high power on high C/R turbo engine
#162
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Originally Posted by markk
right im now going to 'unwatch' this topic as its got to the very boring stage of this topic again as it has soooooo many times
Because the argument is always one sided.
Side1-
Mike Rainbird and a few others explains in techy detail why lower comp makes sense if going above 200bhp-250bhp per litre.
Side2-
You, Phil, etc saying they all full of shit, a bunch of wankers, no idea about tuning, not as clever as you, etc, and that high comp is the tits, much nicer to drive, etc.
But no explanation why, no reasoning, no nothing.
So it never goes anywhere. Wonder whos fault that is.
Stu maybe should do one of his essays, at least hes helpful.
Originally Posted by GARETH T
markk
just one quick question,,,, if you was building a YB engine,, with standard engine geometry, (stroke and rod legnth) and a rs500 spec T4 turbo, bd14 cams,,, aiming for around 450-500 BHP,, what comperssion would you go for?
just one quick question,,,, if you was building a YB engine,, with standard engine geometry, (stroke and rod legnth) and a rs500 spec T4 turbo, bd14 cams,,, aiming for around 450-500 BHP,, what comperssion would you go for?
#164
Stavros...i am not calling anyone a wanker?
..i can clearly see that people feel safer with lower comp at higher BHP because there tuners say so and they have to warranty it!
....just to add i beleive Jullian Godfrey now dont do anything under 8-1 on YB engines
Its called advancements and realisations...most tuners just stick to tried and tested..and i dont blame em TBH!!
..i can clearly see that people feel safer with lower comp at higher BHP because there tuners say so and they have to warranty it!
....just to add i beleive Jullian Godfrey now dont do anything under 8-1 on YB engines
Its called advancements and realisations...most tuners just stick to tried and tested..and i dont blame em TBH!!
#165
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Originally Posted by Bosch-Man
Its called advancements and realisations...most tuners just stick to tried and tested..and i dont blame em TBH!!
petrol of the same spec reacts the same today as it did 10 years ago,,, it has chemistry laws that goven that
the problem is, people THINK things has changed,,, and people THINK they know better than cosworth did 12 years ago,,,to sum it up,,,, YOU DONT
tourcar spec engines (which basically is the spec of MOST meg power ybs) where deisgned with the low compression for a reason
#166
Gareth of course they know more now..do you think Julian Godfrey dont know his stuff? ...The fitter there has a 9-1 comp engine running 500bhp on pump fuel!......You are right about me not knowing though..i just drive em and build them to what i want it to be listening to people.
Your all back in the past......lowering the comp will always mean safer ultimately but you sacrifice drivability.....but then your engine is far simpler specced compared to high comp...why was wrc long stud invented?..because cylinder pressures where higher and boost pressure was higher...they needed a better clamp to keep the head on!..Why linered blocks?..bevause the clyinder pressures where higher...why metal multilayer gasket?...far better than the coopers shite.
Different builds for different applications..ALL reliable though.
Your all back in the past......lowering the comp will always mean safer ultimately but you sacrifice drivability.....but then your engine is far simpler specced compared to high comp...why was wrc long stud invented?..because cylinder pressures where higher and boost pressure was higher...they needed a better clamp to keep the head on!..Why linered blocks?..bevause the clyinder pressures where higher...why metal multilayer gasket?...far better than the coopers shite.
Different builds for different applications..ALL reliable though.
#168
Professional Waffler
Originally Posted by Bosch-Man
Gareth of course they know more now..do you think Julian Godfrey dont know his stuff? ...The fitter there has a 9-1 comp engine running 500bhp on pump fuel!......You are right about me not knowing though..i just drive em and build them to what i want it to be listening to people.
Your all back in the past......lowering the comp will always mean safer ultimately but you sacrifice drivability.....but then your engine is far simpler specced compared to high comp...why was wrc long stud invented?..because cylinder pressures where higher and boost pressure was higher...they needed a better clamp to keep the head on!..Why linered blocks?..bevause the clyinder pressures where higher...why metal multilayer gasket?...far better than the coopers shite.
Different builds for different applications..ALL reliable though.
