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Offline Ilja

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Re: Turbo Billet Block CB750
« Reply #25 on: September 22, 2018, 02:05:51 am »
Is that the special "turbo cam" from megacycle? With no overlap but more lift?

Nice...  8)

Offline MRieck

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Re: Turbo Billet Block CB750
« Reply #26 on: September 22, 2018, 06:17:22 am »
Is that the special "turbo cam" from megacycle? With no overlap but more lift?

Nice...  8)
Yes....the Norris turbo profile. Very interesting to look at.
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Offline Ilja

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Re: Turbo Billet Block CB750
« Reply #27 on: September 23, 2018, 04:58:41 am »
They look like my z650 / gpz 750 turbo cams... but those are shim-under-bucket ones so without rockers / rocker-ratio.  ;D

I see that the specs show only 5 degrees reduced duration on intake and exhaust, but the shape op the sharper lobe says that it will hold the valve open less long around maximum lift.
I think it will feel very strong throughout low and mid for a turbo-charged engine with this cam thats for sure.
I think classic lower compression pistons (8:1) are also needed with this timing.

But I'm curious to see what it will do on top-end, I don't know if it will be better, worse or the same... hard to predict.

Offline MRieck

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Re: Turbo Billet Block CB750
« Reply #28 on: September 23, 2018, 03:07:30 pm »
They look like my z650 / gpz 750 turbo cams... but those are shim-under-bucket ones so without rockers / rocker-ratio.  ;D

I see that the specs show only 5 degrees reduced duration on intake and exhaust, but the shape op the sharper lobe says that it will hold the valve open less long around maximum lift.
I think it will feel very strong throughout low and mid for a turbo-charged engine with this cam thats for sure.
I think classic lower compression pistons (8:1) are also needed with this timing.

But I'm curious to see what it will do on top-end, I don't know if it will be better, worse or the same... hard to predict.
We'll see. ;D ;D
Owner of the "Million Dollar CB"

Offline Cb750 Racer

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Re: Turbo Billet Block CB750
« Reply #29 on: October 21, 2018, 02:18:46 pm »
They look like my z650 / gpz 750 turbo cams... but those are shim-under-bucket ones so without rockers / rocker-ratio.  ;D

I see that the specs show only 5 degrees reduced duration on intake and exhaust, but the shape op the sharper lobe says that it will hold the valve open less long around maximum lift.
I think it will feel very strong throughout low and mid for a turbo-charged engine with this cam thats for sure.
I think classic lower compression pistons (8:1) are also needed with this timing.

But I'm curious to see what it will do on top-end, I don't know if it will be better, worse or the same... hard to predict.
We'll see. ;D ;D
Will be interesting to see the final results for sure!  :)
A lot of progress has been going on behind the scenes even though I haven't posted much. Making these posts is tiring

Got the transmission all cleaned up and replaced every single transmission bearing. New bearings where possible and Kennys super finished bearings for the grooved bearings as they are no longer made. Also have a one year only (k6 I believe) final drive setup which is the early style but it is solid like the later units. Also have a Cycle X primary chain tensioner.



Using a set of Cycle X primary chains I have had sitting around for many months. They will certainly be put to the test  :D




APE main studs as well


Got all the rods in this past week. When I actually torqued the rods the feeler gauges were perpendicular to the way I have them set up in the picture so please ignore that.


Sealed the cases shortly after getting the rods finished up. Was up until 4 in the morning getting this short block together it was like one of those interrigation rooms with no windows that make you lose track of time. I could have swore it was only 1am but


Brought the short block over to Mikes this weekend to get final measurements for the head/base gasket. Mike figures a 0.040 copper base gasket and a 0.040 copper head gasket will be proper. The block was shaved a bit more than we thought but will be a sweet setup nonetheless.I forget to ask Mike what i'm looking in terms of compression with this gasket setup, hopefully just under 9 to 1 like we had discussed awhile back.Mike also set the ring gap while I was there to 0.014 for the top ring and 0.015 for the 2nd ring.Very grateful to have Mike helping me out with this build all his little tips and tricks he's accumulated over the years makes his work a cut above the rest.
« Last Edit: October 22, 2018, 04:21:01 pm by Cb750 Racer »
1972 Honda CB750 AAMRR Racer
1972 Suzuki GT750 Project
1975 Honda CB400f
1981 Kawasaki KZ750 LTD
1984 Kawasaki GPZ550 =>610cc
1996 Honda CR500

