Low Compression Vs High Compression - Discuss
30-01-2004, 06:52 PM
#41
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The moral of the story is....
Decide a spec for the engine and get it built and tuned properly !!
(dont just chuck a chip in and expect 1000000 BHP)
Every tuner/builder has thier own methods and standards.
Sadly, alot of people WRONGLY believe the following statements are true...
1) Low compression is safe
2) Rich fuel mixtures prevent detonation
Decide a spec for the engine and get it built and tuned properly !!
(dont just chuck a chip in and expect 1000000 BHP)
Every tuner/builder has thier own methods and standards.
Sadly, alot of people WRONGLY believe the following statements are true...
1) Low compression is safe
2) Rich fuel mixtures prevent detonation
30-01-2004, 06:57 PM
#43
Originally Posted by SECS
Sadly, alot of people WRONGLY believe the following statements are true...
1) Low compression is safe
2) Rich fuel mixtures prevent detonation
1) Low compression is safe
2) Rich fuel mixtures prevent detonation
point 2 surely the right air/fuel ratio is important......so running to rich fecks that up as much as running lean....also thinking that running a little rich is MUCH better than running lean ?
30-01-2004, 06:59 PM
#44
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As an example (can name names or car)...
(Not a cossie motor)
2.1 litres,
4 cylinders
8.7 CR,
Special designed pistons,
97 RON fuel (super),
Water injection (no additives),
Wideband lambda
EGT fuel control,
Motec ECU
840 BHP (With engine reliability - transmission is another matter !!)
I have seen this on the rollers and engine dyno ....
(Not a cossie motor)
2.1 litres,
4 cylinders
8.7 CR,
Special designed pistons,
97 RON fuel (super),
Water injection (no additives),
Wideband lambda
EGT fuel control,
Motec ECU
840 BHP (With engine reliability - transmission is another matter !!)
I have seen this on the rollers and engine dyno ....
30-01-2004, 07:02 PM
#46
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Originally Posted by dingy
Originally Posted by SECS
Sadly, alot of people WRONGLY believe the following statements are true...
1) Low compression is safe
2) Rich fuel mixtures prevent detonation
1) Low compression is safe
2) Rich fuel mixtures prevent detonation
point 2 surely the right air/fuel ratio is important......so running to rich fecks that up as much as running lean....also thinking that running a little rich is MUCH better than running lean ?
AFR is important and rich is better than lean,
but rich mixtures do NOT guarantee det free perfromance.
30-01-2004, 07:04 PM
#48
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Originally Posted by dingy
daddy, i can't see how a little too much fuel is that bad over a little lean 
I let karl do my engine specs, he seems to be ok at it, his car is no to slow.
I let karl do my engine specs, he seems to be ok at it, his car is no to slow.
30-01-2004, 07:05 PM
#49
SECS, not saying your wrong or anything just asking...
So if a car has a little too much fuel how can this be det free....
I am thinking too much ignition ? or is that not what u are getting at.
So if a car has a little too much fuel how can this be det free....
I am thinking too much ignition ? or is that not what u are getting at.
30-01-2004, 07:06 PM
#50
Originally Posted by SECS
Originally Posted by dingy
daddy, i can't see how a little too much fuel is that bad over a little lean
I let karl do my engine specs, he seems to be ok at it, his car is no to slow.
I let karl do my engine specs, he seems to be ok at it, his car is no to slow.
was a piss take
30-01-2004, 07:11 PM
#52
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Well, metallurgy has evolved quite a bit and there are some alloys available now for pistons that were not back then.
I suspect that between having MUCH better ECU's available (better resolution on fuel AND timing) and the advances in materials, the development possibilities have opened up quite a bit.
There are a lot of people who tend to stay with 'tried and true' methods and that's fine as long as they work. I like to take advantage of newer tech and don't mind doing some of my own development rather than just going with a 'plug and play' solution.
YMMV
I suspect that between having MUCH better ECU's available (better resolution on fuel AND timing) and the advances in materials, the development possibilities have opened up quite a bit.
There are a lot of people who tend to stay with 'tried and true' methods and that's fine as long as they work. I like to take advantage of newer tech and don't mind doing some of my own development rather than just going with a 'plug and play' solution.
YMMV
30-01-2004, 07:12 PM
#53
Originally Posted by Ima Racing500
See Paul Hills at Engine Advantages...end of topic
Most tuners on here talk crap...ok 1 tuner on here in particular Get proper info and then base a decision..................
Most tuners on here talk crap...ok 1 tuner on here in particular
Get proper info and then base a decision..................????? who ?????????
30-01-2004, 07:13 PM
#54
PS....This is a fact...the reason many tuners dont agree with hi comp is because they arnt competant enuff to do hi comp,lo comp is safer cause its all they know...as SECS has said move on people....
30-01-2004, 07:14 PM
#55
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The moral:
If you are happy with your engines performance, who cares about CR.
If you want performance and good fuel consumption High CR is the way to go IMO!
If you are happy with your engines performance, who cares about CR.
