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i am building up a nice VVL rwd setup for my other car now and have built my last sr20det using 86.5mm CP pistons 9:1 for big boost
My new setup will be using 90mm bore CP's (larger reliefs, notched for squirters..)with 12:1 and some carillo a rods. I dont want to change the crank, but do want to be able to change the rod length for optimal performace, as i believe it can be changed for the better, seeing ill be using custom pistons anyways.
I would like Big Toe, Miko, and other engine builder's advice on this. changing the pin location, pin size ect.
I will be using another RWD block my spare set of sunny throttles and some undertermined cams, maybe JWT if they ever come out? maybe franklin stg 3? This is a road race engine, which i will have an oil cooler on, and my powerfc d-jetro to run it. I dont have yet the sinlge solunoid or the CAS from the VET and need help finding them. i have ported many sr20 heads and await my VVL engine to come to see how it is.
If you want a longer rod, I think you can go 3-4mm higher wrist pin without needing serious modification. Miko did a thread or post at one time on the rod lenght vs wrist pin.
Honda H22 rods are just about spot on for maximum lenght, I believe from memory there 150 long witch gives you about 25-26mm compresion height on your piston witch is the most that just about everyone will custom make.
If you go higher than this it becomes a one ring deal. NO GOOD.
H22 rods have the same ping and big end size as nissan.
The honda bearing as a silighty differnet size, but it easy to get 10*** under Honda bearings and get the crank ground to suit.
The only hastle you have is the big end is too wide, but its fairly straight foward to machine the rods to the right width, good machine shop should be able to handle it no worries.
You end up with a wider bearing surface on your journal then as an added bonus.
Plus honda rods are everywhere.!!!!
Let me know how you go.
I was thinking of doing this myself but didn't know if the added cost was worth it.
Honda H22 rods are just about spot on for maximum lenght
How much longer at they than the SR20DE rod?
I was considering doing something like this with an 87mm bore. Since you are getting custom pistons they can move the pin up a few mm, the only issue is what rod to run. If you must run a custom rod, that makes it too expensive to be worthwhile. You can move the pin up a lot (8mm or so) and run an SR16 rod. I have heard that the second compression ring must be removed to facilitate this, but I also heard from a piston manufacturer that it can be done with all 3 rings.
The other issue is the strength of the SR16 rod. I would not want to use it with more than 170 lb ft of torque. That definitely rules it out for boosted or big bore applications.
I am curious about this H22 rod. If it works, it might be worthwhile to buy Eagle rods since they will help shave down the weight. Since you are buying the H22 rods, upgrading to the Eagles only costs an extra $300 and includes ARP rod bolts.
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Climate Change skeptics are the new Flat Earth Society
im going to go search some on this myself t find what the real benefit will be from having a longer rod.....more power?? differant powerband??....hmm....
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B.J. Walker
1993 Aztec Red NX2000
1993 White 240sx Hatchback
Pin Size: 0.812"
Finished Small End Bushing Size: 0.813"
Small End Width: 0.929"
Rod Length Centre to Centre: 5.611" (standard rod length is 5.366")
Big End Diameter: 2.0080"
Big End Width: 0.896"
This will allow you to move to a 25.4mm Compression Height retaining the standard JE low-tension ring pack (3 rings) on JE Pistons.
JE already have made these pistons for me but the valve relief centerlines are 43mm as opposed to the SR20 38mm (will not work on a standard head SR). They are cut from the same 86mm stock forgings but are designed, and one set made to 89mm. You can gain a further 3mm by going to a single compression ring. This is not reccomended for street use (single ring).
The cost here is getting a rod made with a 0.813in Pin finished diameter and this length.
This is a rod with 0.245in or 6.22mm longer center to center than the SR20 standard.
Standard SR20: 1.585:1 Rod Ratio
As above: 1.657:1 Rod Ratio
I do not know if the SR16 and 20 share the same compression height pistons so I cannot guess if the SR16 piston and rod combination will fit the SR20 86mm Crank in the SR20 block without protruding the deck.
