Batass

Only cuz it doesnt have a chipped Duramax in it!

1989GTATransAm

I'm adding this little nugget of information regarding headers. I had ask Larry Meaux of PipeMax fame a question regarding long tube headers and short tube headers. Here is the question and answer.
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"1989TransAm wrote:
Larry, regarding short header exhaust system.

If one was to have the correct primary tube diameter, correct collector length and correct collector diameter would not a shorty header exhaust system approach a long tube header system?

Also when figuring the correct collector length what effect if any does a cone in the collector have for measuring purposes?

Answer:
Yes a "Shorty" Primary tube Headers can come close to another pair
of long tube Tuned Headers as long as the Collector Specs
are on the money !


Also when figuring the correct collector length what effect if any does a cone in the collector have for measuring purposes?

depending on the Cone Taper and Length,
usually .25 to .50 times the Cone Length is added to the Primary Tube
length... it gets complicated quickly as the amount of Taper/Length
can also have varying amounts of Temperature effects,
also depends on how much Cone heat is retained."

Orr89RocZ

more than likely i'm going shorty headers and turbo over winter with new heads.....maybe C4 vette manifolds for a single turbo. not sure yet i have to plan this out and see if i can hit my goal of 600-650whp with my block/internals at 9.8 or so to 1 compression

1989GTATransAm

Designing headers for a turbo is a different animal. I believe you will be trying for maximum exhaust velocity with low heat loss. You may want to consider a tubular K member for a lot more exhaust clearance.

Your car with that much power will really be an animal. The whole set up should be very streatable though.

I wonder if another camshaft would work better with a turbo?

From what Larry said I believe a well designed shorty header system will not be that far behind a long tube header system of equal design.

Orr89RocZ

I'd wonder how much power i'd give up over these Hooker longtubes because it would be worth it to loose 10whp to gain exhaust clearance. Right now it hangs LOW

And if i did a turbo i'd probly swap the cam as well but i have to ask Bret if this thing will work for mild boost. It really doesnt look like a turbo grind with huge exhaust duration split and tight LSA.

I also thought about AFR 210's or the comp 195's and a bigger cam but i'm not sure i want to make the car any less streetable. Was thinking of trying a custom grind i created that should peak in the 6600 rpm range.

1989GTATransAm

From what I have gathered you may be talking 10 horsepower with a well designed set of short tube headers versus a well designed set of long tube headers. Maybe nothing versus a well designed set of short tube headers versus an average designed long tube header.

According to PipeMax with shortys I need primary pipes of between 14 and 17 inches in length. I will be installing a tubular K member so this will be no problem to achieve even with a well designed collector with a cone.

The collector will be right below the two middle exhaust ports and the middle pipes will probably be around 14 inches long. The two outside pipes will be around 17 inches long.

Then most important is getting the secondary or collector pipe the right length and diameter. The length will be the job of the terminator box.

Orr89RocZ

problem is if i go back to shorties i'll just get dyno don's since they are the only 1 3/4 header out there i guess unless there is a un smog legal version which is what i need anyway.

it wont be custom designed so the power losses may be more than i want to take

skinny z

It looks like it may actually be easier to get an optimum collector length with a short header design because of the additional room. My concern is how much of an impact the short primary pipe would have regarding where peak torque and hp occur. Doesn't a short header push that point higher up the rpm scale?
Of course there's the same question. Where do you fit a resonator box?
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Are you going to have the opportunity to test an open header and collector as opposed to your full exhaust?

skinny z

Quick question.
According to Pipe Max, which collector length contributes to building low rpm torque?

1989GTATransAm

"Doesn't a short header push that point higher up the rpm scale?"

From my research here is what I have found if I have understood things correctly. Below peak torque long tube headers are better. Above peak torque there may be no advantage. That is based on everything else being correct.

So a well built set of shorty header can be better than a run of the mill long tube header. A well built long tube header would be better over all. So the bottom is line with a good set of shorty headers for our cars you may not be giving up all that much.

Just had an idea. Let's compare Orr's long tube header car with my Dyno Don short tube header car. We will use rwhp versus cubic inches. Both are 700R4 automatic cars with similiar stalls. Of course there are dyno differences but both are SAE numbers and the same type of dyno.

Orr made 392rwhp with 383 cubic inches. That is 1.023rwhp/cubic inch.
My car made 370rwhp with 355 cubic inches. That is 1.042rwhp/cubic inch.
Pretty darn close if you ask me.

