Quote:
Originally Posted by AN
Yeah, for proof of concept, you should keep things as simple as possible .. also, if you over-complicate your goals ... you might loose interest (I hope not).
Direct drive would be ideal, I hope the LM5 motor from e-cycle comes through at a reasonable price point ... step up gearing at the rpm involved adds a lot of break-points/cost/ mass / maintenance... If this challenge is handled electrically, in the long run it will have a lot of benefits. However, if you ARE leaning towards getting a centrifugal SC for now, I see a few used Vortechs in the $600 ~ $1000 range on eBay. I even see a Rotrex for $900.
I do not have very good understanding of compressor maps ... (I am a EE major, working in IT :| ) .. should I be looking for a compressor which moves a lot of CFM at relatively low rpms and PRs ? Any resource you can point me to ... that will get me reading ?
Also, In your opinion, whats the easiest way to get a usable digital or analog signal for TPS and RPM ? w/o the use of expensive electronics? Is the throttle sensor a 1~5V signal on these / other modern cars ? RPMs would be pulses I imagine.
One more observation I have from Fenton's thread is that after adding additional (smaller 2x 9Ah) batteries to the 2x 18Ah batteries, they are seeing higher boost levels (0.5 psi) through out. This indicates that the ability to flow current at peak demand is definitely a bottleneck here and the Caps should help with that a lot.
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I do love the simplicity of a direct drive system, but it has the drawback that we're looking at speeds that really reach the upper limit of what these hobby brushless motors are capable of. One thing I noticed in my testing is the motors heat up quickly when pushed to the limit.
The reason I think fitting an electric motor to an off the shelf centrfegual super charger is that:
1. I'm not going to be able to build a better transmission myself
2. In addition to the step up gearing, the compressor wheels/housings are designed to produce more boost at slower speeds then a similar sized turbo.
The Phantom setup is actually a custom machined turbo housing to fit a larger compressor wheel from what I understand. Check YouTube for videos explaining compressor maps there are several out there.
TPS signals are 0-5V so easy enough to read with any micro controller. My thought for RPM is to detect the pulses going to one of the spark plugs and then have a micro controller read that. The FA20 engine uses a plug on coil setup so I'm not sure what the signaling voltage triggering the coil looks like but I'm sure it could be figured out. Some people had mentioned reading it off the OBD port but the data there has some lag due to the CAN bus refresh rate. Plus That sort of interface design is a bit beyond my programming skills.
I have no doubt that current is a bottle neck. It will be interesting to see how much caps would help. They are best at handling short spikes in current so it's going to take some very large caps to help for more then just quick bursts.
Keep the ideas coming. I love getting other peoples thoughts and brainstorming.