Rods lenght
- WhiteFinish
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Rods lenght
How much of compression would I lose if I would take a 5.4" rod in stead of the 5.426" rod ?
I would also use a set of ZE heads.
I would also use a set of ZE heads.
- Ryan
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Re: Rods lenght
I think 0 on the static CR, but dynamically, where the piston achieves max velocity changes, so it would be like changing your cam profile....
But a change that small is insignificant.... but insignificantly decreasing it.
But a change that small is insignificant.... but insignificantly decreasing it.
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- WhiteFinish
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Re: Rods lenght
I doubt it will not change the CR.
Isn't CR depending on the volume of the heads and the position / shape of the piston.
If the rod can't push it 0.026" further up; it means the area where the mixture is compressed is larger.
Isn't CR depending on the volume of the heads and the position / shape of the piston.
If the rod can't push it 0.026" further up; it means the area where the mixture is compressed is larger.
- Inodoro Pereyra
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Re: Rods lenght
Your resulting static CR with ZE heads would be 9.822:1, give or take.WhiteFinish wrote:How much of compression would I lose if I would take a 5.4" rod in stead of the 5.426" rod ?
I would also use a set of ZE heads.
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- Ryan
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Re: Rods lenght
So.... basically 0.
Ze heads are lower CC than DE heads too. Thats probably a bigger difference.
0.56CC difference at TDC with 0.026" shorter rods. <- wrong 3.7CC
ZE heads are 2.5CC smaller.
Ze heads are lower CC than DE heads too. Thats probably a bigger difference.
0.56CC difference at TDC with 0.026" shorter rods. <- wrong 3.7CC
ZE heads are 2.5CC smaller.
Now with Moderator power!
Black '93 BP RS - wrecked, parted, scrapped.
Green GS - Sold.
Black GS - Summer DD/Race car - Fancy KLZE
Red GS - K8-ATX -> MTX-KLDE - Frakencar. Scrapped
White GS - Rusty. Parts. Scrapped
1997 BMW M3 - my summer baby
2002 BMW 325Xi - sold
2003 Forester Xti - EJ20K swapped.
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Black '93 BP RS - wrecked, parted, scrapped.
Green GS - Sold.
Black GS - Summer DD/Race car - Fancy KLZE
Red GS - K8-ATX -> MTX-KLDE - Frakencar. Scrapped
White GS - Rusty. Parts. Scrapped
1997 BMW M3 - my summer baby
2002 BMW 325Xi - sold
2003 Forester Xti - EJ20K swapped.
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Re: Rods lenght
Plane down the heads a little to make up the difference.
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2002 Subaru WRX Blue, SOLD (best E test numbers I've ever seen)
94 MX-6. Sold
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96 GS 5 speed, KLZE, Sold
95 GS Minty Shape Sold
92 GS Sold
92 GS Parts Car scrapped.
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95 GS Minty Shape Sold
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- Inodoro Pereyra
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Re: Rods lenght
Ryan, I think you should check your numbers. The difference of 0.2:1 CR I pointed out is WITH ZE HEADS IN BOTH CASESRyan wrote:So.... basically 0.
Ze heads are lower CC than DE heads too. Thats probably a bigger difference.
0.56CC difference at TDC with 0.026" shorter rods.
ZE heads are 2.5CC smaller.
And, considering the total capacity of each cylinder is 416.166 cc, the difference with the shorter rods is 7.408 cc, not 0.56 cc.
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- Ryan
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Re: Rods lenght
You're right. Hasty and totally wrong.
volume swept by an 8.45cm bore and .06604 cm of stroke is h*pi*r^2 = 3.7035 CC...
DISPLACEMENT of each cyl is 416CC, not the capacity. (you did bore x stroke)
But without knowing full volume at either TDC or BDC, I can't comment on C/R...
since changing from 1:10 to 4:13 is NOT the same increase as from 10:100 to 13:103 even though they both go up 3.
