The truth about full system race exhausts - Knox Suzuki GSXR 750 series episode 4

The truth about full system race exhausts - Knox Suzuki GSXR 750 series episode 4
In the first episode of our Suzuki GSXR 750 road and track project series, after removing the full system race exhaust system, we scoured the internet and found an ebay bargain standard Suzuki GSXR 750 exhaust system in a bid to gain more power and pass track day noise testing… did our strategy pay off?
It’s been a mission, but yes, it did! After re-fitting the standard full exhaust with catalytic converter to the GSXR 750, we took it back to Jordan Bikes for some remap adjustment and the results were fantastic displaying a 24hp gain against the full system that had to be baffled to pass the track day noise limit.
In the UK, track days have noise limits designed to keep the public happy and not complaining too much. Unfortunately, full race exhaust systems really struggle to control noise meaning that most riders with full exhaust systems have to fit baffles in order to ride on track. In our case, this destroyed the power of the GSXR 750 and is the issue that we have finally fixed - for good!
While we have gained 5kg in weight against the racing exhaust, we have gained 24hp and the bike now finally runs like it should - fast, eager, torquey - ready for a shakedown!
This project series has felt like a steep learning curve and unfortunately, there isn’t always the information out there and hopefully this will help you if you are considering something similar.
But during this specific process, we feel like we have learned the following:
1- Only fit a race exhaust system if you are racing or live in a country where there are no noise restrictions. For the UK track day rider, there is no point… You will mess up your fuelling and will need to remap, the gains will be pretty marginal and then if you do take it on track, you will need to baffle the exhaust meaning you will lose most of/if not more of the power you gained.
2- Standard exhaust systems are actually really good. Designed by the people who made the engine and the motorcycle, these exhausts are about maximising performance whilst simultaneously conforming to noise and emissions standards. While a race exhaust will be lighter and could deliver a few more HP, it will blow out on the noise…
3- Remapping your motorcycle is very effective and this is where the majority of your gains will come from, even with a standard exhaust system. While it is worth checking with the manufacturer of your bike to see if there is any warranty things you need to be aware of, remapping will get your bike running better throughout the rev range, smoother and more powerful. Check out Jordan Bikes here, www.jordanbikes.com/.
Hope you enjoyed this one. Please like, comment and subscribe and we’ll see you next time!
Thanks,
Aaron KNOX
www.planet-knox.com/
Gear worn on test:
Knox Urbane Pro MK2 - www.planet-knox.com/category/... Knox Richmond MK2 Jeans - www.planet-knox.com/product/r...
Knox Covert Gloves on road - www.planet-knox.com/product/c... Knox Handroid Gloves on track - www.planet-knox.com/product/h... Knox Quilted Jacket - www.planet-knox.com/product/t...

[@UniversalBikers16]

Well I’m very surprised about the results! Another great vid guys.

[@KnoxArmour]

Thanks man! We were fingers crossed for the result, and super relieved when it came off! Aaron KNOX

[@salahstylist]

@@KnoxArmour I am happy for you men, I have the same bike and I would like to buy your full exhaust GPR, let me know and greetings from The Netherlands!!!

[@drasticthompson1995]

I love my K8 7 Fiddy! I feel like it came off the assembly line with just a little more than the rest of the bikes from 08, because it is faster then every 7Fiddy I rode with and it is still stop mapping with just a M4 Slip on with cat! This summer it will go to Moore Mafia for its prep!

[@bosoone1386]

The intake noise on the 750 is better than a noisy exhaust IMHO. That intake growl is unique to the GSXR and so addictive!

[@KnoxArmour]

Totally agree and really glad to back to stock! Thanks Aaron KNOX

[@shaneobrien7978]

Great video with loads of practical advice. And, saved me spending money on a full system. Many thanks 🙏

[@KnoxArmour]

Thanks Shane, glad it was helpful! I was at Donington last week and the Marshall actually came over to me and said to me "thanks so much for running a stock exhaust". They were having loads of problems with loud bikes and people were getting black flagged left right and centre! :) Aaron KNOX

[@AndyManCam]

I love it! It flies in the face of all the armchair tuners and shows that oddly enough, the millions spent by manufacturers in development weren’t entirely wasted! Really happy the bike is performing as it should!

