Longer conrods

Author
Discussion

HedgeyGedgey

Original Poster:

1,281 posts

93 months

Saturday 22nd October 2016
quotequote all
Hi guys, to cut a long story short it's a common thing in the 4g63 evo engines to fit 6mm longer rods with the 6mm shorter pistons from a stroker.I'm having trouble explaining to my dad the advantages, it produces more power and revs out a bit more. Now I know it's to do with the dwell at tdc is changed so you get a cleaner inlet and exhaust stroke, but is there another reason why? He doesn't understand this concept haha. Thanks

Stan Weiss

260 posts

147 months

Saturday 22nd October 2016
quotequote all
I think I have the right bore, stroke, and rod lengths. Look at the difference in piston travel and cylinder volume with a 6 mm longer rod. For one thing you will see a reduction in piston inertia forces with the longer rod.

Stan

Bore_=_85.0_Stroke_=_88.0_Rod_Length_=_150.0
Rotation_Time_of_crank_per_degree_in_Milliseconds0.0256410
Rotation_Time_of_crank_per_rev_in_Milliseconds___9.2307692
Crankshaft_rev's_per_Second______________________108.3333333
Crankshaft_Degrees_at_which_Rod_and_Crank_are_90_Degrees_73.6518

Crank____Piston_____Crank_______Rod____Cylinder_Cylinder
Angle____Travel______Rod_______Bore_____Volume___Volume
Degree_____mm_______Angle______Angle______CI_______cc
-ATDC_
_.0000___.000000__180.00000___0.00000___0.00000__0.00000
1.0000___.008667__178.70668___0.29332___0.00300__0.04918
2.0000___.034664__177.41344___0.58656___0.01200__0.19670
3.0000___.077978__176.12037___0.87963___0.02700__0.44248
4.0000___.138587__174.82754___1.17246___0.04799__0.78641
5.0000___.216462__173.53503___1.46497___0.07496__1.22831
6.0000___.311564__172.24294___1.75706___0.10789__1.76797
7.0000___.423846__170.95133___2.04867___0.14677__2.40511
8.0000___.553253__169.66030___2.33970___0.19158__3.13943
9.0000___.699721__168.36992___2.63008___0.24230__3.97057
_10.0000_.863177__167.08027___2.91973___0.29890__4.89810
_11.00001.043542__165.79144___3.20856___0.36136__5.92158
_12.00001.240725__164.50351___3.49649___0.42964__7.04050
_13.00001.454631__163.21655___3.78345___0.50371__8.25431
_14.00001.685154__161.93066___4.06934___0.58353__9.56241
_15.00001.932180__160.64590___4.35410___0.66907_10.96416
_16.00002.195587__159.36237___4.63763___0.76029_12.45886
_17.00002.475248__158.08013___4.91987___0.85713_14.04580
_18.00002.771023__156.79929___5.20071___0.95955_15.72417
_19.00003.082768__155.51990___5.48010___1.06750_17.49317
_20.00003.410330__154.24206___5.75794___1.18093_19.35193

==============



Bore_=_85.0_Stroke_=_88.0_Rod_Length_=_156.0
Rotation_Time_of_crank_per_degree_in_Milliseconds0.0256410
Rotation_Time_of_crank_per_rev_in_Milliseconds___9.2307692
Crankshaft_rev's_per_Second______________________108.3333333
Crankshaft_Degrees_at_which_Rod_and_Crank_are_90_Degrees_74.2488

Crank____Piston_____Crank_______Rod____Cylinder_Cylinder
Angle____Travel______Rod_______Bore_____Volume___Volume
Degree_____mm_______Angle______Angle______CI_______cc
-ATDC_
_.0000___.000000__180.00000___0.00000___0.00000__0.00000
1.0000___.008591__178.71796___0.28204___0.00298__0.04875
2.0000___.034361__177.43600___0.56400___0.01190__0.19498
3.0000___.077298__176.15420___0.84580___0.02677__0.43863
4.0000___.137379__174.87264___1.12736___0.04757__0.77956
5.0000___.214575__173.59139___1.40861___0.07430__1.21761
6.0000___.308850__172.31054___1.68946___0.10695__1.75257
7.0000___.420156__171.03016___1.96984___0.14549__2.38418
8.0000___.548439__169.75034___2.24966___0.18991__3.11212
9.0000___.693637__168.47114___2.52886___0.24019__3.93605
_10.0000_.855679__167.19266___2.80734___0.29630__4.85555
_11.00001.034485__165.91497___3.08503___0.35822__5.87018
_12.00001.229967__164.63815___3.36185___0.42591__6.97945
_13.00001.442032__163.36227___3.63773___0.49935__8.18281
_14.00001.670574__162.08742___3.91258___0.57849__9.47968
_15.00001.915484__160.81367___4.18633___0.66329_10.86942
_16.00002.176640__159.54110___4.45890___0.75373_12.35135
_17.00002.453917__158.26980___4.73020___0.84974_13.92476
_18.00002.747180__156.99983___5.00017___0.95129_15.58888
_19.00003.056285__155.73128___5.26872___1.05833_17.34290
_20.00003.381083__154.46423___5.53577___1.17080_19.18596

