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

[ivanhoew]

if you do some searching about it , the basic turbo in vnt form is used on some audi s up to mega boost , they seem to top out around 265 bhp  , this is about normal for a 38.55 mm inducer compressor .the saab foums ecuproject etc have a fair bit about when they top out .

they appear to be very efficient and have a good low back pressure turbine ,with an open blade design .

i just run shell v power ,but when racing i run it with the choke out which gives me around 12.8:1 afr .  i am using a 8.5:1 cr .


try wiring the wastegate shut and then see what happens to boost on a test ride ?

i have found my car will wizzz round to 25 psi effortlessly(when i forgot to have the boost pipe on lol) ,

i am using a 53mm id exhaust all the way through,silencer included .

[PeWe]

Turbo talk! a little bit OT
I had ideas about a bigger turbo in my Audi 1.8T B6 Avant quattro with K03s turbo, 190hp original, dual intercoolers, around 225hp with a chip but torque increased much more.
Some hp more and earlier sppol up with Milltek sport cat with complete exhaust. The turbo stalls around 5500rpm on 4-6:th gear, produce a lot of heat. A huge intercoller might help. Metal inlet pipe was a must when original rubber collaps when turbo boost kicked in. All piping/hosing must be rigid to avoid boost surge.

Maybe a K04 modified version able up to 300hp will find its way in later. My turbo can have a bad bearing,  lately it has started to squeel more at highest boost 1.2Bar,  a little bit more as over shoot due to the valve delay.

I found this thread some years ago where different turbos were compared. The larger ones giving more power is very bad low rpm response under 4k rpm.
http://www.audiforums.com/forum/b5-models-69/1-8t-turbo-upgrade-information-93439/
There are turbos with std housing for std manifold but different inside and still able to give over 300hp with correct injectors and software.

[Ilja]

I have a garrett t25 on my 750 turbo which I can run up to around 20psi... but thats nearly unridable. At 15psi it already wheelies.
(I'm gonna make a vid about that tomorrow btw )
It starts making boost at 4.5k and has full boost at 5.5 -6k.
Bike never pinged or anything and boost is rock solid.
The T25 is around 50mm inducer and turbine.. people make around 200hp with them at 20psi.

The honda with the gt17 has more torque offboost, probably because of 836cc vs 750cc and the stock camshaft has less overlap. It goes into positive pressure at 4k rpm and has full boost at 5k... so thats quite early.. but goes back down abit through the revs running 10-12psi. If I set it higher it goes down even more. Im not sure if it will tolerate 15psi without pinging... might need a turbo that kicks in later with less backpressure for that.

The honda is a lot more silent, about identical exhaust systems with the kawasaki having a slightly smaller exhaust tip. The smaller turbo muffles sound a lot more.

The gt17 is a fun turbo and makes the cb very fast, and is nicely responsive and fits the bike perfect.
But its not like the T25.
That one feels like entering warp speed when you roll on in fifth.. (could also be the +1bar boost hehe)
But I really like riding the Honda because its still a very usable street bike like this, with at least 120+ hp.

So now I have a very fun ridable torquey reliable low boost Honda and a crazy highboost moody efi Kawasaki turbo to choose from to ride to work and grocery store.. .
Life is good... when all bikes are working.. .

Next projects are building my z1r which is in parts and turbocharging my xr650r supermoto.

[ivanhoew]

mini power graph ,




drag run boost data logs from 2 different years to compare ... ..

[Ilja]

mini power graph ,




drag run boost data logs from 2 different years to compare ... ..

Nice! Also smooth power curve.. thats some serious power out of a mini!
I need to find out whats holding mine back..

[Ilja]

I just got the kawasaki running again (after lots of fuel system and ecu issues).
Here are some small testrun vids.. clutch slips again.

You can see that with the bigger T25 it behaves totally different from the honda.. bike revs up slow (although im also not giving throttle below 5000rpm) and then suddenly flies to 9000 - 10000 rpm. Running about 15psi here.
Much more power in topend revs, but not much down low.
Its geared a bit lighter then the Honda (around 1 front sprocket tooth)

The Honda is really the opposite, all the power is between 5500-7500 rpm which makes a nice juicy fat midrange and above it feels a bit flat.
But this makes the Honda very very usable on the street.
Boost is lower on the Honda but still... mostly its the combination of the bore-stroke, camshaft and smaller turbo.

