Another one. Exhausted

[Murdoch]

Very interesting read! If there was any doubt in my mind, it's gone now. 1 3/4" 4-1's here I come.

4-1 sound really good mate.
My new wagon has the walki package which I think is the Difillipo system?
The sounds shits all over my old set up which was pretty much a HSV 340kw system. Chalk and cheese.
Maybe the high flow cats help too, im not sure.

 

[Hyperduc]

you should probably have a read of what we did in Project VF as you are far from on the pace as far as when the 1 3/4" become a restriction...we pretty much near on wore threads out changing headers etc on PVFI. Have a read.

http://www.streetquick.com.au/news/project-vf/project-vf-part-iv-the-need-for-speed-continues

Thanks HOWQUICK for the effort your putting in and sharing this with us as well.

 

[Not_An_Abba_Fan]

you should probably have a read of what we did in Project VF as you are far from on the pace as far as when the 1 3/4" become a restriction...we pretty much near on wore threads out changing headers etc on PVFI. Have a read.

http://www.streetquick.com.au/news/project-vf/project-vf-part-iv-the-need-for-speed-continues

I read the entire build and I agree with you. Well, what I have been saying for 20 years and what your results show are basically the same. I think you took my comment out of context, I'm not saying the 1 3/4" are a restriction, I was only saying that if Cuda was going to change headers down the track, why fit the 1 3/4" in the first place when there is very little difference in them. Your results from PVF1 as far as the header change went doesn't really reflect matching headers to an application. It looks like the heads were specifically flowed and ported to suit 1 3/4's. Just by changing the headers, it would have changed the flow characteristics of the heads. Same the other way, if the heads were built to suit 1 7/8" headers would you have seen a similar result stepping down to 1 3/4"?

Another thing I have been saying, and most dynos show it, is that headers are only optimal in a given RPM range. Can headers "over scavenge"? I don't think so, it's more likely the primary size and length isn't matched to the RPM range that the power is dropping away. Here is a dyno of an LS1 that I custom made a set of 1 3/4" proper tuned 4-1's to suit the application IE: burnout car. The specs of the pipes were matched for 4000-5500 rpm. The torque curve shows that.

 

[Hyperduc]

I agree, but the build was for keeping car as standard as possible or only making changes you can afford at the time.
IE. if your going to stay NA then 1&3/4 is more suited.

What I find interesting is that these are easy mods and something the manufacturer could make but they don't.

Is it for warranty? For longevity? Or do they not want to offend the other after market company selling Commodores?

 

[lmoengnr]

What I find interesting is that these are easy mods and something the manufacturer could make but they don't.

Is it for warranty? For longevity? Or do they not want to offend the other after market company selling Commodores?

Emissions and noise regs.

 

[Not_An_Abba_Fan]

What I find interesting is that these are easy mods and something the manufacturer could make but they don't.

Is it for warranty? For longevity? Or do they not want to offend the other after market company selling Commodores?

It's for cost, pure and simple. It costs less to mass produce cast manifolds than it does to hand make headers. An aftermarket part will not affect new car warranty unless the aftermarket part is proven to cause the fault.

 

[Hyperduc]

Emissions and noise regs.

Are we talking illegal from a noise perspective?

 

[HOWQUICK]

I read the entire build and I agree with you. Well, what I have been saying for 20 years and what your results show are basically the same. I think you took my comment out of context, I'm not saying the 1 3/4" are a restriction, I was only saying that if Cuda was going to change headers down the track, why fit the 1 3/4" in the first place when there is very little difference in them. Your results from PVF1 as far as the header change went doesn't really reflect matching headers to an application. It looks like the heads were specifically flowed and ported to suit 1 3/4's. Just by changing the headers, it would have changed the flow characteristics of the heads. Same the other way, if the heads were built to suit 1 7/8" headers would you have seen a similar result stepping down to 1 3/4"?

Another thing I have been saying, and most dynos show it, is that headers are only optimal in a given RPM range. Can headers "over scavenge"? I don't think so, it's more likely the primary size and length isn't matched to the RPM range that the power is dropping away. Here is a dyno of an LS1 that I custom made a set of 1 3/4" proper tuned 4-1's to suit the application IE: burnout car. The specs of the pipes were matched for 4000-5500 rpm. The torque curve shows that.
View attachment 196203

I don't think you understood why we had the head made with the smaller port...it was so WE COULD USE THE SMALLER PIPE rather than be stuck with a port that had to have a 1 7/8" pipe. That was no accident and done as building and racing these cars since the start of LS1 and hotties in general for over 30 years...it was an observation that bigger pipes felt flat under the curve. If you can't get the torque curve right in a LS between 4500 and 5500 you are doing something real wrong...from LS7 427 to cammed LS3 etc near all show peak torque at 45-5200rpm..it is what is happening before that point that gets a streeter out of the hole.

Here is a comprehensive write up on the LS cylinder heads and how the 4.0 came about. We spent a bunch of $$ making that head and put some design stuff into it that we gleaned from offroad racing 6L class. The same head is available with a larger exhaust port...it flows the same numbers.

http://www.streetquick.com.au/tech-articles/sqp-mast-4-0-cylinder-head


The hole in the middle of that torque curve would be nothing I would be excited about. As you know...the architecture of the vehicle dictates where you end up with headers...not something that is compromised on a race only design.

 

[426Cuda]

It's for cost, pure and simple. It costs less to mass produce cast manifolds than it does to hand make headers. An aftermarket part will not affect new car warranty unless the aftermarket part is proven to cause the fault.

Cost is part of it for sure NAAF. Particularly when it comes to headers v cast manifilds. But, re OTR's and tunes, cost wouldn't really be a factor.
Out of interest, do we know why the LSA's didn't come out with piped headers in The HSV's?

 

[Tonner Matt]

Wouldn't it be great if Monstar was here to throw his 2 cents worth in right now