Highest power exhaust for GSX-R750 L1 2011-2023?

[ptuomov]

Narrower collector angles maybe? I'm a bit past my bed time but they look fairly steep

The angles look right to me, personally. The angle is a compromise between objectives, of course. This one mostly needs to see an area expansion at all collectors and also flow-induced vacuum at the last collector.

The simulator likes reducing the secondaries to the absolute minimum.

What’s surprising to me how good this ancient set is, no frills and bumpy torque curve under 11k rpm but makes good power above 11k rpm.

[Rick!]

What custom Yoshi exhaust do Team Classic Suzuki and Team Hammer use on their bikes? Seems they use Team Factory Suzuki Yoshi stuff.
One issue is that to homologate the 750 for racing, a drive by wire throttle assembly and an opening limit of 78% was imposed for closed course stuff. Your engine maybe has a throttle cable and that is not a concern.
It's interesting that the yosh exhaust pn is the same for both the 600 and 750...
Leo Vince exhaust with some aftermarket intake stacks might be worth a look?
Maybe look at the gsxr 600 exhaust for ideas as that combo seems to have a broad top end without falling on its face at 15k.
Lees Cycle Service in San Diego may have some race gixxer 750 information.
Okrapovich (Akrapovich) has a pdf of their racing exhaust - they use tapers and may bigger diameter secondaries...?
You've already modeled the 750 with the previous modded 600 exhaust - anything interesting there?
There are a few threads on the gixxer forum but the links to dyno graphs for hindle, yosh, and okrapovich are all junk.
Are any teams using paddle shifters? Human factors would lead one to believe that reducing the amount of hand/arm motion on the current shifter would lead to quicker shifting, hence more "on power" time for acceleration. That would need to be evaluated by the driver but it appears most driving is one-handed except for the really tight turns.
Your call; go down the exhaust development rabbit hole (where 5 or 6 aftermarket companies have already BTDT) or help the driver be more efficient. The real challenge will be how the team supports the kart after you're done with improvements. What's the schedule for top end renewal since banging off a raised rpm limiter will be commonplace? Maybe Spintron the valvetrain and find the golden valvespring that promotes a little loft?

[ptuomov]

I have found that motorcycle racing information is high quality but not applicable for this series. The torque curve shape appears to be way more important than the average power in motorcycle racing classes. This is not the case for me.

The engine retains the stock throttle system. The driver controls the primary throttle via a cable and the ECU controls the secondary throttle electronically. In the relevant rpms, the secondary throttles are 100% open.

The intake runner trumpets are settled science: use the shortest possible trumpets. Factory Pro doesn’t make 2011- 750 or 2014- 600 trumpets.

The Yoshimura exhaust in the pdf is surely a great motorcycle exhaust but, for my purposes, it’s inferior to the one in my photos because the secondaries are too long and the collector tuned distance also too long.

To best of my knowledge, paddle shifters are against the rules. They would improve lap times if allowed.

There’s a now set schedule by which we will rotate engines into the car. Individual cylinder fuel tune will further improve reliability. This is the first season the team will have a scheduled maintenance/replacement schedule for everything.

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What custom Yoshi exhaust do Team Classic Suzuki and Team Hammer use on their bikes? Seems they use Team Factory Suzuki Yoshi stuff.
One issue is that to homologate the 750 for racing, a drive by wire throttle assembly and an opening limit of 78% was imposed for closed course stuff. Your engine maybe has a throttle cable and that is not a concern.
It's interesting that the yosh exhaust pn is the same for both the 600 and 750...
Leo Vince exhaust with some aftermarket intake stacks might be worth a look?
Maybe look at the gsxr 600 exhaust for ideas as that combo seems to have a broad top end without falling on its face at 15k.
Lees Cycle Service in San Diego may have some race gixxer 750 information.
Okrapovich (Akrapovich) has a pdf of their racing exhaust - they use tapers and may bigger diameter secondaries...?
You've already modeled the 750 with the previous modded 600 exhaust - anything interesting there?
There are a few threads on the gixxer forum but the links to dyno graphs for hindle, yosh, and okrapovich are all junk.
Are any teams using paddle shifters? Human factors would lead one to believe that reducing the amount of hand/arm motion on the current shifter would lead to quicker shifting, hence more "on power" time for acceleration. That would need to be evaluated by the driver but it appears most driving is one-handed except for the really tight turns.
Your call; go down the exhaust development rabbit hole (where 5 or 6 aftermarket companies have already BTDT) or help the driver be more efficient. The real challenge will be how the team supports the kart after you're done with improvements. What's the schedule for top end renewal since banging off a raised rpm limiter will be commonplace? Maybe Spintron the valvetrain and find the golden valvespring that promotes a little loft?

