View Full Version : Header Rebuild Help

01-17-2009, 03:53 AM
Hey guys, Im interested in a redesign of my header, its just a shortie with short primaries that are 1 5/8 I think. Ive been reading online about designing the header to match the engine (3sge) and I think id like to give it a shot, modifying the current one, Ive got the fabrication skill and tooling but i need a hand wrapping my head around all the numbers.

So Far ive got

Engine 3s-ge 1st gen (stock cams, sorry im having a hard time finding the degrees),1 5/8th primaries, Want to aim for the power increase to be at the current max torque of 125 ft-lbs@4800 rpms

Primary Length = ?
Collector Length and Diam = ?

Rest of the exhaust = 2.125''

I want to keep the design a 4-1 for simplicity, Im minaly looking to lengthen the primaries and adjust the collector to the correct length.

If anyone can give me a hand, or show me the formulas i would be forever grateful.

01-17-2009, 04:10 AM
I can't say that I'm able to help much, like you, I can fab it, but the math loses me. I do know that most designers use a program to get their starting points and then just trial and error with dyno runs to get it perfect. This might be a bit more than you're looking to do which is why I say....
Leave it. I assume the header you have is the stock one? If it is, consider it rare. It is a very well designed header done by Yamaha who, in case you're new to Celicas, has designed some of the best heads used in Toyota engines. The reason it's rare is that the only place you find them are on '89 USDM GTSs (which are far and few between) and 1st gen 3sges from over seas, in which case are quite hard to get a hold of, not to mention insane shipping costs. I personally use one on my 92 GTS and I love it. But I imagine it's even better on the 3s.
If I was in your shoes, I would consider trying to redesign the stock secondary. You mentioned wanting a 4-1 but a 4-2-1 will be easier to tune to the range you want, and you could probably get close just by tweaking the secondary.
Another thought is that the 3sge doesn't have the best low end response and the 4-2-1 will help to boost this while retaining a good high end response. I believe a 4-1 would leave you with a nasty dead spot down low.
In any case, since I use the same header, I am interested in what you come up with so keep us posted. But remember- should you want to go back to what you had to start with, it won't be easy.:D

01-17-2009, 04:15 AM
sorry to thread jack, but any idea where to get an 89 GTS header?

01-17-2009, 04:32 AM
I can tell you exactly what you want to build if you're willing to do it...

Need to know where you want peak hp, the header will have an effective tuning range of about 2500, aiming for peak tq 2000rpm lower and the tuning range will carry 500rpm above peak hp.

Only if you're serious, will take me a bit to crunch.

01-17-2009, 03:52 PM
Thats MrWOT, I have an aftermarket 4-1 already, but its a crap design. http://www.geocities.com/tigeronfire445/4.gif its for an MR2 but its adapted it to work on the 3sge.

Im 100% ready to get down to it, i want to keep it simple, more or less extend the primaries, modify the collector.

The spec of the engine stock are 135 hp at 6000rpm, 125 ft-lbs@4800 rpms. I want to have the header compliment the stock cam, peak hp 6000 rpm, torque 4800 rpm if possible.

I want to keep torque increase mainly in the midrange, i dont liek the current disign aimed at high rpm torque increase, id liek improve on the stock configuration if that makes sense.

the Primaries gotta stay at 1 5/8s, but besides that let me know what ill need for best results, i can go 4-2-1 if its worth it, but i was thinking long primary 4-1 would be easiest.

01-17-2009, 06:11 PM
The primaries aren't nearly as important as the collector, alright, I will calculate for torque peak at 5000rpm. I'll get back to you tonight after I'm off work.

01-17-2009, 08:12 PM
sorry to thread jack, but any idea where to get an 89 GTS header?
Off an `89 GT-S obviously.

01-17-2009, 08:41 PM
Off an `89 GT-S obviously.

Thanks Murg...

Stealership be able to get part still or will i have to hunt for it thru yards and forums?

01-17-2009, 09:27 PM
Thanks Murg...

Stealership be able to get part still or will i have to hunt for it thru yards and forums?
Never tried the stealership but it's possible. Good luck hunting the yards. So far I only know of one found in a yard in Indiana. I found mine on ebay several years ago and they show up there from time to time, but don't hold your breath.
Now, if your willing to beg and pay some stiff shipping charges, go to ebay and check out international sellers in the U.K., they have several, but the I tried a few years ago wouldn't ship to the US and I didn't bother with the others. The only other way would be to catch one of our members that lives in Europe or Aus and get them to send you one.

