Question about GT35R
Wrong again on all accounts. No forces on the block, hahahhaha.
Anyways rod big end sizes came up. As per manleys catalog:
6 bolt 4g63 - 1.115"
7 bolt DSM 4g63 - 1.038"
B16A 92 up - 0.935"
B18C 94 up - 0.858"
K20 2002 and up - 0.780"
Big end rod bearing width is a pretty big deal. The wider the better and the harder it is for the crank to push through the boundary layer of oil making rod bearing to crank contact.
Even more alarming is the actual size of the K20 rod bearing (diameter) at 2.008" compared to 1.890" big end size shared by the b series AND the 4g63's. A larger big end size means that the surface speed between the crank and bearing at a given rpm is HIGHER for the rod with a bigger big end. Higher surface speeds lead to rpm related failures sooner. So if I were running a K20 motor I'd be running some thick *** oil, some fairly large "loose" clearances, keep the rpm's "conservative" and pray. Actually I'd do a custom crank with B series rods if even possible to get a wider rod bearing and smaller diameter big end to reduce surface speeds allowing both higher rod forces AND higher rpm's.
It looks to me like honda was trying to "narrow up" the K20 to fit a smaller package and in the process had to make compromises. The extremely wide rods in the 4g63 (specifically the 6 bolt) are a true testament of the motors outstanding design and durability for INTENDED TURBO USE!
Finally, anybody around racing motors (road racing, drag racing, street motors) knows that rod bearing failures are the most common problems. You can not spend enough time on this part of the motors design.
Anyways rod big end sizes came up. As per manleys catalog:
6 bolt 4g63 - 1.115"
7 bolt DSM 4g63 - 1.038"
B16A 92 up - 0.935"
B18C 94 up - 0.858"
K20 2002 and up - 0.780"
Big end rod bearing width is a pretty big deal. The wider the better and the harder it is for the crank to push through the boundary layer of oil making rod bearing to crank contact.
Even more alarming is the actual size of the K20 rod bearing (diameter) at 2.008" compared to 1.890" big end size shared by the b series AND the 4g63's. A larger big end size means that the surface speed between the crank and bearing at a given rpm is HIGHER for the rod with a bigger big end. Higher surface speeds lead to rpm related failures sooner. So if I were running a K20 motor I'd be running some thick *** oil, some fairly large "loose" clearances, keep the rpm's "conservative" and pray. Actually I'd do a custom crank with B series rods if even possible to get a wider rod bearing and smaller diameter big end to reduce surface speeds allowing both higher rod forces AND higher rpm's.
It looks to me like honda was trying to "narrow up" the K20 to fit a smaller package and in the process had to make compromises. The extremely wide rods in the 4g63 (specifically the 6 bolt) are a true testament of the motors outstanding design and durability for INTENDED TURBO USE!
Finally, anybody around racing motors (road racing, drag racing, street motors) knows that rod bearing failures are the most common problems. You can not spend enough time on this part of the motors design.
Another thing that must be considered when you are talking about con rod stress is bob weight. The weight of the piston/wrist pin, con rod about the rotating mass of the crank shaft. All of these engines are vastly different in these aspects and thus clearances and widths are hard to discuss when only looking at one aspect and not the whole picture.
CJ
Rod stroke ratio:
B16 – 1.74
4G63 – 1.705
K20 – 1.616
B18 -1.581
The B16 pushes into the OPEN DECK sleeves the least. The 4g63 is pushing into its CLOSED DECK iron block design just a little harder. I don’t see your argument. A higher rod/stroke ratio promotes higher RPM’s due to less cylinder sidewall loading. This is an important aspect to consider on open deck motors like Hondas.
Rod/Stroke ratio has nothing to do with the fact that the surface speed on a bigger rod bearing is higher for a given rpm. One rotation of the crank is one rotation of the rod journal. A bigger rod/stroke ratio will alleviate some of the angles and forces but the K20 has a SMALLER rod/stroke ratio than most of these motors. Honda motors are "tall" by comparison to most motors of the same displacement because of the height of the VTEC head. Its like trying to stuff a b16 in a CRX, you need a hood with more clearance because the b16 is taller than the d16a6 they came with. Honda is compromising on the bottom end rod length to keep the motor package less "tall" just like they did by narrowing the rod bearings. Doesn't the K20 come with "coated" bearings? I think we can now see why it needs them!
Your fighting semantics at this point with bob weight.
