Stroke

[pablo]

We're toying with the idea of changing the crank although the new crank would require some minor machining to fit. The question that I have is this the new crank has a slightly longer stroke what effect will this have.

Thanks Paul.

[blackskygtr]

I am sure i will be corrected if i am wrong but longer throw crank will give higher compression and increased capacity. Not so good for turbo motor unless you can bring compression down again with thicker gaskets and head work. long throw also reduces revs available hence small revvy units responding well to turbo work (short throw Less rotating mass to deal with)

Pinto lumps sufffered from blowing out head gaskets under standard compression with boost hence a lot of "wills rings" being used and the popularity of cross bolting on later units. I have to admit to not knowing if your engine was pinto or v6 so my apologies if this is all irrelevant. Dont know if that answers any questions but i know a little more about pinto lumps than i do skyline ones :oops:

[Gerry H]

The question that I have is this the new crank has a slightly longer stroke what effect will this have.

Thanks Paul.

Bent valves? Poor throttle response? Lower RPM limit?

[pablo]

Thanks guys very helpful and after 2 hours searching the net confirms what I was able to find
Jason our engine is the v6 cologne version


On stroke

The distance the axis of the crank throws from the axis of the crankshaft determines the piston stroke measurement, and thus engine displacement. A common way to increase the low-speed torque of an engine is to increase the stroke. This also increases the reciprocating vibration, however, limiting the high speed capability of the engine. In compensation, it improves the low speed operation of the engine, as the longer intake stroke through smaller valve's results in greater turbulence and mixing of the intake charge. For this reason, even such high speed production engines as current Honda engines are classified as "under square" or long-stroke, in that the stroke is longer than the diameter of the cylinder bore


And we had been lead to believe that this change of crank would be benefical to us......oh well you learn something new everyday :x :roll:

Another day wasted out of our tight schedule :roll:

[pablo]

The 2.9 crank is said to be a stronger crank than that of the 2.8 (our engine) and it has been stated that it can be fitted to the 2.8 block with some minor machining. Which is what we were planning to do.
If this conversion was carried out on a road car then the road car would feel better as it would improve low down torque. However reducing the rev limit and top speed would not be noticed on a road car but would be detrimental to the performance of a track based car.
I always wondered why the 2.8 had a rev limit of 6100 and the 2.9 5900 rpm now I know...it's due to the diffferences in the crank stroke.

90% of the information that we have on this engine would work perfectly well on a road based car but not on a track based turbo'd car. This is why I am asking a lot of questions at the moment I need to understand more about how things work on a general bases and not engine specific.

[gary@apt]

i run a stroked crank in my evo

running a longer stroke means you would need to run a stroker piston with pin higher up piston to bring compression back to some thing normal

unless this is a conversion thats been done before id leave it alone as the measuring and machining could cost way more than the gains

but its always funny to read things like strokers do rev,theres much more to it than that,mines revs over 8k with a rod ratio thats shocking on paper

[blackskygtr]

Me interested all of a sudden :-D
Gary what is the point of running a longer rod but then moving the piston pin upwards? surely that then defeats the object!!
Sorry if i am being a bit dim but this interests me.The rotating mass would be moved down effectively giving better rev range?
Teach me oh great one :oops:

[gary@apt]

its to do with rod to stroke ratio

my car std has a rod to stroke ratio of 1.7 once i did stroker its now 1.5 no one would want to go lower than that,it has much more sideways trust as crank spins over so wearing bores oval

mine had 150mm rod and 88mm stroke you divide rod by stroke to get ratio

now its same size rod with 100mm stroke

[gary@apt]

so if id used the same piston as std it would come 6mm further up bore and 6 mm further down.

so a stroker piston moves pin 6mm higher bringing the overhaul height back to same as std setup

[blackskygtr]

ok That makes sense I was then going to ask if there was a maximum you could use before the sideways movement becomes an issue but you answered that too LOL
Back on topic then I beleive one of the major things to do when dealing with V6 cologne is the inlet and exhaust ports. Early model colognes had siamesed ports seriously reducing the air flow. Swap of heads to later models with 3 ports per banks was the thing to do back in the day. Or cosworth heads from the 2.9 It was prob one of the worst designs ford ever came up with and highly restrictive. I would be focusing on this i think.
Fast Eddy will be a mine of info as he had around 3 years messing about with V6 in his crapri before binning it in favour of TVR V8 :twisted: :twisted:
There is also a company making a nice 3.5 ltr conversion for not silly money

http://www.cologneengines.com/ford%20co ... ersion.htm

Jay