[@KnoxArmour]

Thanks Andy! It is running awesome now, proper weapon! Yeah, the manufacturers are not daft 🙄😅. Aaron Knox

[@AndyManCam]

@@KnoxArmour And don't forget you can still claw back a few of those Kg's with a set of carbon wheels! That cable tie holding the brake reservoir on looks like it could be 2 or 3 mm shorter too 😜

[@KnoxArmour]

@@AndyManCam haha... yes the cable ties... 😂🤷‍♂️. Next job... sort that out! Lol

[@AndyManCam]

@@KnoxArmour Priorities! We‘ve all got our own ‚cable ties‘. Mine is the rain cover that fully melted on to all four of my downpipes in September. Gonna need a chisel to get it off, so it can wait till I’m ‚ready‘!!

[@N0kJAA]

Exactly: "....the millions spent by manufacturers in development..." Plus speaking on my own behalf, I'm starting to switch towards either a stock exhaust or something quieter than my present akropovic GP. Even with a DB killer installed it's still a tad bit loud... And I love the sound...But require less attention 😊. Btw, good video Fella 👍🏾😎

[@leeandrew2682]

OMG had a K8 R600 in my younger days... had the stock pipes off as soon as i received my full system. noy having it tuned properly, i could def feel it turn down a notch but i believed the top end had gained... i was wrong AF. excellet clip might i add, memories of my K8 got me subscribed to this channel.

[@KnoxArmour]

Thanks! Well, its impossible to tell exactly what happened with the un-baffled full system as we didnt dyno it in that state, but definately now the bike is much stronger in torque and has a really good top end. Just been on track too and it was very good, although admittedly now a bit too quiet ;)... but at least it passes all noise testing and has good performance! Thanks, Aaron KNOX

[@itstherealjammin]

this is a superb video, it's convinced me to go back to stock !

[@Freedombelongstotherighteous]

I have the same exact bike and I always find myself checking out your videos thinking ahhh my bike could look like that one day lol good work man

[@KnoxArmour]

Haha, thanks! It is now properly awesome and look forward to sharing the finished article! Aaron KNOX

[@GodLike_1]

Hello Knox, I recently start looking at your channel cause I have the exact bike you have (gsxr 750) I did a mod on my stock exhaust which I think you will be interested in cause it was a day and night difference,the stock exhaust even with a cat delete is still restrictive, so after looking at a few threads I decided to give one a try,it's very simple ,on the intake side you drill a hole about inch and half wide, you would require a 12 inch long drill bit, when you look into the intake side you would see a curve that's area you drill into when you done you would be able to see the hole from the rear of the exhaust,if you understand the stock exhaust the air has to make an S before it comes out and that is where the restrictions is, your dB would go up bit not by much and you will have a heavier grumble on idle, when I ride I like to listen music sometimes and with this mod I can still hear it clearly plus the rpm swings much faster and there is still a decent amount of back pressure. Well keep up the good work hope you give it a try 👍

[@richardb285]

Very interesting video and I personally was not massively surprised at your results. I had to ditch my standard exhaust when fitting race fairings as the cat was touching the belly pan in several places and I didn't want the risk of a fire having previously had a near miss on another track bike! My Gixer is a dedicated track bike now. With a long end can (400mm) it should be quiet enough for most UK trackdays without baffle. I too had it mapped. The fueling was MILES out between 4-5000 rpm. With baffle fitted I only lost 3 bhp which was super pleasing. Its nicely into the 130's without baffle. Cant wait for the season to start

[@KnoxArmour]

Thanks. Yes totally and if I was running track fairings would have to run a full race exhaust. In hindsight to this video and as a result of talking to many more track goers/racers, as you say, I could have probably sourced a long exhaust to do the job. However, in future bikes I own (track riding, not racing), I'd still swerve changing the exhaust for all the reasons stated in the video as, in most cases, they are very well developed, produce good power and there is never any question regarding noise regulation. Personally, I would sooner spend the money on the upgrades that make most difference on track like race suspension, tyres and brakes and more track time. Thanks, Aaron KNOX

[@yreyesq]

Great content, wise words, very good advices! Thank you very much for your work. I'm so glad I haven't change anything on my motorcycle yet, cause I understand that how they come out of the factory is how the engineers thought would be the best. I'm the proud owner of a GSX-S 1000 which is completely stock and I couldn't wish for a better bike. Thanks a lot again for your video, I've really enjoyed it...

