Advantages of a 2.1 Stroker?

[ZABMANN]

Are there any advantages to de-stroking my 2.4 to 2.1?

 

[Strm Trpr]

This is a 9:1 2.3L Stroker Motor
100mm Crank
150mm Rods

 

[Strm Trpr]

This is a Long Rod 2.0L using the same exact piston but an 88mm crank and 156mm rods.
All I changed was the stroke and rod length.
Notice how the compression ratio drops a full point!

 

[TunaTalon]

When you see a piston specified with a given compression ratio, that specification is at a given stroke and combustion chamber volume.

A stroker piston with a CR of 8.8:1 for a 2.3L stroker 4G63 is specified for a 100mm stroke and a combustion chamber volume of 47cc. It is certainly not specified as 8.8:1 with an 88mm stroke.

 

[Strm Trpr]

When you see a piston specified with a given compression ratio, that specification is at a given stroke and combustion chamber volume.

A stroker piston with a CR of 8.8:1 for a 2.3L stroker 4G63 is specified for a 100mm stroke and a combustion chamber volume of 47cc. It is certainly not specified as 8.8:1 with an 88mm stroke.

This is exactly the problem.

It can be done with a custom 2.3L piston, but if you want a 9.0:1 static compression ratio when it's all said and done someone is going to have to tweak the volume of the dish in the piston to get the compression ratio back up.

By changing the piston dome volume to -8.8cc's from -17cc's, one can achieve a 9:1 compression ratio using a custom 2.3L piston, 88mm crank and 156mm rods.
Now this might be a motor worth looking into.

 

[SBR Joe]

it will not effect CR...heres the info i just got back from wiseco..


ME: Ok, so if were using a 2.3 stroker piston with an 8.5:1 CR, in a long rod 2.0 setup and the 88mm crank, what would it do with adverstised CR? Would it raise it or lower it seeing the dish isn’t designed for that stroke?

Vic at Wiseco: To figure this out I need

gasket thickness
stroke
bore size
head cc's
how far down in the hole it will be


ME: Stroke 88mm
Headgasket .051
Bore size 85.5
Head cc’s (whatever 4g63 head is)
156mm rods using the 2.3 stroker pistons…hope this helps.


Vic at Wiseco: 8.528:1 Compression

 

[Strm Trpr]

Vic at Wiseco is wrong.
It just doesn't add up.
I've explained it a few different ways already.

The dish on the Stroker Piston and the additional deck clearance of 0.3mm, (.012") is designed to offset the extra 12mm of stroke.
This additional stroke increases total cylinder volume.

Static Compression Ratio is:
Total Cylinder Volume / Compressed Volume, (Piston at TDC).

If the total cylinder volume is decreased because of using an 88mm stroke crank rather than the 100mm stroke crank,
but the compressed volume remains the same, you will have a lower compression ratio, plain and simple...

 

[SBR Joe]

Vic at Wiseco is wrong.
It just doesn't add up.
I've explained it a few different ways already.

The dish on the Stroker Piston and the additional deck clearance of 0.3mm, (.012") is designed to offset the extra 12mm of stroke.
This additional stroke increases total cylinder volume.

Static Compression Ratio is:
Total Cylinder Volume / Compressed Volume, (Piston at TDC).

If the total cylinder volume is decreased because of using an 88mm stroke crank rather than the 100mm stroke crank,
but the compressed volume remains the same, you will have a lower compression ratio, plain and simple...

No offense, but ill take the word of a major piston manufacturer over anyone else.

 

[Strm Trpr]

No offense, but ill take the word of a major piston manufacturer over anyone else.

No, I hear you, but the math just doesn't add up.

 

[SBR Joe]

No, I hear you, but the math just doesn't add up.

Im not the biggest math whiz in the world with ADD, so i cant asess it on my own. hahahah....thats why i had him do it for me since they basically just have to put numbers in a computer that tell them the outcome.

 

[Strm Trpr]

The math in my posts above using Eagle's Calculator state otherwise.
I would call Bryant at Wiseco.
He's the man when it comes to custom piston design.

Maurice above states the problem very clearly.

 

[TunaTalon]

Math is easy, communications is hard.

When Joe said:

ME: Ok, so if were using a 2.3 stroker piston with an 8.5:1 CR, in a long rod 2.0 setup and the 88mm crank, what would it do with adverstised CR? Would it raise it or lower it seeing the dish isn't designed for that stroke?

The phrase "...so if were using a 2.3 stroker piston with an 8.5:1 CR, in a long rod 2.0 setup..." could be understood that the piston was designed for an 8.5:1 CR in a 2.0L setup.

I agree with Chris and the Eagle calculator on the math. To clear up the communications Joe could go back to Vic with:

"Using a piston designed for 8.5:1 CR in a 4G63 with 100mm stroke in another 4G63 with the same stock combustion chamber volume and head gasket thickness, but an 88mm stroke, what will be the effect on CR?"

 

[SBR Joe]

I told him this was using a 2.3 stroker piston, so im certain he factored that in.

Math is easy, communications is hard.

When Joe said:



The phrase “…so if were using a 2.3 stroker piston with an 8.5:1 CR, in a long rod 2.0 setup…” could be understood that the piston was designed for an 8.5:1 CR in a 2.0L setup.

