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Old 19 Sep 2007, 16:34 (Ref:2018082)   #31
Bob Riebe
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You are correct rod-angle is incredibly important as to reduced loads on the piston, which reduces friction etc., but then long stroke also means the piston reaches a higher speed, and forces on the piston when it reaches TDC & BDC are greater (theoretically more destructive [the old BOTT Harley builders were thankful that engine vibration {causing discomfort and reduced vehicle control} limited throttle use more than anything, as forces exerted on those pistons made it amazing at rpm's that they were actually capable of achieving]) than those of a short-stroke engine, and no matter how one looks at it, if a piston moves three inches, it has less drag than one moving four inches, even with oil making a fluid barrier between metal componnents.

I also fully realize that many drag racing engines of over eight hundred inches now hit rpms in the eight thousand range, or more, but that is not quite the same as forcing a long stroke engine to do it for twentyfour hours.

The intake design can affect HP, but it is more important in the power curve.
As straight runners, in theory, work better for high rpms, the lack of air caused by the restrictors will negate a great deal of any advantage the straigt runners possible on a P car could have.

Last edited by Bob Riebe; 19 Sep 2007 at 16:40.
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Old 19 Sep 2007, 20:01 (Ref:2018232)   #32
knighty
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sorry bob, I was being gentle in my previous post, based on your last post I'm prepared to say that your now fundamentally wrong, sorry :-/ .......just because the piston travels further dosent mean it will induce more friction.......the reason engine designers (cough: people like me) go the short stroke route is to achieve a VERY high rod to stroke ratio, which drastically reduces piston side loading, and therefore a drastic reduction in piston friction, but this is negated somewhat by the high revving nature of these engines (due to the short stroke) which causes a shed load of friction in itself........this is the wrong way to go for a LMP1 restrictor engine as the restrictor will not permit the massive air flow required for very high RPM, as people have found when they tried to convert 5.8L NASCAR based engines to 6.0 LMP1 restrictor motors.

the piston inertia loadings at BDC and TDC are no problem, I have designed long stroke cranks, rods and pistons before, and it will be fine as long as you do the bearing load calculations correct, and select the correct bearing materials.......its certainly not destructive

the potential torsional vibration issue is easily fixed, even for the low end engine builders, as the viscous torsional crank dampers on the market are great pieces of kit at sensible cost

the reason the Katech Corvette engine makes such good power is it was designed from the outset to rev very low for reduced friction, and for its size, the stroke is quite big at around 96 to 98mm (I have the exact figure at work), this in turn reduces the friction, as friction is directly proportional to the rotational speed of the engine, as the faster the crank rotates, the more loading it exerts on the main bearings, therefore the more friction it will create.

other great examples of low revving long stroke restrictor engines are 2 Litre F3 motors, and the Ford-Elan 7 Litre GT1 engine as used in the Saleens........that thing had a stroke over 100mm and developed over 600bhp with about 850Nm of torque......all great examples proving long stroke works very well for NA restrictor engines.

believe me, a staright inlet runner aimed at the back of the valve, with a narrow runner to valve angle, is the holy grail of any engine, no matter the operating speed......... for a head designed in the 60's, the Gurney-Weslake heads produced 520bhp from 5 litres at about 7200rpm........even by todays standards thats still great for a tuned pushrod motor

Last edited by knighty; 19 Sep 2007 at 20:04.
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Old 19 Sep 2007, 20:24 (Ref:2018252)   #33
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Originally Posted by knighty
sorry bob, I was being gentle in my previous post, based on your last post I'm prepared to say that your now fundamentally wrong, sorry :-/ .......just because the piston travels further dosent mean it will induce more friction.......the reason engine designers (cough: people like me) go the short stroke route is to achieve a VERY high rod to stroke ratio, which drastically reduces piston side loading, and therefore a drastic reduction in piston friction, but this is negated somewhat by the high revving nature of these engines (due to the short stroke) which causes a shed load of friction in itself........this is the wrong way to go for a LMP1 restrictor engine as the restrictor will not permit the massive air flow required for very high RPM, as people have found when they tried to convert 5.8L NASCAR based engines to 6.0 LMP1 restrictor motors.

the piston inertia loadings at BDC and TDC are no problem, I have designed long stroke cranks, rods and pistons before, and it will be fine as long as you do the bearing load calculations correct, and select the correct bearing materials.......its certainly not destructive

the potential torsional vibration issue is easily fixed, even for the low end engine builders, as the viscous torsional crank dampers on the market are great pieces of kit at sensible cost

the reason the Katech Corvette engine makes such good power is it was designed from the outset to rev very low for reduced friction, and for its size, the stroke is quite big at around 96 to 98mm (I have the exact figure at work), this in turn reduces the friction, as friction is directly proportional to the rotational speed of the engine, as the faster the crank rotates, the more loading it exerts on the main bearings, therefore the more friction it will create.

