johncarman
|
| posted on 18/3/04 at 10:15 AM |
|
|
CVH 1.6 head on 1.8
My donor car is a Sierra with the 1.8 CVH engine. I believe the head on this engine is not really suited to tuning for power, so i was wondering if
it is possible to fit the head from the 1.6 CVH. Has anyone done this, or can anyone give any advice.
|
|
|
|
|
ChrisW
|
| posted on 18/3/04 at 10:20 AM |
|
|
I've done it, and the head fits, but I'm told my compression ratio will now be a bit low to get much power and only really suitable if I
run a turbo. This is all speculation tho - the only thing I can confirm is that the head physically fits and as I'm not using that engine any
more I doubt I'll ever find out!
Chris
My gaff my rules
|
|
|
Ben_Copeland
|
| posted on 18/3/04 at 11:35 AM |
|
|
That sounds about right, lowers compression. So ideal for turbo, but not much else
Ben
Locost Map on Google Maps
Z20LET Astra Turbo, into a Haynes
Roadster
Enter Your Details Here
http://www.facebook.com/EquinoxProducts for all your bodywork needs!
|
|
|
Surrey Dave
|
| posted on 18/3/04 at 12:27 PM |
|
|
I run this engine ,and it ain't all bad.
I swapped the Peirburg carb for a Weber DGV.
But you can use the 1600 head plus all the available tuning parts , if you change the pistons and maybe the rods.
Mike Tanski at Ferriday Engineering can help with parts and engineering.
|
|
|
britishtrident
|
| posted on 18/3/04 at 12:59 PM |
|
|
The best info on the CVH is at http://www.pumaracing.co.uk/cvh.htm run by Dave Baker
Dave is a good guy who hangs around the usenet uk.rec.cars.kit-car news group and gives words of wisdom that are spot on 99.999 % of the
time..
On Dave's site you will find info on all the fwd CVH heads.
The one to go if you plan on sticking with carbs (or use throttle bodies) is the head with the number 88SM6090 cast on to the top of the head near
the front between the inlet manifold and the rocker cover -- These are easier to find than Dave's site sugests I got mine off an 89 Orion
with Weber carb.
The early non injection head is also pretty good but the valve seats aren't officially OK for unleaded but are apparently OK -- look for
81SM6090 cast in the same place..
One big advantage of the head from an XR Carb model is it has a conventional distributer ignition system -- but beware are the distributers are
prone to problems with advance mech.
|
|
|
johncarman
|
| posted on 18/3/04 at 03:43 PM |
|
|
Thanks for the reply's. Can somebody please give me a bit of a technical description of what "Lower Compression Ratio" actually
means, and why this is suited to turbo charging. Cheers.
|
|
|
britishtrident
|
| posted on 18/3/04 at 05:02 PM |
|
|
The compression ratio is a measure of how much the engine squeezes the fuel air mixture before ignition -- the definition is
(swept volume+combustion chamber volume)/ combustion chamber volume
Higher compression ratios give more power but can lead to pre-ignition and knock which can destroy an engine. Early engines used very low compression
ratios because of the poor quality fuels available. After WW1 lead additives were put in fuel improving the ressistance to pre-ignition and knock.
The knock ressistance (octane rating) of fuels increased again at the end of WW2 reaching peak with 5 star fuels in the 1960s.
Turbo engines because the air is pre-compressed (and therefore also heated) before the compression process starts are more prone to knock than
non-supercharged engines, and when they do knock it tends to be more destructive.
Higher compression is a double edge sword the higher the compression ratio the more efficient the expansion stroke, but also more work is lost
compressing the charge and more mechanical and thermal stress is put on the engines components. Also the law of dimishing returns applies -- more
power is gained increasing the compression ratio from 7.5:1 to 8:1 than from 8:1 to 9:1. As a result most road engines have compression ratio below
9.5:1 with turbo engines usually running between 7.5:1 and 8.2:1.
