2.6 Stroker??

[c_riggan]

Still cant post in the tech forums....?? ANyway..

Has anybody done the 2.6 stroker from Brian Crower? Uses a 4g64 Block with a 63 head and a 7 bolt crank... BC says it can be a 2.6 with 87.5mm bire and a 106mm crank.

Just wondering if anybody has done it, and how good it really is. Sounds interesting.

The kit is located here: EXTREME PSI : Your #1 Source for In Stock Performance Parts - Brian Crower Mitsubishi 4G64 Block w/4G63 Head 2.6L Stroker Kit

 

[MidShipCivic]

You point is?


Supra's do 3.4L stroker kits all day 1.41 rod to stroke ratio.
SRT-4's all day stock 1.49 rod to stroke ratios.

Honda's have ratios in the 1.5 range.

Although there is more rod angle this doesn't determine the life of your motor.

Breathing has changed and vacuum pull on the ports occur at different crankshaft degrees, so you must tailor your head cam shafts and intake manifold to suit it.


Learn how to build a motor ? And nothing will happen.

 

[DSMTriad]

That makes sense to me. I always thought that stroking to the blocks limit meant less streetability. I also thought that it wasn't really necessary to stroke a turbo engine due to the forced induction.

 

[DSMTriad]

Displacement spools turbos faster and when are you ever over 7K rpm street driving? Therefor the best street engine configuration would have to be the 2.6L. If only they made four cylinder engines with huge, 4"+, bores.

Ah ok I understand now. I had to think about it for a second. I think I might get me a 4G64 block.

 

[z24frank]

the starion has 92mm pistons and its also a 2.6 so just throw that in there!

 

[MidShipCivic]

Displacement spools turbos faster and when are you ever over 7K rpm street driving? Therefor the best street engine configuration would have to be the 2.6L. If only they made four cylinder engines with huge, 4"+, bores.

Don't forget that stroke gives a direct response in spool as well.

the starion has 92mm pistons and its also a 2.6 so just throw that in there!

Yeah true, but are the stroke and rod length remotely close to this combo ? I don't think so.

 

[KeelesKustome]

so basically ... with a stroker motor.. it would induce more air at a shorter rpm... causing a turbo to spool up much faster as that air is exiting at a much lower rpm...
Would this mean you would need a much larger turbo to compinsate for the stroker?

 

[stratt134]

Just think about motors in general.

<b>All daily drivers want MORE torque. Stroker motors make more torque, and spool turbos faster</b>
... more torque... turning force.. = faster/easier revs = quicker/stronger turbo spool. Think of a stroker motor like this, when you have a stuck bolt and use a wrench, and you use a "cheater bar", know how easy it is to break the bolt loose? You had more leverage/force on the bolt. Same with a stroker motor, the rods journals on the crank are "farther apart" hence more force.

On a Chevy 350ci motor, you can stroke it to 383, using a 400ci crank. I have one in a 69 Nova... tons of torque, but it boils the tires down easily... For TRACK TURBO setups, most people take the 400ci block and "de-stroke" it with a 350ci crank, to 377ci... that creates less torque, but spins higher RPMs... AND keeps the block walls as thick/STRONG as stock...


So... stroker motors can AND can not be daily drivers. Obviously, when you stroke a motor, you can only go so far. This 2.6L kit is pretty maxed out, which equals a lot THINNER cylinder walls. I wouldn't go higher than a 2.4L daily driver... for the only reason of the thickness of the cyl walls.
Also, when talking about higher compression ratios, YES, it can be more "efficient" when tuned correctly... BUT for a daily driver, you try to stay in vacuum most of the time, not boost, so your NA compression ration is what you spend most of your driving time in!!! Plus its hard on the starter

Keep in mind, NASCAR motors are ~350ci and make HUGE amounts of EFFICIENT power... but only last 1 race =)

 

[knochgoon24]

...
So... stroker motors can AND can not be daily drivers. Obviously, when you stroke a motor, you can only go so far. This 2.6L kit is pretty maxed out, which equals a lot THINNER cylinder walls. I wouldn't go higher than a 2.4L daily driver... for the only reason of the thickness of the cyl walls.
...

