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18 May 2020, 12:05 (Ref:3976928) | #8651 | |||
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Last edited by bjohnsonsmith; 18 May 2020 at 12:10. |
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"If you're not winning you're not trying." Colin Chapman. |
13 Nov 2020, 02:54 (Ref:4016286) | #8652 | |
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14 Nov 2020, 19:52 (Ref:4016666) | #8653 | ||
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It wasn't "cancelled". It's just a design exercise like the gorgeous 906 and 904, the amazing little VW-Porsche bus all the other renders they've shared. They were never meant to become a reality.
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9 Jan 2021, 09:33 (Ref:4027802) | #8654 | ||
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Let’s see if we can revive this thread:
Most rumors (not all) claim that Porsche will develop their V8 used in their Cayenne for their LMDh car. Whilst I can understand that this would be attractive from a weight (minimum engine weight allowed is enormous (~180Kg) and cost, I suggest that perhaps the 4.6 V8 from the 918 makes better sense. Here are the reasons: 1. The 4.6 V8 (447KW) is indeed a production engine as it was used in the 918 (918 cars were built) 2. This engine is a modified version of the 3.4 V8 (414KW) used in the Porsche 918 RSR concept car which is the same engine that was used in the RS Spyder (Engine known as the MR6) 3. Given the above, the 4.6V8 production version could be easily modified to produce the 470KW required for LMDh. (perhaps an addition of a small turbo) 4. The weight would have to be increased , but that is easily done through ballast with the added benefit of placing the weight where it does the least damage. 5. The engine is a race car derived engine with a very low center of gravity. Any thoughts? |
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9 Jan 2021, 09:38 (Ref:4027803) | #8655 | |||
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LMDh will most likely be heavily BoPed so the incentive of using an expensive engine compared to a cheap mass production engine is low. |
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Hvil i Fred Allan. (Rest in Peace Allan) |
9 Jan 2021, 10:06 (Ref:4027808) | #8656 | |||
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Agreed, but surely Porsche would want to guarantee the best possible handling car under those very restricted conditions. I still think that the MR6 derived lump would be a better choice than a SUV lump, no? |
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9 Jan 2021, 10:41 (Ref:4027812) | #8657 | |||
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LMDh has very cost oriented (even though proven more expensive than LMh by Glickenhaus) so with heavy BoP, why bother going for that extra handling at a larger cost increase, when BoP is going to bring you in line with the rest of the field anyway? |
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Hvil i Fred Allan. (Rest in Peace Allan) |
9 Jan 2021, 10:43 (Ref:4027813) | #8658 | |
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the 918 V8 engine revs up to about 9000rpm to get 610hp and peak torque is around 550Nm between 6000-7000rpm. These figures make the 918 engine almost virtually identical to the gibson lmp2... no doubts it can be a competitive motor, but compared to a turbo engine (bespoke or not) will lack of low-mid torque and fuel efficiency.
The second one is not a big problem because bop will give a proper fuel tank and fuel rig diameter, but the lack of torque in the traffic can't be bopped. To me the most logical choice would be to use a racing tuned version of the 2.9L V6 TT of cayenne S, it should be already equipped with DI too. |
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9 Jan 2021, 11:26 (Ref:4027823) | #8659 | |||
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Yes, lack of torque was my main concern. |
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9 Jan 2021, 14:02 (Ref:4027841) | #8660 | ||
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BTW -
Latest Double Stint Podcast Episode S6:E1 John Dagys says some rumors suggest revival of the MR6 engine |
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9 Jan 2021, 19:14 (Ref:4027869) | #8661 | ||
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Some suggest it would be a more expensive option than using a Bentley GT3 version of an Audi-derived V8. But were those old LMP2 really that expensive to buy and run?
And I think it's better to look at it as a Bentley GT3 V8 vs old MR6 V8, rather than Cayenne V8 road engine or 918 road engine, as Porsche is unlikely to start over, when there already are proven race engines that are related. Of course, this is provided Weissach and its suppliers still have all that's necessary to re-start production of MR6 over a decade later without much extra investment. |
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9 Jan 2021, 22:28 (Ref:4027895) | #8662 | ||
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Porsche RS Spyder (whole car and spares/support) MSRP'd from Porsche Motorsport for over $1.5 million USD. A customer LMP1 was much cheaper, as was even an Audi R8 LMP900 at about the same time.
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Power to me is having the ability to make a change in a positive way. Don't dream it, be it. |
9 Jan 2021, 22:57 (Ref:4027896) | #8663 | ||
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To me the audi/bentley V8 4L TT doesn't make much sense... that engine is like an elephant in a small room... ligier and ESM used the nissan gt-r gt3 engine and they had all kind of cooling and packing issues because of an engine too big to fit in a lmp... not to consider that will be however useless performancewise to have a so big turbo engine since the huge torque release will be however tuned down by bop turbo pressure rpm curve. Also a high-rev/low-torque engine isn't the best option in my opinion, but I guess they know what they are doing. |
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10 Jan 2021, 02:30 (Ref:4027908) | #8664 | |
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10 Jan 2021, 04:26 (Ref:4027915) | #8665 | ||
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Ooh! First time I have seen this!
