Air/fuel tuning

[jeantarrou]

My Hyper isn't running the way I think it should be. After spending a lot of time last year tweaking it, doing standard maintenance, modifying it, bringing it to Adrenaline, and in the end being very happy with how the bike was performing it just hasn't seemed the same since day one this year.

At the beginning of this season I noticed right away that it was idling quite high, ~1600 rpm's. I let it be thinking maybe it was a consequence of the cool temps in March/April (even though I rode into November last year). It didn't go away so I turned in each air bleed screw on the throttle bodies a half turn which brought the idle to 1300, exactly where I wanted it. All the while the bike has been backfiring on decel way more often than last season. Last year it barely did it at all, this year it does it frequently. First I resealed the silencer/midpipe with high temp RVT so there aren't any air leaks, no improvement. Then I tweaked the fuel with my PCV, adding 25 points of fuel at zero throttle from 1500-2500 rpms, this helped quite a bit, but still some popping. I'm now bothered by a much more noticeable unburnt fuel smell since adding the fuel with the PC which I guess shouldn't be surprising.

So basically my questions are, what would cause the bike to not run as well as it did last year, why did I have to turn the air bleed screws in, and I'm not comfortable with all the fuel I've added?

My order of troubleshooting now will be, check the valves, check the belts, synch the throttle bodies (all which was done last year around 4,000 miles ago) then reload the map that worked so well last season.

Any other suggestions?

[butcher bergs]

Intake leak

[aldend123]

This all sounds like a vacuum leak. Extra air entering the system that is not accounted for. Hence the increased idle, the popping, and the need to up the fuel with your tuner.

Edit: I got beat to it.

[jeantarrou]

Message received, I'll check header bolts for tightness. Any other common areas? Any tricks for finding leaks? I think I've read that spraying wd40 around may help?

[aldend123]

Starter fluid instead. That way you're not leaving a WD40 residue every where. Listen for the rise in RPM while spraying. For an example, pull a hose and spray near the hole. But I've always preferred visual inspection. Look for lose hoses, prod them for signs of cracking or aging, pry at boots and look for cracking. Check clamped connections etc. Anything significant enough to cause the problems you're seeing probably isn't a microscopic leak.

[jeantarrou]

Thanks for the replies, started wrenching and there were quite a few hose clamps around the TB's, air filters and on various blow-off hoses that I was able to give a full turn or two. About a quarter turn on a couple header bolts also. I've decided to check the valve clearances also so it'll be a couple days before I wrap that up and take her for a spin, I'll report the results then.

[butcher bergs]

What do the headers have to do with this?

[THE STUFF 187]

Check all vaccum lines off the throttle bodies, make sure the air filter is seated correctly in the air box, spray intake boots with flammable spray, let bike get hot & tighten header bolts. you can also tape up half of the air box intake inlet to see if makes things better or worse. Also adding fuel at 0% throttle is needed on some bikes to stop popping. But its best to take 20 points of fuel out first to see if it gets better this way before you try adding 20 points of fuel this way you don't get that raw fuel smell. Some bikes like fuel out others like fuel added but I always try taking it out first. Also you should be adding or taking these points of fuel from 2000rpm to redline. If you try all these things & still have no luck I can look at bike for you if you like. FYI id would be very surprised if syncing the TB helped with your issues at all. I'd try taking that fuel out first. Best of luck hope its an easy one for you

[jeantarrou]

What do the headers have to do with this?

From what I've read, and videos posted by Dynojet that I've watched, a lean running engine combined with air leaks somewhere along the exhaust system (headers, midpipe connections, etc...) is the most common cause of popping on decel. From what I'm NOW learning I don't think this would cause the high idle though, so it remains to be seen if I have one or multiple issues at play here.

Justin, thanks for the recommendations, I'll continue to fiddle around.

