2.4LR Evo 9 93oct Virtual Dyno Results
May 25, 2018, 07:32 PM
#47
Actually, the better rod ratio reduces the wear (better angle). Do you have measurement between rop and bottom rings and between center of wrist pin and bottom ring?
Last edited by 2006EvoIXer; May 25, 2018 at 07:50 PM.
May 25, 2018, 09:53 PM
#48
Yes, better rod ratio, but at cost of more wear of cylinder walls. I'll need to run through the calcs to see how much tradeoff is here. Maybe it's minimal?
Actually, the better rod ratio reduces the wear (better angle). Do you have measurement between rop and bottom rings and between center of wrist pin and bottom ring?
Actually, the better rod ratio reduces the wear (better angle). Do you have measurement between rop and bottom rings and between center of wrist pin and bottom ring?
but thats ok when it is time to freshen it up I will prob end up doing the 156 in the future.
May 26, 2018, 12:13 AM
#49
If anyone knows how far apart the top/bottom rings are and bottom ring/wrist pin for these 156mm and 150mm pistons, I can run calculations to get a better idea of the trade-offs.
May 26, 2018, 05:13 PM
#51
Evolved Member
Sorry Cursedsm, I was probably thinking of someone else please forgive me, my bad.
like EvoIXer said piston speed is the big issue, longer rod reduces peak piston speeds and is the way to go for a high rpm engine.
like EvoIXer said piston speed is the big issue, longer rod reduces peak piston speeds and is the way to go for a high rpm engine.
May 26, 2018, 06:24 PM
#52
Longer rods reduces the angle the wrist pins turn. It reduces the push outward on crank. Tradeoff is the wrist pin is up against the bottom ring. So distance between the top and bottom rings are usually shortened. Problem with shortened rings is the bottom ring will see more pressure as power stroke occurs (to stay going up/down and resist pivoting). Use a borescope and look at cross hatch along the back of each cylinder to see when you need to hone again. Take pictures when new and every 10k miles to get an idea of your wear.
Last edited by 2006EvoIXer; May 26, 2018 at 07:25 PM.
May 27, 2018, 01:15 AM
#53
Evolving Member
Thread Starter
Sorry, I did not measure this distance before I put them in. From what I saw, between 2.3 and 2.4LR the better rod ratio from the rod gives you the ability to rev a lil higher than 4G63block and less wear. I am still debating on how much rpms are ''safe'' for this build. At the moment I rev it only 7,300 because of the stock turbo. However later on, I am thinking a dual map. One with wastegate pressure and 7.000limit and another map which would be the kill mode and rev it to 8.500. As I said earlier I liked the idea of having a motor which would be torquier than 2.0 but without having to sacrifice the top end. With this build I think I can do both. Probably another build which could be even better is the 2.2 with a 94mm crank and easily rev it to 9.000. But I think 1.5liter more displacement for the 500rpm difference is well worth it. And also as Aaron stated the 2.4lr feels more balanced and somewhat smoothier than the 4g63 2.3.
What troubles me at the moment is the possible backpressure which the car will have with this large engine. The 1.15a/r T4 Divided will keep the backpressure in control but the exhaust won't. Although I have a 3'' turbo-back exhaust, the muffler I have is an HKS Hi-Power Silent (I like to hear the engine lol). The inlet diameter of the muffler is only 50mm so 99% I will have backpressure with this muffler.
But I thought a couple of solutions. The first one is a wastegate cutout installed in the downpipe so it can release the gases before even reach the muffler. And the other one is the same but with a throttle. Throttle will open without the car coming to boost, something which I don't like, but the wastegate will open with pressure, so in travelling at low speeds the car will be more 'civilised'.
Anywhow, one step at a time
When the car will be ready we will deal with this also
What troubles me at the moment is the possible backpressure which the car will have with this large engine. The 1.15a/r T4 Divided will keep the backpressure in control but the exhaust won't. Although I have a 3'' turbo-back exhaust, the muffler I have is an HKS Hi-Power Silent (I like to hear the engine lol). The inlet diameter of the muffler is only 50mm so 99% I will have backpressure with this muffler.
But I thought a couple of solutions. The first one is a wastegate cutout installed in the downpipe so it can release the gases before even reach the muffler. And the other one is the same but with a throttle. Throttle will open without the car coming to boost, something which I don't like, but the wastegate will open with pressure, so in travelling at low speeds the car will be more 'civilised'.
Anywhow, one step at a time
When the car will be ready we will deal with this also
Last edited by ConEvo; Nov 22, 2018 at 03:06 AM.
May 27, 2018, 03:43 AM
#54
I thought about piston speed some more and, as it turns out, it doesn't matter which block the piston is in. 
I read that we should avoid going over 26 m/s because of oiling problems.
26 m/s × 60 s/min × 1,000 mm/m ÷ 100 mm/0.5 rev = 7,800 rev/min.
Destroking to 94mm crank would have given you 8,300 RPM redline using the same formula.
The 4G64 will always be torquier than the 4G63 because of an extra 6mm. Yes, the most common way to reduce back pressure is to use an O2 dump. Or dump both and you will really hear the engine
If you use O2 dump, I suggest dumping to ground and not through hood vent for 2 reasons. 1) rain and carwashing can fill your pipe with water and corrode pipe. And 2), most A/C "Fresh" air is pulling outside air through vents in front of windshield. With up pointing O2 dump, you will get "Fresh" exhaust gases from your engine.