Why are you making thinner cylinder walls!?!?!?! They offer pistons from standard bore to 87.5mm. You don't have to change the cylinder wall thickness any from stock.

He's not taking a 2.0L 4g63 and turning it into a 2.6L, he's taking a 4g64 which started life a 2.4L and is stroking it to 2.6L. Key word... stroking it, not boring it out.

If you can stroke a 2.0L to a 2.3L and drive it, I don't see why you couldn't turn a 2.4L into a 2.6L.

The 2.6L stroker wasn't included in that "To Stroke or Not" article, but the differences between a 2.4L and 2.6L are probably pretty similar to the differences between the 2.0L and 2.3L.

 

[->PrOjEcTGS<-]

Keep in mind, NASCAR motors are ~350ci and make HUGE amounts of EFFICIENT power... but only last 1 race =)

Go out and drive your DSM around at 6000RPM accelerating WOT to redline every 20-30 seconds for a continuous three hours only letting off for 60 seconds every hour and see how long your engine lasts.

 

[DSMTriad]

Go out and drive your DSM around at 6000RPM accelerating WOT to redline every 20-30 seconds for a continuous three hours only letting off for 60 seconds every hour and see how long your engine lasts.

It'll start out as misses then excessive knock then BOOM!

 

[talon_42o]

So making a 2.0l to a 2.3l is ok for DD cause thats what I was thinking of doing. I have a 91 tsi awd with no 3rd and 4th gear I paid 700 for it. I also have a 95 tsi awd with 268 000 kms thats still runing strong with minor lifter tick. ANy suggestions ??

 

[c_riggan]

Wow! I started some debating, but the info is coming out now. Basically, I wanted to know if it is a good motor, and if anybody was running one as a daily. Then I might be able to hear how it is.

I was thinking stroker for the easy streetability, and really fun track days. Sure I could build up a 2.0 and have fun on the track, but it would alomost never hit boost on the street (unless I am hitting really high rpms).

I am not going to go right out and buy the whole set up (I'm not rich), it will take a couple years to build it, so buying another faster car is not an option, and where is the fun in buying a faster car? For me, the fun is in taking something (Like a DSM) and making it faster even it cost more in the long run.

As for higher CRs on the street and stroked motors with forged internals on the street. Ihave owned a stroked motor with high CRs that was a DD car and it was fine as a DD. Said car was a Mercury Capri RS 5.0 stroked to a 347 with forged internals running a 12.5:1 CR, a giant cam, shorty headers, Edlebrock intake and a holy 750 double pumper. The car made awesome amounts of power and was fun to race, but also was nice when driving street. It made alot of torque and meant I didnt have to downshift (and this is especially nice when you have a 4 speed as it had) when getting on the freeway or trying to pass somebody, it just pulled hard straight away from the lower end.

Was thinking the same concept could be applied to this eclipse. Fun track days, and easy pull when passing or merging (Big turbos tend to have a bit of lag in the lower range and less so when on a bigger engine). The last thing I want is a car that is fun on the track but sucks to drive home.

Thanks for all the input and debating, as this brings up many points that are valuable to me AND others thinking about a build. I think I may go grab a 64 block in a couple months to get this thing started (gotta finish the prelude re-build first, my room mate's car)

Chris

 

[stratt134]

Come on, I was talking basic engine theory for the people who don't really know what stroked is......... plus, i have personally gone 1,200 miles non-stop at 4000-4500 rpm with no problems

Why are you making thinner cylinder walls!?!?!?! They offer pistons from standard bore to 87.5mm.

What's standard bore on the 2.0? Smaller than 87.5mm bore??

edit * I didn't notice the 64 block vs the 63 block being used.

 

[knochgoon24]

What's standard bore on the 2.0? Smaller than 87.5mm bore??

Yes, actually both motors do.

The stock 4g63 has an 85mm bore.
The stock 4g64 has an 86.5mm bore.

 

[MidShipCivic]

so basically ... with a stroker motor.. it would induce more air at a shorter rpm... causing a turbo to spool up much faster as that air is exiting at a much lower rpm...
Would this mean you would need a much larger turbo to compinsate for the stroker?

