I'm still researching and building my car (not a honda) but I know where the all motor 4 banger knowledge is at.

I'm wondering what engine you guys use (B, K, H, F, D, whatever) that is close to a 1.68 rod ratio, and what kind of rev range is expected out of such? Dyno chart would be swell.

I've been digging around for a long time here and on club-integra, but its a lot of information to digest.

the engine I'm using isn't a honda engine, but as a comparison point its a 2.0 liters, 86mm x 86mm and a rod ratio of 1.68. compression is sort of meek at 9.5:1

I figure if I can see a similar honda engine (more concerned with stroke and rod ratio matching than anything else) I can get a ballpark idea of what this thing is capable of.


Thanks for the help guys.. any insight is greatly appreciated.

 

D16A6, Z6, Y7, Y8 137mm 90mm 1.52:1
B16A1, A2, A3 134.4mm 77.4mm 1.74:1
B17A1 131.9mm 81.4mm 1.62:1
B18A1, B1, B20B4 137mm 89mm 1.54:1
B18C1, C5 138mm 87.2mm 1.58:1
H22A1 143mm 90.7mm 1.58:1
H23A1, A4 141.5mm 95mm 1.49:1
K20A, A2 139mm 86mm 1.62:1
K24A 152mm 99mm 1.54:1

 

K20A is the closest to your R/S ratio with a 1.62:1 R/S. It has a red line of 8600-8800(i-VTEC) off the assembly line.

 

Why are you concerned with rod ratio? Is this an endurance application?

 

on the old setup, the 2.2 (10:1 compression) I had in the car had a pretty crappy torque drop off after 5200 rpm.

I had a decent flowing head and tri-flow style cams (lift numbers were weak however). After doing some research my best theory was the sudden drop off in torque was due to the lousy rod ratio (around 1.54 I believe)

I'm toying with the idea of trying to get more power naturally aspirated, and since the 2.0 has a better rod ratio I figure it will perform better than the 2.2 despite its penalty in displacement.

I'm hoping to optimize things for a longer, flatter torque curve to drive my power up. The biggest draw back of the 2.0 bottom end is the low compression ratio (9.5:1) but I think if I can get a decent figure out of it stock (maybe 160whp+) it'll confirm my belief that despite it being smaller and having a lower compression than the 2.2, it can still make similar torque while having higher power numbers by sacrificing mid range grunt for a high rpm kick in the pants.

Its not very cost-effective, but I'm dying to see a real world example since I'm pretty sure its never been done for my platform before.

 

I doubt your rod ratio is having much effect on torque dropping off after 5200 rpm. What is the bore and stroke of the 2.2 liter?

 

86mm bore, 94mm stroke

 

So you have an engine where the stroke is quite a bit larger than the bore. This engine is not going to rev as high as an engine which has a larger bore than stroke. What is the stock fuel-cut rpm set to on this engine? You have not said what engine this is but I suspect it is one that was built for torque and not horsepower. If you want to rev it higher you are going to need to get more airflow through the head. What do you mean by a 'decent flowing head'? At what lift does flow start to taper off? What is the valve lift provided by your cam? What rpm are you wanting to rev this engine to?

 

keep in mind, that is the OLD engine.

the new one currently in the car is 86mm x 86mm

 

86x86.... 9.5:1CR hrmmmmm is it the old ford cosworth vega motor? i bet don flores knows.

is it the 20R toyota? and it used to be a 22R?



dont be shy, put that **** up here. im curious as to what it is.

if your compression is 9.5:1, i would figure out what cam youre using and how much "leeway" you have til it slaps the piston and mill up to that much from the head to get the compression up, and shrink the combustion chamber up a little. i did that with a P72 (GSR) piston which is a 0cc (flat) piston a long time ago and it worked pretty well for what it was and what i was. (a retard)

 

I'm trying to avoid decking the block, but it is a possibility. I'm still sort of torn as to keep the engine naturally aspirated, or to just say F it and throw a turbo on it.

the bottom end originally should be bolted to a supercharger, so nobody knows what it'll be capable of without forced induction.

the piston has a donut-shaped dish in it with a small crater in the center. My best guess is it tries to focus pressure near the spark plug, or, gives the flame front a bit of extra initially leverage since it'll push into the small crater first, then eventually move to the rest of the combustion chamber. Although none of the piston is proud of the deck.

the car is a 2002 cavalier, and the engine is a hybrid ecotec. The head from a 2.2 L61 ecotec (cavalier engine) and the bottom end and rotating assembly is from a cobalt ss supercharged.. 2.0 LSJ

switching from supercharger to turbo alone the LSJ is capable of 400hp at the wheels, but I'm curious as well as many others as to how it would behave on is own.


another concern I've been pondering is the LSJ comes with oil squirters. I've heard that they help to control detonation, but at the expense of extra windage in the crankcase. Any input on that? I've heard plugging them is a better option for maintaining proper oiling in the crank and rod journals for high rpm.

