Anyone Ever Rebored/overbored A 5/6Th Gen

[vfrtoy]

Thanks for explanation, Guys. When I was fitting my downpipes, I thought inner diameters are a bit small but still seemed little bigger then VTEC ones.

Out of curiosity, how big is the difference in inner diameters between stock and perf headers? Has anyone checked the measurements?

How much would true performance headers for VFR800 cost in multi buy offer?

Finally, I may be wrong, but one of the guys said earlier that RC45 has a different firing order and the ways the pipes are linked in pairs should reflect engine's firing order, right? I would imagine that you link pipes which cylinders fire (and therefore 'exhale') at different moments to reduce back-pressure on exhaust gases during the time exhaust valves are opened? Am I right?

Performance headers have proper primary diameters with equal lengths with better flow characteristics... switching from a stock cat-with headers to stock cat-less headers already improved your performance by eliminating the restriction of the cat and improved exhaust gas flow by switching to larger diameter primaries... providing you switched your rear downpipes with '98 - '99 downpipes and didn't keep your Vtec or '00 - '01 downpipes that have a smaller internal diameter (ID) than the older 98 - 99 headers.

Current available after market headers may be lighter but their tubing ID's are no better than stock cat-less headers. We are trying to get a group buy together to purchase true performance headers for our VFR800s based on the RC45 exhaust header dimensions.

[CornerCarver]

http://www.vfrdiscussion.com/forum/index.php/topic/78592-potential-re-release-of-two-brothers-racing-vfr800-headers/

For all of your performance header related questions...

[CandyRedRC46]

You are probably right, guys. My only goal with those was to get rid of the cat.

Lame question: what are the differences between standard cat-less headers and performance headers and how much can you gain by going performance?

All the best!

http://www.vfrdiscussion.com/forum/index.php?/topic/74915-I-Have-The-Measurements-On-The-Erion-Racing-Header-Vs-The-Motad

So far my personal best 1/4 mile is 10.82 seconds at 127.4 mph. I haven't raced in a while, but I have since installed over bore throttle bodies, some light porting a and individually tuned cylinder mapping. Plus with launch control, I think I'm knocking on 10.7's at 130's door...

[HighSideNZ]

The 825 Gen5/Gen6

We, anyone that has been following this thread will possibly remember I struck a problem with an over-rev where I thought I'd clipped some valves.

In the long run I found no damage and I hade the surging issue with both the 825 and stock Gen 6 motors so I'd been working with DimSport/RapidBike in Italy trying to determine where the issue lied.

Eventually, we replaced the RB Racing and My TuningBike units, with the replacements arriving from Yaman earlier this week.

I got the units fitted last night and have just returned from a ride over the same route that I've used during all the diagnosis work I've carried out.

In a nutshell, problem solved. No more surging and the carburation is really good. The bike is now nice and easy to ride on the throttle and the 825 is starting to make some really good power, by my seat dyno.

So a big thumbs up to Yaman at RB US and Daniele at Dimsport IT for sticking with me thru this whole situation.

Problem solved. There must be a fault in the RB unit I returned.

Cheers

Phil

Now on with the rest of the project.

[Switchblade]

[rangemaster]

Great news. Those of us that would love to do something like this but don't have the wherewithal to pull it off are hoping it works for you. Keep the reports coming.

[vfrcapn]

Cheers

Phil

Now on with the rest of the project.

Great news. Those of us that would love to do something like this but don't have the wherewithal to pull it off are hoping it works for you. Keep the reports coming.

[yycviffer]

Hi guys,

Its been a while since I have posted much of anything around here, so I figured it was about time to have a go. First off, respect to Phil fo the work he has done. Between the bore on the engine and the rc45 headers, I will add my kudo's to everyone elses. This has got me thinking about the whole subject of increased power, which if I am not looney, is what started this all right?

So with all due respect I have a question to ask. Going the overbore route is obviously a ton of work. I was looking back into the bioblade article and they got "125 hp at 10,000 rpm and 69 lb-ft of torque at 8250 rpm. Reprogramming the engine mapping and changing the end canister produced yet more punch, 134 hp at the back wheel." That has to be pushing 140 at the crank without changing the displacement. From the article it was flowing the ports, cam reprofile and custom exhaust.

I know phil you put in reprofiled cams and now have the rc45 exhaust going along with all the rapid bike electronics. Was boring out the cylinders really required/worth the time and expense? Or was it just a study in "Can it be done?" I have also followed the big bore throttle bodies. Were there any measureable gains from that? With different cam timing maybe, but on thier own? I guess Iam looking at the engine as a package, intake, engine and exhaust. Toro's supercharger kit yielded great gains and used the stock headers. Is the greatest gain coming from the cams?