Short rod high stroke engines (lower rod ratios) have the piston further down the bore at anycrank angle besides 0 and 180 crankshaft degrees. However valve motion is unchanged by rod/stroke ratio, because the chamber volume has grown larger
given the valve /same crankshaft degree. There is greater port velocities at the same crankshaft degree than longer rod ( longer rod shorter stroke engines).

Lower ratio engines can often handle more cam duration , because the additional velocity will have greater momentum at lower rpm. Bigger cams will idle better in short rod engines. Engines with higher rod stroke ratios ( shorter stroke, longer rods) are the opposite because of the inertia require to continue cylinder filling with long duration, and the velocities at low rpm are insufficient to create the inertia when the power band shifts upward in the rpm range. It's because the velocity increase to the point the charge start doing what it's suppose to do. Continue filling the chamber even though the pistons has started to rise on the compression stroke because the inertia is great enough to overcome the decrease chamber volume.

The piston also dwells longer at BDC thus allowing cylinder fill more.

Just think about motors in general.

Keep in mind, NASCAR motors are ~350ci and make HUGE amounts of EFFICIENT power... but only last 1 race =)

They are severely rule limited. Would you happen know their complete engine rules? They are V8's that are destroked, displacement limited and are only allowed to use certain gear ratios to keep them at certain rpm.

 

[delta448]

I have a couple of things to add, but this is overall a pretty good discussion.

Larger displacement and a lower redline is generally more desirable for street driving. It's more responsive and has better low end torque. Lower displacement and higher rpms are generally better for track cars because of the ability to achieve a higher speed in the same gear and not lose the acceleration advantage of the lower gearing by upshifting in order to go farther around the speedometer.

With a stock 86.5mm 4G64 bore it's not a 2.6L anymore, it's 2491cc's so it's "only" a 2.5L. Boring the cylinders affects displacement more as stroke increases.

Just because you increase stroke doesn't mean the rod ratio always has to be worse. It does in the case of the 2.5/2.6 Crower kit though. Sometimes a "stroker" piston design can more than compensate for the stroke increase, where the wrist pin of the piston is moved towards the piston crown. Higher rod ratios are much more desirable than low ones if you intend to make high horsepower or spin to high rpms. A higher rod ratio means less side-loading friction vs a lower rod ratio, more piston dwell time, better efficiency and smoother piston acceleration away from TDC and BDC -so less shock to the wrist pin and rod bolts at high rpms.

 

[DSMTriad]

I found this not for DSMs but some of the general ideas could be used.



the rod ratio in a gasoline engine determines the piston dwell at TDC. the longer the rod, the less downwards piston motion will be the result of the rod angle changing.

if the crank rotates 10 dergees, then a very short rod will be at a greater angle than fi the rod is very long. since the rod doesnt change length then some of the pistons downwards motion will be a result of this phenomenon, so the longer the rod, the longer the "dwell" and the longer the dwell the more complete combustion and higher cylinder pressure. The rod length is limited by other engineering conserns, like bloch deck height, piston height, and thus inherrent stability, and resultant wear. and so on.


In most large cubic inch engines it is hard to get a very high ratio. A Stock 350 Chevy has a 1.64:1 RL/S ratio, which is not very good. By increasing the rod length to 6" the ratio increases to 1.72:1, which is much better. You can squeeze a 6.1" rod in a 350 with little trouble, but longer than that requires plugging the piston pin bores after assembly to support the oil rings. It is not worth the extra expense for the little gains, so a 6" rod in a small-block Chevy has become common because everything fits right in. With endurance engines, longer rods are always better. Most endurance engines are using a RL/S ratio of at least 1.9:1 and some as high as 2.2:1. Before you go out and buy longer rods, let me just say that the gains are very small. This debate has been argued for years and will not end anytime soon. In my opinion, if are building an engine and need new rods and pistons, a longer rod will cost about the same. That makes the small benefits worth it. I would not waste my money buying longer rods if you have a good set of rods that you can use. Use that money to make more power elsewhere in the engine.

