Exhaust headers, LS series engines

[Philm]

Besides, mine is a street car, wanna cruise, take things easy, blow off the occasional rice burner and the odd ford. [/quote]

Hang your head in shame

Phil

[NASSTY]

Originally Posted by Rebel1

Besides, mine is a street car, wanna cruise, take things easy, blow off the occasional rice burner and the odd ford.

Ok Ford boys, let's go for a big cruise to XXXX country and give Uncle Les a flogg'n - on the track of course!

Les, your backflip has been so big that you should be a politician!

[Rebel1]

Originally Posted by NASSTY

Ok Ford boys, let's go for a big cruise to XXXX country and give Uncle Les a flogg'n - on the track of course!

Les, your backflip has been so big that you should be a politician!

Who moe???....dunno wot ya on about.

Once it was called the dark side....now it's a movement, gathering momentum.

[stephen low]

Plums to take you last comment one step further, the std 220kw AU engine's pipes were 1 5/8 and 1 3/4 but we are still only talking 5L.

I'd be interested to know what the last of the AU's, the stroker, ran for pipe sizes, considering this motor's capacity is closer to the LS1 one would expect slightly larger primaries and secondaries.

This knowledge would be good for me down the track as I plan to stroke the motor down the track. I'll just settle for rego. at this point of time!!

Cheers

[Classic Revival]

We base ALL our work on SOUND ENGINEERING PRINCIPLES & experience, not someone’s opinion. In this case the branch of engineering is called Fluid Dynamics.
For an internal combustion engine to achieve a high efficiency, the flow through the exhaust MUST be laminar. If you increase the dia of the exhaust header the flow turns turbulent & the efficiency decreases. Even on the race car ( which produces far more HP & torque than you will see in a Cobra road car ) the primary tubes are still 1 5/8 to maintain the low down ( below 4000 RPM ) torque. Yes, there is a slight trade off in HP at high RPM, but this is only very slight.

Your “opinion” seems to be based on what the so called “expert tuners” (who are not worth a pinch of ****! ) do. They are great at tuning vehicles to run at full throttle opening, but not at making them driveable below 4000RPM which is where the motor will spend most of it’s time on the road. A good example of this can be found on another thread on this forum where one of the US tuners gives dyno results of their cam etc in a LS1, it produces some 510 HP. However, if you look at the dyno graph, ALL of this HP & torque is produced between 5500 & 7000RPM !!! It has in fact a slight DECREASE in power & torque at low RPM !!! – not what you would call a “drivable” unit.

For a good drivable vehicle you need a broad spread of torque across the rev band not something that is very “peaky”& this is why we stick to the smaller primary tubes.

Our vehicles speak for themselves, be it road or track, they are on top because they are based on SOUND ENGINEERING PRINCIPLES.

Cheers,
Ian

[Aussie Mike]

The better examples of these tuners that don't know **** seem to be able to take an internally stock unopened LS1 and with the addition of a good set of headers, a cold air intake and careful tuning and push it down the 1/4 mile in 11 seconds. They aren't doing it with 1 5/8 headers though. The dyno curves I've seen for these motors show an overall increase in power right through the range. It might seem like there is a loss of low end but that's only because they gain so much in the mid range and top end.

Perhaps you should talk to some other tuners than the ones you are using at the moment. After looking at Bretts car I noticed it had a 3" neck on the air filter stepping up to 4" for the MAF and throttle body (Something to do with fluid dynamics?). I also couldn't find the IAT sensor anywhere and this is crucial for optimizing ignition timing.

I have heard that one of these tuners that doesn't know a pinch of **** has just re tuned it and it's making significantly more power than it was when it rolled out of your shop.

Cheers

[Plums]

Clearly your "SOUND ENGINEERING PRINCIPLES and experience" come from years of tuning LS1's, AND from trying countless different combinations of exhaust systems for this particular engine.

I don't have an "opinion" on this subject, I just have my own experience.

The reason I originally posted in this thread was because of your "1 5/8 pipes are far better than larger pipes" statement. This statement annoyed me somewhat, because quite frankly, it's bull.
I was going to just let this ride until I saw the statement I have quoted below.
Quote: "Even on the race car ( which produces far more HP & torque than you will see in a Cobra road car ) the primary tubes are still 1 5/8 to maintain the low down ( below 4000 RPM ) torque."
This quote just cements my belief that you are just out to "flog your product" even if it's not really the right product for the customer!!!

