Tank set up.

[cbaker65]

I been looking at this tank set up ,an to me ,it may pose issues about how the fuel gets to the carb.!
It also have been known to cause lean out at a 1/4 tank!

1. Look at the tank level with the carb. level.
2. Look at the fuel line set up from carb. to the tank.
3. Look at the pressure line that goes to the tank to the muffler.

My opinion ,all these factors will cause issues of the engine getting enough fuel!
I know of several name brand models that had this problem.

Does anyone else see this an have had the same issue? ,If so ,lets here your opinion about it!

Here is a pic that shows what I am talking about!

 

[Pienk Blitz]

I had the same set up i could not runpast 1/4 tank it strugeld a lot with my tune

Then cbaker65 told me about this so i change a few things and my truck ran way better.

I all so found that my fuel tank filler cap where the nipple goes in was blocked with a small pice of plastic from the factory and that made my tank pressure even lower so this tank set up is somthing i feel is very important. Will see in my next pic i have sortend my tubes and turned my muffler pressure nipple to the top it seemed to help a lot.

 

[olds97_lss]

It should be fine. The pressure from the exhaust pushes fuel to the carb as it empties anyway. The real issues happen when the top of the tank is a different shape than the bottom of the tank, especially if it's fat on top and thin on the bottom. Then the pressure isn't evenly disributed as the tank empties and mucks up the tune. Like the widely known HPI Savage "half tank lean" (HTL) problem.

As it is, 90% of RC's are built like that with half the tank or more below the inlet on the carb.

Out of the 20+ nitro RC's I've had over the years, the only one to ever give me fuel delivery issues was the savage.

 

[olds97_lss]

I don't know if LRP engines exacerbate the problem or what, but for me with the LRP28S3 and LRP30S2, the effect was very bad. Back when I ran an OS21RG in my first savage, the issue was present, but I don't recall it swaying the temps 50F+ from top to bottom like the LRP's do.

With the engine fully broken in and warmed up, I'd fill the tank with the fuel just above the center seam. Then I'd drive it like normal for a few minutes in the grass and adjust tune to keep the temps around 240F. If I ran too long before I got a tune I liked, I'd add more fuel to just above half full and adjust accordingly.

The last time I fought with it, I did so for over a gallon of fuel 2.5 years ago. My thinking was that the last time I tried this before was over 15 years ago and I have learned a bit about tuning since then, so was chalking up my experience then with the HTL issue to my inexperience at the time. However, with the latest attempt, the issue was still present. My temps would range from full tank at 210F and barely running to 1/4 tank at 300F and screaming. I tried raising the tank 3/4" so less of the tank/fuel was below the carb, I tried adding more pressure line, more fuel line, but nothing had any real effect over the massively varying temps from full to empty. So, I tried a brand new HPI tank thinking mine was faulty. Same exact issue. If I tuned it so it was cooler at 1/4 tank down to 260F or so, when I filled the tank, it was so blubbery rich that it would barely move.

Stranger still, the issue with the LRP's was way worse after the engine started to loosen up from break-in, 10+ tanks through. I can only assume it's because I don't putt putt it around as gingerly at that point and I don't have them tuned overly rich at that point like they are during break-in.

The only reason I even retried the HPI tank again was because my old OFNA tank cap spring is shot and the seal is worn out, so it leaked and sucked air really bad making for a poor tune and a mess all over the side of the truck.

When I finally gave up again, the old reliable OFNA tank I had used for years in the past was no longer available as OFNA didn't exist anymore. I was able to find a suitable 125cc buggy tank on ebay with similar dimensions to the old OFNA tank I used. I put my fuel lines back to normal lengths, but the associated pump bulb back in play and threw on the new tank. The tune was way out of whack from the last time I fought with it and the stock tank. Once I got it tuned, I could get a clean burn from idle to WOT and keep the temps at a nice 235-245 running hard in the grass from a full to empty tank. I could do that tank after tank whether I was in the grass or at the skate park. The engine would change so little at the end of the tank that if I didn't pay close attention to it's level, I couldn't hear the difference until the last 15 seconds of fuel or so and it would rev a bit, then die due to an empty tank.

I haven't driven the thing in 18 months. The only footage I have of it is with the current 125cc tank in it and 18/47 gearing, which I changed to 17/47 because the clutch slipped too much in the grass even though the engine could drag it up to speed at a decent rate.

Url for that run

 

[olds97_lss]

I'm not sure who your quoting, but it's not me. I've never had a stock engine in a savage because I've always bought mine used, usually without an engine at all, so I'd put in an engine I had used in my other trucks. So I don't know how the stock engine reacts to the tank or the power output of the stock engines as the HPI had quite a few stock engines over the past 20 years. I don't recall ever saying the LRP out performs an HPI engine. I've only seen an HPI engine run once and that was 15 years ago, I think it was one of the HPI 21's or 25's, a guy I ran into when out running trucks had it in his savage.

I ran 50K in my buggies center diff when I had them, which I haven't had one of for 2 years. I run 500K in my brushless outcast center diff. I run 750K in my savage flux with a center diff. My nitro savage doesn't have a center diff.

I won't run nitro again until next spring, but I'll try what you suggest in the comments on my video or here with my LRP30S2 that I'm running to see if I can get better results then I will also try the stock tank again.

This was from the last time I tried using the stock tank if you would like to comment there, then it's on a thread I created vs derailing this one:
https://www.rctalk.com/forum/threads/got-a-new-engine-for-my-savage-lrp-zr-30.112864/

 

[cbaker65]

Here ,we will just throw one of my lame duck at you then!.....LOL

 

[HPIguy]

On That Pipe I'm not sure why you keep calling out Olds97 in every single thread you've posted the last 24hrs, but this is your warning, keep it civil and not in a call out inflammatory fashion.

 

[Rolex]

Like I said...if you got a problem with any of this, then we can handle it like two nitro-heads. I say my sh*t bangs and your sh*t sucks.
Just know I;m on the hunt right now for frauds like you. Yeah. That part.

I'm backing up HPIguy once again. This will be your last time to insult our members here. You need to NERD up.

My Spidey senses are tingling....AGAIN.

 

[HPIguy]

Confirmed that is indeed Nitro Nerd. And he's banned, again.

 

[Rolex]

Nerd down.