Oxygenated fuel
12 posts
• Page 1 of 1
Post by: griffo » Mon Mar 20, 2000 7:23 pm
I would be interested to hear from list members regarding their experiences
with the current pump gas available in the U S. In talking to the machine
shop that is machining my twincam , we were discussing comp. ratios, he
warned me that current pump gas can have anywhere between 20% to 80% ethanol
additive. That there is no government control over the amount that is added.
This is causing a lot of burned pistons and valves on ratios of 10:1 or
higher. All because of oxygenation. He is advising me that with 10.25 : 1 to
use non oxy gas and use a booster to prevent it from burning up. Getting race
fuel is getting harder to get off the track in the Midwest (mpls)
I'll be interested in your comments
Thanks
Peter Griffin
with the current pump gas available in the U S. In talking to the machine
shop that is machining my twincam , we were discussing comp. ratios, he
warned me that current pump gas can have anywhere between 20% to 80% ethanol
additive. That there is no government control over the amount that is added.
This is causing a lot of burned pistons and valves on ratios of 10:1 or
higher. All because of oxygenation. He is advising me that with 10.25 : 1 to
use non oxy gas and use a booster to prevent it from burning up. Getting race
fuel is getting harder to get off the track in the Midwest (mpls)
I'll be interested in your comments
Thanks
Peter Griffin
- griffo
- First Gear
- Posts: 26
- Joined: 15 Aug 2016
Post by: rodney » Mon Mar 20, 2000 10:21 pm
At 02:23 PM 3/20/00 -0500, you wrote:
We car drivers in Australia have had a similar problem arise in that
toluene was being added to the fuel to reduce the amount of tax the
suppliers were paying. There has not been any actual proof thatthis
damaged any engines, but it probably has.
On compression ratios, I was working out mine the other night and I would
like to see what others think of my method.
Measured the capacity of the combustion chamber 33 milliLitres.
Calculated the swept capacity of the = 399.5 mL
Compesion ratio = (swept capacity + combustion capacity)/combustion capacity
= (399.5 + 33)/33
= 13.1
This seems high but the bore is 83.5mm and the head has had a fair bit of
scimming over the years.
It has been running fine on Super Leaded (95-96 octane I think) petrol with
no addatives.
Rodney Stevens
Email: ***@***.***
Work Phone: 61 2 97106701
Work Fax: 61 2 97106789
Email: ***@***.***
Elan SS s/e 45/7616
http://sites.netscape.net/rodjohnstevens/homepage
We car drivers in Australia have had a similar problem arise in that
toluene was being added to the fuel to reduce the amount of tax the
suppliers were paying. There has not been any actual proof thatthis
damaged any engines, but it probably has.
On compression ratios, I was working out mine the other night and I would
like to see what others think of my method.
Measured the capacity of the combustion chamber 33 milliLitres.
Calculated the swept capacity of the = 399.5 mL
Compesion ratio = (swept capacity + combustion capacity)/combustion capacity
= (399.5 + 33)/33
= 13.1
This seems high but the bore is 83.5mm and the head has had a fair bit of
scimming over the years.
It has been running fine on Super Leaded (95-96 octane I think) petrol with
no addatives.
Rodney Stevens
Email: ***@***.***
Work Phone: 61 2 97106701
Work Fax: 61 2 97106789
Email: ***@***.***
Elan SS s/e 45/7616
http://sites.netscape.net/rodjohnstevens/homepage
- rodney
- Second Gear
- Posts: 220
- Joined: 03 Jun 2007
Post by: lawrence at promobility.n » Tue Mar 21, 2000 2:36 am
Hi Rodney:
The computation looks mostly correct but I think you missed the small
volume at the top of the cylinder, plus the thickness of the gasket in
your computations. If the piston comes within X mm of the top of the
block, and the gasket is Y mm thick then you have an additional volume
in the combustion chamber of (X+Y)*(Pi*piston_radius^2) mL. Lets say
this adds 10ml to the virtual combustion chamber size then your
compression ratio drops to 10.3 which seems more reasonable.
-Lawrence-
Rodney Stevens wrote:
--
Lawrence King Ottawa Ontario Canada
http://www.promobility.net/lawrence
I am reading a very interesting book about anti-gravity.
I just can't put it down.