Different builds for different applications..ALL reliable though.
designed for a totally different application than we use them for,,,
#169
Gareth both are though arnt they...touring cars were like 6.8-1 wernt they?...Rally cars are like 9.5-1 (YB) to me 8-1 is the perfect compression AS Ford made as road version
No idea on his geometry mate...i know they dont use std cranks or rods as they build VERY high speeced engines for rich people..LOL...but i do know that std bottom end has been used at 8.5-1 in rallycross by the budget teams at 750bhp and easily last the season!!! (on race fuel of course...pump fuel is 550bhp limit at 8-1)
Benn you WILL be in the 8's if its being built by them!
No idea on his geometry mate...i know they dont use std cranks or rods as they build VERY high speeced engines for rich people..LOL...but i do know that std bottom end has been used at 8.5-1 in rallycross by the budget teams at 750bhp and easily last the season!!! (on race fuel of course...pump fuel is 550bhp limit at 8-1)
Benn you WILL be in the 8's if its being built by them!
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arguments aside, ok so i have high (9.0) C/r , the engine/turbo is fine and well matched. so why does it det at anything above 1.2bar @ 336bhp?
my fuel system/injectors are not maxed out? and intercooling is very adequate?
my fuel system/injectors are not maxed out? and intercooling is very adequate?
#172
Professional Waffler
Originally Posted by leecavturbo
arguments aside, ok so i have high (9.0) C/r , the engine/turbo is fine and well matched. so why does it det at anything above 1.2bar @ 336bhp?
my fuel system/injectors are not maxed out? and intercooling is very adequate?
my fuel system/injectors are not maxed out? and intercooling is very adequate?
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Originally Posted by GARETH T
Originally Posted by leecavturbo
arguments aside, ok so i have high (9.0) C/r , the engine/turbo is fine and well matched. so why does it det at anything above 1.2bar @ 336bhp?
my fuel system/injectors are not maxed out? and intercooling is very adequate?
my fuel system/injectors are not maxed out? and intercooling is very adequate?
#174
Professional Waffler
Originally Posted by Bosch-Man
Gareth both are though arnt they...touring cars were like 6.8-1 wernt they?...Rally cars are like 9.5-1 (YB) to me 8-1 is the perfect compression AS Ford made as road version
No idea on his geometry mate...i know they dont use std cranks or rods as they build VERY high speeced engines for rich people..LOL...but i do know that std bottom end has been used at 8.5-1 in rallycross by the budget teams at 750bhp and easily last the season!!! (on race fuel of course...pump fuel is 550bhp limit at 8-1)
Benn you WILL be in the 8's if its being built by them!
Benn you WILL be in the 8's if its being built by them!
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Lee any ideas what EGT are on a good run?
How do you know it is det'ing and/or can't take anymore..........just beacuse the guy at noble said so??
If i were you i'd get it to someone who has experience with turbo mapping,i'm not so sure noble are to clued up myself.
How do you know it is det'ing and/or can't take anymore..........just beacuse the guy at noble said so??
If i were you i'd get it to someone who has experience with turbo mapping,i'm not so sure noble are to clued up myself.
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Originally Posted by GARETH T
when we start talking different engine geometry everything changed the same as different fuels
#177
Gareth your only talking det though...you can run more ignition the higher octane...it dont change the heat or pressure aspects?
The fact is the correct spec 9-1 engine will handle 750bhp no worries...on the road due to fuel 550bhp is about your limit.
My spec of engine on lo and hi comp 500bhp.
Lo comp:-
Std bottom end with lo comp std mahle type pistons grp a bolts
Std head bolts
coopers ring gasket
T4 turbo
Secret cams
Grp A ported head
hi comp
Linered block
Cossie racing pistons
WRC long studded conversion
Grp a bolts
Multi layer metal head gasket
T4 turbo
secret cams
Grp A ported head
You see the difference in what you NEED on the hi comp engine to keep it reliable over the lo comp version...yep cost alot more money BUT you get the all round REAL deal
The fact is the correct spec 9-1 engine will handle 750bhp no worries...on the road due to fuel 550bhp is about your limit.
My spec of engine on lo and hi comp 500bhp.
Lo comp:-
Std bottom end with lo comp std mahle type pistons grp a bolts
Std head bolts
coopers ring gasket
T4 turbo
Secret cams
Grp A ported head
hi comp
Linered block
Cossie racing pistons
WRC long studded conversion
Grp a bolts
Multi layer metal head gasket
T4 turbo
secret cams
Grp A ported head
You see the difference in what you NEED on the hi comp engine to keep it reliable over the lo comp version...yep cost alot more money BUT you get the all round REAL deal
#178
Professional Waffler
Originally Posted by GARETH T
PxLxAxN
cylinderPRSSURE x strokeLength x boreAREA x NUMBER of power strokes = BHP
cylinderPRSSURE x strokeLength x boreAREA x NUMBER of power strokes = BHP
mean cylinderPRSSURE x strokeLength x boreAREA x NUMBER of power strokes = BHP
#179
Professional Waffler
Originally Posted by Bosch-Man
Gareth your only talking det though...you can run more ignition the higher octane...it dont change the heat or pressure aspects?
