Honda CBX 1350 Fuel Injected - Speakers UP!!

[EMS]

Here's what I was told, way back when, by a muscle car guy.
"Torque is what gets you off the line
Horse Power is what makes you move fast."

Next time ask a mechanical engineer or a physicist and see what answer you get.

Here is a mechanical engineer. Mouse is correct. In simple terms, torque produces acceleration (and seat-of-the-pants feel), horsepower is an indication of how well the vehicle can sustain higher speeds.
If you look at a torque and horsepower chart, the further apart the peak values for torque and horsepower are, the more "elasticity" your engine has. This translates into the "roll-on performance" that is sometimes quoted in tests 9time to accelerate from (25 - 85mph, e.g.)

[rperacing]

EMS,

Question:
How do you explain that the dyno dynamics dyno does not show torque when there is no rpm input and yet shows hp, exactly the same value if the rpm input was configured correctly?

Not being a smart ass, just my experience.

[Rick Pope]

I think (alway dangerous) Mike (EMS) was making reference to the formula to calculate horsepower: rpm x torque, measured in lb/ft, divided by 5252 = hp.

The dynos I've been around don't measure hp, just acceleration rates against a known resistance. Everything else is calculated from there.

[Syscrush]

Back on the topic of this EFI build...

You mentioned that closed-loop would be doable, just more complicated. Is that extra complication more hardware (like a lambda sensor or a more sophisticated ECU), more tuning effort, or both?

I know you don't want cats on your bike, but do you think that in closed-loop operation an aftermarket ECU on these old air-cooled engines could create AFR's that are in the right range and stable enough to allow the use of a catalytic convertor without poisoning it? What would be the limiting factors?

[rperacing]

Back on the topic of this EFI build...

You mentioned that closed-loop would be doable, just more complicated. Is that extra complication more hardware (like a lambda sensor or a more sophisticated ECU), more tuning effort, or both?

I know you don't want cats on your bike, but do you think that in closed-loop operation an aftermarket ECU on these old air-cooled engines could create AFR's that are in the right range and stable enough to allow the use of a catalytic convertor without poisoning it? What would be the limiting factors?

Yes you would need an extra lambda sensor. Weather or not you need a lambda sensor controller depends on the ECU some have O2 built in control (heater, diagnostics, etc - Motec and many others) while some don´t - Haltech and many others. None of this is an issue or complicated in a special way. I would say tuning gets easier with closed loop.

For example, our ECU, the Sprint 500 is a very basic one, does not provide CL operation. If we did it again we would probably use the Elite 750 which has CL. It also has auto tuning of fuel table, long term fuel trims... A setup like this will get you lambda=1 when you ask for it, considering the sensor is at operating temperature and in good condition. No reason why the results would be any worse than an OEM application (on the fueling side of things at least).

We have found the hardest part was the hardware side of things, mainly the throttle bodies. Getting them balanced is difficult because they are cobbled together from 2 sets of 4 and also catilevered...

[Syscrush]

I'm wondering if a custom manifold and slide throttle might be a viable solution - these have become somewhat popular with the RX-7 crowd when they run peripheral port converted engines. This is a good example of that approach:



Slide parts. The black slide is made of teflon, but he changed it to Al on roller bearings since the Teflon slide can stick (including sticking open) as a result of the large pressure differential across the throttle.


Slide in place.


Fuel rail and intake ports.


Whole intake in place.


It would take a wacky linkage to operate 2 of these with 3 holes each in a V shape, but IMO it's a design that has some merit.

[rperacing]

Well that is a very elegant solution! I have heard of it but first time I saw the real deal.

I imagine that it takes trial and error as anything in life to get it to work but it is no different than flat slide carbs. Another plus is that the cylinder balance is perfect by design. Also looks quite slim.

I would avoid the 'kink' at all cost - no good would come from there

I would try and find some rubber elbows and cut the desired angle to match to the stock runners. Or cut the head runners and weld straight ones on there. We have done that.

We do that a lot on race CBs as they have a shit runner size stock. The CBX is not bad though.

Food for though indeed

[Syscrush]

How do you feel about weighing in on the following thread?
Claimed 200 whp CBX

Your CBX engine building prowess was a subject of some discussion before you joined up and posted this 1350 EFI machine.

[rperacing]

I did not read the whole thread but I am familiar with the bike. We built it after all.

