427 SBC test debunks 128 debunckers

[David Vizard]

This is the engine tech section, not the I have a book and engine for sale section. Play it anyway you want, everyone else has enough respect not to do it, IMHO.

Drill,

Would you mind telling me just how many other ST posters earn much of their income by writing books. Heck those guys doing heads, cams, etc. they don't come in for the blasting that I get!

Tell you what - let's have some extra opinions here and see where the cards fall.

My goal is to make sure the people get the right answer to their questions not this so many screwed up answers that the Internet is capable of giving them. If somebody else says oh you can find that detailed DV's book [pick a title] on page so-and-so and so-and-so that's fine but if I say it exactly the same thing it's not and if it doesn't get said that end-user using the wrong information finds he makes costly mistakes. If I'm to look after my readers do I let them suffer in such a manner or help them out.

The amount of tech I put into my posts far outweighs the amount of plugs I give myself of course that's my opinion and I'm sure those who agree and those who don't will chime in here. I at least hope that it weighs in on my side.

I think with the amount of money I spend to service guys needs here I should be given a just a little leeway by those people who do very little to do so. Of course I could give up posting - it does use up a lot of my time.

DV

[David Vizard]

This is the engine tech section, not the I have a book and engine for sale section. Play it anyway you want, everyone else has enough respect not to do it, IMHO.

This^^^

There are two types of readers of the 128 formula.

1. Those that think it is great

2. Those that understand how a formula is derived and what a polynomial fit looks like.

And you're less than obvious point is?

DV

[plovett]

Drill,


The amount of tech I put into my posts far outweighs the amount of plugs I give myself of course that's my opinion and I'm sure those who agree and those who don't will chime in here. I at least hope that it weighs in on my side.

I think with the amount of money I spend to service guys needs here I should be given a just a little leeway by those people who do very little to do so. Of course I could give up posting - it does use up a lot of my time.

DV

And then here comes the giant ego. "Pay me the proper respect or I will leave". There's lots of smart engine builders on here who can take criticism and who don't use this forum as blatant advertising.

JMO,

paulie

[digger]

How well does 87 octane work in real life on a build like this ? It's fine to tune on dyno under ideal conditions but stinking hot day, heat soaked engine when the engine gets lugged around more than it should is there enough safety margin to cope with that ?

Digger,

You have some good points here but I think some of them you'll able to answer yourself when I say that we test on 87 octane fuel so that we can, with a reasonable degree of certainty, know that it will run just fine on 91 – 93 octane fuel.

The big issue here is looking after engine cooling- a big radiator is a must and engine temperatures need to be kept at or below 170 F. Also good engine oil is needed and even then that should not be run over about 210° F.

DV

I've always wondered if a you keep coolant and air temp fed to the engine the same whether a lower cr with better trapping efficiency was less prone to knock than a higher cr engine that wasn't as good at trapping assuming they both made the same BMEP.

It's been pointed out by others that temperature is more important than static CR as far as knock Is concerned.

[SchmidtMotorWorks]

This is the engine tech section, not the I have a book and engine for sale section. Play it anyway you want, everyone else has enough respect not to do it, IMHO.

This^^^

There are two types of readers of the 128 formula.

1. Those that think it is great

2. Those that understand how a formula is derived and what a polynomial fit looks like.

And you're less than obvious point is?

DV

We have covered this before:

You claimed that you developed the formula by "polynomial" fit; the problem with that claim is, your formula is not what the result of a polynomial fit looks like is when a reasonable set of variables and data are used.

A polynomial fit formula would scale, your formula doesn't.

You can promote a formula to people that don't have have enough experience with mathematics to recognize BS when they see it, but don't expect people that do understand it to pretend it is what you claim it is.

[hoffman900]

This^^^

There are two types of readers of the 128 formula.

1. Those that think it is great

2. Those that understand how a formula is derived and what a polynomial fit looks like.

And you're less than obvious point is?

DV

We have covered this before:

You claimed that you developed the formula by "polynomial" fit; the problem with that claim is, your formula is not what the result of a polynomial fit looks like is when a reasonable set of variables and data are used.

A polynomial fit formula would scale, your formula doesn't.

You can promote a formula to people that don't have have enough experience with mathematics to recognize BS when they see it, but don't expect people that do understand it to pretend it is what you claim it is.

From a purely technical standpoint, I agree with Jon.

Take away the emotions. Take away everything but the equation being exactly about the math, and Jon is right.