I guess you are also right about my tuning skills (that are not worth a pinch of ****!). Because of the lack of drivability below 4000rpm, most of my customers have to drive around in 2nd just to keep the revs up! Just ask Aussie Mike, Leeroy and snkbte (all who have CR's by the way) from this forum, I'm sure it annoys them no end

EDIT: If Bretts car is the one I am thinking about, we managed to screw more than 50 extra hp out of it AND make it WAY more drivable. After fitting all the correct sensors and equipment of course.....

[LoBelly]

The thing is... experience does not equal proof. Neither does basing a design on sound engineering principles constitute proof.

At best this is evidence.

It may be that someone has a lot of experience tuning a type of motor, and they may then be able to say that - all other things being equal - that header primary size A is better than size B.

A real lot of experience may then entitle someone to claim expertise.

They may then reasonably argue that they anticipate no comparative difference with the results when the combinations are moved to a Cobra. (And certainly the contribution is valuable and I'd like to see it continued)

However, until the results are tested in a Cobra - its still opinion. Perhaps even expert opinion (which will carry a lot of weight)

Proof would come with the hard data (say dyno graphs) from the same engine with the different header sizes in the application in question.

I think that if you're claiming that what you're saying is not opinion and asking someone else for proof then I think its reasonable to expect that Your proof be provided.

So I'm seeing a lot of 'talk' and not much data - That basically was my point.

The other interesting notion this thread has raised is the question of being up one's self . I haven't heard that phrase in a long time and it made me laugh - its not really a way in which I'd generally view someone but perhaps it could be instructive.

I guess the assessment is (again) a matter of opinion. If I were weighing up someone in that manner - in the context of their posts in this forum - I guess I would have to look at the level of vitriol, the respect they show others' opinions, their capacity to support their arguments in a cogent manner and the degree of circumspection and qualification they add to their opinion.

Hmmm......might be better for me if I don't apply that test to close to home

LoBelly

[NASSTY]

Firstly, I have no experience with regards to headers or exhausts and I have relied on the opinions/experience of others for my application.

If the article posted by Rebel1 is to be taken as evidence then that article suggests that the whole sytem, not just the primaries, needs to be matched properly.

Perhaps what has happened with this thread is simply a matter of a few "black & white" statements being made instead of qualifying your opinions/experiences. For example, 1 5/8's primaries may be more appropriate for most street applications.

While most cobras are modied to some degree, I think based on the entries at the Nationals, most are not heavily modified and consequently not chasing as much HP as they possibly can. If that is considered to be reasonable then 1 5/8 primaries may be all that's needed.

It's all horses for courses. Do you want to chase maximum HP or not?

I think the more support manufacturers give to their clients the better.

Bring on the debate but it would be great if derogatory comments weren't included.

Cheers

[sambo]

Al, I agree wholeheartedly and I just wanted to back your comments up. I think it's great that Ian has gone to the trouble of bulk supplying these headers, but both he and others probably want to avoid making broad technical statements or personal remarks, for the sake of this forum.

I spoke to Warwick Harrison last week and he mentioned that he has Chev headers on the way for his Cobra kit, designed I believe with the assistance of an experienced exhaust guru. I'm sure more details will emerge soon.

Meanwhile, let's look at Ian's offering as "A Good Thing" for the Cobra community and by all means have a healthy debate - that's what public forums are all about. Any R&D that a kit manufacturer does of their own accord can only improve the end result for all of us.

Paul

[Plums]

I agree that for many Cobra drivers, these 1 5/8 pipes will do a marvelous job. For an untuned LS1, these pipes will be a great choice.

As soon as you get a decent MAFLess tune, a step to the next size would be ideal. Why? Most decent tuners can tune the "bottom-end" with larger pipes to equal, if not exceed the smaller pipes torque gain, with better top-end performance too...
Chasing maximum HP is not what it's all about. Why not get a few extra HP up top, while still maintaining the same bottom-end performance????

All of the above relates to stock, unopened LS1's. As soon as you put an aftermarket cam in an LS1, these smaller pipes will be left behind for top-end performance.
These smaller pipes will still even work on over 400 cube LS1's, they will just strangle it somewhat...

NASSTY has absolutely and positively hit the nail on the head!!! The whole system needs to be matched. There is one problem with Cobra's, people try to make them look original by using the 2 inch sidepipe bends and the large 3 1/2 inch collectors. 1 5/8 primary pipes that step-up to 2 inch pipes then a 3 1/2 inch collector will absolutely kill performance. The laminar flow that Ian mentioned earlier will be totally lost. Even a 1 3/4 pipe step-up to a 2 inch is too much and will hurt torque.
If you wanted to run these 1 5/8 pipes, I would suggest running 1 3/4 side pipe bends....