And it is an increase of 0.15 liter (not 1.5L).
I read that we should avoid going over 26 m/s because of oiling problems.
26 m/s × 60 s/min × 1,000 mm/m ÷ 100 mm/0.5 rev = 7,800 rev/min.
Destroking to 94mm crank would have given you 8,300 RPM redline using the same formula.
The 4G64 will always be torquier than the 4G63 because of an extra 6mm. Yes, the most common way to reduce back pressure is to use an O2 dump. Or dump both and you will really hear the engine
If you use O2 dump, I suggest dumping to ground and not through hood vent for 2 reasons. 1) rain and carwashing can fill your pipe with water and corrode pipe. And 2), most A/C "Fresh" air is pulling outside air through vents in front of windshield. With up pointing O2 dump, you will get "Fresh" exhaust gases from your engine.
And it is an increase of 0.15 liter (not 1.5L).
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ConEvo (May 31, 2018)
May 31, 2018, 12:31 AM
#57
Evolving Member
Thread Starter
Jun 1, 2018, 05:43 AM
#59
Evolved Member
EvoXier,
piston speed is non linear due to rod angle, the formula your using doesn’t take into account rod angle. Higher rod angles cause the piston to accelerate/decelerate faster at certain crankshaft degrees. Also there’s less dwell time at TDC, this makes a short rod motor less efficient at high rpm. Long Rods are critical for high rpm efficiency, you won’t find any high rpm late model race motors running short rod to stroke ratios for many reasons, Cylinder filling, TDC dwell time, piston speed, cylinder/skirt side loading, just to name a few.
IMO any stroker motor should be a long rod, Benifits of lower ring lands just don’t outweigh the Benifits of a longer rod.
Also run a 1mm top ring in conjunction with a 1.2mm second ring, the thin rings will drastically reduce ring flutter at higher RPM. Also radial gas ports on anything over 35 psi boost pressure is a good idea. Vertical gas porting is a bad idea with a street driven car, they will plug with carbon fairly quick.
piston speed is non linear due to rod angle, the formula your using doesn’t take into account rod angle. Higher rod angles cause the piston to accelerate/decelerate faster at certain crankshaft degrees. Also there’s less dwell time at TDC, this makes a short rod motor less efficient at high rpm. Long Rods are critical for high rpm efficiency, you won’t find any high rpm late model race motors running short rod to stroke ratios for many reasons, Cylinder filling, TDC dwell time, piston speed, cylinder/skirt side loading, just to name a few.
IMO any stroker motor should be a long rod, Benifits of lower ring lands just don’t outweigh the Benifits of a longer rod.
Also run a 1mm top ring in conjunction with a 1.2mm second ring, the thin rings will drastically reduce ring flutter at higher RPM. Also radial gas ports on anything over 35 psi boost pressure is a good idea. Vertical gas porting is a bad idea with a street driven car, they will plug with carbon fairly quick.
Jun 1, 2018, 12:50 PM
#60
EvoXier,
piston speed is non linear due to rod angle, the formula your using doesn’t take into account rod angle. Higher rod angles cause the piston to accelerate/decelerate faster at certain crankshaft degrees. Also there’s less dwell time at TDC, this makes a short rod motor less efficient at high rpm. Long Rods are critical for high rpm efficiency, you won’t find any high rpm late model race motors running short rod to stroke ratios for many reasons, Cylinder filling, TDC dwell time, piston speed, cylinder/skirt side loading, just to name a few.
IMO any stroker motor should be a long rod, Benifits of lower ring lands just don’t outweigh the Benifits of a longer rod.
Also run a 1mm top ring in conjunction with a 1.2mm second ring, the thin rings will drastically reduce ring flutter at higher RPM. Also radial gas ports on anything over 35 psi boost pressure is a good idea. Vertical gas porting is a bad idea with a street driven car, they will plug with carbon fairly quick.
piston speed is non linear due to rod angle, the formula your using doesn’t take into account rod angle. Higher rod angles cause the piston to accelerate/decelerate faster at certain crankshaft degrees. Also there’s less dwell time at TDC, this makes a short rod motor less efficient at high rpm. Long Rods are critical for high rpm efficiency, you won’t find any high rpm late model race motors running short rod to stroke ratios for many reasons, Cylinder filling, TDC dwell time, piston speed, cylinder/skirt side loading, just to name a few.
IMO any stroker motor should be a long rod, Benifits of lower ring lands just don’t outweigh the Benifits of a longer rod.
Also run a 1mm top ring in conjunction with a 1.2mm second ring, the thin rings will drastically reduce ring flutter at higher RPM. Also radial gas ports on anything over 35 psi boost pressure is a good idea. Vertical gas porting is a bad idea with a street driven car, they will plug with carbon fairly quick.
2winscroll, you're correct about piston acceleration/deceleration speeds varies as rods turn around the crank. My thinking was simplified and was average speed thinking. With long rods, the acceleration/deceleration from TDC to mid cylinder is less drastic than shorter rods. I'll need to find a way to calculate the advantages and disadvantages to see if tradeoff is worth the risk and cost differences.
I'll need to recalculate 26 m/s piston speed vs RPM. This will reduce rev limit for each crankshaft. Lol
Last edited by 2006EvoIXer; Jun 1, 2018 at 12:58 PM.