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Save the Date - 2020 Annual Sevens HPDE Event at NJMP - October 17/18, 2020


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Mike, I believe it’s up around 9200 with the crank that Karl specced For it. I know they took it up over 8700 when I had it dynoed I however find no need to take it that high. I scare the crap out of myself at 7000rpm

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Mike, I believe it’s up around 9200 with the crank that Karl specced For it. I know they took it up over 8700 when I had it dynoed I however find no need to take it that high. I scare the crap out of myself at 7000rpm ��

 

Original Cosworth literature says 8800rpm for Tom's engine. It has the special billet crank.

 

Mine did not have the special crank so limited to 7800rpm

 

No real need to go that high though, the peak torque/power curves mean it makes sense to change well before that.

 

 

Edited for correction - its actually 8900rpm for Tom's engine. I reconfirmed my memory this morning

Edited by Croc
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I used the dyno curve, the gear rations and a simple spreadsheet to work out the best shift point in each gear. I then programmed the shift light to reflect the numbers so all 6 lights on is 1st, 5 lights 2nd, 4...... With all cars the shift point will get lower as the gear ration lowers. But like Croc says the shift points have nothing to do with the rev limit, some people spin the Honda motors like crazy but it's not necessary.

 

Graham

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An advantage of having a red line higher than the normal shift points is the ability to "stretch" a gear. Auto cross and mountain rally special stages are good examples. If the next corner is close enough to only allow a couple seconds in the next gear, it's better not to shift and then down shift. The extra shifts provide an opportunity to miss a gear, or upset the chassis on corner entry. Personally, I hate banging against a rev limiter.

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All very good points raised. This is why I love the larger displacement Duratec engines. They have lovely fat torque curves which gives shift point flexibility no matter what the need.

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I agree with the advantage of being able to "stretch" a gear with a higher RPM limit. At our annual gathering at the Lightning circuit at NJMP, I am able to hit the 7200 RPM redine in 5th gear, half way down the front straight. This is in my 6 sp Zetec powered Caterham.

 

So the question is whether it is worth an upshift, and then a downshift before entering the big right hand turn at the end of that straight? The answer, after much trial and error, is no, it's not worth it. Instead I lift up on the accelerator a bit and keep the revs at 7000. Then a single shift down to 4th before the turn (rather than 2 shifts into 4th before the turn) simplifies things.

 

Lightning's front straight has proven diagnostic over the years. On my original engine, following a tune, I was able to get into 6th at the beginning of the straight. That was nice! Later, when I had trouble getting into 6th by the end of the straight, I knew there were power issues. (First O2 sensors, later compression loss).

 

When I came back following an engine swap and was only able to use 6th gear 1/2 way down the straight, I knew the new engine was missing some hp.

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I agree with the advantage of being able to "stretch" a gear with a higher RPM limit. At our annual gathering at the Lightning circuit at NJMP, I am able to hit the 7200 RPM redine in 5th gear, half way down the front straight. This is in my 6 sp Zetec powered Caterham.

 

So the question is whether it is worth an upshift, and then a downshift before entering the big right hand turn at the end of that straight? The answer, after much trial and error, is no, it's not worth it. Instead I lift up on the accelerator a bit and keep the revs at 7000. ..."

 

LONG straights. That's another interesting point. In Mexico, they have had real top speed rally stages, especially in the north. We're talking full speed for say 2 miles or more. Ridiculous stuff. Often someone would blow an engine, with lots of excuses. Gas, tune, etc... I took a bit different technique, and never had an issue. Once at max revs (7200), which was 145 mph in that car, I would do a hard lift for a few seconds. Didn't lose too much time, then ease back up to top speed. My theory was to suck some oil vapors to keep the combustion chamber a bit cooler. Maybe BS, and I just got lucky.

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I had a similar thought Shane. Except my flashback was triggered when I saw the mammoth bear toothed, seven-destroying curbing on the turn at the bottom of the photo(:!

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ok...which of you caused the skid marks on turn 12?

 

I'll never tell........:cooldude:

 

But....speaking of skid marks, here's the COVID=19 balaclava. Guaranteed to promote social distancing during that 25 minute track session especially during point-by and overtake maneuvers.:jester:

 

AF42BFF8-627A-47B0-8652-AD4F24F89E3A.jpg

AF42BFF8-627A-47B0-8652-AD4F24F89E3A.jpg

Edited by xcarguy
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I kind of forgot the Cosworth 2.3 Duratec revved to 8,800. That's Formula 1 and Winston Cup piston speeds. (27.5 meters per second avg, 43.3 max). The short stroke engine equivalent would be close to 9,100 but I don't think I'll push it that hard. We'll see what the torque and HP curves look like.

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Hi Croc - I'm not really sure what the HP will be, we're breaking new ground here. For a guess, it's almost the same displacement as the 2.5 which made 200 lb-ft of torque at 7,200 and 274 hp. If we can make maybe 180 lb-ft but about 1,000 rpm higher that could get us over 280 HP. We'll see soon. I'll keep you posted.

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