[pcnsd]

It looks in many ways as if you are boxed by circumstance and previously achieved development plateaus. Have you looked at friction reduction (Ceramic bearings, transmission gear coatings, lighter drive chain and sprockets, oil pump blueprinting, oil passage refinement, lighter viscosity lubricants, total loss electrical, etc.)
Can you cheat and get away with it? What is the allowable overbore and SCR? Are you there? What if you stepped a bit beyond, how stringent is technical inspection? Are there claiming rules?
Further cylinder head development. Can the cylinder head be further optimized for combustion efficiency at the target rpm. Can you model the shapes and process?

[ptuomov]

It looks in many ways as if you are boxed by circumstance and previously achieved development plateaus. Have you looked at friction reduction (Ceramic bearings, transmission gear coatings, lighter drive chain and sprockets, oil pump blueprinting, oil passage refinement, lighter viscosity lubricants, total loss electrical, etc.)
Can you cheat and get away with it? What is the allowable overbore and SCR? Are you there? What if you stepped a bit beyond, how stringent is technical inspection? Are there claiming rules?
Further cylinder head development. Can the cylinder head be further optimized for combustion efficiency at the target rpm. Can you model the shapes and process?

Intake (upstream of the throttle body) and exhaust (downstream of the exhaust port flange) are free, everything else in the engine is stock by rules. Repairs are allowed if listed in the factory workshop manual. The oil viscosity has been optimized trading off speed and reliability, the car doesn't turn like a motorcycle and has an accusump to successfully bandaid oiling. Battery gets charged after every heat, electrical system doesn't eat much power.

Absolutely no need or desire to cheat as we have the fastest driver.

[juuhanaa]

It can be worthwhile to test the engine with the alternator and without/all electrics on. It can be surprising how bad can happen if the voltage drops too low, and having said that i wouldnt leave this thing untested again.

In addition with the alternator, you can possibly play with the battery weights without forgetting the advantage that comes into play when the car is brought to the line faster when it does not have to be charged between the heats.



-juhana

[ptuomov]

P=I*E, main fuse 30A and voltage 13.5, maximum power 405W or 0.54 horsepower. The motorcycle electrical system is an insignificant parasitic loss for this 160hp peak power engine.

[ptuomov]

This exhaust collector has the out pipe sticking out into the flow. There’s a clear lip, especially on the outside. Is this an intentional, performance improving feature or is it a manufacturing shortcut?

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[ptuomov]

The next question is whether the mid-pipe resonator actually improves performance or just alters the exhaust note.

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[pcnsd]

The next question is whether the mid-pipe resonator actually improves performance or just alters the exhaust note.

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Resonators usually are about narrow band sound. Usually, but in this case I would be afraid to change it unless guided by model simulation or the dyno output of someone who has been there.

[ptuomov]

The next question is whether the mid-pipe resonator actually improves performance or just alters the exhaust note.

Resonators usually are about narrow band sound. Usually, but in this case I would be afraid to change it unless guided by model simulation or the dyno output of someone who has been there.

Let’s see what the machine says.

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[ptuomov]

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.

Simulates the observed curve shapes pretty well.

[BLSTIC]

I can't see how those lips help. They stick in to proved a lip that will disrupt the "outside" 50% of the blowdown pulse from smoothly entering the merge.

UNLESS it's like those stupid lollipop things in harley exhausts, whose function is to "provide backpressure" disrupt pressure waves to destroy some anti-tune event.

Black line open exhaust, red with baffle, green was longer pipe

Screenshot_20231116-104926_Gallery.jpg

Ps my upload are coming up super bad on my screen. Can someone tell me if that screenshot i posted comes up properly?

[ptuomov]

The screenshot sucks hairy scrotum!

Thanks for the comments, I agree that those lips serve no useful purpose and should be ground out.

I can't see how those lips help. They stick in to proved a lip that will disrupt the "outside" 50% of the blowdown pulse from smoothly entering the merge.

UNLESS it's like those stupid lollipop things in harley exhausts, whose function is to "provide backpressure" disrupt pressure waves to destroy some anti-tune event.

Black line open exhaust, red with baffle, green was longer pipe

Screenshot_20231116-104926_Gallery.jpg


Ps my upload are coming up super bad on my screen. Can someone tell me if that screenshot i posted comes up properly?

[BLSTIC]

Black line - Short open pipe
Green line - Long open
Red line - disruption baffle in short pipe

Screenshot_20231116-104926_Gallery.jpg

You can see the disruption of pulse tuning when I model a 50% area reduction step just before the end of the pipe

Uploaded the same file twice and it works the second time. But I still have to have the first file in there... oh well.