B16 – 1.74
4G63 – 1.705
K20 – 1.616
B18 -1.581
The B16 pushes into the OPEN DECK sleeves the least. The 4g63 is pushing into its CLOSED DECK iron block design just a little harder. I don’t see your argument. A higher rod/stroke ratio promotes higher RPM’s due to less cylinder sidewall loading. This is an important aspect to consider on open deck motors like Hondas.
Rod/Stroke ratio has nothing to do with the fact that the surface speed on a bigger rod bearing is higher for a given rpm. One rotation of the crank is one rotation of the rod journal. A bigger rod/stroke ratio will alleviate some of the angles and forces but the K20 has a SMALLER rod/stroke ratio than most of these motors. Honda motors are "tall" by comparison to most motors of the same displacement because of the height of the VTEC head. Its like trying to stuff a b16 in a CRX, you need a hood with more clearance because the b16 is taller than the d16a6 they came with. Honda is compromising on the bottom end rod length to keep the motor package less "tall" just like they did by narrowing the rod bearings. Doesn't the K20 come with "coated" bearings? I think we can now see why it needs them!
Your fighting semantics at this point with bob weight.
Rod stroke ratio:
B16 – 1.74
4G63 – 1.705
K20 – 1.616
B18 -1.581
The B16 pushes into the OPEN DECK sleeves the least. The 4g63 is pushing into its CLOSED DECK iron block design just a little harder. I don’t see your argument. A higher rod/stroke ratio promotes higher RPM’s due to less cylinder sidewall loading. This is an important aspect to consider on open deck motors like Hondas.
Rod/Stroke ratio has nothing to do with the fact that the surface speed on a bigger rod bearing is higher for a given rpm. One rotation of the crank is one rotation of the rod journal. A bigger rod/stroke ratio will alleviate some of the angles and forces but the K20 has a SMALLER rod/stroke ratio than most of these motors. Honda motors are "tall" by comparison to most motors of the same displacement because of the height of the VTEC head. Its like trying to stuff a b16 in a CRX, you need a hood with more clearance because the b16 is taller than the d16a6 they came with. Honda is compromising on the bottom end rod length to keep the motor package less "tall" just like they did by narrowing the rod bearings. Doesn't the K20 come with "coated" bearings? I think we can now see why it needs them!
Your fighting semantics at this point with bob weight.
B16 – 1.74
4G63 – 1.705
K20 – 1.616
B18 -1.581
The B16 pushes into the OPEN DECK sleeves the least. The 4g63 is pushing into its CLOSED DECK iron block design just a little harder. I don’t see your argument. A higher rod/stroke ratio promotes higher RPM’s due to less cylinder sidewall loading. This is an important aspect to consider on open deck motors like Hondas.
Rod/Stroke ratio has nothing to do with the fact that the surface speed on a bigger rod bearing is higher for a given rpm. One rotation of the crank is one rotation of the rod journal. A bigger rod/stroke ratio will alleviate some of the angles and forces but the K20 has a SMALLER rod/stroke ratio than most of these motors. Honda motors are "tall" by comparison to most motors of the same displacement because of the height of the VTEC head. Its like trying to stuff a b16 in a CRX, you need a hood with more clearance because the b16 is taller than the d16a6 they came with. Honda is compromising on the bottom end rod length to keep the motor package less "tall" just like they did by narrowing the rod bearings. Doesn't the K20 come with "coated" bearings? I think we can now see why it needs them!
Your fighting semantics at this point with bob weight.
If the crank stroke is higher, the big end size surface speeds will be slower. You are correct in saying that one revolution of the crank is still on revolution of the big end, but the speeds are different when you consider crank stroke. Now, factor bob weight and rod ratio of these engines and you can see that piston acceleration from one engine to the next and the g forces involved will be vastly different, thus warranting different big end bore sizes and bearing widths.
I rest my case.
CJ
End even on paper you can only "see" so much. The real world tells the tale (which I tried to elude to a few pages back). Rau 199mph in a Pro RWD car no nitrous. Shepard 191 mph in an AWD all steel unibody car. Buschur going nearly 175 in a shoebox for aerodynamics Evo.
I'm not going to sit back and let people tell me that the "honda head" or the "honda bottom" end is so much superior to a motor with the real world accomplishments of the 4g63 series of motors.
I'm not going to sit back and let people tell me that the "honda head" or the "honda bottom" end is so much superior to a motor with the real world accomplishments of the 4g63 series of motors.
