Turkish block strikes again on YUM this time
19-06-2008, 08:17 AM
#281
True, but than again, when u start the engine, you are pushing the pistons through there compression stroke quite easily, so the force of the compression itself can't be that big.
Cylinder pressures will ofcourse be higher, but as I said in my previous post: Cylinder pressure = torque.
Say I have an engine with high comp but N/A, it will not have very much torque, so no liners needed. If i have a low comp engine with a massive boost spike and lots of torque, i might need them a lot sooner.
Does CR affect the cilinder pressure, YES
Does the amount boost affect cilinder pressure, YES
and so do alot of other (smaller) factors.
Just saying high comp = liners, low comp = no liners is BS (All IMO ofcourse)
Cylinder pressures will ofcourse be higher, but as I said in my previous post: Cylinder pressure = torque.
Say I have an engine with high comp but N/A, it will not have very much torque, so no liners needed. If i have a low comp engine with a massive boost spike and lots of torque, i might need them a lot sooner.
Does CR affect the cilinder pressure, YES
Does the amount boost affect cilinder pressure, YES
and so do alot of other (smaller) factors.
Just saying high comp = liners, low comp = no liners is BS (All IMO ofcourse)
.You say that high compression = high cylinder pressure.
You then say that high cylinder pressure = torque.
You then agree that high torque requires liners, but disagree that high compression creates this - WTF?
For people's information, the reason for the liners is that the last batch of blocks produced by Cosworth were the Turkish ones. It was soon discovered that at around 500bhp, these would regularly crack the bores - even with the standard piston size. The cause was subsequently found to be that the "99" blocks did not have the same cylinder wall thickness of the original batch of the Cosworth cast blocks. Therefore, linering is advisable on these blocks if going above 500bhp.
Ipso facto, I think you will find that the people running the high power do so on the earlier "proper" blocks, and those that liner do so for cylinder pressure / bore size / block type reasons
. Also from what I understand, the Scandinavian cars, although driven hard do less than 2-3k miles a year, so tend to last much longer than the most UK cars, which tend to do 2-3 times that, which obviously makes the lower mileage cars appear more reliable... 
19-06-2008, 08:43 AM
#282
People's assumptions about cylinder pressures on higher comp engines in this thread arent correct IMHO
The peak cylinder pressure seen is limited ultimately only by the point at which your mixture det's.
If you run more timing on a lower comp motor you will still get to this same pressure.
The peak cylinder pressure seen is limited ultimately only by the point at which your mixture det's.
If you run more timing on a lower comp motor you will still get to this same pressure.
19-06-2008, 08:50 AM
#283
Chip from what I understand of Mark's engines (and the figures he has previously posted), he still likes to run similar ignition values to the low comp engines, which obviously puts a huge strain on the engine with 2.5 to 2.7 bar up it 
. Again, I am just going by what I have read in Mark's posts.
Hence why he has recommend liners for his engines.
. Again, I am just going by what I have read in Mark's posts.Hence why he has recommend liners for his engines
.
19-06-2008, 08:55 AM
#284
Chip from what I understand of Mark's engines (and the figures he has previously posted), he still likes to run similar ignition values to the low comp engines, which obviously puts a huge strain on the engine with 2.5 to 2.7 bar up it . Again, I am just going by what I have read in Mark's posts.
Hence why he has recommend liners for his engines.
. Again, I am just going by what I have read in Mark's posts.Hence why he has recommend liners for his engines
.I dont care what you think mark does or doesnt like, he cant run more timing in any given circumstance than the amount that generates a cylinder pressure which introduces det!
Detonation is caused when the cylinder pressure is high enough (either globally or locally) to cause some of the mixture to spontaneously ignite.
Better piston design, better head shape, squish volumes etc, these things all effect what peak pressure can be run without det occurring, compression ratio doesnt have the correlation you think it does.
Last edited by Chip; 19-06-2008 at 08:58 AM.
19-06-2008, 09:08 AM
#285
I understand this, but from Mark's own threads, on a lot of his big power engines, he runs high boost (2.5 bar held), relatively high compression (8.0:1) and relatively high ignition values (18 degrees on the top line if memory serves me correct?). This all means that IMO, a linered block is essential for an engine of this application.
I personally wouldn't run an engine of this kind of specification without this - and it would appear that Mark wouldn't either - unless you are saying he is doing things un-necessarily?
.
I personally wouldn't run an engine of this kind of specification without this - and it would appear that Mark wouldn't either - unless you are saying he is doing things un-necessarily?
.
19-06-2008, 11:29 AM
#286
I understand this, but from Mark's own threads, on a lot of his big power engines, he runs high boost (2.5 bar held), relatively high compression (8.0:1) and relatively high ignition values (18 degrees on the top line if memory serves me correct?). This all means that IMO, a linered block is essential for an engine of this application.
I personally wouldn't run an engine of this kind of specification without this - and it would appear that Mark wouldn't either - unless you are saying he is doing things un-necessarily?.
I personally wouldn't run an engine of this kind of specification without this - and it would appear that Mark wouldn't either - unless you are saying he is doing things un-necessarily?
.You seem to be totally missing the point with regards to cylinder pressures mike.
He cant exceed the point at which det occurs, the ONLY way he can run higher cylinder pressures than say martin or harvey does, is if his engines are better designed internally and have massively better det resistance as a result.
This would make them both more powerful and more economical by default of course, do you think this to be the case? As there is NO other way that he can run any higher peak cylinder pressures than other tuners do.
