Gt186 carb and exhaust

[Mick Abbey]

This is interesting stuff. It would be good if someone were to draw up some sort of chart as to what exhaust is good with what tune. I know there has been talk before of using Clubman style pipes on tuned engines, but I wasn't aware of any issues with them clogging up.

I couldn't tell you what works best with what as I just build my own pipes to suit my own tuning for me its the only way forward.

[lozmondo]

changing from a Cam Lam ancillotti to a BGM clubman gave me 2bhp and1.5lb of torque on an SR barrel fitted with a reed valve. Not huge figures but it pushed it from 12 to 14 bhp..around 15% increase. Just a thought

[shamrockexpress]

Going to be running in my GT186 with a jl3 is anyone useing a jl3 if so what kind of performance is expected what will it rev too?
I know its not a first choice pick for this kit i will be changing to an ADS race once run in.......

[Muttley McLadd]

Going to be running in my GT186 with a jl3 is anyone useing a jl3 if so what kind of performance is expected what will it rev too?
I know its not a first choice pick for this kit i will be changing to an ADS race once run in.......

I've not run one.. but wouldn't a long pipe like a JL3 suit the GT more so than a short revvy one?

Personally, I'd avoid something that'd make it a pain in the ass to ride.

[hendy]

Going to be running in my GT186 with a jl3 is anyone useing a jl3 if so what kind of performance is expected what will it rev too?
I know its not a first choice pick for this kit i will be changing to an ADS race once run in.......

I've not run one.. but wouldn't a long pipe like a JL3 suit the GT more so than a short revvy one?

Personally, I'd avoid something that'd make it a pain in the ass to ride.

I'd agree with Muttley. Exhaust is around 175 and transfers about 126 so a blowdown of about 25 degrees which isn't particularly revvy.

[eden]

I tried an MB V3 box pipe on my gt250 a few weeks ago and it reduced the max BHP by over 10 HP and only gave it 3 HP more below 4k rpm.
Not slagging the MB pipe just confirming Dan's findings when comparing box pipes and expansions.

[hendy]

I tried an MB V3 box pipe on my gt250 a few weeks ago and it reduced the max BHP by over 10 HP and only gave it 3 HP more below 4k rpm.
Not slagging the MB pipe just confirming Dan's findings when comparing box pipes and expansions.

I've heard this is a bigger effect on higher revving higher capacity motors as they're restricted by the inside diameter of the tailpipe (around 20mm compared to 25mmish on expansions I think). Because in simple terms they need to shift a higher volume of gas through the system. Just as an example, a 250 which peaks at 8500 rpm is moving gas through the system at a rate about 65% higher than a 186cc which peaks at 7000rpm.

I'm not suggesting that the effect doesn't exist on smaller lower timing engines, but rather that it is a smaller effect. Clearly, tuned length comes into play and the restricted tailpipe still matters, just less so.

Discuss.

[shamrockexpress]

I,m not looking to cruise this engine I,m hoping for a fun around town revver so I have lifted the exhaust port 1mm (should have said that oops!) ehaust timing is 180 ........so as per plan run it up with the JL3 then try the ADS race only because I have it sat on another motor doing nout!!!!

back to original question when will the JL3 turn off? 7, 7.5 would it reach 8........

[hendy]

I,m not looking to cruise this engine I,m hoping for a fun around town revver so I have lifted the exhaust port 1mm (should have said that oops!) ehaust timing is 180 ........so as per plan run it up with the JL3 then try the ADS race only because I have it sat on another motor doing nout!!!!

back to original question when will the JL3 turn off? 7, 7.5 would it reach 8........

Look at the graphs on this link. I think they're all on a ts1, but they still give a good idea.

http://www.andyfrancisscooters.co.uk/dy ... 4580566211