other great examples of low revving long stroke restrictor engines are 2 Litre F3 motors, and the Ford-Elan 7 Litre GT1 engine as used in the Saleens........that thing had a stroke over 100mm and developed over 600bhp with about 850Nm of torque......all great examples proving long stroke works very well for NA restrictor engines.

believe me, a staright inlet runner aimed at the back of the valve, with a narrow runner to valve angle, is the holy grail of any engine, no matter the operating speed......... for a head designed in the 60's, the Gurney-Weslake heads produced 520bhp from 5 litres at about 7200rpm........even by todays standards thats still great for a tuned pushrod motor
You have nothing to apologize for if engine building has proceeded (which I guess is obvious because of the rpms achieved by some drag racing engines) as you have stated, please give us the facts.
It has been a long time since I worked on the internals of an engne or was in school so your informations are welcomed, not otherwise.

As I have recently read some articles in which engine builder still have doubts about speed attained by pistons in some bore/stroke ratios, are your feelings now the accepted norm or are there still divided camps (there always are some opposing views no matter what) or have piston acceleration-deceleration matters been negated by improved products?
Bob
PS--Don't forget the G/W numbers was for alcohol with nitro.
From what I remember in qualifying mixture it produced around 540 HP, but even at that it was impressive for that time no matter the fuel mixture.

Do you have anty idea of what the top constant rpms actually recorded in a US push-rod engine, that did not blowup is?
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Old 19 Sep 2007, 22:02 (Ref:2018336)   #34
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Quote:
Originally Posted by knighty

the reason the Katech Corvette engine makes such good power is it was designed from the outset to rev very low for reduced friction, and for its size, the stroke is quite big at around 96 to 98mm (I have the exact figure at work), this in turn reduces the friction, as friction is directly proportional to the rotational speed of the engine, as the faster the crank rotates, the more loading it exerts on the main bearings, therefore the more friction it will create.
2006 Corvette Engine Specifications
2006 Corvette C6.R
Displacement (L / ci) 7.0 / 427
Horsepower 590 @ 5400 rpm
Torque (lb-ft) 640 @ 4400 rpm
Bore diameter
(mm / in) 106.2 / 4.180
Crankshaft stroke
(mm / in) 98.42 / 3.875
Deck height
(mm / in) 235 / 9.24
"V" angle (deg) 90
Cylinder bore spacing
(mm / in) 111.7 / 4.40
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Old 19 Sep 2007, 22:59 (Ref:2018371)   #35
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Originally Posted by knighty

the reason the Katech Corvette engine makes such good power is it was designed from the outset to rev very low for reduced friction, and for its size, the stroke is quite big at around 96 to 98mm (I have the exact figure at work), this in turn reduces the friction, as friction is directly proportional to the rotational speed of the engine, as the faster the crank rotates, the more loading it exerts on the main bearings, therefore the more friction it will create.



Quote:
Originally Posted by AU N EGL
2006 Corvette Engine Specifications
2006 Corvette C6.R
Displacement (L / ci) 7.0 / 427
Horsepower 590 @ 5400 rpm
Torque (lb-ft) 640 @ 4400 rpm
Bore diameter
(mm / in) 106.2 / 4.180
Crankshaft stroke
(mm / in) 98.42 / 3.875
Deck height
(mm / in) 235 / 9.24
"V" angle (deg) 90
Cylinder bore spacing
(mm / in) 111.7 / 4.40
Knighty:
This is not to say that the Chevy boys have not designed to work with lower revs. as high ones on an engine that already has small ports to work with the restrictor do nothing when only x amount of air can go through by the laws of physics, but a bore of 4.18 is not small with 4.40 bore centers.

I would say how the rod journals, are located on the crankshaft and journal size are of as great of importance here than merely the stroke.
Actually lower revs are not a choice but a necessity again as I said above, without a blower or ram-air you can only get so much through a hole of x diameter and I am sure the sight line on the factory heads would make an engine builder of even twenty years ago go "oooooooh, sweeeeeet."

I am not countering what you said but I see nothing really odd about the bore/stroke ratio of this engine; now if it was under-square, that would really get my attention.
Bob
PS--Now I do not know what the HP number actually represents, if it is peak or just a number that is there to have one.
It is odd though.
It does show how many ponies this engine puts out about the time when the Audi is peaking.