Inline__engine

195 posts

135 months

Sunday 23rd October 2016
quotequote all
fitting longer rods is over hyped alot of the time, if youre looking for a hp or two or are on the ragged edge of durability sure otherwise there is usually lower hanging fruit worth picking first IMO. id rather use the stroker crank and care not about the rod length.

Edited by Inline__engine on Sunday 23 October 02:11


Edited by Inline__engine on Sunday 23 October 07:20

KiaDiseasel

83 posts

90 months

Sunday 23rd October 2016
quotequote all
HedgeyGedgey said:
Hi guys, to cut a long story short it's a common thing in the 4g63 evo engines to fit 6mm longer rods with the 6mm shorter pistons from a stroker.I'm having trouble explaining to my dad the advantages, it produces more power and revs out a bit more. Now I know it's to do with the dwell at tdc is changed so you get a cleaner inlet and exhaust stroke, but is there another reason why? He doesn't understand this concept
That's probably because he's smart enough to know that the primary effect of small changes in rod/stroke ratio is to stimulate the adrenal glands to produce greater quantities of the hormone "gullibullenin" which acts on the wish fulfillment area of the temporal lobe of the brain of people with little actual knowledge of the subject they are expounding on. Gullibullenin increases the perceived correlation between "expectation" and "actual result" hence creating an impression that imaginary effects are real ones. Also known as "Sandy Brown Syndrome" or S-BS for short, this condition is believed to affect as many as 10% of the population. A recent study found that those most affected by Gullibullenin levels in the body also have a particular genetic marker in the 17th chromosome now known as the "I heard it down the pub so it must be true" gene.

Gullibullenin levels in the blood are thought to be responsible for a wide variety of conditions including believing in the efficacy of homeopathic medicine, that innoculations cause autism and that Donald Trump could even run a bath properly let alone a whole country.


Edited by KiaDiseasel on Sunday 23 October 09:50

Steve_D

13,737 posts

257 months

Sunday 23rd October 2016
quotequote all
KiaDiseasel said:
HedgeyGedgey said:
Hi guys, to cut a long story short it's a common thing in the 4g63 evo engines to fit 6mm longer rods with the 6mm shorter pistons from a stroker.I'm having trouble explaining to my dad the advantages, it produces more power and revs out a bit more. Now I know it's to do with the dwell at tdc is changed so you get a cleaner inlet and exhaust stroke, but is there another reason why? He doesn't understand this concept
That's probably because he's smart enough to know that the primary effect of small changes in rod/stroke ratio is to stimulate the adrenal glands to produce greater quantities of the hormone "gullibullenin" which acts on the wish fulfillment area of the temporal lobe of the brain of people with little actual knowledge of the subject they are expounding on. Gullibullenin increases the perceived correlation between "expectation" and "actual result" hence creating an impression that imaginary effects are real ones. Also known as "Sandy Brown Syndrome" or S-BS for short, this condition is believed to affect as many as 10% of the population. A recent study found that those most affected by Gullibullenin levels in the body also have a particular genetic marker in the 17th chromosome now known as the "I heard it down the pub so it must be true" gene.

Gullibullenin levels in the blood are thought to be responsible for a wide variety of conditions including believing in the efficacy of homeopathic medicine, that innoculations cause autism and that Donald Trump could even run a bath properly let alone a whole country.


Edited by KiaDiseasel on Sunday 23 October 09:50
Thank you. It doesn't happen often but that did make me LOL.

Steve

99hjhm

426 posts

185 months

Sunday 23rd October 2016
quotequote all
Wow I had to Google that it was a 85mm bore with 88mm stroke. Do you know what the rod length ratio is to start with?