19-06-2008, 11:37 AM
#287
Advanced PassionFord User
People's assumptions about cylinder pressures on higher comp engines in this thread arent correct IMHO
The peak cylinder pressure seen is limited ultimately only by the point at which your mixture det's.
If you run more timing on a lower comp motor you will still get to this same pressure.
The peak cylinder pressure seen is limited ultimately only by the point at which your mixture det's.
If you run more timing on a lower comp motor you will still get to this same pressure.
I was reaing the second last page going
then clicked over and chip had beaten me to it
19-06-2008, 11:39 AM
#288
Alistair, Id have liked to go one step further and point out that in a lot of cases lower compression means lower in cylinder temps, and hence you can actually run slightly HIGHER peak cylinder pressures before the onset of det in certain circumstances, but I figure that might be a step too far
19-06-2008, 11:47 AM
#290
BUT lets not go off at a tangent, currently Mike Rainbird is in the middle of explaining to everyone how an MAD engine is SO much better designed internally that it has det resistance way beyond anything from SCS or Reyland etc, and I suspect that people like Rod Tarry are going to really enjoy reading all about it, as they've been saying for years there are subtle differences in MAD engines which make them better and before now Mike Rainbird has always seemed to not agree with them, but now he really seems to be promoting Mark Shead's engine design in a MASSIVE way by saying that Mark Shead can manage the "holy grail" of handling higher peak cylinder pressures without detonation, presumabley due to a better understanding of squish/piston design/cylidner heads, than all the "old school" tuners can muster
Last edited by Chip; 19-06-2008 at 12:05 PM.
19-06-2008, 12:57 PM
#291
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Maybe i didn't put it really clear in my previous posts mike, but what i was trying to say is it's the amount of torque the engine produces that determines if you need liners or not. Not just the fact if you run high comp or not. (As you stated earlyer)
Ofcourse, if you have 2 the same engines, running the same boost, but one is low comp and the other high comp, the high comp engine will produce more torque, but that's not the point.
19-06-2008, 01:03 PM
#292
Yes, but high boost also means high cylinder pressure, not just compression.
Maybe i didn't put it really clear in my previous posts mike, but what i was trying to say is it's the amount of torque the engine produces that determines if you need liners or not. Not just the fact if you run high comp or not. (As you stated earlyer)
Ofcourse, if you have 2 the same engines, running the same boost, but one is low comp and the other high comp, the high comp engine will produce more torque, but that's not the point.
Maybe i didn't put it really clear in my previous posts mike, but what i was trying to say is it's the amount of torque the engine produces that determines if you need liners or not. Not just the fact if you run high comp or not. (As you stated earlyer)
Ofcourse, if you have 2 the same engines, running the same boost, but one is low comp and the other high comp, the high comp engine will produce more torque, but that's not the point.
19-06-2008, 01:21 PM
#293
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You should have added "generally" as if the high comp means that you have to retard the timing excessively at peak torque to avoid det (the thing that Mike Rainbird feels Mark Shead's engines internals are better designed to minimise with than the old school stuff from other tuners) then you can end up with less torque not more on higher comp. The devil (as always) is in the details.
19-06-2008, 02:09 PM
#294
Yes, but high boost also means high cylinder pressure, not just compression.
Maybe i didn't put it really clear in my previous posts mike, but what i was trying to say is it's the amount of torque the engine produces that determines if you need liners or not. Not just the fact if you run high comp or not. (As you stated earlyer)
Ofcourse, if you have 2 the same engines, running the same boost, but one is low comp and the other high comp, the high comp engine will produce more torque, but that's not the point.
Maybe i didn't put it really clear in my previous posts mike, but what i was trying to say is it's the amount of torque the engine produces that determines if you need liners or not. Not just the fact if you run high comp or not. (As you stated earlyer)
Ofcourse, if you have 2 the same engines, running the same boost, but one is low comp and the other high comp, the high comp engine will produce more torque, but that's not the point.
. 2.7 bar mid-range = 500+lb ft .
19-06-2008, 04:14 PM
#304
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19-06-2008, 04:15 PM
#305
Well the cam profile isnt what is relevent, to what the engine sees on its own in terms of valve lift and duration, its also the amount that the lifters open, and that is also effected by the lifters at the time
(although they of course empty and close down in size as the forces on them increase with rpm, especially as the oil they rely on to stay open gets hotter and thinner and leaves them, they obviously do NOT jack up like little Mike here seems to think)
(although they of course empty and close down in size as the forces on them increase with rpm, especially as the oil they rely on to stay open gets hotter and thinner and leaves them, they obviously do NOT jack up like little Mike here seems to think
)
19-06-2008, 04:47 PM
#317
I dont think the rules of building these engines has changed in that time, just the goalposts have moved!
19-06-2008, 04:52 PM
#318
Yours was a trackcar, id be using solids in a track car even at much lower power levels personally (in fact I was doing so 15 years ago, lol), and im sure Mark would have done back then as well if that was what he was trying to achieve at the time.
I dont think the rules of building these engines has changed in that time, just the goalposts have moved!
I dont think the rules of building these engines has changed in that time, just the goalposts have moved!
19-06-2008, 04:54 PM
#320
10K+ Poster!!
Yours was a trackcar, id be using solids in a track car even at much lower power levels personally (in fact I was doing so 15 years ago, lol), and im sure Mark would have done back then as well if that was what he was trying to achieve at the time.
I dont think the rules of building these engines has changed in that time, just the goalposts have moved!
I dont think the rules of building these engines has changed in that time, just the goalposts have moved!
Can you use solids on normal hydraulic cams ?