Rod Angularity

A longer rod reduces the maximum rod angle to the cylinder bore centerline. Less rod angle will reduce piston side loading; there will be less friction and less bore wear. Less rod angle also gives better average leverage on the crank for a longer period of time. A 5.7" rod with a 3.48" stroke (stock Chevy 350), will have a maximum of 17.774° rod angle. Switching to a 6" rod will reduce that to 16.858°, assuming that the wrist pin has no offset. (on a ford small block, installing the pistons backwards will actually gain almost 20 Hp. since the piston acts like it was mounted on a longer rod, as the ofset is reversed, at the price of increased noise and wear)

Piston Pin Height

A higher pin height will reduce piston rock and aid ring seal. please no screaming and name calling about anything about a tighter ring pack, we are talking about pin height and pin height only. Moving the pin closer the the center of gravity of the pistons makes the piston more stable.

Rings

As the compression height is reduced, the space for the ring pack also get reduced. This can be a problem on some engines. It is good for power to have the top ring as close to the top as possible, but this is limited to the strength of the top ring land. As it becomes thin, it becomes weak. High output engines (especially nitrous engines) need a thicker ring land to keep the cylinder pressure from pinching the top ring. In my opinion, if you have to compromise ring location, it would be better to run a slightly shorter rod.

Skirts

Shorter skirts are usually combined with a shorter piston for a longer rod, but they are not really related. There is no reason to reduce the size of the skirts just because the pin location changed. A shorter skirts are used to reduce friction and lighten the piston. The cost is a little less stability, but it is arguable that a lighter piston with a higher pin height does not need the extra stability. For a street car, I would increase the rod length if it meant a reduction is skirt size. Most of the things listed here are for competition motors to gain a few hp, not worth a lot of effort for most street engines.

Piston-to-Valve Clearance

A longer rod decelerates toward TDC and accelerates away from TDC slower than a shorter rod, so piston-to-valve clearances are tighter with a longer rod. This may require deeper valve relief's in the piston (but probably not). A short rod is just the opposite, there is more clearance because the piston decelerates toward and accelerated away for TDC faster.

Piston Velocity

A longer rod reduces peak piston speeds slightly and delays peak piston velocity until the piston is further down the bore, which gives the intake valve more time to open more. Peak piston velocity is usually somewhere around 75° ATDC and since most cams cannot fully open the cam until at least 106° ATDC, it leaves the valve as a major obstacle when airflow demand is at its greatest. By delaying peak piston velocity, even if it's only 1 or 2 crankshaft degrees, it can allow the valve to open another 0.010-0.015", before peak airflow demand is reached. Not a huge help, but a step in the right direction. With a 350 Chevy, switching to 6" rods from 5.7" ones will delay peak piston velocity from 74.5° to 75.5°.

Piston Acceleration / Deceleration

Reducing piston acceleration / deceleration from and toward TCD will reduce tensile loading of the rod, the number 1 cause of rod failure. A Chevy 350 with 5.7" rods will have a peak piston acceleration rate of 101699.636 ft/sec/sec at 7000 rpm. Swapping in 6" rods will reduce that to 100510.406 ft/sec/sec at that same rpm. That is a reduction of 1189.23 ft/sec/sec.

Intake Runner Volume

Since it is easier for an engine to breath with a longer rod, less runner volume is needed. This allows more room for an intake system (this is a very small gain, but is real).

Exhaust Gas Scavenging

A longer rod is moving slower at TDC, which reduces the speed of the exhaust gasses during the overlap period. This reduces the scavenging effect at low rpm and reduces low rpm power slightly (makes the engine run more cammie). A short rod on the other hand moves faster past TDC and increases the scavenging effect and help low rpm power.

Ignition Timing Requirements

Due to the fact that the longer rod moves past TDC slower, it gives the charge a longer time to burn. So you need less timing for peak power. Using less timing also reduces the chance of detonation; so higher compression ratios can be used. Switching from 5.7" to 6" rods on a 350 Chevy can allow as much as 1 full point increase in compression. In other words, if you could only run 9.5:1 with 5.7" rods, you could run 9.6:1 with 6" rods.