Offline Bill/BentON Racing

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Re: Turbo Billet Block CB750
« Reply #30 on: October 23, 2018, 06:40:08 pm »
Gotta be nice to have Mike close by..... ;D
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Over 35 years of experience working on vintage motorcycles, with a speciality in Honda SOHC/4 with a focus on the CB750 and other models as well from 1966 - 1985.
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1993 HRC RS125 | 1984 NS400R | 1974 Honda CB750/836cc (Calendar Girl) | 1972 CB 500/550 Yoshi Kitted 590cc | 1965 Honda CB450 Black Bomber | 1972 Suzuki T350 | 1973 88cc | Z50/Falcons Pit Bike | 1967 CA100| 1974 CB350 (400F motor)...and more.
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Offline MRieck

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Re: Turbo Billet Block CB750
« Reply #31 on: October 23, 2018, 06:57:50 pm »
Gotta be nice to have Mike close by..... ;D
Jutin doen't live to far away Bill...little over an hour I believe.
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Offline calj737

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Re: Turbo Billet Block CB750
« Reply #32 on: October 24, 2018, 03:32:45 am »
Gotta be nice to have Mike close by..... ;D
Would be a wet dream to be sandwiched between you and Mike on the same block!  :-*
'74 550 Build http://forums.sohc4.net/index.php?topic=126401.0
'73 500 Build http://forums.sohc4.net/index.php?topic=132935.0

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Offline Cb750 Racer

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Re: Turbo Billet Block CB750
« Reply #33 on: October 24, 2018, 06:05:31 pm »
Gotta be nice to have Mike close by..... ;D
Would be a wet dream to be sandwiched between you and Mike on the same block!  :-*
don't get too hasty i'm broke enough just having Mike close by  ;D It is very nice having Mrieck about an hour away though my build probably wouldn't be what it is today if Mike was any farther. I was hesitant about the billet block until I saw it in person, It really is worth it!Having you two within an hour would make me a very poor and blinged out man.
1972 Honda CB750 AAMRR Racer
1972 Suzuki GT750 Project
1975 Honda CB400f
1981 Kawasaki KZ750 LTD
1984 Kawasaki GPZ550 =>610cc
1996 Honda CR500

Offline Medyo Bastos

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Re: Turbo Billet Block CB750
« Reply #34 on: October 25, 2018, 04:17:29 am »



[/quote]
Would be a wet dream to be sandwiched between you and Mike on the same block!  :-*
[/quote]


you might want to keep that to yourself, pervert!
« Last Edit: October 25, 2018, 04:19:39 am by Medyo Bastos »

Offline calj737

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Re: Turbo Billet Block CB750
« Reply #35 on: October 25, 2018, 04:23:14 am »
Would be a wet dream to be sandwiched between you and Mike on the same block!  :-*
Quote
you might want to keep that to yourself, pervert!
Embarrassed I was reading your mind?  ;D
Okay, would be a Honda Dream to be sandwiched.... Better?  8)
« Last Edit: October 29, 2018, 03:08:35 am by calj737 »
'74 550 Build http://forums.sohc4.net/index.php?topic=126401.0
'73 500 Build http://forums.sohc4.net/index.php?topic=132935.0

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Offline PeWe

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Re: Turbo Billet Block CB750
« Reply #36 on: October 25, 2018, 10:25:33 am »
The "normal" Honda dream is a sandcast..... ;)
This forum is where the ideas hatch and nice parts can be shipped worldwide. Mike is very helpful :) I live a week or 2 away via USPS and my local postal service.
If Mike get many visitors, he might start to put them into work in his shop! ;) Free labor in exchange of some engine guidelines hot to and not..
CB750 K6-76 1005cc JMR Billet block.
CB750 K2-75 stock looking project started 2017

