ok, I was going to wait to drop this on people but the cat is already out of the bag, so to just kind of throw the information out there here we go.

I've been thinking a lot about hybrids, and why exactly we can't mix and match ecotec parts and it dawned on me after having a random conversation with ryan (oldskool).

Basically, bottom end geometry is super imperative when you are INCREASING your stroke. Why? Because you're reducing your clearances with the deck height, and usually pushing things to the outer limit of such.

But with DEstroking, things are a bit different because you're increasing your clearances. Working within the bounds of the ecotec architecture, we actually have quite a few possibilities of taking mix/match engines to the next level with minimal custom part purchases.

Why would we do this? Because we can lego together a combination that will give us an ideal rod /stroke ratio, as well as maintaining a decent displacement. There are three seperate possible combinations that I came up with, however the third has one small hangup that will potentially mean it won't work... however, there is a work around.. I'll explain further when we get to it.

So what do we have to work with? the port injected ecotec engines will all swap into a Jbody with minimalistic modifications. Anything that doesn't use an L61 crank will need to utilize an external crank trigger wheel. Anything that uses an LSJ crankshaft will also need an LSJ clutch and flywheel as well as a GM transmission spacer (a rather cheap part... GM p/n 12583853). All these combinations will need an L61 oilpan bolted to the bottom of the LE5 block. All these combos need to be used with either an LSJ head or L61 head. VVT will not work in the Jbody with out some serious r&d and modification.

All of the possible combinations will utilize an LE5 block. The LE5 block is a genII block, which has improved rigidity and strength when compared to genI blocks.

here's what we have to work with for the bottom end:

LE5 (2.4L n/a)
bore = 88mm
rods = 143.7386mm
stroke = 99mm (also sometimes quoted as 98mm)
wrist pin diameter = 20mm
R/S ratio = 1.45 (aka GARBAGE)

L61 (2.2 n/a)
bore = 86mm
rods = 146.5mm
stroke = 94.6mm
wrist pin diameter = 20mm
R/S ratio = 1.54

LSJ (2.0 s/c)
bore = 86mm
rods = 145.5mm
stroke = 86mm
wrist pin diameter = 23mm
R/S ratio = 1.69

so from these, I can think of a few pretty sweet combinations. One that uses all OEM parts, one with custom rods, and the other that sorta won't work but sorta will.

*interesting side note: the L61 has the longest rods, NOT the LSJ.. hmm interesting. I'm beginning to wonder if the deck height is different across the different variants.


2.1L OEM rod

engine components:
-LE5 block
-LE5 pistons
-L61 rods 146.5mm
-LSJ crank

extras:
-external trigger wheel
-GM trans spacer p/n 12583853
-LSJ clutch
-LSJ flywheel
-IF block has integrated oil cooler, you need the external oil cooler adapter in order to use the L61 thermostat housing. more information at the bottom of the post)

attributes:
86mm stroke x 88mm bore
r/s ratio of 1.70:1
piston is 3.74mm lower in the cylinder

here we have the 2.1L ecotec. Probably the most scattered mix of OEM parts I can think of. It has a r/s ratio akin to the LSJ's 1.69:1, which means it will be very good for upper midrange and top end power with a decently flat torque curve depending on camshaft selection. the 2.1L is a minimal displacement loss for a more rev-friendly short stroke. The piston being 3.74mm lower in the bore will drop the static compression slightly which will counteract the compression increase of the 88mm, 10.5:1 cr piston shooting into the L61/LSJ combustion chamber.


2.1L custom rod

-LE5 block
-LE5 pistons
-Custom length rods 155.74mm
-LSJ crank

extras:
-external trigger wheel
-GM trans spacer p/n 12583853
-LSJ clutch
-LSJ flywheel
-custom made 12mm longer rods (155.74mm)
-IF block has integrated oil cooler, you need the external oil cooler adapter in order to use the L61 thermostat housing. more information at the bottom of the post)

attributes:
86mm stroke x 88mm bore
r/s ratio of 1.81:1
piston is normal height

this engine has the same displacement as the other engine, but with the custom length longer rods. the longer rods will maintain the piston at the correct height, and maintain the higher compression resultant from using the 88mm piston into the L61/LSJ head. The longer rods will also move the r/s ratio to 1.81:1, which means the engine will be really happy revving extremely high. This would probably be a very good n/a setup.