This is our second most powerful CBX to date (not to say we cannot go further - in fact we will ). Those dyno results were inflated - they were taken at another workshop that has a dynojet. For some reason it reads really high. We got our own dyno now so no more issues.

This bikes puts out 140 - 145whp on our dyno.

For comparison:
2007 R1 - 155 whp with pipe and commander
Stock FZR 1000 - 120 whp
LS1 - 300 whp

I rate that engine at 160 - 170hp. Video and dyno graph (in the end) here:
https://www.youtube.com/watch?v=4N9A5MZ ... Fs&index=2

I wasn't around when thread was going and dont want to reignite the fire as "the customer is always right". In his defense that bike, on that day on that dyno put out that horsepower. Do I believe the number - no.

Still damn proud of it though. Shame there isn't much competition about. We have got a something special in the pipeline, just in case.



Paulo

[BiKenG]

I did not read the whole thread but I am familiar with the bike. We built it after all.
...
I wasn't around when thread was going and dont want to reignite the fire as "the customer is always right". In his defense that bike, on that day on that dyno put out that horsepower. Do I believe the number - no.

Still damn proud of it though. Shame there isn't much competition about. We have got a something special in the pipeline, just in case.

A rather old thread now, but having read through this and the 225 hp thread, there is still an unanswered question in my mind:-

How much bigger can you go without having to bore the cases?

The original liners are apparently 71mm OD, but if I recall correctly they're not a tight fit in the cases. So how big a liner can you use before having to bore out the cases?

I built a CBX engine many years ago with some parts HRC (or might have been RSC then) produced when they thought a CBX could be used for racing. There was a 999 kit to suit a 1000cc capacity limit, a 1200 kit and a 1350 (I think) kit. There were cams and rods, but not all kits used the latter. For the life of me now I cannot remember whether I had the 1200 or 1350 barrel. I do remember that it used the same pistons as the 4 cylinder F1 race bikes of the time. These were based on the 750 rather then the 900 for its shorter stroke and the pistons would have been about 71.5 and I would have had the 1200 kit barrel, but I cannot remember the exact specifics. However, I'm sure I didn't have to bore out the crankcases.

So as the builder of the big CBXs mentioned in this thread, perhaps rperacing could confirm just how big is the opening in the cases and so what size liners can be fitted to stock cases.

[EMS]

The original liners are apparently 71mm OD, but if I recall correctly they're not a tight fit in the cases. So how big a liner can you use before having to bore out the cases?

... what size liners can be fitted to stock cases.

Not sure that I understand your question. The liners do not flap around in the cases. They have a press fit.
If you want to use a liner that has a larger OD than the stock liner, you will have to bore the cases.
I did a 72mm bore CBX block and the liner OD was around 75mm. We had to bore the cases to fit these.

[daves79x]

Think he means that the liners are not an extremely tight fit when installing the block onto the cases - not the liner fit into the block.

Dave

[BiKenG]

The original liners are apparently 71mm OD, but if I recall correctly they're not a tight fit in the cases. So how big a liner can you use before having to bore out the cases?

... what size liners can be fitted to stock cases.

Not sure that I understand your question. The liners do not flap around in the cases. They have a press fit.
If you want to use a liner that has a larger OD than the stock liner, you will have to bore the cases.
I did a 72mm bore CBX block and the liner OD was around 75mm. We had to bore the cases to fit these.

Are you referring to the block/barrels/cylinders or the crankcases? Of course the liners are a tight fit in the cylinder/barrels, but they are never a tight fit in the crankcase opening as the cylinders have to be easily removable from the crankcases. To get any significant increase in capacity the liners will undoubtedly have to be removed from the cylinders which are then bored and larger liners fitted. But what is the size of the hole in the crankcases? How large can the liner be before the crankcases have to be bored out to accept the larger liner?

Or are people confusing the crankcase with the barrels/cylinders?

[BiKenG]

...We thought about a budget solution but nowhere near ready. It would involve a modular design where you join them side by side to whatever pitch you want.
...

Did these ever materialise? The idea of modular throttle bodies that can be connected in groups of however many you need sounds mighty attractive.

[FalldownPhil]

If my memory is working this morning ( maybe & Maybe not) anything with pistons over 68mm will require bigger liners.
That will require the top case to be opened up to hold the larger liners.
Best,
Phil