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  #771  
Old 09-15-2021, 01:06 PM
gasman gasman is online now
 
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"The 6 x 6.00 are the same as used on the -7A. I decided to keep the stock 5x5.00 front tire. "

Are you sure about this? The tires on a stock 7A should be the same as the 6A, 8A, and 9A.
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  #772  
Old 09-15-2021, 04:12 PM
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charosenz charosenz is offline
 
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Quote:
Originally Posted by gasman View Post
"The 6 x 6.00 are the same as used on the -7A. I decided to keep the stock 5x5.00 front tire. "

Are you sure about this? The tires on a stock 7A should be the same as the 6A, 8A, and 9A.
You are right, I said that wrong. I should have said this 6.00 matco set up is the same that is used when switching out the -7A too....

Thanks for catching that!
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  #773  
Old 11-16-2021, 06:17 PM
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Just wanted to provide an update. Basically all is well. The engine and PSRU seem to be running strong. But my nemesis of course is heat. I can see too high of temps (sometimes engine, sometimes inlet air, some times PSRU) in demanding use. I.E. climb-outs on warm days. Or cruise above 35" MAP. But at cruise on "normal" days temps are all good. The high temps on demanding ops are all fixable with some time.

Also one issue that I am beginning to notice is the cowl is creeping up and out at the firewall, which tells me there is not enough outlet for the air trapped in the cowl at higher speeds. I am not surprised by this. I figured this was not ideal and it is something on my radar to improve. I could/should incorporate a high air flow exit for both the intercooler and the cowl. One thought is to incorporate a 3" aluminum 90 degree that would exit the cowl with the opening in a negative pressure area i.e. have the exit facing the rear either at the bottom or the side of the cowl. I suspect this would have a noticeable reduction in cowl air pressure as well as increased flow across the intercooler.

I have sent oil samples to blackstone for both the PSRU and the engine and there is some indication of wear but until I send in several samples for comparison I can't say that there is a whole lot that can be derived from the numbers. One odd note is that there is some fuel noticed in the oil test and that has got me real curious. I do run it rich which might be a cause but at this point it is a mystery.
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Last edited by charosenz : 11-16-2021 at 06:21 PM.
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  #774  
Old 11-19-2021, 06:33 PM
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Piper J3 Piper J3 is offline
 
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Fuel noticed in the oil test - I wonder how common that is? And at what percentages? Timed-EFI with FADEC should prevent raw fuel from washing down cylinder walls. This peaks my interest...
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  #775  
Old 11-19-2021, 07:41 PM
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Quote:
Originally Posted by Piper J3 View Post
Fuel noticed in the oil test - I wonder how common that is? And at what percentages? Timed-EFI with FADEC should prevent raw fuel from washing down cylinder walls. This peaks my interest...
- Me too. I emailed Blackstone back to see if they had any thoughts on the cause but I have not heard back. I think the proof in concern will be if it stays high or of course increases after the next oil change. It was something like 2.2%. The standard so-to-speak is that it should be below 2%. And it was like 0.8% last change....

I plan to do a compression check too when I get some time to tinker....
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  #776  
Old 11-19-2021, 08:13 PM
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Fuel in oil is pretty common. As injectors age they bleed down at shutdown and some raw fuel ends up in the oil. Some cars like my Porsche 996 the fuel leaking out of the injectors when the engine is off will cause dilution of the oil on the lower part of the cylinder and results in bore scoring. Its a horizontally opposed engine.
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  #777  
Old 11-19-2021, 09:01 PM
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charosenz charosenz is offline
 
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Quote:
Originally Posted by rocketbob View Post
Fuel in oil is pretty common. As injectors age they bleed down at shutdown and some raw fuel ends up in the oil. Some cars like my Porsche 996 the fuel leaking out of the injectors when the engine is off will cause dilution of the oil on the lower part of the cylinder and results in bore scoring. Its a horizontally opposed engine.
Rbob,

That is fascinating. I did increase the size of the injectors over stock, due to the increase in long periods of high output ops. Probably a bit bigger than necessary. If the percentage of fuel goes up, and the compression stays in check, I might test new injectors.

I have almost done this anyway as with the new injectors my Air/Fuel Ratio mixture control changes the ratio quicker (with the same amount of rotation of the knob) than with smaller injectors. This is not really bad, but I like ability to have finer changes. But of course new/different injectors would require a reconfigure of the fuel map curve....(might have to dig out some old fuel maps....)

Thanks for the insight.

C
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  #778  
Old 11-24-2021, 06:53 PM
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charosenz charosenz is offline
 
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Default follow up on heat issues

I mentioned in post 773 that I need to relieve what I believe is a build up of air pressure in the cowl at higher speeds. "higher" for me (with my fixed pitch climb prop and 6 in wheels with no leg fairings) means over 150 MPH.

The good news is that I cruised at 5000rpm today at about 28" of MAP and never saw gearbox temps over 210F. That is because it was 50F OAT, unlike most of the summer here what it was 80F plus.

I saw my inlet air temps creep up over 140F when I pushed it past 30" of MAP, so I need to work on my intercooler system. I currently have a terrible outlet flow, so I know that is where I need to do some duct work.

My engine today stayed at 198F on the hot side of the radiator with the cool side staying about 168F. I am good with that. But that is at or close to 30" MAP with an OAT of 50F....

My immediate plan is to add "exhaust" outlet tubes on the bottom of the cowl. (I know what I have now is not sufficient). The plan is to install one 3 inch 90 tube to exit in to negative pressure airstream below the cowl. If that is not enough I will add a second one. I hope to set up a temp air pressure gauge inside the cowl to not only see what the pressure is, but also to see what the results are of the pending outlets. This will be a repurposed MAP gauge.....

I am confident that this will help the IAT, the PSRU temp both....
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Last edited by charosenz : 11-24-2021 at 06:57 PM.
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