Dyno Time

luckily got the offer of my bike getting some free dyno time as a training aid for a freind and it was very interesting ;I decided to take the gsxr carbs off and put the hitachi's on to see what they were realy doing .
My bike is :
81 750 seca
PODS
Dynojet 124 main and D/J needle

Now I wasnt realy worried about power numbers but I just wanted it to be smoother, wasnt bad to begin with but I have a hatred for the Hitachi carbs.

anyhow , first run and realising I am so glad its just had a oil change with good quality oil .
lumpy top end and power curve .

2nd run , better curve and not so lumpy , decided due to the amount of rain weve had that the pods were damp and rying out so we dried them out more.

3rd run lovely and smooth but A/F meter showed top end was rich so we took the pods off all together it was much better .

so now I am running with the pods back on with 120 d/j mains and its like a different bike soooo smooth . final bhp figure was 71 at the back wheel which I am happy with for a 31 year old bike . The dyno operator was quite impressed as he expected 50-60bhp. We had a good chat and he said a few things that back some of whats been said on here .
1, a custom exhaust especially a shorter one is far worse than pods .Bikes rely on back pressure , example ; R1 with £800 bolt on silencer puts out 15 bhp less than a standard bike , Customer argues it cannot be possible as it cost £800

2, although pods let through a lot more air , it isnt always the case to have bigger main jets as a lot of the air is wasted as turbulance . air could be forced in the carb but as the turbulance swirls it could miss the areas that it needs to be altogether.so yes you do lose a few bhp but whether anyone would notice it is up for discussion

His only gripe about pods is the fact that they get damp . this can be solved by oiling them but this then restricts the flow.

so a good day , a bit scary watching the bike stationary at full revs hoping to not have to catch the odd conrod or piston but very educational

 

Congrat's on the good numbers and you did a great write-up WITH explanation but you've much braver than I. We used to do everything that we could to get more power out of our race bike back in the 70's but as curious I am aobut my turbo, I'll pass on it....guess my reflexes have slowed down and I'm not sure I could still catch that rod<LOL>
jeff

 

If it's going to toss a rod on a dyno then it's going to toss a rod regardless, it just might be a bit further down the track

For doing jetting a dyno with a a/f meter makes it so much easier and faster

 

Thats awesome, congrats. I hope I will pull more, but time will tell. Haha. Hows about some pics of the bike?

 

Id love to see an xj toss a rod.

 

I saw a youtube video of some guy hot dogging his 650 seca until it tossed a rod in the direction of the camera man. It was linked on this site, but I haven't been able to find it recently.

 

Really nice explanation!! Great number too!

 

cheers guys for the comments .
another rather un- scientific day but i decided to put the 124 dyno jets back in richen it again then to counteract that used a long sharp tube to open the can out a bit , very bodgit I know but another run on the dyno has taken it 72bhp at the wheel and a nice smooth power curve . I know its only 1bhp difference but the noise it now makes is bloody awesome and well worth it

heres a crappy pic at the local bike meet .


the headlight is now " quick relase" so I can take it off in the day as it looks so much better up front with just the number board. Its also a lot shinier as I have polished the aly bits more .I am also getting a new master cylinder so I can do away with the cable operated one and go down to one disc at the front . I am also getting new forks without the anti dive to clean the front end up a bit. I have fitted rear shocks off a xs750 that are an inch longer so that has raised the tail a little bit .
still lots of stuff to do to it through the winter . cant decide on what colour to do the wheels or fit something with spokes . I am also a tart as I have 20 ml of castrol R mixed with the fuel so it even smells nice .gets lots of comments and I am sure they should make a castrol R perfume