[Rebel1]

OK....so I often get accused of being somewhat different. That's only cuz I'm the only insane one amongst us. So to keep with tradition I'm gonna put in my 2 cents worth.

Many of us have an interest in track work. That implies wringing every last bit of power one can from their engines.

But.....some of us are not into that, we only want a good street car that will blow most of the showroom cars from the road. Now, this is where I get to be somewhat different.

With regard to the Gen111 and IV Chev/holden motors the stock cast manifold has proven to be more than sufficient for healthy street work or, as plums described, an unopened but well tuned engine.

The restriction with these engines in their parent cars are from the cats back. In other words most gains can be had in the parent cars by replacing the standard exhaust system with aftermarket cat back systems.

The problem is that these standard manifolds can be difficult to use in a cobra because they exhaust backward. However, if you swop left to right you'll find in many cases they will fit and will allow a nice curved J pipe to run under the car to the cats.

How can I justify my claims about the performance factor of these standard manifolds?. Go the Australian LS1 site....do a search. You'll find plenty of comment and tests that imply that the standard manifolds are great up to the point of installing a cam.

Now....It's back to the funny farm for me, to the bees and flowers and laughing birds and basket weavers who twiddle their thumbs and toes, etc. etc. etc.

Cheers Les

[HSVREDSLED]

Originally Posted by Rebel1

How can I justify my claims about the performance factor of these standard manifolds?. Go the Australian LS1 site....do a search. You'll find plenty of comment and tests that imply that the standard manifolds are great up to the point of installing a cam.
Cheers Les

.....................Un-tuned.........Tuned
Pacemaker.......hp lbs/ft..........hp..lbs/ft

1.5" Tri-Y.........339 349.......... 364 373
1.625" Tri-Y......353 357.......... 370 379
1.5" 4>1 ..........309 341.......... 364 379
1.375"..............339 354.......... 360 374
1.625" 4>1........349 355.......... 368 378
1.75" 4>1.........340 344.......... 371 381


Sams Brand XX

1-5/8 t-y&2.5"....352 358........ 376 383
1-5/8 4>1..........344 354........ 374 380

Genie

1-5/8 4>1..........347 353....... 368 377
1-5/8 Tri-Y........345 355........ 374 382

HM Headers

1-5/8 & 2.5........349 355......... 370 379
1-5/8 & 2.25......343 352........ 372 381

Hurricane

1-½ T-Y...........346 356......... 363 375
1-5/8 T-Y.........350 358......... 369 380

DiFilippo
4>1..................343 356........ 374 381

HSV
4>1..................340 349........ 365 373

CAPA
4>1 .................356 356........ 371 377

Wildcat
1-5/8...............346 353........ 370 376

Advance
1-5/8 T-Y.........355 358........ 373 382

Hi-Tech
1-5/8...............352 357........ 372 380

Std Manifold
.....................347 349........ 367 372

**This has been faithfully & accurately pasted, with no fudging of ANY figures!

(Copied from LS1 website.)

[Rebel1]

Hey, thanks loads HSVREDSLED, guess that proves a point.

Given that often our finances are stretched and we have heaps of other things to spend money on, then that proves that using a standard manifold is an excellent and inexpensive option.

The cost of a fancy header system is better off being put towards a good CAI in my opinion.

Tis Ok if you are a welder type but to us more, ahmmmmm, academic types, then not having to make extractors/headers is one hell of a saving.

Cheers

[sambo]

Do the factory headers literally go straight on when reversed or do they need drilling or adapting in some way? Sounds like a good cheap way to get the car running and maintain that factory look for rego.

[Rebel1]

They go straight on Sambo.

Pic in my gallery if ya wanna see what it looks like.

Cheers

[sambo]

Beaut - that's one of the less ugly designs I've seen from the factory. How much are they new? Reminds me of the ram horns I had on the HT Monaro.

[Rebel1]

Dunno what they cost Sambo....if you purchase a crate L76/LS2 they come with them.

They are the same as you see on the L76 pics in my gallery except the heat shields have been removed.

Cheers

[boxhead]

I am not sure Sambo, but I may have afew sets of these at home, give me the weekend to look abd I will let you know.
The only thing is due to the weight they might cost abit to send.
Possably get talking on the LS1 site and ask if there is anyone near you who might have some looking for a home.
While I am at it Les I will be digging out the fuel pump for you and send it over.

[sambo]

Thanks guys. I'm a ways off getting the engine (haven't got the car yet!) but it's nice to know that money can be saved in this area without sacrificing too much power.