Offline Ilja

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Re: Turbo Billet Block CB750
« Reply #37 on: October 29, 2018, 03:01:58 am »
They look like my z650 / gpz 750 turbo cams... but those are shim-under-bucket ones so without rockers / rocker-ratio.  ;D

I see that the specs show only 5 degrees reduced duration on intake and exhaust, but the shape op the sharper lobe says that it will hold the valve open less long around maximum lift.
I think it will feel very strong throughout low and mid for a turbo-charged engine with this cam thats for sure.
I think classic lower compression pistons (8:1) are also needed with this timing.

But I'm curious to see what it will do on top-end, I don't know if it will be better, worse or the same... hard to predict.
We'll see. ;D ;D
Will be interesting to see the final results for sure!  :)
A lot of progress has been going on behind the scenes even though I haven't posted much. Making these posts is tiring

Got the transmission all cleaned up and replaced every single transmission bearing. New bearings where possible and Kennys super finished bearings for the grooved bearings as they are no longer made. Also have a one year only (k6 I believe) final drive setup which is the early style but it is solid like the later units. Also have a Cycle X primary chain tensioner.


Looking good!

Be carefull with 9:1 and boost and that short cam timing. Not meaning to critisize but 8:1 would be more safe, as my pistons found out in the beginning. :(
I think for 9:1 around 0.5 bar / 7psi is the limit, maybe a bit more with boost ignition retard but it's on the edge and will ping more easily if boost spikes.
For my engine I setup the ignition so it retards to 20 degrees when boost goes over 15psi, as a safety measure for boost spikes or wastegate failure.

When I ran almost 9:1, crappy squish and probably one bad piston, 7psi gave me around 85hp
and 10psi gave me almost 100hp at 6500rpm and 110hp up top...but it misfired at higher rpm on the dyno. :-)

Later on I installed the F2 head with lower compression but bigger valves, better ignition, normal squish and intercooler. So possibly it has more but never tested again.

And I spent many evenings past midnight in the garage during building, it's so addictive.  ;D
 

« Last Edit: October 29, 2018, 03:09:03 am by Ilja »

Offline Cb750 Racer

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Re: Turbo Billet Block CB750
« Reply #38 on: December 01, 2018, 01:12:50 pm »
They look like my z650 / gpz 750 turbo cams... but those are shim-under-bucket ones so without rockers / rocker-ratio.  ;D

I see that the specs show only 5 degrees reduced duration on intake and exhaust, but the shape op the sharper lobe says that it will hold the valve open less long around maximum lift.
I think it will feel very strong throughout low and mid for a turbo-charged engine with this cam thats for sure.
I think classic lower compression pistons (8:1) are also needed with this timing.

But I'm curious to see what it will do on top-end, I don't know if it will be better, worse or the same... hard to predict.
We'll see. ;D ;D
Will be interesting to see the final results for sure!  :)
A lot of progress has been going on behind the scenes even though I haven't posted much. Making these posts is tiring

Got the transmission all cleaned up and replaced every single transmission bearing. New bearings where possible and Kennys super finished bearings for the grooved bearings as they are no longer made. Also have a one year only (k6 I believe) final drive setup which is the early style but it is solid like the later units. Also have a Cycle X primary chain tensioner.


Looking good!

Be carefull with 9:1 and boost and that short cam timing. Not meaning to critisize but 8:1 would be more safe, as my pistons found out in the beginning. :(
I think for 9:1 around 0.5 bar / 7psi is the limit, maybe a bit more with boost ignition retard but it's on the edge and will ping more easily if boost spikes.
For my engine I setup the ignition so it retards to 20 degrees when boost goes over 15psi, as a safety measure for boost spikes or wastegate failure.

When I ran almost 9:1, crappy squish and probably one bad piston, 7psi gave me around 85hp
and 10psi gave me almost 100hp at 6500rpm and 110hp up top...but it misfired at higher rpm on the dyno. :-)

Later on I installed the F2 head with lower compression but bigger valves, better ignition, normal squish and intercooler. So possibly it has more but never tested again.

