Stupid question time...Strokers?
Discussion
rickf_uk said:
I know I'm going to regret this but, tell me more? Remember to speak slowly. To start with what are the pros and cons of the stroker?
Cubic capacity gives you more torque, so the bigger the better. Ringram has the biggest on here at 440cubic inches...so he tells me! One way to gain extra cubes is to install a stroked crank which increases the volume of each cylinder with the extra throw. You might do it by increasing the bore only, but it's not then a real "Stroker". Strokers have increased piston speeds which wear more. Over square engines (bigger bore than stroke) tend to be revvier/racier.Although if you have one of those compressor thingys, they effectively make an engine bigger by squeezing more fuel in. That's called forced induction (FI) i.e Turbochargers or superchargers (commonly called blowers)
You can do the same thing by using Nitrous. This is where you inject more fuel and nitrous oxide(the oxidising agent)together for a bigger fuel charge.
As you will see on here the camps are divided into (tribes really) each with his/her perception of which is the best way to annexe more power. BTW its all very well having all that power, but you then need to get it down, safely and a lot of folk ignore that.
I'm sure this is going to become quite an interesting thread, when the others arrive. Cheers Mate.
Edited by MyM8V8 on Tuesday 11th August 23:50
Shortblock Myth #1 - My piston speed will be too much if I build this engine!
Gotta start somewhere while doing the stickies so I picked this one although in the last year or two these types of questions have dropped off somewhat.
I used to get a call or two a week asking or worrying about "excessive piston speed" and still do every once in a while but less so as time goes on and we see more and more larger stroke deals out there like the LS7 or the 5.4 Mod Motor etc.
People typically are somewhat worried about this having some sort of effect on their power or engine life. They are often informed on the net about the evils of "too much piston speed" and not being able to turn the rpm they want to etc.
I'd like to hear peoples questions and discuss this but I will lay down some truths ahead of time and more as this goes on.
- Engine speed is generally capped by the hydraulic roller valvetrain and the intake manifolds on 95 percent of the LSx engines seen in any of these discussions anywhere on the net.
- When you increase piston speed you increase airflow through the ports as that is why air enters the ports in the first place. If the engine does not turn and the pistons do not move then the ports do not move any air.
- Past a certain rpm and stroke the heads start to go turbulent and get choked and the engine starts to lose power even with perfect valvetrain. Anotherwords all engines will peak and then lose power.
- When you increase engine stroke you lower the rpm at which the engine will peak and lose power. This can allow you the use of larger better heads without turning more rpm which as we said is capped by other factors in most LSx hydraulic roller engines (some high and some lower).
- The rotating and recipricating loads that destroy your parts over time are directly related to the stroke and to the SQUARE of the RPM.
- This means that if I double my stroke I will have double the loads on my parts at the same RPM but of course like we said RPM at the equivalent power or peak power will be reduced by approximately 1/2 as well in general. The loss in RPM will drop the same loads by a factor a 4 so that now at the same piston speed but half the RPM with double the stroke I will see only half the force on my parts like pistons and rods and rod bolts and crank etc.
- Anotherwords "piston speed" can not determine bottom end reliability much at all but rather RPM is a much better sign of stress as RPM is squared in these rpm related load equations. I can have one engine that lasts 1,000,000 miles at 4000 FPM mean piston speed or another that only lasts 1 mile. One might turn 2200 RPM with a big stroke and one might turn 22,000 RPM with a very short stroke even though they both average the same piston speed.
- If you have an ARP catalogue you can look in it and Carroll Smith and Kenneth Foster have it all lined out there about rod bolt loads in the earlier pages etc. as to what causes load on the rods.
- I am not discounting rod and piston MASS which is also a large factor so less weight is also always good as long as the parts are also still strong.
______________
Erik Koenig
SamRacing.com
Gotta start somewhere while doing the stickies so I picked this one although in the last year or two these types of questions have dropped off somewhat.
I used to get a call or two a week asking or worrying about "excessive piston speed" and still do every once in a while but less so as time goes on and we see more and more larger stroke deals out there like the LS7 or the 5.4 Mod Motor etc.
People typically are somewhat worried about this having some sort of effect on their power or engine life. They are often informed on the net about the evils of "too much piston speed" and not being able to turn the rpm they want to etc.
I'd like to hear peoples questions and discuss this but I will lay down some truths ahead of time and more as this goes on.