But it will be small.
volume swept by an 8.45cm bore and .06604 cm of stroke is h*pi*r^2 = 3.7035 CC...
DISPLACEMENT of each cyl is 416CC, not the capacity. (you did bore x stroke)
But without knowing full volume at either TDC or BDC, I can't comment on C/R...
since changing from 1:10 to 4:13 is NOT the same increase as from 10:100 to 13:103 even though they both go up 3.
But it will be small.
Now with Moderator power!
Black '93 BP RS - wrecked, parted, scrapped.
Green GS - Sold.
Black GS - Summer DD/Race car - Fancy KLZE
Red GS - K8-ATX -> MTX-KLDE - Frakencar. Scrapped
White GS - Rusty. Parts. Scrapped
1997 BMW M3 - my summer baby
2002 BMW 325Xi - sold
2003 Forester Xti - EJ20K swapped.
Feedback
Black '93 BP RS - wrecked, parted, scrapped.
Green GS - Sold.
Black GS - Summer DD/Race car - Fancy KLZE
Red GS - K8-ATX -> MTX-KLDE - Frakencar. Scrapped
White GS - Rusty. Parts. Scrapped
1997 BMW M3 - my summer baby
2002 BMW 325Xi - sold
2003 Forester Xti - EJ20K swapped.
Feedback
- Inodoro Pereyra
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Re: Rods lenght
You're right.Ryan wrote: volume swept by an 8.45cm bore and .06604 cm of stroke is h*pi*r^2 = 3.7035 CC...
I made a mistake. I doubled the volume, because I confused a shorter rod with a shorter stroke. Actually, the difference in CR would be lower than I stated before, because, even when the piston is stopping .26" earlier at TDC, it's also going down .26" further at BDC, so, without doing the math, I'd guess the final CR would be a little over 9.9:1.
Sorry...
Nope. I actually did 2497/6...Ryan wrote:DISPLACEMENT of each cyl is 416CC, not the capacity. (you did bore x stroke)
![Laughing :lol:](./images/smilies/icon_lol.gif)
![Laughing :lol:](./images/smilies/icon_lol.gif)
Either way, the math is the same.
And yeah, it's the displacement. Sorry for the misnomer.
The volumes could be calculated easily, but I don't think it's worth it.Ryan wrote:But without knowing full volume at either TDC or BDC, I can't comment on C/R...
Bottom line, Whitefinish, using the shorter rods might make you lose 1 or 2 hp at the most.
But, because of the shorter rods, the stroke/rod ratio would go down, which would affect (negatively) your RPM range. At the same time, using the shorter (lighter) rods would call for balancing the rotating assembly. IMO, too much work (and money) to get less hp and a shorter redline than stock...
![Shrug :shrug:](./images/smilies/shrug.gif)
EDIT: You'd lose 0.53 bhp.
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- MrMazda92
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Re: Rods lenght
Go for longer, lighter rods, shorter pistons(from the pin to the block deck, with a tapered skirt to help ease side loading), and rev it to 10K with Colt 218 cams. ![Love :love:](./images/smilies/love.gif)
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'12 Challenger R/T + STP - 3.92 w/ LSD, JG Cam, headers, SkipShift delete, Clutch Delay Valve delete, Hurst STS, RAM Clutch Adjuster, StopTech 6 Piston Brakes, Sticky Nittos, 435 WHP
Kid Hauler:
'08 Suburban LT 4WD - TVS 1900 Blower, LF SC Cam, headers, AFM delete, true 5" lift, 33x12s, 523 WHP
First Love:
'92 GS 5 spd - Straightneck KL/67mm TB, MegaSquirt/Coilpacks, 5 lugs/Speed6 brakes/FD wheels, wiretuck, coilovers, headers, AEM WB, Borla
Deleted: VAF/Power Steering/Air Conditioning/EGR/ABS/Auto Seatbelts/etc
- WhiteFinish
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Re: Rods lenght
Oke, I understand I loose a bit of CR.
