kingscott Posted November 21, 2011 Share Posted November 21, 2011 Hi I have an RB B9 l2g engine fitted in my D8 as per: http://www.speedymodels.com/rb01009-b9---rb-concept-buggy-9-b9-l2g-21-engine-1618-p.asp I'm trying to get a little more acceleration out of the car as it tends to perform quite poorly on pick up/acceleration IMO. The engine is mechanically fine but beings this engine is supposed to be "top of the range" Its bottom end performance is quite frankly very tame indeed. My other D8 short track runs a less expensive GO.21 GX 7R engine but this is much MUCH faster on pick up. I've tried the following obvious changes with no real improvement: LSN tuning New carbon clutch and stronger springs. Fitted a 14t bell (rather than the original 16t I was running). I have not adjusted the HSN yet as I don't believe this will affect my problem, could I be wrong? Don't get me wrong the engine runs sweet as a nut and the top end speed is completely ballistic,however I'm just a little frustrated and disappointed that a 300 quid engine does not have the bottom end grunt I expect from it. I run 25% fuel with a Jammin JP 1 pipe, come to think I may swap this for the RB tuned one on the other engine to see if this changes the performance. The engine does not bog down or hesitate, it just revs up very smoothly and with no drama. I suppose in a way this is a good thing but its just not fast enough out the corners for what I like. Has anyone owned/own one of these engines? what does it perform like for you? Any other ideas why I'm getting this "strange" power delivery? Any ideas help or pointers would be great. Many thanks Quote Link to comment Share on other sites More sharing options...
CHUNKERLUV Posted November 21, 2011 Share Posted November 21, 2011 Only thing I could say is to lean the bottom end right in. Lots of racers run with bottom lean as the car engine doesn't operate in this range much anyway so no worry about heat / lube. If you pinch the fueline about inch from inlet you should aim for cutout in 2secs thats about as much safe punch your going to get...you'll have to close the idle abit. Other than what you've already done I can't help !! JP1 could be changed out for the JP2 its a bit better for bottom to mid. Your right about the HSN it shouldn't affect punch its like a tap and the LSN like the hose nossle if your getting good topend then the taps open bottom end or hose nossle (LSN) needs work. Quote Link to comment Share on other sites More sharing options...
CHUNKERLUV Posted November 21, 2011 Share Posted November 21, 2011 In addition you could also try a heavier centre diff oil...10000wt is about the max in a buggy. That'll even out the drive you may just be losing it through the front wheels as the weight transfers to the rear on take off....sounds like a rocket..lol Quote Link to comment Share on other sites More sharing options...
kingscott Posted November 21, 2011 Author Share Posted November 21, 2011 Hi Yer some interesting points, spesh regards the diff oil. The car runs for around 4 seconds on fuel pinch at the mo, I'm a little hesitant to go much leaner with it even tho like you say most of the work is done mid to top on the track. Funny because the guy I bought this D8 roller from in question (second hand) said the car was set up for "long track"!?! I wonder if he has played with the diff oils in some strange way. The car does not scrabble the front tho, Its just very smooth on pick up. Very strange, Ive not run this RB engine in any other chassis either so I have no comparison unfortunately. I suppose its a 10 min job to swap it all with the other D8 and see what happens. Quote Link to comment Share on other sites More sharing options...
CHUNKERLUV Posted November 21, 2011 Share Posted November 21, 2011 Yere that engine should fire you over a 6-8ft double from a couple of feet away, I had a mate who had bottom end trouble with an RB world series engine and all his troubles dissapeared when he moved from a JP3 to the RB (don't know which one) pipe. But that was in a heavy truggy....it was slow off the mark but uncontrolable once it got on the pipe Try some other folks pipes down the track thats the easiest way of seeing. Quote Link to comment Share on other sites More sharing options...
kingscott Posted November 21, 2011 Author Share Posted November 21, 2011 Ha ha, at the mo I need a 10ft run up! .......and at that point she's going about........120MPH. Joking aside yes like you say the top end is crazy fast, too fast to use! I could quite cheerfully loose lots of the top end speed to get the bottom end punch right. I have an RB pipe fitted to my GO engine and a pit mate has a Picco. Ill swap them over and see what happens. Could be an expensive pipe selection mistake on my part, Thanks for your input mate much appreciated. Quote Link to comment Share on other sites More sharing options...