All right, let the abuse start.........................................................

Cheers

[HighSideNZ]

Hi yycviffer

Thanks for the kudos

Yep, you are right, the big bore is a lot of work for possibly not a lot of gain.

It is interesting I've got the bike on a brake dyno on Monday so the proof will be in the eating, as they say.

I'm going to not say what I expect to find until I actually have the dyno run output, but what I'm expecting is a good boost of torque in the mid range as that is what I designed the cam timing/centrelines around.

As I outlined in the post about the pipes, the increase overall has been fantastic from the pipes alone but I did do a far bit of work to balance out the primaries/secondaries to give a different curve front to back.

The breathing is pretty good standard but the HRC porting outline and a general tidy up/matching is well worth it I believe.

I'm not convinced that you need to go bigger in throttle bodies for a road bike in general but it is definitely best to match the bodies to the isolators and the ports.

The cams are also an interesting situation. There are good gains to be had there, but make sure that whoever does the job knows what they are doing and doesn't distort the cams like what happened to me.

As I outlined earlier in this post the dyno will tell the outcome!

With a proper eddy current brake dyno, compared to a steady state like a DynoJet, I expect to get accurate data that is not inflated.

[Cogswell]

Can't wait to see the results. For me, something like this would be a labor of love no matter how it turns out. Great project!

[SEBSPEED]

I have two TBR full systems for my 4th gen,one that has cylinders 2&4/1&3 paired and the other has 2&1/4&3. There really isn't a significant difference seat of the pants wise,maybe a bit extra midrange with 2&4/1&3 together,it's really hard to tell. The main difference is the sound,with 2&1/4&3 it has that classic VFR nascar sound but with 2&4/1&3 it sound almost like an Impreza wrx to me.

That is odd that TBR made two different exhaust merging pairings for the same bike... Is one a left exit and the other a right exit exhaust?

Yeah one is left exit and one is right.

I have a TBR on my 4th gen that pairs 2/4 and 1/3. It sounds like a 360 crank engine.

[Mohawk]

yycviffer, the bioblade, had cams & a small amount of porting, plus a custom exhaust. I was in contact with the jurno that had it built. The 125hp was on petrol, the peak torque you listed is way wrong. Made 55ish torque. The 134hp figure was on methanol, hence the Bio in its name !

If you check out my Yoshi stacks thread, you can see my latest dyno, 118.5hp, but would have been 120 if my rev extend had not got lost. All done with similar mods to the bioblade on standard bores. So it is doable, with no loses. 120 was my target, so I'm happy.

As Highsidenz has done basically the same mods, plus the big bore that will give better torque & as he said the big bore should breath better as one side of the inlet valves are unmasked by the big bore. He also has 6th gen injectors which give a better fuel air mix, so expect good things come Monday. Is it worth the gains yes, but not if you had to pay two thousand pounds to get it done, plus stripping the engine from the bike etc. If you wanted a ride in ride out service it would cost 2K in the UK.

Can't wait for the results, it's like Phil, has had my baby :)

[HighSideNZ]

Hey Chris, you are making this sound incestuous! LOL

As Mohawk has outlined, any level of mods like these are time consuming and so come at a hefty cost if you can't do the work yourself.

Come on Monday!

I'm hanging out to see what the results are as well.

[Switchblade]

Hey Chris, you are making this sound incestuous! LOL

As Mohawk has outlined, any level of mods like these are time consuming and so come at a hefty cost if you can't do the work yourself.

Come on Monday!

I'm hanging out to see what the results are as well.

Now you know pretty much everyone on this forum waiting also. No pressure .

Roll On ..

[CandyRedRC46]

Mohawk, when are you doing a head port and polish??

Sent from my A0001 using Tapatalk

[Rush2112]

Hey Chris, you are making this sound incestuous! LOL

As Mohawk has outlined, any level of mods like these are time consuming and so come at a hefty cost if you can't do the work yourself.

Come on Monday!

I'm hanging out to see what the results are as well.

Is it Monday in NZ yet?!?

[Mohawk]

Mohawk, when are you doing a head port and polish??

Sent from my A0001 using Tapatalk

After you have done that Dyno run, so could be never :)

[HighSideNZ]

Hi Guys

Well the dyno run is complete but I don't have the graph as yet.

It went really well until the water pump seal blew and started pumping coolant out over the dyno room floor.