It’s okay. Scientists and engineers are wrong all the time, they take the criticism, go back to the drawing board, and keep trying. Outside of SAE and other academic journals, there are no peer review for 100% of automotive articles written. I’d like to think the break down of the topic and discussion here is as close as we can get for the average enthusiast. Instead of everyone getting all huffy-puffy, why don’t we actually talk about fitting data to an equation like it’s done in academic, science, and engineering circles?

My 2 cents.

[GARY C]

After careful consideration I am going to have to join the anti DV crowd, it turns out that he is to blame for my years of debt and fast cars.
If it wasn't for an article he wrote in the 80's I would have had more money to spend on drugs and alcohol but thanks to him all I have to show for all those years is a shop, several engines, a bunch of go fast parts, a race car, 2 street cars, mill/lathe and a flow bench.

Anyone who would sell a book for $25.00 that tells you everything you need to know about building a particular engine family and then have the audacity to include 10 dyno proven builds is clearly an evil capitalist just out to take everyone's money.

Here is the 2 part article and like a dumb a$$ I followed what it said to the best I could afford and ended up with a stupid street car that went to the track running 8.0 eight/12.40 quarter on motor and 7.60/11.70 on 100 shot.

Then 20 years later the capitalist SOB gives me the car out of the article and wont take my money, you know someone like that is up to no good and can't be trusted.

[Carnut1]

Screenshot_2018-05-08-19-27-03.png

Dart 227cc cnc flows from Dart

[hoffman900]

How well does 87 octane work in real life on a build like this ? It's fine to tune on dyno under ideal conditions but stinking hot day, heat soaked engine when the engine gets lugged around more than it should is there enough safety margin to cope with that ?

Digger,

You have some good points here but I think some of them you'll able to answer yourself when I say that we test on 87 octane fuel so that we can, with a reasonable degree of certainty, know that it will run just fine on 91 – 93 octane fuel.

The big issue here is looking after engine cooling- a big radiator is a must and engine temperatures need to be kept at or below 170 F. Also good engine oil is needed and even then that should not be run over about 210° F.

DV

I've always wondered if a you keep coolant and air temp fed to the engine the same whether a lower cr with better trapping efficiency was less prone to knock than a higher cr engine that wasn't as good at trapping assuming they both made the same BMEP.

It's been pointed out by others that temperature is more important than static CR as far as knock Is concerned.

Yes. This, mixture motion, ignition tunability, and mixture quality. This is why all your sportbike engines are running 12.5-13.5:1 compression on pump gas, some with very large bore sizes and a ton of rpm (10,000+)

[digger]

And you're less than obvious point is?

DV

We have covered this before:

You claimed that you developed the formula by "polynomial" fit; the problem with that claim is, your formula is not what the result of a polynomial fit looks like is when a reasonable set of variables and data are used.

A polynomial fit formula would scale, your formula doesn't.

You can promote a formula to people that don't have have enough experience with mathematics to recognize BS when they see it, but don't expect people that do understand it to pretend it is what you claim it is.

From a purely technical standpoint, I agree with Jon.

Take away the emotions. Take away everything but the equation being exactly about the math, and Jon is right.

It’s okay. Scientists and engineers are wrong all the time, they take the criticism, go back to the drawing board, and keep trying. Outside of SAE and other academic journals, there are no peer review for 100% of automotive articles written. I’d like to think the break down of the topic and discussion here is as close as we can get for the average enthusiast. Instead of everyone getting all huffy-puffy, why don’t we actually talk about fitting data to an equation like it’s done in academic, science, and engineering circles?

My 2 cents.

Generally speaking there is nothing wrong with curve fitting like David has done if the bounds are clear and assumptions stated.
It's the same that complicated curves can sometimes be approximated to be linear within certain ranges.

[Scotthatch]

Almost don't need the chart on the head it's a 23 degree head most well done ported are about the same ....if you figure the used cfm on the engine it 340 cfm so with 309 cfm in the head that's a port efficiency of 110 % so to get that you are looking at like a 270 to 275 @ .050 cam ...

[GARY C]

And you're less than obvious point is?

DV

We have covered this before:

You claimed that you developed the formula by "polynomial" fit; the problem with that claim is, your formula is not what the result of a polynomial fit looks like is when a reasonable set of variables and data are used.

A polynomial fit formula would scale, your formula doesn't.

You can promote a formula to people that don't have have enough experience with mathematics to recognize BS when they see it, but don't expect people that do understand it to pretend it is what you claim it is.