Lengthening the rod does push the peak torque up in the rev range and narrow the power band width (to a point), however comparing the SR16 to the SR20 on the same bore size and the beloved SR16 cams the dynamics are not much different on the 16 as they are on the 20 with the longer rod, ie: they both make peak power within the same relative rpm bands.
Looking at the post from GTRSentra you can save money and have the piston made to fit the K20 or the 3SGTE Rod length. If you wanted to go to the H22 you would need a smaller pin diameter in the piston and a way lower compression height, at least 22.4mm.
Even here you could save money by just having a good shop re-bush the rod to suit the 0.813in pin for the JE piston.
Do your own maths and the best you can do will be directly related to your back pocket. I would say that any gain in length you can get out of the rod would be a valid gain. "Optimal" as you suggest would cost a rediculous amount of money. Comparing to what's around, again the best you can do is mix and match to suit with the aim being to increase the rod length. What works on will not be the same across the board, the rod length, bore size, runner length, valve sizes, exhaust design etc. all combine for the changes to volumetric efficiency. Thrust face friction will reduce as the rod length goes up (to a point) and within the constraints of the SR20 block will reduce thrust face friction up to the limit of what can fit.
I do not know if the SR16 and 20 share the same compression height pistons so I cannot guess if the SR16 piston and rod combination will fit the SR20 86mm Crank in the SR20 block without protruding the deck.
The SR16 and SR20 engines have the same Compression height. So the SR16 rods can not be used with a stock compression height piston.
Standard SR20: 1.585:1 Rod Ratio
As above: 1.657:1 Rod Ratio
The SR16 has a Rod Ratio of: 1.815:1
If you put the SR16 Rod in an SR20 (86mm stroke) you get a Rod Ratio of 1.634:1.
The SR16 has a rod length of 140.578mm which is only 4.28mm longer than the SR20 Rod. Not 8mm like previously described.
The Stroke on an SR 16 (on exactly 1600cc with an 86mm bore) is 77.437mm.
The Stroke on an SR20 is 86mm.
The difference between them is 8.56mm, however the rod length diference is 1/2 the stroke length difference to retain the deck height. As is the crankshaft "throw" 1/2 that of the Stroke.
Big Toe
Are you positive on the SR16 stroke?
I was under the impression that it has a stroke of 68.9mm (instead of 77.437mm) but I could be wrong as I have not worked on any of these engines!!
Wow, found the error in my spread sheet, had a hard number instead of a cell reference. The 77.43mm came from a crank design I was messing with to have Farandon in England make for me............Oops!
Thanks for pointing out that mistake!!
That now makes for an SR16 Rod Ratio of 2.102:1 based on a 144.846m rod with a stroke of 68.9mm. (8.55mm longer rod than the SR20). Does that sound right. Like you I've not ever played with one...........hell I've never even seen one. 68.9mm stroke makes for 1601cc though, is that what they are?
As said earlier if you drop the second ring and go with the 0.812in Pin you gain enough to run the SR16 rod in the SR20 with a 25.4mm compression height.
I got an e-mail response from Wiseco a while ago stating they can build a custom piston for the H22 rod with a final C/R of 12.0:1 and still use all the rings. This is part of the response I received;
".....We can easily make pistons of that height (25.15mm )using a groove lock spacer (putting the pin up in the oil ring groove and a spacer ring to support the oil ring)..."
Not sure if this groove lock spacer design works or not but I think it was worth mentioning it.
Pito
Last edited by GTRSentra : 11-19-2006 at 11:25 PM.
JE call it an Oil Control Ring "Support Rail". It has a little detent in it to prevent it from rotating. It works well and is proven design on V-8 stuff for about 2 million years now. It's exactly what they did with the ones I have.