1989GTATransAm

Regarding the room for the termination boxes. I had given up on it until I noticed that a tubular K-member freed up a ton of room. I'm also going with a Canton Oil pan to free up some more room. I will take pictures of what I will be doing.

skinny z

What I really want to see is some data comparing full exhaust with open headers. Dyno simulations show hp increases along the lines of 10%. 412 chp vs 451 chp in my case. That to me is worth pursuing.
I'm looking forward to your terminator box construction. That would be the icing on the cake.

TheBadazz

Hey chaps we are finishing up that 92' rs with the 4" terminator tube. We should have some pics soon and some dyno numbers to compare shortly after that. We had a few set backs but we are getting close to having her done. We'll keep you guys posted.

Orr89RocZ

yes i will be adding a cutout here sometime whenever i feel like taking the exhaust off. I hope to add it and then take it to the dyno to finalize the new MAF sensor tune, and then i'll do a cutout open run on the dyno

then i will track the car again.

I may order the cutouts tomorrow

1989GTATransAm

Orr if posible try to get the cut outs around 18.4" from where the primary tubes end in the collector. That should get you the maximum benefit. Let me recheck PipeMax.

The best locations are 18.4" and 36.8" from the end of the primary pipes.

The worst locations will be 27.6 and 55.3 inches.

Orr89RocZ

I peak at roughly 6300 and would like to boost the 6000 rpm range due to my gearing not allowing me to cross the line any where near peak hp.

i think i'll beable to reach near 18 inches but depends

1989GTATransAm

"Hey chaps we are finishing up that 92' rs with the 4" terminator tube. We should have some pics soon and some dyno numbers to compare shortly after that. We had a few set backs but we are getting close to having her done. We'll keep you guys posted."

I'm looking forward to the results.

skinny z

Which offers the best low end torque? I don't have the grunt of the 383 and good use a boost around my stall speed.

1989GTATransAm

In Orr's case the 18.4 gives the best all around performance. The 36.8 gives the better low end torque. We may not be talking much of a difference.

Orr89RocZ

my torque output seems low for a 383, i could use more. BUT 36.8 would put me at the y pipe almost i believe. i'll have to shoot for 18

tomorrow or maybe sunday i will try to install the subframe connectors finally poor car

while its in the air i'll take measurements on the cutout placement. i want electronic ones but can not justify 300 bucks for the pair

skinny z

I designed my y-pipe to be removed easily at the track. Isn't that easy. Anything underneath these lowered cars and you need a full set of jack stands.
The cutouts would certainly make things effecient.
As far as science goes, do you think the cut outs would behave sufficiently like " a substantial change in cross sectional area " even with the balance of the exhaust still hooked up?

Orr89RocZ

The exhaust will find its way thru the lowest pressure spot. Any pin hole in the exhaust air will leak out as exhaust is slightly higher pressure than atmosphere.

So with the cutout available, 90% of the air will flow outward i think. So it will act like open end pipe

skinny z

Been thinking about that.
Have you calculated you dynamic c.r.?
Couldn't find it in your old threads or all the info to figure it out.

1989GTATransAm

Couple of my thoughts on a cutout. If you already have a good free flowing exhaust system I don't think you will gain much as you have already eliminatied much of the back pressure.

However by the proper location of the cutout you can gain from wave tuning. This can be quite a few horsepower. You just have to locate the cutout in that sweet spot. Now it might also be possible to loose or not gain any power by installing the cutout in the wrong locations as indicated in my response above.

Orr89RocZ

Dynamic is around 8.3 to 1.

yes i'm not going for more flow, i'm going for wave tuning with cutouts. I'm sure abit mor flow helps since all that piping length kills some flow in the long run but the wave tuning will help alot

1989GTATransAm

I agree with that. I think there is a little to be gained from the flow but most will come from the wave tunning in your situation.

thebufenator

I've been reading through this thread and was intrigued enough to get PipeMax for myself.

My engine build is a 383 LT1 engine.
The hedders I have are Pacesetter LT's.

According to my engine specs PipeMax tells me I want a collector that is either 16.4 or 32.8 inches.

I will be using a dual 3" exhaust system so the pipes are the same size as my collector.

Here is the question.....

Do I want to put the "resonator", or whatever is going to be used for the pressure change, right after the specificed length for the collector?
Also, what specific muffler or