Whoopsy water + some air box and intake mods

[stopintime]

Cutting a cyinnder every speed bump... hmmm. It had rained a whole week, so I checked a few connectors. No effect. Had some time, so cleaned my air filter...

 

[koko64]

Water injection 

[koko64]

Seriously though, I've never liked how close the air filter is to the top of the velocity stacks on some models.
It led me to relocate the filter to the top of the airbox lid to maximise the space or volume available for the stacks to draw on during each intake event.
The carb models were particularly bad. Made some gains there on the dyno. The tank shape had to allow enough space between the filter and the underside of the tank for it to work though.

What is the distance between the top of the stacks and the filter?

[stopintime]

I don't know the height measurements, but I have doubts about this being a significant improvement area. Because the lid is open and the filter very unrestrictive. What does make a huge difference is work done to the intake. My 839cc well built engine made 99 bhp (Kämna numbers which were "calculated" the same way Ducati always did)(about 10% bullshit), then detuned to let the engines survive more than a year. Now about 86 honest rear wheel bhp. That's great numbers. Biggelaar offers to do more - besides my already nicely done port & polish in the heads he wants to modify the rest of the intake and with a serious face claim further 10bhp. That, of course, will make me kill my engines in a much shorter time, so I have declined since 2020. Not sure how much longer I can resist... However, I'll ask if the air filter box/stacks can be modified to work better. If so, I'm going to be close to 100 rear wheel bhp.

[koko64]

I wish my SC800 made 86hp.
My high comp, ported, M900 made 86hp/68 ft/lbs torque. The airbox mods gave me 4-5 of that.

I've thought about an 1100 crank and 90mm bore in Scrambler cases to give 910cc. Then better cams and twin throttle bodies.

Or I could buy back my M1100 Evo.

[MonsterHPD]

I wish my SC800 made 86hp.
My high comp, ported, M900 made 86hp/68 ft/lbs torque. The airbox mods gave me 4-5 of that.

Hi,
would be interesting to know exactly what your airbox mods were.

A member on the german ducati.1 forum is an experienced engine developer at one of the big german car / engineering companies. He has made pressure measurements inside the inlet system, and has concluded that the combination of uneven inlet suction events and an unsufficient airbox volume results in the HOR cylinder having less air than the VER cylinder, resulting in a power deficiency of about the magnitude you mention. Acc to him, it´s also the reason the VER cylinder´s running hotter than the HOR; it´s simply working harder.

I don´t have any actual measurement records or similiar to verify this, but I do trust this person to know what he´s talking about. I will certainly at least open up the airbox lid on my ST2-motored SSie track bike for next year.   

[koko64]

I'll email you some pics including the dyno chart. The photo host sites don't like me any more.

[MonsterHPD]

Hi,
I now have the pics, and relevant explanations. I´ll post them here, if it´s OK with you both.

[stopintime]

Please do 

[koko64]

No worries.

[MonsterHPD]

OK, let´s try this. I´m still not sure about all the details of the dyno runs, so please clarify as needed. This post is entirely Tony´s pics and info, I just play the messenger here, the messenger does not always get all details correct.

Starting point: 73hp for stock bike.

First dyno run is open stock airbox and stock velocity stack rubbers, possily verus stock airbox and short inlet rubbers (?).

Dyno2 by torbjörn bergström, on Flickr

Second dyno is modified open airbox and shorter, ported velocity stack rubbers as I described. Stacks are 17-18mm shorter and air filter is lifted up to the top of the airbox lid like in the pictures. This increases the gap between rubber trumpet stacks and filter to 80mm which let's the whole airbox volume be used. The stock gap gap is only 30mm and this causes bad turbulence and negative effect resonance. The stock design doesn't effectly use all the airbox. You can see two round dirt marks above the stacks on a stock filter. The filter is too close!
As noted on the graph: Open stock airbox vs modified open airbox as described above. Bike has high comp, ported heads and FCR41s.

Dyno1 by torbjörn bergström, on Flickr

Stock airbox:

Airbox OEM by torbjörn bergström, on Flickr

"Project"  components:

Airbox mod components by torbjörn bergström, on Flickr

Final assy:

Airbox mod assy by torbjörn bergström, on Flickr

I have to wonder, how did all that fit under the tank???

I hope I got it all correct, if not, please inform / add / correctas needed.

Kind regards,
Torbjörn.   

[koko64]

That's pretty close.
So the bike was a ported, hi comp M900 with FCR41, and Termi pipes.

The dyno charts show the before and after between an open airbox that's otherwise stock and an airbox with shortened inlet rubber stacks and the filter placed on top of the airbox lid. This increases the space between the filter and the stacks from 30mm to 80 + mm. It let's the ports draw on the whole airbox volume instead of only sucking through the filter above the stacks. Evidenced by two dirty circles on the filter in stock airboxes.

No other changes.
So stock bike 73hp
Modified bike with airbox changes
81 to 86hp.

Same dyno and operator, same software.

The shape of the torque curve is the evidence as it changed character. You can see it may be improved in the mid range with a jet change.

I don't know if it would work on a stock carbed M900. Maybe the modified bikes ported heads liked the extra available airbox volume?

The concept is to increase sub airfilter volume available to the velocity stack rubbers.

The pic with the M900ie airbox shows the change in available sub airfilter volume and how limited the carby airbox is. I would like to use a slightly smaller airfilter in the future for a better fit, but I used the customer's existing K&N filter in each case to save money.

It fits because the filter is relocated to the roof of the airbox lid
and the little snorkels are gone. It can be tight at the front under the steering lock. I have made a few on modified carby bikes,
three 900s and a 750, but not on a 900ie (yet).
One thing I forgot to explain, a goal was to get the carb 900 airbox volume below the filter (sub filter volume) closer in volume to the M900ie airbox sub filter. Looking at the two airboxes, I came close to achieving that.

Thanks.

[koko64]

Sent some more pics I found.