16v Intake Manifold Study and Prototype
Can't wait!
01-16-2009, 08:37 AM
#62
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Todd peaked outside his garage yesterday and saw his shadow. So I think that means six more weeks of winter?
01-16-2009, 10:55 AM
#64
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Just my question : i'm i right that such manifold is ideal for FI applications, but for a NA engine , the ITB are "always" the best solution ? In other words, could a manifold ever have the flow of ITB with good design lenghts and trumpets ?
I installed ITB's and velocity stacks on a 1971 Corvette with a built small block on it years ago, and that sucker wouldnt idle, had a mild mid-range, and an incredible top end. I was young and dumb, and could not tune it in with the tools at the time.
Things have gotten better, and with a modern engine management system I am sure that this could be improved. However, the general reputation of ITB's in street applications are poor for the same reasons: that the bottom end suffers to favor the top end.
Yes, ITB's with short stacks will produce max HP at max RPM at WOT when compared to a single-plane or dual-plane manifold. But, as road-racers, its often felt that we spend more time between 4,000 and 6,000 rpm than at 6500; and more time at partial throttle than at WOT.
For that, carefully tuned runners and a plenum to match provide better throttle response and power to pull out of the corners in the mid-range.
I certainly wouldn't go dismantling your sweet ITB setup as a result of this post, however. Try it and see. Based on your exhaust scavenging, your camshaft profiles, your gearing, and tire diameters - you may have the combination that you like. Try it and see.
01-16-2009, 12:10 PM
#65
01-16-2009, 12:52 PM
#66
Three Wheelin'
Barry,
I installed ITB's and velocity stacks on a 1971 Corvette with a built small block on it years ago, and that sucker wouldnt idle, had a mild mid-range, and an incredible top end. I was young and dumb, and could not tune it in with the tools at the time.
Things have gotten better, and with a modern engine management system I am sure that this could be improved. However, the general reputation of ITB's in street applications are poor for the same reasons: that the bottom end suffers to favor the top end.
Yes, ITB's with short stacks will produce max HP at max RPM at WOT when compared to a single-plane or dual-plane manifold. But, as road-racers, its often felt that we spend more time between 4,000 and 6,000 rpm than at 6500; and more time at partial throttle than at WOT.
For that, carefully tuned runners and a plenum to match provide better throttle response and power to pull out of the corners in the mid-range.
I certainly wouldn't go dismantling your sweet ITB setup as a result of this post, however. Try it and see. Based on your exhaust scavenging, your camshaft profiles, your gearing, and tire diameters - you may have the combination that you like. Try it and see.
I installed ITB's and velocity stacks on a 1971 Corvette with a built small block on it years ago, and that sucker wouldnt idle, had a mild mid-range, and an incredible top end. I was young and dumb, and could not tune it in with the tools at the time.
Things have gotten better, and with a modern engine management system I am sure that this could be improved. However, the general reputation of ITB's in street applications are poor for the same reasons: that the bottom end suffers to favor the top end.
Yes, ITB's with short stacks will produce max HP at max RPM at WOT when compared to a single-plane or dual-plane manifold. But, as road-racers, its often felt that we spend more time between 4,000 and 6,000 rpm than at 6500; and more time at partial throttle than at WOT.
For that, carefully tuned runners and a plenum to match provide better throttle response and power to pull out of the corners in the mid-range.
I certainly wouldn't go dismantling your sweet ITB setup as a result of this post, however. Try it and see. Based on your exhaust scavenging, your camshaft profiles, your gearing, and tire diameters - you may have the combination that you like. Try it and see.
Can the trumpets lenght on ITB be choosen to be optimal for partial throttle , perhaps some HP giving away at WOT ?
i know, i'm a pain the *** with all my questions...
01-16-2009, 01:11 PM
#67
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Individual throttle bodies are better UNLESS they are also Weber carbs.....and slide valves are even better 
! Simply look at Porsche racing engines and development to see the progression. That said 911 engines used individual throttle bodies for many years. Plus the gear spacing is such on a 928 that you ONLY have a maximum RPM drop of about 1,500 RPM when shifted at 6,000 who cares about midrange simply down shift ....that is what the stick is there for.
! Simply look at Porsche racing engines and development to see the progression. That said 911 engines used individual throttle bodies for many years. Plus the gear spacing is such on a 928 that you ONLY have a maximum RPM drop of about 1,500 RPM when shifted at 6,000 who cares about midrange simply down shift ....that is what the stick is there for.
01-16-2009, 01:24 PM
#68
Developer
Thread Starter
Barry,
there are several formulas for the selection of velocity stack length, and even autobiographical books by John Wyer and others cover this. Yes - Porsche, McLaren, Ferrari and many others often carried several sets of velocity stacks with them in the race trailer. Changed the length of the tubes to set up a race car for an individual circuit.
Note when you see photos of open-engine-bay race cars (Can-AM, for example) the incredible diversity in height of velocity stacks. That depeneded on their HP experiments of the moment and their setup for the track they were on. Very common. Also much easier to change velocity stacks from track to track on an ITB setup, almost impossible on a plenumed manifold (if at all).
there are several formulas for the selection of velocity stack length, and even autobiographical books by John Wyer and others cover this. Yes - Porsche, McLaren, Ferrari and many others often carried several sets of velocity stacks with them in the race trailer. Changed the length of the tubes to set up a race car for an individual circuit.
Note when you see photos of open-engine-bay race cars (Can-AM, for example) the incredible diversity in height of velocity stacks. That depeneded on their HP experiments of the moment and their setup for the track they were on. Very common. Also much easier to change velocity stacks from track to track on an ITB setup, almost impossible on a plenumed manifold (if at all).