The area where the Honda is prone to ping (around 5500-6500rpm) the Kawasaki doesnt even make boost yet. 
Not completely sure if the Honda still does it though, but when experimenting with higher boost I think I heard one or two ticks... and then nothing. At 10-12psi it runs great so left it there to be safe!

[Ilja]

Found some old T25 compressor maps, and compared them with the GT1752 compressor map that can be found on the internet...

Seems like the GT1752 flows way more and at a better efficiency then the bigger sized T25.

Must have something to do with the T25 being older tech...
So in principle I can also install the GT1752 on the Kawasaki and have the same power + much better spool. 

Honda is working awesome, did some more riding and it's everything you could want from a turbocharged cb750.
However, I'm going to up the gearing a bit as it is geared for too much top speed (270kmh according to the gearing chart ) and you can really feel the long first gear when you ride away from standing.

Think I'm going to change to 18:43 instead of 18:39..
I have a brand new supersprox 46th rear sprocket, but thats a bit on the light side I think, the turbo needs to pull a bit.... though could be fun with wheelies.

[ivanhoew]

as far as i can tell ,the saab sized t25 tops out around 285 ,and the 17 around 265 ... check the origination of any maps you find on this.

best bet is to take a gt2056 map , and scale it down by the % of inlet inducer area difference i think the 17 was 38.55 mm dia and the 2056 was 41.4mm ish .

[Ilja]

Yesterday I did a 350km trip with work collegues.. bike worked fine and averaged on 6 to 6.5L of fuel on 100km riding around 80-110km hr with lots of twisties.
Did a small traffic light sprint with a Honda vfr (or vtr?) and accelerated about the same untill 3th where I left him behind. :-)
 
I had to shift to first!! gear a lot in turns riding in the group or in traffic... also the top speed is a bit over the top for a no-fairing bike. It does 135kmh at 5000rpm so its nice to cruise on the highway but 135 at 5500 or 5800 would still work fine.
I will probably never ride any extended period of time above 200kmh so I might as well gear it a lot lower.

Still have boost set at 10psi.. tried 14-15psi but I heard some slight pinking around 5-6k doing a pull so thats not gonna happen.. 
Bike feels good offboost and has all the torque from 4500- 7000 rpm. From 7000-9000 rpm it keeps on pulling but you can feel torque tails off... I think just like the original bike did.

So I came to think let's have a look at cam timing:

I have an F1 cam, but can't find any info on it.. however the K models have the following specs according to this forum:

Intake opens 5 BTDC, closes 30 ABDC
-Lift: 8mm.
-Duration 215
Exhaust opens 35 BBDC, closes 5 ATDC
-Lift: 7.5mm.
-Duration 220
10 degrees overlap.

The 10 degrees overlap is very little for an N/A bike, as normally with a decent flowing exhaust with little backpressure bikes have 45-65 degrees of overlap to create a scavenging effect filling the cylinders.
However for a turbo bike, you want as LITTLE overlap as possible because there is a lot of backpressure (more then boost) between the turbo and the exhaust valves... if the intake and exhaust valves open at the same time you get a thing called "reversion" which kills your bottom end and midrange torque.
So actually this is pretty good and explaines why the bike still pulls fine offboost... BUT the duration is really really short.

My gpz turbo engine with gpz turbo / z650 (identical) camshafts has the following timing:

Lobes 105/110
Intake opens 22 BTDC, closes 52 ABDC
Duration 254
Exhaust opens 60 BBDC, closes 20 ATDC
Duration 260
Overlap 42 degrees
(I once tried a hotter exhaust camshaft in that bike with more duration and 65 degrees overlap in total, and it really killed all bottom end torque. )


I'm thinking that the cb750 stock camshaft is designed for a nice torqeuy City Bike ride without revving out too much, concentrating torque from 4500 - 6500 rpm. So the stock cam is causing high cylinder pressures in midrange because it has so little duration (and overlap).

But I think this can also cause pinking in midrange when pushing the engine with higher compression or a turbo... 

Soo... I never looked at aftermarket cb750 camshafts and their specs... but I'm interested to try one with more duration.
Are there any aftermarket camshafts available with little overlap (between 10 and 40 degrees) but with longer duration around 250 degrees ?

[Jerry Rxman Griffin aka MuthaF'er]

CB750F cam:

Int open  5 BTDC
close      35 ABDC

Exh open 35 BBDC
close        5 ATDC

My bike ran exceptionally well when new. I recently took my mic to some stock cams to compare and discovered my early model 75 F cam has exh lobes that are 0.1mm taller than the 78 K cam and the 77/78 F cam which has 5 more duration. Honda has been know to sneak in performance boosters early in a model run. May help explain the performance I had.       