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Originally Posted by Rs1
Lee any ideas what EGT are on a good run?
How do you know it is det'ing and/or can't take anymore..........just beacuse the guy at noble said so??
If i were you i'd get it to someone who has experience with turbo mapping,i'm not so sure noble are to clued up myself.
How do you know it is det'ing and/or can't take anymore..........just beacuse the guy at noble said so??
If i were you i'd get it to someone who has experience with turbo mapping,i'm not so sure noble are to clued up myself.
#182
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Originally Posted by leecavturbo
Originally Posted by GARETH T
Originally Posted by leecavturbo
arguments aside, ok so i have high (9.0) C/r , the engine/turbo is fine and well matched. so why does it det at anything above 1.2bar @ 336bhp?
my fuel system/injectors are not maxed out? and intercooling is very adequate?
my fuel system/injectors are not maxed out? and intercooling is very adequate?
You are correct though about adding heat when you retard it. So its seems a no win situation at present.
#183
Sorry to butt in...
I run a Rover (don't laugh) engine that's 86.4mm stroke and 92mm bore.
Compression is 8.6:1
Makes 370hp at the wheels at 1.6bar and has advance of about 13deg at 6500rpm and 1.6bar.
It's all about teh design of the pistons, bowl shape in the head, etc.
I can't see the merits of 7.x:1 compression and 2+bar of boost myself.
I run a Rover (don't laugh) engine that's 86.4mm stroke and 92mm bore.
Compression is 8.6:1
Makes 370hp at the wheels at 1.6bar and has advance of about 13deg at 6500rpm and 1.6bar.
It's all about teh design of the pistons, bowl shape in the head, etc.
I can't see the merits of 7.x:1 compression and 2+bar of boost myself.
#184
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cylinderPRSSURE x strokeLength x boreAREA x NUMBER of power strokes = BHP
So number of power strokes is just the rev limit - lets say its the same for both engines.
So power produced comes down to purely the peak cylinder pressures, as everything else is equal. Surely peak cylinder pressures are the same with both high comp and low comp as you'd run as much as reliably possible to make as much power? So even though your stuffing 2 bar of boost into a low comp motor, the peak pressures are the same as stuffing 1 bar into a high comp motor? Therefore they both make the same power?
Anyone with me so far, or have I cocked it up?
#185
DEYTUKURJERBS
Scruffy-No, not by a long shot,ifthat was true there would be no reason for low compression, hell, barely a reason for turbos at all, just crazy high comp non turbo cars.
You think drag cars run compression down into the 5s for fun?
That countless works race cars ran 6/7:1 compresssion and sometimes over 60psi boost just for the crack?
No, me either.
You think drag cars run compression down into the 5s for fun?
That countless works race cars ran 6/7:1 compresssion and sometimes over 60psi boost just for the crack?
No, me either.
#186
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Sorry for sounding thick, but cant the people complaining about off boost response/drivabilty just change the gearing? off boost response only really affects road driving, you dont need a road car geared to do 190+ or whatever a standard T5 is geared to, surely thats the best of both worlds, low comp reliability with decent response.
It would seem ilogical to me to have an engine built on the side of less reliabilty just for the sake of about 5% of driving off boost, hey, theres always the gearstick, thats the cheapest way to cure response you can get
It would seem ilogical to me to have an engine built on the side of less reliabilty just for the sake of about 5% of driving off boost, hey, theres always the gearstick, thats the cheapest way to cure response you can get
#187
Did Someone Mention TUV
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Originally Posted by grant620
Sorry to butt in...
I run a Rover (don't laugh) engine that's 86.4mm stroke and 92mm bore.
Compression is 8.6:1
Makes 370hp at the wheels at 1.6bar and has advance of about 13deg at 6500rpm and 1.6bar.
It's all about the design of the pistons, bowl shape in the head, etc.
I can't see the merits of 7.x:1 compression and 2+bar of boost myself.
