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Removal of pre-catalyst in stock 1050 header?

16442 Views 95 Replies 18 Participants Last post by  Willgaut
Inside the header of the 1050cc Triples is a small length of perforated tubing coated with a catalyst material - located just behind the collector. Has anyone remove this? What was gained in performance - if anything?

I have removed it from my header, ported the primary entries, and removed a good amount of weld and slag inside the collector. I have also ceramic coated the header and wrapped the primaries with insulation. I will report any results, but wanted to know if anyone else has done something like this.

The photo is not mine, but shows the part I am refering to.
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Last person I'd heard of who tried removing the pre-cats got maybe a half horsepower bump up. I'd definitely like to hear your results in case you manage something extra that gives more power.
Initial impressions are interesting - I have started the engine and let it idle to check everything out. It DOES sound a bit different... A touch deeper with less metalic resonance. This is with the TOR exhaust that I have become used to.

I need to put on the body panels (other than just the tank) today, before I test ride it. The panels have been out for paint. And I will change out the TOR exhaust for the new Trident half system I just bought. As a result, I will not have any direct comparisons - LOTS of changes since I took it apart for paint and mods/clean up.

On a side note, the Trident half system uses a larger mid pipe and silencer/can inside diameter. On my bench, they flow considerably more air. I have yet to find out just how much is overkill for intake and exhaust flow.
After a few longer rides, I definately like the combination of both the precatalyst and SAI removed - no poping at all now. I've done quite a few modifications at the same time, so I can't point at one mod or another, but the bike is definately more responsive.

Resonance in the exhaust has changed by a few hundred rpm. My bet this is due to flow through the header and the increased exhaust temps through the exhaust system with the ceramic coating and header wrap.

The "gurgling" at part throttle with the modified Tuneboy 20103 map is a bit more noticeable though, but I have an idea about the cause. I can't seem to tune it out with fuel or timing, so it's more than likely the venturis; just like on the 955i Daytonas. Work here may do wonders.
I spent Friday removing the precat from the header on HiVel's bike. We also cleaned up the ports and inside welding slag.

We coated the header and exhaust system on his bike as well.
He swears he has noticed a performance increase, and likes the slightly deeper tone to the exhaust. The black exhaust on his white speed triple looks great!

He is spending the day riding. Maybe I can get him to post his impressions here soon.
Yep, we did it. Sawing, chiseling, cutting, grinding, welding, ceramic coating and cooking in the big oven! DONE! A bit of work ? -yes. Worth it ? -yes! My bike has a Trident half system which needed some grinding and cleaning inside on the Oxy sensor boss. That was done as well. Now we have a more rorty, deeper tone coming out through the carbon cans plus the bike feels like it has picked up some HP all across the RPM range. It literally jumps on throttle twisting, is very crisp and I like it! We also put the Tuneboy tune for this set up in it from Wayne @ Tuneboy-wow! Good stuff. More tuning to come. I have the BMC filter and Khulka's SAI block off plates (nice stuff also) and am going to try some other simple mods soon. This is some pretty simple stuff that really livens up this bike. Thanks to Devious for all his help and guidance.
Want to get it on the dyno very soon. These bikes come from the factory mass market detuned and have some real good potential with fairly easy mods.
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I envy you Hivel for living so close to Devi!
I'm always glad to help another enthusiast. I'm just glad you are happy with the results. These bikes make it almost too easy to get more power.
These mods have made my bike so nice to ride-flat torque curve is the secret plus great throttle response and such a sound. I love it. Rode around this afternoon and could not get enough of it. Its almost like you do not even need the gearbox it pulls so hard from 2000 rpm on up. Good stuff. More to come.Thanks again Dev.
All it costs is time - glad to help. It makes my day.

I was actually surprized by the gain in low end torque by removing the precat and coating the exhaust on my bike. It is good to back up my findings with your results. This just goes to show how well the two mods work together. AND how much the stock bike is congested.

Next we need to get the cold air kit on it. ;D
I just removed the pre thing. Boy that tube is tiny! The ID is 32mm which makes it much smaller than the header primaries. The size is the same as the link pipe which has two of them. I would be very surprised if it does not choke. I believe it has more to do with noise than catalyst. The riding season is pretty much wrap here so I cannot test the performance.
Excellent work guys!
Now you see WHY I removed it from my header and from HiVel's.
If the pre silencer is in place and someone says the stock link pipe is restrictive, I just have to wonder. The link pipe has twice the area of the stock collector. Plus the gas in collector has more velocity and drag because it runs hotter. The design might not be the best possible but I don´t think the link pipe restricts power that much. This pre thing migh be one of the reasons why all after collector mods make more or less the same power. That means the restriction is not in the link pipe and cans. With the 32mm tube in the collector the choke is propably there. Someone should dyno the before and after case.
The restriction is definately in the precat rather than the mid-pipe. But there is more to it than that.

Why do the Zard and Arrow full systems NOT make more power than a stock header (with precat) and TOR exhaust? With a good tune, I have yet to see an aftermarket full system beat the power of a stock header. It doesn't mean it is not possible, just that I have yet to see dyno results for a full system that do so.

I have dyno'd before and after, but I changed several things when I removed the precat. I do not feel that there is much (if any) difference in power between the TORS and the Trident half system - until you are making over 130 hp.
The same thing has crossed my mind also. Zard & Co do not make tremendous power compared to cans only. That makes me think there is not much power available in the exhaust no matter what brand or design it is. Maybe the stock one is not that bad after all. The Zard is not very much different from the stock after all. Maybe the cams are so mild the exhaust tuning has not much effect. With the engine in higher state of tune may change things. On the other hand the pre cat is so tiny the downstream would not make much difference because it flows more in any case.
Mild cam timing in an engine makes the engine notice other changes less. The reduced valve duration and overlap means the exhaust can scavange the cylinder less. So, designing the header to work over a wide rpm range effectively should be the priority - not simply targeting high rpm flow.

This is why modifying the stock header through precat removal, ceramic coating/wrapping, and interior clean up will give the bigest bang for the buck. A well designed aftermarket or custom header MIGHT make 3-4% more power with the stock cams, so the cost to result ratio is MUCH higher.

I still want to build a better header this winter - I HAVE to know what it gains over what I have already done to the stock header.
Is there a way to remove the pre-cat without drilling holes in the collector? I don't have any welding equipment to fill in the holes.
I'm not going to say it is impossible, but it would be tough. If you look at the location of the front welded pins (forward of the rear header mount), you see that they are pretty far inside the collector.

IF you used an air chisel, you might be able to cut the pre-cat into a few pieces and remove it a bit at a time.

Premier - Isn't there a welding shop nearby that can do the welding? At most it is two welds that are about 15-17mm in diameter. A good Harley Davidson or hot rod shop should have the equipment to do the work. I think that is what TightTL had done.
Devious is right. At his suggestion I went to a local HD dealership where they have one kick ass machine shop and the machinists and fabricators to use the stuff. They charge $65 an hour for welding work and it took an hour to remove the precat, weld up the holes, and grind the welds smooth. While I was there I also had them port the header...that was another $35. I thought the price was reasonable and the work was done once and done right.
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