From a purely technical standpoint, I agree with Jon.

Take away the emotions. Take away everything but the equation being exactly about the math, and Jon is right.

It’s okay. Scientists and engineers are wrong all the time, they take the criticism, go back to the drawing board, and keep trying. Outside of SAE and other academic journals, there are no peer review for 100% of automotive articles written. I’d like to think the break down of the topic and discussion here is as close as we can get for the average enthusiast. Instead of everyone getting all huffy-puffy, why don’t we actually talk about fitting data to an equation like it’s done in academic, science, and engineering circles?

My 2 cents.

I always wondered why if the end result gives you what you are looking for then why are the numbers that get you there wrong?

I never understood why some get so upset because someone else simplifys a problem.

[hoffman900]

We have covered this before:

You claimed that you developed the formula by "polynomial" fit; the problem with that claim is, your formula is not what the result of a polynomial fit looks like is when a reasonable set of variables and data are used.

A polynomial fit formula would scale, your formula doesn't.

You can promote a formula to people that don't have have enough experience with mathematics to recognize BS when they see it, but don't expect people that do understand it to pretend it is what you claim it is.

From a purely technical standpoint, I agree with Jon.

Take away the emotions. Take away everything but the equation being exactly about the math, and Jon is right.

It’s okay. Scientists and engineers are wrong all the time, they take the criticism, go back to the drawing board, and keep trying. Outside of SAE and other academic journals, there are no peer review for 100% of automotive articles written. I’d like to think the break down of the topic and discussion here is as close as we can get for the average enthusiast. Instead of everyone getting all huffy-puffy, why don’t we actually talk about fitting data to an equation like it’s done in academic, science, and engineering circles?

My 2 cents.

Generally speaking there is nothing wrong with curve fitting like David has done if the bounds are clear and assumptions stated.
It's the same that complicated curves can sometimes be approximated to be linear within certain ranges.

Right, exactly, but it wasn't initially advertised as such and that's where Jon is coming from in regards to him and David's initial argument on here (another thread).

Maybe I'm a robot, wouldn't be the first time I've been told as such, but I could care less what someone has done. I base their contributions on exactly what they are proposing at that given time. Has David contributed a lot to the sport? Absolutely. Does he have a good reputation amongst many enthusiasts? Absolutely. Does that make him infallible? No.

Is 128 wrong? Only when, as Digger correctly stated, it is applied to everything but the very narrow range that it works for (pump gas, 400ci+/-, single carbureted, 2 valve, V8). It wasn't initially advertised as such and that's where the "trolls" are coming form. This is was so obvious in the original thread that I'm blown away when people don't see it this way. People need to start taking a 20,000ft view of things posted on this site...

[Scotthatch]

How well does 87 octane work in real life on a build like this ? It's fine to tune on dyno under ideal conditions but stinking hot day, heat soaked engine when the engine gets lugged around more than it should is there enough safety margin to cope with that ?

Digger,

You have some good points here but I think some of them you'll able to answer yourself when I say that we test on 87 octane fuel so that we can, with a reasonable degree of certainty, know that it will run just fine on 91 – 93 octane fuel.

The big issue here is looking after engine cooling- a big radiator is a must and engine temperatures need to be kept at or below 170 F. Also good engine oil is needed and even then that should not be run over about 210° F.

DV

This worries me a little ..... testing with lower fuel is one thing but engine temp of 170? And oil under 210? That's not even going to drive the moisture from the oil and where I live good luck keeping the temperature that low ...

It kinda like the idea of reverse flow on the engine coolant

[GARY C]

How well does 87 octane work in real life on a build like this ? It's fine to tune on dyno under ideal conditions but stinking hot day, heat soaked engine when the engine gets lugged around more than it should is there enough safety margin to cope with that ?

Digger,

You have some good points here but I think some of them you'll able to answer yourself when I say that we test on 87 octane fuel so that we can, with a reasonable degree of certainty, know that it will run just fine on 91 – 93 octane fuel.

The big issue here is looking after engine cooling- a big radiator is a must and engine temperatures need to be kept at or below 170 F. Also good engine oil is needed and even then that should not be run over about 210° F.

DV

This worries me a little ..... testing with lower fuel is one thing but engine temp of 170? And oil under 210? That's not even going to drive the moisture from the oil and where I live good luck keeping the temperature that low ...

It kinda like the idea of reverse flow on the engine coolant

170 to 180 coolant may be possible but from what I have seen on oil is 230 to 250.