And I spent many evenings past midnight in the garage during building, it's so addictive.  ;D

You're right and I don't mind the criticism at all. I believe Mike calculated about 8.8:1 with the gaskets we got but that didn't account the valve reliefs which had to be enlarged for the large F2 valves as well.So compression will be a hair less from even that calculation. 10psi on the streets would make me a happy man I think with a large oil cooler along with proper ignition and fuel control it should be safe. I'd love to see your setup on the dyno before you take it all apart! I'm sorry to hear about the emission problems in your country in the states you can register just about anything with a vin number
1972 Honda CB750 AAMRR Racer
1972 Suzuki GT750 Project
1975 Honda CB400f
1981 Kawasaki KZ750 LTD
1984 Kawasaki GPZ550 =>610cc
1996 Honda CR500

Offline MRieck

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Re: Turbo Billet Block CB750
« Reply #39 on: December 01, 2018, 05:33:08 pm »

 Never underestimate what $hitty squish will do to an engine....NA, nitrous oxide or forced induction.
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Offline Jim F

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Re: Turbo Billet Block CB750
« Reply #40 on: December 05, 2018, 03:38:19 am »
And I thought I had a lot of money in my turbo build
Wow
Jim
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Offline PeWe

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Re: Turbo Billet Block CB750
« Reply #41 on: December 06, 2018, 03:05:20 am »
It is amazing how much power a turbo can add. Must be cheapest hp, torque/$.
CB750 K6-76 1005cc JMR Billet block.
CB750 K2-75 stock looking project started 2017

Offline Ilja

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Re: Turbo Billet Block CB750
« Reply #42 on: December 06, 2018, 10:28:06 am »
It is amazing how much power a turbo can add. Must be cheapest hp, torque/$.

Basically as a rule of thumb is 2x N.A power with 10psi boost (with a turbo thats efficient at lower boost), on almost anything just with proper fueling and lower compression. :-)

But you always loose a bit of responsiveness, it becomes more like a "startrek enterprise" kinda bike. But very very fun!  ;D
Especially the CB with it's long stroke and mild engine tuning was a still very docile with that power, good bottom end and great to tour around also.

The reason I can't get the turbo in the papers (easily) is because the vehicle inspection wants to do a before :o & after dyno run at their dyno to determine the new power @ the crank. And thats not really possible as too many things have changed.
.. they started that because of all the lighter bike categories nowadays (15, 25 and 35kw) so the procedure is more about placing restrictors normally....

As I am #$%* poor on time nowadays I want to focus on my other two turbo bikes which are legal and just make the CB nice with RS34 carbs, 836 10:1, OS valves, bakker alu swingarm and a titanium 4-4 pipe...and just use it for the evening rides and to look at the beautifull bike it is...becoming.  :P I have everything except the titanium pipe and the RS34 carbs, that will be a project for next year.

It's just that you have to make decisions... but just wait untill the boost hits you the first time, it's a fantastic feeling. :)

« Last Edit: December 06, 2018, 03:13:18 pm by Ilja »

Offline PeWe

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Re: Turbo Billet Block CB750
« Reply #43 on: December 06, 2018, 11:10:57 am »
I did the last vehicle inspection ever with my CB750 K6 this year.  I need to let them inspect my CB750 K2 when ready. After than no more.
They changed the rules last year for old vehicles. No more fiddling with exhaust to reduce the sound for the inspection.
Or  remove turbo if having any.
The inspection guy really enjoyed the test ride and did not complain about the almost double hp. But, he must been used to modern bikes with 150-200 hp so a modified old CB750 with a fat cylinder block did not matter.
CB750 K6-76 1005cc JMR Billet block.
CB750 K2-75 stock looking project started 2017

Offline Ilja

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Re: Turbo Billet Block CB750
« Reply #44 on: December 06, 2018, 11:21:54 am »
I did the last vehicle inspection ever with my CB750 K6 this year.  I need to let them inspect my CB750 K2 when ready. After than no more.
They changed the rules last year for old vehicles. No more fiddling with exhaust to reduce the sound for the inspection.
Or  remove turbo if having any.
The inspection guy really enjoyed the test ride and did not complain about the almost double hp. But, he must been used to modern bikes with 150-200 hp so a modified old CB750 with a fat cylinder block did not matter.

