Bruce ( Shrinker )

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carby tuning techniques said:
its a proform main body with a stepped downleg booster.
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both are at WOT.
both venturis are on the same side of the engine.
with the holley the combustion on that side is upsetting the flow out of the holley booster.
on the smartcarby it is not.
with the smartcarby the combustion changed dramatically.

i will write something later on about the smartcarby and the main reason that Bruce built them.
 
Nice XD by the way.

Can you remember the difference in idle vacuum between the carbs by any chance?

Greg do you remember Neil Bovey's 308 that Steve Gay did the heads for?
 
Hysteric said:
Nice XD by the way.

Can you remember the difference in idle vacuum between the carbs by any chance?

Greg do you remember Neil Bovey's 308 that Steve Gay did the heads for?
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the idle vacuum was changeable as we changed the tune with both carbs.both carbs would increase the idle vacuum about 2" as the tune was changed with each carb.

yes i remember that 308.a lot of people have loosley copied that combo over the years all over aus.
 
Any ideas on what the port volume would be on those heads? To be honest I think that's what my original combo was based off of but with more cubes for the fact it was a street car or that's what I surmise from the original builders intentions.

Wouldn't be anything like the engine package you offer by any chance :lol:
 
Hysteric said:
Any ideas on what the port volume would be on those heads? To be honest I think that's what my original combo was based off of but with more cubes for the fact it was a street car or that's what I surmise from the original builders intentions.

Wouldn't be anything like the engine package you offer by any chance :lol:
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Port volumes are pretty standard i think.
It was the bowl and valve job mainly.

How do i upload a pdf paper?
 
carby tuning techniques said:
Here is something i wrote for you on Bruce.
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If you have written that for me I am deeply appreciative. Like anything related to this stuff it'll take some time to digest it no doubt.

I know those early small valve heads start at 95cc and to think they run 11's with those is remarkable. Tony Knight has also managed to do amazing things with such a small port.
 
Wow......lots of stuff to unpack in those 3 pages.

"Bruce realised long ago that the majority of engines like and needed a combination of 2 droplet sizes."

Is it right to assume that the 2 differences are what the T-slot and booster provide?
 
Hysteric said:
Wow......lots of stuff to unpack in those 3 pages.

"Bruce realised long ago that the majority of engines like and needed a combination of 2 droplet sizes."

Is it right to assume that the 2 differences are what the T-slot and booster provide?
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Hysteric said:
Wow......lots of stuff to unpack in those 3 pages.

"Bruce realised long ago that the majority of engines like and needed a combination of 2 droplet sizes."

Is it right to assume that the 2 differences are what the T-slot and booster provide?
Click to expand...

P5220225.JPG


P5220223.JPG
 
carby tuning techniques said:
yes that is correct.
However,with the smart carby he would run 2 different size holes in the spreader bars for the mains fuel.this was where the different size droplets come from that i was referring to.
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Thanks Greg these pics are more than I could ever hope for. Is it right to assume the different droplet sizes has to do with the vaporization rate and where and when it takes place during the process? Bruce said this some where in relation to droplet size:

"You have to learn how to balance the speed of vaporization and where it occurs in every engine. They are all different."

Is this what we are discussing here?
 
Hysteric said:
Thanks Greg these pics are more than I could ever hope for. Is it right to assume the different droplet sizes has to do with the vaporization rate and where and when it takes place during the process? Bruce said this some where in relation to droplet size:

"You have to learn how to balance the speed of vaporization and where it occurs in every engine. They are all different."

Is this what we are discussing here?
Click to expand...
with pump unleaded petrol,you have to be real careful with the amount of vaporization that you have on the up stroke (compression).The light vapors that boil at a lower temp have the expensive octanes in them,they can withstand quite a bit of heat energy for a short amount of time.
The higher temp ones are the cheap octanes,they cant withstand as much heat and are designed to go off on the down stroke and in the cats.
When you can control the droplet size you can to some degree adjust this relationship of what vaporizes when.
You still want vaporization and burning to be occurring while the piston is at TDC as it helps the chase down of the piston. Thats why the flame kernel strength is so important and why ignition timing is linked with CO production.
Thats why having mains fuel with different droplet size is key to producing power making CO2.
 
