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Old car, new engine. Spanking...
Cars Modifications Aspects of car modifications (tuning, styling) (uk.rec.cars.modifications)
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#31
 
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Re: Old car, new engine. Spanking... -
04-23-2007
, 11:35 AM
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In article <9_1Xh.716$zI1.488 (AT) newsfe2-win (DOT) ntli.net>, burgerman (AT) ntlworld (DOT) com says... Hes probably got most of the extra power purely from daft compression ratios. Try it it works! But you need higher octane fuels to stop it eating itself. Sorry but that is provable wrong: the extra compression raises the theoretical efficiency but it contributes but marinal to extra power. The formula is n = 1- 1 /(L^(k-1)) L= compression ratio k is a ration which defines if the burning goes on under constant pressure (=piston moving down) compared to burning under constant volume (piston in TDP) IRL k equals around 1.4. The *theoretical* efficiency for L = 10 is 60% , for L =17 it is 67.8% So if you take an engine and you change nothing but the compression and supposing that the mixture doesn't detonate unwanted, the gain is power would be 13% ( 67,8 /60) |
in volumetric efficiency as well? And the gain by ignition process later in
the cycle? Because half the gain comes from this.
Then 13 percent extra (I see much more in practice for whatever reason) when
you would have had around 300 anyway is a marked 40 hp extra! And from
experience compression hikes of that amount show greater than 13 percent!
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Petrol engines are not build for the extra stresses that the compression raise that high introduces, diesels are. |
go so damned fast and read stagering numbers on my dyno afterwards?
EG my mates olde 2 valve kawasaki has both a big valve and big bore and
about 16 to 1 compression and its seriously FAST and a road bike.
NA-engines can not
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"intercool" or liquidate the heat interduced by the compression. |
They seem to manage exactly that extremely well! I have added a couple of
140 bhp nitrous systems to various very high compression bike engines
without any problems at all. Just big power.
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IRL our Greek will get close to nothing on raising the compression ratio that high because ignition will have to be retarded too. He has a nice engine which in the escort Mk2 will be a blast to drive but it hasn't 400 Hp not by a long way. |
power curve that says he has. And its easy to repeat.
But it IS possible to get close to that say 330 or 40 though. Although I
dont believe the revs since the piston speed at a quess would be out of the
57 to 60 fps range which is pushing it a lot.
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Hp-figures sell, just like topspeed-figures and "race"-parts anodised in fancy colors but weaker then OEM-parts. How often have we passed a competitor who claimed he was above 200 kph when our datalogging showed 170 kph... Most of the time they went on complaining that our engine was modified beyond the rules "cause he was over 200 kph"... Tom De Moor Tom De Moor |
#32
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Dunno, I think the rule I quoted is current - that a team may use a V10 but it has to be rev limited and the team has to prove that it had no V8 alternative available. No such limit applies to the V8. |
The V8 is limited to 19000rpm to try and keep costs down.
#33
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"Steve Firth" <usenet-urcm (AT) malloc (DOT) co.uk> wrote in message news:1hx133w.11qxy27opu4opN%%steve%@malloc.co.uk.. . Dunno, I think the rule I quoted is current - that a team may use a V10 but it has to be rev limited and the team has to prove that it had no V8 alternative available. No such limit applies to the V8. Are there any teams still using the V10, I think they're all on V8's now? The V8 is limited to 19000rpm to try and keep costs down. |
quoted about the limited V8s was the case.
--
Dan
#34
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In article <xn0f5agg61pfqu001 (AT) nermal (DOT) unix-consult.com>, ... and that fits as a glove in a oldtimer-rallye car worth 2 kUPD? |
cost you £12000-£20000.
Even a good standard RS car will be £5000+
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BTCC 2l (like the Williams Laguna's, TWR Volvo's) on TB's were at 300 HP with serious budgets. |
wouldn't that equate to around 400bhp?
#35
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ThePunisher wrote: Albert T Cone wrote: ThePunisher wrote: Elder wrote: http://retrorides.proboards86.com/index.cgi? board=general&action=display&thread=1177001426 Crazy mad fucking greek fucker. Shouldn't the power and torque lines cross around 5252? Nah, he isn't using lb.ft for the torque - he's using kg.m 5180 for metric, whatever he's using it should cross near the 5000rpm line. Also, he's using separate axes for the power and torque plots - they can cross where they like! |
torque figure?
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ThePunisher
#36
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Albert T Cone wrote: ThePunisher wrote: Albert T Cone wrote: ThePunisher wrote: Elder wrote: http://retrorides.proboards86.com/index.cgi? board=general&action=display&thread=1177001426 Crazy mad fucking greek fucker. Shouldn't the power and torque lines cross around 5252? Nah, he isn't using lb.ft for the torque - he's using kg.m 5180 for metric, whatever he's using it should cross near the 5000rpm line. Also, he's using separate axes for the power and torque plots - they can cross where they like! Yes, but the common axis is RPM, you do know how to work out power from a torque figure? -- ThePunisher |
I do I designed and built automotive dyno systems.
And the only graphs that cross at 5252 are ones where BOTH axis are common
and in lb-ft and bhp.
If the scale for torque is on a different measurement (kg metre?) or the
torque is on the other side of the graph in a different scale they can cross
anywhere.
#37
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Albert T Cone wrote: ThePunisher wrote: Albert T Cone wrote: ThePunisher wrote: Shouldn't the power and torque lines cross around 5252? Nah, he isn't using lb.ft for the torque - he's using kg.m 5180 for metric, whatever he's using it should cross near the 5000rpm line. Also, he's using separate axes for the power and torque plots - they can cross where they like! Yes, but the common axis is RPM, you do know how to work out power from a torque figure? |
For example, if you stretched the torque axis by a factor of two, then
assuming no offset on the axes, the two plots would cross at 2626rpm
instead of 5252. As it is, the torque and power axes have different
scales AND different offsets, so the two lines can actually cross
several times, at arbitrary rpm.
#38
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The formula is n = 1- 1 /(L^(k-1)) L= compression ratio k is a ration which defines if the burning goes on under constant pressure (=piston moving down) compared to burning under constant volume (piston in TDP) IRL k equals around 1.4. The *theoretical* efficiency for L = 10 is 60% , for L =17 it is 67.8% So if you take an engine and you change nothing but the compression and supposing that the mixture doesn't detonate unwanted, the gain is power would be 13% ( 67,8 /60) Does that gobbledegook also allow for the more dense charge due to increase in volumetric efficiency as well? And the gain by ignition process later in the cycle? Because half the gain comes from this. |
theoretical.
It is derived directly from the optimal, theoretical cycle -supposes
there are no pumping losses, that volumetric efficiency is 100%, etc-
and as such that theoretical efficiency is the maximum that can be
obtained for that cycle.
It's a bit like climbing a mountain: you can buy the best gear there is,
be the best climber ever existed, but you can't climb higher than the
top.
Tom De Moor
#39
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Yes, but the common axis is RPM, you do know how to work out power from a torque figure? |
Power = Torque x 2 x pi x RPM /60
pi= 3.1415...
Just watch out that torque is in Nm, Power will be in W(att)
1 Hp = 736 W
TDM
#40
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In article <09aXh.6861$mk4.6281 (AT) newsfe4-win (DOT) ntli.net>, thepunisher (AT) ntlworld (DOT) com says... Yes, but the common axis is RPM, you do know how to work out power from a torque figure? Power = Torque x 2 x pi x RPM /60 pi= 3.1415... Just watch out that torque is in Nm, Power will be in W(att) 1 Hp = 736 W TDM |
No... According to my own dyno software which displays either its 0.7456999
w
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