@Pewe We don't have annual vehicle inspection and stuff...we only pay ~50 euro insurance for old bikes and nothing else needs to be done or paid. 
It's just for insurance and the official bike papers... officially power can be off 20%..but I could get screwed if I crash it into someone... as it's easily a point of discussion if insurance needs to pay someone's salary.   ;
)



@CB750 Racer: By the way what was the base engine type and what is the size of the cylinders? And did you use an F2 head? Or K/F?
Oh wait... 72mm.

If you have an F2 head, 72mm pistons with a 1cc dome (estimate by eye ;) ) and a 1.1mm squish height / headgasket thickness at about 0 deckheight you should be at 9.2:1
Squish I would aim for 1.1-1.3mm, otherwise it stops being effective as gas pockets can form around the edges.

This is an easy calculator: http://www.summitracing.com/newsandevents/calcsandtools/compression-calculator
« Last Edit: December 06, 2018, 11:51:34 am by Ilja »

Offline Cb750 Racer

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Re: Turbo Billet Block CB750
« Reply #45 on: December 06, 2018, 02:04:33 pm »
It is amazing how much power a turbo can add. Must be cheapest hp, torque/$.
Very true Nitrohunter is a good example of what can be done with one of these kits on close to stock engine. Though this build is aiming for a bit more reliability  ;)

And I thought I had a lot of money in my turbo build
Wow
Jim

Sadly I don't think my build will reach the level of class your bike carries. Your setup is cleannnn!

It is amazing how much power a turbo can add. Must be cheapest hp, torque/$.

Basically as a rule of thumb is 2x N.A power with 7-10psi boost, on almost anything just with proper fueling and lower compression. :-)

But you always loose a bit of responsiveness, it becomes more like a "startrek enterprise" kinda bike. But very very fun!  ;D
Especially the CB with it's long stroke and mild engine tuning was a still very docile with that power, good bottom end and great to tour around also.

The reason I can't get the turbo in the papers (easily) is because the vehicle inspection wants to do a before :o & after dyno run at their dyno to determine the new power @ the crank. And thats not really possible as too many things have changed.
.. they started that because of all the lighter bike categories nowadays (15, 25 and 35kw) so the procedure is more about placing restrictors normally....

As I am #$%* poor on time nowadays I want to focus on my other two turbo bikes which are legal and just make the CB nice with RS34 carbs, 836 10:1, OS valves, bakker alu swingarm and a titanium 4-4 pipe...and just use it for the evening rides and to look at the beautifull bike it is...becoming.  :P I have everything except the titanium pipe and the RS34 carbs, that will be a project for next year.

It's just that you have to make decisions... but just wait untill the boost hits you the first time, it's a fantastic feeling. :)


I hate to see you take the turbo off! Though the bike will still be awesome with the setup you're planning anyway  :D
This engine would have no problem making 80+hp with just a set of round-top carbs and a 4 into 1 exhaust. 10lbs of boost is going be a bit rowdy on the streets for sure I'm hoping for 130hp but we'll see how that makes sense in terms of reliability. I believe the common rule of thumb is 1bar doubles the N/A power rather than 7-10lbs.

I did the last vehicle inspection ever with my CB750 K6 this year.  I need to let them inspect my CB750 K2 when ready. After than no more.
They changed the rules last year for old vehicles. No more fiddling with exhaust to reduce the sound for the inspection.
Or  remove turbo if having any.
The inspection guy really enjoyed the test ride and did not complain about the almost double hp. But, he must been used to modern bikes with 150-200 hp so a modified old CB750 with a fat cylinder block did not matter.

