Topic: CB 836cc f1 turbo - spoked kickstart street turbo

[ivanhoew]

i think i have one washer on the 500.

[Ilja]

Just ordered a new gopro as my old one isnt working anymore..
Hopefully I can make a driving vid this weekend! :-)

[Ilja]

Yay, short vid driving... :-) Not crazy revving as I'm still breaking in the engine..but it gives a nice impression of the bike.

I don't have a speedometer yet and apparently you don't hear much of the engine..
but full throttle in 3th gear is already quite fast... bike has 18:39 gearing. 

I'll try again with the closed gopro casing soon.

[Ilja]

Small run with the dual stage switch at 0.5bar!

...and one with the switch at 0.7 bar!

Quite happy how it runs! Tomorrow I will spend the day installing the intercooler.
Looking forward to test if what difference it will make, both in responsiveness and turbo power.

[Bill/BentON Racing]

Nice, you pull that gearing to redline....you be flying!

[Medyo Bastos]

looks and sounds great from here 

[Ilja]

Installing my piston insurance policy.. 

[Ilja]

 

[Ilja]

Strange...uploading multiple pics seems to always be bugged for me... need to ad them one by one.. 

[Ilja]

Done!

[Ilja]

Just did a testdrive! No IC pressure drop visible and no lack of bottom end or late spool either, exactly same boost pressures as before. It seems to spool up a tad slower, e.g 0 to 0.7bar takes from 4-5k rpm instead of 4-4.7k rpm.

But GOOD LORD the difference in power is bizar! The bike suddenly became a bit scary to accelerate full throttle!
A/f is also at 11.5 instead of 10.5, though that may also be partly due to me only having 1 big pitot tube now instead of 1 small and 1 big.

Definitly a huge difference! ahhhh now for some beers!

[NitroHunter]

Awesome!

[ivanhoew]

nice joB ... always estimated my ic added about 25% power.

[Ilja]

Made some small vids doing some pulls to 150kmh with the intercooler mounted... shifting at around 7000rpm. 

I've also lowered the front 2.5cm by removing the extensions on to fork tubes since its also extended 3cm internally.... turns better and more stable now.
Also repositioned the boost regulator closer to the WG actuator, and installed a one-way valve in the "standard spring pressure" line.. boost spikes seem to be almost gone now, just a steady 10psi. 

Got a small lean(er)-spike around 5.5-6.5k rpm... so gonna add the second pitot tube again to the transfer pipe as it didn't have that with the two pitot tubes on the old transfer pipe.

[Ilja]

Plenum popped off.. so made a small vid before cruizin home.

Did 100 km'ers driving pretty fast, all was fine untill the plenum popped of the last 3km with a loud POOF... god that gave me a scare.. thought my engine popped!

Second pitot tube cured the lean spot but WOT is still at 11.5.
So the intercooler leaned out the afr from 10.5 to 11.5 by cooling air and adding o2..

[Jim F]

very very cool bike

Now I need to get mine and start to work on it

Jim

[ivanhoew]

dyno time ?

[Ilja]

Thanks and yes I will do a dyno run.. probably in wk 38 because of my holiday next wk.

I will probably do a 0.7bar or 10psi dyno run.. nice to compare with last time!

Think i'm going to leave it at this pressure since the engine seems to be happy with it and its already pulling like mad.

Bit afraid that by raising pressure i'll run into detonation/pinging again or destroy the gearbox or primary chains/cush.
It was a lot of work so might just ride it for a while first... (and finish some other projects )

This 10psi seems like a safe pressure as I already did many WOT pulls with it..
Actually this is already quite extreme power for a cb750.
Its somewhere around 125-140hp if I may estimate judging from the last 110hp dynorun at only 7.5k rpm..

Main motivator for this is also seeing the pics of some classic endurance guys I know.. they managed to snap a primary chain and a conrod last week with a sohc cb750. Engine completely destroyed....
Old chains but still!

Time to enjoy the bike for a bit!

[Bill/BentON Racing]

Did the rod go first and take out the chain.... can you tell which went first? Thanks and good job, Bill

[ivanhoew]

good thinking Ilja .

[Ilja]

Back from holiday!
So today i've enlarged the exhaust from 30 to 43mm...
Didnt make a huge noticable difference but it feels a little bit smoother and quicker. Still pretty silent but louder resonation on lower revs.
Also tried without muffler material and it sounded like a dragbike...

Ive also fabbed up some rods to keep the plenum in place, because it popped off under boost scaring the hell out of me.

Looking to have a dyno run this week! Curious to find out what she makes!

[Ilja]

Did the rod go first and take out the chain.... can you tell which went first? Thanks and good job, Bill

Not sure... the guys think it was the chain..which in turn blocked the conrod next to it.
They were running old stock chains, and racing is constantly riding at high rpm which is a chain killer.

[Ilja]

Just for info purposes about the gt1752 turbocharger im using..
It comes from saab cars and its called a lpt, low pressure turbo. It doesnt have a strong axial bearing and was used in the cars to run 0.4bars of boost with max of 0.7bar.
They fail a lot and most people replace them for td04 or t25 turbos that are a lot bigger.

The good thing is they spool and react very fast. The bad thing is it runs out of breath at a higher rpms,... which is a bit what im seeing... boost runs back a bit going through the revs.
So its fine for a low pressure build but essentially still too small.

Also, the increased backpressure causes a lot of heath to the exhaust valves, which in turn causes pinging.

If it starts failing in the future I'll probably replace it for a t25, which is a solid strong 50mm turbo which can run 15-20psi, cheap to rebuild and good for up to 200hp.

[ivanhoew]

ilja ,


i used the gt17 on my 1310cc  1972 mini . dynoed at 248 bhp ,and will run up to 25 psi boost no problem .


here's a link with more info ..


http://www.turbominis.co.uk/forums/index.php?p=vt&tid=10263


regards
robert.

[Ilja]

ilja ,


i used the gt17 on my 1310cc  1972 mini . dynoed at 248 bhp ,and will run up to 25 psi boost no problem .


here's a link with more info ..


http://www.turbominis.co.uk/forums/index.php?p=vt&tid=10263


regards
robert.

What!! Wow, thats a lot for such a small turbo.. at least 50hp above rated power.
Almost nobody runs high boost with these turbos.
Did you run octane booster or race fuel?

Im having a hard time getting more then 12psi out of it without it creeping back down through the revs. Might be the actuator and regulator then.