Discussion ZXR250C Dyno Results

That is only a small change, but may give you an extra HP.

 

It depends on what you're after. As @Murdo said, your suggested main jet change is almost insignificant. If you go to 110;112;112;110 then you'll see a few more ponies. If you're keen to chase HP, then get a bung welded into your exhaust so the Dyno person can monitor AFR accurately. Secondly, some of what is happening at higher revs is because of how the TCI has been 'programmed'. They tend to be designed so you can ride around without flat spots or hesitation and/or burning valves while going WOT everywhere. You could order an aftermarket TCI from Ignitech (Czech Republic) and that will let you play with the ignition advance across the rev range, but most importantly at higher revs. Again, it all depends on what you're after. The other 'thing' to consider is that on a Dyno there is little to no air flow into the air box and at higher revs the engine will be running out of oxygen, especially if the Dyno guy is doing several 'pulls'. I run a bastardized air box that retains the inlet trumpets (built into the airbox) and also the top of the airbox for any shockwave scavenging (not that I believe in that on 4-strokes).

 

Nice curves in the dyno charts - that torque curve is very nice. The hp loss up top does not appear to be too bad, despite the rich afr's you are getting above 12k. You might squeeze another couple of hp out by going a bit leaner on the mains, but remember at WOT you really want the afr's to be between 12 and 13 for engine longevity the richness could also be as a result of the stock airbox, they are quite restrictive. Were you using an oem air filter or an aftermarket filter for these runs?

I am a big fan of tuning on a dyno, your dyno operator should have been able to give you some good advice on which way to go with jetting after these runs.

 

Your numbers look good!!
That's based on a 15% drive train loss yeah?

 

Dano, I'm guessing your bike runs either the 21119-1322 or 21119-1384 TCI units. I'd be surprised if it's running the 21119-1316 TCI, but I've been surprised before. Below are the ignition curves for those TCI units. You can show them to your Dyno guy so he has an idea of what's happening across the rev range. The TCI unit @Linkin referred to (Lixianda) is a relatively cheap aftermarket unit that (unfortunately) has the rev limiter removed and (fortunately) opens up the top end of the ignition curve; this doesn't make any more power (on the dyno), but you will notice the power deliver is smoother up high and the power curve doesn't drop away dramatically like on a normal dyno pull. The ZXR250C TCI units have a slightly better ignition curve to the ZXR250A TCI units.

 

Hey Dano, yes the 1384 is limited. The 1316 is from the malaysian model, but I don't think it is any different to the other non-limited TCI units for the C model. I too believe that not having a rev-limited TCI on a ZXR250 is a bad idea. The Honda CBR seems to cope with being over-revved, but the ZXR does not like it at all. I think @Murdo runs a Lixianda unit on his CBR and he might have zinged it past the redline at least once and it survived. A couple of period 6 guys reckon the CBR can go 22,000rpm without permanent damage!

 

[QUOTE=" I think @Murdo runs a Lixianda unit on his CBR and he might have zinged it past the redline at least once and it survived. [/QUOTE]
I will admit to seeing 21,000 on the tacho once when trying to beat an R1 at the drags with no ill effects to the engine.

 

Must be satisfying to get dyno runs with those figures on something that you rebuilt yourself - kudos!
Also that 1.1 HP is nothing to be sneezed, it's 2.6%.

 

I think your 10,000rpm weak spot is a consequence of having a motor that revs to 16-18,000. There'll be resonance happening up top to make horsepower, but at 10k it ain't helping. My Yamaha is sweet below 10,000 and goes well above 10,200. In anything other than 1st gear on a flat it will not accelerate through that gap.
As everyone seems to agree, it's richer than it needs to be. However, my son's R6 runs at .72lambda or about 10.5:1 and the pipe is spotlessly clean plus it makes good power. I suspect that just like 2-strokes, which I know about, that the fuel is to help the motor survive a good thrashing. My desired lambda is 0.88 or about 12.9:1 at WOT without boost in my Yamaha and 0.78lambda or 11.5:1 with boost. 12:1 should be safe as houses and give you a few horsepower. Buying a lambda meter is a good investment. Put it on for tuning then take it off once done

 

Emulsion tubes are the same across all 4 carbs.