About to get a remap done (PC5) and looking for some advice...

Hi

I bought an 07 vfr 800 vtech in february, which had 2900 miles on the clock. Initially I found that there was a lot of stuttering/oscilation when low on revs and at constant speed. There were also flatspots around 4-5.5K revs. I bought and installed a PC5 with the o2 eliminators and have been very happy with the results. The flatspots are gone and the vtech surge is now minimal. However my fuel economy has taken a huge nosedive and struggle to get over 110 miles before hitting the reserve on the tank. SO i've decide to get a custom map done. I like the idea of being able to switch between an economy mode for commuting and a 'sport' mode for when I'm touring or on a leisure ride so will get them to set up 2 switchable maps. The reason for this is to save money on fuel economy on the motorway/town and i'm curious to see how much difference the tune will make to the bikes power.

Now, in an ideal world I'd put in a k&N filter and a new exhaust system so that I can make the most of the dyno tune and get a nice power increase, but I don't really have the budget for all that. I've been looking at how people have gutted the exhaust and or cat, fitted end cans etc but most of them have not gone for a dyno tune afterwards. So i'm not sure how all these options would compare in terms of increased power.

So i'm wondering if I should try to do something to the exhaust, put in a kn filter, or just leave it all as it is? at the back of my mind is a worry about how restrictive the stock exhaust and cat might be? Would new downpipes (ones without a cat) be better than replacing the end cans for example? or just gutting the exhaust?

many thanks

 

What stock map did you use? Is it for a similar year and stock setup? Are you whacking the throttle everywhere you go? If yes, the mileage may be reasonable. If no, I wonder if another problem to the bike was introduced recently?

Regarding the common upgrades.

1) The header and downpipes: High flow versions increase peak horsepower but lower power lower in the band, where you ride on a daily basis.

2) Weight loss from any part of the custom exhaust is good overall as the engine is moving less weight, but this is a tradeoff to #1.

3) Mufflers make small or no changes to power, depending on the muffler. Once again, the weight savings can be good overall.

4) The bike is incredibly lean due to the EPA rules. Adding more fuel will take the bike 90% of the way there. This is the one thing you have noticed, or will notice with a custom map. A dramatic raising of the front in the acceleration range.

5) A lot of discussion on air filters here. It seems to me that the bike is not limited significantly by the filter, but more by the overall design. I started with BMC filters but am going back to stock.

6) Catalytic converter: A clogged one, from a terribly running bike will rob power. There should not even be enough miles on the bike to have affected yours adversely. A fully functioning late model catalytic converter, if it robs any power, it would be very little. Help the environment, do not gut this just because other people do. But I must also mention, this is another place for weight savings.

If I had one vote out of many, I would say tune it, and you are done. That provides a dramatic improvement at a reasonable cost.


I await the vociferous, vehement, vitriolic disagreements that are sure to follow this advice, but given the age and that it is partially broken in, I suggest that you or the tuner balance the starter valves. Hesitation down low can be due to an imbalance here, and this is a common maintenance item. Any imbalance also makes you feel "there is no power" which is what you are trying to address here.

 

Hi.

Thanks for getting back to me. I am using the map from PC official website that is designed for a stock VFR. I checked the map and it is not just full of zeroes, as the original map would be relative to the current one (hope that makes sense). I'm driving quite conservatively on my commute and that seems to be where I'm not getting good mileage. It's a mixture of fast dual carriageway and some town riding. On the same route with my CBR 600f (2000, carb version) I was getting around 9 miles per litre which i thought wasn't bad. The bike had been sat in a warm garage for a couple of years before I bought it, but I had it serviced by a mechanic I trust, so I think there was nothing really wrong with it before I fitted the power commander. I had ridden it for a couple of weeks and the fuel economy was definiteyl better, but I was more concerned about flat spots, oscillation etc that i didn't pay too much attention to the mileage at that point.

1) thats interesting. I would prefer more power in the usable band so this makes me lean less toward changing pipes etc
3) One of the things i've noticed about a lot of aftermarket road legal exhausts is that many claim no need to remap after fitting....so this makes me think what are they actually doing to claim HP increases?
5) on the PC website it says that you can use the same map with either a kn filter or stock.....so not sure whether it will make any difference once tuned.

As for the starter valves, I'm not sure if they're ok or not as I've not much experience with them. I've balanced carbs on the cbr before and have an idea from listening if it sounds like they need doing. I think i'll prob get the tuner to do this as well, as he has to muck about with the pair and flapper valves anyway, so will have the tank up.

thanks for your comments and welcome any more.

 

ANother quick question: I've heard that the pair valve and flapper valve have to be disabled before doing a dyno run, but do they need to be permanantly disabled thereafter? I mean can you disconnect them for the run then reconnect? or should they be always blocked off/blanked after the tuning?

thanks again

 

Yes we call those "a zero map", where they make no change to the fueling.

