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Engine Decisions - FI Choices Airflow vs AvStar

motodave

Well Known Member
I've done the searches and still not conclusive.

I'm about to order a Thunderbolt engine from Van's (before the annual price increase) and one of the choices is for the FI between Airflow Performance vs AvStar. I'm planning on a YIO-360-M1B with dual e-Mags and welcome any insight on the FI differences. I also plan to use a James cowl and extended hub Hartzell (M2YR) so if any experience on the FI interference fit I would appreciate that also.

Thanks!
 
I don't have any hard data ... I have a M1B with the AvStar servo, which is working well. However, I haven't been able to get any reasonable manuals for my PN .. I'm cribbing on the older RSA-5 manuals when needed.

AFP, though, has great manuals and support. I had to switch out a grumpy Andair fuel pump for an AFP model, and loved the extensive documentation. I'm sure that the servo docs are solid ... and the live person help is just about legendary here on VAF. That would close the deal for me if I had to make the choice (which wasn't an option for my engine)
 
I've had 2 engines with AFP, product and company is top notch.
I think the Avstar's idle better but the AFP flows more at WOT.
 
Does anybody know which model AFP comes with the Thunderbolt if you select that option? One of them has a different intake flange that requires modification of the snorkel, but I just looked on their website and the FM-150 sure looks a lot like a bendix mounting flange.
 
AFP idle

I've had 2 engines with AFP, product and company is top notch.
I think the Avstar's idle better but the AFP flows more at WOT.
I had the same problem. I added an airflow straightener in my snorkel just before the servo, and now mine idles smoothly down to about 650 RPM. It was a dramatic difference.

https://vansairforce.com/community/showthread.php?p=1455416

BTW, every time I call Airflow Performance they pick up the phone, and I get to talk to the top guru there, Don. He answers all my dumb questions, and then I usually find out later that the answer was in the manual. Outstanding support.
 
I had the same problem. I added an airflow straightener in my snorkel just before the servo, and now mine idles smoothly down to about 650 RPM. It was a dramatic difference.

https://vansairforce.com/community/showthread.php?p=1455416

BTW, every time I call Airflow Performance they pick up the phone, and I get to talk to the top guru there, Don. He answers all my dumb questions, and then I usually find out later that the answer was in the manual. Outstanding support.

I would love to try something like what you shown on my FM150 to see the results and a friends FM100 that has a serious idle problem.
I have a vertical induction which I don't think is as bad as the snorkels.
 

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Crutch

I would love to try something like what you shown on my FM150 to see the results and a friends FM100 that has a serious idle problem.
I have a vertical induction which I don't think is as bad as the snorkels.
The airflow straightener is a crutch - the right solution is to do as DanH suggested in the other thread - make the intake better. It seems that Don from AFP worked with Van's on the RV-14 snorkel to improve it using his flow bench - I might look at that one when it becomes available, or try to fix it as DanH suggested, or longer term, create a 3d printed snorkel which is "perfect". Another option is to change from a snorkel to a straight intake like DanH has.

Very limited time right now and I want to finish my flight testing before I take on a complex project.
 
Thanks all for the insight on AFP versus AvStar. I won't have the snorkel with James cowl, it's a straight shot from intake to throttle body hopefully the idle is fine for either. Was/is concerned about any potential interference with the cowl if anyone use a James cowl?

It sounds like the support on the AFP is much better and likely leaning that way... I don't need to try and reverse engineer anymore than I do already!
 
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