2.3L non-functioning version

-LE5 block
-LE5 pistons
-L61 crank
-L61 rods 146.5mm

extras:
-IF block has integrated oil cooler, you need the external oil cooler adapter in order to use the L61 thermostat housing. more information at the bottom of the post)

attributes:
94.6mm stroke x 88mm bore
r/sratio of 1.54:1
piston is 1.64mm higher in the bore, pushing the piston above the deck surface (assuming the compression height is NOT enough to compensate which I'm assuming it is NOT).

this setup is basically a big bore L61 with a slightly domed piston. However, it seems that the longer rods of the L61 will push the piston above the deck 1.64mm, which means it probably wouldn't be a good idea to try this combination. However, you could order custom pistons in order to stay within the block, and maintain the decent r/s ratio of 1.54:1. This combinatino also requires no external crank trigger since the L61 crank has the 6+1 pattern integrated into it. I would have a more concrete argument for this engine if I had the LE5's compression height, but have yet to find that dimension.

2.3L short rod

-LE5 block
-LE5 pistons
-LE5 rods 143.74mm
-L61 crank

extras:
-IF block has integrated oil cooler, you need the external oil cooler adapter in order to use the L61 thermostat housing. more information at the bottom of the post)

attributes:
94.6mm stroke x 88mm bore
r/sratio of 1.52:1
piston is 2.2mm lower in the cylinder

this 2.3L will work with all oem parts, the downside of this combination is that you get a slightly worse than L61 r/s ratio, although on the plus side the r/s ratio is better than the LE5. the piston being lower will also slightly fight the compression bump when using the 88mm piston and the L61/ LSJ head.

these combinations (unless otherwise noted) will work. how WELL they will work comes down ultimately to real world testing. any of the engines could be fitted with custom rods in order to eliminate the piston being lower in the combustion chamber, however I don't think it would make too much of a difference unless you wante to maintain the CR bump by using the 88mm piston with the LSJ/L61 head.

*this company makes an adapter that allows you to run an external oil cooler and it bolts in place on the LSJ block... not 100% sure it will work on the LE5 however. Majority of LE5s came with no oil cooler though.

http://www.unique-fabricating.com/

the benefits of a good r/s ratio are really worth their weight in gold, especially in an engine being used for racing or weekend warriors. a better r/s ratio will slow down your piston speed at a given rpm, reduce piston side-wall loading, and increase dwell at TDC.

interesting idea, I had heard some rumblings from a certain common friend in the area you were looking into doing some bigger things.

I heard about this as well, I'm glad to see some more in depth info on this. Im kind of tempted to try the 2.3 short rod when I finish assembling my le61...Are there any physical/dimensional differences between cranks (other than the reluctor wheel obviously) that it would require any modification to fit the l61 crank to the le5 block and rods, or is it just swap and go?

EVILution (KGM Godfather) wrote:I heard about this as well, I'm glad to see some more in depth info on this. Im kind of tempted to try the 2.3 short rod when I finish assembling my le61...Are there any physical/dimensional differences between cranks (other than the reluctor wheel obviously) that it would require any modification to fit the l61 crank to the le5 block and rods, or is it just swap and go?

all ecotec crankshafts have the same main journal diameter and rod journal diameter. drop in and go. the only catch MIGHT be the reluctor ring not lining up, but I don't see this happening.

the only option you have with swapping rods is between L61 and LE5. both have 20mm wristpins. the LSJ uses 23mm, and so you'd need to either bore out the LE5 piston or have a custom one made.

Some food for thought...

k24
Bore = 87mm
Stroke = 99mm
Rod Length = 152mm
--> R/S = 1.54 (identical to the LD9)

...and there are plenty of these revving out to 8000+ RPMS and making ~300whp NA.


I think it's great that the ECO and Quad guys lately are trying to get creative with improving r/s, but I personally believe you guys are putting way too much stock into this figure of merit.




I have no signiture

I agree with whalesac, r/s ratio isnt as big of a deal as you're making it. My computer simulation says that the le5 with stock hg, ammfab race port head, generic "mild" cam, and the MP62 with a 2.8 pulley will make its peak power of 400 crank at the 7000 rpm redline and be still climbing at that point. I'll run those other engines if I have time this weekend.


1994 Saturn SL2 Home Coming Edition: backup car
2002 Chevy Cavalier LS Sport Coupe: In a Junk Yard
1995 Mazda Miata R-package Class=STR
Sponsored by: Kronos Performance

WPI Class of '12 Mechanical Engineering
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Very interesting info PJ....some great ideas in there.

I agree with both sides of this r/s debate, on the one side....having a higher r/s ratio gives a laundry list of benifits which have already been listed.