01-17-2009, 09:30 PM
I have an aftermarket 4-1 already, but its a crap design.
So I take it you no longer have the stock header?

01-17-2009, 10:11 PM
I have the stock header, but my engine isnt an 89. My old header had a O2 sensor mount on the front, but when I got the car the EGR was attached to the opening instead. Im not sure if the header I had was an 89 header, but as far as my 4th gen skills go I dont think there was a difference of much between years besides EGR and O2 hookups.

01-18-2009, 02:46 AM
On the '89 GTS they put an actual header on it from the factory that was designed by Yamaha. Everything else just came with a crappy standard exhaust manifold. If you don't have the original engine that's a bummer.

01-18-2009, 03:13 AM
Its definitely not a header, are you sure your not getting confused with 2nd gen 3sge manifold (they came in 90 gt-s in europe)? they were actual pipe headers, that can be installed on the 4th gens if you mount your starter tranny side. In my experiences ive never seen a header stock on an 89, and we got a few 89's over at st162.net

01-18-2009, 05:42 AM
The primaries should be 1 1/8" dia, 32.7-35.6" AND/OR 22.8-25.7" long

The collector should be 2 1/8" dia, 22.1" long, OR 44.1" if you want more bottom end than top end....

Collector beginning to tailpipe END (total length)

560.2 or 1120.5 or 2240.9 or 4481.9MM long

2500-5000rpm powerband


I also need the lobe seperation angle for this to be right

edit: btw, the tailpipe end means you need an exhaust termination box there, the actual tailpipe should exit preferably behind a rear tire.

01-18-2009, 03:06 PM
Its definitely not a header, are you sure your not getting confused with 2nd gen 3sge manifold (they came in 90 gt-s in europe)? they were actual pipe headers, that can be installed on the 4th gens if you mount your starter tranny side. In my experiences ive never seen a header stock on an 89, and we got a few 89's over at st162.net
That's exactly the one I mean, and yes, they did come in the '89GTS. In Europe, they came in all Celicas after '90 that had the 3sge.

01-18-2009, 03:09 PM
Thanks WOT, the one issue is that I need to keep the Primaries at 1 5/8 diam, If you check out the pic above im planning to cut the primaries at the collector, extend the , reattach the collector and adjust the pipe diam and length for best results. If we aim for power band between 4000-6500 would it be acceptable to keep the primaries at 1 5/8?

Ill try to find the lobe separation angle, but its hard to come by

Thanks again

01-18-2009, 04:42 PM
It will lose power, but I can't say how much :shrug:

1/2" too big is WAY too big, like 40% too big. But the primary diameter/length isn't as important as getting the collector right.

01-18-2009, 05:01 PM
If we move the power band to a high range, 4000-6500 the needed primary size will increase, making the 1 5/8 a bit less useless? I can Step the tubing down to a smaller diam after the bends coming off the head (once its straightened out) if that will help. If I were to aim for a 4000-6500 power band what would the ideas be? Ill rough up a design a post it if you can give me a hadn with those numbers, thanks WOT

01-18-2009, 05:18 PM

Even revving to 9k you wouldn't need 1 5/8" at 120% VE. If you can't replace them, don't worry about it. Like I said, the collector is key, not the primaries.

01-18-2009, 05:34 PM
ok, I have just a few more question to wrap my head around. Ill try to seperate them as best i can

1)If i were to tune the collector to 4000-6500 power band what specs would I want to build to?

2a)Is it worth Extending the 1 5/8 primaries?

2b)Is it worth extending the 1 5/8 primaries with smaller diam pipe? (first 15" are 1 5/8 last 12" would be 1 1/2)

3) whats the definition of the collector, the area where the 4 pipes merge or the larger pipe that follows? ( ive been assuming its both)

01-18-2009, 05:55 PM
1) 2 3/8" 14.6"

2a) Yes, but only 18.2 inches for 4000-6500

2b) No, the point of smaller diameter is to maintain velocity, once velocity is lost, it cannot be regained without pumping losses.

