For those of you playing along at home, you may remember the poor state of the original fans in our 1991 Toyota MR2 Turbo that we discovered when installing a Mishimoto radiator.
While we reinstalled those old fans at the moment in order to get the car back in service, we also placed an order for the matching Mishimoto …
Pretty skinny fans on a shroud that's very close to the core. How do they do pulling through multiple heat exchangers? That's the usual downfall of slim fans with no torque.
In reply to Keith Tanner :
Lots more aluminum involved with this setup aiding heat exchange. These new fans have to be better than the OEMs, especially with the extra sealing. Maybe we look at the overall system rather than one segment of it.
That Corbin clamp on your upper hose is hurting, but I don't blame you for leaving it alone. There's a hundred ways to lose knuckle skin on this job.
When I have to remove that clamp, I typically disconnect the hard pipe brackets and pull it back into the frunk to work on it. I once bought an MR2 Turbo that someone had installed silicone hoses on, which I replaced with durable, reliable OE hoses.
Jerry From LA said:In reply to Keith Tanner :
Lots more aluminum involved with this setup aiding heat exchange. These new fans have to be better than the OEMs, especially with the extra sealing. Maybe we look at the overall system rather than one segment of it.
What aluminum? In the shroud? That doesn't help. Note that I've been involved in actual instrumented dyno testing under controlled conditions, so I have a bit of insight into what makes fans work.
These new fans do NOT have to be better than the OEMs. I don't bash non-FM products as a rule, but I make an exception for the Mishimoto fans for the Miata because they are terrible. The slimline motors have no torque to pull through multiple heat exchangers and the shrouds are far too close to the core, which means the fans really only pull through about 50% of the core surface area. Looking at this application, I see the same.
The fan manufacturer should be able to tell you how the fans perform not just in free air, but also when there's a pressure gradient involved. Slim, low torque motors will fail in the latter application, but unfortunately it's where fans actually really come in to play. You need big beefy motors that suck a lot of juice. Coincidentally, that's what most OEM fan motors look like.
The shroud has to be far enough away from the core to allow air to move sideways. The closer it is, the less airflow you have through the core that's not directly under the fan. We want to see at least an inch and preferably more. GRM states that these fans don't use all the space available. I would be willing to wager that proper testing would show that adding spacers under the shroud stand-offs to move the shroud further away from the core and use up some of that unused space would improve the cooling ability of the car. Again, you'll notice that OEMs do this. They also have the abililty to shape the shroud to direct airflow, which is not possible with the folded sheet metal shrouds usually found on aftermarket setups.
Sealing to the core - I've mentioned that. But again, look at the OEMs. They're pretty well sealed.
What part of the overall system did I miss here?
Maybe when this car's cooling system is struggling next summer GRM will try to space that shroud off the core. It's the easiest fix to try. Swapping in some stronger fans would be a second choice. Since these fans were most likely donated to GRM by Mishimoto in exchange for editorial (hey, it's what makes project cars possible), the former experiment would likely be more palatable to all involved.
Long term testing I guess will be the decider. We have some space at the bottom to offset the shroud, but almost none at the top. But worst case, should we find that the flowthrough isn't sufficient, it's conceivable we could offset teh lower part of the shroud and create a higher volume low pressure area between the core and the fans.
Cool. It may make for some interesting articles, honestly. Like radiator design, there's a lot of bad assumptions out there about fans. If you want, I could probably dig up some numbers from our testing. We had an engine that could run under a set load as a heat generator and a radiator in a box with multiple fan setups tested. We tested time-to-temperature and drop across the core. Not easy to do in the car, but it's pretty useful data.
If you're constrained at the top, that is going to make things more challenging. Going with a wedge will probably help. Where does the air go afterwards, do you have any aerodynamic assist to help out?
Here's an example of the effects of motor torque. The only difference between the orange and grey traces is the size of the motor on one of the fans. Obviously both of them are dwarfed by the two blue traces, but you can see how the grey setup consistently outperforms the orange. It would be a lot more obvious if we scaled the graph from 0-1800 CFM :)
The blue traces? Massive brushless motors that are a pain to package and have huge power feeds. These are the ratings from the manufacturer, shroud design is not taken into account.
Tyler H (Forum Supporter) said:That Corbin clamp on your upper hose is hurting, but I don't blame you for leaving it alone. There's a hundred ways to lose knuckle skin on this job.
When I have to remove that clamp, I typically disconnect the hard pipe brackets and pull it back into the frunk to work on it. I once bought an MR2 Turbo that someone had installed silicone hoses on, which I replaced with durable, reliable OE hoses.
When I did the rad, one of my plans was to replace them wth the proper OEM spring clamps, which I have a big box of that I've collected over the years.
Except... I couldn't find ones that fit. And as I was working—as I frequently am—at like 1am, I just put the old clamps back on because they had nice grooves already and I know they worked.
Of course, when I was putting tools away I found—wait for it—the OTHER box of Toyota clamps with the proper size. They sit. Waiting. Just in case.
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