Vespa BGM MRB Clubman - 30.21hp

Post your Vespa dyno graphs here! But graphs & spec info only, keep the chat in the 'dyno chat' section ;o)
registered user
Posts: 361
Joined: Thu Jun 24, 2010 7:48 pm
ebay user ID: fairspares
Main scooter: Lambretta GP RB252

Darrell Taylor wrote:
MattsDad wrote:Sorry I don't really use or own standard pipes but hopefully will be doing an expansion comparison next week.
Its new engine build and not standard. Not welded, 57 stroke, Vespatronic, reed, centred head, and TM carb.
Its got packing options to make into a touring tune also so will graph that too.
Here's the torque which shows efficient bmep peaks so happy will that and more than surprised the pipe revs through this far:

just noticed on this graph of the lambretta dyno put on by accident that the correction factor is missing/cropped off the picture ,i took a look at the old rapido 42bhp post and found the correction factor shown is sae 1.21 whereas the vespa graphs are 0.96 / 97 which is more or less what uk weather corrects to fluctuating from min 0.95 to 1.05max

this means the power figure shown is inflated by 0.25 which corrects to a real figure of 31.34bhp be worth asking the dyno guy for a new graph with the the appropriate correction applied

if the original 26.31 graph was 0.97 and the 1.21 applied you,d see 32.8

figures arent perfectly calculated ive applied 25% for the 0.25 which is close

id presume the old graph at 26.31 was around a 0.97 correction
and new graph with new tune 31.34 with 0.97 correction applied so a healthy 4bhp increase all the same

Ive checked through my previous dyno graphs and you are correct Darrel the correction is either 0.97/0.98 with a correction of 1.21 on the 42 bhp graph , your conclusion tallys with my dyno results by Dan that my engine is only producing 33 bhp and 22 lbs tq , this also corresponds with my sprinting times/speeds. I will now have to go and read up on how dynos are set up so i dont have the wool pulled over my eyes again.
Fairspares Lambretta workshop.
Darrell Taylor
Posts: 752
Joined: Wed Apr 06, 2011 8:43 am
Main scooter: LAMBRETTA
Location: Doncaster

can only think the temp probe was faulty or in a position of extreme heat etc to have miscalculated

sorry for offtopic ,back to the vespa
Last edited by Darrell Taylor on Mon Sep 16, 2013 7:02 pm, edited 1 time in total.
feel free to use this link to contact me on facebook and like it(if u like it) ... 8819767924
User avatar
sean brady scooters
Posts: 2040
Joined: Mon Jan 05, 2009 12:09 pm
Location: Ripon, North Yorkshire

we could see that you were somewhat dissapointed shaun at your results on our dyno ,but great that this has been sorted :)
Sean Brady Scooters - 01765 690 698
registered user
Posts: 740
Joined: Wed Jan 07, 2009 10:57 am
Location: drax,near selby,north yorkshire

sean brady scooters wrote:we could see that you were somewhat dissapointed shaun at your results on our dyno ,but great that this has been sorted :)

not only shaun may have been dissapointed,i run a similar set up and was sick that mine only acheived 35hp, although i was thrilled with its ability to pull a three furrow plough up mount everest despite this and the aching shoulders due to hanging on!
User avatar
Posts: 2838
Joined: Sun Jan 04, 2009 1:42 pm
ebay user ID: sc00terotica
Main scooter: '69 Lambretta GP
Location: North Yorkshire

joespeed wrote:.........,i run a similar set up and was sick that mine only acheived 35hp
I think that comment sums up what a great era of tuning we are in right now. When people a disappointed with 35bhp!

Any Rapido which pulls 30-35bhp Is doing well and certainly not to be sniffed at. Good stuff gents.
See our YouTube scooter channel for Tech-help:
registered user
Posts: 78
Joined: Sat Jan 17, 2009 2:21 am

Sorry for late reply, too busy.
Oh, that engine, there were some communication issues so we couldn't convey the correct data, until now :)
You were nearly there Darrel, not temperature but a faulty atmospheric pressure sensor. The figures were close enough; uncorrected was 34.51 and at standard INHG 32.68hp with an SAE of 0.947. An increase of 6.37hp or 24%; more if the next port layout and pipe design had been implemented.

Dan the dynojet is a motorbike garage local to me. Clutch slip issues there this week on the BGM comparison with expansion, as there is a bit more power there but this is graphed before its latest fettle and it holds up very well I think. Both are SAE corrected.

registered user
Posts: 78
Joined: Sat Jan 17, 2009 2:21 am

Tested on new engine, run in 100 miles and set up for the BGM, first time on dyno.
First run with expansion in pink, thought maybe the jetting.
Second run brown with BGM, very nice and does it better lower down than the fast road engine.
Third run Blue, BGM with a tweak but dip back and its a misfire but no electrical spares to hand.
Happy result for a Clubman on a touring engine at 26/27 once the misfire sorted.

Post Reply Previous topicNext topic
  • Information
  • Who is online

    Users browsing this forum: No registered users and 0 guests