 

if i were you, i would be looking for an 86mm piston with a somewhat equal pin height and a little more dome.

see what a K20 piston looks like compared to what you have. check the F20C and F22C. those are S2000 pistons. those are 87mm but im sure those sleeves have a mm to spare. youd be the coolest guy ever if you ran an ecotec with oem honda pistons.

also the K24 engines use 87mm pistons. that is the honda element, CRV TSX and accord all newer than 2002 models.

check those out and compare the valve pockets as well.

that reminded me..you remember those lawnboy lawnmowers? they were bright green and 2 stroke. i put a yamaha piston in one when i was 13. ran like a raped ape.

 

what are the compression height of said pistons? I can cross reference to the LSJ piston once I find the actual measurement.

the only thing I could see being an issue is the LSJ has 23mm wristpins.. abnormally thick

 

compression height on all K pistons is 31mm and either a flat top or 4.25 dome except the l20a3 whic has a -2.5 dome

 

K20 pistons have a 30mm compression height, valve reliefs for 35mm intake valve, 30mm Exhaust valve and the pin diameter is 22mm. Not sure of the angle of the valve pockets so that may be another slight problem.

To line hone the wrist pin hole out to 23mm probably wouldn't cost too much. But why bother I'm sure there are already high compression pistons that are made specifically for an ecotec.....

Wiseco has a listing for the GM 2.0 LNF Turbo piston with a 30.85mm compression height, 86mm bore, and a 22mm wrist pin diameter. It also shows the 2.2 & 2.4 with 22mm wrist pins. Is yours an only orphan with 23mm?

 

dimensions I have for the piston pins are different. straight from GM:

piston pin dia.
22.995mm-23.000mm

piston dia.
85.967mm-85.982mm

piston pin bore dia.
23.004mm-23.010mm

intake valves are 35.17mm
exhaust valves are 30.09mm

the 2.4 and 2.2 have 20mm wrist pins

here's my reference.
page 7 of this .pdf file:
GM tuner source


the only thing I need to confirm is the compression height of the LSJ piston.

 

Hmmm maybe aftermarket rods actually shrink the pin size?

 

LSJ has no available aftermarket rods.

everything is a custom deal, they only have pistons available.

stock crank is forged steel, and rods are made out of 5115 steel

 

I see that the LSJ is an odd size and it does have the larger wrist pins. So why don't you just get a set of custom forged pistons with the correct pin offset and the 23mm wrist pin. The offset is noted to be used to keep the pistons quiet during warm up. That sounds a lot like the OEM Honda/Acura K20/K24's. It's all about keeping the engine quiet for the masses....lol

 

i find it amazing that a motor that people are using to cut high 7 second passes has no aftermarket. i mean, really amazing.

dare i say call whitfield racing? they have a 1000+hp cobalt. they might be able to give some advice.

 

the race engines have little in common with the LSJ other than the rod ratio. Blocks are sleeved (not as common in the ecotec world as it is here), sonny bryant crank, carillo rods.. basically a lot of hard to find and very expensive parts.

When I do turbocharge the car I want to basically order the entire GM racing setup (crank rods and pistons) for a block I'm having sleeved with Darton M.I.D. but I want to have a bit of fun before getting serious and try something new (hence the LSJ stripped of its power adder and put under an L61 head.

I'm noticing a lot of conflicting numbers on different aftermarket vendor websites though. I've put the request in to my friend at GM who's going to get me specs straight out of the horse's mouth.

I appreciate all the help and suggestions tho guys. Unfortunately, GM's idea of a "modular" 4 cylinder doesn't include the internals. And believe it or not, aftermarket piston makers don't make higher compression pistons for us.. just flat tops and dish pistons. I could call wiseco and see if they'd make me flat tops for the LSJ.. that'd bump compression up pretty nice, and I wouldn't have to get too fancy with the specs for them (hopefully keeping cost down)

 

From what I see on the net there doesn't seem to be as many sponsored or independent racers doing R&D for a Cobalt as there are Civics and Integras

Ether that or the GM guys aren't as happy to share all the information on forums like the Honda community does. I find it much harder to find specs on-line for domestic cars then it is any Honda/Acura.