Also engines with large cylinders generally have lower compresion ratios than small bore engines.
|
|
|
Fatboy Dave
|
| posted on 18/3/04 at 07:36 PM |
|
|
Chris, it's not speculation, I've had an engine running for some time in this condition (well, with a turbo on the side anyway  ).
BritishTrident, surely you mean above 9.5? I haven't met a whole load of modern engines lower than 9.5, unless they were
'modernised' older design engines (the 1360cc TU engine in the Shitroen Shatso being an example). These are usually also 8v sh*tters too,
usually found in shoppers, where any semblance of performance is merely hinted at by the bijout metallic paint and plastic wheel trims.
Dave
Stop the planet, I want to get off
|
PLEASE NOTE: This user is a trader who has not signed up for the LocostBuilders registration scheme. If this post is advertising a commercial product or service, please report it by clicking here.
|
johncarman
|
| posted on 18/3/04 at 08:01 PM |
|
|
Dave, Can you give me any more details of your engine ?? What Turbo are you running, do i need to make any modifications to the engine, such as new
pistons, rods etc.
|
|
|
britishtrident
|
| posted on 18/3/04 at 08:19 PM |
|
|
No 9.5:1 on stock engines except on smaller engines below about 400 cc per cylinder and with a good combustion chamber design it can creep up to about
9.7:1 or even 10:1 engines with a knock detector can go a bit higher say 10.5:1 but the gains just aren't worth the effort.
Looking for power by increasing the compression is nothing new back in the 60s quite a few new cars were sold with 10:1 or even 10.5:1 compression
but since then fuel knock ressistance has fallen, don't be fooled by quoted octane numbers.
With cast iron heads very few stock engines go above 9.2:1.
The big disadvantage in raising compresson ratio is that more extra heat energy is dumped into the cooling system and exhaust gases than is
liberated as extra power.
The typical gain in going from an 8.5:1 to a 9.5:1 compression ratio is about 3.5 hp per 1000cc, the gain from going from 9.5:1 to 10.5:1 falls to
about 2 bhp.
The camshaft used also has a big effect --- cams with a big overlap need a higher compresion to work properly.
The waste heat problem is made worse if the ignition has to be retarded to stop pinking, the more retarded the spark the more heat is dumped to the
cooling water and exhaust at the end of the expansion stroke.
[Edited on 18/3/04 by britishtrident]
|
|
|
Fatboy Dave
|
| posted on 18/3/04 at 08:23 PM |
|
|
John,
I'm on my fourth now 
I normally haul 'em straight out the cars when I break a Sierra. Pistons I always leave standard, as I never run much boost (way I figure it,
it's a sh*tter of an engine, and if I was to spen much money, I'd do a Zetec instead).
Gaskets have always been standard 1.8CVH, which so far, has been the failure point on two of them (one melted a piston when the fuel pump failed on
boost, and two head gaskets).
Turbo wise, I'm using an Escort RS Turbo manifold, but the flow is poor, so I took to making new ones with 14" tubular equal length
primaries (purely to have a fiddle. Nothing wrong with an RST manifold on a standard bottom end of a 1.8). Units themselves are again, standard Ford
fare. T3 in (I think) .48 trim. Wanted to try a T2 from a Fiesta to cut down on the lag (not that there is a lot of it anyway), but the children on
eBay pay silly money for the manifolds. That's not what any of my projects are about...
Inlet manifold on the first engine was an RST one, as I had used an XR3i hemi head, so I had to have the injector plate machined to accept electronic
injectors (all MFI cars have different shaped ports to the EFI cars, which either means an MFI manifold, or an adaptor plate to fit an EFI manifold.
You could always search out an XR2i head, or a '90 spec 1.6i engine).
Second engine onwards are using EFI manifolds and heads, and fueling is being taken care of by Megasquirt (tried using a metering head and mechanical
injection, but it wasn't a massice success, and th cost of a chip to sort out the extra engine size ruled it uneconomical).
Hope that helps, I think it covers everything...