Last edited by Bob Riebe; 19 Sep 2007 at 23:06.
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Old 20 Sep 2007, 08:33 (Ref:2018569)   #36
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Some times I think I should return to daily drinking of Tequila as I seem to operate better with it, but I just realized that the race block has a shorter stroke than the street block, so I would not say it is favoring "long stroke."

Tom if I remember correctly the current race block is linerless, do you know material they use?
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Old 20 Sep 2007, 11:05 (Ref:2018787)   #37
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Hi bob, interesting discussion this one………correct, they reduced the stroke in order to reduce the piston side loadings as per my notes above, therefore reduced friction = more power.........they cant get too clever with the standard block, as they MUST use a factory cylinder block, as per the ACO rules.......hmmmm, dont mention the C5R specially cast blocks!!!!

ref the liners, they fully machined out the iron liners, and nicasil coated to the parent cast ali of the cylinder block

sorry again, Katech and GM DID design for low revs and low friction, this is principally achieved by the big capacity and the long stroke……….Roger Allen did a 12 page technical summary in the may 2007 issue of race tech magazine stating exactly that, low revs = low friction.

believe me, the 7 litre LS7R and Elan GT1 7 litre race engines are very long stroke for their capacity, going by most US tuning standards, particularly Nascars…….heres the proof, lets compare the bore to stroke ratios

Corvette LS7R: 4.185" bore / 3.875 stroke = 1.08

Elan/Saleen GT1 4.125 / 4 = 1.03

5.8 NASCAR: 4.125 / 3.250 = 1.28

Both the Corvette and Elan 7 litre motors produce 640lb/fs (860Nm) of torque……..thats a ferocious amount of torque for a gasoline engine

Yes I'm comparing 5.8 litres to 7 litres, but it’s the bore to stroke ratio trend that drastically changes for a heavily restricted GT1 / LMP1 engine……..the nascar motor has a much bigger bore, for the stroke, as they are chasing power and revs, they don’t necessarily need the torque as they spend nearly all their life at max power on ovals……..acelleration out of a tight corner for a nascar engine is not really a consideration, otherwise it would compromise the top end power.

The reason the Corvette regularly dusted the Aston martins, was because the astons just couldn’t compete with corvette on terms of torque, hence the restrictor rows, but thet still didn’t fix things, as at the end of the day, the aston was 5 litres, and therefore 2 litres smaller!……..to compare the Corvette to the Audis is like an apples to banannas comparsion……..Aston have the wrong engine and they know it……..I'm hearing they want to take the 5 Litre V12 LMP1 racing……..I hope they remember the lessons learned against Corvette and go the biggest capacity possible (6 litres) and go long stroke, as it wil rev lower.

all the best :-)

Last edited by knighty; 20 Sep 2007 at 11:09.
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Old 20 Sep 2007, 11:23 (Ref:2018798)   #38
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Originally Posted by knighty
The reason the Corvette regularly dusted the Aston martins, was because the astons just couldn’t compete with corvette on terms of torque, hence the restrictor rows, but thet still didn’t fix things, as at the end of the day, the aston was 5 litres, and therefore 2 litres smaller!
I must be confused, but the Aston Martin DBR9 has always had a 6.0 V12
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Old 20 Sep 2007, 11:54 (Ref:2018829)   #39
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DBR9 engine
Quote:
Engine:

All alloy, quad overhead camshaft, 48-valve Aston Martin Racing V12 engine.
Dry sump lubrication system, 2 x 31.2mm air restrictors.
ECU/Data system:
Pi Data system, Pectel engine ECU
Capacity: 6.0 litres
Power: approximately 600 bhp
Torque: > 700 Nm
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Old 20 Sep 2007, 12:04 (Ref:2018838)   #40
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sorry for the bumb steer, I thought it was 5 litres.......but the fact still remains, aston know their engine is too small for GT1 competition against the Corvettes 7 litres........more capacity = more torque.......long stroke = more torque at lower revs.......

In which case, I dare say the Aston V12 will make reasonable LMP1 engine……..it certainly worked for the BMW's back in 99!

Just googled it…...Aston is a 5935cc…….bore of 89mm…….stroke of 79.5…….hmmmm.....not the best starting point, as they will need to rev it harder due to the over squareness, but it could be worse!