Weisco like to have a huge amount of alluminum above the top ring groove. I'm sure they can do better if they re-design the full piston and change the ring pack from the standard offering.
Say that again............
There is no way they can get that so high for a rod that long and keep a ±25mm comp height.
What size pin are they using?
Correct me if I am wrong!!
1. We are calculating using a compression height of 25.15mm.
2. The SR engines have a block height of 211.3mm.
3. H22 connecting rods are 143.15mm long.
4. SR20 stroke is 86mm.
Take the rod lenght and add half the stroke plus the piston compression height and you arrive at 211.3mm!!
For my 25.15 C/H piston with 0 deck height that would be:
Ok, but 32mm - 25.15mm = 6.8mm.
I do not recall there being enough room to move that much up without getting into the 2nd ring land with the standard diameter pin. That's why JE came up with 0.812in. And even with htis they had to shorten up on the stacked height of the ring package.
OK, heres a question, a little off topic but ok. I'm putting together a sr16 motor boosted and i'm tryin to find rods for it. I was thinking that the H22 rods would work but I just want to be sure on what actually has to be machined. Can anyone sum it up really easy?
Use the H22 Rod Bearings and offer them onto the crank, if you have too then mill equally on the sides of the bearing to get them to sit within the radius of the crank journal. If you have to mill them then you will also have chamfer them.
I would just go with good bolts on the OEM SR16 rods. Power would hardly bend a rod like that. Being forced inducion you hardly have to worry about tensile failure. If you stick with the OEM rod then go with a medium eccentricity bearing (ACL, Mougal and Clevite all have them).
Cunningham would make any rod you want as well for the same as you would pay for a set of Crower, Pauter or the like.
The rods I had in mind are the extra length(5.608") Dodge Neon Eagles $300!!. They have Exactly the same big end bore as the sr20 does!(2.008") It is .135" wider (B.E.)which can be machined down at a cost of $60ish. Plus the Pins on these rods are smaller(only 21mm) which will allow for more (.5mm)ring clearance on top. The pistons will be a 90MM custom piston anyways so i dont have to use the nissan(22mm) size on that end. anyways. And the rod is .243" longer or 6.172mm's. The only thing i am concerned with is that these rods can accpet the standard nissan bearing? Or should i use some custom to fit? or machine to fit the nissan bearings?
I believe the H22 v-tec rods are too long at 5.636 and are 6.8mm longer than stock(almost sr16ve!)
The F/H22(no-vtec) rod is a hair shorter(5.580"), but then has the larger pin size, which could cancel out each other. Also the B.E. width is only .069" larger. which could mean this could work easier, and maybe not have to be machined? which is 5.4mm longer which could be ideal, but scat nor eagle makes these, which would make the price too high.
The 3s rod isnt long enough to do this conversion as its only 1mm longer and as the larger B.E. Width The K20 not long enough either. 2.64mm longer
Can anyone here make these pistons for me? Or should i speak with CP pistons direct? i can send them an sr16ve piston and have them figure the rest of this out? As i would need more clearance for larger valves and more lift. Does this look feasable to raise the pin(aka lower the compression height) by 6.172mm's, which is 2.3mm shorter +.5mm(the smaller pin)=2.8mm more usable space for the rings to sit in comparison to the sr16ve rods(which are weak)
This is all to save easily $500 on custom rods as all customs are $850 plus and 2 month wait! ill only have to wait on pistons.
thanks again! For your technical input and advice!
Pete
Ok, but 32mm - 25.15mm = 6.8mm.
I do not recall there being enough room to move that much up without getting into the 2nd ring land with the standard diameter pin. That's why JE came up with 0.812in. And even with htis they had to shorten up on the stacked height of the ring package.
I told them I was going to use the H22 rod and I needed a piston with a C/H of 25.15mm and the above was the response I received. It really doesn't say anything about the pin size but I had already told them I was using the H22 rod.
If they were going to use a smaller pin they forgot to mention it!!