try not to get to caught up in thinking that the small drops come from the transfer and the large from the main boosters.Of course they are different sizes,but if you just think like that you will miss other important goodies.
This is what i find with tuning.
The transfer fuel if its done correct - it really does set the driving style of the vehicle.much vehicle movement for small throttle movement.
It does this by producing a hot cylinder and this is extremely important as it sets up the cylinder condition to take the larger mains fuel droplets.If the cylinders are not nice and hot the mains fuel builds lower cylinder pressure than optimum.
Then comes the mains fuel for constant power production later in the load which requires a mixture of droplet sizes for optimum power production.
The boosters in a Holley do give a few different droplet sizes but its all too big and very hard to control.
Smart carby you can gas the fuel if you want,but that is not what is always required.
you can experiment with making the transfer fuel smaller and experiencing the difference it makes in drving.when it has correct spark timing moving with it,you can get it very good.

On my car i have a 800cfm Holley with straight bar boosters and programmable ignition and this is a plug that is achievable with tuning in those areas.what comes with this plug is smooth power and much vehicle with minimal throttle movement.
This plug is idling around,cruising and WOT runs.it never gets black.

IMG_8371.jpeg
 
carby tuning techniques said:
try not to get to caught up in thinking that the small drops come from the transfer and the large from the main boosters.Of course they are different sizes,but if you just think like that you will miss other important goodies.
This is what i find with tuning.
The transfer fuel if its done correct - it really does set the driving style of the vehicle.much vehicle movement for small throttle movement.
It does this by producing a hot cylinder and this is extremely important as it sets up the cylinder condition to take the larger mains fuel droplets.If the cylinders are not nice and hot the mains fuel builds lower cylinder pressure than optimum.
Then comes the mains fuel for constant power production later in the load which requires a mixture of droplet sizes for optimum power production.
The boosters in a Holley do give a few different droplet sizes but its all too big and very hard to control.
Smart carby you can gas the fuel if you want,but that is not what is always required.
you can experiment with making the transfer fuel smaller and experiencing the difference it makes in drving.when it has correct spark timing moving with it,you can get it very good.

On my car i have a 800cfm Holley with straight bar boosters and programmable ignition and this is a plug that is achievable with tuning in those areas.what comes with this plug is smooth power and much vehicle with minimal throttle movement.
This plug is idling around,cruising and WOT runs.it never gets black.

View attachment 1715851606
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IMG_8163.jpeg


vn carby look.jpeg
 
Thread of the year!!! Thanks Greg for joining up. And sharing all of this information.
 
Quick question.
2C5384DC-5104-4EAF-AE4F-648F32C34D10.jpeg

is this a fuel pressure sensor?
 
carby tuning techniques said:
with pump unleaded petrol,you have to be real careful with the amount of vaporization that you have on the up stroke (compression).The light vapors that boil at a lower temp have the expensive octanes in them,they can withstand quite a bit of heat energy for a short amount of time.
The higher temp ones are the cheap octanes,they cant withstand as much heat and are designed to go off on the down stroke and in the cats.
When you can control the droplet size you can to some degree adjust this relationship of what vaporizes when.
You still want vaporization and burning to be occurring while the piston is at TDC as it helps the chase down of the piston. Thats why the flame kernel strength is so important and why ignition timing is linked with CO production.
Thats why having mains fuel with different droplet size is key to producing power making CO2.
Click to expand...

You do realize there's a lot of info to unpack in that paragraph!

carby tuning techniques said:
The transfer fuel if its done correct - it really does set the driving style of the vehicle.much vehicle movement for small throttle movement.
It does this by producing a hot cylinder and this is extremely important as it sets up the cylinder condition to take the larger mains fuel droplets.If the cylinders are not nice and hot the mains fuel builds lower cylinder pressure than optimum.
Click to expand...

