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8 Feb 2007, 12:59 (Ref:1836252) | #1 | ||
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Corvette restrictor size & power?
Can someone tell me what restrictor sizes the Pratt & Miller run corvettes use......I can see that they use two (1 per bank) from the under hood picture that I have - but I havent a clue which size they use - I'm lead to believe its a 7 litre engine - known as the LS7....... I know they have/had the edge over the astons due to 6% bigger restrictors allowed for the 2-valve engines........last I heard was this 6% 2-valve rule was being dumped and the corvettes now have lost the 6% restrictor advantage?......is this correct?
also does anyone know what sort of power the katech built motors are producing in the corvettes?......I'm sure this must be common knowledge in the US grape-vine |
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8 Feb 2007, 13:44 (Ref:1836295) | #2 | |||
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LS7.r engine specs: http://www.corvetteracing.com/cars/c...ne_specs.shtml the LS7.r produced about 590 bhp @ 5400 rpms and 640 ftlbs of tq @ 4400 rpms. The restrictor size is not easy to find. But IIRC the two restrictors about about 25mm diameter each. The LS7 thottle body is a single 90 mm with 505 bhp vs the LS7.r has two 25 mm spacers and produces 590 bhp. Katech guesstimates that with out the restrictors the LS7.r would produce around 900 bhp. They have never tested this as the engine was not designed for this type of use. it is just an educated guess. Last edited by AU N EGL; 8 Feb 2007 at 13:49. |
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8 Feb 2007, 15:14 (Ref:1836384) | #3 | |
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I read Alphands C5-R produced 610bhp, the Astons 615/20.
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8 Feb 2007, 15:59 (Ref:1836420) | #4 | ||
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Per 07 aco regs the restrictors should be 30,9mm.
6 liter Aston should have 30,4mm restrictors. |
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8 Feb 2007, 16:05 (Ref:1836429) | #5 | ||
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excellent link AU N EGL!!!!!.....in the drop down menu about the engine, there is a cracking CAD picture of the bare race motor - just what I was looking for as I wanted to see the bare inlet system.
http://www.corvetteracing.com/cars/c6r/engine.shtml 640lb/ft of torque - or 870NM......cripes - thats a serious amount of twist for a normally aspirated 2-valve.......hmmmm.....makes me think they are "under-quoting" the power figure of 590bhp & 5400rpm.....I strongly suspect they are well into 600bhp interesting what they are doing with the LS7.R internals......with a bigger bore and shorter stroke than the standard LS7 road car motor........when it was in 6 litre form as the C6.R they are saying they ran 2 x 31.8mm restrictors.......when they went to 7 litres the revs reduced, giving better fuel economy and greater torque........pretty much as you would expect.......and as Judd are stating the same trend with the new 5.5 V10 Last edited by knighty; 8 Feb 2007 at 16:09. |
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8 Feb 2007, 16:33 (Ref:1836459) | #6 | |||
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8 Feb 2007, 17:11 (Ref:1836490) | #7 | ||
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8 Feb 2007, 17:36 (Ref:1836525) | #8 | |||
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The heads have special small valve, small port set-up just to overcome the restrictors as much as possible. I doubt, very, very much that any of the over-sea engines contain even second to latest cylinder heads. Katech is like most many spy agencies, what they do not tell you is more informative than what they do. One of the items people who build engines for NASCAR teams hate is they are forced to share new ideas with others, at least that is what the rules say. Bob |
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8 Feb 2007, 18:22 (Ref:1836575) | #9 | ||
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Web site posting are only approximate. two years ago there where smaller resticitors, yet new tuning capabilties the engine still made more power.