- Engine speed is generally capped by the hydraulic roller valvetrain and the intake manifolds on 95 percent of the LSx engines seen in any of these discussions anywhere on the net.
- When you increase piston speed you increase airflow through the ports as that is why air enters the ports in the first place. If the engine does not turn and the pistons do not move then the ports do not move any air.
- Past a certain rpm and stroke the heads start to go turbulent and get choked and the engine starts to lose power even with perfect valvetrain. Anotherwords all engines will peak and then lose power.
- When you increase engine stroke you lower the rpm at which the engine will peak and lose power. This can allow you the use of larger better heads without turning more rpm which as we said is capped by other factors in most LSx hydraulic roller engines (some high and some lower).
- The rotating and recipricating loads that destroy your parts over time are directly related to the stroke and to the SQUARE of the RPM.
- This means that if I double my stroke I will have double the loads on my parts at the same RPM but of course like we said RPM at the equivalent power or peak power will be reduced by approximately 1/2 as well in general. The loss in RPM will drop the same loads by a factor a 4 so that now at the same piston speed but half the RPM with double the stroke I will see only half the force on my parts like pistons and rods and rod bolts and crank etc.
- Anotherwords "piston speed" can not determine bottom end reliability much at all but rather RPM is a much better sign of stress as RPM is squared in these rpm related load equations. I can have one engine that lasts 1,000,000 miles at 4000 FPM mean piston speed or another that only lasts 1 mile. One might turn 2200 RPM with a big stroke and one might turn 22,000 RPM with a very short stroke even though they both average the same piston speed.
- If you have an ARP catalogue you can look in it and Carroll Smith and Kenneth Foster have it all lined out there about rod bolt loads in the earlier pages etc. as to what causes load on the rods.
- I am not discounting rod and piston MASS which is also a large factor so less weight is also always good as long as the parts are also still strong.
______________
Erik Koenig
SamRacing.com
rickf_uk said:
I know I'm going to regret this but, tell me more? Remember to speak slowly. To start with what are the pros and cons of the stroker?
Theres no replacement for displacement 
stroker is the most effective way to increase displacement. you can bore the piston wall only by about .015 inches on most ls blocks safely. so an ls2 would go from 4" to 4.03". stroke can be increased by almost .5 inches.
more room to go up and down instead of side to side. stroking the engine tends to add more torque then horsepower too.
not to mention saying "I have a stroker" just sounds cool
TomHGTO said:
rickf_uk said:
I know I'm going to regret this but, tell me more? Remember to speak slowly. To start with what are the pros and cons of the stroker?
Theres no replacement for displacement
stroker is the most effective way to increase displacement. you can bore the piston wall only by about .015 inches on most ls blocks safely. so an ls2 would go from 4" to 4.03". stroke can be increased by almost .5 inches.
more room to go up and down instead of side to side. stroking the engine tends to add more torque then horsepower too.
not to mention saying "I have a stroker" just sounds cool
same as theres no substitute for cubic inches
TomHGTO said:
rickf_uk said:
I know I'm going to regret this but, tell me more? Remember to speak slowly. To start with what are the pros and cons of the stroker?
Theres no replacement for displacement stroker is the most effective way to increase displacement. you can bore the piston wall only by about .015 inches on most ls blocks safely. so an ls2 would go from 4" to 4.03". stroke can be increased by almost .5 inches.
more room to go up and down instead of side to side. stroking the engine tends to add more torque then horsepower too.
not to mention saying "I have a stroker" just sounds cool
Older LS1/6 blocks have 0.005", the liners are wafer thin.
stevieturbo said:
LS2 liners have plenty of meat in them for boring...far beyond the 0.015" you mention
Older LS1/6 blocks have 0.005", the liners are wafer thin.
safely Older LS1/6 blocks have 0.005", the liners are wafer thin.
I know ls2s running at 4.06 but its not recommended. some have run it for years, others weeks. deffinatly not over 4.03 for FI.
I couldn't get a shop to bore out an LS2 block over .03 when I had my motor built. I called a lot of shops too, all over the country =/
Edited by TomHGTO on Wednesday 12th August 01:24
Consider the following.
S600VXR has a 6L LS2 it put down in ideal conditions (Middle of winter) 505rwhp
Jez's car built to the same spec only managed 450rwhp at the dyno day we all went to which represents a more realistic output.
Boost pressure on the above is IIRC 12psi which is in excess of 180% of atmospheric.