I heard somewhere Katech have an 8 litre version of the LS7 on the drawing board.........just incase aston or the Dodge viper start challenge their supremicy
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Old 20 Sep 2007, 12:15 (Ref:2018848)   #41
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I heard somewhere Katech have an 8 litre version of the LS7 on the drawing board.........just incase aston or the Dodge viper start challenge their supremicy
Drawing Board ? um nooo

Warhawk Block LS7X

http://www.gmhightechperformance.com...iew/index.html
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Old 20 Sep 2007, 13:46 (Ref:2018918)   #42
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Drawing Board ? um nooo

Warhawk Block LS7X

http://www.gmhightechperformance.com...iew/index.html
I was gouing to say CATIA / Pro Engineer / Auto CAD etc……but thought someone would say "whats that"……..anyway, yeah I have looked at those warhawk blocks before and they are certainly a better choice than the C5R, the reason being they have more external "meat", that would lend themselves very well to being fully stressed in an LMP1 application…….but they would still need a fair amount of the block skirt machined off, to the same height as the main cap split, which would allow a 1 piece billet sump with integral main caps, this would make the engine much stiffer, lighter and tidyer, and most important of all………allow a sensible dry sump scavenge system to be packaged for the lowest engine mounting position possible.

Very logical thinking in re-working the lube system, very good modification and power save for the oil pump

Last edited by knighty; 20 Sep 2007 at 13:56.
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Old 20 Sep 2007, 16:43 (Ref:2019050)   #43
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Quote:
Originally Posted by knighty
Hi bob, interesting discussion this one………correct, they reduced the stroke in order to reduce the piston side loadings as per my notes above, therefore reduced friction = more power.........they cant get too clever with the standard block, as they MUST use a factory cylinder block, as per the ACO rules.......hmmmm, dont mention the C5R specially cast blocks!!!!

ref the liners, they fully machined out the iron liners, and nicasil coated to the parent cast ali of the cylinder block

sorry again, Katech and GM DID design for low revs and low friction, this is principally achieved by the big capacity and the long stroke……….Roger Allen did a 12 page technical summary in the may 2007 issue of race tech magazine stating exactly that, low revs = low friction.

believe me, the 7 litre LS7R and Elan GT1 7 litre race engines are very long stroke for their capacity, going by most US tuning standards, particularly Nascars…….heres the proof, lets compare the bore to stroke ratios

Corvette LS7R: 4.185" bore / 3.875 stroke = 1.08

Elan/Saleen GT1 4.125 / 4 = 1.03

5.8 NASCAR: 4.125 / 3.250 = 1.28
all the best :-)
I do not disagree with the long stroke/low friction as it is the only method they can use to gain an advantage with the crippling effect the restrictors have on standard hot rodding techniques.

I would say on four forty bore centers, without iron liners, Chevy and Katech "tuned" not designed for the bore stroke ratio they are pretty much confined to, as on four forty bore centers, minus iron liners, which are stronger than aluminum walls they cannot go much thinner and have practical safety margin in an engine designed to last a twenty four hour race
(I am well aware that some engine builders, depending on application, are taking cylinder walls a good deal less than twohundred thousandths, depending on make of engine and rod length.)

Remember Dodge was forced to quit using the true stock based engine block in NASCAR as its thicker cyl. walls gave it what NASCAR considered an unfair advantage.
Instead they were forced to switch to the block created originally for sprint car racing.

The crippling restraints of the small bore centers is one of the reasons Ford is bringing out the Hurricane engine, with bore centers rumored to be at least four fifty and possibly four fiftyfive.

What compression ratio are they running on the bunny pee gasoline?
Bob
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Old 20 Sep 2007, 16:50 (Ref:2019055)   #44
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Originally Posted by AU N EGL
Drawing Board ? um nooo

Warhawk Block LS7X

http://www.gmhightechperformance.com...iew/index.html
Some of the hi-po mags have hinted at the possibility Chevy has considered to actually built LS based engines with an increased bore spacing.
But as far as I know it is rumor.

Bob
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Old 20 Sep 2007, 17:28 (Ref:2019086)   #45
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Hey knighty, about the ridiculously small air restictors in GT1 favoring low reving engines as of nature. What happend to the electronic restrictors FIA tested at the end of the 2005 FIA-GT season in the Ferrari 550? And what exactly was those restrictors? It was ment to save costs as with this little air they are getting now the engines needs to be rebuilt quite frequently, and they cost so much to develope, so (basicly) unlimited air but electornic restictors would save costs and make it easier for peformance balancing. And also, it would take away the unfair advantage of naturally low reving engines.

Why did this die out? I though the test was successful!
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