[@alexventrov6826]

Yes, that's how the engineers set it up for emission standards. Without a tune bikes from factory run very lean. If you're happy then good for you.

[@KnoxArmour]

Thanks and glad you found it helpful! Glad you enjoy your bike! If you ever wanted more performance out of it, a remap would probably help to make the fuel mapping perfect. Thanks, Aaron KNOX

[@drasticthompson1995]

Thanks for the vid it was great!

[@jimbo1485]

Loving the videos and the bike Aaron. Great stuff 👍

[@KnoxArmour]

Awesome, thank you! Aaron KNOX

[@n0surrenda]

Very interesting result for this bike. With other bikes, such as the S1000RR, a full system such as the Akropovic results in mid range gains once the ECU has adapted. With my L6 GSXR 1000, after I elimiinated the o2, removed the CAT (because it had come loose), and reflashed the ECU, I got mid range gains (according to my arse dyno) and a much more responsive throttle overall, however fuel consumption greatly increased. Well done on this video, very, very informative.

[@MatiMorini]

Hi what rwhp did you get???

[@KnoxArmour]

Thanks Chris, glad you found it informative. Didnt mention, but a part of what Jordan Bikes did as part of the remap was to remove the o2 sensor and we removed the SET valve too. Of course, a Akrapovic full system exhaust definitely should gain more power with a remap than a standard exhaust which is why race teams use them. The problem we have here in the UK is that we have strict noise testing on track days and now our annual MOT checks are getting stricter too in regards to noise. My full system exhaust was too noisy for track days meaning a baffle was required, which in turn killed the power output. The stock exhaust with cat in place now allows me to pass all track day noise testing and get great power and I'm happy with it. All the best, Aaron KNOX

[@1MrBryn]

Everything is so well set up out of the factory now, that it's best to leave the damn exhaust well alone. A nice end can for a bit of bling is good, but leave it at that.

[@sambyf2445]

Top video. I have the exact same model with only a Yoshi end can. Great bike and appropriate power for the road. I previously owned two quick cars - an Audi S3 and a Merc C63. Presence wise the Merc had it all day, but fun wise the S3 had the Merc beat all day. It’s hard to understand this until you experience both on the road. I could use the S3 to its max every day but for the Merc it just had too much power. And that is why I will keep the 750 and not fall into the 1000cc trap. Maybe I am wrong, maybe the litre bike is actually useable - I’ve never ridden one, but my gut tells me the 750 is pound for pound the superior road weapon. Any advice is welcome 🙏

[@KnoxArmour]

Thanks glad you enjoyed it! We have just got a GSXR1000r too which will start featuring on the channel. Of course the 1000 is faster and has more grunt, but its not like its night and day different, they are both more than fast enough for road and track! Thanks, Aaron KNOX

[@connor1982]

Yeah you're definitely right. 1k bikes are definitely the best but on the street and track the 750 still is truly the best all around motorcycle. Put the 1k boys to shame at the track all day long

[@mindspinn311]

More riders need to see this video and understand how exhaust systems and tuning actually work. So many sport bike owners do a slip-on or even worse and fully system with no tune. They don’t realize they’re losing power everywhere and their engine is running dangerously lean. Modern factory exhaust systems are very good, it’s just the emissions compliant tune that ruins the fun.

[@KnoxArmour]

Thanks Alex. Yes, the exhaust/power/noise control performance is a complex subject. I agree, a lot of people just whack a full system on it and assume that it will be great, but in most situations, its not that easy and there are issues if people don't remap and even more if strict noise tests must be achieved. Thanks, Aaron KNOX

[@Daf0ck1]

i have Yoshi r11 slip with decat and remap ECU. Got on wheel 140hp. The response from throttle is sick at low rps it goes like crazy. Compared to my 600rr 08 without tune i felt like it lack something till 10k rpm's. Now i know what w/o tune cause being donkey with Factory restrictions.

