel 2.5" wont be a restriction at this point in time). I purchased an extractor kit so to speak, It consists of mandrel lengths, header flanges and 4-1 collectors. The size for the primaries I have is 1 7/8", I realise this is large and will possibly sacrifice some low down torque, but will this be significant?
The stock majesta headers will not fit for this conversion, hence my quest to build new ones. I am not looking for a design to support massive numbers, however something that will easily flow 400hp if I choose to go down a higher horsepower path later down the track

 

[Lambo]

Header Calculator

hi 2khamisj, You should find this usefull for your build, just join up to get access to the calculator.Make sure you scroll down the page as there is lots of info below the calculator.

http://www.headerdesign.com/login/header.asp

Regards
Lambo

 

[JBrady]

Ok thanks for that, the car will be a mild streeter... Im currently only looking at cams & ECU at the moment with some drivetrain mods. My current exhaust is a 2.5" mandrel bent single from the catback (I will possibly upgrade to 3" however I feel 2.5" wont be a restriction at this point in time). I purchased an extractor kit so to speak, It consists of mandrel lengths, header flanges and 4-1 collectors. The size for the primaries I have is 1 7/8", I realise this is large and will possibly sacrifice some low down torque, but will this be significant?
The stock majesta headers will not fit for this conversion, hence my quest to build new ones. I am not looking for a design to support massive numbers, however something that will easily flow 400hp if I choose to go down a higher horsepower path later down the track

1.875" primaries are WAY WAY WAY too big. Use those pipes to make duals if you must use them. Really.

1.75" makes MORE torque on the 5.7 liter LS1 engines than 1.875"

1.625" is too large but is the largest you want to use on a street 1uzfe.

1.50" will give you the best torque and have no problem supporting 400hp if you ever get there especially because you will probably use a supercharger to do so.

 

[LEXUSA]

How high do you intend to rev this? The lower the rev range the longer the primaries, usually.

 

[2khamisj]

As stated before the car will be a streeter, so it will not be hard revving 24/7. As for the primaries being too big, can anyone actually provide an estimate on torque being lost?
I know most header companies over here use 1 1/2" primaries on their designs for mild v6's (3.8l ecotec) and then for the supercharged counterparts they use 1 5/8" or even 1 3/4".
I was given these lengths to use as primaries in a kit I purchased with engine mounts etc. Please be patient with my questions as Ive never done this before. Using the header calculator program I've found best size for my use would indeed be 1 1/2". Thankyou for your help

 

[LEXUSA]

The ID of the exhaust ports are around 1 1/2" IIRC. Anything larger might only help at high rpms, maybe. Sometimes too large of a headpipe can cause turbulence and restrict flow killing performance. As with most things, the right size is better than too much or too little.

 

[2khamisj]

I see, I suppose my best bet would be the header design calculator... Does anyone know where I can get the dimensions of the bore/stroke for the 1uz stroker kits? I plan 400hp with extensive N/A mods not FI

 

[LEXUSA]

400hp N/A sounds like a high rpm screamer. If no FI what are your plans? A header's design is always a compromise and tuned for a rev range.

 

[1uzvl]

Slighty OT,but when doing that programe is the max power and rpm etc is that before mods(stock standard engine)or what you hope to acheive??.

 

[2khamisj]

Extensive work... after playing with some variables I realise my best bet would be to make a set for street use and then a redesign for the modifications.

 

[JBrady]

The ID of the exhaust ports are around 1 1/2" IIRC. Anything larger might only help at high rpms, maybe. Sometimes too large of a headpipe can cause turbulence and restrict flow killing performance. As with most things, the right size is better than too much or too little.

Actually the ID of the port is about 1.35" which is almost exactly the ID of 1.5" 0.065 wall tubing. Car must be taken to not create an overlap with any port missmatch using 1.5" pipes. This was solve using a slight swaging of the primary at the flange on the S&S headers.

 

[JBrady]

As stated before the car will be a streeter, so it will not be hard revving 24/7. As for the primaries being too big, can anyone actually provide an estimate on torque being lost?
I know most header companies over here use 1 1/2" primaries on their designs for mild v6's (3.8l ecotec) and then for the supercharged counterparts they use 1 5/8" or even 1 3/4".
I was given these lengths to use as primaries in a kit I purchased with engine mounts etc. Please be patient with my questions as Ive never done this before. Using the header calculator program I've found best size for my use would indeed be 1 1/2". Thankyou for your help

I apologize if I sounded impatient. Ask any questions you wish. Of course doing a search will give you pretty good detail on this subject.

The less cylinders used for any given displacement increase each cylinders needs since each is larger (relatively).

BTW, I wasn't kidding... dual 1.875 mandrel pipes are good for street use. Just barely smaller than the stock size used on stock GS430s rated 300hp/325tq.

 

[JBrady]

Extensive work... after playing with some variables I realise my best bet would be to make a set for street use and then a redesign for the modifications.

I think you will be MUCH happier going this route. Build a 1.5" primary set for daily driving. Search under member RMS for high RPM applications.http://lextreme.com/forums/showthread.php?t=8431

 

[2khamisj]

I think you will be MUCH happier going this route. Build a 1.5" primary set for daily driving. Search under member RMS for high RPM applications.http://lextreme.com/forums/showthread.php?t=8431

Yeah thanks JBrady, picked up about 2m 1.5" straights and what not yesterday, as I have access to a pipe bender. Using the exhaust header program I found my primary lengths to be 30-odd inches in 1.27". Seeing as I am using 1.5", would these lengths be considerably shorter?

 

[Toysrme]

Do you have pipe or tube? What's the actual OD/ID & wall thickness? If possible, port match the flange, have the initial primary a fingernail wider than the port to helpprevent reversion.

Too bad you're not in North America. 1.5" Schedule-10 stainless is ideal for many. Easy for the newbies to weld, long lasting. ID is 1.682, and will flow 200hp+ a cylinder with no problems FI.
Plus, you're not going to want to hack into a turbo manifold at a later date (if possible) on 16-gauge tubing unless you've got a good design and a good welder.

2khamisj the skinnier the longer.


Don't go nuts working out "equal length" either. No such thing. If there were, it still wouldn't matter. Noone's ever made two cylinders make the same power on the same exact powerband anyway LoL. If they're all within 10" of each other by the time you're done. Gravy.



























Email Burns with as much data as possible and ask for help. That's going to be the best "design & material size answer" you're going to get. They've always been good about throwing non-customer projects into "X-design" hah... flashy name... LoL