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Build Complete: HPI RS4 2

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Old 11-13-2018, 06:09 PM
  #16  
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Yet another solid build, and extremely good explanations for problems solved. I wish I still had my Super Nitro RS4 Rally from back in the early oughts. It was shaft drive, but it was fun!
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Old 11-14-2018, 05:41 PM
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Originally Posted by fyrstormer View Post
I pulled the shock towers off a (filthy) donor car. I think it's either GPM or CRC brand. Most of the parts are from donor cars, actually, so I don't know most of the part numbers. The spacers are Schumacher part #2858, though. The pivot-balls are all Tamiya hard steel pivot balls (rather than aluminum, since nitro cars are a lot heavier); I used a mix of their 5x5 hex balls and 5x8 hex balls, with the 5x8's giving some extra length to fit spacers as necessary.
Did you use spacers between the shocks and the shock mounts as well? It looks like you may have, but I can't be sure. If so what size did you use? I had written a large reply the other night, and watched the site save it, but before I could complete my writing my 4 year old son intervened, having woke late I got him back to bed and it had deleted my post. I was tired and slightly annoyed, so I didn't get back to you until today. I'm still experimenting with other cars and brands of front and rear damper stays, as I've noted the newer cars have so much more adjustability. At the moment I am switching out my A901 chassis for the A914, and the upper deck from the RS4 2. I was lucky enough to get an HPI 73910 racing chassis, but as you have pointed out, without having the nicer asphalt to race on here in MO, I'm not going to destroy a piece of art just to play around. I wish they made a different heat sink head for my Nitro Star 15SS. I like the one you have used for the 15FE. Oh, that's the other question I wanted to ask. Were the older Nitro Star 15SS and 18SS engines also made by an airplane engine manufacturer? I wondered, because they seem to purr so nicely in comparison to your description of what the FE sounded like before you made your modifications.

I would be remiss not to comment that your build is very nice and clean. That's actually what caught my eye, THEN I started to look closer, hahaha!
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Old 11-16-2018, 03:22 AM
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There are spacers between the rear A-arms and the rear lower shock mounts, yes. None on the front lower shock mounts.

I think the 15SS and 18SS were also made by Toki, but after examining the insides of an 15SS a couple years ago, it's clear they did more optimization on that design. The 18SS is, I think, just a bored-out 15SS.

If you think the 15FE is bad in stock form, you should check out a 12E at some point. It doesn't even have a bronze connecting rod, it has an iron connecting rod with bronze bushings pressed-in. Talk about overweight and impossible to balance! The 12R SS is in a whole other league compared to the 12E; the 15FE was interesting and satisfying to mod, but I wouldn't waste the effort on the 12E. It looks like a 1970's airplane engine inside.

Last edited by fyrstormer; 11-16-2018 at 05:31 AM.
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Old 11-16-2018, 10:10 AM
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Wow great work. Looks new!
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Old 11-16-2018, 10:38 PM
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Thanks! After all the money I spent on it, it better damn well look new.
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Old 11-17-2018, 01:49 AM
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I just realized I never updated this thread with further improvements I made to the engine:

























That's an 8mph / 17% increase in top speed with no changes to gearing or tire size. That should tell you something about how un-optimized the 15FE is in stock form.

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Old 12-12-2018, 11:19 AM
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what does that engine oil catch do ? saw it listed as optional part. but haven't seen any other nitro engine come with it as either stock or optional. does it catch oil from the engine? but what oil?
thanks
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Old 12-12-2018, 12:21 PM
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Man you should have kept all those junk, sloppy parts instead of throwing them away. Then you could have built a beater, hoopty version lmao! Some worn out tires, an engine that barely runs, even throw a little primer on the body lol. That wouldve been great lol. It would have given you something to bash in your speed bump riddled apartment parking lot. But I am truly impressed with how you meticulously assembled that car out of 5 different chassis. Exceptionally done, I cant say that enough
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Old 12-13-2018, 06:52 PM
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Originally Posted by NSLST View Post
what does that engine oil catch do ? saw it listed as optional part. but haven't seen any other nitro engine come with it as either stock or optional. does it catch oil from the engine? but what oil?
thanks
The crankshafts on most engines step-down in diameter where they pass through the front bearing, so the flywheel collet and the step-down shoulder on the crankshaft pinch either side of the front bearing and form a tight seal. This reduces the amount of oil that seeps out through the front of the engine. The crankshaft on this engine is the same diameter the whole way through, so there is no tight seal at the front. The external oil catch intercepts oil that has seeped out the front of the engine, by catching the oil droplets that would otherwise get flung all over the car by centrifugal force. It's very much a solution to a problem that only exists for this engine. With most other engines, if you have oil being flung all over the car by the flywheel, it means you need to replace the front bearing with one that has better rubber seals.
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Old 12-13-2018, 06:53 PM
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Originally Posted by VoltageDrop View Post
Man you should have kept all those junk, sloppy parts instead of throwing them away. Then you could have built a beater, hoopty version lmao! Some worn out tires, an engine that barely runs, even throw a little primer on the body lol. That wouldve been great lol. It would have given you something to bash in your speed bump riddled apartment parking lot. But I am truly impressed with how you meticulously assembled that car out of 5 different chassis. Exceptionally done, I cant say that enough
Thanks!

I admit I considered building a "beater", but the fact of the matter is I'd eventually start trying to make it work better, and then it wouldn't be a beater anymore. Better to save myself the extra effort and just throw away those stripped-out old parts before I got tempted to build something with them.
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Old 12-19-2018, 08:09 PM
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Hey just got my first rs4 as a nitro project to work on over winter. Looking for a fuel tank replacement. Been searching & see people recommend the “racing” tank but they’re discontinued everywhere . Tx
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Old 12-19-2018, 10:41 PM
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Yeah, they've been discontinued for years. You pretty much have to buy a roller that already has the racing tank installed. The part number is 72525 though, in case you get lucky and find a new one for sale somewhere.
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Old 12-20-2018, 01:00 PM
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Tx, does anyone know of any other 1/10 nitro brands that girl tank will fit?
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Old 12-20-2018, 08:27 PM
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Fyrstormer is the one to listen to when it comes to the rs4.
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Old 12-23-2018, 12:50 AM
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I'm not aware of any other fuel tanks that are a direct fit. The main problem with the stock fuel tank is the primer assembly, which always seems to leak. HPI did a halfassed job fixing this by replacing the rubber O-ring on the filler cap with a foam ring, so excess pressure could leak past the foam ring instead of pushing fuel out through the primer assembly, but that's not really an improvement. There are aftermarket filler caps for the stock fuel tank that have O-rings like all good filler caps should, but then the problem of the primer assembly leaking comes back. If you could remove the primer assembly and plug it without blocking the fuel pickup inside the tank, then that would be a good solution. I never actually figured out how to do that, though, because I managed to buy a couple of the racing tanks while it was still possible to find them.

EDIT: I just saw this auction on eBay for a racing tank: https://www.ebay.com/itm/HPI-Racing-...w/233063255445. 17 hours remaining, as of 3AM EST on 12/23.

ANOTHER EDIT: I just remembered, GPM makes a special top deck for the Nitro RS4 that has a larger space for the fuel tank, and I believe it can fit the extended 100cc fuel tank from the Nitro MT2 truck. The 100cc fuel tank works great, I have one in my Nitro MT2 and a modified one in my T-Maxx.

Last edited by fyrstormer; 12-23-2018 at 01:02 AM.
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