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Old 2 Jan 2018, 11:27 (Ref:3790294)   #3211
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Originally Posted by knighty View Post
Interesting Cadillac will reduce the engine capacity from 6.2L down to 5.5L in an attempt to help IMSA BOP targets.......seems like IMSA and Cadillac had a quiet kitchen discussion and agreed the 6.2L was a bit of a joke and causing everyone an un-needed BOP headache.
I can't help but think there's a weight balance issue here. I'm sure the 5.5 will be lighter, unless it's the same block destroked obviously, and IMSA showed last year that they really do want things as equal as possible(even though it took most of the season to get there), so if they're going to be restricted down anyway they might as well switch to an engine that can create a better overall balance in light of it.
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Old 2 Jan 2018, 11:31 (Ref:3790296)   #3212
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Is this just the 5.5 litre out of the GTE/GTLM Corvette?
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Old 2 Jan 2018, 12:59 (Ref:3790305)   #3213
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LS and LT are basically the same engine design overall, so I doubt there's much of a weight difference. I'm betting it's down to BOP.
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Old 2 Jan 2018, 13:10 (Ref:3790307)   #3214
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Originally Posted by FormulaFox View Post
I can't help but think there's a weight balance issue here. I'm sure the 5.5 will be lighter, unless it's the same block destroked obviously, and IMSA showed last year that they really do want things as equal as possible(even though it took most of the season to get there), so if they're going to be restricted down anyway they might as well switch to an engine that can create a better overall balance in light of it.
even if nissan, cadillac and acura dpi have been set to have a 940kg min. weight, actually is irrelevant because as already stated during last season cadillac and nissan are already about 50kg overweighted. Also riley lmp2 and mazda dpi were overweighted last season.
Guess won't never be confirmed if new cadillac engine is a destroked 6.2L or an updated corvette DP LS9, but I don't expect a considerable weight loss by this swap.

Acura, nissan and cadillac should be in the same torque range now; with acura as the only brand fielded by the closest thing to an official work team (actually don't know if WTR will keep on being supported by GM and dallara like 2017 season.... AXR and SoD won't be for sure).
Is unlikely a cadillac domination like 3/4 of last season.
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Old 2 Jan 2018, 22:18 (Ref:3790381)   #3215
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Just for fun I made some odds for how I see the Prototype class at Daytona
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Old 3 Jan 2018, 02:21 (Ref:3790396)   #3216
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Originally Posted by canaglia View Post
even if nissan, cadillac and acura dpi have been set to have a 940kg min. weight, actually is irrelevant because as already stated during last season cadillac and nissan are already about 50kg overweighted. Also riley lmp2 and mazda dpi were overweighted last season.
Guess won't never be confirmed if new cadillac engine is a destroked 6.2L or an updated corvette DP LS9, but I don't expect a considerable weight loss by this swap.

Acura, nissan and cadillac should be in the same torque range now; with acura as the only brand fielded by the closest thing to an official work team (actually don't know if WTR will keep on being supported by GM and dallara like 2017 season.... AXR and SoD won't be for sure).
Is unlikely a cadillac domination like 3/4 of last season.
Do you know how much slower the cars would be if they were 50kg overweight? Cadillac wouldn't be winning anything if they were that heavy When they say overweight, it's more likely they don't have much leeway with ballast if at all. I have no idea why this figure of 40, 50kg etc. gets thrown around. Do you have a link? Does anyone have a link to this?
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Old 3 Jan 2018, 08:06 (Ref:3790430)   #3217
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canaglia should be qualifying in the top 10 on the gridcanaglia should be qualifying in the top 10 on the grid
When you have so much torque by your side, being a little overweight is not a problem at all. Peugeot 908HDi has always been overweighted and very likely even porsche, audi and toyota lmp1 are over the min. weight.
During 2014-2016 IMSA seasons, DP were 140kg heavier than lmp2, but basically was irrelevant.
About cadillac there is an Angelelli interview after daytona success where he states that car is a bit more powerfull than lmp2 but however heavier because of the larger engine. About esm, before laguna seca race, scott sharp stated that the track fits better for aco lmp2 becasuse are about 50kg lighter than them.

And funny side of the issue, just one years ago, you were the one who speculated about esm car overweight (page 135 of this thread)
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Old 4 Jan 2018, 07:25 (Ref:3790573)   #3218
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Originally Posted by canaglia View Post
When you have so much torque by your side, being a little overweight is not a problem at all. Peugeot 908HDi has always been overweighted and very likely even porsche, audi and toyota lmp1 are over the min. weight.
During 2014-2016 IMSA seasons, DP were 140kg heavier than lmp2, but basically was irrelevant.
About cadillac there is an Angelelli interview after daytona success where he states that car is a bit more powerfull than lmp2 but however heavier because of the larger engine. About esm, before laguna seca race, scott sharp stated that the track fits better for aco lmp2 becasuse are about 50kg lighter than them.

And funny side of the issue, just one years ago, you were the one who speculated about esm car overweight (page 135 of this thread)
Being overweight can vary and of course it's possible. I just have a hard time believing 50kg over is the amount. That would mean they're running around 980kg. They wouldn't be winning with that amount of heft. Torque helps a lot, but if that's the case, the Penske Acura will be a lot quicker because we know from Oreca that chassis is under the minimum weight requirement.