The computation looks mostly correct but I think you missed the small
volume at the top of the cylinder, plus the thickness of the gasket in
your computations. If the piston comes within X mm of the top of the
block, and the gasket is Y mm thick then you have an additional volume
in the combustion chamber of (X+Y)*(Pi*piston_radius^2) mL. Lets say
this adds 10ml to the virtual combustion chamber size then your
compression ratio drops to 10.3 which seems more reasonable.
-Lawrence-
Rodney Stevens wrote:
--
Lawrence King Ottawa Ontario Canada
http://www.promobility.net/lawrence
I am reading a very interesting book about anti-gravity.
I just can't put it down.
- lawrence at promobility.n
Post by: rodney » Tue Mar 21, 2000 11:17 pm
Lawrence at 09:36 PM 3/20/00 -0500, you wrote:
Yes I did forget the gasket thickness and the small capacity of the valve
cut outs in the piston. The piston deck was flush with the top of the
block, but ther was a small relief around the rim. These would add about 2
mL to the capacity.
With varying gaskets 1mm, 1.5mm and 2mm the ratios come out to 11.4 10.7
10.3 to 1 so things are not as bad as I thought.
Rod
Rodney Stevens
Email: ***@***.***
Work Phone: 61 2 97106701
Work Fax: 61 2 97106789
Email: ***@***.***
Elan SS s/e 45/7616
http://sites.netscape.net/rodjohnstevens/homepage
Yes I did forget the gasket thickness and the small capacity of the valve
cut outs in the piston. The piston deck was flush with the top of the
block, but ther was a small relief around the rim. These would add about 2
mL to the capacity.
With varying gaskets 1mm, 1.5mm and 2mm the ratios come out to 11.4 10.7
10.3 to 1 so things are not as bad as I thought.
Rod
Rodney Stevens
Email: ***@***.***
Work Phone: 61 2 97106701
Work Fax: 61 2 97106789
Email: ***@***.***
Elan SS s/e 45/7616
http://sites.netscape.net/rodjohnstevens/homepage
- rodney
- Second Gear
- Posts: 220
- Joined: 03 Jun 2007
Post by: griffo » Wed Mar 22, 2000 3:12 pm
car event that someone had compiled a list of independent petrol (gas)
stations in and around Minneapolis that supplied non oxygenated gas. After
much digging through my motor stuff I found it. It has about 90 members of
the Minnesota Service Stations that support non oxy gas. I expect if other
members check their area that there will be gas stations that also supply non
oxy gas.
Regards.
Peter Griffin
- griffo
- First Gear
- Posts: 26
- Joined: 15 Aug 2016
Post by: TJECK at MEDIAONE.NET » Thu Mar 23, 2000 3:03 am
Here's my spin on compression ratio's - pardon the length and the pedantic
tone. I've been blabbing on the damned phone all day and figure hey why stop
now.
Usable compression ratio varies between engines and applications. As a gross
approximation engines with smaller bores, running at higher rpms with
aluminum heads and modern combustion chambers (read twin cam) can run higher
compression ratio's than slow turning, big bored, iron headed, poorly
combusted engines. I leave out here any consideration of electronic control
of ignition or fuel.
In a twin cam, as in other engines, maximum compression ratio depends on
fuel octane, application (race or street or mixed use), cam (longer duration
cams can run higher compression ratios) and valve size as the most important
of many parameters. The owner's driving style _greatly_ affects what
compression ratio is most appropriate.
It's also important to know that increasing the compression ratio vastly
increases the loading on pistons, rods, (especially rods) bearings etc. I
believe stresses go up as the square of the compression ratio increase, if
memory serves me right. If you are increasing your compression ratio you
need to make damned sure everything is mechanically spot on.
In my experience, admittedly somewhat limited, street twin cams can run
10.25:1 compression ratios, found by the method detailed below, on USA 92
RON unleaded gas with sprint or better cams and used in a "spirited"
fashion. This compression ratio will not require use of octane boosters,
provided fuel and ignition are properly tailored. But don't whine to me if
you use this info and your engine knocks like crazy. If I built it I'll fix
it, if you built it you......
