Pipercross MPX1004 dual pod filters.

[tabby59]

Hi folks. I'm just checking in to see if any of you have used these filters on your A/O motors and what are your thoughts. I'd especially be interested in how they compare to the K&N RU-2922. The K&Ns push against the frame of my Slabby enough to push them down some, while the MPX 1004 looks to be tapered a bit and might fit in there better. Dyno comparisons would be greatly appreciated if you have them. If the Pipers flow as well, great, I might give them a try. If not, well, I'll be less inclined.

[Nelson]

Hi Tabby

Can't do you a direct comparison bhp, I swapped filters at the same time I changed from 40mm to 38mm carbs.

here's the fit / look comparison.

 

 

 

 

 

 

[Nelson]

Here's the K & N s on some 40mm carbs

 

 

 

 

 

 

[Nelson]

To make them fit & look better I notched them.

The K & N filters fitted to 40mm M carbs on a tuned Slabby engine made 131 bhp on a rolling road.

The Pipercross filters fitted to 38mm 750 M powerjet carbs, same motor, make 126 bhp on the same rolling road.

Had it sorted November, just in time for the winter. Nice !

Dyno-jet stage 3 in the 38s.

 

 

 

 

 

 

 

 

[tabby59]

Wow,,,,,, you weren't messing around notching the K&Ns. Something to consider. I have RS38s, which both the Piper and the K&N don't really fit. I had to make aluminum sleeves that I shrunk fit onto the RSs,,,,, with some additional "adapting" shall we say. The Pipers definitely have more room. You are right about a direct comparison. Too bad you didn't try the Pipers on the 40s. My engine is a hot rodded 750/907. It made 142 rwhp without filters, 138 with individual K&N pods. My engine builder said to run the duals to get the 4 hp back. If you are curious, you can see my dyno sheets in one of my Facebook albums. Just look up Tab Burgess

[Nelson]

Yo Tabby,

Sorted through the paperwork, the first one is with K & Ns on the 40mm carbs

 

 

This is the Pipers on the 38s

 

 

Thing is, when I had the 40s dyno-ed, I was proper on my knees. So Pete got it best as, with minimum expense. It had had a Dynojet kit some time in the 18th Century & the needles were fecked. I couldn't afford new.

It ran 'ok' for some time but then went right off.

Everybody, who ever everybody is, says that the 38s are best & the 40s are too big.

Looking at the results it would great to throw the credit card at the 40s & see what happens.

Unfortunately my credit card in the critical ward & with Christmas, it will be on life support.

However, 

[tabby59]

Thanks nelson! I'm not used to your dyno sheets. I was looking at the bottom graph. AFRs? The K&Ns on the 40s looked like it went lean up top. The Pipers went rich? I can't read the graphs very well. I don't know if you pay as big a "penalty" for being too big with CV carbs. I would imagine that if an engine couldn't quite pull enough air through one, the vacuum slide just wouldn't retract all the way?? Might it still maintain a constant velocity? So much I don't know about fuel mixers. 

[Nelson]

It's all science & black magic to me.

It seems like a different byke when I got it back.

It rides REAL good. 

As best I can tell on 5 degree C roads,

With the 40s it ran ok but here's a shot of one of the needles.

 

 

Massive wear grooves. 

It still made 130 brake & seemed ok-ish.

How good would they be with the same work I've just put in the 38s.

The 1100 M had the 40s & made 140 I think.

No body had a problem with them then,