I run a Rover (don't laugh) engine that's 86.4mm stroke and 92mm bore.
Compression is 8.6:1
Makes 370hp at the wheels at 1.6bar and has advance of about 13deg at 6500rpm and 1.6bar.
It's all about the design of the pistons, bowl shape in the head, etc.
I can't see the merits of 7.x:1 compression and 2+bar of boost myself.
#188
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Why have we not seen any of these high compression cars perform at Bruntingthorpe (on normal super)?
I have tested high compression, and in my application (track days etc) it was not suitable.
Remember when I first did my engine three years ago and one of the pistons cracked within 1500miles at Bedford (no det, just the side loads on the piston edges created by PCPs that were too high due to running 8:1 compression and 1.8 bar with a T4)? And I was using longer rods AND JE pistons as well . Driving it on the road, no problem what-so-ever. Ten laps at Bedford, cracks (literally) in the high compression armour were showing through .
In the end we had to switch back to standard rods and short compression height Accralite pistons as I was not prepared to risk the engine letting go catastrophically, and since then - total reliability for 35k - even though IMO, the compression is still too high for my application at 7.54:1, as I still see 900+°C at high rpm in fifth and wouldn't be happy maxing the engine out at Brunters without race fuel....
Moving on to what I mentioned about turbos earlier in the post, I finally managed to get some photos of what running heavily retarded ignition (needed on high compression engines) does to them (8° on top line):
See how it has nibbled away at the edges - the engine was still perfect, although there was a concern for the exhaust valves, but these were okay .
Just so you can see that it wasn't a blade that let go or shrapnel from an engine failure - all blades still fully in-tact.
Still want high compression YB? Then change the gearing and don't use as a road car or drive like a girl and never use the power or run low boost . YB's and their bore / rod size don't like high compression* (*please note that rallying / rally-cross is totally different and due to low gearing and lack of sustained load mileage can get away with higher compression).
For your information Evos do a similar thing, they are running high compression (8.5:1 to 8.8:1 depending on model year) and heavily retarded ignition on the top-line, that the standard turbos REGULARLY fall apart due to heat damage - ask any Evo tuner / turbo supplier .
I have tested high compression, and in my application (track days etc) it was not suitable.
Remember when I first did my engine three years ago and one of the pistons cracked within 1500miles at Bedford (no det, just the side loads on the piston edges created by PCPs that were too high due to running 8:1 compression and 1.8 bar with a T4)? And I was using longer rods AND JE pistons as well . Driving it on the road, no problem what-so-ever. Ten laps at Bedford, cracks (literally) in the high compression armour were showing through .
In the end we had to switch back to standard rods and short compression height Accralite pistons as I was not prepared to risk the engine letting go catastrophically, and since then - total reliability for 35k - even though IMO, the compression is still too high for my application at 7.54:1, as I still see 900+°C at high rpm in fifth and wouldn't be happy maxing the engine out at Brunters without race fuel....
Moving on to what I mentioned about turbos earlier in the post, I finally managed to get some photos of what running heavily retarded ignition (needed on high compression engines) does to them (8° on top line):
See how it has nibbled away at the edges - the engine was still perfect, although there was a concern for the exhaust valves, but these were okay .
Just so you can see that it wasn't a blade that let go or shrapnel from an engine failure - all blades still fully in-tact.
Still want high compression YB? Then change the gearing and don't use as a road car or drive like a girl and never use the power or run low boost . YB's and their bore / rod size don't like high compression* (*please note that rallying / rally-cross is totally different and due to low gearing and lack of sustained load mileage can get away with higher compression).
For your information Evos do a similar thing, they are running high compression (8.5:1 to 8.8:1 depending on model year) and heavily retarded ignition on the top-line, that the standard turbos REGULARLY fall apart due to heat damage - ask any Evo tuner / turbo supplier .
#190
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Originally Posted by SECS
Mike,
If your high comp spec damaged your engine in anyway then it wasnt
specced/mapped properly or had a fault.
If your high comp spec damaged your engine in anyway then it wasnt
specced/mapped properly or had a fault.
As to you comment, about it being a problem with the map, it did the journey to the Ring as it's running-in period (as it was finished at nidnight the night before ), dropped the oil out, ragged it round the 'Ring (on only 1.4 bar of boost, as it hadn't been det checked in the car at full boost) and drove back - again no problem. The boost was then raised to it's dyno figure, det checked and all was spot on. Drove the car to Bedford, 10 laps, piston 2 didn't like the PCPs that 1.8 bar was creating with the T4 and the rest is history...