Inline__engine

195 posts

135 months

Monday 24th October 2016
quotequote all
rods are 150mm so RR is 1.70 to start with

plot the piston displacement and velocity vs crank angle between and the lines will be basically drawn one ontop of each other you would hardly tell with a dial indicator the difference close to TDC as the rocking motion of the piston is substantially greater and thus dwell difference is lost in the error from that.

As an example at 15 degrees ATDC the short rod piston is 0.016 mm further down the hole 1.932 mm vs 1.916 mm

the peak angle changes by something of the order of ~0.5 degree so even the friction is not going be much different

KiaDiseasel

83 posts

90 months

Monday 24th October 2016
quotequote all
Rod stroke ratios in production car engines mainly fall between about 1.55 and 1.80 with an average of around 1.65. A few outliers exist on either side of course although 1.45 is about the bitter minimum. At the opposite end the Jaguar 2.9 straight six has a ratio of 2.34!

Race engine designers have debated for decades over whether there's a perfect ratio. Opinion has tended to come down somewhere around 1.75 to 1.80 but the simple truth is the effects are so small it's almost impossible to measure any definitive differences, even over large changes in ratio. Small changes in induction or exhaust flow or cam duration swamp any real or perceived effects of rod length.

So it's a topic that sensible people don't pay much attention to unless you're working in F1 or similar.

The realities of designing cars means that aerodynamics are paramount and hence bonnet height tends to be pretty much a constant. That gives a certain amount of height the engine can fit into. Long strokes mean less room for correspondingly long rods and taller blocks so they tend to end up with smaller rod stroke ratios than engines with short strokes.

As always though, there's nothing quite so capable of opening people's wallets to no real purpose as a healthy dose of gullibility.

Little Pete

1,513 posts

93 months

Monday 24th October 2016
quotequote all
KiaDiseasel said:
That's probably because he's smart enough to know that the primary effect of small changes in rod/stroke ratio is to stimulate the adrenal glands to produce greater quantities of the hormone "gullibullenin" which acts on the wish fulfillment area of the temporal lobe of the brain of people with little actual knowledge of the subject they are expounding on. Gullibullenin increases the perceived correlation between "expectation" and "actual result" hence creating an impression that imaginary effects are real ones. Also known as "Sandy Brown Syndrome" or S-BS for short, this condition is believed to affect as many as 10% of the population. A recent study found that those most affected by Gullibullenin levels in the body also have a particular genetic marker in the 17th chromosome now known as the "I heard it down the pub so it must be true" gene.

Gullibullenin levels in the blood are thought to be responsible for a wide variety of conditions including believing in the efficacy of homeopathic medicine, that innoculations cause autism and that Donald Trump could even run a bath properly let alone a whole country.


Edited by KiaDiseasel on Sunday 23 October 09:50
Brightened up my Monday morning this has. laugh

dom9

8,040 posts

208 months

Monday 24th October 2016
quotequote all
KD - Never heard SB's name mentioned outside of Peugeot circles... Sounds like there is a story there as I understood he was well respected?!

Perhaps not a discussion on an open forum. As you were smile

PS Interesting topic and responses!

KiaDiseasel

83 posts

90 months

Monday 24th October 2016
quotequote all
dom9 said:
KD - Never heard SB's name mentioned outside of Peugeot circles... Sounds like there is a story there as I understood he was well respected?!
Oh, sorry for the confusion. I was of course referring to the famous jazz clarinettist rather than the Peugeot tuner who believed that big valves don't produce more power than small ones and that every engine he ever builds shows 96 or more ft lbs per litre. smile

dom9

8,040 posts

208 months

Monday 24th October 2016
quotequote all
GLOL wink

KiaDiseasel

83 posts

90 months

Monday 24th October 2016
quotequote all
Little Pete said:
Brightened up my Monday morning this has. laugh
We aim to please smile

KiaDiseasel

83 posts

90 months

Monday 24th October 2016
quotequote all
Inline__engine said:
As an example at 15 degrees ATDC the short rod piston is 0.016 mm further down the hole 1.932 mm vs 1.916 mm
Hmmmm. Exactly correct according to my own calculations. You're clearly not the average bear on here it seems. Not many can do calcs for such complex situations.