Standard LS2 with average tuneup does 320rwhp so the blower should based on the pressure yield around 580rwhp!
Yet best case is only gives 60% more power, and more normally a feeble 40% more. The other 40% of fuel burnt is simply wasted in paracyitic losses and thermal inefficiency. Sure more rear wheel is produced by fitting a blower, but its hardly an efficient way of generating it.
By contrast a stroker of 7.2L represents only a 20% increase over stock displacement, yet power is a much more consistent 160% of stock. (mine put down 502rwhp in the middle of summer at SRR)
Efficiency gains are from better voumetric efficiency, camshaft and head design.
At idle the stroker will use 20% more fuel than stock (Maybe a tad more depending on cam) so will lose to the PD Blower at idle which still only moves stock airflow.
Also consider that the power that doesnt end up at the rear with the PD blower is still felt to some extent by the engine due to inefficient heat losses and load on the crank which is spent in trying to jam air where it doesnt want to go and its no surprise the stock engines only last a short period of time with a blower.
The load on a stroker is close to, or the same as stock. But efficiency is greater at almost all levels. Sure you burn more fuel, but you also make more power. None of the extra is wasted as it is with the blower.
Now if you combine both technologies you will have something better than the sum of the 2 parts, because the engine is designed for boost. Cam timing, heads, structure etc are all optimised. Gross power will be something mental.
So as Ive said before if you are looking at fitting at blower to a stock engine, then you need to either keep boost low so as not to blow things up and reduce engine life, or perhaps dont even bother at all. A simple $350 US cam will give you 400rwhp in a consistent manner. Over that consider that a stroker will take you to over 500rwhp with excellent reliability. North of that you will want do both things.
HarryOz, Jez, Wormus, Munkey have done both and have the best gross power. But ask them how many pounds per BHP they spent. Id guess its at least 2-300% more than I spent on the stroker.
My 2p. Abuse invited.
S600VXR has a 6L LS2 it put down in ideal conditions (Middle of winter) 505rwhp
Jez's car built to the same spec only managed 450rwhp at the dyno day we all went to which represents a more realistic output.
Boost pressure on the above is IIRC 12psi which is in excess of 180% of atmospheric.
Standard LS2 with average tuneup does 320rwhp so the blower should based on the pressure yield around 580rwhp!
Yet best case is only gives 60% more power, and more normally a feeble 40% more. The other 40% of fuel burnt is simply wasted in paracyitic losses and thermal inefficiency. Sure more rear wheel is produced by fitting a blower, but its hardly an efficient way of generating it.
By contrast a stroker of 7.2L represents only a 20% increase over stock displacement, yet power is a much more consistent 160% of stock. (mine put down 502rwhp in the middle of summer at SRR)
Efficiency gains are from better voumetric efficiency, camshaft and head design.
At idle the stroker will use 20% more fuel than stock (Maybe a tad more depending on cam) so will lose to the PD Blower at idle which still only moves stock airflow.
Also consider that the power that doesnt end up at the rear with the PD blower is still felt to some extent by the engine due to inefficient heat losses and load on the crank which is spent in trying to jam air where it doesnt want to go and its no surprise the stock engines only last a short period of time with a blower.
The load on a stroker is close to, or the same as stock. But efficiency is greater at almost all levels. Sure you burn more fuel, but you also make more power. None of the extra is wasted as it is with the blower.
Now if you combine both technologies you will have something better than the sum of the 2 parts, because the engine is designed for boost. Cam timing, heads, structure etc are all optimised. Gross power will be something mental.
So as Ive said before if you are looking at fitting at blower to a stock engine, then you need to either keep boost low so as not to blow things up and reduce engine life, or perhaps dont even bother at all. A simple $350 US cam will give you 400rwhp in a consistent manner. Over that consider that a stroker will take you to over 500rwhp with excellent reliability. North of that you will want do both things.
HarryOz, Jez, Wormus, Munkey have done both and have the best gross power. But ask them how many pounds per BHP they spent. Id guess its at least 2-300% more than I spent on the stroker.
My 2p. Abuse invited.
MyM8V8 said:
Mate, he wanted it keeping simple. Horses for courses. What do you think the stroke is on an F1 engine.
Exactly, sweet FA. But look at their RPM and the cost to keep it together.I think the idea is that stroke in itself is not bad, RPM is. However a large stroke will make everything work better meaning you dont need as much RPM. Just gear it right
(ie) Long stroke high rpm = Bad. Long stroke slightly reduced rpm = good
Loading is arithmetially proportional to stroke but geometrically proportional to RPM
To be fair...4.0" is a long stroke, I wouldnt consider going any further.