kingscott Posted November 21, 2011 Author Share Posted November 21, 2011 Out of interest the JP1 manifold is much longer than the RB manifold, however the JP pipe is stubby in comparison. A cut from RB's web page says the following: If you increase the length in between the manifold and pipe, the engine will get better low rpm power(more torque) but you will loose high rpm power(less rpm at full speed). If you decrease the length in between the manifold and pipe, the engine will get better high rpm power(more rpm at full speed) but you will loose low rpm power(less torque). So that sort of goes against the theory at first outside glance, but ill defo swap them over and see what happens. Quote Link to comment Share on other sites More sharing options...
CHUNKERLUV Posted November 21, 2011 Share Posted November 21, 2011 Its all about the convergance and divergence cones its not as simple as length although that is a big factor. Shorter manifold will give better bottom end, longer better top but thats not a generalisation as I said its about the cones. Planes operate long pipes because they are at full throttle most of the time so don't know what rody (RB) was thinking when he wrote that on the website cos to me its the wrong way round...try the RB shorter manifold on the JP3 you may get the good bottom end performance your looking for. Quote Link to comment Share on other sites More sharing options...
martin Posted November 21, 2011 Share Posted November 21, 2011 Its all about the convergance and divergence cones its not as simple as length although that is a big factor. Shorter manifold will give better bottom end, longer better top but thats not a generalisation as I said its about the cones. Planes operate long pipes because they are at full throttle most of the time so don't know what rody (RB) was thinking when he wrote that on the website cos to me its the wrong way round...try the RB shorter manifold on the JP3 you may get the good bottom end performance your looking for. Wrong with 2 stroke engines the key to power is mostly the pipe used, the exhaust gases pulse hundreds off times a second these pulses bounce off the cones inside thus making the waste fuel/oil go back into the engine for lubrication, the longer the manifold is the longer it takes for the gases to escape thus making it have better bottom end but less top end, the shorter manifold the the quicker the gases escape and give it better top end but less bottom end grunt, im afraid you can,t have a pipe that gives you best bottom and top that is impossible, thats why they make jp1 jp2 jp3 jp4 etc to suit different driving styles and tracks, manufacturers now design double and triple cones inside the pipes to try and give and overall decent pipe ie the jp3 and jp4, if your happy that your engine gives you to much high end so it needs more bottom end try a pipe that will calm the top end down and aid the bottom end like a jp1 pipe. marty Quote Link to comment Share on other sites More sharing options...
kingscott Posted November 21, 2011 Author Share Posted November 21, 2011 Hi Marty. Worryingly the engine already has a JP1 Pipe fitted? I've checked Jammin's web site and yes your correct in that they claim the JP1 pipe is good for bottom and mid punch. .................................................. After a bit of research the JP1 pipe should be a good match with my RB B9, the only thing I have not played with is the carb venturi sizes, but Ive always looked at these for race time/fuel usage rather than "tune". I'm sure this is not my issue I'm also going to count the main spur gear's teeth to make sure its not bigger than standard or anything daft. I'm sure the issue will be something silly ive overlooked. My other D8 fitted with the GO gx7r runs a 16t pinion on an RB exhaust, I can't express how much faster it is on pick up in comparison with the B9/JP1 combination, this to me just does not make sense?? Unless I'm underestimating the quality of the GO engine, that may I add I got very cheaply second hand! I for one cant fault it. Quote Link to comment Share on other sites More sharing options...
martin Posted November 21, 2011 Share Posted November 21, 2011 Them go engines even the 3 port Quote Link to comment Share on other sites More sharing options...
kingscott Posted November 21, 2011 Author Share Posted November 21, 2011 100 quid give or take a 5er for the RB exhaust system. ........................................................................ Quote Link to comment Share on other sites More sharing options...