Higher compression ratio's can be used on engines that get higher octane gas
and have modified valve trains. I get a little nervous giving a customer a
compression ration higher than 11.5:1 unless he/she is a racer. I don't do
race engines per se. Be aware that current compression ratios on racing TC
motors are quite high compared to what was previously thought usable. (eg
14.5:1 +). One of the biggest factors governing max compression ratio on
TC's is the size of the pop up (dome) on the piston, which intrudes into the
combustion chamber, gives a poor chamber shape and interferes with flame
propagation.
When I build an engine I spend way more time pondering the above questions
than I do on the following tedious but simple measurement and calculation
procedures.
Measuring compression ratio:
I believe this to be to an SAE spec. But I don't know shi....
Pardon the english explanations if you're a math person - most folks don't
seem to be.
The basic idea:
Compression Ratio is the ratio of the swept volume (displacement) to the
unswept volume (combustion chamber volume + volume of deck height +volume
displaced or absorbed by the piston (dome, cut outs etc) + volume of head
gasket + volume of space above piston rings (around the perimeter of the
piston above the compression ring.)) It is generally shown something like
this: CR=(SV + CV ) / CV . CV means Combustion Volume. And is all the crap
called uswept volume above. Each item is computed or measured.
Said another way:
Compression Ratio states how much the air sucked into the engine by the
piston is squashed into the small volume of the combustion chamber. It is
assumed that the combustion chamber, though not "swept" by the piston, is
also filled. Note another assumption embedded in this formula - that we are
obtaining 100% cylinder filling to atmospheric pressure - this is certainly
not true at partial throttle! The ratio stays the same but the pressures
involved will be much lower. This is a static simplification of a dynamic
process.
SWEPT volume is computed by figuring the displacement of one cylinder (1/2
bore squared x stroke x PI) (the area of a circle times the stroke) PI is
good enough at 3.14159265358979323846 (hah ha just kidding).
COMBUSTION chamber volume is measured by CCing the combustion chamber
Volume of DECK HEIGHT (the distance from the flat part of the piston to the
top of the block) is computed by measuring the piston to top of block
clearance at TDC and multiplying by 1/2 the bore squared x PI. Typical deck
height on a twin cam is .025 inches. You are essentially doing the swept
volume step but pretending the stroke is only as long as the deck height. I
don't build engines with stock deck heights.
Volume of HEAD GASKET is computed by measuring the bore of the gasket
dividing by 2, squaring, then multiplying by PI (again the area of a
circle). Then multiplying by the crushed thickness of the gasket - .020
inches is a good approximation to crushed gasket height on a stock twin cam
gasket. The diameter of the hole in the head gasket is larger than the bore.
Volume of RING LAND: You can compute this or measure it in the method
described below. If you compute it: You need to get the volume of the
annular area above the top ring on the piston (diff between piston head
diameter and bore dia.) To do so compute the volume of the bore then
subtract the volume of the piston. The difference will be the volume of this
land. (The top of a piston is roughly .050 inches less that the bore dia. -
actual piston clearance is measured low down on the piston skirt).The top
ring is usually a quarter inch down from the top of the piston. So: .250 x
(bore/2)^2 x PI minus .250 x (piston dia/2)^2 x PI. (Subtract one circle's
area from a larger encompassing circular area and you get the difference
between them. Multiply by their height and you get the volume of a ring.)
I'm starting to run out of gas here.... A diagram makes this all a bit
easier. Maybe I'll save this to the web site and add a picture.
The piston top isn't flat, it has a slight dome in it and cutouts for the
valves. How do you figure out how much the pop up takes away and the valve
reliefs add to the combustion chamber volume?
The following procedure measures how much space the pop up in the piston
takes, plus how much space is added by the cutouts for the valves (valve
reliefs). It also happens to include the ring land volume. Again, as in the
ring land computation, the trick is a subtraction. Put rings on the piston
and put it in the bore. Push it down a measured amount, say one quarter
inch. Compute this volume as above (area of circle x depth down (.250)).
Write this down. Now cc this area like you would a combustion chamber -
you'll get a reading. If you had a perfectly flat piston occupying the whole
space then your measured volume would exactly match your computed volume.
But your piston ain't flat, it's slightly domed and has cut outs for the
valves. Plus it's smaller than the bore. So if you subtract the measured
from the computed volumes you willl get how much space the pop up occupies,
or the valve reliefs give. Plus you'll pick up the ring land volume. The
number might be a plus or a minus depending on the relative sizes of the
cutouts and pop up.
