I agree with you on the port timing has alot to do with the power gain on these long rod motors,or even a stroker motor,no arguments here,everyone,or engine builder has his own beliefs,on what or will make more preformance,but if you talk to the guys over at oniel bros they will agree if your running a 4wd car like a losi,the 30.5 is better for the torque factor then the long rod.like we were saying everyone has there own opions,no offense taken.
Long Rod...
- Thread starter dwarfy
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46u
Well-Known Member
I cannot dispute that as all I have right now is a 2 wheel drive. In my situation I am just hoping I can hang on to it but would love to have a 4 wheel drive and Lord will maybe one day. Never talked to Sean about this but will the next time I talk to him. I all so agree about port timing even on a stroker motor and is why a machined cylinder is much better then one built with stacked or thicker gasket.
Thanks for the cool conversation.
Thanks for the cool conversation.
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i agree with you guys!, the 7.5hp is higher in the rev range,and in reality doesn't mean much, as you know it probably only hits above 7hp for a few hundred revs,and over 6hp for maybe 1 or 2 thousand revs.the proof is definatly in the performance of the engine/buggy! my mate has a 26cc in his mcd,i think he will definatly go the 30.5cc way as it takes more torque to get it rolling due to more mechanical drag. i have the 27.2 long rod,but am not seeing its full potential which is down to the track pipe im using,but it is very smooth,like i said its that smooth in power delivery ,i didnt realise how fast it picked up its pace and top end untill i raced someone.its so much more graceful in the hormann in comparison to the huge thump of power the jetpro gives from mid upwards ,the pipes definatly have a say in how the power is delivered.
The problem is most people hear ohh 7.5hp but littile do they realize that if the porting on the motor or stroke size isnt right,and they run 4wd then that 7.5 is really useless,because your getting most of that power in the mid and high compared to the low,and a littlie mid were 4wd needs it most to get rolling,defantley when your going around the track you are hardley useing the high ,your constantley slowing down asnd picking up speed.
mooman007uk
Well-Known Member
i've been perusing all the torque and hp figures for my foff jeep (i'm after the best torque figures...as whit don't take the figures literally but for comparisons sake they're a great tool) and here's what i found....highest torque and hp is obr 27.2 long rod...beats the 30.5 and 29.5.. max torque is at 15000 where the 30.5 long rod is 500 rpm lower. the 27.2 also makes more at 10K which is where you want lots of ooomph especially if running a 9.5k spring (this is running a vrc propipe which was designed in conjunction with the 27.2 full mod so is maybe why the 27.2 has better figures)
the long rods make more torque earlier and more total than a regular full mod, they also rev higher and pick up off idle quicker so all round a better motor...
I'm running just a full mod 27.2 in my 4wd 37lb pyrad and it's plenty of motor for it, a race port 27.2 in the toxyc which is again more than enough.
In the old 2 bolt days the 30.5 made more torque than anything else without a doubt but our engines in the last year or so have evolved to the next level with the 4 bolt zen and now long rods...as a comparison the best hp 30.5 2 years ago was 5.0hp and now it's 7.0hp, torque follows the same pattern so that's a 40% increase in power!!!
I'm going to talk to Sean at obr about a motor for the jeep and see what he suggests; at the moment i'm thinking 27.2 LR full mod but now waiting to see what the new 4wd motor/losi figures are
the long rods make more torque earlier and more total than a regular full mod, they also rev higher and pick up off idle quicker so all round a better motor...
I'm running just a full mod 27.2 in my 4wd 37lb pyrad and it's plenty of motor for it, a race port 27.2 in the toxyc which is again more than enough.
In the old 2 bolt days the 30.5 made more torque than anything else without a doubt but our engines in the last year or so have evolved to the next level with the 4 bolt zen and now long rods...as a comparison the best hp 30.5 2 years ago was 5.0hp and now it's 7.0hp, torque follows the same pattern so that's a 40% increase in power!!!
I'm going to talk to Sean at obr about a motor for the jeep and see what he suggests; at the moment i'm thinking 27.2 LR full mod but now waiting to see what the new 4wd motor/losi figures are
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I hear ya but im going from what Oniel bros and i talked about,and from expirence,i have a long rod motor and 3 30.5full mods,and a 28.5 fullmod for price wise and power wise,i would rather have the 30.5full mod,I was going to order the 27.2longrod from oniel bros just to have my motor guy throw it on his dyno to see what it actually puts out hp wise,and run it in my Losi if it really puts out what they say,but after talking to them at oneil bros,they said i probally would be disapointed running it in the Losi and said i would probally be better of running the 30.5 fullmod,cause the long rod was desighned for more hp in the mid to high range,so if they would steer me away from spending more money on a long rod and go with a 30.5 full mod,then im probally going to listen just from running what i have and talking to them,but everyone has there opionens,thats why i don't pay much att. to hp specs on a dyno,don't get me wrong there nice to see or get a idea of what a motor will do,but in my opionen thats it,if you want the facts you need to run it,or see it ran.
46u
Well-Known Member
I talked to Sean today at OBR and he indeed said he did not recommend the long rod for any 4 wheel drive do to lack of bottom end. So I for one stand corrected. 
Just wish I could afford a 4 wheel drive and from what I have been reading from the end users the Lois is the way to go.
Just wish I could afford a 4 wheel drive and from what I have been reading from the end users the Lois is the way to go.
