Cossie stroker kits?
#81
Advanced PassionFord User
Edit: But I'll try, using a longer rod (with stock crank stroke, aka a higher rod ratio) lowers the mean average piston speeds (essentially they don't accelerate as quickly). This has 2 effects, the first being that there are less forces exerted on the rod bolts, rod's themselves, gudgeon pins and the area on the piston surrounding the gudgeon pin at XXXX rpm when comparing a longer rod to a standard length one meaning that you can safely rev the engine higher without one of those components breaking and sending the piston clattering into the exhaust valves/head on the exhaust stroke.
The second benefit/drawback is the effect it has on the combustion pressure. Due to the slower accelerating piston it spends more time near (not at) TDC, that means that you can use more ignition timing for the same revs/load whilst achieving peak combustion pressure at the correct crank angle for maximum torque for that specific engine (assuming it isn't already det limited), but the key word there is "can". On say a YB engine with standard cams, head and a T3 working it's guts out a longer rod can be a drawback as you could struggle to put any decent ignition timing in at peak torque (and other area's) which could not only result in less torque output but also higher EGT's. Obviously on a higher spec'd engine with a bigger turbo this can (that "can" word again), not be an issue as you'll have high cylinder pressures at higher rev's where not only the natural VE of the engine is lower but also the time available for detonation to occur is less.
Hope that explanation makes sense as I'm not a writer I'm sure other people will come in with their own opinion of longer rod's and there effect too
Last edited by SiZT; 19-07-2013 at 02:24 PM.
#82
PassionFord Regular
Funny you should say that, Mark is close to me and I have rang him regarding a set up once the new clutch & hydraulic pedal are fitted, oh and the wasted spark is working
But I'll be wanting to pick his brains of what he can offer for future build, I like to know the nuts and bolts of it all, interested in how these guys are making it work
But I'll be wanting to pick his brains of what he can offer for future build, I like to know the nuts and bolts of it all, interested in how these guys are making it work
#83
PassionFord Regular
8.5 compression ratio -2.8 bar of Boost & 8.8k limit on revs. 838bhp/666ft-lb. This suggests your advice is incorrect as my MAD engine seems to work rather well. The new engine will be better as 5 more years of development will go into it. However this level of engine is very expensive & its always a case of How fast can you afford to go.
Your build has been epic, I am looking forward to seeing the next instalment
I can afford to go fast....., just not as fast as you
#84
PassionFord Regular
This was on pump fuel, the faster times we aimed for we're going to be on race fuel.
Compression ratio was no lower that 8.0:1..
We personally range from 7.7-11.5:cr it completely depends on what the engine is for and spec.
Big engines we don't go below standard cr, as mark says turbos manifolds and cams make a huge difference on what cr you can run it's all a juggling game at the end of the day, it's easy to just put an engine together and it work but to get a really well working complete package takes development. Hence the use of a bench dyno IMO is essential.
My own engine spent a week on the dyno playing with cams and I could vary torque from 450 to 490lbft of torque just with timing
I settled at 470lbft and 552bhp as 2wd I didn't want too aggresive and wanted a wide power band
I was keeping it very basic as I didn't want to make an article about it. But as its very interesting understanding piston speeds and dwell etc and their effects go ahead
Compression ratio was no lower that 8.0:1..
We personally range from 7.7-11.5:cr it completely depends on what the engine is for and spec.
Big engines we don't go below standard cr, as mark says turbos manifolds and cams make a huge difference on what cr you can run it's all a juggling game at the end of the day, it's easy to just put an engine together and it work but to get a really well working complete package takes development. Hence the use of a bench dyno IMO is essential.
My own engine spent a week on the dyno playing with cams and I could vary torque from 450 to 490lbft of torque just with timing
I settled at 470lbft and 552bhp as 2wd I didn't want too aggresive and wanted a wide power band
I was keeping it very basic as I didn't want to make an article about it. But as its very interesting understanding piston speeds and dwell etc and their effects go ahead
I have read a bit in to timing and overlap, I saw your car, very nice, some very nice touches
#85
PassionFord Regular
The problem is how much do you write without people thinking it's some kind of magic power maker and start trying to stuff the longest rods they can in T3 and T34 engines on standard cams
Edit: But I'll try, using a longer rod (with stock crank stroke, aka a higher rod ratio) lowers the mean average piston speeds (essentially they don't accelerate as quickly). This has 2 effects, the first being that there are less forces exerted on the rod bolts, rod's themselves, gudgeon pins and the area on the piston surrounding the gudgeon pin at XXXX rpm when comparing a longer rod to a standard length one meaning that you can safely rev the engine higher without one of those components breaking and sending the piston clattering into the exhaust valves/head on the exhaust stroke.
The second benefit/drawback is the effect it has on the combustion pressure. Due to the slower accelerating piston it spends more time near (not at) TDC, that means that you can use more ignition timing for the same revs/load whilst achieving peak combustion pressure at the correct crank angle for maximum torque for that specific engine (assuming it isn't already det limited), but the key word there is "can". On say a YB engine with standard cams, head and a T3 working it's guts out a longer rod can be a drawback as you could struggle to put any decent ignition timing in at peak torque (and other area's) which could not only result in less torque output but also higher EGT's. Obviously on a higher spec'd engine with a bigger turbo this can (that "can" word again), not be an issue as you'll have high cylinder pressures at higher rev's where not only the natural VE of the engine is lower but also the time available for detonation to occur is less.
Hope that explanation makes sense as I'm not a writer I'm sure other people will come in with their own opinion of longer rod's and there effect too
Edit: But I'll try, using a longer rod (with stock crank stroke, aka a higher rod ratio) lowers the mean average piston speeds (essentially they don't accelerate as quickly). This has 2 effects, the first being that there are less forces exerted on the rod bolts, rod's themselves, gudgeon pins and the area on the piston surrounding the gudgeon pin at XXXX rpm when comparing a longer rod to a standard length one meaning that you can safely rev the engine higher without one of those components breaking and sending the piston clattering into the exhaust valves/head on the exhaust stroke.
The second benefit/drawback is the effect it has on the combustion pressure. Due to the slower accelerating piston it spends more time near (not at) TDC, that means that you can use more ignition timing for the same revs/load whilst achieving peak combustion pressure at the correct crank angle for maximum torque for that specific engine (assuming it isn't already det limited), but the key word there is "can". On say a YB engine with standard cams, head and a T3 working it's guts out a longer rod can be a drawback as you could struggle to put any decent ignition timing in at peak torque (and other area's) which could not only result in less torque output but also higher EGT's. Obviously on a higher spec'd engine with a bigger turbo this can (that "can" word again), not be an issue as you'll have high cylinder pressures at higher rev's where not only the natural VE of the engine is lower but also the time available for detonation to occur is less.
Hope that explanation makes sense as I'm not a writer I'm sure other people will come in with their own opinion of longer rod's and there effect too
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