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8 Feb 2007, 18:28 (Ref:1836583) | #10 | |||
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The corvettes only run a 66-6800 rpm limit. Runn lower RPMS then AMs or the 996s and 997s in GT2. That is what gives that wonderfull deeeeeep booming V8 sound. For those of you on fast internet service, take a ride in a C5R around Le Sarth( sp?) http://www.youtube.com/watch?v=s2vqzJ6EcTM Last edited by AU N EGL; 8 Feb 2007 at 18:31. |
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8 Feb 2007, 20:30 (Ref:1836675) | #11 | |||
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AU N GEL - what the hell are "reverse split cams"......bearing in mind what I do for a living I have never heard of this before!.......tell me more......I have a suspicion this is something to do with there being a depression in the intake runner due to the restrictors. |
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8 Feb 2007, 20:57 (Ref:1836705) | #12 | |||
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"Traditional Splits refers to more exhaust duration and lift then intake (tsp231/237, g5x2 232/450, ect). Reverse split refers to more intake duration and lift then exhaust (TR 230/224, X1 230/227). Single patterns are defined as having both the same intake, exhaust duration, and lift. (TR224, TR220, FM4 226/226). Which cam is better depends on your application." Cam guide Katech is building me a LS7 engine with LS7 heads. Using the GM World Challange cam - 258/258 @ .050 .578/.578 lift, 110 LSA Should run about 650 bhp and 589 ft lbs I have all kinds of charts and graphs about differnt cams and the out put results. Last edited by AU N EGL; 8 Feb 2007 at 21:03. |
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9 Feb 2007, 08:50 (Ref:1837056) | #13 | ||
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very interesting AU N EGL- thanks for the information - with a split reverse cam is there much overlap?.......or any whatsoever?......going by whats said in the link I'm thinking there is none on such a low revving engine as the LS7.R's
sounds quite logical when I think about it, as a 40mm exhaust valve is actually quite small, hence the extra lift and duration would make it flow better for sure. I'm told NASCAR tuners run 40.6mm (1.6") exhausts, and I'm told they struggle getting them to flow properly, but do get away with it and it works.......all in an attempt to use the biggest intake valve possible - which in Nascar is 54.6mm (2.15") ........aparrently 49.15mm (1.935") valve spacing is mandatory in NASCAR, so it keeps valve sizes under control. Surely Katech or GM must have realised the LS is a great platform for a LMP1 motor?.......the restrictor regs favouir it heavity as it will have a 6% restrictor size advantage over the equivalent 4-valve motor |
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9 Feb 2007, 12:22 (Ref:1837275) | #14 | ||
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Here are the heads that were used on the C5R engine. Most likely still used on the LS7R do required casting head numbers to the homlogated C5 in 1998
C5R bare racing cylinder head 355-T7"as-cast" aluminum racing head Professional porting of combustion chamber chambers required No seats, or guides C5R rectangle port design-requires rectangle port intake manifolds Designed for 2.180"/1.625" valves Valve angle revised to 11 degrees, Machined for big bore LS&/C5R race block 210 cc "as-cast" intake ports 70 cc "as-cast" exhaust ports same as production LS6 30 cc "as-cast" combustion chambers All fasteners are metric Valve cover rails have O-ring groove for .125" O-ring Capable of over 800 horsepower GM Part # 12480090 I have asked Katech about a 6 liter LPM1 engine, and their response was they could develope just about anything. Last edited by AU N EGL; 9 Feb 2007 at 12:27. |
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9 Feb 2007, 15:16 (Ref:1837419) | #15 | |||
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Popular Hot Rodding when it did an article on new Chevy heavy duty engines, said that special small port/valve heads, not available to the public, were being used as of 2006. I would like to see what the euro cars are running. Bob |
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9 Feb 2007, 19:59 (Ref:1837598) | #16 | ||
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I have to say - I'm in agreement with bob - I'd be very very surprised to hear they are using such massive size valves on such low revving motor......the LS7 standard heads sound wonderful with huge great valves, but for the low revving LS7.R race motor, they will be well out of place - but I stand to be corrected if anyone wants to spill the beans!
interesting they are a special rectangle inlet port design........but not surprising - the standard LS7 intake port shape looks a horrific start for a race motor.......not surprised they tidied it up with something much smaller and simple...........just a personal opinion based on experience! E UN GEL - well, if the GM-Corvettes get bored of racing by themselves in 2007 - which is looking highly likley at the moment - why not step up a level! - they have been racing corvettes for long enough now - I dare say the sound of a floor trembling 6 litre LS7 LMP1 motor in the back of any LMP1 sports prototype would be more than welcome in both Europe and the US!.......they can make up for the noise that Audi should be making........I dare say Katech have all the parts, they just need to make the engine fully stress-able for a mid-engined sports prototype installation - not hard on an LS7 - its build like a brick out house already! Last edited by knighty; 9 Feb 2007 at 20:07. |
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9 Feb 2007, 20:50 (Ref:1837636) | #17 | ||
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Turns out that is the C5R head, not even close to the LS7r head. rember the r engine uses individural runners too.
Still a low reveing motor( relative) and other cars may be faster, but not more reliable and why they win so much. |
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9 Feb 2007, 20:55 (Ref:1837643) | #18 | |||
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9 Feb 2007, 21:00 (Ref:1837647) | #19 | |||
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Chevy is in racing to A: get the Corvette reputation back; B: Gets its own reputation back. It once used its RWD cars to become the Heartbeat of America but its FWD crap-wagons turned it into, the rental fleet flotsam of america. Originally Chevy beating Dodge was the starting point of that campaign; beating Ferrari in '03 was probably the absolute high point. Entering the P class serves nothing as it would gain no sales recognition, especially as they cannot do a quasi-GTP Corvette as they did twenty years ago; plus the aisnine rules make it a no-win situation. You cannot build a better product as the contrived rules headquarters will eliminate it quickly, so what is the point of trying. Bob |
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9 Feb 2007, 21:10 (Ref:1837651) | #20 | |||
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Peronally, I would like the IMSA to bring back the GTX category, where there was no real cubes limit. As there are top engine builders who can build BB Chevies up to 695 cubes and still be over-square, they could force them to run street gas, and they would still put current LMP horsepower levels to shame. Bob |
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15 Feb 2007, 21:11 (Ref:1842562) | #21 | ||
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Knighty:
I recieved an Aussie mag. recently which the history of the Windsor/Boss engine in Australia, and found out the current Supercar Ford V-8 are Boss 302 derived (there words, but it is the generation 35+ years removed) engine that with a strict 7,500 rpm limit, intakes valves limited to 2.125 inches, and a 10:1 comp. ratio, is still putting out 640 hp at 7,500 rpm and 470 lb. ft of torque at 6,000 rpm. Lord only knows what it would do with another 2,000 rpm, unlimited comp. ratio, and unlimited valve size. Now if the ACO is so paranoid about horsepower, such a limit is far more intelligent than strangling an engine. |
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19 Feb 2007, 13:36 (Ref:1845523) | #22 | ||
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interestibng stuff bob - I calculate 302ci as 4948cc........if they are producing 640bhp thats 128bhp per litre - quite a highly strung motor for a 2-valve per cylinder........which still makes me think a 6.0 LMP1 V8 2-valve motor will produce the beans.........with 470 lb/ft torque I would be interested to know the bore and stroke - seems quite low - I would suspect the stroke is shorter than the bore diameter.......