Just wondering how much I should raise the piston in order to compensate.
Just wondering how much I should raise the piston in order to compensate.
Why do you come up with this combination ?MrMazda92 wrote:Go for longer, lighter rods, shorter pistons(from the pin to the block deck, with a tapered skirt to help ease side loading), and rev it to 10K with Colt 218 cams.
- MrMazda92
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Re: Rods lenght
The decreased weight allows for significant reduction in Crank weight(below even the KLG4 crank weight), which will do more good than anything for high RPM applications. As it is, it would certainly make the engine rev faster, and if the parts are quality, it could increase the lifespan.
You decrease a LOT of weight by making a smaller piston, and a longer rod. The problem this typically creates is an increase in side loading force against the cylinder wall, for which you'll want a "longer" piston skirt to help distribute that force more evenly. If you taper the skirt so it's longer at 90 degrees and 270 degrees, and shorter at 180 and 360, then you can find a balance between strength and light weight.
Those positions are only an example, my main point was a 4 corner approach to the piston shape, but the angles make it sound more confusing than it is.
I'm not actually sure where the 218 Colt cams top out in the Revs, so that part was kind of a "wouldn't it be nice!" addition. I haven't seen too many people mess with that, none actually, surprisingly.
You decrease a LOT of weight by making a smaller piston, and a longer rod. The problem this typically creates is an increase in side loading force against the cylinder wall, for which you'll want a "longer" piston skirt to help distribute that force more evenly. If you taper the skirt so it's longer at 90 degrees and 270 degrees, and shorter at 180 and 360, then you can find a balance between strength and light weight.
Those positions are only an example, my main point was a 4 corner approach to the piston shape, but the angles make it sound more confusing than it is.
I'm not actually sure where the 218 Colt cams top out in the Revs, so that part was kind of a "wouldn't it be nice!" addition. I haven't seen too many people mess with that, none actually, surprisingly.
Daily:
'12 Challenger R/T + STP - 3.92 w/ LSD, JG Cam, headers, SkipShift delete, Clutch Delay Valve delete, Hurst STS, RAM Clutch Adjuster, StopTech 6 Piston Brakes, Sticky Nittos, 435 WHP
Kid Hauler:
'08 Suburban LT 4WD - TVS 1900 Blower, LF SC Cam, headers, AFM delete, true 5" lift, 33x12s, 523 WHP
First Love:
'92 GS 5 spd - Straightneck KL/67mm TB, MegaSquirt/Coilpacks, 5 lugs/Speed6 brakes/FD wheels, wiretuck, coilovers, headers, AEM WB, Borla
Deleted: VAF/Power Steering/Air Conditioning/EGR/ABS/Auto Seatbelts/etc
'12 Challenger R/T + STP - 3.92 w/ LSD, JG Cam, headers, SkipShift delete, Clutch Delay Valve delete, Hurst STS, RAM Clutch Adjuster, StopTech 6 Piston Brakes, Sticky Nittos, 435 WHP
Kid Hauler:
'08 Suburban LT 4WD - TVS 1900 Blower, LF SC Cam, headers, AFM delete, true 5" lift, 33x12s, 523 WHP
First Love:
'92 GS 5 spd - Straightneck KL/67mm TB, MegaSquirt/Coilpacks, 5 lugs/Speed6 brakes/FD wheels, wiretuck, coilovers, headers, AEM WB, Borla
Deleted: VAF/Power Steering/Air Conditioning/EGR/ABS/Auto Seatbelts/etc
- Ryan
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Re: Rods lenght
WhiteFinish wrote:Oke, I understand I loose a bit of CR.
Just wondering how much I should raise the piston in order to compensate.
Why do you come up with this combination ?MrMazda92 wrote:Go for longer, lighter rods, shorter pistons(from the pin to the block deck, with a tapered skirt to help ease side loading), and rev it to 10K with Colt 218 cams.
0.026" would make it exactly the same.