[@ahahahahahaahahaa]

So, I’m confused. You show your dyno results that say you had improvements from reinstalling your stock exhaust, however, you later state that you will gain horsepower if you were to install an akrapovic full exhaust system and get it retuned. Was your original full exhaust system not tuned correctly, or was it just a shit exhaust. Ive personally never heard of that brand you had originally installed. I understand your limitations with European track noise limits, but here in the US we don’t have those limitations. Generally, from what i understand, a full exhaust system and a remap or a power commander V will on average increase horsepower by about 15 HP (a little less with the provided baffle installed). And also save 12 pounds or 3% weight. So my question is, how are you getting the results from the dyno that you showed in the video with the performance increase when switching to the stock system?

[@KnoxArmour]

Dont be confused... we couldnt run a full system exhaust on track as it was too loud, so we had to baffle it. This meant the power war running at 107hp becuase of the baffle. By changing to the original exhaust, Ive got full power of 131hp and fixed the noise issue. If I was to change to a full akrapovic, I may gain another 2-3hp max, and would save 5kg, but would probably be in the same position in terms of not passing noise regulations. On new motorcycles, a remap will achieve most of the power gains, and another exhaust helps a bit, but most of the power comes from the fuelling remap. Hope that helps, Aaron KNOX

[@antoniosfoskolos102]

@@KnoxArmour the max power I’ve seen on a gsxr 750 is 134 whp full bot on bike with the ecu remapped

[@-DC-]

Have always returned any used bike back to OEM parts have made thousands over the years in systems and steering dampers etc.

[@KnoxArmour]

Cool! Yes and adding those parts to bikes normally makes absolutely no value to the bike when you sell it. However, from experience now, I would put an extra value on proper aftermarket suspension as it is really good! Aaron KNOX

[@alastairb8597]

I don't want a noisy bike but, as mine is only used on track and the original fairings are looking very tired after a few excursions, want to fit race fairings.... don't really want to have to cut a big hole in the belly pan to accommodate the cat...options other than decat are limited?

[@KnoxArmour]

Well... with some more experience under my belt... You can run a race system, but compliment it with an MHP 450mm length clubman can with a 50mm core and it will be able to pass noise regs with no baffle and no power restriction. We've just done it with our new GSXR1000r susperstock bike and it works. Hope that helps. Aaron KNOX

[@lordgibbness]

Just thinking about this. Would you get better results power-wise, and still acceptable sound level, if you removed the cat from your stock system? Or is it all welded in?

[@KnoxArmour]

Thanks Rob. Tbh, i dont think there would be much in it now in terms of performance, probably the main difference is weight. But it does appear that the cat is the main method of noise control on the system. Thanks, Aaron KNOX

[@marcinpudlik8172]

What about fuel consumption after remap? Did that change if yes how? Thanks for great info. Like you I used to ride with load exhaust now I stick to standard and I'm happy.

[@KnoxArmour]

V similar fuel economy. Still get about 120 miles to a tank, and about 70 on track. Thanks, Aaron KNOX

[@marcinpudlik8172]

@@KnoxArmour that's great thanks , I'm considering to do remap to my honda xadv is only 55 bhp I'm not planing racing just to have little bit more for overtaking. I used to have power full bikes but I'm more in to touring! What's a costs of remap? Is make sense to do to such a low power bike? What you recon?

[@KnoxArmour]

@@marcinpudlik8172 Its up to you really. I doubt that a remap on the Xadv would make a massive difference as its quite a heavy bike 230kg ish with 55hp. By contrast, this GSXR is 185kg with 130hp. While the power increase was definitely noticeable, but the main thing was throttle response. If the throttle response is snatchy then maybe its worth it... Hope that makes some sense? On a modern bike, I would remap again, but mainly to improve throttle response. thanks, Aaron KNOX

[@Bow-to-the-absurd]

Stock exhausts all day long. Properly set up and perfect for the job.

[@KnoxArmour]

Sure, its running much better now.. cant wait to get it on track next month! Aaron KNOX

[@fictiveaudio]

Surprising result but if it works better with the stock exhaust and tune, then so be it! Have fun with it :-)

[@KnoxArmour]

Thanks, will do! Aaron KNOX

[@alexventrov6826]

It is surprising for sure, but hey its for the track which has restrictions. If he did it just for street I'm sure he would have some people giving their opinions 😁

[@KnoxArmour]

@@alexventrov6826 sure. I think its a great solution for what I'm doing... track days with noise restrictions, and is a much better solution than a race exhaust system with a baffle in it. Also on the road, it is now getting mich stricter for MOT checks reference noise too, so happy with the result. Of course, if we were going racing, we may have a different solution. Thanks Aaron Knox

[@sambyf2445]

It’s just so hard to get my head around this. I have driven countless vehicles before and after cat removal and the performance has always improved due to the unrestricted flow. I just thought the same principle would apply to bikes. This video has definitely got me thinking now about the mods I want to make.