OK so now you have your bits: You have measured the combustion chamber
volume, you've measured the amount of space the pop up uses or the valve
reliefs add, you have the volume of the deck height and of the head gasket.
You will have to do conversions between metric and inch volumes. 1000 cc =
61.14 cubic inches. Put the bits together and you get the compression ratio:
(displacement +combustion chamber +head gasket +deck height +piston volume)
divided by (combustion chamber + head gasket +deck height +piston volume)
equals the compression ratio. If you measured the piston volume
differerently from above, you need to include a number for the ring land
volume on both sides of the division above.
Voila, jeez, finally.
I don't go getting all carried away using lots of decimal places. When I say
I use 10.25:1 as a goal what I really get is somewhere between 10.2 and
10.3. I try, on any particular engine, by massaging various parts, to get
the compression ratios to be within .1 of each other. eg. cyl 1 is 10.15.
Cyl 4 is 10.25. It's easier to do than the above makes it sound. I do this
all ahead of time by measuring and figuring and fettling. The final build is
anticlimatic.
I'll toss a speadsheet on the website (
http://people.ne.mediaone.net/tjeck/index.html ) that allows you to just
fill in the numbers, but please be clear on the concept.
The above is the standard agreed-on method of computing compression ratio's.
There is no reason something else couldn't be used, but it would then be
difficult to compare notes. The above may or may not be the "compression
ratio" you will be quoted by any particular person or magazine article. But
if they aren't using this formula, I think, to interject a note of
personality here, they have their heads up their asses. And I'm a pretty
easy going kinda guy.
--Tom ... you use any of the above info at your peril....
tone. I've been blabbing on the damned phone all day and figure hey why stop
now.
Usable compression ratio varies between engines and applications. As a gross
approximation engines with smaller bores, running at higher rpms with
aluminum heads and modern combustion chambers (read twin cam) can run higher
compression ratio's than slow turning, big bored, iron headed, poorly
combusted engines. I leave out here any consideration of electronic control
of ignition or fuel.
In a twin cam, as in other engines, maximum compression ratio depends on
fuel octane, application (race or street or mixed use), cam (longer duration
cams can run higher compression ratios) and valve size as the most important
of many parameters. The owner's driving style _greatly_ affects what
compression ratio is most appropriate.
It's also important to know that increasing the compression ratio vastly
increases the loading on pistons, rods, (especially rods) bearings etc. I
believe stresses go up as the square of the compression ratio increase, if
memory serves me right. If you are increasing your compression ratio you
need to make damned sure everything is mechanically spot on.
In my experience, admittedly somewhat limited, street twin cams can run
10.25:1 compression ratios, found by the method detailed below, on USA 92
RON unleaded gas with sprint or better cams and used in a "spirited"
fashion. This compression ratio will not require use of octane boosters,
provided fuel and ignition are properly tailored. But don't whine to me if
you use this info and your engine knocks like crazy. If I built it I'll fix
it, if you built it you......
Higher compression ratio's can be used on engines that get higher octane gas
and have modified valve trains. I get a little nervous giving a customer a
compression ration higher than 11.5:1 unless he/she is a racer. I don't do
race engines per se. Be aware that current compression ratios on racing TC
motors are quite high compared to what was previously thought usable. (eg
14.5:1 +). One of the biggest factors governing max compression ratio on
TC's is the size of the pop up (dome) on the piston, which intrudes into the
combustion chamber, gives a poor chamber shape and interferes with flame
propagation.
When I build an engine I spend way more time pondering the above questions
than I do on the following tedious but simple measurement and calculation
procedures.
Measuring compression ratio:
I believe this to be to an SAE spec. But I don't know shi....
Pardon the english explanations if you're a math person - most folks don't
seem to be.
The basic idea:
Compression Ratio is the ratio of the swept volume (displacement) to the
unswept volume (combustion chamber volume + volume of deck height +volume
displaced or absorbed by the piston (dome, cut outs etc) + volume of head
gasket + volume of space above piston rings (around the perimeter of the
piston above the compression ring.)) It is generally shown something like
this: CR=(SV + CV ) / CV . CV means Combustion Volume. And is all the crap
called uswept volume above. Each item is computed or measured.
