290cc Athena big bore kit hits 31 hp!

[Tazsike]

Luckily we have such great options to choose from in these times.

[Thumpthing Old]

Well, my ZX10 will read 105 in 1st gear when I hit the rev limiter, so there is a we bit of difference. However, I'm having a great time riding the WRX and it is FAR more pleasant around town.

So if you can got 105 in first, what's the point of those other 5 gears?

[Tazsike]

So if you can got 105 in first, what's the point of those other 5 gears?

I'm not sure!!!

I've had a few really fast bikes and been to a fair amount of trackdays, and I don't think the modern literbikes, Busa, ZX-14, etc have all that much practical purpuse. However, it is profoundly fun for a while. The problem I'm running into, and part of the reason for the WRX, is that the police in my area are now arresting people for things that I used to do regularly (not the silly child stuff in traffic, just the extreme speeding and wheelies when not in traffic). And, I don't have the time for more than a handful of trackdays per year.

[r1usn]

This is a serious question, not a smarta$$ question. Why go with either bigbore kit when you can get 31+ rwhp with a pipe, airbox mod, PCIII, and dyno tune. Especially given that you will do most/all of these either way. I'm sure there is a little extra torque involved with the bigbore kit, but realistically how much time would be spent in the rpm range in which the extra torque would be of any use?

So much misinformation on this post. No point in arguing about it, but a big bore with the same mods as a stock bore is going to give you more hp and tq throughout the entire rev range. Simple as that. The only time this wouldn't be true on a fuel injected bike, would be if it wasn't tuned and the a/f ratios were way off.

[Tazsike]

So much misinformation on this post. No point in arguing about it, but a big bore with the same mods as a stock bore is going to give you more hp and tq throughout the entire rev range. Simple as that. The only time this wouldn't be true on a fuel injected bike, would be if it wasn't tuned and the a/f ratios were way off.

I believe that most people here understand that it will provide more HP and Torque over a portion of the rpm range. However, for example, if my bike without a bigbore kit is providing 31ish HP from about 8500 to rev limiter and that matches the big bore, and I ride it in that range when I'm having fun, why would I spent the extra $1000-$1500? Again, I understand the extra power and torque at 4000-8500, but the numbers aren't such that it changes the bike from a slow bike to a fast bike in that range, but just makes it a bit better (maybe perfect for some and well worth the investment). If you would like (and my son is home to do it for me later since I haven't figure the scanner to jpeg thing), I can post my dyno graph for comparison purposes.

[Tazsike]

Out of curiousity, I compared the numbers at several points (my son isn't around to make the jpeg for me). It was tuned on a Dynojet. Obviously numbers vary between dyno's. However, he said that the prior two WRX's had put down just under and just over 32rwhp (but, he said mine tuned out/ran better relative to AF...).

Mine at 5500 makes 15 rwhp

at 8500 makes 30 rwhp

at 9000 makes 31.17 rwhp

at 9500 makes 30 rwhp

and holds 30+ rwhp until the rev limiter

ranges from 16 fp of torque to 18.68 between 5500 and 9200

The dyno of the big bore kit bike (I was guesstimating looking at the picture)

at 5500 makes 20 rwhp

at 8200 makes 30 rwhp

at 9000 makes 31+ rwhp (couldn't see the exact number)

at 9500 makes 29 rwhp

and hold 28 ish rwhp until just before the rev limiter and then drops

ranges from 17-19 fp of torque between 5500 and 9200.

So, there is one point of clear advantage, and a slight disadvantage at the top. This is meant for discussion not argument. I'm here because I love talking about motorcycles and not here to argue. I just find this interesting.

[bmdtech]

I am curious as to if Thumpthing had any porting done on the engine during this process?

It looks like the big bore does help the bottom end tremendously, which is about the only point I feel much of a weekness on this bike. I ride with quite a few guys on big ktm 530's and the biggest slowdown I see is going around tight corners and trying to pull out fast if I am not in the "right gear" its slow going. The bottom end improvment would help from this kit.

[Thumpthing Old]

I am curious as to if Thumpthing had any porting done on the engine during this process?

It looks like the big bore does help the bottom end tremendously, which is about the only point I feel much of a weekness on this bike. I ride with quite a few guys on big ktm 530's and the biggest slowdown I see is going around tight corners and trying to pull out fast if I am not in the "right gear" its slow going. The bottom end improvment would help from this kit.

Nope, my engine has no porting at all. Just the Athena 290 kit, PCIII with custom map, GYTR pipe, stock headpipe, K&N and airbox flapper held open. Some porting would help I'm sure, but I just didn't want to spend the time and money on it.

Years ago I ported four cylinder roadrace engines----it was pretty fun to do if you have the right equipment and guidance from somebody who knows that they're doing. But one slip can really screw things up!

