'79 GS1000S - 1085 Wiseco Kit - overheats at low speeds

[Fjbj40]

Theoretically the cooling capacity of the engine design, as in the cooling fins, has not changed and therefore should be able to keep the engine cool. However, as I said, the reduced barrel thickness has a reduced convective capacity. This is where the oil comes in, as in gets hotter. Because the cylinder barrel has lost some of its heat transferring ability the heat has to go somewhere. This is where the oil gets hotter, other than lubricating, one of oils most important roles is cooling.

The engine from Suzuki is designed to keep within an acceptable operating temperature. We change the thermal capacity by overboring, hence the reason an oil cooler is required on air cooled engines, IMOP whether stock or modified. Every other air cooled engine I have ever worked on are were
equipped with an oil cooler.

The early Suzuki engines ran hot when pushed hard, I think the bean counters were the reason why they were not equipped with an oil cooler.

[posplayr]

Theoretically the cooling capacity of the engine design, as in the cooling fins, has not changed and therefore should be able to keep the engine cool. However, as I said, the reduced barrel thickness has a reduced convective capacity. This is where the oil comes in, as in gets hotter. Because the cylinder barrel has lost some of its heat transferring ability the heat has to go somewhere. This is where the oil comes in, other than lubricating, one of oils most important roles is cooling.

I agree the cooling effectiveness or Thermal resistance of the convective cooling capacity has not changed but that does nothing to insure it will remain cool. In fact that is exactly my point, more internal heat from higher Hp would necessitate higher operating temp since the convective thermal resistance is unchanged. It just occured to me that the larger cylinder walls and piston skirts will generate more heat just due to friction at the same nominal speed even if the RWHP is the same. While there may be hot spots related to thinner linings, it is the unchanged overall thermal impedance that necessitates a higher operating temp with higher Hp.

[Fjbj40]

I agree the cooling effectiveness or Thermal resistance of the convective cooling capacity has not changed but that does nothing to insure it will remain cool. In fact that is exactly my point, more internal heat from higher Hp would necessitate higher operating temp since the convective thermal resistance is unchanged. It just occured to me that the larger cylinder walls and piston skirts will generate more heat just due to friction at the same nominal speed even if the RWHP is the same. While there may be hot spots related to thinner linings, it is the unchanged overall thermal impedance that necessitates a higher operating temp with higher Hp.

GOOD point about the larger pistons increasing friction/ temperature! The higher HP, compression ratio, increased friction from larger pistons all equate to higher temps.

I would love to be able to get/afford larger sleeves and install in the 1085 to see if it would lower temps? Not really necessary as my oil cooler takes care of it, but just to quantify what I have been told by the Lycoming and Continental engineers about reduced cooling capacity.

[posplayr]

GOOD point about the larger pistons increasing friction/ temperature! The higher HP, compression ratio, increased friction from larger pistons all equate to higher temps.

I would love to be able to get/afford larger sleeves and install in the 1085 to see if it would lower temps? Not really necessary as my oil cooler takes care of it, but just to quantify what I have been told by the Lycoming and Continental engineers about reduced cooling capacity.

I dont know if you are aware, but there are several documented cases of a SERIES R/R reducing oil temperature and presumably engine temperature. Not everybody believes this but in the link you will see those that have seen it by doing it ( I have seen it and Chef as well no I have no doubts). Now Ed tried it on his 8V 1000 and got no improvement.

http://www.thegsresources.com/_forum/showthread.php?161397-Compu-Fire-SERIES-R-R-Install

The only explanation I can come up with is the same one why as to why some people burn up stators and some don't; it has to do with how much heat the bike is generating and how well it can convect the heat away. Similar sized engines will be able to convey heat away similarly, but the smaller engines will run cooler as they have more excess capacity effectively. They don't burn stators as readily.

A 1100E with an 1166 kit definitely runs warmer and it definitely cools off substantially (20-40 degF )running the SERIES R/R. So this all implies that there is in fact a delicate balance of thermal efficiency v.s. heat production and it doesn't take much to tilt it the wrong way.

One other indicator of the same, is that East coast 1100E seem to run cooler that hey do out west. Not sure why except for humidity. I had an office mate with a Phd in thermal/heat flow Mechanical Engineering and he could not endorse such a theory but I don't know what else it could be.

[Fjbj40]

I run a RR off a Goldwing, sh775, it also sits out in the air just above the swingarm on my 1085. It definitely helped with the temps, as you stated.