DP vs lmp2 is a different scenario because the former had at least 100 more horsepower. These DPi's are the same lmp2's but with new hardware, they don't have that big of a power advantage. If you have a source that would be nice to read!
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Old 4 Jan 2018, 08:37 (Ref:3790580)   #3219
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let's clear something: oreca 07, along liger and dallara lmp2 with gibson engine under the hood are lighter than 930kg. No doubts about that. Add to this mandatory air conditioning system and you just have some room left for ballast to reach 930kg.
Turbo engines are heavier, require extra cooling devices around it and a more resistant rear subframe structure joint to the monocoque; very likely acura dpi uses a different rear suspensions geometry than standard 07, to make the powertrain fully stressed. The latter is just a my theory of course, but quite realistic I guess. All these modifies make the car much heavier.
Question: Is oreca 07 chassis so light that even if powered by HPD 3.5 V6, the car will remain under 930kg? Perhaps, or maybe not.

About lmp2/DPi, is not so correct. Power gap between lmp2 and dp was in the range of 60hp in 2014 (nissan 500hp lmp2 vs GM/ford about 560hp). From that, dp power was constantly nerfed, until 2016 season where ligiers powered by HPD 3.5L were basically in the same power range power, if not something more.
Real deal for dp was that both riley ford and corvette DP were in 600-640Nm range, 100Nm more than lmp2 nissan, that helped the dp's to be on the edge even if heavier and less aero/chassis developed.
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Old 4 Jan 2018, 11:36 (Ref:3790607)   #3220
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Originally Posted by canaglia View Post
let's clear something: oreca 07, along liger and dallara lmp2 with gibson engine under the hood are lighter than 930kg. No doubts about that. Add to this mandatory air conditioning system and you just have some room left for ballast to reach 930kg.
Turbo engines are heavier, require extra cooling devices around it and a more resistant rear subframe structure joint to the monocoque; very likely acura dpi uses a different rear suspensions geometry than standard 07, to make the powertrain fully stressed. The latter is just a my theory of course, but quite realistic I guess. All these modifies make the car much heavier.
Question: Is oreca 07 chassis so light that even if powered by HPD 3.5 V6, the car will remain under 930kg? Perhaps, or maybe not.

About lmp2/DPi, is not so correct. Power gap between lmp2 and dp was in the range of 60hp in 2014 (nissan 500hp lmp2 vs GM/ford about 560hp). From that, dp power was constantly nerfed, until 2016 season where ligiers powered by HPD 3.5L were basically in the same power range power, if not something more.
Real deal for dp was that both riley ford and corvette DP were in 600-640Nm range, 100Nm more than lmp2 nissan, that helped the dp's to be on the edge even if heavier and less aero/chassis developed.
Do we know that to be true? Seems like something well beyond the idea of DPi, at least to me.
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Old 4 Jan 2018, 13:56 (Ref:3790636)   #3221
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HPD engine can't be stress mounted in the Oreca-Acura because it's a stock block engine. Neither can the GM V8 in the Cadillac or the Nissan in ESM's Ligiers be fully stress mounted. By which I mean bolted directly to the monocoque vs being mounted in a sub-frame.

If you're going to redesign a stock block engine to be fully stress mounted, may as well start from a clean sheet of paper.

The only thing stock on these engines are the basic block and heads, but the basic block and heads aren't designed to be bolted to the tub as an integral member.
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Old 4 Jan 2018, 15:18 (Ref:3790654)   #3222
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HPD engine can't be stress mounted in the Oreca-Acura because it's a stock block engine. Neither can the GM V8 in the Cadillac or the Nissan in ESM's Ligiers be fully stress mounted. By which I mean bolted directly to the monocoque vs being mounted in a sub-frame.

If you're going to redesign a stock block engine to be fully stress mounted, may as well start from a clean sheet of paper.

The only thing stock on these engines are the basic block and heads, but the basic block and heads aren't designed to be bolted to the tub as an integral member.
Are you sure? It's quite common for road going engines to be stress mounted via a bespoke sump and either bespoke cam/rocker covers or mounting plates. Majority of prototypes still have additional supporting frames from the bellhousing to tub for additional support but don't live in a cage. Current p3's are a good example of all this.

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Old 4 Jan 2018, 19:43 (Ref:3790708)   #3223
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MP has some engine related info (semi stressed) in the Caddy

http://www.racer.com/imsa/item/14656...smaller-engine

Also, imsa has a 580hp target.
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Old 4 Jan 2018, 19:49 (Ref:3790710)   #3224
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Semi-stressed to me implies tube frame that ties the engine to the tub. I doubt that the block and heads on any of the stock block engines has been modified enough to be bolted to the monocoque.
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Old 4 Jan 2018, 20:24 (Ref:3790715)   #3225
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MP has some engine related info (semi stressed) in the Caddy

http://www.racer.com/imsa/item/14656...smaller-engine

Also, imsa has a 580hp target.
So according to the article, the engine has been de-stroked, it's not the old DP engine or the GTE engine. So weight balance is not part of the equation - if, somehow, the pistons in the 6.2 were so heavy that the de-stroked block's extra weight in combination with the smaller pistons is lighter it'd be at most a five pound difference. It is in all likelihood exactly the same weight.
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