Said another way:
Compression Ratio states how much the air sucked into the engine by the
piston is squashed into the small volume of the combustion chamber. It is
assumed that the combustion chamber, though not "swept" by the piston, is
also filled. Note another assumption embedded in this formula - that we are
obtaining 100% cylinder filling to atmospheric pressure - this is certainly
not true at partial throttle! The ratio stays the same but the pressures
involved will be much lower. This is a static simplification of a dynamic
process.
SWEPT volume is computed by figuring the displacement of one cylinder (1/2
bore squared x stroke x PI) (the area of a circle times the stroke) PI is
good enough at 3.14159265358979323846 (hah ha just kidding).
COMBUSTION chamber volume is measured by CCing the combustion chamber
Volume of DECK HEIGHT (the distance from the flat part of the piston to the
top of the block) is computed by measuring the piston to top of block
clearance at TDC and multiplying by 1/2 the bore squared x PI. Typical deck
height on a twin cam is .025 inches. You are essentially doing the swept
volume step but pretending the stroke is only as long as the deck height. I
don't build engines with stock deck heights.
Volume of HEAD GASKET is computed by measuring the bore of the gasket
dividing by 2, squaring, then multiplying by PI (again the area of a
circle). Then multiplying by the crushed thickness of the gasket - .020
inches is a good approximation to crushed gasket height on a stock twin cam
gasket. The diameter of the hole in the head gasket is larger than the bore.
Volume of RING LAND: You can compute this or measure it in the method
described below. If you compute it: You need to get the volume of the
annular area above the top ring on the piston (diff between piston head
diameter and bore dia.) To do so compute the volume of the bore then
subtract the volume of the piston. The difference will be the volume of this
land. (The top of a piston is roughly .050 inches less that the bore dia. -
actual piston clearance is measured low down on the piston skirt).The top
ring is usually a quarter inch down from the top of the piston. So: .250 x
(bore/2)^2 x PI minus .250 x (piston dia/2)^2 x PI. (Subtract one circle's
area from a larger encompassing circular area and you get the difference
between them. Multiply by their height and you get the volume of a ring.)
I'm starting to run out of gas here.... A diagram makes this all a bit
easier. Maybe I'll save this to the web site and add a picture.
The piston top isn't flat, it has a slight dome in it and cutouts for the
valves. How do you figure out how much the pop up takes away and the valve
reliefs add to the combustion chamber volume?
The following procedure measures how much space the pop up in the piston
takes, plus how much space is added by the cutouts for the valves (valve
reliefs). It also happens to include the ring land volume. Again, as in the
ring land computation, the trick is a subtraction. Put rings on the piston
and put it in the bore. Push it down a measured amount, say one quarter
inch. Compute this volume as above (area of circle x depth down (.250)).
Write this down. Now cc this area like you would a combustion chamber -
you'll get a reading. If you had a perfectly flat piston occupying the whole
space then your measured volume would exactly match your computed volume.
But your piston ain't flat, it's slightly domed and has cut outs for the
valves. Plus it's smaller than the bore. So if you subtract the measured
from the computed volumes you willl get how much space the pop up occupies,
or the valve reliefs give. Plus you'll pick up the ring land volume. The
number might be a plus or a minus depending on the relative sizes of the
cutouts and pop up.
OK so now you have your bits: You have measured the combustion chamber
volume, you've measured the amount of space the pop up uses or the valve
reliefs add, you have the volume of the deck height and of the head gasket.
You will have to do conversions between metric and inch volumes. 1000 cc =
61.14 cubic inches. Put the bits together and you get the compression ratio:
(displacement +combustion chamber +head gasket +deck height +piston volume)
divided by (combustion chamber + head gasket +deck height +piston volume)
equals the compression ratio. If you measured the piston volume
differerently from above, you need to include a number for the ring land
volume on both sides of the division above.
Voila, jeez, finally.
I don't go getting all carried away using lots of decimal places. When I say
I use 10.25:1 as a goal what I really get is somewhere between 10.2 and
10.3. I try, on any particular engine, by massaging various parts, to get
the compression ratios to be within .1 of each other. eg. cyl 1 is 10.15.