I remember you saying this way back when on SpeedTalk about saturation

The engine runs on the transfer slot fuel first, and its this fuel that saturates the airstream for consistent fuel gassing in the intake tract.
This fuel that comes out of the transfer slot continues to come out quite high in the load settings on some engines and has a profound effect on the amount of combustion completeness that is reached.
To obtain a smooth running set of cylinders you need saturated air going to ALL cylinders.
The transfer fuel can be smaller in droplet size than the fuel that comes out of the main boosters, so it can deliver a different cylinder condition than the booster fuel.
You can choose to have either small droplets or larger blobby fuel drops exiting the transfer slots of a carby,its up to the operating to calibrate the t/slot/ifr/iab so as to achieve well saturated air exiting the carby.
The transfer slot reacts to the vacuum that is under it and the air leak that is on top of it, so all different engine combinations will deliver different amounts and sizes of fuel droplets, and here in lies the saturation level and quality.
Carb sizing plays a huge role in achieving good air saturation out of the transfer slot as well as the camshaft and port sizing.
Very,very little fuel emulsification has taken place at this point, if any at all..

Before I pulled my engine I put a 850 Thermoquad on it that Demonsizzler originally built for AndyF. The most notable difference was the running smoothness and how much quicker it revved.

So is it safe to surmise that transfer slot fueling is critical for flame kernel development and general cylinder conditioning?

I found an interesting paper from Heywood:Early Flame Development and Burning Rates in Spark Ignition Engines and Their Cyclic Variability on JSTOR

This statement from Heywood for me is profound: "It also suggests that cycle by cycle variations in the position and growth rate of the flame kernel at very early times are the very cause of the cycle by cycle fluctuations in the pressure curves for spark ignition engines."
 
Hysteric said:
Before I pulled my engine I put a 850 Thermoquad on it that Demonsizzler originally built for AndyF. The most notable difference was the running smoothness and how much quicker it revved.

So is it safe to surmise that transfer slot fueling is critical for flame kernel development and general cylinder conditioning?
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Thermoquad are very good.the transfer system is very good,better than a Holley.
thats why its smoother and revved quicker.the smaller venturi gets you more vaporization as well,and that is why there is more vaporization at ignition time.possibly.
i say possibly because the droplet size thing is full off pitfalls.It is true that the higher the gas level the less timing is required and normally you would expect more power from more vaporization but the timing needs to be correct for it otherwise it will not.
Ignition strength is critical for flame kernal development.
 
Hysteric said:
This statement from Heywood for me is profound: "It also suggests that cycle by cycle variations in the position and growth rate of the flame kernel at very early times are the very cause of the cycle by cycle fluctuations in the pressure curves for spark ignition engines."
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yes absolutely.
CO production and the amount of it thats left over from the previous bang effects the flame kernal immensely.
Homogenization is key to reduce cycle to cycle variations and the fuel has to be gassed so you can homogenize it.
When you are tuning an engine you are tuning the pressure wave.You want this to be as constant and predictable as you can get it.this is what gives smooth power and smooth lines on graphs.
 
carby tuning techniques said:
Thermoquad are very good.the transfer system is very good,better than a Holley.
thats why its smoother and revved quicker.the smaller venturi gets you more vaporization as well,and that is why there is more vaporization at ignition time.possibly.
i say possibly because the droplet size thing is full off pitfalls.It is true that the higher the gas level the less timing is required and normally you would expect more power from more vaporization but the timing needs to be correct for it otherwise it will not.
Ignition strength is critical for flame kernal development.
Click to expand...

Had an interesting conversation about carb design with Bruce about "Improving" the Holley design and he responded with: "Fix a Holley and it will work like a Carter." That really threw me at the time but after reading up on design and some time spent at the patent office website it started to make more sense.

Back to CO and CO2 and flame kernel development as to your earlier statement:

carby tuning techniques said:
Thats why the flame kernel strength is so important and why ignition timing is linked with CO production.
Thats why having mains fuel with different droplet size is key to producing power making CO2.
Click to expand...

Can you expand on this further.?
 
Hysteric said:
Had an interesting conversation about carb design with Bruce about "Improving" the Holley design and he responded with: "Fix a Holley and it will work like a Carter." That really threw me at the time but after reading up on design and some time spent at the patent office website it started to make more sense.
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yes that would of been a good conversation.
when you get the supersonic air going into idle circuits it smashed up fuel drops to very fine prior to exiting the exit are into the bore.
 
carby tuning techniques said:
yes that would of been a good conversation.
when you get the supersonic air going into idle circuits it smashed up fuel drops to very fine prior to exiting the exit are into the bore.
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Funny you mention that it had a distinct whistle at idle.
 
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