If you want performance and good fuel consumption High CR is the way to go IMO!
30-01-2004, 07:17 PM
#56
Originally Posted by Ima Racing500
PS....This is a fact...the reason many tuners dont agree with hi comp is because they arnt competant enuff to do hi comp,lo comp is safer cause its all they know...as SECS has said move on people....
but that statement is horseshit....if you have the means to make something better, IE management then thats the way it goes.
More the control increases the better the reliability, simple facts really.
30-01-2004, 07:17 PM
#57
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Originally Posted by dingy
Originally Posted by Ima Racing500
See Paul Hills at Engine Advantages...end of topic
Most tuners on here talk crap...ok 1 tuner on here in particular Get proper info and then base a decision..................
Most tuners on here talk crap...ok 1 tuner on here in particular
Get proper info and then base a decision..................????? who ?????????
????I never claimed to be a tuner !!
30-01-2004, 07:21 PM
#58
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well, lets see a high comp engine put some decent times in then and prove something...
(i'm going to feel really stupid now if martin hadlands is over 8.0:1)
(i'm going to feel really stupid now if martin hadlands is over 8.0:1)
30-01-2004, 07:22 PM
#60
Originally Posted by Ima Racing500
PS....This is a fact...the reason many tuners dont agree with hi comp is because they arnt competant enuff to do hi comp,lo comp is safer cause its all they know...as SECS has said move on people....
Perhaps you need to explain all the techinical aspects of low and high comp engine speccing et etc and why high comp is better. There is only one person I have seen do this on this board and justify his point and that is Karl hence why I love the posts he does.
Most people say you should do this but can't explain for shit why, Karl on the other hand say's you should do this and explain in great detail why.
In short one person is talking here say bollocks and somebody else is talking fact. I experience the same thing in IT and it makes me laugh my tits off at some people.
So to sum you up your techincal disccusion on the matter in case anyone missed that. High comp is better because............hmmmmm.........hmmmm.........er rr.......Paul Hills says it is........hmmmmmmmm........my engine drives better now (but still laggier than dan's T4 low comp engine).......
Point made me thinks, off for food!!LOL
Cheers,
Dan
30-01-2004, 07:34 PM
#66
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The C:R in my fiesta is quite low - but agressive ign advance makes it a responsive car to drive
here's another intersting point - if a car cannot produce low act's you have to go for low c:r to combat det
here's another intersting point - if a car cannot produce low act's you have to go for low c:r to combat det
30-01-2004, 07:37 PM
#67
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Hmm, would ACTs have that much of an effect? I'd not ahve though you'd need to alter CR for it!!!.
Essentially a high ACT means less oxygen/unit. Therefore you'd just adjust the fueling to suit (so you retain your desired AF ratio), why would you need to go low comp??
*Probably missing a point here!*
Essentially a high ACT means less oxygen/unit. Therefore you'd just adjust the fueling to suit (so you retain your desired AF ratio), why would you need to go low comp??
*Probably missing a point here!*
30-01-2004, 07:40 PM
#69
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higher compression promotes earlier point of det! higher combustion temps in cylinder due to the air being compressed alot more. so in theory could lead to more localised hotspots which promote the onset of det...
how ever a higher compression does give a biger bang when combustion occurs so does give more power, its just making sure the engine can cope and that cheap/bad quality pump fuel aint used to try to decrease the risk of det!
just what i have sort of learnt in the course at uni so far, prob all wrong tho!
how ever a higher compression does give a biger bang when combustion occurs so does give more power, its just making sure the engine can cope and that cheap/bad quality pump fuel aint used to try to decrease the risk of det!
just what i have sort of learnt in the course at uni so far, prob all wrong tho!
30-01-2004, 07:41 PM
#70
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Originally Posted by PhilM
Hmm, would ACTs have that much of an effect? I'd not ahve though you'd need to alter CR for it!!!.
Essentially a high ACT means less oxygen/unit. Therefore you'd just adjust the fueling to suit (so you retain your desired AF ratio), why would you need to go low comp??
*Probably missing a point here!*
Essentially a high ACT means less oxygen/unit. Therefore you'd just adjust the fueling to suit (so you retain your desired AF ratio), why would you need to go low comp??
*Probably missing a point here!*
But it depends completely on the sum of the total spec of the engine.
(I.E Every engine is different !!)
30-01-2004, 07:43 PM
#73
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Originally Posted by PhilM
Cool
Good job ive got my little cooler planned then eh mate? Fuck knows what the outlet temperature will be, will be interesting to find out though 
Good job ive got my little cooler planned then eh mate?
Fuck knows what the outlet temperature will be, will be interesting to find out though Its a fickle old world .....
Next topic subject -- too hot or too cool !!!!
30-01-2004, 07:45 PM
#78
Its all to do with mapping..you either got it or you aint..and most certainly aint!!!!!
Remember i specced my engine..and i aint a pro ..Paul is doin his best with a bad job..ROFL...but i have every confidence!
Remember i specced my engine..and i aint a pro
..Paul is doin his best with a bad job..ROFL...but i have every confidence!