I agree with Chris and the Eagle calculator on the math. To clear up the communications Joe could go back to Vic with:

“Using a piston designed for 8.5:1 CR in a 4G63 with 100mm stroke in another 4G63 with the same stock combustion chamber volume and head gasket thickness, but an 88mm stroke, what will be the effect on CR?”

 

[Rob10_99]

There's no way this can have the same CR with all the same factors excluding stroke, it does not add up.

 

[TunaTalon]

I told him this was using a 2.3 stroker piston, so im certain he factored that in.

The math has been checked, and confirmed.
The communication has not been checked but we are “certain”?

As Rob10_99 says something does not add up; and it’s not the math.


Oh, and I’m certain my wife never mis-understands what I say.

 

[Strm Trpr]

The math has been checked, and confirmed.
The communication has not been checked but we are "certain"?

As Rob10_99 says something does not add up; and it's not the math.


Oh, and I'm certain my wife never mis-understands what I say.

Yeah, isn't this the truth.

Last edited by TunaTalon : 09-28-2009 at 01:05 PM. Reason: Added wink in case single tooners think that last bit was remotely possible.

 

[dsm-onster]

It is remotely. But the remote is usually without batteries and under one the couch cushions. By far the hardest remote to keep track of.

 

[We're on Boost]

Hey I've been meaning to post this stuff for awhile. There was a pretty good discussion about rod ratio in this thread, so here goes.
One of the few really good tech projects ever written up in DSport magazine was the Long rod vs Short rod shoot out. It was actually called the Dart Engine Challenge, parts 1, 2, and 3. Yeah it was done with normally aspirated Honda engines ok sorry. They used Dart blocks with as I recall different deck heights to accomodate the different rods without changing the crap out of everything else. They ran the 2 motors on a DTS engine dyno, not a chassis dyno, because they knew they would be looking for a small hp difference and didn't want it to get lost in all the noise of the tranny, tires, and so forth. They built the 2 blocks. Used 1 head-intake-cams assy which they swapped back and forth onto the 2 blocks. Sounds like fun hey? Wish I could afford to do sh*t like this!

These engines were ~260 hp engines. They said most of the experts were predicting more hp from the long rod. So they were surprised when the short rod made about 8 hp more. That's about 3%. The short rod made more torque through the entire rev range tested. I still think the long rod would probably have some advantages like longer engine life - which could be a big plus with high boost engines. BTW the rod ratios in this shootout were 1.62 and 1.47.

This series is a good read. The final testing and results are in issue 35 of DSport, Nov 2005. You can draw your own conclusions. If I have time I'll scan the final hp comparo and imageshack it. I do have this issue and could scan the whole article if anybody would like a copy.

You must be logged in to view this image or video.

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[cheekychimp]

The last post is interesting and it is disappointing that it received no replies. I struggle with some of the math involved here but I am a strong believer in the idea that you don't get something for nothing. I often wondered without any scientific basis for my ideas how the long rod motors could maintain or even surpass the bottom end torque of the standard 2.0L and then go on to rev higher!

Now that said, I wonder if the bore sizes used in the Dart Engine Test mentioned were all the same. There seems to be some argument for using the standard 85.5mm bore over the 87mm one you are forced to use with the G4CS/4G64 block. Now I realize it might not be cost effective to do so, but I have often wondered if it would be beneficial mechanically or performance wise to 'sleeve' the G4CS block and rebore it to 85.5mm and then use 162mm long rods.

As far as the benefits of revving any higher are concerned, I am looking at this from a slightly different standpoint.

Firstly, speed. There seems to be a great deal of concern about power falling off at higher rpms but once you are moving and have momentum, far less power is required to maintain speed than is required to overcome inertia and accelerate. Since your crankshaft spins at a rate proportionate to that of your axles, as long as you are not slipping at the clutch or spinning tyres, the faster your engine revs in any given gear the faster you go. As long as you maintain 11,000 rpms you will maintain that speed, how much horsepower you are producing is irrelevant.

Secondly, longevity of both the block and the head. Irrespective of whether the engine is making more power at higher rpms it stands to reason that if an engine is built for 11,000 rpms and only sees 8000 rpms regularly, it should live a long time and quite possibly survive a missed shift at 8000 rpms that would cause an 8,500 rpm engine catastrophic failure.

 

[PieEyedPiper]

GeekyChimp should come back.

And yes, I'm posting on this old dinosaur's bones. The 2.0 LR vendor thread was dug up today and it kind of re-kindled the fire.

So, with years now past - has there been consensus? I have to admit, If you take Maurice's post/list about what a longer rod will do and combine it with the dart analysis it sure does make for an argument against SBR's claim regarding the LR 2.0.

Is/was anyone else selling the LR 2.0?

 

[We're on Boost]

As far as I know this general subject is still on-going with different opinions, and probably with some components available that weren't available in 2009. Most of what I have seen about it is in evom. If there is anything like a consensus (in evom) I would say it is that the most desireable engine overall is a 2.3 liter stroker. But what rods, pistons, bore, block, crank, etc, I don't know. David Buschur is one of the chief proponents of the 2.3 - he makes a version he calls the "high rpm 2.3 liter" or something like that.
BTW in the Dart engine comparo, the 2 engines definitely had the same bore.