[Thumpthing Old]

Out of curiousity, I compared the numbers at several points (my son isn't around to make the jpeg for me). It was tuned on a Dynojet. Obviously numbers vary between dyno's. However, he said that the prior two WRX's had put down just under and just over 32rwhp (but, he said mine tuned out/ran better relative to AF...).

Mine at 5500 makes 15 rwhp

at 8500 makes 30 rwhp

at 9000 makes 31.17 rwhp

at 9500 makes 30 rwhp

and holds 30+ rwhp until the rev limiter

ranges from 16 fp of torque to 18.68 between 5500 and 9200

The dyno of the big bore kit bike (I was guesstimating looking at the picture)

at 5500 makes 20 rwhp

at 8200 makes 30 rwhp

at 9000 makes 31+ rwhp (couldn't see the exact number)

at 9500 makes 29 rwhp

and hold 28 ish rwhp until just before the rev limiter and then drops

ranges from 17-19 fp of torque between 5500 and 9200.

So, there is one point of clear advantage, and a slight disadvantage at the top. This is meant for discussion not argument. I'm here because I love talking about motorcycles and not here to argue. I just find this interesting.

Same here----this is just discussion, not religion.

I expect that a large part of the ambiguous dyno numbers we see is due to the variables that actually don't relate to the big bore kit. There is variation in individual bikes, in the dynos, in the dyno operator, the type of tire on the back of the bike (which I assume could change the amount of slip), the weather (though the dyno is supposed to compensate for this). Maybe other factors like chain tension, break-in miles or what gear the run is made in.

The reason I think these variables add up to something significant is that I've seen peak horsepower figures for completely stock WR250R/Xs listed on-line as anywhere from 24 to 27 horsepower. That strikes me as a really big swing----more than you you get from just the variation between two bikes coming down the assembly line.

That kind of variation makes me inclined to not trust figures from different dynos at different times----at least not for comparison.

I tend to agree with R1USN. If you take a WR with a Dyno tuned PCIII, pipe, modded airbox and K&n and run it on a dyno, you'll get X horsepower. Now if you take that same bike and add 40cc of displacement (16%), give it a custom PCIII map and run it again, it just about HAS to make more power everywhere, including on top. Getting X+16% seems reasonable, give or take based on whether the engine is bumping into some kind of internal airflow restriction or something like that. That's how I see the Big Bore kit running on a hypothetical perfect dyno. In the real world, hard to say.

[r1usn]

Out of curiousity, I compared the numbers at several points (my son isn't around to make the jpeg for me). It was tuned on a Dynojet. Obviously numbers vary between dyno's. However, he said that the prior two WRX's had put down just under and just over 32rwhp (but, he said mine tuned out/ran better relative to AF...).

Mine at 5500 makes 15 rwhp

at 8500 makes 30 rwhp

at 9000 makes 31.17 rwhp

at 9500 makes 30 rwhp

and holds 30+ rwhp until the rev limiter

ranges from 16 fp of torque to 18.68 between 5500 and 9200

The dyno of the big bore kit bike (I was guesstimating looking at the picture)

at 5500 makes 20 rwhp

at 8200 makes 30 rwhp

at 9000 makes 31+ rwhp (couldn't see the exact number)

at 9500 makes 29 rwhp

and hold 28 ish rwhp until just before the rev limiter and then drops

ranges from 17-19 fp of torque between 5500 and 9200.

So, there is one point of clear advantage, and a slight disadvantage at the top. This is meant for discussion not argument. I'm here because I love talking about motorcycles and not here to argue. I just find this interesting.

No i am not here to argue either. I just don't want some newbie to read this post and think a 290cc wrx is going to have the same power as a 250cc wrx. The only way to tell the true power difference between the two would be to dyno them on the same dyno within minutes of each other. If this is ever accomplished, i bet the 290cc bike would consistantly have 2-4 more hp than the 250cc bike. If this wasn't the case what's the point of putting a big bore kit on anything?

[Tazsike]

No i am not here to argue either. I just don't want some newbie to read this post and think a 290cc wrx is going to have the same power as a 250cc wrx. The only way to tell the true power difference between the two would be to dyno them on the same dyno within minutes of each other. If this is ever accomplished, i bet the 290cc bike would consistantly have 2-4 more hp than the 250cc bike. If this wasn't the case what's the point of putting a big bore kit on anything?

I have seen and used big bore kits in both motorcycles and cars for a long, long time. And, usually the result is very consistent, and similar to what you are discussing. However, I have seen three dyno graphs for bikes modified like mine and two modified with big bore kits, and in all cases the data has been similar to above (that isn't a lot of data, but the data has been consistent). There has been a notable advantage down low, and little or no advantage up top. The most RWHP I have seen or heard about out of a big bore kit (on our bike) has been in the high 33 range and I have seen bikes in the high 32 without it (and, again the advantage has mostly been in an area I really don't care much about, but might be very important to others, therefore making this the perfect mod). I think that in our case there are two factors leading to "different" results. First, we are talking about a small engine that is still a small engine after the mod (even though the percentage difference is pretty good). Second, the fact that it is a large percentage difference changes the dynamics of where the gains will occur and creates the drop near the top. Just some thoughts, and I am enjoying the discussion.

