Tuning for torque peak is for racing cars that spend most of their time in a narrow RPM range. They gear for the track and have a great deal of control over rear-end ratio, gearbox ratio spread, etc. specifically to keep the car in the desired narrow RPM range throughout the track or down the 1/4 mile. This is exactly, 180 degrees (<-maths) opposed to what we want on even a strong street car where a broad torque curve is king and a "peaky" engine is just no fun to drive...and doesn't perform well in the varied RPM range on the street that comes from a fixed driveline.


Many performance calculations from the books are intended for racing applications where the variables can be very precisely controlled vs. the broad compromises required for a street engine - and even then, what works in Excel often doesn't work on the dyno. This is why guys like Vizard and Lingenfelter spend years testing what really works and providing guidance based on what has been demonstrated to work, over and over, on the engine or chassis dyno. There's nothing "random" about it.

 

I will post results with 1 7/8 long tubes into 4 inch collectors to 3 inch out lets that will go into my 3 inch exhaust on my ZZ430 clone. I am setting the car up for a 427 sbc and am almost done ,, but will run the 430 hp till next fall with the 427 drive line and exhaust ..

 

From here. quoted from my posts
http://forums.corvetteforum.com/c3-t...rformance.html

And from this thread;

My appologies if I'm not making myself clear. One has to start from somewhere and these calculations look like good place to start.
This is just Information. How it is used is up to the user.

 

I'm not qualified nor experienced enough to make any recommendations on the effect of various exhaust combos. Nor do I have the testing equipment to do so.
I'm just presenting tools that a person can use to further their own development of their exhaust system should they want to. Any info is likely better than none at all.
This calculator can help you with header size and length to get a desired result.
http://www.wallaceracing.com/header_length.php

Again based on peak torque numbers. Keep in mind that peak torque is used because it is the max flow volume of exhaust that the engine will see per exhaust event.
After peak torque cylinder filling is reduced and so each exhaust stroke contains less volume of exhaust.
The HP method still considers this as the restriction. With greater HP for a given displacement the peak torque event occurs later due to cam requirements.

 

The user just needs the context - which is street vs. race engines, and ensuring the many sources of validated, experiential guidance are considered as well as math that may be in direct conflict with those lessons.


This is where genuine experience comes to bear - knowing how to apply conceptual knowledge on a practical basis and draw the right conclusions.


'Nuff said.

 

I'd say that is a fair assessment. There is no replacement for experience. But someone taught you and someone taught that person etc. Somewhere along the line math was applied. It didn't come from thin air.
Not all of us have the advantage of working with or having someone of experience that we trust to confer with. I wish I did, but I do not and companies that sell products are more interested in $$ than getting me what suits my needs best. So that makes their recommendation suspect.

As has been demonstrated here on this forum "expert" opinions vary depending on that experts experience and depth of knowledge. Often experts will battle it out to no end and leave the OP in a quandary. This is not productive for the person seeking an answer or information on which to base a descision.

I am one of those kind of people that if you make a recommendation that I don't understand the reason behind, I'm going to ask why. If the person making the recommendation cannot answer that to my satisfaction. I will go else were to get my answers. That is each person's option. Since often there there is not another personal source of info. Then it may be necessary to go and figure it out for myself based on what I can learn from a written source.
The results are twofold. One I'll learn something and have a better understanding of how the particular item effects the total package (engine, drive train)
Two I'll get to see why some recommendations are made the way they are and how the answer was derived.

So these calculators and calculations are that other source. Then this information is coupled with what you may already know or been told and there you have an answer. No one source should be used exclusively and that is where this forum comes in. Many different sources and experiences. Mix it all together sift out the chaff and hopefully come up with a useful solution.
Experience will tell you if it was the right one.

 

Not all aspects of engineering lend themselves to engineering mathematical analysis. Talk to head porters and cam designers...certainly there's engineering involved, but there's still an aspect of "I don't know why that works, but it works so we do it." across the board. That's why work is always - always - backed up with dyno testing and why that validation is so important. Math that is capable of consistently quantifying real-world results in performance engine building is great - it's just relatively rare.

Context also includes where the information is useful and can be applied - so for example, a posting a video about tuning racing torque peaks to 5K RPM isn't particularly applicable to a guy asking about 1-7/8 headers on a mild, < 1 HP/CID engine...and may lead him to believe from the information that he's making a good choice.

This, then, becomes the crux of the biscuit - people make decisions on the information posted. For many, it's a significant investment and they don't have the opportunity for an "oops". There's a level of responsibility for people posting information that they understand it and how it applies to the question being asked - and can articulate that clearly to help posters make good decisions. When I see information that can be misunderstood, is being mis-applied or otherwise poses a risk I call it out - doesn't make me very popular, but there it is.

Overall, kind of a big ask for the interwebs to think carefully about the implications of what they post, but it's worth thinking about as we post information for the benefit of our fellow Corvette owners.

 

I purchased a pair of stainless 1.75" SBC headers this past spring during my engine refresh. Once my 12 year old Hedmanns rust out (Jet-Hot coated), I'll update my exhaust with the stainless items. I also had them Jet-Hot coated to aid scavenging; not for increased durability like the old steel pair I installed back around 2000. Never thought I would see 12+ years out of a pair of steel headers. Would have seen more had I put plastic down in my garage the past 8 winters (to block moisture).

I figure I'll see a small bump in performance with the 1.75's given the good breathing of my Dart 180cc heads and comp retro cam kit.