Dave
Stop the planet, I want to get off
|
PLEASE NOTE: This user is a trader who has not signed up for the LocostBuilders registration scheme. If this post is advertising a commercial product or service, please report it by clicking here.
|
Fatboy Dave
|
| posted on 18/3/04 at 08:36 PM |
|
|
Agree with the principals, and the maths work out, but the logic is flawed. You need to provide the fact that most modern cars (at least ones I know
of) that are using 95RON fuel have a compression higher than 9.5:1. The fact is, the Zetec engine has a 10.4:1 compression ratio, has a knock sensor,
and has no hassles with the fact. The XE, again, has a similar configuration.
Even the humble Ford Endura 'crossflow', en engine old enough to be my dad, still keeps its compression at 9.5:1, and I doubt you get an
engine smaller (certainly under the 400cc per chamber you quote), or more basic that that? The fact is, just a quick look at Google, for some random
engines, that shows that in this day and age, the only engine using <9.5:1 is turbocharged. Even the humble TU 1360 Peugeot engine (I picked on
this as its herritage comes from the Talbot Samba, as I gently rib some of my Saxo/106 owning colleagues with), has 10.2, and that's a 2v OHC
deisgn (ali. head, iron blocked IIRC).
I should also point out, that the major reason behind this is mainly a case of efficiency. High compression = decent performance, and clean running
(to an extent. We have emissions systems for these particular caveats).
[Edited on 18/3/04 by Fatboy Dave]
Dave
Stop the planet, I want to get off
|
PLEASE NOTE: This user is a trader who has not signed up for the LocostBuilders registration scheme. If this post is advertising a commercial product or service, please report it by clicking here.
|
britishtrident
|
| posted on 18/3/04 at 09:05 PM |
|
|
Not only the Zetec but even the old Rover M16 but we are talking CVH not Zetec, the hassle of trying to put a knock detector on an engine that
hasn't got one isn't worth it as the knock detection circuitry and sensor has to be match exactly to the power unit it isn't
just a bolt on goodie.
Interstingly Rover having used a knock detector on the M16 and T16 and although they have a connection available on the ECU for a knock sensor went
to running without one on the K series dropping the compression ratio back in the process.
[Edited on 18/3/04 by britishtrident]
|
|
|
Mark Allanson
|
| posted on 18/3/04 at 09:15 PM |
|
|
My old favorite party trick, rattle a spanner on the rocker cover of a 1.6 montego (if you can find one), and if you get the frequency right, you can
stall the engine!
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
|
|
|
Fatboy Dave
|
| posted on 18/3/04 at 10:38 PM |
|
|
quote:
Not only the Zetec but even the old Rover M16 but we are talking CVH not Zetec, the hassle of trying to put a knock detector on an engine that
hasn't got one isn't worth it as the knock detection circuitry and sensor has to be match exactly to the power unit it isn't
just a bolt on goodie
Indeed!
But!
At the risk of being argumentative, and as such, this will be my final post on the subject, that wasn't the point being made...
It goes without saying, that modern EFI is equipped to handle pinking, and as such 99 times out of 100, has a knock sensor.
If you want to limit this to the CVH, and not the broad statement made above, then 9.5 is *fine* for a CVH. They don't make big power anyway,
unless you throw a lot of money and affort at them for deminishing returns, and as such, trying to push a 25 year old design to modern standards, is,
as you say, like chalk and cheese to the Zetec.
Now, let's all go to the pub and have a drink
Dave
Stop the planet, I want to get off
|
PLEASE NOTE: This user is a trader who has not signed up for the LocostBuilders registration scheme. If this post is advertising a commercial product or service, please report it by clicking here.
|
soggy
|
| posted on 19/3/04 at 06:59 PM |
|
|
cvh
my avon is fitted with a 1.8cvh fitted with a 1.6 head the pistons have been replaced with zetec ones and compression is 10.1 the work was carried out
by ferriday engineering 01785 621710 stafford. The car was brought as an unfinished project i didnt have the work done to the engine all i did was
bolt it in, for the money it cost turbo option sounds good to me might try it my self when its on the road i still have fond memories of my series 2
turbo.
if at first u dont succeed use a bigger hammer!
|
|
|