On the other side, if you take a stock LE5 with a r/s of 1.45 (which from what they say is horrible) GM spins them from the factory to 6900rpm in the Solstice and Sky, which I believe is the highest redline on a factory Ecotec. I have also seen dyno graphs of Intake/Exhaust/Tuned LE5's making peak HP over 6500rpm.

I'm sure they would make more power and higher rpm power with an improved r/s ratio, the thought of having a 1.8:1 r/s ratio is awesome, but is it really nessacary?

I dunno, I don't know what to think about this....VERY interesting topic tho.....hopefully we can get some good debate going about this.

Leafy (Club Jeffie FEA man) wrote:I agree with whalesac, r/s ratio isnt as big of a deal as you're making it. My computer simulation says that the le5 with stock hg, ammfab race port head, generic "mild" cam, and the MP62 with a 2.8 pulley will make its peak power of 400 crank at the 7000 rpm redline and be still climbing at that point. I'll run those other engines if I have time this weekend.

Also, one point about that program is it can't compensate for r/s, as there is no entry for rod length.

So your r/s could be 1.5:1 or 2.5:1 and it wouldn't know the differance.

Looking forward to more updates..

very intriguing......in for more updates





RIP JESSE GERARD.....Youll always be in my thoughts and prayers...

This could make a need for another run of trigger wheels. I have already sold 38, but with this new information out there this could be a whole new ball game. I am definitely interested in the 2.1 setup with the L61 Rods, LSJ Crank and, LE5 Block/pistons.



LE61T PTE6262 Powered

Just ran the math on the 2.1 OEM Rod set-up:

I'm getting 7.3:1 CR....can anyone confirm?

here's some food for thought.

guys on honda-tech, team integra, etc go out of their way to build combos with good r/s ratios and we all know how the n/a honda engines (B series and K series in particular) perform.

I think a good r/s is worth the trouble.

Good read pj


PRND321 Till I DIE
Old Motor: 160whp & 152ft/lbs, 1/4 Mile 15.4 @88.2
M45 + LD9 + 4T40-E, GO GO GO

I would like to add that it has been dyno proven many times that in a chevy 350 going from a 5.7" rod to a 6" rod can add as much as 40hp depending on mods due to the engine not having to work as hard to rotate. We obviously would not see 40hp but gains would be there none-the-less!

newt wrote:Just ran the math on the 2.1 OEM Rod set-up:

I'm getting 7.3:1 CR....can anyone confirm?

rod length has no effect on static compression.

DaFlyinSkwirl (Pj) v2.0 wrote:here's some food for thought.

guys on honda-tech, team integra, etc go out of their way to build combos with good r/s ratios and we all know how the n/a honda engines (B series and K series in particular) perform.

I think a good r/s is worth the trouble.

Sure, but I think you guys are using r/s as a crutch and overlooking the more critical components, such as head flow, cams, valvetrain weight. The reason K24s can make so much power, is because they use the higher flowing K20 head. The argument of R/S is not much different compared to knife edging. Does it help? Absolutely, but is it really worth the loss in displacement.




I have no signiture

if we are talking high revvers, then journal size/ bearing speed is a big concern, gearing, but r/s is one piece of the puzzle, and i think its fair to say this is a decent way to go about it.

granted the eco head isnt designed as well as the k series head, but we can still get some pretty decent flow numbers.

furthermore, if reducing rod length doesnt effect compression (whether it be static or dynamic), why does spacing the head up effect it? either way you are increasing the volume in the chamber which should in theory reduce the squeeze, correct?

Whalesac wrote:

newt wrote:Just ran the math on the 2.1 OEM Rod set-up:

I'm getting 7.3:1 CR....can anyone confirm?

rod length has no effect on static compression.

I know, but in that set-up you are reducing the stroke by using the LSJ crank instead of the LE5 crank, while the CC of the combustion chamber remains unchanged, except for the 3.74mm deck height, which further lowers it.

Thus I got 7.3:1 CR.

For the 2.1 Custom Rod set-up I get 9.8:1 CR

Both of those figures assume the stock LE5 deck height is zero and don't account for the valve reliefs in the factory pistons.

DaFlyinSkwirl (Pj) v2.0 wrote:if we are talking high revvers, then journal size/ bearing speed is a big concern, gearing, but r/s is one piece of the puzzle, and i think its fair to say this is a decent way to go about it.

granted the eco head isnt designed as well as the k series head, but we can still get some pretty decent flow numbers.

furthermore, if reducing rod length doesnt effect compression (whether it be static or dynamic), why does spacing the head up effect it? either way you are increasing the volume in the chamber which should in theory reduce the squeeze, correct?