46u
Well-Known Member
I am 57 years old and I am still learning. I am sure you will agree you can not beleive everything you read on the forums. Sorry whittron I do not know you from Adam. But I have not problem to admit when I am wrong. Now I would like to know why the long rod robs low end. All is good and thanks.
motorman
Well-Known Member
porting of the longrod is important. actually though, the longrod give better performance in both areas, revs and torque. the key to a longrod is porting for a lower power band(torque) but the mechanical advantage of the reduced rod angle lets the engine rev a bit more. its not like it will rev to the moon over a convetional length rod but it does give improvement. i build my own motors and ive tested all variables. ive ported longrods for rpm, same as if i were using standard rod and the longrod was a little softer on the bottom but did seem to rev hard. then, ported for more torque and this is where the LR shined. it offers more torque, better response, and will rev more. this is in comparison to same porting, only changing between a standard length rod and a longer rod. and, imo the 5mm rod seems better to me than the 3mm longer rod. all my testing in performance is in the field feel of the engine/car. i do not have a dyno to confirm this on paper. i do not think it is necessary, mainly as said above. a dyno is useful for a serious builder selling to the public so he can compare porting in a controlled invironement with a baseline to work from.
mooman007uk
Well-Known Member
whit you are crazy
but also right, the new 4wd motor from obr is a reg rod 30.5...regardless of the figures the peak power and torque come at 13300rpm, so with a 9500 spring it'll be on the pipe pretty much instantly.
only reason i can think it produces more torque over a long rod is because the LR has less of an angle to the crank so it produces slightly less leverage which in turn makes it harder to spin up, the stroker crank with the pin 2mm further from centre and a short rod gives the most attainable leverage.
but also right, the new 4wd motor from obr is a reg rod 30.5...regardless of the figures the peak power and torque come at 13300rpm, so with a 9500 spring it'll be on the pipe pretty much instantly.only reason i can think it produces more torque over a long rod is because the LR has less of an angle to the crank so it produces slightly less leverage which in turn makes it harder to spin up, the stroker crank with the pin 2mm further from centre and a short rod gives the most attainable leverage.
motorman
Well-Known Member
a 2mm stroker cranks' rod boss is only 1mm further out from center. the 2mm is arrived at by an extra 1mm up stroke and an extra 1mm down stroke added together to be a 2mm stoker.
there is something to the rod angle and leverage but i think the mechanical freedom of the engine given by the longer rod can out weigh the leverage you are refering to when going with a standard length rod.
im saying if they wanted that amount of torque from the longrod at that rpm they could easily achieve it with the longrod version of thier 30.5 aswell.
there is something to the rod angle and leverage but i think the mechanical freedom of the engine given by the longer rod can out weigh the leverage you are refering to when going with a standard length rod.
im saying if they wanted that amount of torque from the longrod at that rpm they could easily achieve it with the longrod version of thier 30.5 aswell.
mooman007uk
Well-Known Member
oops, my bad on the crank.
need help
Hey Whittron ,I'm in MICHAN and looking for a place to have my 30.5 dyno and tune
yh longrods not best for 4wd but great in 2wd like fg, even now alot of people are moving to longrod motors.
ive seen 4wd mcds with 27.2 to 30 5cc, didnt see a huge difference tho'. and pipe choice will still have a big say in the matter.
alot of people are keeping their stock 26cc motors in their losi 5ts, I guess it comes down to what your into.
just got myself a reed engine for my next (heavy) project...
ive seen 4wd mcds with 27.2 to 30 5cc, didnt see a huge difference tho'. and pipe choice will still have a big say in the matter.
alot of people are keeping their stock 26cc motors in their losi 5ts, I guess it comes down to what your into.
just got myself a reed engine for my next (heavy) project...
Trebor
Well-Known Member
mooman007uk
Well-Known Member
the long rods spin up a bit faster a rev higher but produce less torque..my 4wd rigs have either full mods or race ports...the obr 30.5 full mod losi motor is a torque monster and still revs high, i run one in my mk1 foff jeep and it screams, hits the pipe early and stays there, pipe is vrc pro, the pros were originally designed on the obr 27.2 full mod engine using timing and port size to calculate the pipe dimensions, so obr motors really go nuts and make the most power with the vrc's as the reflective sound wave is timed perfectly with the piston stroke..
dynos are just a tool for comparison on the same motor, change something...run it and then see if the changes you made were good or bad...
and dyno figures from different dynos are apples and oranges imo...for any relevant comparisons between different engines they all need to be done on the same dyno with atmospheric conditions remaining constant for the test duration..they are also handy to see the hp and torque curves in relation to rpm
dynos are just a tool for comparison on the same motor, change something...run it and then see if the changes you made were good or bad...
and dyno figures from different dynos are apples and oranges imo...for any relevant comparisons between different engines they all need to be done on the same dyno with atmospheric conditions remaining constant for the test duration..they are also handy to see the hp and torque curves in relation to rpm
30.5cc
that will be cool,cause im also looking to have another motor built.thanks for responding back.
although alot of people know dyno results don't tell the whole storey, I guareentee all want to know hp either by finding out on the net or getting them dynoed. eg, I know I have the mst powerful production motor sold for a baja but I still want to know hp, torque, rpms and most importantly where the hp and torque are produced.. its just men and motors,