That's the problem with high comp as well, the safety margins are narrowed considerably....
#191
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Originally Posted by Stavros
Scruffy-No, not by a long shot,ifthat was true there would be no reason for low compression, hell, barely a reason for turbos at all, just crazy high comp non turbo cars.
You think drag cars run compression down into the 5s for fun?
That countless works race cars ran 6/7:1 compresssion and sometimes over 60psi boost just for the crack?
No, me either.
You think drag cars run compression down into the 5s for fun?
That countless works race cars ran 6/7:1 compresssion and sometimes over 60psi boost just for the crack?
No, me either.
#192
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Originally Posted by scruffythefirst
Originally Posted by Stavros
Scruffy-No, not by a long shot,ifthat was true there would be no reason for low compression, hell, barely a reason for turbos at all, just crazy high comp non turbo cars.
You think drag cars run compression down into the 5s for fun?
That countless works race cars ran 6/7:1 compresssion and sometimes over 60psi boost just for the crack?
No, me either.
You think drag cars run compression down into the 5s for fun?
That countless works race cars ran 6/7:1 compresssion and sometimes over 60psi boost just for the crack?
No, me either.
Look at what Lee has posted about his Cavalier, he is running 9:1 compression, but can only run 1.2 bar of boost, because it dets beyond that and only makes 336bhp.
If he lowered the compression, it would allow him to run more boost and exceed this figure. More boost = greater air flow for the given PCP = more power.
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Originally Posted by markk
right im now going to 'unwatch' this topic as its got to the very boring stage of this topic again as it has soooooo many times
Had a good read of this topic as it seemed to be one of the more interesting ones on here at the moment.
I personally don't think you have any idea about high/low comp or performance engines in general as you seem totally incapable of backing up your argument! So if your not really as ignorant as you appear then lets hear some proper techincal argument from you...........
#195
Originally Posted by Mike Rainbird
.............and the engine was back together and running (lower compression) within a few days........
#196
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Mike,
I wasnt dissing your map, just giving all possibilities.
What I was getting at is....
ANY engine no matter what CR should have suitable safety margins built
in.
If margins are breached/not set up properly then it will cause problems
for any given CR.
I wasnt dissing your map, just giving all possibilities.
What I was getting at is....
ANY engine no matter what CR should have suitable safety margins built
in.
If margins are breached/not set up properly then it will cause problems
for any given CR.
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Mike R.
Did you have your injectors flow tested when your engine went? Did you have EGT sensors on every tube? Just out of interest
ps. Friend of mine uses standard bottom end with 8:1 compression with Holset HX40 turbo (60/65mm wheels) and he runs almost 20deg advance on 6500rpm and 1.8bar. And he uses standard 98ron fuel. I think that 8-8.5:1 compression is widely used in scandinavia as far as I know
Did you have your injectors flow tested when your engine went? Did you have EGT sensors on every tube? Just out of interest
ps. Friend of mine uses standard bottom end with 8:1 compression with Holset HX40 turbo (60/65mm wheels) and he runs almost 20deg advance on 6500rpm and 1.8bar. And he uses standard 98ron fuel. I think that 8-8.5:1 compression is widely used in scandinavia as far as I know
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No, he's say you get LOWER PCPs with low comp.
If he lowered the compression, it would allow him to run more boost and exceed this figure. More boost = greater air flow for the given PCP = more power.
If he lowered the compression, it would allow him to run more boost and exceed this figure. More boost = greater air flow for the given PCP = more power.
cylinderPRSSURE x strokeLength x boreAREA x NUMBER of power strokes = BHP
I get that with low comp you can burn more fuel and air per cycle as you have more volume to fit the uncompresed air in before the dynamic CR gets too high, but how does that give you more power if the PCP is the same?
#200
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Originally Posted by leecavturbo
arguments aside, ok so i have high (9.0) C/r , the engine/turbo is fine and well matched. so why does it det at anything above 1.2bar @ 336bhp?
my fuel system/injectors are not maxed out? and intercooling is very adequate?
my fuel system/injectors are not maxed out? and intercooling is very adequate?
Why dont you try de-compressing the engine with a de-comp plate, then doing a det check?
That way you'll have the benchmarks to make an informed judgment on this debate....
Ian