[PeWe]

Read this?
Turbo cam described here. (I guess still possible to order from Megacycle)
http://satanicmechanic.org/megacyclecam.shtml
125-N-T3.342    215   109.5   Turbo profile Norris design        2/37     .004
        .312    222   110     Turbo charged engines. Use race    41/1     .006

CB750 turbo kit:
http://www.satanicmechanic.org/turbo.shtml

[Ilja]

Read this?
Turbo cam described here. (I guess still possible to order from Megacycle)
http://satanicmechanic.org/megacyclecam.shtml
125-N-T3.342    215   109.5   Turbo profile Norris design        2/37     .004
        .312    222   110     Turbo charged engines. Use race    41/1     .006

CB750 turbo kit:
http://www.satanicmechanic.org/turbo.shtml

Thanks!

The turbo cam has the right idea with the minimal overlap but the stock cam already has minimal overlap so the improvement would be very small. Also duration is about the same as stock..

The 125-05 looks interesting....
Duration is perfect and overlap is acceptable.. though a lot more then stock.

Does a hardwelded cam also require hard faced rockers or are the stockers ok?

[ivanhoew]

"The 125-05 looks interesting....
Duration is perfect and overlap is acceptable.. though a lot more then stock."


i'd suggest ,way too tight on the lobe seperation angle , i would ask them to make that same cam , but with 112 degrees lsa .

[Ilja]

"The 125-05 looks interesting....
Duration is perfect and overlap is acceptable.. though a lot more then stock."


i'd suggest ,way too tight on the lobe seperation angle , i would ask them to make that same cam , but with 112 degrees lsa .

Yes indeed, that would be nice...though not sure these guys would do that for an affordable price..

I believe a wider lsa moves the peak torque /cylinder pressures up in the rev range right? Or did it spread the powerband?

I must say that I don't know exactly where the limits are regarding duration and LSA...and what is best for a turbo charged engine. Need to do more studying on cam timing.. :p but it's hard to find really good information on it because the internet is full with "second hand" experiences. I need a book on it or something.

The only thing I know is a turbo needs no scavenging from the intake during evac, because it doesn't really happen untill high in the rev range and you only get reversion.. so overlap needs to be little and in general likes modest cams..

What I want is spreading the huge mid range peak to midrange and topend and by that reduce cylinder pressure in midrange.. should make the engine more detonation resistant and a bit more rev-happy.

So far I can only compare to my other turbo bikes specs which works great at high boost on pumpfuel and has a comparable engine architecture.

[ivanhoew]

wider lsa in this case flattens the trq curve , making it a bit better at bottom and top and less good in the middle ,

 combine that with the increased duration ,and the wider lsa also reduces exhaust backflow  into the inlet as the rpm rises and the turbine back pressure rises .

 the increased duration also raises your max rpm for trq and bhp peak , as long as the head and turbo /manifolding can keep up .

a rough rule of thumb is 10 degrees of duration added gives a 500 rpm rise in pk bhp . so if you have a power peak of 8500 rpm ,and 215 d inlet duration ,then adding 30d would raise pk to 10k rpm . eg 245 d  duration , ,,,the confusing thing is that different cams can be assessed for duration at different lifts .using the .050 thou lift point levels this off a bit .


regards
robert.

[Ilja]

Thanks Robert!
Now to find a decent camshaft.... webcam 341a looks good aswell with 114 lobe centers, 12.5 overlap and a bit longer duration.

I also want to share this great tool with you guys:

http://cochise.uia.net/pkelley2/DynamicCR.html

You can download a dynamic compression ratio calculator from that page... to figure out your compression ratio with regard to cam timing.
If you have a cam with small duration your compression ratio will be (a lot) higher then when you are using a wilder cam, which closes the intake valve later...

The period between closing point of the intake valve ABDC up to TDC, in combination with piston position determines your Dynamic compression ratio. This changes with different durations and lobe center.

Thats why with performance camshafts you can run, and are advised to run, higher compression ratio pistons.... but its alsways hard to figure out the needed figures...

This also shows that my cb750 with 10psi has a higher dynamic compression ratio then my kawasaki with 15psi..

[Ilja]

This one also works though less advanced.. shows cranking psi.

http://www.wallaceracing.com/dynamic-cr.php

[Ilja]

So after researching this dynamic compression ratio stuff, I think that the Kawi gpz750 turbo ignition which im using on my CB is not really suitable.