Longer Rod Pros

Less rod angularity
Higher wrist pin location
Helps resist detonation
A lighter reciprocating assembly
Reduced piston rock
Better leverage on the crank for a longer time
Less ignition timing is required
Allow slightly more compression to be used before detonation is a problem
Less average and peak piston velocity
Peak piston velocity is later in the down stroke
Less intake runner volume is needed

Longer Rod Cons


Closer Piston-to-valve clearances
Makes the engine run a little more cammie at low rpm
Reduces scavenging at low rpm

Shorter Rod Pros


Increased scavenging effect at low rpm
Helps flow at low valve lifts (a benefit if the heads are ported with this in mind)
Slower piston speeds near BDC
Allows the intake valve to be open longer with less reversion
More piston-to-valve clearance
Can allow for a shorter deck height

Shorter Rod Cons


More rod angularity
Lower piston pin height (if the deck is not shorter)
Taller and heavier pistons are required (again, if the deck height is not reduced)
More ignition timing is required for peak power

some of this must be attributed to grape ape racing...

 

[MidShipCivic]

I have a couple of things to add, but this is overall a pretty good discussion.

Larger displacement and a lower redline is generally more desirable for street driving. It's more responsive and has better low end torque. Lower displacement and higher rpms are generally better for track cars because of the ability to achieve a higher speed in the same gear and not lose the acceleration advantage of the lower gearing by upshifting in order to go farther around the speedometer.

Strokers aren't limited by RPM. Breathing is.

Lower displacement engine must rev higher and use shorter gear (number wise) to meet their peak power faster and more efficiently.

 

[dsm-onster]

Tensile strength limits rodbolts. The longer stroke causes more tensil stress on the rod bolts, if the reciprocating assembly weighs the same.

Now a stroker does have a lighter piston than a stock 2.0L motor, but not a 2.4 4g64 (where all the same piston/rod brands are used). The 2.3 stroker sees the same tensile stress as a 2.0L at about 400rpms earlier, which isn't bad; because of the higher wristpin height and consequently a ligher piston (again where all the same piston/rod brands are used).

That is a minute difference unless you bore the stroked 2.3 to 86.5mm and make it a 2.4. Now you're adding weight to the piston. And that same tensile stress comes on significantly earlier in the rpm range.

Tensile stress becomes the limit of the rod bolt and that limit is at different places in the rpm range for different strokes and piston/rod weights.

 

[delta448]

Nice post Matt. I think you said it much more clearly than me, and in much more specific detail.

Strokers aren't limited by RPM. Breathing is.

Absolutely, -so long as the rods and rodbolts are stong enough to handle the rpms- and the same is true for any engine regardless of displacement. As long as the strength of the materials is enough, airflow limits are rpm limits. Sonic choking certainly does occur quicker with more displacement.

 

[stratt134]

They are severely rule limited. Would you happen know their complete engine rules? They are V8's that are destroked, displacement limited and are only allowed to use certain gear ratios to keep them at certain rpm.

Wow, for being so bold, you are a... well let us just say you missed it a little on that one...

 

[MidShipCivic]

Wow, for being so bold, you are a... well let us just say you missed it a little on that one...

I don't follow?

 

[MidShipCivic]

Here are the specifications on the connecting rods in the BC 2.6L kit.

Pistons are custom and entirely is your decision.

6.000" center to center

1.890" big end bore

1.038" big end width

22mm pin


6'' rod and 106mm stroke makes a 1.43:1 rod stroke ratio.
An oem engine that has this exact ratio is the Nissan QR25DE.

 

[c_riggan]

So... I have located my 4g64 block.. In a galant. Timing belt went so the head is done. But thats ok... gonna use a 63 head anyway. Getting the engine for 200 bones....

 

[c_riggan]

So, I picked up the engine and have been searching various sites to try to find out which timing belt to use when dropping the 63 head on it. Being that the deck height is a bit taller, I dont think a 4g63 belt will work, and the 64 belt shouldnt either because of swapping to daul cams.

Can anybody provide some insight on this? I would very much appreciate it, as I need to start building her, cause I'm pretty sure my poor little 63 is just starting to walk.

Thanks