Similarly with bores on these engines. I'd use a little over 4.0", but not much. I dont see any gains worth having over a 402/3 for the possible reliability problems with a bit of boost due to thinner liners.
n/a no problem, but not with boost. And the larger engines already make enough torque that traction can be a problem, without doing much more to increase torque lower in the rpm range.
No sense having lots of claimed power, if ultimately your car cant go any faster because you cant make use of it.
For a daily driver, reliability etc...Richards approach is a very good one. Although in the short term, more expensive. But you could opt for a larger n/a build initially with a safe CR, quality pistons etc.
And then if you did get bored, what an ideal time to add that blower. WOuld probably more cost effective in the long run to do it that way.
Some here have bolted blowers to std engines, then wanted more. This then required a new engine, and a new blower. So far more expensive. Had they went the forged upraded route first with a n/a unit, and then chosen a blower to suit....they probably would ahve saved a bomb.
Or they may have been happy with the n/a lump and just leave it there.
Similarly with bores on these engines. I'd use a little over 4.0", but not much. I dont see any gains worth having over a 402/3 for the possible reliability problems with a bit of boost due to thinner liners.
n/a no problem, but not with boost. And the larger engines already make enough torque that traction can be a problem, without doing much more to increase torque lower in the rpm range.
No sense having lots of claimed power, if ultimately your car cant go any faster because you cant make use of it.
For a daily driver, reliability etc...Richards approach is a very good one. Although in the short term, more expensive. But you could opt for a larger n/a build initially with a safe CR, quality pistons etc.
And then if you did get bored, what an ideal time to add that blower. WOuld probably more cost effective in the long run to do it that way.
Some here have bolted blowers to std engines, then wanted more. This then required a new engine, and a new blower. So far more expensive. Had they went the forged upraded route first with a n/a unit, and then chosen a blower to suit....they probably would ahve saved a bomb.
Or they may have been happy with the n/a lump and just leave it there.
Those with LS3's are very lucky to have an excellent engine to work from. The LS3 heads were originally developed by GM for the LS7 project with a target 500bhp.
All the gains are mainly from the heads.
Sure add a blower and you will have more power than an LS2, but the same comments and limitations apply. Its just the head is more efficient.
A cam only LS3 will easily give over 450rwhp IMO.
All the gains are mainly from the heads.
Sure add a blower and you will have more power than an LS2, but the same comments and limitations apply. Its just the head is more efficient.
A cam only LS3 will easily give over 450rwhp IMO.
stevieturbo said:
To be fair...4.0" is a long stroke, I wouldnt consider going any further.
Similarly with bores on these engines. I'd use a little over 4.0", but not much. I dont see any gains worth having over a 402/3 for the possible reliability problems with a bit of boost due to thinner liners.
Bore accepted. But surely the limitation of stroke is mainly due to insufficient piston support due to the short bores in stock form.Similarly with bores on these engines. I'd use a little over 4.0", but not much. I dont see any gains worth having over a 402/3 for the possible reliability problems with a bit of boost due to thinner liners.
With blocks like the RHS, the LS7 and Darton sleeves supporting a much longer stroke this issue can be avoided. Afterall the RHS block was specifically designed to support a 4.5" stroke!
On a stock engine I would tend to agree based on others experiences. 4" is a sensible maximum. Though the LS7 has much longer bores so a 4.1 or even 4.125 is probably ok in them.
ringram said:
Those with LS3's are very lucky to have an excellent engine to work from. The LS3 heads were originally developed by GM for the LS7 project with a target 500bhp.
All the gains are mainly from the heads.
Sure add a blower and you will have more power than an LS2, but the same comments and limitations apply. Its just the head is more efficient.
A cam only LS3 will easily give over 450rwhp IMO.
And yet a friend in Australia reliably informs me that he has just had a stock cammed LS2 VZ Maloo with a good (mafless) tune make 292 rwkw (392HP) as against a similar tuned LS3 in a VE made 280rwkw odd. So the 243 heads can't be that bad against the L92's -(flow numbers accepted).?All the gains are mainly from the heads.
Sure add a blower and you will have more power than an LS2, but the same comments and limitations apply. Its just the head is more efficient.
A cam only LS3 will easily give over 450rwhp IMO.
My OTR should be on its way!!!
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