[r1usn]

You are probably right about the top end. I don't know enough about the wrx engine but if i had to guess, i would say either the head does not flow enough gases (Which could be cams or the head itself), or the diameter of the aftermarket pipe is too small to flow enough to support the extra 40cc. This would limit your top end performance.

[Tazsike]

You are probably right about the top end. I don't know enough about the wrx engine but if i had to guess, i would say either the head does not flow enough gases (Which could be cams or the head itself), or the diameter of the aftermarket pipe is too small to flow enough to support the extra 40cc. This would limit your top end performance.

Funny thing today when I stopped by the shop during my ride. They said that they did the same mods to yet another WRX (except they kept the airbox door) and this one wouldn't break into the 28 range. So, they have modded and dynoed 6 (I believe), with a range of results from high 27's to low 32's (on the same dyno in similar weather). I do believe this bike has its biggest limitation on the air intake side, then followed by the header. However, I didn't do the header and I'm pretty darn happy with the results.

Back to the big bore kit, though. Is the Yamaha accessory kit the exact same kit as ThumpingOld used?

[Thumpthing Old]

Funny thing today when I stopped by the shop during my ride. They said that they did the same mods to yet another WRX (except they kept the airbox door) and this one wouldn't break into the 28 range. So, they have modded and dynoed 6 (I believe), with a range of results from high 27's to low 32's (on the same dyno in similar weather). I do believe this bike has its biggest limitation on the air intake side, then followed by the header. However, I didn't do the header and I'm pretty darn happy with the results.

Back to the big bore kit, though. Is the Yamaha accessory kit the exact same kit as ThumpingOld used?

That's pretty interesting about the range of dyno figures. The airbox opening is pretty small, so maybe it's a bottleneck even with the flapper mod. I tried removing the entire top of my airbox, but it was so loud and vibrated the seat so much, I decided to glue it back on. Did you remove the side door on yours?

As for the Athena kit, it appears to be the exact same item that Yamaha is selling. Yamaha is referring to it as an "Athena 290 kit", and it has all the same items included. So I'm assuming there are no differences in the version sold through Yamaha or through other channels.

[Tazsike]

That's pretty interesting about the range of dyno figures. The airbox opening is pretty small, so maybe it's a bottleneck even with the flapper mod. I tried removing the entire top of my airbox, but it was so loud and vibrated the seat so much, I decided to glue it back on. Did you remove the side door on yours?

As for the Athena kit, it appears to be the exact same item that Yamaha is selling. Yamaha is referring to it as an "Athena 290 kit", and it has all the same items included. So I'm assuming there are no differences in the version sold through Yamaha or through other channels.

Yes, the entire side door is off on my bike. It made a huge difference in the tuning, and yes it is rather loud. At the track day I asked a few of the guys I know well if it is loud or obnoxious, and everyone said loud without hesitation. Also, I have very little concern regarding water (even though it rains up here in Seattle). I have had several cars with far more exposed systems and never had a problem.

Interesting that Yamaha is selling the Athena unit. They must have a lot of faith in it.

[Thumpthing Old]

Interesting that Yamaha is selling the Athena unit. They must have a lot of faith in it.

That's what I'm hoping! I'm committed now----to put it mildly!

One interesting thing about the fuel controller that comes with the Athena kit is that it lowers the rev-limiter from 11,500 rpm, down to 11,000. (I didn't install the kit fuel controller; I used my PCIII with a custom dyno tune.) That makes me think that the kit is fairly well thought out, and that given the added power and piston weight, they wanted a little less maximum rpm.

Mine still revs to 11,500, but I promise not to use that last 500 rpm (much!).

[routerdotexe]

i want to see results of a derestriced airbox, and an after market pipe with the exup on it.

[Travis_D-37]

How about this? We just bought a dyno once I get it up, running and some training I do a dyno day at the shop open to anyone that wants to come down. Hopefully Ministry and Thumpthing old can come down and do back to back runs. That way you will have an apple to apple comparison.

[Thumpthing Old]

I think you'd have quite a few takers so something like that----the place would probably be WR central for the day.

[Ministry]

How about this? We just bought a dyno once I get it up, running and some training I do a dyno day at the shop open to anyone that wants to come down. Hopefully Ministry and Thumpthing old can come down and do back to back runs. That way you will have an apple to apple comparison.

Grats on getting the dyno! WR250R/X dyno day sounds awsome. I want the highest hp title, count me in for sure.