[Pigman]

Most common but not alwys true........ Add a pipe with no Pair or air box block offs and you get the same affect

[jeantarrou]

Most common but not alwys true........ Add a pipe with no Pair or air box block offs and you get the same affect

Wouldn't adding a pipe without blocking off the PAIR cause a really lean condition?

[butcher bergs]

Wouldn't adding a pipe without blocking off the PAIR cause a really lean condition?

No. The lean condition would otherwise already exist as the tuning state would be poor already. The air injection occurring in the exhaust region would only serve to expose the issue more readily.

[Pigman]

Wouldn't adding a pipe without blocking off the PAIR cause a really lean condition?

Depending on the motor.......yes Really lean as in blow up lean No, just poping on the decell from the air being pumped back into the airbox

But say a GSXR 600 stock with a Pipe won't hurt or affect it Ever....

[butcher bergs]

Air is pumped into the exhaust, not the airbox

[Pigman]

Air is pumped into the exhaust, not the airbox

Yea same diff.......what he said

[jeantarrou]

The air injection occurring in the exhaust region would only serve to expose the issue more readily.

Ah yes, that makes sense.

[timmyho414]

A pop back is the burning of the air/fuel mixture in the intake track or cylinder before intake valve closes. Most of the time its because the air/fuel mixture is too lean. vacuum leak, big exhaust and no jet kit or tune etc.

So its not "pumped" into the air box so much as exploding into the air box.

[jeantarrou]

So I completed some maintenance and troubleshooting, as mentioned previously I did have to tighten a fair amount of hose clamps, but nothing was really grossly out of whack. Only one valve was out of spec, just ever so slightly tight. I got that valved back into spec, reloaded last season's map, reset the air bleed screws to where they were last year and took the bike for a spin. Idle speed was pretty much right where it needed to be, 1300 rpms, but a couple of times when coming to a stop it would stay up around 1600. A little blip of the throttle and the idle came right back down, that makes me think there's more of a mechanical issue with the idle, ie. sticky throttle cables, maybe the throttle body butterflies aren't always closing fully?

There was also more popping on deceleration and the throttle seemed a bit more abrupt than normal. Just for the fvck of it I opened up the map this morning and took 30 points of fuel out of the entire rpm range at 0 throttle, I've always felt the exhaust smelt especially rich, so why not try it. I also looked at the 2% throttle range and all the lower rpm cells were "minus" pretty big numbers, so, I added 30 points of fuel to a bunch of cells...

I know I'm going at this totally blind without having a gas analyzer in the tailpipe, but I'll be damned if the bike didn't run SUPER smooth on the way into work with ZERO popping.

If it's running great should I be satisfied, or is fiddling with it like this a recipe for disaster? Also, the "sticky" idle, mechanical? thoughts?

[butcher bergs]

Is there a reason you cannot trim the map back to factory settings and go from there?

My opinion on the tuning is to at least put it on a dyno to confirm your AFR. What you are feeling from the seat might be amazing but that does not directly reflect the quality of your tuning state.

[jeantarrou]

Is there a reason you cannot trim the map back to factory settings and go from there?

I certainly could. History is, I bought the bike with a full Termignoni and matching race ECU, ran ok but not a smooth as I'd like. I added a pod filter/velocity stack kit and bought a PCV with a dual channel autotune. Had lots of fun tinkering with AFR's values and created a map I liked. Visited Justin at Adrenaline to reset my TPS, put it on the dyno for a pull or two to see the power numbers, he put a gas analyzer on and that checked out ok. Justin did think he could get better numbers with a custom tune, something I may pull the trigger on in the future, but I'd really like to save the $ for trackdays... So, I feel pretty strongly that the race ECU map wouldn't be any better than what I've got now, would you agree?

[butcher bergs]

A custom map is tuned for your specific application. Not all engines/electronics/ etc are exactly the same.

What's a tune go for nowadays? $200 or so? If I were spending your money I'd be on the dyno once and be done with it rather than worring about the risk of engine damage.