Are you able to provide a link? Thank you! |
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10 Jan 2021, 10:33 (Ref:4027932) | #8666 | ||
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1) N/Nmax intended as rpm engine, does each step means the % of torque refering to the max torque available? something like example 0.55, meaning 385Nm of a max 700Nm? 2) is this the mandatory power/torque curve of both lmh and lmdh? Because it tells the sum of all 4 wheels power, it let me think it's more about hybrid lmh. Anyway this doesn't change a lot the overall picture since with a turbo engine + hybrid release you can virtually get the torque/power curve you wish through mandatory pressure boost and hybrid release software, good luck to achieve that with a not bespoke NA engine. At the same time, it doesnt' change what I was meaning about the 918 engine... you could eventually be able to set the torque/power curve that way, but the torque release of a NA 4.6L will be however lower than the one released by a turbo engine... the same about fuel efficiency... a smaller engine will require to rev higher anyhow to get high power, so fuel efficiency will be worse anyhow (why mazda engine revving >9000rpm needs a larger fuel tank than other dpi revving at 7000-7500rpm?). At the end you just can't bop physics. |
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10 Jan 2021, 10:50 (Ref:4027935) | #8667 | |
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Porsche did not go the the turbo route with their 991 GTE car. If I recall correctly, Porsche AG stated that BOP would address the torque differences of the various engines - so they did not believe turbo engines in the 911 would be of any advantage - so they opted to go with a lighter and less heat NA engine solution. Suspect that they will do the same with the new LMP.
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10 Jan 2021, 11:30 (Ref:4027939) | #8668 | ||
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Well, Audi are rumored to be using their I4 from DTM... and that's basically the engine that was so expensive that it killed Class 1. With the two brands closely related, I am wondering if cost is really Porsche's main concern.
BTW, what about an in-house-version of the LBP-Cayenne-V8 from Grand Am? |
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10 Jan 2021, 12:03 (Ref:4027940) | #8669 | |||
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10 Jan 2021, 12:03 (Ref:4027941) | #8670 | |||
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Let us not forget, however, two more......Peter Gregg and and the other monster Turbo-Porsche, the world beating 935. Attending the IMSA Finale weekend a couple 'o year's after Donohue's record run, I never understood it, but, Peter made a run at Mark's closed-course record with his aero'd out 935 (trimmed wing, flush windows and wheel covers, abbreviated inlets, etc.). It wasn't very exciting, watching one car circulate the tri-oval, even if at a good clip. He did succeed, however, in eclipsing the mark. 'Only problem was, it was not an official FIA record as his 222+ didn't break Mark's by the requisite 1%. An anti-climactic footnote to "their" arse kicking season.....Gregg, 9 wins of 14 races; Porsche, 12 (Hobb's quick but fragile turbo mini-motor 320i taking the other two). |
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10 Jan 2021, 12:05 (Ref:4027942) | #8671 | ||
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GTE/GT3 are very heavy cars and the effect of more torque is however compensated by a really high mass (a=f/m) not to consider that when porsche gte was a RR layout car had the best acceleration possible since the engine was mounted on top or rear axle making less torque get lost between shafts and the torque curve was basically a flat line for most of the rpm range (that is basically the reason why 991 gt3r is still a traction killing machine under heavy rain). There isn't much to say about, only a big >5L NA engine may have the same high torque release and fuel efficiency of a mid-sized turbo engine, a smaller NA engine will have less torque and worse consumes no matter what. |
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10 Jan 2021, 12:38 (Ref:4027944) | #8672 | ||
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deleted, duplicate
Last edited by jimclark; 10 Jan 2021 at 12:57. Reason: duplicate |
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"Those were the days my friends. We thought they'd never end..." jimclark |
10 Jan 2021, 18:49 (Ref:4027996) | #8673 | ||
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Quote:
“We finally opted for a normally aspirated engine exactly one year ago,” Walliser said. “The final go was a meeting between Dr. Blume [Porsche CEO] and myself in Bahrain. “For the 911 concept, considering our actual engine lineup, a normally aspirated engine gives us more freedom in the car concept, e.g. weight distribution.” However, Walliser doesn’t see it as a disadvantage, thanks to variable boost levels for turbocharged engines implemented by the FIA, ACO and IMSA that now provides a near-identical power curve for both normally aspirated and turbocharged engines. “The rules are written in a way that gives turbos and normally aspirated engines the same power and torque behavior,” he said. Will LMP BOP be able address this issue the way GTE seem too? Beleive it or not, the street version 997 GT3 is faster from 60 to 120 than the 911 Turbo. Might be mainly by weight differences. |
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10 Jan 2021, 19:06 (Ref:4027999) | #8674 | ||
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Quote:
Acceleration is more influenced by mass than force (torque) but since lmp1, lmp2, gte are all in a similiar range of mass, it's clear that more torque gives a better acceleration. Aside that, acceleration is influenced by also a lot of other factors... cx of the car, gear ratios, width of tyres etc... |
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13 Jan 2021, 23:00 (Ref:4028838) | #8675 | ||
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They're always here. Yes it's the LMH regulations and not LMDh, but if the power units are going to be capped to the same power level and all the other basic car parameters are basically identical it would be crazy for this to not also apply. |
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