[Nessism]

I disagree that a series R/R effects oil temp beyond some minimal amount. The only way for the stator to increase oil temp is if the stator itself is hotter than the oil AND coming into contact with the oil. For one thing, the stator only gets minimal splash oil flow. The volume of oil hitting the stator could not possibly heat the entire sump. And in order for the stator to heat the oil at all it would have to be scorching hot. How can this happen when only about 50W of power is getting shorted back to the stator during high rpm riding?

I also disagree that an engine with a big bore kit will automatically run noticeably hotter than a stock engine while cruising. The power demands to push the bike at any given speed are dictated by friction (rolling and internal) and wind drag. It's not like a big bore engine makes more power all the time. It only makes more power when the pilot twists the throttle.

[chuck hahn]

I would think the larger displacement would require larger jets as well to effect as perfect a performing engine as possible. To not rejet would also be a reason for it going lean and overheating...yes????

[IanR]

Adding an 1150 oil cooler (and filter cover) to my stock 1075, dropped temps so much I usually ride with the cooler covered up with cardboard. It still runs much cooler than it did before.

If your jetting is correct, sounds like you need an oil cooler. Doesn't a big-bore make more heat?

Rob, I'd be grateful if you could show me what the oil cooler arrangement is on your bike. I see that for the 1150s the oil lines appear to come off the oil filter cap, which look like they use the same 3 stud arrangement as on my GS1000S. I'd prefer this method to replacing the oil pressure switch plate and bringing the oil lines from behind the engine.

[Nessism]

Rob, I'd be grateful if you could show me what the oil cooler arrangement is on your bike. I see that for the 1150s the oil lines appear to come off the oil filter cap, which look like they use the same 3 stud arrangement as on my GS1000S. I'd prefer this method to replacing the oil pressure switch plate and bringing the oil lines from behind the engine.

The 16V 1100 engine has a different oiling system. For the 8V engines the adapter plate is the proper method.

[posplayr]

I run a RR off a Goldwing, sh775, it also sits out in the air just above the swingarm on my 1085. It definitely helped with the temps, as you stated.

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[posplayr]

The 16V 1100 engine has a different oiling system. For the 8V engines the adapter plate is the proper method.

As Ed said

[John Park]

OK that is a good explanation (even using Bernoulli) but how does it predict a better flowing head needs smaller main jets? Do we need a composite theory?

I never said that better flowing heads need smaller main jets; usually the contrary, unless your 'flow job' didn't do what you'd hoped. Somebody else said that about automotive carbs; I never found that to be the case, but I only work on cars when they're broken….

There are those who increase the size of the hole and expect that more will magically flow through it. It's far more complex than that.

[posplayr]

I never said that better flowing heads need smaller main jets; usually the contrary,

No I don't think you ever said it but it is fact. So my comment relative to jetting is because to be satisfactory it would need to explain the three elements I mentioned, not just #1

1. Increase bored (compression) required increased jetting
2. Improved head flow reduces jetting
3. Increased cams requires increased jetting.

I added compression to #1 because all the street BB kits bump up compression. Again items #1 thru #3 are established fact at least for the 16V 1100's. I'm sure Ray or Blower can corroborate that as well.

[Fjbj40]

I do pay attention to what the senior guys on this forum have to say! I read many posts by you Posplayr, the SH775 advice, SPG, coil relay mods, starter clutch kill switch mod plus many more.

I also used SaltyMonk, Blowerbike, Chef, Rapidray and Tone and many others advice on many things.

People just need to search and read lots, pretty much every problem, mod and repairs are on this forum, just got to SEARCH!

Cheers,
Daryl

[John Park]

Any increase to the surface area of the engine internals will pull more quantity of heat from the process than a lesser area. That's why Subaru, for example, has gone to a smaller bore longer stroke engine recently. Big bore, short stroke engines are less thermally efficient - lose more heat to the head and barrel - than small bore long stroke, because the process is mostly over by the time the rest of the bore is exposed. Subaru had a hard time being competitive on mileage - thermal efficiency - until they went from a rather over square 92 X 67 down to 77 X 83 or whatever it went to.

The increase in surface area will be the square of the difference in diameter.

The thickness of the barrel acts like a flywheel, storing heat and minimizing fluctuations, but the external surface area determines the eventual temperature. In this case, the internal surface has been increased but the outer surface remained the same. Even at the same speed it should run a bit hotter.