Mr2Mike

20,143 posts

254 months

Monday 24th October 2016
quotequote all
KiaDiseasel said:
the Peugeot tuner who believed that big valves don't produce more power than small ones
Above some size he is quite correct.

KiaDiseasel

83 posts

90 months

Tuesday 25th October 2016
quotequote all
KiaDiseasel said:
Inline__engine said:
As an example at 15 degrees ATDC the short rod piston is 0.016 mm further down the hole 1.932 mm vs 1.916 mm
Hmmmm. Exactly correct according to my own calculations. You're clearly not the average bear on here it seems. Not many can do calcs for such complex situations.
Oh oops. Stan Weiss had already posted the numbers. As you were then.

Inline__engine

195 posts

135 months

Tuesday 25th October 2016
quotequote all
i didn't read Stans post though they do agree....i created my own spreadsheet in excel from these equations

https://en.wikipedia.org/wiki/Piston_motion_equati...


Sandy309

2 posts

88 months

Monday 7th November 2016
quotequote all
I've built a variety of similarly spec'd engines with varied rod/stroke ratios and I've not seen any convincing trends on the dynamic properties relating to the "dwell around TDC" and it should be remembered that stress wise, the changes over the top are reflected inversely at the bottom. What I do know however is that the way the engine feels and performs at high RPM are certainly influenced by the changes in piston/rod mass and friction that you get from shorter pistons and longer rod designs.

KiaDiseasel, you write in a familiar manner. Looking back, I think it's over 7 years since I last got into a heated argument with you Dave Baker; I was about to see one of my engines (Fiesta Zetec-SE 1400, not a Peugeot as it happens) win the CCRC Saloon championsip outright with 9/9 class wins that year; the first of five consecutive overall titles for my engines in that series with three different cars/drivers. I've also proudly enjoyed overall wins in the ASWMC sprint and hillclimb championships, winning the MSA British Super1600 Rallycross championship at the first attempt in 2014, coming within 1 points of winning the fiercely contested and punishing BTRDA S1400 at the first attempt too and numerous 2nd and 3rd placed championship results. The ultimate of course has been winning the British Hillclimb Leaders championship 2015 and 2016 with Colin's 205, which holds saloon records at just about every significant hill in the UK now and he put in a stunning debut at the 2016 European Hillclimb Masters recently representing GB, at a venue he'd never seen before, finishing 2nd FWD overall.
I'd hoped the engine you were building Dave Adams, that was supposed to show me how it should be done, would come to fruition, but I gather it was not to be. Any other successes you'd like to share with me over that timeframe?

lowly106

28 posts

182 months

Monday 7th November 2016
quotequote all
Ha...

Haha..

Stan Weiss

260 posts

147 months

Monday 7th November 2016
quotequote all
Sandy309 said:
I've built a variety of similarly spec'd engines with varied rod/stroke ratios and I've not seen any convincing trends on the dynamic properties relating to the "dwell around TDC" and it should be remembered that stress wise, the changes over the top are reflected inversely at the bottom. What I do know however is that the way the engine feels and performs at high RPM are certainly influenced by the changes in piston/rod mass and friction that you get from shorter pistons and longer rod designs.

KiaDiseasel, you write in a familiar manner. Looking back, I think it's over 7 years since I last got into a heated argument with you Dave Baker; I was about to see one of my engines (Fiesta Zetec-SE 1400, not a Peugeot as it happens) win the CCRC Saloon championsip outright with 9/9 class wins that year; the first of five consecutive overall titles for my engines in that series with three different cars/drivers. I've also proudly enjoyed overall wins in the ASWMC sprint and hillclimb championships, winning the MSA British Super1600 Rallycross championship at the first attempt in 2014, coming within 1 points of winning the fiercely contested and punishing BTRDA S1400 at the first attempt too and numerous 2nd and 3rd placed championship results. The ultimate of course has been winning the British Hillclimb Leaders championship 2015 and 2016 with Colin's 205, which holds saloon records at just about every significant hill in the UK now and he put in a stunning debut at the 2016 European Hillclimb Masters recently representing GB, at a venue he'd never seen before, finishing 2nd FWD overall.
I'd hoped the engine you were building Dave Adams, that was supposed to show me how it should be done, would come to fruition, but I gather it was not to be. Any other successes you'd like to share with me over that timeframe?
All I can say is very interesting first post.

Have you ever played around with offset wrist pins or crank center lines in cases where there is limited deck height to work with?

Stan