martin Posted November 21, 2011 Share Posted November 21, 2011 Yep i hate having to spend money on stuff that you don't know will do any better, if you have a nice model shop maybe they might let you trail and error with some pipes if they have them in or ask some one on here if they will let you borrow a pipe combo just a thought, if you don't race than an rb is overkill really just a status factor but each to their own, would it be cheaper to sell the rb and get another go that you know is a corker of an engine also the sts .21 and the picco .21 all perform really well, then the funds from your rb go towards the engine and the pipe you have should suit these other engines. The balls in your park mate glad its not in mine lol. Quote Link to comment Share on other sites More sharing options...
kingscott Posted November 21, 2011 Author Share Posted November 21, 2011 Im just getting back into racing hence the part second hand stuff plus the new engine Quote Link to comment Share on other sites More sharing options...
ansmann1 Posted November 21, 2011 Share Posted November 21, 2011 funny you should mention but i hve judt recently bought an rb sport 10 its not quite as expensive as yours. ihave the same problem with mine. i have put it in my ansmann virus 2 as a direct replacement for my force engine. like you say bottom end it just doesnt take off like you imagine it should. however i have an lrpz21r engine in my hyper 7 which is like s*** off a stick in comparison Quote Link to comment Share on other sites More sharing options...
kingscott Posted November 22, 2011 Author Share Posted November 22, 2011 Really? Interesting yet worrying mate! Update: Well I swapped the exhausts today and now I have a very dodgy transmitter/receiver issue with the car.(I dare not drive it as its a power fail not a signal fail) So I cant test until my new receiver arrives in the post. Fab times!!! Quote Link to comment Share on other sites More sharing options...
olixmb4x Posted November 22, 2011 Share Posted November 22, 2011 i would have thought that fitting the smaller clutch bell would have made a big differnce fitting a larger spur gear would give it better low end punch, and changing the clutch springs to something softer/thinner. to be fair though, its all about the engines tuning, because spending loads of money on all fancy bits can be wasted if its not tuned up right. ive had my car feel like a rocket when its tuned by someone who knows what theyre doing (not really me when it comes to engines), so make sure its well tuned Quote Link to comment Share on other sites More sharing options...
kingscott Posted November 23, 2011 Author Share Posted November 23, 2011 Yer my tuning skills are not too bad, I was also surprised at the minimal change in performance from the 16 t to the 14 t. Obviously the top end was slower but the pick up and mid was near as dam the same. I'm suspecting a carb leak at the moment, the cars taking some serious priming on the starter box and its not idling very happy. Ill get there in the end.........somehow!!! I'm pondering on going to 25% fuel rather than the current 20% so either way both of the engines will need a slight adjustment soon. Quote Link to comment Share on other sites More sharing options...
Mr Drifta Posted November 23, 2011 Share Posted November 23, 2011 Sounds mad and i bet you have already but, is your throttle linkage set right ? Maybe a hang up...Just a thought like Shall i get me coat? Quote Link to comment Share on other sites More sharing options...
kingscott Posted November 23, 2011 Author Share Posted November 23, 2011 Sounds mad and i bet you have already but, is your throttle linkage set right ? Maybe a hang up...Just a thought like Shall i get me coat? Yer it's all squilly meter perfect, ive just had the carb off for a quick clean too all looks well. Quote Link to comment Share on other sites More sharing options...
Mr Drifta Posted November 23, 2011 Share Posted November 23, 2011 Yer it's all squilly meter perfect, ive just had the carb off for a quick clean too all looks well. No biscuit for me then Hmmmm...Trouble is how to find low down torque from something that revs at 30+.....when you have no cams to play with, shame these rc charger conversions dont work Quote Link to comment Share on other sites More sharing options...
kingscott Posted November 23, 2011 Author Share Posted November 23, 2011 I might just set the tickover at 15,000 RPM.......Problem solved Quote Link to comment Share on other sites More sharing options...
adesaxo31 Posted November 23, 2011 Share Posted November 23, 2011 Does the d8 have a slipper clutch of it does have you checked its set right atb ade Quote Link to comment Share on other sites More sharing options...
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