| Oil-Coolers for GSX1100
engines...
I bought my '81 Kat1100 with a substantial oil-cooler already installed. However, by comparing the temperature of the hoses to and from the cooler after a long run, there didn't seem to be much temp. difference between the two, and so I wondered if the cooler was functioning properly. So I put my question about this on the Forum at Katana Central -- and I got a lot of helpful advice and so I was able to make some sense of the situation. At the same time, I did a fair bit of trawling across the Internet and came across other advice that I have now come to see as being of 'varied' quality. Right, enough prattle. My conclusions are as follows: Part One In un-modified form, the situation with a GSX1100 engine before you attach an oil-cooler, is shown in Figure 1. All of the oil from the oil pump enters the filter housing directly, and passes through the filter to the rest of the engine. And the blanking plugs just sit there, BEGGING you to install an oil-cooler. They are very hard to ignore, aren't they. Figure
1: As far as I can tell, there is a fair bit of misinformation floating around out there, that more or less states that if you install an oil-cooler without blocking off the relevant oil way using (i) a purpose-made plug, or (ii) an 'EFE' oil-filter cover, then you will surely cook the cylinder head. There was even an old bike magazine article I came across in my travels, that declared that there were cooked GSX-1100 heads propping open garage doors all over England, because people had failed to redirect the oil when they installed an oil-cooler! I now think that all this is plain wrong. As one correspondent on the Katana Central forum pointed out, even if the relevant plug or filter cover is not installed there can be no loss in oil pressure because it is a closed system (see Figure 2). Figure
2: In real terms, all that will happen if no plug or EFE fitler cover is installed, is that the oil flow will be shared between the path to the oil filter, and the path to the oil-cooler. But because the oil-cooler feeds back into the filter recess anyway, there is no pressure-loss or reduction of oil volume flowing through the system overall. This verdict is backed up by the fact that my bike had its oil-cooler installed for years before I bought it, without the afore-mentioned plug or EFE filter cover, and there was no sign at all of over-heating cam journals and the many other dire consequences the prophets of doom have been crowing on about. None whatsoever. So here is my first conclusion: if you don't block off the relevant oil way with a plug or an EFE filter cover, there will be no damage. HOWEVER... however, in my travels I have come to understand that a plug or EFE filter cover is still a mighty good idea! Why do I think this? Read on... Part Two What we need to do, I think, is understand just what the 'EFE' filter cover is designed to achieve. As the pictures below make clear (courtesy of 'Katman'), the EFE filter cover -- which was made by Suzuki for their GSX-engined machines which came with an oil-cooler fitted as standard -- has an extra 'baffle' cast on the inside, right where the oil is pumped into the filter housing from the engine.
Now it is important to realise that this 'baffle' is not there to block the oil flow into the filter housing -- it is only designed to restrict it. Some of the oil being pumped from the engine can still make its way directly into the filter housing, as there is a restricted gap by virtue of the 'baffle', but -- importantly -- more oil is now redirected through the oil-cooler. (See Figure 3.) Figure
3: Which is exactly what the people at Suzuki wanted to achieve, I guess. For there is no point having an oil-cooler if you're only going to get minimal oil-flow through it. But at the same time, it appears that the folk at Suzuki didn't want to have the oil from engine pumped EXCLUSIVELY through the oil-cooler -- hence the baffle on the inside of the filter cover. Now it's a bit hard to imagine why things have been designed this way. One reason might be, I suspect, for safety's sake. I mean, if all your oil is being pumped through the oil-cooler and it blocks up with gunk or sludge, then you could end up with a seized engine as all the oil paths to the engine have been blocked. But then again, we must keep in mind that there is a by-pass valve incorporated in the oil-system's design, so that (for example) if the oil-filter is hopelessly blocked, then the valve is opened so that the engine doesn't starve of oil. And in the event of a blocked oil-cooler, the same valve would perform the same function. OK then, here's another explanation: perhaps it was a compromise situation so that bikes sold to colder climates (eg. northern Europe and North America) wouldn't get too much cooling happening. Who knows. Until some knowledgeable boffin comes along to enlighten us all, all we can do is speculate as to why the EFE cover aims to redirect most, but not all, of the oil through the cooler. The main question is, what does all this mean for fitting an oil-cooler to our GSX-engined machines?
Part Three What it means is, unless you can think of a good reason to route ALL of the oil through the cooler, probably the safest bet is to install an EFE filter cover. It's the way Suzuki designed it, and it's probably the better way to go for that reason (although not everything designed by Suzuki is good!). But if you fit a plug into the relevant oil-way instead of getting an EFE filter cover (as per Figure 4 below), then your oil-cooler will work, and not just sit there looking pretty. And as long as your oil-cooler maintains good flow and doesn't get gunked up, this setup should be fine. With modern oils and regular oil-changes, sludge build-up simply shouldn't be an issue. Figure
4: Now if you can't get your mits on an EFE filter cover, but you have a plug, then one thing you could do to emulate the partial restriction of the filter cover (if you so wish) is simply drill a hole up the centre of the plug. Now, not having an actual EFE filter cover in my paws, the following calculations are an estimate based upon scaled measurements from Katman's pictures above. Assuming that the semi-circular slot through the baffle of the EFE cover is about 3.25 mm across (and if someone in possession of an actual EFE cover can confirm this measurement, that would be great), it works out that to achieve the same cross-sectional area for a circular hole, you would would need a 2.29mm hole drilled up the centre of your plug. (Of course, no one sells 2.29mm drill bits, but a 2.3mm bit should be readily obtainable.) For those of you who would like to know, the formula I came up with and used in my calculation is...
... where d2 is the diameter of a semicircle, and d1 is the diameter of the hole you'll need to drill to achieve the same cross-sectional area (and thus -- in this case -- corresponding oil volume delivery). So, 3.25mm divided by the squareroot of 2 delivers 2.29mm. But don't take my word for it; I had to dust off some basic school-boy maths for that! By all means, dust off your own and see how you go. And if in the course of time we find out that my initial estimate of 3.25mm isn't quite right, well, just plug the correct figure into the formula and take things from there. Wrapping Things Up This brings you to the end of my thinking on GSX1100 oil-cooler matters. Of course I am more than happy to be corrected on any of the information and ideas I have presented here, as like you I just want an engine that works, and works well. Because the GSX1100 engine is undoubtedly the most excellent engine ever made for anything (although that 24 litre, 12 cylinder lump in the Napier-Railton must come close). And finally, it's my turn to put in a predictable caveat: all of the information here is for you to weigh up and use AT YOUR OWN RISK. I make no claims to being a 'guru' -- there are enough of these boorish types out there in cyberspace as it is. All I have tried to do is think through things logically and clearly. You be the judge. So, want to give me some feedback, or set me straight on something? Or pass on some comments or tips? Email me at:
Happy biking, Mike.
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