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19 Feb 2007, 17:14 (Ref:1845634) | #23 | |||
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The Speed World Challange Corvettes use a LS2 6 liter block. 550+ BHP without restrictor and 525 ft tq. a few notes: 2000-7000 rpm range Cam is the GM- Cup cam with 239/251 570/570 106 lsa Here are some details: 2.A.1. OEM Engine Designation: LS-2 2.A.2.Displacement (Max): 6026cc (368ci) 2.A.3. Number of Cylinders: 8 (V-block) 2.A.4. Rev-Limit: Required: (Y / N) Yes 2.A.5. @ RPM See Appendix A 2.A.6. Method: Fuel Cut 2.A.7. Compression Ratio (Max): 12.0:1 2.A.8. Piston Stroke (Max): 92.08mm 2.A.9. Restrictors – (teams are required to be prepared to install these restrictors): % of Reduction: 20, 25, 30, 35, 40 Hole Diameter (mm): 80.5, 77.9, 75.3, 72.6, 69.7 2.A.10. Cylinder Firing Order: 1-8-7-2-6-5-4-3 2.A.11. Direction of Engine Rotation (incl. cams): Clockwise B. CYLINDER BLOCK: Part Number: 12568950 (casting#: 12568952) 2.B.1. Cylinder Block Material: Cast Aluminum 2.B.2. Cylinder Bore (Max): 102.1mm *Note: Includes any allowed overbore, usually 1mm over stock. C. CYLINDER HEAD: Part Number: LS6: 88958622 (casting#: 12564243), LS2: 88958765 (casting#: 12564243) 2.C.1. Cylinder Head Material: Cast Aluminum D. VALVE SYSTEM: 2.D.1. Number of Valves per Cylinder: 2.D.1.a. Intake: 1 2.D.1.b. Exhaust: 1 2.D.2. Valve Head Diameter (Max): 2.D.2.a. Intake: 50.8mm 2.D.2.b. Exhaust: 39.4mm E. INTAKE PORT DIMENSIONS: 2.E.1. At Inlet Manifold Face (Stock): 2.E.1.a. Height: 82.8mm 2.E.1.b. Width: 29.2mm 2.E.2. Intake Port Work Allowed (Yes or No): No 2.E.2.a. Depth from Face: n/a F. EXHAUST PORT DIMENSIONS: 2.F.1. At Exhaust Manifold Face (Stock): 2.F.1.a. Height: 33.8mm 2.F.1.b.Width: 41.7mm 2.F.2. Exhaust Port Work Allowed (Yes or No): No 2.F.2.a. Depth from Face: n/a Source: http://www.world-challenge.com/competitors/vts.php Look under Chevrolet C6 Corvette Z06 or Cadillac CTS-V Both use the LS2 motor not the 7 liter LS7 for Speed World Challange Last edited by AU N EGL; 19 Feb 2007 at 17:16. |
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19 Feb 2007, 22:14 (Ref:1845860) | #24 | ||
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The limit is five liters or 305 but if the BxS must be prod. based it would be the old 4.00x3.00, as both the factory Fords and Chevies used.
I wonder what the Chevy based Holdens are using, as when they used a genuine Holden that five liter had a different BxS unique to Holden; while they are now using an LS based engine, I wonder which BxS they are using. In the Trans-Am before they put a lid on the pot, the 310-311 inch entgines most common in the nineties had alloy valve trains, as large a carb, but not a Domnator as possible. They were turning into the ten thousand range, and horse power was always listed as only 650+ HP with no mention of real numberrs attained, plus the comp. ratio was also open at that time. Some of the T-A engine builders who were also NASCAR builder were experimenting with comp. ratios as high as 17:1 with 15:1 being not out of the ordinary. The street quasi-race 302 engines from both Ford and Chevy were never torque monsters but whereas one could leave the line with a Ford engine with no dramatics, the Z28 302s, even with a idle well over 1,000 rpm were a ***** to get going. Bob |
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20 Feb 2007, 01:58 (Ref:1846005) | #25 | ||
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Besides, why would Chevrolet step into the "Peugeot Charity" class? There's absolutely no reason for any manufacturer to move up when the rules have, are, and will be written to benefit the chosen manufacturer the ACO wants to entice. |
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