Topic: fuel injected supercharged resto mod cb550 track & street bike.

[Harald F]

but i bet it was fun while it lasted ?

[cbornotcb]

Yep !
Here's a test run.

& the 2nd failure (of 3)

[Harald F]

now thats a failure

[cbornotcb]

I'll have another go next year, I recon it's sorted now 
Tiny

[Harald F]

what did you change ?

[cbornotcb]

what did you change ?

I had leaking valves, AFTER paying someone  to redo the seats, grind the valves (there were minute fragments embedded in the seats & valve faces from the "pissed ' n ' broke " year), I bought a set of Newway cutters and did the job properly myself.
 Due to the draw thru setup I use, burning mix ignited the methanol mix in the plenum (my BOV works well), & due to the remoteness of the salt lake, I tried to minimize the back firing by leaning it off a bit with the power valve (I didn't know about the valves leaking at the time) and put the "jockey" on board, he made it to 4th gear before it backfired, which I heard clearly from the start line a mile away from him,
I guess pre-ignition caused the power drop he felt, and inverted the piston crowns.

The decision was made to de tune it for next year, "stock" cams with 1mm more lift, and heaps of overlap, which would drop the boost from 15 LB, to 10 LB, & hopefully help cool the ceramic topped pistons (the only pistons available for less than $550 each, bare) are Chinese ,,and, as I discovered while checking valve / piston clearances, with 1mm more lift, I had minus point 5 thou" clearance,,,and 16 bent valves (ever so slightly)
A 2mm head gasket is being made, and I'm about to pressure test the valves using a Perspex gasket, and a dead block,,,3 months to go, and so little play time,,,,
Tiny

[Harald F]

done some more work on the supercharger system.. just need to make the axle and modify the pulleys now.

[dragracer]

Any more progress on the bike??

[Harald F]

tensioner pulley for the main belt is a mazda miata cam belt pulley


Made a new flywheel bolt with adapter for the drive belt pulleys.



Made several different sized pulleys to be able to select best gearing for correct boost while at the dyno with minimal delay.


Final test assembly before stripping it down and sending the frame to be powdercoated


Todays small update enjoy

[fastbroshi]

This is friggin awesome, can't wait to see how much power it makes. 

[Harald F]

i literally have no idea its running a dynoman stage 2 kit for the 550(now 592), with a ported head and maybe 0,4 bar boost? should be easily above the stock 50hp
how much rpm would be the recommended maximum for the stage 2 kit ? 10k ? 11k?

[fastbroshi]

You're just being modest, I'm sure you know    Only thing that concerns me is the CR for those pistons, which I think are 10.5 or 10:1.  Did you massage any thing to get it back down a little?    I'm not that experienced with pressurized motors, everything I know is from what I read.

[Harald F]

10.5 CR is "ok" for boost as long as i keep it down to low boost levels.. and unlike pretty much any other boosted CB, i have full control over fueling and ignition angle and can easily program in some degree of safety margin while boosted. we will also monitor for knock during dyno tuning.
If i had a lower CR, and a air/air intercooler i could up the pressure to stupid levels   Ive been considering adding a water/meth injection system.. but it will probably be fast enough as it is

[Harald F]

to answer the horsepower rating, i would be really happy to see 90hp crank

[Ilja]

Wow very beautifull bike!

Are you running 10.5CR?
Your damage, like you said, looks like pre-ignition which is typically caused by overheathing.
Could be that your engine never detonated, but just got too hot and then pre-ignited and blew the piston crown.

But I'm afraid that 10.5CR with the tame camshaft(high DC) is just too much on boost, even with less ignition.. be carefull. 

What I found out building my cb836 turbo is the following:

At 9:1 CR with 1mm spacer (and therefore bad squish) it pinged at anything over 0.5bar(7psi), regardless of A/F and ignition above 25 degrees. I pinged out the ringlands at 0.8 bar but piston crown looked spotless due to the correct A/F.

At 8:1 CR I'm running 0.8 bar (10-12psi) without issues. Did not run it higher because I still want to install my Ingitech ignition with boost retard and a better boost controller. It tends to spike a bit if I run higher boost.