01-16-2009, 01:51 PM
#69
Rennlist Member
Carl, when do you expect to get this on the dyno? Also, I realize this getting ahead a bit, do you have ballpark price for production pieces.
Very anxiously,
Very anxiously,
01-16-2009, 04:56 PM
#70
Drifting
THANKS Carl for the reply... a bit what i expected.... but can you give a clarification for that sympton ? Does it mean that a engine at midrange NEEDS a little pressure drop in the intake ? Sorry, i just want to see why ... ?
Can the trumpets lenght on ITB be choosen to be optimal for partial throttle , perhaps some HP giving away at WOT ?
i know, i'm a pain the *** with all my questions...
Can the trumpets lenght on ITB be choosen to be optimal for partial throttle , perhaps some HP giving away at WOT ?
i know, i'm a pain the *** with all my questions...
Think of a GM L98 engine from 1985. The one in the C4 Corvettes with the plenum on top and the wrap around runners. Port length was something like 28 inches. That engine made 330 lb-ft @3200 rpm and 230 hp @ 4000 rpm. The LT1 followed in 1992 and had a very similar short block, with a different intake setup: shorter runners/bigger plenum. It made 330 ft-lb @ 4000 rpm and 300 hp @ 5000. Hp and torque shifted up in the rpm range due the different intake setup and peak power went up 30%. Granted the cam was different and the heads flowed better, but those pieces had been optimized to work with the new intake manifold.
01-16-2009, 05:50 PM
#71
Rennlist Member
Beautiful work Carl. This should get you up Pike's Peak in 1st.
And you just added another year to my restification of my 32V. Ths year exhaust, next year intake. You can have the 32V version by next year, right? Stay warm.
Tim
And you just added another year to my restification of my 32V. Ths year exhaust, next year intake. You can have the 32V version by next year, right? Stay warm.
Tim
01-16-2009, 06:16 PM
#72
Very Nice work Carl, from somebody who has also made a simpler version of the 2V manifold it is a stack of work, for everybody's info, a sheetmetal intake for a pro stocker costs $3,100 and they make a lot more of them than Carl will make of this so hopefully everybody can see the work involved to get this done, when I made mine I didn't change the plenum but modified it. I also managed to get the lengths of the runners much closer than Porsche did, whether or not that is a good thing well, I don't know but that's what I did too. I think mine cost about $1000 in material, those tubes aren't cheap.
For my bigger engine the 6.0 litre I will use ITB, I have a new head design at the shop at the moment and we will be testing that port, hopefully the last design, if I can fit it I plan on having variable trumpets in a simplified version to what the F1 cars use, changing the runner lengths makes around a 5% difference on a 600 hp engine. Kinsler did a test and their engine did 610 hp with long stacks and 640 hp with short stacks.
Greg
Greg
For my bigger engine the 6.0 litre I will use ITB, I have a new head design at the shop at the moment and we will be testing that port, hopefully the last design, if I can fit it I plan on having variable trumpets in a simplified version to what the F1 cars use, changing the runner lengths makes around a 5% difference on a 600 hp engine. Kinsler did a test and their engine did 610 hp with long stacks and 640 hp with short stacks.
Greg
Greg
01-17-2009, 10:07 PM
#75
Race Director
Barry,
I installed ITB's and velocity stacks on a 1971 Corvette with a built small block on it years ago, and that sucker wouldnt idle, had a mild mid-range, and an incredible top end. I was young and dumb, and could not tune it in with the tools at the time.
Things have gotten better, and with a modern engine management system I am sure that this could be improved. However, the general reputation of ITB's in street applications are poor for the same reasons: that the bottom end suffers to favor the top end.
Yes, ITB's with short stacks will produce max HP at max RPM at WOT when compared to a single-plane or dual-plane manifold. But, as road-racers, its often felt that we spend more time between 4,000 and 6,000 rpm than at 6500; and more time at partial throttle than at WOT.
For that, carefully tuned runners and a plenum to match provide better throttle response and power to pull out of the corners in the mid-range.
I certainly wouldn't go dismantling your sweet ITB setup as a result of this post, however. Try it and see. Based on your exhaust scavenging, your camshaft profiles, your gearing, and tire diameters - you may have the combination that you like. Try it and see.
I installed ITB's and velocity stacks on a 1971 Corvette with a built small block on it years ago, and that sucker wouldnt idle, had a mild mid-range, and an incredible top end. I was young and dumb, and could not tune it in with the tools at the time.
Things have gotten better, and with a modern engine management system I am sure that this could be improved. However, the general reputation of ITB's in street applications are poor for the same reasons: that the bottom end suffers to favor the top end.
Yes, ITB's with short stacks will produce max HP at max RPM at WOT when compared to a single-plane or dual-plane manifold. But, as road-racers, its often felt that we spend more time between 4,000 and 6,000 rpm than at 6500; and more time at partial throttle than at WOT.
For that, carefully tuned runners and a plenum to match provide better throttle response and power to pull out of the corners in the mid-range.
I certainly wouldn't go dismantling your sweet ITB setup as a result of this post, however. Try it and see. Based on your exhaust scavenging, your camshaft profiles, your gearing, and tire diameters - you may have the combination that you like. Try it and see.
Interesting......ITB intakes are the "best" in terms of pure power....all of the top HP/L engines tend to have them....which also tend to be high RPM screamers like my M3 (8400rpm).....
I did drive Louies ITB setup a couple years ago...& like his dyno chart shows...he is NOT lacking in bottom end torque...but a 6.5L engine helps that a bunch too....
One thing I noticed today on my track shark with stock S4 intake is the ability to pull strongly at low rpms in a higher gear..granted its light (2800lbs) but I got my fastest lap times holding 4th gear, when in theory I could have dropped to 3rd to get better acceleration.... Call me old fashioned...but I love the wide powerband of 928's.....