Cyl 4 is 10.25. It's easier to do than the above makes it sound. I do this
all ahead of time by measuring and figuring and fettling. The final build is
anticlimatic.
I'll toss a speadsheet on the website (
http://people.ne.mediaone.net/tjeck/index.html ) that allows you to just
fill in the numbers, but please be clear on the concept.
The above is the standard agreed-on method of computing compression ratio's.
There is no reason something else couldn't be used, but it would then be
difficult to compare notes. The above may or may not be the "compression
ratio" you will be quoted by any particular person or magazine article. But
if they aren't using this formula, I think, to interject a note of
personality here, they have their heads up their asses. And I'm a pretty
easy going kinda guy.
--Tom ... you use any of the above info at your peril....
- TJECK at MEDIAONE.NET
Post by: par-olof.hakansson at gam » Thu Mar 23, 2000 9:01 am
Hi
Tom Eckstein wrote:
Check out http://www.gmeurope.com/saab/engine.html to see how SAAB's
innovative engine designer Per Gillbrand has solved the problem.
Best regards,
P-O H?kansson +2 S130/5 #73120378M
(who will do his first testdrive with his restored Plus 2 on Saturday
Tom Eckstein wrote:
Check out http://www.gmeurope.com/saab/engine.html to see how SAAB's
innovative engine designer Per Gillbrand has solved the problem.
Best regards,
P-O H?kansson +2 S130/5 #73120378M
(who will do his first testdrive with his restored Plus 2 on Saturday
- par-olof.hakansson at gam
Post by: Foxie » Fri Mar 24, 2000 1:43 am
-----Original Message-----
From: ***@***.*** <***@***.***>
To: ***@***.*** <***@***.***>
Date: 23 March 2000 09:01
Subject: [LotusElan.net] Re: Compression ratio. (long)
Best wishes for your test drive on Saturday !
I visited the SAAB site to see the variable compression engine, but I did
not find out how it works. (I physically visited SAAB in Trollhatten two
years ago, my brother-in-law does component work for them, some nice old
timers there in the museum !)
My late tutor Professor Seamus Timoney of University College Dublin
developed a variable compression two-stroke diesel many years ago. Two
opposed pistons operated in the same cylinder, with variable eccentric
rocker shafts connecting the conrods to a common crankshaft. Is the SAAB
engine a development of this ?
Sean Murray
From: ***@***.*** <***@***.***>
To: ***@***.*** <***@***.***>
Date: 23 March 2000 09:01
Subject: [LotusElan.net] Re: Compression ratio. (long)
Best wishes for your test drive on Saturday !
I visited the SAAB site to see the variable compression engine, but I did
not find out how it works. (I physically visited SAAB in Trollhatten two
years ago, my brother-in-law does component work for them, some nice old
timers there in the museum !)
My late tutor Professor Seamus Timoney of University College Dublin
developed a variable compression two-stroke diesel many years ago. Two
opposed pistons operated in the same cylinder, with variable eccentric
rocker shafts connecting the conrods to a common crankshaft. Is the SAAB
engine a development of this ?
Sean Murray
-
Foxie - Coveted Fifth Gear
- Posts: 1634
- Joined: 20 Sep 2003
Post by: par-olof.hakansson at gam » Fri Mar 24, 2000 11:39 am
Hi again
Sean Murray checked out the link I supplied:
Sorry, I saw the figures at that location and thought that they showed the
rubber bellows that makes it possible to change the volumes of the
combustion chambers, and since I already knew about that I thought it was
crystal clear... So check out
http://www.autoworld.com/news/saab/saab ... ession.asp
for a textual description and look at
http://www.gmeurope.com/saab/engine.html for illustrations.
a galvanized chassis so who cares!
Regards,
P-O
Sean Murray checked out the link I supplied:
Sorry, I saw the figures at that location and thought that they showed the
rubber bellows that makes it possible to change the volumes of the
combustion chambers, and since I already knew about that I thought it was
crystal clear... So check out
http://www.autoworld.com/news/saab/saab ... ession.asp
for a textual description and look at
http://www.gmeurope.com/saab/engine.html for illustrations.
a galvanized chassis so who cares!
Regards,
P-O
- par-olof.hakansson at gam
Post by: Rob_LaMoreaux » Fri Mar 24, 2000 3:35 pm
So this takes us full circle to last weeks contest whose answer was
integral head and cylinders. Looks like a valve job is going to be
expensive on the VCR Saabs.