@Pewe We don't have annual vehicle inspection and stuff...we only pay ~50 euro insurance for old bikes and nothing else needs to be done or paid. 
It's just for insurance and the official bike papers... officially power can be off 20%..but I could get screwed if I crash it into someone... as it's easily a point of discussion if insurance needs to pay someone's salary.   ;
)



@CB750 Racer: By the way what was the base engine type and what is the size of the cylinders? And did you use an F2 head? Or K/F?
Oh wait... 72mm.

If you have an F2 head, 72mm pistons with a 1cc dome (estimate by eye ;) ) and a 1.1mm squish height / headgasket thickness at about 0 deckheight you should be at 9.2:1
Squish I would aim for 1.1-1.3mm, otherwise it stops being effective as gas pockets can form around the edges.

This is an easy calculator: http://www.summitracing.com/newsandevents/calcsandtools/compression-calculator
Correct the head is an F2 . The pistons are 72mm Wiseco from Cycle X. They recently took them off the website but were labeled as "9:1 turbo" pistons though I'm not sure under what circumstances the 9:1 was measured. 1cc is probably accurate for the piston dome they're very minuscule. The beauty of Mikes block is the ability to change deck height by just changing a few numbers in the programming. Though Mike was really adamant about having a tiny squish for the same reason you mentioned above so I can't imagine the block is too tall. Your numbers are right and honestly my 8.8:1 number may be off it's a very old figure from when this build was just an idea. I'm heading up to Mikes this weekend to pick my engine back up so i'll have to get some clarification on the squish/deck height.
« Last Edit: December 06, 2018, 02:12:11 pm by Cb750 Racer »
1972 Honda CB750 AAMRR Racer
1972 Suzuki GT750 Project
1975 Honda CB400f
1981 Kawasaki KZ750 LTD
1984 Kawasaki GPZ550 =>610cc
1996 Honda CR500

Offline Ilja

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Re: Turbo Billet Block CB750
« Reply #46 on: December 06, 2018, 04:38:38 pm »
Quote

This engine would have no problem making 80+hp with just a set of round-top carbs and a 4 into 1 exhaust. 10lbs of boost is going be a bit rowdy on the streets for sure I'm hoping for 130hp but we'll see how that makes sense in terms of reliability. I believe the common rule of thumb is 1bar doubles the N/A power rather than 7-10lbs.


10lbs is quite nice as it still doesn't add massive levels of heath... its in between the "racefuel, intercooling playing with fire" and "I can run a stock engine" level of engine requirements.
(At 10lbs if you calculate air will theoretically already be 100 degrees C or something just from compressing it.)

Important is first run it with 5-7lbs and then if fueling is ok slowly increase to 10lbs, as it can very well already ping at that amount of boost.
And be carefull the first time, finding out where the wastegate is set at. You can ride years at the right boost but destroy the pistons in 1 pull with too much boost... if it pings or becomes too hot ;D

I think the challenge of a draw through system is to get the fueling correct.. the combination for bottom end for ridability and to keep it from leaning out at WOT.
They tend to use massive main jets and makes it hard to jet it correctly at part load. Going slow testing and tuning the bike will be important!

At 10lbs I think you should definitly be able to get 130hp with that 1022cc engine, maybe more.. 8)
But the turbo has to flow enough air at a good efficiency at the dialed boost, and the cylinderhead has to be able to flow the air as well.

E.g. for the Garrett turbo's you can check the compressor maps which are available on the internet and you can check at what efficiency island the turbo will be at the amount of boost you will run with the desired amount of horsepower (airflow).

https://www.garrettmotion.com/racing-and-performance/performance-catalog/turbo/gt2052/

Roughly multiply the lbs/min under the x-axis with 10 to get the amount of horsepower the airflow can provide.
On the Y-axis you can see the pressure ratio... a ratio of 2 is 15psi of boost (14.7psi athmosferic + 14.7 boost). So you can see for that GT2052 at 10psi or 1.75 PR you are right in the middle of the efficiency island at WOT if your engine makes 150hp. This means a good performing turbo charger with cool air. :)
You don't want to be left of the graph as there your turbo would be surging, and the right edge of the graph is where it runs out of steam/doesn't make anymore power. 