[@MatiMorini]

i ' m on this stage but i tune myself my bike i will make video on my channel inc dyno runs matimorini

[@lordgibbness]

Most likely the aftermarket exhaust wasn't performance tested by the manufacturer. Something like an akra, sc project or similar should give you more performance even with their respective baffles in.

[@lordgibbness]

Great video though. Informative!

[@connor1982]

That is true but my 2019 750 with stock exhaust tuned made only 2 HP less than the $1200 akropovic full system. I totally wasted my money for the power but it's literally just weight savings. Sadly since it's a street bike though it's way too long and I can't even break the law without the entire world hearing me rip ass

[@rudy3835]

Remove baffle put full race exhaust with k&n filter and remap it it be better than one with cat and stock can

[@KnoxArmour]

No doubt.

[@FOX1RR]

So sorry. My 2022 GSXR 750 with arrow full race exhaust and a tune just made 136.41 hp at the rear wheel. And its much lighter due to the removal of the catalytic converter and SS headers. Not buying your decision is best for most applications.

[@KnoxArmour]

Sure, a race system will ultimately give more power and be lighter... but in UK, its hard to use them due to strict noise testing, meaning you have to fit baffles in most cases which destroys any power gains. Hope that makes sense. Thanks, Aaron KNOX

[@cordellian]

The mind boggles as to how a Cat can give you less restriction than a DB killer, everything i have ever been told or heard about bikes is clearly wrong.

[@KnoxArmour]

100% and why it was so surprising to find out the hard way! Aaron KNOX

[@markusreynolds7586]

Not a Akrapovic Arrow or Yash but a knockoff this video doesn't make sense

[@kennedyracing7527]

Are you getting paid by the government to do this because no race team puts back weight on a bike. Akropovic exhaust and tune plus less weight is the way to go. Lost all respect for this channel

[@KnoxArmour]

Maybe you didn't quite listen, but we're not racing... this is about making a track day/road bike and with most track days requiring 102db limit meaning a full system exhaust needs baffling... which in turn and in our case significantly reduces power. As we said, they are good for racing where you are allowed more noise... but in our direct experience they aren't right for track day riders. In terms of losing respect, that's your choice, but I've been up and down the country, sorted it out and got a great result without help from anyone so don't know why that means a loss of respect... 🤷‍♂️ Thanks Aaron Knox

[@Bow-to-the-absurd]

The days of race exhausts on the road are over.

[@jimbo1485]

@The Lone Ninja 82 well said

[@heriport6654]

Ight m8 bike sounds good with stock to each their own is not a moto gp cmon. Check out the new susuki gp moto with the cross plane engine and akrapovic exhaust sounds fantastic

[@redline350zHR]

@@heriport6654 where can i find that? I havent tried searching here on YT

[@flamintasty]

The titanium Akrapovic system on my 2018 GSXR 1000R only loses 3hp when the baffle is fitted into the can. You didn’t get the same result with that cheap exhaust, because that’s exactly what it is. An exhaust developed and sold by a company like Akrapovic or Arrow, gives better results. But then my exhaust retails at £2400, that GPR thing is considerably less. You get what you pay for!! Check out Sylvain Guintoli’s video of his GSXR being dynoed with and without the baffle, the results back up exactly what I said about the exhaust. Sylvain has the same bike and the same exhaust as me.

[@KnoxArmour]

Agree to an extent, but the new akrapovic systems developed with special baffles are not available for every bike. For example, you cant get them for the GSXR750 anymore etc. From memory, Sylvains exhaust system is right on the border line of passing and even with the baffle included he wouldnt be able to ride at certain tracks. For this bike, refitting the stock exhaust and remapping has been a brilliant decision. Thanks, Aaron KNOX

[@juanpalomoyomelocomo]

Super interesting video. Good job

[@KnoxArmour]

Thanks for letting us know! Aaron Knox