Being conservative and getting 110 miles/tank - I agree that this sounds very low. Maybe the map is rich and a tuning will help but, being the correct map, be on the lookout for other issues.

How much fuel have you gone through? Is the fuel all fresh now?

These bikes are rated at low octane. I don't know your country's octane system so check the owner's manual and compare. The bike will not benefit from high octane, and high octane will not burn thoroughly, thus it can in fact reduce mileage.


3) muffler power

Read this:

http://www.micronexhaust.com/faq.php/71

Is that non-specific or what? And that is the manufacturer's FAQ. So they kinda-sorta-somewhat hint that a more efficient design just maybe-might-whoknows add some-alittle-whoknows horsepower.

I have seen some dyno charts with one or two horsepower increase from slip-ons. But even Micron tells us that these are mostly for sound, looks, and weight reduction.

Now weight reduction is a valid way to speed up the bike. But every pound of savings is very expensive, as you know.

 

Let's think this through: The O2 sensors are disabled. The PAIR injects additional air into the exhaust to burn excess gas when the engine is cold and running rich. The O2 sensors are not being used and would not make any feedback to fueling based on PAIR ON/PAIR OFF. So I would say the PAIR valve can be re-enabled after tuning. I am going to tune my bike soon (with he Wideband 2 unit) and plan on enabling the PAIR when done. I like clean air.

The flapper exists to reduce intake noise per the EPA. Now Jeff here on the forum is pretty smart and recently pointed me to an example of a small power gain from disabling the flapper. I would say if you like the louder sound of the intake, leave the flapper off. If the engine is already loud enough for you, leave the flapper on.

 

Hi

I've done around 1500 miles since I got the bike a few months ago so the fuel has been flushed through many times. The UK standard unleaded is what I have been using but I believe it is "better" than some other countries....so it may be slightly higher octane but isn't performance fuel

3) I'll check that out in a minute.


As for the pair valve, what you're saying makes sense. My limited understanding is this........ the dyno tuner wants to know what the mixture was like in the combustion chamber....to find that out he analyses the exhaust gas. if there is extra air being pumped into the exhaust then it's difficult to determine what just happened in the chamber. but once that mixture is set, it doesn't affect power if the in exhaust mixture then has more air in right? so you can re attach the Pair.

As you say for the flapper, its more of a preference rather than a requirement.


thanks again

 

Yes I agree.

Other factors affecting mileage:

Did you change the sprocket sizes? The reason I ask is if you got very aggressive, say with -1 tooth in front and +3 in the rear, that would increase RPM a lot, and mileage would get worse all around.

If the thermostat is not working and the engine is too cool, it will perpetually run rich.

I took the liberty of checking out the UK weather, and I see it is cool there. Thus this may apply to you. If you ride for 1/2 hour and it never goes about 160°F (71°C) that is a hint the thermostat is stuck open.

A definitive test: Start the bike cold. Put your hand on a radiator or use a laser thermometer. If the radiator slowly warms up along with the engine, the coolant is flowing when it should not be and the thermostat is stuck open. It should stay cold until the temp shows 180°F/82°F then get unbearably hot all at once when the thermostat opens. That is the correct operation.

Another factor affecting mileage is brake condition. If the brakes are binding that is a problem. You can spin the front wheel and should get about two spins. The rear wheel is tougher to test as it has the chain on it. If the last owner let the fluid get old, although you may have changed the fluid, there can be hard fluid in the seals inside the caliper, causing the pistons to stick. So binding brakes may indicate the need to clean/replace seals and pistons in the calipers.

 

hi

Thanks again. The bike is totally stock mechanically, so no sprocket changes. I had it serviced and the coolant was changed at that time. The temperatures seem ok to be honest. not too hot, not too cool. It warms up ok and is usually between 85-100C getting up to 100 when sitting in traffic and then back down a little as I get going again. the fan is kicking in and being effective when it gets too hot.

 

Thats a good shout on the brakes as when we went to view the bike the brakes were binding a little bit. not enough to stop moving the bike but enough to warrant a service. I normally do a lot of my own servicing, but since the bike was new to me I had the brakes serviced when I got the bike. The wheels spin freely, as i've had it on the centre stand for cleaning and have checked both.


the last owner was a friend of mine and although she hardly ever rode the bike, she had it serviced and MOT'd (road worthiness test in UK) every year lol.


thanks

 

Oh you got a good deal. My bike had no maintenance from the prior owner. THAT is how I know about some of these calamities HAHAHA.

 

Like a visit to a physician, a second opinion on all this stuff might be in order. There are guys on this forum who have actual hands on experience with what you may or may not need.

Binding brakes are indicative of brakes locking up. This is a condition that can be fatal. If the binding is enough to cause the forks to compress. STOP and get the hell off the bike bleed off some fluid at the slave, The bike can then be ridden sans the front brake. Do not touch the front brake lever. This can cause the brakes to lock up again.