We carried on and got the run done.

As this is a Mustang/Factory Pro eddy current dyno, the figures are about 12 to 13% down on what you would see from a DynaJet inertia dyno.

But from readings I took straight off the screen, I was seeing the following:

RPM RWHP

10500 105

11000 112

11500 117

12000 122

It was still making power and had not hit the rev limiter but I was concerned with the coolant situation so we stopped.

If I factor these with +12% they come out at:

RPM RWHP

10500 117

11000 125

11500 131

12000 136

I'll wait for the official graphs but I'm happy with that.

I'd have to say that a large part of this is down to the pipes/cams. Just allowing it to breath.

It goes to prove that the throttle bodies are not a limiting factor in horsepower from these engines.

I'll keep you posted once I get the final figures emailed to me.

Back to repairing the water pump.

Cheers

Phil

[Duc2V4]

Not sure how much money all this cost you but I'm sure it's a lot less than the $184k price tag of the RC213V-S and your making more horse power to boot, well more than the U.S. version will have.

Great Job by the way!

[Mohawk]

Good result Phil, around the numbers we were expecting, which is great. Bummer about the water pump, but I did say you gave birth to my baby & I guess the placenta burst :) maybe go electric water pump, mine makes the bike run cooler & recover quicker & they released a newer slightly bigger version with an increased flow rate.

From my experience, DJ dynos normally read about 15% higher, I know you have been conservative @12% to avoid any noise, so more like 140DJhp @15% which is pretty good for that engine capacity & more than an 840 version of the 750, which topped out at about 125Hp.

Your results are better than the old dynomohum 870 produced too, so hats off to you for pulling this off. If I ever get round to getting my finger out I would love to do this or maybe the 916cc version :)

Sir we salute you.

[HighSideNZ]

Hi Chris

Thanks for that.

I've replaced the pump with my Gen 6 one.

What did you use for the electric one on yours?

Interesting on the DJ increase in the 15% order. I didn't think it was that high.

Anyway, comparing dynos is a no win situation in any case.

If you do do your build, a 916 would be really interesting to say the least!!

Cheers

Phil

[Mohawk]

Hi Phil, I used one from your island neighbours, https://daviescraig.com.au/category/electric-booster-pumpsI used the 15L minute EBP. There are 18, 23 & 25L versions now. The 15 has coped with my increased power no problem, as it runs all the time from ignition on.

Only thing I had to do was add T piece in the bottom hose between rads to allow re circulation from the T-stat so the T-stat would work.

I also fitted a lower temp fan switch, which comes on at 95c so the engine never gets to hot even in town.

[HighSideNZ]

Hey Chris

The 15l EBP has 3/4" connections and the standard lines are 1" (25mm).

What did you do re this?

I take it also that you removed the standard pump?

When you say you put a Tee in the bottom hose, there is already a Tee in that line?

Cheers

Phil

[Mohawk]

You are correct the EBP has the wrong size outlets, so I bought some 19mm Id/25mm OD (as in 3mm wall) silicone hose & cut a couple of short pieces to slip on the EBP unions, then the 25mm hoses fit straight on & hose clamp in place.

See here http://www.vfrdiscussion.com/forum/index.php/topic/72202-vfr800-10year-refresh-part-deux/ Part 21.

http://www.vfrdiscussion.com/forum/index.php/topic/73790-a-few-more-mods-its-winter-what-else-is-there-to-do/

Shows the T in the hose for the T-stat recirculation, i.e. allows the pump to circulate around the head with the T-stat closed, until heat opens the T-stat & allows the rest of the rad to come into play. Search for "Black hose" the pic above those words shows the T with hoses fitted. You'll understand when you see it.

If you look at the water pump, it has 3 hoses, 2 x 25mm, being main coolant in/out, the third is 12mm IIRC that is the T-stat-head recirculation hose, that my T piece replicates. Orginally I was going to use the Davies Craig coolant controller, had it all fitted, before discovering that it would NOT operate the EBP, needed one of the big pumps ! With that controller you remove the T-stat & it pulses the pump during warm up & then adjusts flow based on actual temps. Great idea, pity it did not work with this pump :( They authorised a full refund from the place I bought it.

Point to note is the the coolant stub top left above the genny housing, where the circular hose from the water pump goes to the head, is NOT 25mm, i discovered this by leaks when I added my silicone hoses. To cure it, add 2 layers of heat shrink & shrink in place before adding the hose. It fine if you use Honda's hose, but not with 25mm replacements !

[Switchblade]

Great numbers !!

Roll On ..