The gpz750 stock has (much) wilder cams and shorter stroke which bleeds of a lot of peak cylinder pressure.
Also, because of the shorter stroke it theoretically needs more advance because of the piston position to TDC and slower piston speed.

An engine needs to have a completed burn at 15-20 degrees past TDC and is normally tuned for MBT (Max Brake Torque) on a dyno for the optimal ignition advance position.
( https://en.wikipedia.org/wiki/Maximum_brake_torque )

If the burn finishes too soon (with for example too much advance) you will create a huge cylinder pressure peak because the piston has to work against it, thats why we retard ignition timing.
If you have a boosted engine, the combustion is even faster...

So basically an ignition with boost reference would be a solution for my CB... but where to find an affordable one.. I don't want to spend 500 euro's for a dyna 2000 which only switches retard. I want to program it myself.

Well, I found this great company: http://www.ignitech.cz/en/vyrobky/tcip/tcip.htm

These ignitions are a fraction of the price of the Dyna's and you can program EVERYTHING.
Just download the software of the page and you can see it for yourself...

Ignition advance table vs RPM & Pressure
or Ignition advance vs RPM and TPS for non-turbo bikes
Rev limiter
Switched retard or quickshift
3D map
Etc etc..

I've ordered one for the CB... as I still want to run 15psi instead of 10 ..but reliable. 
Might as well make use of the excellent torque characteristics of the CB engine and tune out the "5000-6500rpm detonation danger zone" with the ignition.

[Ilja]

Another interesting thing I've bought is a dual port wastegate actuator.
I didnt want an external wastegate for this bike so I tried to boost control it the cheap way "easy" way with a "ball & spring" controller like everyone does, but it sucked. So glad I found this one that replaces my stock actuator.

Right now I have one with a single port. The pressure line goes from the turbo compressor house to the 2/3 port solenoid and then I can switch on my handlebar between going directly to the single port actuator, or via a "ball&screw" type boostcontroller.
Effectively having two boost posibilities, stock wastegate pressure and adjustable pressure.

The problem with this is... it spikes. It spikes because the pressure is only passing the ball & screw regulator when the pre-set value is reached and then starts filling the actuator too late, so you end up with a boost spike. (you can also see that in my dyno graph). This is not good especially at higher boost...


So with the two-port actuator (bought from "turbonetics) you can make a more stable setup. It's basically the same as what you get with an external wastegate.
You can have one boost line directly from the turbo compressor to the top port, and then another boost line with a T piece and a pneumatic pressure regulator (like on your home workshop compressor) to the other port.
With the pneumatic pressure regulator you can set an amount of pressure to the other port, working against the stock spring pressure.

The amount you set with the pressure regulator is relative to the amount of additional boost you get... and no boost spiking because it lets air through straight away, but cuts it off at set pressure instead of the other way around.

You can add again a 2/3 solenoid with a switch on the line with the regulator and you have a perfect dual stage boost controller setup with no spiking. 
I have it set like this on my other bike with an external wastegate with great success.

I've sketched a small illustration for future reference in case anyone else starts needs it. 

[scottly]

Have you put the re-built motor on the dyno yet?

[Ilja]

So the weather has been really #$%*ty lately and i've been busy traveling for work. So not much new has been done on my favourite bike. Programmable ignition and two port wastegate actuator are still waiting in a box.

I did however take the bike out for one last pre-winter ride! Didnt baby it and raced the bike around for an hour or so.. had the handlebar in my face a few times as the front comes up in 1st gear very easily.

I cant get over how well this engine works with 836cc, keihin 32cv carbs, f2 head, intercooler and the gt17 turbo.
Its a perfect high power street bike with a huge powerband for a turbo, fun starts at 4000rpm! I think it really has to do with the long stroke and short duration camshaft. You probably cant run huge boost but in return the engine works very well on the street.

Didnt have it on the dyno yet as I first want to install the new ignition and turbo actuator. Ideally I want to dyno it at 10 and 15psi. Will need to wait to 2017. 

[Ilja]

So anybody whos still in doubt about building a hairblower cb, do it! It works great and is very rewarding!
Besides, the R&D work has already been done. 

[540nova]

What do you estimate the horse power to be?


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[Ilja]

What do you estimate the horse power to be?


Sent from my iPhone using Tapatalk

Between 130 and 150hp @10psi at the moment.

[754]

Rick Racer has a set of new turbo pistons for sale, look in the ebay craigs section fir his Lester mags auction, then click other items.