3) The larger pipe that follows, but where the pipes merge is also important in regards to the angle, length and a few other things, but unless you're going to spend some serious money (good merge collector is over $300 just for the merge section) or know what you're doing and can weld stainless, the pipe is all you are concerned with.

Collectively, it's the collector :laugh:

The LENGTH refers to the point at which the primaries terminate inside the merge, to the end of the large pipe section.

01-18-2009, 07:31 PM
Great info, ive gone out and measured, i the primaries on mine are between 14-16~ inches, and the Inside diameter of the collector is roughly 2 3/8. So Im thinking Ill shorten the Collector (fairly long) a perportional amount to to lengthening of the primaries. (im thinking a 3-4'' extension.)

The current flange joining exhaust and header goes straight from 2 3/8 collector to 2 inch exhaust, no taper, so im thinking of making a cone , i guess about 3-4 inches long that tapers down to the exhaust diameter. Two more thoughts.

1)Is there a recommended length for the tapered cone i would be constructing? Ive head elsewhere tapering the collector can have a large impact.

2)Say I have my 4 inch tapered cone and the collector is 14.6 inches long, should I weld it to the back making the collector and cone a total of 18.6", should i reduce the collector to 10.6 with a 4" cone or split the differience at 12.6 collector, 4" cone.

01-19-2009, 04:05 AM
Tapering the collector does many things, and the angle and length will adjust the tuning range. You are good on the taper length 4"+. and you need to cut the primaries at an angle so they join together at the end of that cone inside the collector, remember, the collector begins where the primaries terminate. The length after primary termination needs to be 14.6"

01-19-2009, 02:34 PM
I was talkign about the end of the collector where it connects to the exhaust system. right now its just a basic flange, but its no good because one side is 2 3/8s and the other is 2"

like so http://img413.imageshack.us/img413/7408/23415552fy3.jpg

red is what im planning to do, to help the flow. I will also look into making a new cone for the collector, maybe 5" long for that one. This weekend ill probably get it started. Ill keep the thread updated.

01-22-2009, 11:50 PM
I'll be putting the new header together this weekend, I got all the parts ready made to weld on, 3" primary extension and a cone to fit to the end of the collector to merge smoothly into the exhaust system

01-24-2009, 06:43 AM
Want to aim for the power increase to be at the current max torque of 125 ft-lbs@4800 rpms
I take it what you really want is to increase torque at your current peak of 4800rpms thereby increasing the HP above that? My calculations and info from some other reliable sources say you should use about 1-3/8" OD pipe for that on a 2.0 liter. 1-5/8" pipe is going to produce peak torque up above 7500rpms which is pointless on and engine with your redline. By using a diameter that big you will be diminishing the effects of any wave tuning you do in the primaries and collector.

I'm going to disagree with MrWOT on one point here but it is really a topic of debate everywhere you go. Many would argue that the primary diameter is the most important measurement, myself included. In my opinion you must get the diameters right first and work on the lengths to swing torque above or below that peak. Get the overall flow right first and then try to enhance it with reflections.

Also the length of the runners and collector will be very dependant on the duration and lobe separation of the cams. Without those numbers you are just ballparking it. Anybody have those for a gen1 3sge?

01-25-2009, 04:03 AM

Theres the start, im goign with mrwots numbers, i still need to finsh modding the collector length and ad the 4th primary extension.

01-25-2009, 10:12 AM
I get about 1 1/8 ID when I figure for 3000-5500

01-25-2009, 11:13 PM
I got the header done an installed, built it to ~18" primaries @1 5/8 and ~14"collector with a reducing cone at the end feeding it to the exhast. I took it for a short drive, low end feel good, was only around the block tho so ill get back it you guys when its been on the highway.

01-26-2009, 03:53 AM
Well? :)

01-27-2009, 08:22 PM
You alive? :ohnoes:

01-28-2009, 02:18 PM
yep but i havnt had a change to really tell. It feels good, sounds about the same. I have it off the car to partch up the pin hole leaks and fix the flange. Its gonna be just about impossible to really tell with out a dino, but I think I may build my own header from scratch , with the best possible specs for the engine once they can be all figured out with the seperation angle and stuff.

01-28-2009, 06:44 PM
Yeah without the cam specs it's really just guessing on lengths