Correct.

It was my understanding that the ECO is a 0-deck height engine. If you are talking about changing rods, i was under the impression that you would maintain that same deck height with custom or modified pistons. If you don't maintain that 0-deck height, then yes, the static compression will change. I misinterpreted what Newt was saying. That was my fault. Sorry.




I have no signiture

whalesac, no worries. i didnt know if maybe i missed something.. i dont claim to know everything about engines which is why i was a bit worried i may have based some of my ideas on false info.

newt, are you taking into account that the LE5 pistom is 10.5:1, and that the L61 /LSJ chamber is smaller than the LE5 chamber? i knew compression would drop but from 11.x:1 down to less than 8 seems like a big difference.

the 2.1L custom rod ecotec should have compression up near 11.5:1 since ur keeping the piston at its normal height.

also, dynamic compression is gonna be a lot lower than static.. so of we are comparing static to dynamic is apples and oranges. dynamic is always lower, i think 8.5:1 is safe on pump gas, not sure what the upper and lower limits are.

i thought the le5 and l61 heads were the same casting.............. anybody got pics of the chambers on these 2 heads. also just to throw my .02 in i see the ideal r/s ratio as being about 1.75:1 from what ive read over the years and yes if i were building a hybrid engine the r/s ratio would def be something i would try to get into my "ideal" range.


mike


i make neons and j-bodys go fast

DaFlyinSkwirl (Pj) v2.0 wrote:whalesac, no worries. i didnt know if maybe i missed something.. i dont claim to know everything about engines which is why i was a bit worried i may have based some of my ideas on false info.

newt, are you taking into account that the LE5 pistom is 10.5:1, and that the L61 /LSJ chamber is smaller than the LE5 chamber? i knew compression would drop but from 11.x:1 down to less than 8 seems like a big difference.

the 2.1L custom rod ecotec should have compression up near 11.5:1 since ur keeping the piston at its normal height.

also, dynamic compression is gonna be a lot lower than static.. so of we are comparing static to dynamic is apples and oranges. dynamic is always lower, i think 8.5:1 is safe on pump gas, not sure what the upper and lower limits are.

Yup, I took that into consideration, Those numbers i posted should be accurate I think.

I'm on mu phone right now, I'll post more when I get to a computer.

But, it's cause you are reducing the stroke, the cylinder at BDC has less volume, so it's compressing less air into the same space (combustion chamber).

That's why there is such a drop in compression.

For all this long rod talk n compression issues there are simple fixes. Use the longer rod I'm pretty sure you can get .75mm undersize bearings, have the crank offset ground to help a little and I'm sure there is enough meat to have the top of the piston milled to zero deck height. I can look up the minimum thickness later when I'm not posting from my phone.

AWESOME thread!!

On the 2.1 OEM rod set up i came up with 9.87:1, neglecting the valve reliefs in the LE5 pistons and using a standard 1mm LE5 HG. Take it for what it's worth.

http://www.race-cars.net/calculators/compression_calculator.html

On the topic of R/S ratio - consider what it means for the car your building and the goals/plans you have for it. As mentioned, GM gave the engine that is worst suited to revving the highest redline of any ecotec variant. If you're building an all out race car that is going to rev constantly, of course you'd better damn well pay respects to r/s. If you're building a gutsy street car that probably won't see north of 7000 rpm in it's life - it probably doesn't matter as much.

Personally - I favor the 2.3L short rod. I came up with 10.7:1 c/r on that set up with a standard 1mm HG, NO need for the external wheel.

Yeah the 2.3 short rod doesnt sound bad.

GM also put the best engine suited for a turbo in their line up to get a super charger. The 2.4 is going to love the blower once I get it on it. Trouble is, I'm really going to need that exhaust so I can get my spark advance back up. I finally fixed my iat spark table to make the iat temp I normally operate at have 0 timing change and well... It put me at 10*-12* (going down to 6* when I hit 15 psi, which seems to be only tonight). I foresee that going down to single digits and 0-2 respectively with the 2.4 bottom end and the 11:1 comp. I almost want to bitch out and get a thicker head gasket but I really want all that comp with the blower because it will be @!#$ sick.


1994 Saturn SL2 Home Coming Edition: backup car
2002 Chevy Cavalier LS Sport Coupe: In a Junk Yard
1995 Mazda Miata R-package Class=STR
Sponsored by: Kronos Performance

WPI Class of '12 Mechanical Engineering
WPI SAE Risk and Sustainability Management Officer