About tuning turbo engines.... mine added 10hp per lbs after 7lbs, so dialing in 2lbs more can already result in 20hp extra as long as the turbo can flow the amount of air required at a good efficiency for the amount of boost. Thats why other engine tuning tricks are less important with a blown engine... the gain is too small compared to just increasing boost.

If the turbo is too small, it will make boost by generating heat and the power won't increase anymore... that's also one thing to keep in mind.

I don't know where the "roof" is on these engines... e.g. with the gpz750, a GT2056 turbo (or equivalent) proper fueling and the rest about stock 150hp is achieved by lots of people at about 13-15psi. Also 200hp at 22psi with the stock 750cc turbo pistons at 7.8:1 has been achieved by some people (I have the same setup). 

So the CB should also be able to get also 130-150hp I think, don't worry about that...  :)

Offline Cb750 Racer

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Re: Turbo Billet Block CB750
« Reply #47 on: December 06, 2018, 08:07:31 pm »
Quote

This engine would have no problem making 80+hp with just a set of round-top carbs and a 4 into 1 exhaust. 10lbs of boost is going be a bit rowdy on the streets for sure I'm hoping for 130hp but we'll see how that makes sense in terms of reliability. I believe the common rule of thumb is 1bar doubles the N/A power rather than 7-10lbs.


10lbs is quite nice as it still doesn't add massive levels of heath... its in between the "racefuel, intercooling playing with fire" and "I can run a stock engine" level of engine requirements.
(At 10lbs if you calculate air will theoretically already be 100 degrees C or something just from compressing it.)

Important is first run it with 5-7lbs and then if fueling is ok slowly increase to 10lbs, as it can very well already ping at that amount of boost.
And be carefull the first time, finding out where the wastegate is set at. You can ride years at the right boost but destroy the pistons in 1 pull with too much boost... if it pings or becomes too hot ;D

I think the challenge of a draw through system is to get the fueling correct.. the combination for bottom end for ridability and to keep it from leaning out at WOT.
They tend to use massive main jets and makes it hard to jet it correctly at part load. Going slow testing and tuning the bike will be important!

At 10lbs I think you should definitly be able to get 130hp with that 1022cc engine, maybe more.. 8)
But the turbo has to flow enough air at a good efficiency at the dialed boost, and the cylinderhead has to be able to flow the air as well.

E.g. for the Garrett turbo's you can check the compressor maps which are available on the internet and you can check at what efficiency island the turbo will be at the amount of boost you will run with the desired amount of horsepower (airflow).

https://www.garrettmotion.com/racing-and-performance/performance-catalog/turbo/gt2052/

Roughly multiply the lbs/min under the x-axis with 10 to get the amount of horsepower the airflow can provide.
On the Y-axis you can see the pressure ratio... a ratio of 2 is 15psi of boost (14.7psi athmosferic + 14.7 boost). So you can see for that GT2052 at 10psi or 1.75 PR you are right in the middle of the efficiency island at WOT if your engine makes 150hp. This means a good performing turbo charger with cool air. :)
You don't want to be left of the graph as there your turbo would be surging, and the right edge of the graph is where it runs out of steam/doesn't make anymore power. 


About tuning turbo engines.... mine added 10hp per lbs after 7lbs, so dialing in 2lbs more can already result in 20hp extra as long as the turbo can flow the amount of air required at a good efficiency for the amount of boost. Thats why other engine tuning tricks are less important with a blown engine... the gain is too small compared to just increasing boost.

If the turbo is too small, it will make boost by generating heat and the power won't increase anymore... that's also one thing to keep in mind.

I don't know where the "roof" is on these engines... e.g. with the gpz750, a GT2056 turbo (or equivalent) proper fueling and the rest about stock 150hp is achieved by lots of people at about 13-15psi. Also 200hp at 22psi with the stock 750cc turbo pistons at 7.8:1 has been achieved by some people (I have the same setup). 

So the CB should also be able to get also 130-150hp I think, don't worry about that...  :)

This is some amazing information. It's always nice to see an Ilja comment on the thread  :D

I came up with the 10lb number from just playing with effective compression ratio calculations Sqrt((10+14.7)/14.7)*8.8 ) = 11.40:1 CR which would I figured would be perfect for street use.