Robert D. LaMoreaux
BT Electronics LLC
22700 Heslip Dr.
NoVI, MI 48375
Phone:(248)-449-8284
Fax:(248)-449-2577
Email:***@***.***
Alternate Email:***@***.***
integral head and cylinders. Looks like a valve job is going to be
expensive on the VCR Saabs.
Robert D. LaMoreaux
BT Electronics LLC
22700 Heslip Dr.
NoVI, MI 48375
Phone:(248)-449-8284
Fax:(248)-449-2577
Email:***@***.***
Alternate Email:***@***.***
- Rob_LaMoreaux
- Fourth Gear
- Posts: 968
- Joined: 22 Sep 2003
Post by: Foxie » Sat Mar 25, 2000 12:52 am
-----Original Message-----
From: ***@***.*** <***@***.***>
To: ***@***.*** <***@***.***>
Date: 24 March 2000 11:39
Subject: [LotusElan.net] Re: Compression ratio.
Hi P-O
Thanks for your SAAB site addresses. Had a look at these sites, think I
have a better idea of how this works. The cylinder head valve gear and
cylinders and combustion chambers as a single unit are hinged on one side
to the crankcase/crank. On the other side they are located by an eccentric
shaft. This allows the head to be moved closer or further from the
crankshaft. The rubber bellows only seals the oil space crankcase to the
head, and is not subject to combustion pressures. The information in the
text article of "4 degrees variation" does not give much information if the
relative positions and variations in the pivot points are not also given,
although the compression ratio variable of 8:1 to 14:1 can be used with the
cylinder dimensions given to find how much the head actually lifts from the
crankshaft, its too late for me to start to do this tonight. The pistons
will also be moving in cylinders whose centreline will also vary through an
angle of 4 degrees . Must have been a lot of research into minimising
piston slap.
1600cc, 225 BHP, fly by wire supercharger, variable compression. Hope
the engine management system is reliable...............Hmmmm. I'll stick
with my Plus 2 : )
Best wishes,
Sean Murray
From: ***@***.*** <***@***.***>
To: ***@***.*** <***@***.***>
Date: 24 March 2000 11:39
Subject: [LotusElan.net] Re: Compression ratio.
Hi P-O
Thanks for your SAAB site addresses. Had a look at these sites, think I
have a better idea of how this works. The cylinder head valve gear and
cylinders and combustion chambers as a single unit are hinged on one side
to the crankcase/crank. On the other side they are located by an eccentric
shaft. This allows the head to be moved closer or further from the
crankshaft. The rubber bellows only seals the oil space crankcase to the
head, and is not subject to combustion pressures. The information in the
text article of "4 degrees variation" does not give much information if the
relative positions and variations in the pivot points are not also given,
although the compression ratio variable of 8:1 to 14:1 can be used with the
cylinder dimensions given to find how much the head actually lifts from the
crankshaft, its too late for me to start to do this tonight. The pistons
will also be moving in cylinders whose centreline will also vary through an
angle of 4 degrees . Must have been a lot of research into minimising
piston slap.
1600cc, 225 BHP, fly by wire supercharger, variable compression. Hope
the engine management system is reliable...............Hmmmm. I'll stick
with my Plus 2 : )
Best wishes,
Sean Murray
-
Foxie - Coveted Fifth Gear
- Posts: 1634
- Joined: 20 Sep 2003
Post by: Rob_LaMoreaux » Mon Mar 27, 2000 4:36 pm
This weeks AutoWeek magazine has an article that is interesting reading
on the SAAB SVC.
Robert D. LaMoreaux
BT Electronics LLC
22700 Heslip Dr.
NoVI, MI 48375
Phone:(248)-449-8284
Fax:(248)-449-2577
Email:***@***.***
Alternate Email:***@***.***
on the SAAB SVC.
Robert D. LaMoreaux
BT Electronics LLC
22700 Heslip Dr.
NoVI, MI 48375
Phone:(248)-449-8284
Fax:(248)-449-2577
Email:***@***.***
Alternate Email:***@***.***
- Rob_LaMoreaux
- Fourth Gear
- Posts: 968
- Joined: 22 Sep 2003
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