If you're going with custom pistons, wiseco makes 11.5:1 pistons for us, thats your only real upgrade option as far as I know.
Now with Moderator power!
Black '93 BP RS - wrecked, parted, scrapped.
Green GS - Sold.
Black GS - Summer DD/Race car - Fancy KLZE
Red GS - K8-ATX -> MTX-KLDE - Frakencar. Scrapped
White GS - Rusty. Parts. Scrapped
1997 BMW M3 - my summer baby
2002 BMW 325Xi - sold
2003 Forester Xti - EJ20K swapped.
Feedback
Black '93 BP RS - wrecked, parted, scrapped.
Green GS - Sold.
Black GS - Summer DD/Race car - Fancy KLZE
Red GS - K8-ATX -> MTX-KLDE - Frakencar. Scrapped
White GS - Rusty. Parts. Scrapped
1997 BMW M3 - my summer baby
2002 BMW 325Xi - sold
2003 Forester Xti - EJ20K swapped.
Feedback
Re: Rods lenght
Do you have these rods sitting around? Just wondering why you asked about these in particular.WhiteFinish wrote:How much of compression would I lose if I would take a 5.4" rod in stead of the 5.426" rod ?
I would also use a set of ZE heads.
2004 Subaru WRX Silver, stage 2, minty interior.
2002 Subaru WRX Blue, SOLD (best E test numbers I've ever seen)
94 MX-6. Sold
92 GS KLZE 5 Speed
96 GS 5 speed, KLZE, Sold
95 GS Minty Shape Sold
92 GS Sold
92 GS Parts Car scrapped.
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7477th member.
I know you believe that you understand what you think I said but I'm sure you realize that what you heard is not what I meant.
2002 Subaru WRX Blue, SOLD (best E test numbers I've ever seen)
94 MX-6. Sold
92 GS KLZE 5 Speed
96 GS 5 speed, KLZE, Sold
95 GS Minty Shape Sold
92 GS Sold
92 GS Parts Car scrapped.
Feedback viewtopic.php?f=37&t=66348" onclick="window.open(this.href);return false;
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I know you believe that you understand what you think I said but I'm sure you realize that what you heard is not what I meant.
- MrMazda92
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Re: Rods lenght
He's probably got access to the Ford small block rods that are readily available, and beefier than stock.
IIRC, those were 5.4" exactly, and fit with zero/minimal modification.
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Daily:
'12 Challenger R/T + STP - 3.92 w/ LSD, JG Cam, headers, SkipShift delete, Clutch Delay Valve delete, Hurst STS, RAM Clutch Adjuster, StopTech 6 Piston Brakes, Sticky Nittos, 435 WHP
Kid Hauler:
'08 Suburban LT 4WD - TVS 1900 Blower, LF SC Cam, headers, AFM delete, true 5" lift, 33x12s, 523 WHP
First Love:
'92 GS 5 spd - Straightneck KL/67mm TB, MegaSquirt/Coilpacks, 5 lugs/Speed6 brakes/FD wheels, wiretuck, coilovers, headers, AEM WB, Borla
Deleted: VAF/Power Steering/Air Conditioning/EGR/ABS/Auto Seatbelts/etc
'12 Challenger R/T + STP - 3.92 w/ LSD, JG Cam, headers, SkipShift delete, Clutch Delay Valve delete, Hurst STS, RAM Clutch Adjuster, StopTech 6 Piston Brakes, Sticky Nittos, 435 WHP
Kid Hauler:
'08 Suburban LT 4WD - TVS 1900 Blower, LF SC Cam, headers, AFM delete, true 5" lift, 33x12s, 523 WHP
First Love:
'92 GS 5 spd - Straightneck KL/67mm TB, MegaSquirt/Coilpacks, 5 lugs/Speed6 brakes/FD wheels, wiretuck, coilovers, headers, AEM WB, Borla
Deleted: VAF/Power Steering/Air Conditioning/EGR/ABS/Auto Seatbelts/etc