10lbs may not be so achievable assuming i'm near 0 deck height with about a 1.1m squish. Plugging that 9.2CR number you had mentioned earlier Sqrt((10+14.7)/14.7)*9.2) = 11.92 CR  puts me a bit higher than I would want to be on the streets. I can't imagine heat could escape fast enough even with a very large oil cooler and the nikasil billet block to safely run 12:1CR. That starts to get into racefuel territory as you stated before the air will already be 100+ degrees C just from compressing it.

The bike will get slowly dialed in I don't plan to make any boost on the first day :)  Once jetting is sorted to the best of my ability i'll ride over to the dyno for final fueling adjustments while creeping up on boost with a keen eye on the AFR guage. Timing will be set to somewhere around 24 degrees static initially. I'm interested to see how much the max brake torque number differs, of course backing it off a few degrees to account for pump fuel variation between pumps. The 10%ethanol content in the my local 93 octane pump fuel is a bit scary though i'm reluctant to use it because of the affects it could have on my engine/turbo seals after a few years. Getting the AFR where I want it all across the board is also going to be tricky no doubt, Cold starts are gonna be a pain in the ass especially being kickstart only.

I wish compressor maps could be found for my Rajay "F" series turbo. Only maps I have been able to find are Rajay "E" compressor maps which has a different blade design. It would be really helpful to know where the peak efficiency range lies, i'm going to make a few phone calls to Rajay and there parent company tomorrow and see what I can find. If anything my turbo is a bit large for the application i'm not sure if ill ever reach peak efficiency will even be seen with how little boost i'm running.But I guess that also leaves some room on the table. A gt2052 would be perfect for my setup had I gone blow through. You'd be right in the peak efficiency range with the boost I plan on running @WOT that setup would be the best case scenario. Now I just need you to modify your kit for the 2052 and i'll paypal you to ship it over the pond  ;) ;) ;)

130hp will be plenty for the streets though I have no doubt it could make much more than that. Not sure what the "roof" would be on this engine but the studs are only 8mm so that's certainly a limitation. A step deck setup with an mls headgasket would allow you to get some serious leak free power for cheap. Anything over 160hp wouldn't last too long you'd have to replace the final drive chains too often. There was rumor of a hilborn injected, dry clutch, and supercharged cb750 that was said to make over 150hp+ back in the 80's. Sorry for the blurry picture it was from a magazine back in the day.I have little to no information other than a picture that was sent from a friend.

1972 Honda CB750 AAMRR Racer
1972 Suzuki GT750 Project
1975 Honda CB400f
1981 Kawasaki KZ750 LTD
1984 Kawasaki GPZ550 =>610cc
1996 Honda CR500

Offline Cb750 Racer

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Re: Turbo Billet Block CB750
« Reply #48 on: December 07, 2018, 02:06:49 pm »
Finally the day I've been waiting months for have come. I finally scored a cb750 ATP intake manifold. Huge huge shoutout to Bill Benton i'd still be high and dry if it wasn't for him stepping in and helping me out. Hope all is well Bill!



You can see my ATP intake manifold is starting collection is getting there :) Just need a CBX manifold now  ;)




This manifold sits so much closer to the head than others that use the stock intake boots so it really allows me to suck everything up under that engine bay. It's gonna be very tight even with this trick manifold
1972 Honda CB750 AAMRR Racer
1972 Suzuki GT750 Project
1975 Honda CB400f
1981 Kawasaki KZ750 LTD
1984 Kawasaki GPZ550 =>610cc
1996 Honda CR500

Offline TurboD

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Re: Turbo Billet Block CB750
« Reply #49 on: December 12, 2018, 11:01:44 am »
Cb750 racer here you go, both E and F Rajay maps, along with different blade design the E wheel and compressor are larger. It has been my experience that on a big Kawasaki the smaller F setup will make almost 300rwhp, I would guess the E to be good for roughly another 100hp.

 

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