Thank you dan l. Finally some numbers, I couldnt find them anywhere. You have just proved what I have been stressing all along. And if you throw the s2000 the rodstroke ratio is something like 1.8x which is why it has the ability to rev so high without breaking a sweat. I know piston speed also plays a part, but so does side load and the less side load the better for reving, proven. I honestly do not see anything that makes the
K20 > 4g63. iron block(4g) vs aluminum block(k20), mivec(4g) vs ivtec(k20), head flow very close, strongest 4 cylinder ever made(4g) vs smallest rod journals ever made (k20), one comes in an awd vehicle, the other comes in a 2wheelerpeeler lol. No but really dan l your numbers pretty much put the nail in the coffin. Thanks.
K20 > 4g63. iron block(4g) vs aluminum block(k20), mivec(4g) vs ivtec(k20), head flow very close, strongest 4 cylinder ever made(4g) vs smallest rod journals ever made (k20), one comes in an awd vehicle, the other comes in a 2wheelerpeeler lol. No but really dan l your numbers pretty much put the nail in the coffin. Thanks.
End even on paper you can only "see" so much. The real world tells the tale (which I tried to elude to a few pages back). Rau 199mph in a Pro RWD car no nitrous. Shepard 191 mph in an AWD all steel unibody car. Buschur going nearly 175 in a shoebox for aerodynamics Evo.
I'm not going to sit back and let people tell me that the "honda head" or the "honda bottom" end is so much superior to a motor with the real world accomplishments of the 4g63 series of motors.
I'm not going to sit back and let people tell me that the "honda head" or the "honda bottom" end is so much superior to a motor with the real world accomplishments of the 4g63 series of motors.
As for the superiority of one head vs. another, that's easy enough to resolve with a flowbench (at least flow potential anyway).
As to which is 'superior' to the other overall, I feel the answer to that question depends heavily on the context. At a glance, I'd say Honda (e.g. S2000) appears to be designed primarily for strong high rpm efficiency, light weight, low friction, in normally aspirated configuration. In that arena, it excels, and I doubt anyone will argue. Meanwhile, the 4G63 would appear to be by design, better suited to take a general beating with a turbo in front of it, and this is probably not by accident.
And finally, as for discussing Hondas, et al in this forum, I see no issue with it whatsoever so long as it's done for comparative and/or educational purposes. Many good ideas and discussions arise from opening one's eyes and ears to other platforms.
Flow bench numbers mean about as much to me as dyno hp figures. When we start racing flow bench numbers at the track I'll start worrying about those figures. Static flow bench numbers do not do justice to a dynamic fluid such as air. If you think bottom end geometry is dynamic in nature (realistically it can be modeled fairly easily) then the dynamic properties of a fluid reacting to a valve opening and air entering the cylinder will absolutely blow your mind to pieces. We haven't even gotten to the exhaust stroke where we have to add thermodynamic properties of the expanding gasses.
A sturdier platform simply puts 'great accomplishments' more easily within reach. Nevertheless, I'm unaware of top EVOs (e.g. 900-1000+whp) using 'many stock OEM parts' - not critical ones anyway.
Flow bench numbers are about as useful as dyno figures, and both are useful enough to make reasonably accurate predictions. I've had enough calculus and exposure to fluid dynamics to be well aware of the complications of real-world modeling, but that doesn't negate the fact that just about anyone can tell a diamond from a turd without having to resort to 'blowing their mind to pieces'.
Flow bench numbers are about as useful as dyno figures, and both are useful enough to make reasonably accurate predictions. I've had enough calculus and exposure to fluid dynamics to be well aware of the complications of real-world modeling, but that doesn't negate the fact that just about anyone can tell a diamond from a turd without having to resort to 'blowing their mind to pieces'.
All very good points. The thing that is different and has been for years with the dsm's is numbers and money. For small amounts of money you can take dsms into the 11's and lower. Honda's will get there, but you need more duckets. Dan nice 1g, i know many people who have tried to blow up a 6bolt and just couldn't do it. The 4g63 does take a lot of punishment, hopefully the new X engine will do the same.
A sturdier platform simply puts 'great accomplishments' more easily within reach. Nevertheless, I'm unaware of top EVOs (e.g. 900-1000+whp) using 'many stock OEM parts' - not critical ones anyway.
Flow bench numbers are about as useful as dyno figures, and both are useful enough to make reasonably accurate predictions. I've had enough calculus and exposure to fluid dynamics to be well aware of the complications of real-world modeling, but that doesn't negate the fact that just about anyone can tell a diamond from a turd without having to resort to 'blowing their mind to pieces'.
Flow bench numbers are about as useful as dyno figures, and both are useful enough to make reasonably accurate predictions. I've had enough calculus and exposure to fluid dynamics to be well aware of the complications of real-world modeling, but that doesn't negate the fact that just about anyone can tell a diamond from a turd without having to resort to 'blowing their mind to pieces'.
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