My kawasaki z750 turbo can run up to 1.5 bar without pinging, which is more or less the same engine (aircooled 2V, flat top pistons, few mm shorter stroke, same ignition currently)

The key difference is dynamic compression ratio. The CB750 has one of the most "conservative" camshafts I have ever seen. 10 degrees of overlap and very short duration (220degrees). For comparison my kawasaki has 265 duration and 45 degrees overlap and that is already regarded "not too wild / tame".

This is why the CB's are sensitive to pinging. (but also very streetable and usable off-boost!)
Low compression ratio matters because of this.. theres not much safety margin. But it also mainly helps keeping the temperature down.

What makes it hard is that with a loud exhaust, you can't really hear the pinging very well. It's just very small ticks like shaking a small roller bearing ball in a can.
You run a supercharger so your exhaust is much louder then my turbo bikes. (my honda is very silent)

[Harald F]

The engine was first planned as a na engine, we will be running low boost (maybe 0,4 bar boost) the cam is not stock and has more overlap and more duration than stock. we will be running a knock sensor during dyno pulls and if all else fail and we still get issues i will have to get custom pistons made later.
we normally build cars and have a decent knowledge of carefully tuning for reliability. 


BTW if anyone knows of a +2mm bore(61mm) forged, low compression piston, please let me know

we will be careful

[Harald F]

oh, and thanks for the input, always cool hearing from others that have boosted the CB's before

[calj737]

BTW if anyone knows of a +2mm bore(61mm) forged, low compression piston, please let me know

JE makes the +2, but they're high compression. Wonder if you could mill the domes (you don't seem the least bit incapable of such an alteration) to lower the CR to your target? Some simple math and an end mill (and a reasonable amount of courage) and you could have it. I'd be curious if the piston has sufficient material thickness to achieve it-

[Harald F]

Checked, there is not enough material to mill the tops flat, if there was, i would probably do it ( i have the JE pistons )

[Ilja]

The engine was first planned as a na engine, we will be running low boost (maybe 0,4 bar boost) the cam is not stock and has more overlap and more duration than stock. we will be running a knock sensor during dyno pulls and if all else fail and we still get issues i will have to get custom pistons made later.
we normally build cars and have a decent knowledge of carefully tuning for reliability. 


BTW if anyone knows of a +2mm bore(61mm) forged, low compression piston, please let me know

we will be careful

Ah very nice, yes the bike shows you guys are capable enough!
Yes I do by no means want to criticise your build or anything, but I just spend one year of my life chasing Honda CB pinging issues... 

My cb turbo also still uses cast pistons.. it's criticall to get everything set up correctly because they fail quickly if somethings wrong.
Problem was also finding forged ones.... I just won a MTC flat top forged piston kit on ebay, but normally they are impossible to find.
 
A forged piston will show slightly lower pistoncrown temperatures but it will also meltdown if something is wrong (detonation or too much heath).
It will take abuse a bit longer, giving you time to sort the issues , but will for sure also fail.
Or it won't fail but your crank bearing shells get hammered flat or small ends lockup and the rod breaks. 

[Ilja]

By the way..

http://www.bullfrogmotosport.com/product-p/600.2028.htm

Looks *lower* compression to me and the compression height could be close..

[Harald F]

I know.. i would prefer a lower comp ratio, but given that this will only be a very  low boost setting, and gived the degree of control over ignition and fuel, and careful dyno tuning i think this will work ok. More used to pushing 500hp+  from old mx5 turbos than oldschool motorcycle engines.
everyone told us they would not be reliable either, 10 years and counting pushing up to 2 bar boost with good driveability so far

[fastbroshi]

Check the DP592 street piston here.  10:1 CR.

http://www.dynomanperformance.com/engine/pistons/dp-CB550.html

[Harald F]

Small but very important update.. frame is finished and beeing mediablasted and then powdercoated now.. 

[Harald F]

the frame is now painted.. 30(satin) black frame. 80(gloss) springs.
Just had to testfit a few parts to see how it will look.  Just a matter of putting an engine in it now